Highlights
New Asthma Guidelines Released
In 2007, the U.S. National Asthma Education and Prevention Program (NAEPP) released updated guidelines for the diagnosis and management of asthma. The new guidelines are the first to be released in a decade. Key points include:
- Assessment and Monitoring. Doctors should use multiple measures to determine a patients current condition and future risk for worsening of condition. Even patients who show few daily effects of asthma may be in danger of sudden worsening of symptoms.
- Patient Education. Patients should be taught skills to self-monitor and manage asthma. Doctors should give patients a written asthma action plan, which includes information on daily treatment and ways to recognize worsening asthma.
- Control of Environmental Factors and Other Asthma Triggers. The guidelines outline new approaches for reducing exposure to allergens. They also address how treating co-existing chronic conditions (rhinitis, sinusitis, gastroesophageal reflux, obesity) can help improve asthma control.
- Medications. A stepwise approach is recommended where medication types and doses are increased or decreased based on the level of asthma control.
New Inhaled Corticosteroid Approved
In January 2008, the Food and Drug Administration (FDA) approved ciclesonide (Alvesco), a new inhaled corticosteroid drug, for patients ages 12 years and older.
Introduction
The word asthma originates from an ancient Greek word meaning panting. Essentially, asthma is an inability to breathe properly. When any person inhales, the air travels through the following structures:
- Air passes into the lungs and flows through progressively smaller airways called bronchioles. The lungs contain millions of these airways.
- All bronchioles lead to alveoli, which are microscopic sacs where oxygen and carbon dioxide are exchanged.
Asthma is a chronic condition in which these airways undergo changes when stimulated by allergens or other environmental triggers. Such changes appear to be two specific responses:
- The hyperreactive response (also called hyperresponsiveness)
- The inflammatory response
These actions in the airway cause coughing, wheezing, and shortness of breath (dyspnea), the classic symptoms of asthma.
Hyperreactive Response
In the hyperreactive response, smooth muscles in the airways of the lungs constrict and narrow excessively in response to inhaled allergens or other irritants. Everyone's airways respond by constricting when exposed to allergens or irritants, but a special hyperreactive response occurs in people with asthma:
- When people without asthma breathe in and out deeply, the airways relax and open to rid the lungs of the irritant.
- When people with asthma try to take those same deep breaths, their airways do not relax and narrow, causing patients to pant for breath. Smooth muscles in the airways of people with asthma may have a defect, perhaps a deficiency in a critical chemical that prevents the muscles from relaxing.
Inflammatory Response
The hyperreactive stage is followed by the inflammatory response, which generally contributes to asthma in the following way:
- In response to allergens or other environmental triggers, the immune system delivers white blood cells and other immune factors to the airways.
- These so-called inflammatory factors cause the airways to swell, to fill with fluid, and to produce a thick sticky mucus.
- This combination results in wheezing, breathlessness, an inability to exhale properly, and a phlegm-producing cough.
Click the icon to see an image of a normal bronchiole versus an asthmatic bronchiole.
Inflammation appears to be present in the lungs of all patients with asthma, even those with mild cases, and plays a key role in all forms of the disease.
Symptoms
Asthma symptoms vary in severity from occasional mild bouts of breathlessness to daily wheezing that lasts even when a patient takes large doses of medication. After exposure to asthma triggers, symptoms rarely develop abruptly but progress over a period of hours or days. Occasionally, the airways have become seriously obstructed by the time the patient calls the doctor.
The classic symptoms of an asthma attack include:
- Wheezing when breathing out is nearly always present during an attack. Usually the attack begins with wheezing and rapid breathing, and, as it becomes more severe, all breathing muscles become visibly active.
- Shortness of breath (dyspnea). Shortness of breath is a major source of distress in patients with asthma. However, the severity of this symptom does not always reflect the degree to which lung function is impaired. Some patients are not even aware that they are experiencing shortness of breath. These patients are at particular risk for very serious and even life-threatening asthma attacks, since they are less conscious of symptoms. Those at highest risk for this effect tend to be older, female, and to have had the disease for a longer period of time.
- Coughing. In some people, the first symptom of asthma is a nonproductive cough. Some patients find this cough even more distressing than wheezing or sleep disturbances.
