Before we present the typical symptoms of asthma, we should dispel some common myths about this condition. This is best achieved by conducting a short true or false quiz.

1. T or F Asthma is “all in the mind.”
2. T or F You will “grow out of it.”
3. T or F Asthma can be cured, so it is not serious and nobody dies from it.
4. T or F You are likely to develop asthma if someone in your family has it.
5. T or F You can “catch” asthma from someone else who has it.
6. T or F Moving to a different location, such as the desert, can cure asthma.
7. T or F People with asthma should not exercise.
8. T or F Asthma does not require medical treatment.
9. T or F Medications used to treat asthma are habit-forming.
10. T or F Someone with asthma can provoke episodes anytime they want in order to get attention.

Here are the answers:

1. F – Asthma is not a psychological condition. However, emotional triggers can cause flare-ups.
2. F – You cannot outgrow asthma. In about 50% of children with asthma, the condition may become inactive in the teenage years. The symptoms, however, may reoccur at any time in adulthood.
3. F – There is no cure for asthma, but the disease can be controlled in most patients with good medical care. The condition should be taken seriously, since uncontrolled asthma may result in emergency hospitalization and possible death.
4. T – You have a 6% chance of having asthma if neither parent has the condition; a 30% chance if one parent has it; and a 70% chance if both parents have it.
5. F – Asthma is not contagious.
6. F – A new environment may temporarily improve asthma symptoms, but it will not cure asthma. After a few years in the new location, many people become sensitized to the new environment and the asthma symptoms return with the same or even greater intensity than before.
7. F – Swimming is an optimal exercise for those with asthma. On the other hand, exercising in dry, cold air may be a trigger for asthma in some people.
8. F – Asthma is best controlled by having an asthma management plan designed by your doctor that includes the medications used for quick relief and those used as controllers.
9. F – Asthma medications are not addictive.
10. F – Asthma attacks cannot be faked.

What is asthma?

Asthma is a chronic inflammation of the bronchial tubes (airways) that causes swelling and narrowing (constriction) of the airways. The result is difficulty breathing. The bronchial narrowing is usually either totally or at least partially reversible with treatments.

Bronchial tubes that are chronically inflamed may become overly sensitive to allergens (specific triggers) or irritants (nonspecific triggers). The airways may become “twitchy” and remain in a state of heightened sensitivity. This is called “Bronchial Hyperreactivity” (BHR). It is likely that there is a spectrum of bronchial hyperreactivity in all individuals. However, it is clear that asthmatics and allergic individuals (without apparent asthma) have a greater degree of bronchial hyperreactivity than non-asthmatic and nonallergic people. In sensitive individuals, the bronchial tubes are more likely to swell and constrict when exposed to triggers such as allergens, tobacco smoke, or exercise. Amongst asthmatics, some may have mild BHR and no symptoms while others may have severe BHR and chronic symptoms.

Allergy Assist

Asthma affects people differently. Each individual is unique in their degree of reactivity to environmental triggers. This naturally influences the type and dose of medication prescribed, which may vary from one individual to another.

From the past to the present

Physicians in ancient Greece used the word “asthma” to describe breathlessness or gasping. They believed that asthma was derived from internal imbalances, which could be restored by healthy diet, plant and animal remedies, or lifestyle changes.

Allergy Jargon

Asthma is derived from the Greek word “Panos,” meaning panting.

Chinese healers understood that “xiao-chiran,” or “wheezy breathing,” was a sign of imbalance in the life force they called “Qi.” They restored “Qi” by means of herbs, acupuncture, massage, diet, and exercise.

The Hindu philosophers connected the soul and breath as part of the mind, body, and spirit connection. Yoga uses control of breathing to enhance meditation. Indian physicians taught these breathing techniques to help manage asthma.

Allergy Fact

Maimonides was a renowned 12th-century rabbi and physician who practiced in the court of the sultan of Egypt. He recommended to one of the Royal Princes with asthma that he eat, drink, and sleep less. He also advised that he engage in less sexual activity, avoid the polluted city environment, and eat a specific remedy-chicken soup.

The balance of the “four humors,” which was derived from the Greco-Roman times, influenced European medicine until the middle of the 18th century. In a healthy person, the four humors, or bodily fluids-blood, black bile, yellow bile, and phlegm-were in balance. An excess of one of these humors determined what kinds of disorders were present. Asthmatics who were noted for their coughing, congestion, and excess mucus (phlegm) production were therefore regarded as “phlegmatic.”

By the 1800s, aided by the invention of the stethoscope, physicians began to recognize asthma as a specific disease. However, patients still requested the traditional treatments of the day, such as bloodletting, herbs, and smoking tobacco. These methods were used for a variety of conditions, including asthma. Of the many remedies that were advertised for asthma throughout the 19th century, none were particularly helpful.

Allergy Fact

As early as 1892, the famous Canadian-American physician Sir William Osler suggested that inflammation played an important role in asthma.

Bronchial dilators first appeared in the 1930s and were improved in the 1950s. Shortly thereafter, corticosteroid drugs that treated inflammation appeared and have become the mainstay of therapy used today.

The scope of the problem

Asthma is now the most common chronic illness in children, affecting one in every 15. In North America, 5% of adults are also afflicted. In all, there are about 1 million Canadians and 15 million Americans who suffer from this disease.

The number of new cases and the yearly rate of hospitalization for asthma have increased about 30% over the past 20 years. Even with advances in treatment, asthma deaths among young people have more that doubled.

Allergy Fact

There are about 5,000 deaths annually from asthma in the U.S. and about 500 deaths per year in Canada.

Normal bronchial tubes

Before we can appreciate how asthma affects the bronchial airways, we should first take a quick look at the structure and function of normal bronchial tubes.

The air we breathe in through our nose and mouth passes through the vocal cords (larynx) and into the windpipe (trachea). The air then enters the lungs by way of two large air passages (bronchi), one for each lung. The bronchi divide within each lung into smaller and smaller air tubes (bronchioles), just like branches of an inverted tree. Inhaled air is brought through these airways to the millions of tiny air sacs (alveoli) that are contained in the lungs. Oxygen (O2) passes from the air sacs into the bloodstream through numerous tiny blood vessels called capillaries. Similarly, the body’s waste product, carbon dioxide (CO2), is returned to the air sacs and then eliminated upon each exhalation.

Normal bronchial tubes allow rapid passage of air in and out of the lungs to ensure that the levels of O2 and CO2 remain constant in the blood stream. The outer walls of the bronchial tubes are surrounded by smooth muscles that contract and relax automatically with each breath. This allows the required amount of air to enter and exit the lungs to achieve this normal exchange of O2 and CO2. The contraction and relaxation of the bronchial smooth muscles are controlled by two different nervous systems that work in harmony to keep the airways open.

The inner lining of the bronchial tubes, called the bronchial mucosa, contains: (1) mucus glands that produce just enough mucus to properly lubricate the airways; and (2) a variety of so-called inflammatory cells, such as eosinophils, lymphocytes, and mast cells. These cells are designed to protect the bronchial mucosa from the microorganisms, allergens, and irritants we inhale, and which can cause the bronchial tissue to swell. Remember, however, that these inflammatory cells are also important players in the allergic reaction. Therefore, the presence of these cells in the bronchial tubes causes them to be a prime target for allergic inflammation.

how does asthma affect breathing?

Asthma causes a narrowing of the breathing airways, which interferes with the normal movement of air in and out of the lungs. Asthma involves only the bronchial tubes and does not affect the air sacs or the lung tissue. The narrowing that occurs in asthma is caused by three major factors: inflammation, bronchospasm, and hyperreactivity.

Inflammation

The first and most important factor causing narrowing of the bronchial tubes is inflammation. The bronchial tubes become red, irritated, and swollen. The inflammation occurs in response to an allergen or irritant and results from the action of chemical mediators (histamine, leukotrienes, and others). The inflamed tissues produce an excess amount of “sticky” mucus into the tubes. The mucus can clump together and form “plugs” that can clog the smaller airways. Specialized allergy and inflammation cells (eosinophils and white blood cells), which accumulate at the site, cause tissue damage. These damaged cells are shed into the airways, thereby contributing to the narrowing.

