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Asthma |
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An asthma is a chronic disease of the respiratory system in which the airway occasionally constricts, becomes inflamed, and is lined with excessive amounts of mucus, often in response to one or more triggers. These episodes may be triggered by such things as exposure to an environmental stimulant (or allergen), cold air, warm air, moist air, exercise or exertion, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold. This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. The airway constriction responds to bronchodilators. Between episodes, most patients feel well but can have mild symptoms and they may remain short of breath after exercise for longer periods of time than the unaffected individual. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and environmental changes. |
History |
| The word 'asthma' is derived from the Greek aazein, meaning "sharp breath." The word first appears in Homer's Iliad;[3] Hippocrates was the first to use it in reference to the medical condition, in 450 BC. Hippocrates thought that the spasms associated with asthma were more likely to occur in tailors, anglers, and metalworkers. Six centuries later, Galen wrote much about asthma, noting that it was caused by partial or complete bronchial obstruction. In 1190 AD, Moses Maimonides, an influential medieval rabbi, philosopher, and physician, wrote a treatise on asthma, describing its prevention, diagnosis, and treatment.[4] In the 17th century, Bernardino Ramazzini noted a connection between asthma and organic dust. The use of bronchodilators started in 1901, but it was not until the 1960s that the inflammatory component of asthma was recognized, and anti-inflammatory medications were added to the regimens.
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Signs and symptoms |
In some individuals asthma is characterized by chronic respiratory impairment. In others it is an intermittent illness marked by episodic symptoms that may result from a number of triggering events, including upper respiratory infection, stress, airborne allergens, air pollutants (such as smoke or traffic fumes), or exercise. Some or all of the following symptoms may be present in those with asthma: dyspnea, wheezing, stridor, coughing, an inability for physical exertion. Some asthmatics that have severe shortness of breath and tightening of the lungs never wheeze or have stridor and their symptoms may be confused with a COPD-type disease.
An acute exacerbation of asthma is referred to as an asthma attack. The clinical hallmarks of an attack are shortness of breath (dyspnea) and either wheezing or stridor.[5] Although the former is "often regarded as the sine qua non of asthma,[5] some patients present primarily with coughing, and in the late stages of an attack, air motion may be so impaired that no wheezing may be heard. When present the cough may sometimes produce clear sputum. The onset may be sudden, with a sense of constriction in the chest, breathing becomes difficult, and wheezing occurs (primarily upon expiration, but can be in both respiratory phases). An asthma attack may spread the mold to others through the air.
Signs of an asthmatic episode include wheezing, rapid breathing (tachypnea), prolonged expiration, a rapid heart rate (tachycardia), rhonchous lung sounds (audible through a stethoscope), and over-inflation of the chest. During a serious asthma attack, the accessory muscles of respiration (sternocleidomastoid and scalene muscles of the neck) may be used, shown as in-drawing of tissues between the ribs and above the sternum and clavicles, and the presence of a paradoxical pulse (a pulse that is weaker during inhalation and stronger during exhalation).
During very severe attacks, an asthma sufferer can turn blue from lack of oxygen, and can experience chest pain or even loss of consciousness. Just before loss of consciousness, there is a chance that the patient will feel numbness in the limbs and palms may start to sweat. Feet may become icy cold. Severe asthma attacks, which may not be responsive to standard treatments (status asthmaticus), are life-threatening and may lead to respiratory arrest and death. Despite the severity of symptoms during an asthmatic episode, between attacks an asthmatic may show few signs of the disease
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Diagnosis |
Asthma is defined simply as reversible airway obstruction. Reversibility occurs either spontaneously or with treatment. The basic measurement is peak flow rates and the following diagnostic criteria are used by the British Thoracic Society:
* =20% difference on at least three days in a week for at least two weeks;
* =20% improvement of peak flow following treatment, for example:
o 10 minutes of inhaled ß-agonist (e.g., salbutamol);
o six week of inhaled corticosteroid (e.g., beclometasone);
o 14 days of 30mg prednisolone.
* =20% decrease in peak flow following exposure to a trigger (e.g., exercise).
In many cases, a physician can diagnose asthma on the basis of typical findings in a patient's clinical history and examination. Asthma is strongly suspected if a patient suffers from eczema or other allergic conditions—suggesting a general atopic constitution—or has a family history of asthma. While measurement of airway function is possible for adults, most new cases are diagnosed in children who are unable to perform such tests. Diagnosis in children is based on a careful compilation and analysis of the patient's medical history and subsequent improvement with an inhaled bronchodilator medication. In adults, diagnosis can be made with a peak flow meter (which tests airway restriction), looking at both the diurnal variation and any reversibility following inhaled bronchodilator medication.
Testing peak flow at rest (or baseline) and after exercise can be helpful, especially in young asthmatics who may experience only exercise-induced asthma. If the diagnosis is in doubt, a more formal lung function test may be conducted. Once a diagnosis of asthma is made, a patient can use peak flow meter testing to monitor the severity of the disease.
In the Emergency Department doctors may use a capnography PMID 16187465 which measures the amount of exhaled carbon dioxide along with pulse oximetry which shows the amount of oxygen dissolved in the blood, to determine the severity of an asthma attack as well as the response to treatment.