- Chest tightness or pain. Initial chest tightness without any other symptoms may be an early indicator of a serious attack.
- Rapid heart rate
- Sweating
The end of an attack is often marked by a cough that produces thick, stringy mucus. After an initial acute attack, inflammation lasts for days to weeks, often without symptoms. (The inflammation itself must still be treated, however, because it usually causes relapse.)
Symptoms of a Life-Threatening Attack
The following signs and symptoms may indicate a life-threatening situation:
- As the chest labors to bring enough air into the lungs, breathing often becomes shallow.
- Lacking enough oxygen, the skin becomes bluish.
- The flesh around the ribs of the chest appears to be sucked in.
- The patient may begin to lose consciousness.
Asthma often progresses very slowly to a serious condition or may develop to a fatal or near-fatal attack within a few minutes. It is very difficult to predict when an attack will become very serious.
Early symptoms or lack thereof do not always reflect the ultimate severity of an attack. In fact, some studies suggest that people at high risk for fatal or near-fatal asthma attacks are those with poor awareness of their own reduced ability to breathe and who are therefore slow in seeking help. Those at highest risk for this effect tend to be older, female, and have had the disease for a longer period of time. Monitoring peak flow rates is an important management component since it provides a more accurate assessment of lung function than symptoms alone.
Exercise-Induced Asthma
Exercise-induced asthma (EIA) is a limited form of asthma in which exercise triggers coughing, wheezing, or shortness of breath. This condition generally occurs in children and young adults, most often during intense exercise in cold dry air. Symptoms are generally most intense about 10 minutes after exercising and then gradually resolve.
EIA is triggered only by exercise and is distinct from ordinary allergic asthma in that it does not produce a long duration of airway activity, as allergic asthma does. (However, some people have both forms of asthma.) People who have only EIA do not appear to need long-term maintenance therapy.
Nocturnal Asthma
Asthma occurs primarily at night (nocturnal asthma) in as many as 75% of patients with asthma. Attacks often occur between 2 and 4 a.m. Some experts believe that nocturnal asthma may actually be a unique form, with its own specific biologic mechanisms occuirng only at night and reducing natural steroid hormones (which block inflammation).
Causes
Asthma has dramatically risen worldwide over the past decades, particularly in developed countries, and experts are puzzled over the cause of this increase. The mechanisms that cause asthma are complex and vary among population groups and even from individual to individual. Many asthma sufferers have allergies, and some researchers are targeting common factors in both these conditions. Not all people with allergies have asthma, however, and asthma is not always due to an allergic response.
Asthma is most likely caused by a several factors that can include genes and environmental and biologic triggers (such as infections, dietary patterns, hormonal changes in women, and allergens).
The Allergic Response
Nearly half of adults with asthma have an allergy-related condition, which, in most cases developed first in childhood. (In patients who first develop asthma during adulthood, the allergic response usually does not play a strong causal role.)
The Allergic Process. The allergic process, called atopy, and its connection to asthma are not completely understood. The process involves various airborne allergens, or other triggers, that set off a cascade of events in the immune system, leading to inflammation and hyperreactivity in the airways. Here is an example of the allergic process:
- The conductor in an orchestra of immune factors that contribute to allergies and asthma appears to be a category of white blood cells known as helper T cells, in particular a subgroup called Th2 cells.
- Th2 cells overproduce interleukins (ILs), immune factors that are molecular members of a family called cytokines, which are involved in the inflammatory process.
- During an allergic attack, these IgE antibodies can bind to special cells in the immune system called mast cells, which are concentrated in the lungs, skin, and mucous membranes. This bond triggers the release of several active chemicals, importantly potent molecules known as leukotrienes. These chemicals cause airway spasms, overproduce mucus, and activate nerve endings in the airway lining.
- One specific cytokine, interleukin 5, attracts white blood cells known as eosinophils. These cells accumulate and remain in the airways after the first attack. They persist for weeks and mediate the release of other damaging particles that remain in the airways.
Over several years, the repetition of the inflammatory events involved in asthma can cause irreversible structural and functional changes in the airways, a process called remodeling. The remodeled airways are persistently narrow and can cause chronic asthma. Researchers are trying to determine how this process occurs:
- Interleukins. Some researchers are looking at potent immune factors, including interleukins 11 and 13. They have been linked to a number of processes possibly involved in remodeling, including scarring in the airways and overgrowth of cells in the smooth muscles that line the airways.