Bronchospasm

The muscles around the bronchial tubes tighten during an attack of asthma. This muscle constriction of the airways is called bronchospasm. Bronchospasm causes the airway to narrow further. Chemical mediators and nerves in the bronchial tubes cause the muscles to constrict.

Hyperreactivity (Hypersensitivity)

In patients with asthma, the chronically inflamed and constricted airways become highly sensitive, or reactive, to triggers such as allergens, irritants, and infections. Exposure to these triggers may result in progressively more inflammation and narrowing.

The combination of these three factors results in difficulty with breathing out, or exhaling. As a result, the air needs to be forcefully exhaled to overcome the narrowing, thereby causing the typical “wheezing” sound. People with asthma also frequently “cough” in an attempt to expel the thick mucus plugs. Reducing the flow of air may result in less oxygen passing into the bloodstream and if very severe, carbon dioxide may dangerously accumulate in the blood.

The importance of inflammation

Inflammation, or swelling, is a normal response of the body to injury or infection. The blood flow increases to the affected site and cells rush in and ward off the offending problem. The healing process has begun. Usually, when the healing is complete, the inflammation subsides. Sometimes, the healing process causes scarring. The central issue in asthma, however, is that the inflammation does not resolve completely on its own. In the short term, this results in recurrent “attacks” of asthma. In the long term, it may lead to permanent thickening of the bronchial walls, called airway “remodeling.” If this occurs, the narrowing of the bronchial tubes may become irreversible and poorly responsive to medications. Therefore, the goals of asthma treatment are: (1) in the short term, to control airway inflammation in order to reduce the reactivity of the airways; and (2) in the long term, to prevent airway remodeling.

Allergy Assist

The hallmark of managing asthma is the prevention and treatment of airway inflammation. It is also likely that control of the inflammation will prevent airway remodeling and thereby prevent permanent loss of lung function.

Various triggers in susceptible individuals result in airway inflammation. Prolonged inflammation induces a state of airway hyperreactivity, which might progress to airway remodeling unless treated effectively.

Which triggers cause an asthma attack?

Asthma symptoms may be activated or aggravated by many agents. Not all asthmatics react to the same triggers. Additionally, the effect that each trigger has on the lungs varies from one individual to another. In general, the severity of your asthma depends on how many agents activate your symptoms and how sensitive your lungs are to them. Most of these triggers can also worsen nasal or eye symptoms.

Triggers fall into two categories:

• Allergens (“specific”)
• Nonallergens – mostly irritants (nonspecific)

Once your bronchial tubes (nose and eyes) become inflamed from an allergic exposure, a re-exposure to the offending allergens will often activate symptoms. These “reactive” bronchial tubes might also respond to other triggers, such as exercise, infections, and other irritants. The following is a simple checklist.

Common Asthma Triggers:

Allergens

• “Seasonal” pollens
• Year-round dust mites, molds, pets, and insect parts
• Foods, such as fish, egg, peanuts, nuts, cow’s milk, and soy
• Additives, such as sulfites
• Work-related agents, such as latex

Allergy Fact

About 80% of children and 50% of adults with asthma also have allergies.

Irritants

• Respiratory infections, such as those caused by viral “colds,” bronchitis, and sinusitis
• Drugs, such as aspirin, other NSAIDs (nonsteroidal antiinflammatory drugs), and beta blockers (used to treat blood pressure and other heart conditions)
• Tobacco smoke
• Outdoor factors, such as smog, weather changes, and diesel fumes
• Indoor factors, such as paint, detergents, deodorants, chemicals, and perfumes
• Nighttime
• GERD (gastroesophageal reflux disorder)
• Exercise, especially under cold dry conditions
• Work-related factors, such as chemicals, dusts, gases, and metals
• Emotional factors, such as laughing, crying, yelling, and distress
• Hormonal factors, such as in premenstrual syndrome

The many faces of asthma – “Expected”

The many potential triggers of asthma largely explain the different ways in which asthma can present. In most cases, the disease starts in early childhood-age 2 to 6 years. In this age group, the cause of asthma is often linked to exposure to allergens, such as dust mites, tobacco smoke, and viral respiratory infections. In very young children, less than 2 years of age, asthma can be difficult to diagnose with certainty. Wheezing at this age often follows a viral infection and might disappear later, without ever leading to asthma. Asthma, however, can develop again in adulthood. Adult-onset asthma occurs more often in women, mostly middle-aged, and frequently follows a respiratory tract infection. The triggers in this group are usually nonallergic in nature.

Types: allergic (extrinsic) and nonallergic (intrinsic) asthma

Your doctor may refer to asthma as being “extrinsic” or “intrinsic.” A better understanding of the nature of asthma can help explain the differences between them. Extrinsic, or allergic asthma, is more common (90% of all cases) and typically develops in childhood. Approximately 80% of children with asthma also have documented allergies. Typically, there is a family history of allergies. Additionally, other allergic conditions, such as nasal allergies or eczema, are often also present. Allergic asthma often goes into remission in early adulthood. However, in 75% of cases, the asthma reappears later.

Intrinsic asthma represents about 10% of all cases. It usually develops after the age of 30 and is not typically associated with allergies. Women are more frequently involved and many cases seem to follow a respiratory tract infection. The condition can be difficult to treat and symptoms are often chronic and year-round.

Typical symptoms and signs of asthma

The symptoms of asthma vary from person to person and in any individual from time to time. It is important to remember that many of these symptoms can be subtle and similar to those seen in other conditions. All of the symptoms mentioned below can be present in other respiratory, and sometimes, in heart conditions. This potential confusion makes identifying the settings in which the symptoms occur and diagnostic testing very important in recognizing this disorder.

The Four Major Recognized Symptoms:

• Shortness of breath – especially with exertion or at night
• Wheezing – a whistling or hissing sound when breathing out
• Coughing – may be chronic; usually worse at night and early morning; and may occur after exercise or when exposed to cold, dry air
• Chest tightness – may occur with or without the above symptoms

Acute asthma attack

An acute, or sudden, asthma attack is usually caused by an exposure to allergens or an upper respiratory tract infection. The severity of the attack depends on how well your underlying asthma is being controlled (reflecting how well the airway inflammation is being controlled). An acute attack is potentially life-threatening because it may continue despite the use of your usual quick-relief medications (inhaled bronchodilators). Asthma that is unresponsive to treatment with an inhaler should prompt you to seek medical attention at the closest hospital emergency room or your asthma specialist office, depending on the circumstances and time of day. Asthma attacks do not stop on their own without treatment. If you ignore the early warning signs, you put yourself at risk of developing “status asthmaticus.”

Allergy Fact

Prolonged attacks of asthma that do not respond to treatment with bronchodilators are a medical emergency. Physicians call these severe attacks “status asthmaticus,” and they require immediate emergency care.

The symptoms of severe asthma are persistent coughing and the inability to speak full sentences or walk without shortness of breath. Your chest may feel closed and your lips may have a bluish tint. In addition, you may feel agitation, confusion, or an inability to concentrate. You may hunch your shoulders, sit or stand up to breathe more easily, and strain your abdominal and neck muscles. These are signs of an impending respiratory system failure. At this point, it is unlikely that inhaled medications will reverse this process. A mechanical ventilator may be needed to assist the lungs and respiratory muscles. A face mask or a breathing tube is inserted in the nose or mouth for this treatment. These breathing aids are temporary and are removed once the attack has subsided and the lungs have recovered sufficiently to resume the work of breathing on their own. A short hospital stay in an intensive care unit may be a result of a severe attack that has not been promptly treated. To avoid such hospitalization, it is best, at the onset of symptoms, to begin immediate early treatment at home or in your doctor’s office.