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Differential diagnosis |
Before diagnosing someone as asthmatic, alternative possibilities should be considered. A clinician taking a history should check whether the patient is using any known bronchoconstrictors (substances that cause narrowing of the airways, e.g., certain anti-inflammatory agents or beta-blockers).
Chronic obstructive pulmonary disease, which closely resembles asthma, is correlated with more exposure to cigarette smoke, an older patient, less symptom reversibility after bronchodilator administration (as measured by spirometry), and decreased likelihood of family history of atopy.
Pulmonary aspiration, whether direct due to dysphagia (swallowing disorder) or indirect (due to acid reflux), can show similar symptoms to asthma. However, with aspiration, fevers might also indicate aspiration pneumonia. Direct aspiration (dysphagia) can be diagnosed by performing a Modified Barium Swallow test and treated with feeding therapy by a qualified speech therapist. If the aspiration is indirect (from acid reflux) then treatment directed at this is indicated.
A majority of children who are asthma sufferers have an identifiable allergy trigger. Specifically, in a 2004 study, 71% had positive test results for more than 1 allergen, and 42% had positive test results for more than 3 allergens.
The majority of these triggers can often be identified from the history; for instance, asthmatics with hay fever or pollen allergy will have seasonal symptoms, those with allergies to pets may experience an abatement of symptoms when away from home, and those with occupational asthma may improve during leave from work. Occasionally, allergy tests are warranted and, if positive, may help in identifying avoidable symptom triggers.
After a pulmonary function test has been carried out, radiological tests, such as a chest X-ray or CT scan, may be required to exclude the possibility of other lung diseases. In some people, asthma may be triggered by gastroesophageal reflux disease, which can be treated with suitable antacids. Very occasionally, specialized tests after inhalation of methacholine — or, even less commonly, histamine — may be performed.
Asthma is categorized by the United States National Heart, Lung and Blood Institute as falling into one of four categories: mild intermittent, mild persistent, moderate persistent and severe persistent. The diagnosis of "severe persistent asthma" occurs when symptoms are continual with frequent exacerbations and frequent nighttime symptoms, result in limited physical activity and when lung function as measured by PEV or FEV1 tests is less than 60% predicted with PEF variability greater than 30%.
There is no cure for asthma. Doctors have only found ways to prevent attacks and relieve the symptoms such as tightness of the chest and trouble breathing.
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Treatment |
The most effective treatment for asthma is identifying triggers, such as pets or aspirin, and limiting or eliminating exposure to them. Desensitization to allergens has been shown to be a treatment option for certain patients.
As is common with respiratory disease, smoking is believed to adversely affect asthmatics in several ways, including an increased severity of symptoms, a more rapid decline of lung function, and decreased response to preventive medications.[33] Automobile emissions are considered an even more significant cause and aggravating factor. Asthmatics who smoke or who live near traffic[4] typically require additional medications to help control their disease. Furthermore, exposure of both non-smokers and smokers to wood smoke, gas stove fumes and second-hand smoke is detrimental, resulting in more severe asthma, more emergency room visits, and more asthma-related hospital admissions. Smoking cessation and avoidance of second-hand smoke is strongly encouraged in asthmatics.
The specific medical treatment recommended to patients with asthma depends on the severity of their illness and the frequency of their symptoms. Specific treatments for asthma are broadly classified as relievers, preventers and emergency treatment. The Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma of the U.S. National Asthma Education and Prevention Program, and the British Guideline on the Management of Asthma[36] are broadly used and supported by many doctors. A new draft Full Report of Expert Panel: Guidelines for the Diagnosis and Management of Asthma (EPR-3) was posted on the NHLBI web site for public review and comment but has been withdrawn from the NIH website pending formal dissemination, although comments submitted by the American College of Allergy, Asthma and Immunology about the proposed revised NHLBI asthma guidelines are still available online. Bronchodilators are recommended for short-term relief in all patients. For those who experience occasional attacks, no other medication is needed. For those with mild persistent disease (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene modifier, a mast-cell stabilizer, or theophylline may be administered. For those who suffer daily attacks, a higher dose of glucocorticoid in conjunction with a long-acting inhaled ß-2 agonist may be prescribed; alternatively, a leukotriene modifier or theophylline may substitute for the ß-2 agonist. In severe asthmatics, oral glucocorticoids may be added to these treatments during severe attacks.
For those in whom exercise can trigger an asthma attack (exercise-induced asthma), higher levels of ventilation and cold, dry air tend to exacerbate attacks. For this reason, activities in which a patient breathes large amounts of cold air, such as skiing and running, tend to be worse for asthmatics, whereas swimming in an indoor, heated pool, with warm, humid air, is less likely to provoke a response.
Researchers at Harvard Medical School (HMS) have come up with convincing evidence that the answer to what causes asthma lies in a special type of natural "killer" cell. This finding means that physicians may not be treating asthma sufferers with the right kinds of drugs. For example, natural killer T cells seem to be resistant to the corticosteroids in widely used inhalers
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