- Growth Factors. Compounds known as vascular endothelial growth factor (VEGF) have been observed in the airways of patients with asthma. VEGF is a powerful promoter of cell growth in blood vessel linings, and some researchers believe it may be major factor in remodeling.
Environmental Factors
An asthma attack can be induced or aggravated by direct irritants to the lungs. Studies indicate that the more indoor allergens a child is allergic to, the higher the risk for severe asthma. Important irritants or allergens include:
- Dust mites, specifically mite feces, which are coated with enzymes that contain a powerful allergen. These are the primary allergens in the home.
- Animal dander. Cats harbor significant allergens, which can even be carried on clothing; dogs usually cause fewer problems. People with asthma who already have pets and are not allergic to them probably have a low risk for developing allergies later on.
- Smoking, or exposure to secondhand smoke
- Pollen. An asthma attack from an allergic response to pollen is more likely to occur during extreme air changes, such as thunderstorms. Major weather changes, such as El Nino, can affect the timing of allergy seasons. For example, in 1998, when the effects of El Nino were very strong, allergy and asthma attacks occurred earlier and were markedly increased.
- Molds might produce a worse asthma attack in adults than other allergens.
- Fungi
- Cockroaches. Cockroaches are major asthma triggers and may reduce lung function even in people without a history of asthma.
- Fossil Fuels. Certain chemicals may trigger allergic rhinitis. Some experts believe that refined fossil fuels, such as diesel fuel and particularly kerosene, may be important triggers for allergic rhinitis. And, in people who already have allergies or asthma, exposure to such fossil fuels may worsen symptoms.
Genetic Factors
About one-third of all persons with asthma share this condition with another member of their immediate family. Asthma may be more likely to pass to children from their mother than from their father. Both allergies and asthma are strongly associated with hereditary factors, sharing certain genetic markers, but they are not always inherited together.
Research on the genetics of these conditions is confusing. Of some significant promise, researchers have identified a gene (ADAM33), which has been linked to asthma. The gene regulates one of the enzymes called metalloproteases, which are involved with the smooth muscle in the airway. A mutation of this gene could play a role in airway changes that occur after inflammation.
Treatment
General Approach for Treating and Managing Asthma
While medications play an essential role in the management of asthma, appropriate management of asthma involves much more:
- Identifying and avoiding allergens and other asthma triggers
- Following appropriate drug treatments
- Home monitoring performed by either patient or family
- Good communication between the doctor and patient
- Needed psychosocial support
- Treatment of asthma in all environments (school, work, exercise)
The severity of asthma has now been classified into four groupings: Intermittent, Mild Persistent, Moderate Persistent, and Severe Persistent. Six specific components of severity are used to classify patients. These components are:
- Symptom frequency, ranging from fewer than 2 days per week to throughout the day
- Nighttime awakenings, ranging from none to nightly
- Short-acting beta2-agonist use for symptom control, ranging from 2 or fewer days per week to several times per day
- Interference with normal activity, ranging from none to extremely limited
- Lung function as measured by FEV1 and FEV1/FVC, measured with pulmonary function testing at the doctor's office
- Number of exacerbations (sudden worsening) requiring oral corticosteroids, ranging from none to two or more in the last 6 months
Treating Symptoms Versus Controlling the Disease
Patients can greatly reduce the frequency and severity of asthma attacks by understanding the difference between coping with asthma attacks and controlling the disease over time.
Medications for asthma fall into two categories:
- Rescue (Quick-Relief) Medication. Medications that open the airways (bronchodilators, or inhalers) are used to quickly relieve any moderate or severe asthma attack. These drugs are usually short-acting beta-adrenergic agonists (beta2-agonists). Other drugs used in special cases include corticosteroids taken by mouth and anticholinergic drugs. Beta2-agonists and anticholinergics do not have any effect on the disease process itself. They are only useful for treating symptoms.
- Long-Term Control (Maintenance) Medication. Simply coping with asthma symptoms without also controlling the damaging inflammatory response is a common and serious error. For adults and children over age 5 with moderate-to-severe persistent asthma, experts now recommend inhaled corticosteroids and long-acting beta2-agonists.
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