Allergy Fact

The presence of wheezing or coughing in and of itself is not a reliable standard for judging the severity of an asthma attack. Very severe attacks may clog the tubes to such a degree that the lack of air in and out of your lungs fails to produce wheezing or coughing.

What medications are used in the treatment of asthma?

Most asthma medications work by relaxing bronchospasm (bronchodilators) or reducing inflammation (corticosteroids). In the treatment of asthma, inhaled medications are generally preferred over tablet or liquid medicines which are swallowed (oral medications). Inhaled medications act directly on the airway surface and airway muscles where the asthma problems initiate. Absorption of inhaled medications into the rest of the body is minimal. Therefore, adverse side effects are fewer as compared to oral medications. Inhaled medications include beta-2 agonists, anticholinergics, corticosteroids, and cromolyn sodium. Oral medications include aminophylline, leukotriene antagonists, and corticosteroid tablets.

Historically, one of the first medications used for asthma was adrenaline (epinephrine). Adrenaline has a rapid onset of action in opening the airways (bronchodilation). It is still often used in emergency situations for asthma. Unfortunately, adrenaline has many side effects, including rapid heart rate, headache, nausea, vomiting, restlessness, and a sense of panic.

Medications chemically similar to adrenaline have been developed. These medications, called beta-2 agonists, have the bronchodilating benefits of adrenaline without many of its unwanted side-effects. Beta-2 agonists are inhaled bronchodilators which are called “agonists” because they promote the action of the beta-2 receptor of bronchial wall muscle. This receptor acts to relax the muscular wall of the airways (bronchi), resulting in bronchodilation. The bronchodilator action of beta- 2 agonists starts within minutes after inhalation and lasts for about four hours. Examples of these medications include albuterol (Ventolin, Proventil), metaproterenol (Alupent), pirbuterol acetate (Maxair), and terbutaline sulfate (Brethaire).

A new group of long-acting beta-2 agonists has been developed with a sustained duration of effect of 12 hours. These inhalers can be taken twice a day. Salmeterol xinafoate (Serevent) is an example of this group of medications. The long-acting beta-2 agonists are generally not used for acute attacks. Beta-2 agonists can have side effects, such as anxiety, tremor, palpitations or fast heart rate, and lowering of blood potassium.

Just as beta-2 agonists can dilate the airways, beta blocker medications impair the relaxation of bronchial muscle by beta-2 receptors and can cause constriction of airways, aggravating asthma. Therefore, beta blockers, such as the blood pressure medications propanolol (Inderal), and atenolol (Tenormin), should be avoided by asthma patients if possible.

The anticholinergic agents act on a different type of nerves than the beta-2 agonists to achieve a similar relaxation and opening of the airway passages. These two groups of bronchodilator inhalers when used together can produce an enhanced bronchodilation effect. An example of a commonly used anticholinergic agent is ipratropium bromide (Atrovent). Ipratropium takes longer to work as compared with the beta-2 agonists, with peak effectiveness occurring two hours after intake and lasting six hours. Anticholinergic agents can also be very helpful medications for patients with emphysema.

When symptoms of asthma are difficult to control with beta-2 agonists, inhaled corticosteroids (cortisone) are often added. Corticosteroids can improve lung function and reduce airway obstruction over time. Examples of inhaled corticosteroids include beclomethasone dipropionate (Beclovent, Beconase, Vancenase, and Vanceril), triamcinolone acetonide (Azmacort), and flunisolide (Aerobid). The ideal dose of corticosteroids is still unknown. The side effects of inhaled corticosteroids include hoarseness, loss of voice, and oral yeast infections. Early use of inhaled corticosteroids may prevent irreversible damage to the airways.

Cromolyn sodium (Intal) prevents the release of certain chemicals in the lungs, such as histamine, which can cause asthma. Exactly how cromolyn works to prevent asthma needs further research. Cromolyn is not a corticosteroid and is usually not associated with significant side effects. Cromolyn is useful in preventing asthma but has limited effectiveness once acute asthma starts. Cromolyn can help prevent asthma triggered by exercise, cold air, and allergic substances, such as cat dander. Cromolyn may be used in children as well as adults.

Theophylline (Theodur, Theoair, Slo-bid, Uniphyl, Theo-24) and aminophylline are examples of methylxanthines. Methylxanthines are administered orally or intravenously. Before the inhalers became popular, methylxanthines were the mainstay of treatment of asthma. Caffeine that is in common coffee and soft drinks is also a methylxanthine drug! Theophylline relaxes the muscles surrounding the air passages and prevents certain cells lining the bronchi (mast cells) from releasing chemicals, such as histamine, which can cause asthma. Theophylline can also act as a mild diuretic, causing an increase in urination. For asthma that is difficult to control, methylxanthines can still play an important role. Dosage levels of theophylline or aminophylline are closely monitored. Excessive levels can lead to nausea, vomiting, heart rhythm problems, and even seizures. In certain medical conditions, such as heart failure or cirrhosis, dosages of methylxanthines are lowered to avoid excessive blood levels. Drug interactions with other medications, such as cimetidine (Tagamet), calcium channel blockers (Procardia), quinolones (Cipro), and allopurinol (Xyloprim) can further affect drug blood levels.

Corticosteroids are given orally for severe asthma unresponsive to other medications. Unfortunately, high doses of corticosteroids over long periods can have serious side effects, including osteoporosis, bone fractures, diabetes mellitus, high blood pressure, thinning of the skin and easy bruising, insomnia, emotional changes, and weight gain.

Expectorants help thin airway mucus, making it easier to clear the mucus by coughing. Potassium iodide is not commonly used and has the potential side-effects of acne, increased salivation, hives, and thyroid problems. Guaifenesin (Entex, Humibid) can increase the production of fluid in the lungs and help thin the mucus, but can also be an airway irritant for some people.

In addition to bronchodilator medications for those patients with atopic asthma, avoiding allergens or other irritants can be very important. In patients who cannot avoid the allergens, or in those whose symptoms cannot be controlled by medications, allergy shots are considered. The benefits of allergy shots (desensitization) in the prevention of asthma has not been firmly established. Some doctors are still concerned about the risk of anaphylaxis, which occurs in one in 2 million doses given. Allergy shots most commonly benefit children allergic to house dust mites. Other benefits can be seen with pollens and animal dander.

In some asthma patients, avoidance of aspirin, or other NSAIDs (commonly used in treating arthritis inflammation) is important. In other patients, adequate treatment of backflow of stomach acid (esophageal reflux) prevents irritation of the airways. Measures to prevent esophageal reflux include medications, weight loss, dietary changes, and stopping cigarettes, coffee, and alcohol. Examples of medications used to reduce reflux include omeprazole (Prilosec) and ranitidine (Zantac). Patients with severe reflux problems causing lung problems may need surgery to strengthen the esophageal sphincter in order to prevent acid reflux (fundoplication surgery). For further information, please read the Gastroesophageal Reflux Disease article.

Asthma At A Glance

• Asthma is a chronic inflammation of the bronchial tubes (airways) that causes swelling and narrowing (constriction) of the airways. The bronchial narrowing is usually either totally or at least partially reversible with treatments.

• Asthma is now the most common chronic illness in children, affecting one in every 15.

• Asthma involves only the bronchial tubes and usually does not affect the air sacs or the lung tissue. The narrowing that occurs in asthma is caused by three major factors; inflammation, bronchospasm, and hyperreactivity.

• Allergy can play a role in some, but not all, asthma patients.

• Many factors can precipitate asthma attacks and are they are classified as either allergens or irritants.

• Symptoms of asthma include shortness of breath, wheezing, cough, and chest tightness.

• Asthma is usually diagnosed based on the presence of wheezing and confirmed with breathing tests.

• Chest x-rays are usually normal in asthma patients.

• Avoiding precipitating factors is important in the management of asthma.

• Medications can be used to reverse or prevent bronchospasm in patients with asthma.

REFERENCES: Murray, J., Nadel, J. (2000). Textbook of Respiratory Medicine. Third edition. Philadelphia: W.B Saunders Company.

Davies, S. Peak expiratory flow rate monitoring in asthma. In: UpToDate, Rose, BD (Ed), UpToDate, Wellesley, MA, 2005.

Kohler, C. Metered dose inhaler techniques in adults. In: UpToDate, Rose, BD (Ed), UpToDate, Wellesley, MA, 2005.

Medically Reviewed By: Ellen Reich, MD, Board Certified in Allergy and Immunology, Board Certified in Pediatrics

The lungs are a pair of organs in the chest that are primarily responsible for the exchange of oxygen and carbon dioxide between the air we breathe and the blood.

The lung is composed of clusters of small air sacs (alveoli) divided by thin, elastic walls or membranes. Capillaries, the tiniest of blood vessels, run within these walls between the alveoli and allow blood and air to come near each other. The distance between the air in the lungs and the blood in the capillaries is very small, and allows molecules of oxygen and carbon dioxide to transfer across the membranes.

Air reaches the alveoli via the bronchial tree. The trachea splits into the right and left mainstem bronchi, which branch further into bronchioles and finally ends in the alveolar air sacs.

When we breathe in, air enters the lung and the alveoli expand. Oxygen is transferred onto hemoglobin molecules in the red blood cells to be transported to the rest of the body for use. As oxygen attaches to the red blood cell, carbon dioxide, the waste product of metabolism, detaches and crosses into the alveoli to be exhaled. When we breathe out, the alveoli get squeezed by the elasticity in their walls and air is pushed out of the lungs.

What is emphysema?

Emphysema is a long-term, progressive disease of the lung(s) and occurs when the alveolar walls are destroyed along with the capillary blood vessels that run within them. This lessens the total area within the lung where blood and air can come together, limiting the potential for oxygen and carbon dioxide transfer.

In early emphysema, there is associated inflammation of the small airways or bronchioles that limits the amount of air that can flow to the alveoli. In more severe emphysema, there is also loss of elasticity in the alveolar walls that have not been destroyed. When the patient breathes out, the alveoli and small airways collapse. This makes it hard for air to get out of the lungs and makes it even harder for new air to enter.

As more of the lung is destroyed and the lung cannot maintain oxygen concentrations in the bloodstream, the body compensates by gradually increasing the breathing rate. After a while, even hyperventilation (hyper=more + ventilation=breathing) cannot maintain adequate oxygen levels, and the arteries in the lung begin to constrict or narrow. The heart has to work harder to push blood into these narrower blood vessels, causing the blood pressure in the lung arteries to increase (pulmonary hypertension). Over time, the extra work requirement causes the heart muscle to enlarge (hypertrophy) and can cause heart failure.

What are the causes or risk factors for emphysema?

• The main cause of emphysema is smoking, which activates inflammatory cells in the lung. This inflammation causes; 1) swelling within the bronchioles, and 2) activation of enzymes called proteases which attack and destroy lung tissue (the alveolar wall structures).
• There is a genetic predisposition to emphysema. The relatively rare condition known as alpha 1-antitrypsin deficiency is the genetic deficiency of a chemical that protects the lung from damage by proteases.
• Emphysema is also a component of aging. As the lungs get older, the elastic properties decrease, and the tensions that develop can result in small areas of emphysema.

Other less common causes of emphysema include:

• Intravenous drug use in which some of the non-drug additives like corn starch can be toxic to lung tissue
• Immune deficiencies in which infections like Pneumocystis carinii can cause inflammatory changes in the lung
• Connective tissue illnesses (Ehlers-Danlos Syndrome, Marfan syndrome) in which abnormal elastic tissue in the body can cause alveoli to fail

In underdeveloped countries, a common cause of emphysema is indoor air pollution. In these populations, it is very common to have indoor stoves in the kitchen. The smoke from cooking results in the damage to the lungs.

What are symptoms of emphysema?

Emphysema is a progressive disease that usually manifests itself in patients after 50 years of age. Emphysema is a subtype of chronic obstructive pulmonary disease (COPD in the US, COLD in the United Kingdom). Most patients, except in those in whom disease is the result of a genetic deficiency (alpha-1 antitrypsin deficiency), have variable manifestations of the different components of COPD which include:

• chronic bronchitis,
• asthma,
• emphysema, and
• bronchiectasis.

Each of the subtypes has characteristic symptoms; those primarily associated with emphysema are shortness of breath and wheezing. Initially the shortness of breath (dyspnea) occurs with activity; as time continues and the disease progresses, the episodes of dyspnea occur more frequently eventually occurring at rest.

How is emphysema diagnosed?

As is the case with most illnesses, the healthcare provider will take a careful history to learn about the lung and breathing symptoms.

• How long has the shortness of breath been present?
• What makes it better?
• What makes it worse?
• Has there been an infection recently?
• Have the symptoms been getting more severe?
• Does the patient smoke?
• Does the patient have exposure to secondhand smoke or other toxic fumes?
• Is there a family history of lung disease?

Physical examination

Physical examination will concentrate on the lung findings, but may also include the heart and the circulatory system.

• Is there an increased respiratory rate?
• Is the patient short of breath just sitting in the examination room?
• Is the patient using accessory muscles to breathe, in addition to the rib muscles and the diaphragm?
• Is the chest cavity enlarged or barrel-shaped?
• Does the chest cavity sound hollower than it should?
• Does exhalation take longer than it should?
• Is the movement of the diaphragm decreased?
• Is the patient cyanotic (having a blue tinge to the skin color signifying lack of oxygen in the blood)?
• Listening to the lungs, are there wheezes present, especially if the patient is asked to exhale quickly?

Exams and tests

Oximetry

Oxygenated blood is a brighter red and becomes purpler in color when oxygen is removed. The oximeter is a device usually placed on a finger and detects the pulse of blood. A light is transmitted through the tissue, and the amount of the brighter red color is determined, enabling a measure of oxygen saturation, a measure of hemoglobin oxygen content. This value is usually greater than 90%.

Blood Tests

A complete blood cell count (CBC) may be performed to check for an increase in the number of red blood cells. In response to lower blood oxygen concentrations, the body manufactures more red blood cells to try to deliver as much oxygen as possible to cells.

Alpha 1-antitrypsin levels may be measured to look for any genetic predisposition to emphysema.

An arterial blood gas test will measure the amount of oxygen and carbon dioxide in the blood and combined with other measurements can help the healthcare provider decide whether the body has been able to adapt to the lower oxygen concentrations in the body. In some laboratories, the arterial blood gas result will include a carbon monoxide percentage, most often found in the body because of smoking. For each hemoglobin molecule that has carbon monoxide attached, there is one less that can carry oxygen.

Radiology

A plain chest x-ray may show lungs that have become too inflated and too lucent, signs that lung tissue destruction has occurred.

Pulmonary Function Tests

A variety of lung functions can be measured and may include how much air the lungs can hold and empty with each breath, the degree of airflow obstruction, the available surface for exchange of carbon dioxide and oxygen, the amount of trapped gases, and how elastic the lungs are with inspiration and expiration. By comparing results to a “normal” person of the same age, sex and size, estimations can be made as to the severity of the emphysema.

What is the treatment for emphysema?

Emphysema is not a curable disease, once lung damage has occurred it cannot be reversed. The goal of treatment is to stop further lung destruction and preserve lung function. The patient needs to know that the focus is on improving quality of life and limiting the intrusion of emphysema on daily activities.

Smoking cessation

The number one treatment goal is to have the patient stop smoking. Education, counseling, support groups and medication may be used.

Medications

Bronchodilators

Bronchodilators are used to relax the smooth muscles that surround the bronchioles and allow the breathing tubes to dilate and allow more air flow. These medications can be inhaled using an MDI (metered dose inhaler), powder inhaler devices, or a nebulizer machine These medications can either be short or long acting. Recently, the propellant for the MDIs , chlorofluorocarbons (CFCs) have been removed from the market because of the effect of these agents on the ozone layer in the atmosphere. These propellants have been replaced with hydrofluoric alkanes (HFAs).

The short acting bronchodilators include the albuterol agents (Ventolin HFA, Proventil HFA, and Pro Air) and the anticholinergic agent, ipratropium bromide (Atrovent).

As an aside, in the past patients have been instructed to count the number of puffs used from these devices or “float” the inhaler in water to determine the amount of remaining medicine available. The HFA devices can not be floated, and counting of the number of puffs is the only available method of determining the continued presence of medication. One device, Ventolin HFA, has a built in counter. It is important to understand that the mere presence of propellant coming from the inhaler does not necessarily mean that medication is present.

The long acting agents include salmeterol (Serevent), formoterol (Foradil) and tiotropium (Spiriva). Often the long acting bronchodilator is used for controlling the symptoms of emphysema as maintenance therapy, and the short acting one is used when symptoms flare up (rescue therapy). It is important that the patient know which medication is prescribed, since long acting inhalers cannot be used for rescue because the delayed onset of action.

Corticosteroids

Since most patients do not have pure emphysema and usually also have other components of COPD, combined therapy is often prescribed which includes a long-acting bronchodilator and an inhaled corticosteroid. The inhaled corticosteroid (ICS) helps suppress the inflammatory components of COPD. These agents like Advair, which is a mixture of salmeterol (Serevent) and fluticasone (Flovent), an ICS, further simplify treatment to a single inhaler device. Studies have been done in Europe on a similar agent, Symbicort [a combination of formoterol (Foradil) and budesonide (Pulmicort), another ICS], and are currently underway in the United States.

Many patients with emphysema need only take steroids when their symptoms flare, but others require daily therapy. Corticosteroids have direct action on the lung tissue. Absorption into the blood stream is minimal. Prednisone, an oral corticosteroid, can be taken in addition to the inhaled steroid should further anti-inflammatory effects be required. In emergency situations, corticosteroids may be injected intravenously.

Antibiotics

Since patients with emphysema are at risk for infections like pneumonia, antibiotics may be prescribed when the usually clear sputum changes color, or when the patient presents with systemic signs of an infection (fever, chills, weakness).

Oxygen

As the disease progresses, patients may require supplemental oxygen to be able to function. Often it begins with nighttime use, then with exercise, and as the disease worsens, the need to use oxygen during the day for routine activities increases.

The earliest type of medicine in most cultures was the use of empirical natural resources like plants (herbalism), animal parts and minerals. In all societies, including Western ones, there were also religious, ritual and magical resources. In aboriginal societies, there is a large scope of medical systems related to religious thinking, cultural experience, and natural resources. The religious ones more known are : animism (the notion of inanimate objects having spirits); spiritualism (here meaning an appeal to gods or communion with ancestor spirits); shamanism (the vesting of an individual with mystic powers); and divination (the supposed obtaining of truth by magic means). The field of medical anthropology studies the various medical systems and their interaction with society, while prehistoric medicine addresses diagnosis and treatment in prehistoric times.

The practice of medicine developed gradually in ancient Egypt, Babylonia, India, China, Greece, Persia, the Islamic world, medieval Europe and early modern period in Persia (Rhazes and Avicenna), Spain (Abulcasis and Avenzoar), Syria/Egypt (Ibn al-Nafis, 13th century), Italy (Gabriele Falloppio, 16th century), England (William Harvey, 17th century). Medicine as it is now practiced largely developed during the 19th and 20th centuries in Germany (Rudolf Virchow, Wilhelm Conrad Röntgen, Robert Koch), Austria (Karl Landsteiner, Otto Loewi), United Kingdom (Edward Jenner, Alexander Fleming, Joseph Lister, Francis Crick), New Zealand (Maurice Wilkins), Australia (Howard Floery, Frank Macfarlane Burnet), Russia (Nikolai Korotkov), United States (William Williams Keen, Harvey Cushing, William Coley, James D. Watson), Italy (Salvador Luria), Switzerland (Alexandre Yersin), Japan (Kitasato Shibasaburo), and France (Jean-Martin Charcot, Claude Bernard, Louis Pasteur, Paul Broca and others). The new “scientific” or “experimental” medicine (where results are testable and repeatable) replaced early Western traditions of medicine, based on herbalism, the Greek “four humours” and other pre-modern theories.

The Sumerian god Ningizzida was the patron of medicine. In the image he is accompanied by two gryphons. It is the oldest known image of snakes coiling around an axial rod, dating from before 2000 BCE. A similar image with two snakes coiling around a rod is called the Caduceus and, although historically inappropriate, appears in the logo/emblem of a significant number of private (rather than professional or academic) medical practices.

The focal points of development of clinical medicine shifted^{[citation needed]} to the United Kingdom and the USA^{[citation needed]} by the early 1900s (Canadian-born) Sir William Osler, Harvey Cushing). Possibly the major shift in medical thinking was the gradual rejection, especially during the Black Death in the 14th and 15th centuries, of what may be called the ‘traditional authority’ approach to science and medicine. This was the notion that because some prominent person in the past said something must be so, then that was the way it was, and anything one observed to the contrary was an anomaly (which was paralleled by a similar shift in European society in general – see Copernicus‘s rejection of Ptolemy‘s theories on astronomy). Physicians like Ibn al-Nafis and Vesalius led the way in improving upon or indeed rejecting the theories of great authorities from the past (such as Hippocrates, Galen and Avicenna), many of whose theories were in time discredited. Such new attitudes were made possible in Europe by the weakening of the Roman Catholic church’s power in society, especially in the Republic of Venice.

Evidence-based medicine is a recent movement to establish the most effective algorithms of practice (ways of doing things) through the use of the scientific method and modern global information science by collating all the evidence and developing standard protocols which are then disseminated to healthcare providers. One problem with this ‘best practice’ approach is that it could be seen to stifle novel approaches to treatment.

Drug ampoules

Genomics and knowledge of human genetics is already having some influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology and genetics are influencing medical practice and decision-making.

Pharmacology has developed from herbalism and many drugs are still derived from plants (atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc). The modern era began with Robert Koch‘s discoveries around 1880 of the transmission of disease by bacteria, and then the discovery of antibiotics shortly thereafter around 1900. The first of these was arsphenamine / Salvarsan discovered by Paul Ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. The first major class of antibiotics was the sulfa drugs, derived by French chemists originally from azo dyes. Throughout the twentieth century, major advances in the treatment of infectious diseases were observable in (Western) societies. The medical establishment is now developing drugs targeted towards one particular disease process. Thus drugs are being developed to minimise the side effects of prescribed drugs, to treat cancer, geriatric problems, long-term problems (such as high cholesterol), chronic diseases type 2 diabetes, lifestyle and degenerative diseases such as arthritis and Alzheimer’s disease.

Practice of medicine

he practice of medicine combines both science as the evidence base and art in the application of this medical knowledge in combination with intuition and clinical judgment to determine the treatment plan for each patient.Central to medicine is the patient-physician relationship established when a person with a health concern seeks a physician’s help; the ‘medical encounter’. Other health professionals similarly establish a relationship with a patient and may perform various interventions, e.g. nurses, radiographers and therapists.

As part of the medical encounter, the healthcare provider needs to:

• develop a relationship with the patient
• gather data (medical history, systems enquiry, and physical examination, combined with laboratory or imaging studies (investigations))
• analyze and synthesize that data (assessment and/or differential diagnoses), and then:
• develop a treatment plan (further testing, therapy, watchful observation, referral and follow-up)
• treat the patient accordingly
• assess the progress of treatment and alter the plan as necessary (management).

The medical encounter is documented in a medical record, which is a legal document in many jurisdictions.^[3]

[edit] Health care delivery systems

Medicine is practiced within the medical system, which is a legal, credentialing and financing framework, established by a particular culture or government. The characteristics of a health care system have significant effect on the way medical care is delivered.

Most industrialized countries and many developing countries deliver health care though a system of universal health care which guarantees health care for all through a system of compulsory private or co-operative health insurance funds or via government backed social insurance. This insurance, (in effect, a form of taxation) ensures the entire population has access to medical care on the basis of need rather than ability to pay. The delivery systems may be provided by private medical practices or by state owned hospitals and clinics, or by charities.

Most tribal societies but also some communist countries (e.g. China) and at least one industrialized capitalist country (the United States) provide no guarantee of health care for the population as a whole. In such societies, health care is available to those that can afford to pay for it or have self insured it (either directly or as part of an employment contract) or who may be covered by care financed by the government or tribe directly.

Transparency of information is another factor defining a delivery system. Access to information on conditions, treatments, quality and pricing greatly affects the choice by patients / consumers and therefore the incentives of medical professionals. While US health care system has come under fire for lack of openness, new legislation may encourage greater openness. There is a perceived tension between the need for transparency on the one hand and such issues as patient confidentiality and the possible exploitation of information for commercial gain on the other.

Health care delivery

Medical care delivery is classified into primary, secondary and tertiary care.

Primary care medical services are provided by physicians or other health professionals who have first contact with a patient seeking medical treatment or care. These occur in physician offices, clinics, nursing homes, schools, home visits and other places close to patients. About 90% of medical visits can be treated by the primary care provider. These include treatment of acute and chronic illnesses, preventive care and health education for all ages and both sexes.

Secondary care medical services are provided by medical specialists in their offices or clinics or at local community hospitals for a patient referred by a primary care provider who first diagnosed or treated the patient. Referrals are made for those patients who required the expertise or procedures performed by specialists. These include both ambulatory care and inpatient services, emergency rooms, intensive care medicine, surgery services, physical therapy, labor and delivery, endoscopy units, diagnostic laboratory and medical imaging services, hospice centers, etc. Some primary care providers may also take care of hospitalized patients and deliver babies in a secondary care setting.

Tertiary care medical services are provided by specialist hospitals or regional centers equipped with diagnostic and treatment facilities not generally available at local hospitals. These include trauma centers, burn treatment centers, advanced neonatology unit services, organ transplants, high-risk pregnancy, radiation oncology, etc.

Modern medical care also depends on information – still delivered in many health care settings on paper records, but increasingly nowadays by electronic means.

Patient-physician-relationship

his kind of relationship and interaction is a central process in the practice of medicine. There are many perspectives from which to understand and describe it.An idealized physician’s perspective, such as is taught in medical school, sees the core aspects of the process as the physician learning the patient’s symptoms, concerns and values; in response the physician examines the patient, interprets the symptoms, and formulates a diagnosis to explain the symptoms and their cause to the patient and to propose a treatment. The job of a physician is similar to a human biologist: that is, to know the human frame and situation in terms of normality. Once the physician knows what is normal and can measure the patient against those norms, he or she can then determine the particular departure from the normal and the degree of departure. This is called the diagnosis.

The four great cornerstones of diagnostic medicine are anatomy (structure: what is there), physiology (how the structure/s work), pathology (what goes wrong with the anatomy and physiology) and psychology (mind and behavior). In addition, the physician should consider the patient in their ‘well’ context rather than simply as a walking medical condition. This means the socio-political context of the patient (family, work, stress, beliefs) should be assessed as it often offers vital clues to the patient’s condition and further management.

A patient typically presents a set of complaints (the symptoms) to the physician, who then obtains further information about the patient’s symptoms, previous state of health, living conditions, and so forth. The physician then makes a review of systems (ROS) or systems inquiry, which is a set of ordered questions about each major body system in order: general (such as weight loss), endocrine, cardio-respiratory, etc. Next comes the actual physical examination and often laboratory tests; the findings are recorded, leading to a list of possible diagnoses. These will be investigated in order of probability.

The next task is to enlist the patient’s agreement to a management plan, which will include treatment as well as plans for follow-up. Importantly, during this process the healthcare provider educates the patient about the causes, progression, outcomes, and possible treatments of his ailments, as well as often providing advice for maintaining health. This teaching relationship is the basis of calling the physician doctor, which originally meant “teacher” in Latin. The patient-physician relationship is additionally complicated by the patient’s suffering (patient derives from the Latin patior, “suffer”) and limited ability to relieve it on his/her own. The physician’s expertise comes from his knowledge of what is healthy and normal contrasted with knowledge and experience of other people who have suffered similar symptoms (unhealthy and abnormal), and the proven ability to relieve it with medicines (pharmacology) or other therapies about which the patient may initially have little knowledge.

The physician-patient relationship can be analyzed from the perspective of ethical concerns, in terms of how well the goals of non-maleficence, beneficence, autonomy, and justice are achieved. Many other values and ethical issues can be added to these. In different societies, periods, and cultures, different values may be assigned different priorities. For example, in the last 30 years medical care in the Western World has increasingly emphasized patient autonomy in decision making.

The relationship and process can also be analyzed in terms of social power relationships (e.g., by Michel Foucault), or economic transactions. Physicians have been accorded gradually higher status and respect over the last century, and they have been entrusted with control of access to prescription medicines as a public health measure. This represents a concentration of power and carries both advantages and disadvantages to particular kinds of patients with particular kinds of conditions. A further twist has occurred in the last 25 years as costs of medical care have risen, and a third party (an insurance company or government agency) now often insists upon a share of decision-making power for a variety of reasons, reducing freedom of choice of healthcare providers and patients in many ways.

The quality of the patient-physician relationship is important to both parties. The better the relationship in terms of mutual respect, knowledge, trust, shared values and perspectives about disease and life, and time available, the better will be the amount and quality of information about the patient’s disease transferred in both directions, enhancing accuracy of diagnosis and increasing the patient’s knowledge about the disease. Where such a relationship is poor the physician’s ability to make a full assessment is compromised and the patient is more likely to distrust the diagnosis and proposed treatment. In these circumstances and also in cases where there is genuine divergence of medical opinions, a second opinion from another physician may be sought or the patient may choose to go to another doctor.

In some settings, e.g. the hospital ward, the patient-physician relationship is much more complex, and many other people are involved when somebody is ill: relatives, neighbors, rescue specialists, nurses, technical personnel, social workers and others.

Clinical skills

A complete medical evaluation includes a medical history, a systems enquiry, a physical examination, appropriate laboratory or imaging studies, analysis of data and medical decision making to obtain diagnoses, and a treatment plan.^[4]

The components of the medical history are:

• Chief complaint (CC): the reason for the current medical visit. These are the ‘symptoms.’ They are in the patient’s own words and are recorded along with the duration of each one. Also called ‘presenting complaint.’
• History of present illness / complaint (HPI): the chronological order of events of symptoms and further clarification of each symptom.
• Current activity: occupation, hobbies, what the patient actually does.
• Medications (DHx): what drugs the patient takes including prescribed, over-the-counter, and home remedies, as well as alternative and herbal medicines/herbal remedies such as St John’s wort. Allergies are also recorded.
• Past medical history (PMH/PMHx): concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases and/or vaccinations, history of known allergies.
• Social history (SH): birthplace, residences, marital history, social and economic status, habits (including diet, medications, tobacco, alcohol).
• Family history (FH): listing of diseases in the family that may impact the patient. A family tree is sometimes used.

• Review of systems (ROS) or systems inquiry: a set of additional questions to ask which may be missed on HPI: a general enquiry (have you noticed any weight loss, fevers, lumps and bumps? etc), followed by questions on the body’s main organ systems (heart, lungs, digestive tract, urinary tract, etc).

The physical examination is the examination of the patient looking for signs of disease (‘Symptoms’ are what the patient volunteers, ‘Signs’ are what the healthcare provider detects by examination). The healthcare provider uses the senses of sight, hearing, touch, and sometimes smell (taste has been made redundant by the availability of modern lab tests). Four chief methods are used: inspection, palpation (feel), percussion (tap to determine resonance characteristics), and auscultation (listen); smelling may be useful (e.g. infection, uremia, diabetic ketoacidosis). The clinical examination involves study of:

• Vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, hemoglobin oxygen saturation
• General appearance of the patient and specific indicators of disease (nutritional status, presence of jaundice, pallor or clubbing)
• Skin
• Head, eye, ear, nose, and throat (HEENT)
• Cardiovascular (heart and blood vessels)
• Respiratory (large airways and lungs)
• Abdomen and rectum
• Genitalia (and pregnancy if the patient is or could be pregnant)
• Musculoskeletal (spine and extremities)
• Neurological (consciousness, awareness, brain, cranial nerves, spinal cord and peripheral nerves)
• Psychiatric (orientation, mental state, evidence of abnormal perception or thought)

Laboratory and imaging studies results may be obtained, if necessary.

The medical decision-making (MDM) process involves analysis and synthesis of all the above data to come up with a list of possible diagnoses (the differential diagnoses), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient’s problem.

The treatment plan may include ordering additional laboratory tests and studies, starting therapy, referral to a specialist, or watchful observation. Follow-up may be advised.

This process is used by primary care providers as well as specialists. It may take only a few minutes if the problem is simple and straightforward. On the other hand, it may take weeks in a patient who has been hospitalized with bizarre symptoms or multi-system problems, with involvement by several specialists.

On subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, and lab or imaging results or specialist consultations.

Branches of medicine

Working together as an interdisciplinary team, many highly-trained health professionals besides medical practitioners are involved in the delivery of modern health care. Examples include: nurses, emergency medical technicians and paramedics, laboratory scientists, (pharmacy, pharmacists), (physiotherapy,physiotherapists), respiratory therapists, speech therapists, occupational therapists, radiographers, dietitians and bioengineers.

The scope and sciences underpinning human medicine overlap many other fields. Dentistry and psychology, while separate disciplines from medicine, are considered medical fields.

A patient admitted to hospital is usually under the care of a specific team based on their main presenting problem, eg the Cardiology team, who then may interact with other specialties, eg surgical, radiology, to help diagnose or treat the main problem or any subsequent complications/ developments.

Physicians have many specializations and subspecializations into certain branches of medicine, which are listed below. There are variations from country to country regarding which specialties certain subspecialties are in.

The main branches of medicine used in Wikipedia are:

• Basic sciences of medicine; this is what every physician is educated in, and some returns to in Biomedical research#Preclinical research.
• Medical specialties
• interdisciplinary fields, where different medical specialties are mixed to function in certain occasions.

[edit] Basic sciences

• Anatomy is the study of the physical structure of organisms. In contrast to macroscopic or gross anatomy, cytology and histology are concerned with microscopic structures.
• Biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components.
• Biostatistics is the application of statistics to biological fields in the broadest sense. A knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. It is also fundamental to epidemiology and evidence-based medicine.
• Cytology is the microscopic study of individual cells.
• Embryology is the study of the early development of organisms.
• Epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics.
• Genetics is the study of genes, and their role in biological inheritance.
• Histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry.
• Immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example.
• Microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses.
• Neuroscience includes those disciplines of science that are related to the study of the nervous system. A main focus of neuroscience is the biology and physiology of the human brain and spinal cord.
• Nutrition is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. Medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases.
• Pathology as a science is the study of disease—the causes, course, progression and resolution thereof.
• Pharmacology is the study of drugs and their actions.
• Physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms.
• Toxicology is the study of hazardous effects of drugs and poisons.

[edit] Medical specialties

Main article: Medical specialty

In the broadest meaning of ‘medicine’, there are many different specialties. However, within medical circles, there are two broad categories: “Medicine” and “Surgery.” “Medicine” refers to the practice of non-operative medicine, and most subspecialties in this area require preliminary training in “Internal Medicine.” “Surgery” refers to the practice of operative medicine, and most subspecialties in this area require preliminary training in “General Surgery.” There are some specialties of medicine that do not fit into either of these categories, such as radiology, pathology, or anaesthesia, and those are also discussed further below.

[edit] Surgery

Surgical specialties employ operative treatment. In addition, surgeons must decide when an operation is necessary, and also treat many non-surgical issues, particularly in the surgical intensive care unit (SICU), where a variety of critical issues arise. Surgery has many subspecialties, e.g. general surgery, trauma surgery, cardiovascular surgery, neurosurgery, maxillofacial surgery, orthopedic surgery, otolaryngology, plastic surgery, oncologic surgery, vascular surgery, and pediatric surgery. In some centres, anesthesiology is part of the division of surgery (for logistical and planning purposes), although it is not a surgical discipline.

Surgical training in the U.S. requires a minimum of five years of residency after medical school. Sub-specialties of surgery often require seven or more years. In addition, fellowships can last an additional one to three years. Because post-residency fellowships can be competitive, many trainees devote two additional years to research. Thus in some cases surgical training will not finish until more than a decade after medical school. Furthermore, surgical training can be very difficult and time-consuming. A surgical resident’s average work week is approximately 75 hours. Some subspecialties of surgery, such as neurosurgery, require even longer hours, and utilize an extension to the 80 hour regulated work week, allowing up to 88 hours per week. Many surgical programs still exceed this work hour limit. Attempts to limit the amount of hours worked has been difficult because of the large volume of patients who require surgical care, the limited amount of resources (including a shortage of people willing to enter into surgery as a career)^[5], the need to perform long operations and still provide care to all pre- and post-operative patients, and the need to provide constant coverage in the OR, ICU, and ER.

[edit] Medicine

• Internal medicine is concerned with systemic diseases of adults, i.e. those diseases that affect the body as a whole (restrictive, current meaning), or with all adult non-operative somatic medicine (traditional, inclusive meaning), thus excluding pediatrics, surgery, gynaecology and obstetrics, and psychiatry. Practitioners of such specialties are referred to as Physicians. There are several subdisciplines of internal medicine:
  • Cardiology
  • Critical care medicine
  • Endocrinology
  • Gastroenterology
  • Hepatology
  • Hematology
  • Infectious diseases
  • Nephrology
  • Oncology
  • Proctology
  • Pulmonology
  • Rheumatology
  • Neurology
  • Geriatrics

Generally, Pediatrics and Family Practice are also considered to fall under the category of “Medicine.”

Medical training, as opposed to surgical training, requires three years of residency training after medical school. This can then be followed by a one to two year fellowship in the subspecialties listed above. In general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week.

[edit] Diagnostic specialties

• Clinical laboratory sciences are the clinical diagnostic services which apply laboratory techniques to diagnosis and management of patients. In the United States these services are supervised by a pathologist. The personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. Subspecialties include Transfusion medicine, Cellular pathology, Clinical chemistry, Hematology, Clinical microbiology and Clinical immunology.
• Pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. As a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence-based medicine. Many modern molecular tests such as flow cytometry, polymerase chain reaction (PCR), immunohistochemistry, cytogenetics, gene rearragements studies and fluorescent in situ hybridization (FISH) fall within the territory of pathology.
• Radiology is concerned with imaging of the human body, e.g. by x-rays, x-ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography.
• Clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. These kinds of tests can be divided into recordings of: (1) spontaneous or continuously running electrical activity, or (2) stimulus evoked responses. Subspecialities include Electroencephalography, Electromyography, Evoked potential, Nerve conduction study and Polysomnography. Sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional.

[edit] Other

Following are some selected fields of medical specialties that don’t directly fit into any of the above mentioned groups.

• Ophthalmology exclusively concerned with the eye and ocular adnexa. Combines conservative and surgical therapy, and has its own College.
• Dermatology is concerned with the skin and its diseases. In the UK, dermatology is a subspeciality of general medicine.
• Emergency medicine is concerned with the diagnosis and treatment of acute or life-threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies.
• Obstetrics and gynaecology (often abbreviated as Ob/Gyn) are concerned respectively with childbirth and the female reproductive and associated organs. Reproductive medicine and fertility medicine are generally practiced by gynecological specialists.
• Palliative care is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal illnesses including cancer and heart failure.
• Pediatrics (AE) or paediatrics (BE) is devoted to the care of infants, children, and adolescents. Like internal medicine, there are many pediatric subspecialities for specific age ranges, organ systems, disease classes, and sites of care delivery.
• Physical medicine and rehabilitation (or physiatry) is concerned with functional improvement after injury, illness, or congenital disorders.
• Psychiatry is the branch of medicine concerned with the bio-psycho-social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. Related non-medical fields include psychotherapy and clinical psychology.

[edit] Interdisciplinary fields

Interdisciplinary sub-specialties of medicine are:

• General practice, family practice, family medicine or primary care is, in many countries, the first port-of-call for patients with non-emergency medical problems.
• Many other health science fields, e.g. dietetics
• Bioethics is a field of study which concerns the relationship between biology, science, medicine and ethics, philosophy and theology.
• Biomedical Engineering is a field dealing with the application of engineering principles to medical practice.
• Clinical pharmacology is concerned with how systems of therapeutics interact with patients.
• Conservation medicine studies the relationship between human and animal health, and environmental conditions. Also known as ecological medicine, environmental medicine, or medical geology.
• Disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management.
• Diving medicine (or hyperbaric medicine) is the prevention and treatment of diving-related problems.
• Evolutionary medicine is a perspective on medicine derived through applying evolutionary theory.
• Forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death.
• Gender-based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease.
• Hospital medicine is the general medical care of hospitalized patients. Physicians whose primary professional focus is hospital medicine are called hospitalists in the USA.
• Keraunomedicine is the medical study of lightning casualties.
• Medical humanities includes the humanities (literature, philosophy, ethics, history and religion), social science (anthropology, cultural studies, psychology, sociology), and the arts (literature, theater, film, and visual arts) and their application to medical education and practice.
• Medical informatics, medical computer science, medical information and eHealth are relatively recent fields that deal with the application of computers and information technology to medicine.
• Naturopathic medicine is concerned with primary care, natural remedies, patient education and disease prevention.
• Nosology is the classification of diseases for various purposes.
• Preventive medicine is the branch of medicine concerned with preventing disease.
  • Community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis.
  • Occupational medicine‘s principal role is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained.
  • Aerospace medicine deals with medical problems related to flying and space travel.
• Osteopathic medicine, a branch of the U.S. medical profession.
• Pharmacogenomics is a form of individualized medicine.
• Sports medicine deals with the treatment and preventive care of athletes, amateur and professional. The team includes specialty physicians and surgeons, athletic trainers, physical therapists, coaches, other personnel, and, of course, the athlete.
• Therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health [1].
• Travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments.
• Professions complementing physicians
  • Nursing specialties; Medical specialties performed by Nurses.
  • Mid-level Practitioners: Performance of medical sciences by other certified people than physicians or nurses; Nurse practitioners, midwives and physician assistants, treat patients and prescribe medication in many legal jurisdictions.
• Urgent care focuses on delivery of unscheduled, walk-in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department.
• Veterinary Medicine; Veterinarians apply similar techniques as physicians to the care of animals. The original focus of veterinary medicine was primarily the health care of domestic animals. In recent years the discipline has broadened to include all vertebrate animals and even some of the more economically valuable or scientifically interesting invertebrates. Veterinary and human medicine had similar origins but diverged in the West largely under the influence of Christian doctrine which emphasized a fundamental difference between humans and all other species. The two disciplines re-converged to some degree after the Renaissance when scientific study of anatomy and physiology revealed undeniable similarities between humans and other animals. The similarities further extend into pathology and disease control leading the early pioneer in scientific pathology Rudolph Virchow to proclaim the doctrine of “one medicine.”

[edit] Medical education

An image of a 1901 examination in the faculty of medicine.

Main articles: Medical education and Medical school

Medical education is education connected to the practice of being a medical practitioner, either the initial training to become a physician or further training thereafter.

Medical education and training varies considerably across the world, however typically involves entry level education at a university medical school, followed by a period of supervised practice (Internship and/or Residency) and possibly postgraduate vocational training. Continuing medical education is a requirement of many regulatory authorities.

Various teaching methodologies have been utilised in medical education, which is an active area of educational research.

Presently, in England, a typical medicine course at university is 5 years after secondary education (4 if the student already holds a degree). Amongst some institutions and for some students, it may be 6 years (including the selection of an intercalated BSc – taking one year – at some point after the pre-clinical studies). This is followed by 2 Foundation years afterwards, namely F1 and F2. Students register with the UK General Medical Council at the end of F1. At the end of F2, they may pursue further years of study.

In the US and Canada, a potential medical student must first complete an undergraduate degree in any subject before applying to a graduate medical school to pursue a (M.D. or D.O.) program. Some students opt for the research-focused MD/PhD dual degree, which is usually completed in 7-8 years. There are certain courses which are pre-requisite for being accepted to medical school, such as general chemistry, organic chemistry, physics, mathematics, biology, English, labwork, etc. The specific requirements vary by school.

In Australia, there are two pathways to a medical degree. Students can choose to take a five or six year undergraduate medical degree Bachelor of Medicine/Bachelor of Surgery (MBBS or BMed) straight from high school, or complete a bachelors degree (generally three years, usually in the medical sciences) and then apply for a four year graduate entry Bachelor of Medicine/Bachelor of Surgery (MBBS) program.

[edit] Legal restrictions

In most countries, it is a legal requirement for a medical doctor to be licensed or registered. In general, this entails a medical degree from a university and accreditation by a medical board or an equivalent national organization, which may ask the applicant to pass exams. This restricts the considerable legal authority of the medical profession to physicians that are trained and qualified by national standards. It is also intended as an assurance to patients and as a safeguard against charlatans that practice inadequate medicine for personal gain. While the laws generally require medical doctors to be trained in “evidence based”, Western, or Hippocratic Medicine, they are not intended to discourage different paradigms of health.

[edit] Criticism

Criticism of medicine has a long history. In the Middle Ages, some people did not consider it a profession suitable for Christians, as disease was often considered God-sent. God was considered to be the ‘divine physician’ who sent illness or healing depending on his will. However, many monastic orders, particularly the Benedictines, considered the care of the sick as their chief work of mercy. Barber-surgeons generally had a bad reputation that was not to improve until the development of academic surgery as a speciality of medicine, rather than an accessory field.^{[citation needed]}

Through the course of the twentieth century, healthcare providers focused increasingly on the technology that was enabling them to make dramatic improvements in patients’ health. The ensuing development of a more mechanistic, detached practice, with the perception of an attendant loss of patient-focused care, known as the medical model of health, led to further criticisms. This issue started to reach collective professional consciousness in the 1970s and the profession had begun to respond by the 1980s and 1990s.^{[citation needed]}

The noted anarchist Ivan Illich heavily criticized modern medicine. In his 1976 work Medical Nemesis, Illich stated that modern medicine only medicalises disease and causes loss of health and wellness, while generally failing to restore health by eliminating disease. This medicalisation of disease forces the human to become a lifelong patient.^[6] Other less radical philosophers have voiced similar views, but none were as virulent as Illich. Another example can be found in Technopoly: The Surrender of Culture to Technology by Neil Postman, 1992, which criticises overreliance on technological means in medicine.^{[citation needed]}

Criticism of modern medicine has led to some improvements in the curricula of medical schools,^{[citation needed]} which now teach students systematically on medical ethics, holistic approaches to medicine, the biopsychosocial model and similar concepts.

The inability of modern medicine to properly address some common complaints continues to prompt many people to seek support from alternative medicine. Although most alternative approaches lack scientific validation, some may be effective in individual cases. Some physicians combine alternative medicine with orthodox approaches.

Medical errors and overmedication are also the focus of many complaints and negative coverage. Practitioners of human factors engineering believe that there is much that medicine may usefully gain by emulating concepts in aviation safety, where it was long ago realized that it is dangerous to place too much responsibility on one “superhuman” individual and expect him or her not to make errors. Reporting systems and checking mechanisms are becoming more common in identifying sources of error and improving practice.