Asthma is characterized by a predisposition to chronic inflammation of the lungs in which the airways (bronchi) are reversibly narrowed. Asthma affects 7% of the population of the United States, 6.5% of British people and a total of 300 million worldwide. During asthma attacks (exacerbations of asthma), the smooth muscle cells in the bronchi constrict, the airways become inflamed and swollen, and breathing becomes difficult.
-
Asthma causes 4,000 deaths a year in the United States. Medicines such as inhaled short-acting beta-2 agonists may be used to treat acute attacks. Attacks can also be prevented by avoiding triggering factors such as allergens or rapid temperature changes and through drug treatment such as inhaled corticosteroids and then long-acting beta-2 agonists if necessary. Leukotriene antagonists are less effective than corticosteroids, but have no side effects. Monoclonal antibodies, such as mepolizumab and omalizumab, are sometimes effective. Prognosis is good with treatment.
In contrast to chronic obstructive pulmonary disease and chronic bronchitis, the inflammation of asthma is reversible. In contrast to emphysema, asthma affects the bronchi, not the alveoli.
The National Heart, Lung and Blood Institute defines asthma as a common chronic disorder of the airways characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness (bronchospasm), and an underlying inflammation.
Public attention in the developed world has recently focused on the predisposition because of its rapidly increasing prevalence, affecting up to one quarter of urban children.
Treatment
Perhaps the most important step in controlling asthma is establishing a partnership between doctor and patient (whether child or adult) to create a specific, customized plan for proactively monitoring and managing symptoms. It is essential to be certain that someone who has asthma understands (and takes an active part in deciding) what needs to be accomplished, including reducing exposure to allergens, taking medical tests to assess the severity of symptoms, and possibly using medications. The treatment plan should be written down, consulted at every visit, and adjusted according to changes in symptoms.
The most effective treatment for asthma is identifying triggers, such as pets or aspirin, and limiting or eliminating exposure to them. If trigger avoidance is insufficient, medical treatment is available. Desensitization has been suggested as a possible cure. Additionally, some trial subjects were able to remove their symptoms by retraining their breathing habits with the Buteyko method.[116]
Other forms of treatment include relief medication, prevention medication, long-acting β2-agonists, and emergency treatment.
Medical
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 (EPR-2) of the U.S. National Asthma Education and Prevention Program, and the British Guideline on the Management of Asthma are broadly used and supported by many doctors.
The Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma of the U.S. National Asthma Education and Prevention Program, released in 2007, presented a focused 6-step approach to asthma management, based on four principles that act as a blueprint to guide individualized treatment:
* Frequent and regular assessment of symptoms
* Patient education
* Control of environmental triggers
* Systematic evaluation of the effectiveness and safety of medications.
The 2007 revised NAEPP guidelines differ from the earlier version in an increased focus on asthma control and individualized treatment, reorganizing the goals of treatment to differentiate risk from impairment. They specify defined measures that should prompt a decision to "step up" or "step down" the intensity of treatment, and they emphasize education and integrated decision-making to encourage patient self-management.
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 β-2 agonist may be prescribed; alternatively, a leukotriene modifier or theophylline may substitute for the β-2 agonist. In severe asthma, oral glucocorticoids may be added to these treatments during severe attacks.
Pharmaceutical agents
Symptomatic control of episodes of wheezing and shortness of breath is generally achieved with fast-acting bronchodilators. These are typically provided in pocket-sized, metered-dose inhalers (MDIs). In young sufferers, who may have difficulty with the coordination necessary to use inhalers, or those with a poor ability to hold their breath for 10 seconds after inhaler use (generally the elderly), an asthma spacer (see top image) is used. The spacer is a plastic cylinder that mixes the medication with air in a simple tube, making it easier for patients to receive a full dose of the drug and allows for the active agent to be dispersed into smaller, more fully inhaled bits.
A nebulizer which provides a larger, continuous dose can also be used. Nebulizers work by vaporizing a dose of medication in a saline solution into a steady stream of foggy vapour, which the patient inhales continuously until the full dosage is administered. There is no clear evidence, however, that they are more effective than inhalers used with a spacer. Nebulizers may be helpful to some patients experiencing a severe attack. Such patients may not be able to inhale deeply, so regular inhalers may not deliver medication deeply into the lungs, even on repeated attempts. Since a nebulizer delivers the medication continuously, it is thought that the first few inhalations may relax the airways enough to allow the following inhalations to draw in more medication.
Relievers include:
* Short-acting, selective beta2-adrenoceptor agonists, such as salbutamol (albuterol USAN), levalbuterol, terbutaline and bitolterol.
Tremors, the major side effect, have been greatly reduced by inhaled delivery, which allows the drug to target the lungs specifically; oral and injected medications are delivered throughout the body. There may also be cardiac side effects at higher doses (due to Beta-1 agonist activity), such as elevated heart rate or blood pressure. However, levalbuterol has been shown to have less cardiac side effects and significantly more anti-inflammatory effects on bronchial smooth muscle than its racemic counterpart albuterol. The question becomes does this justify its 5-10 fold higher cost. Some hospitals start a patient on levalbuterol until symptoms wane and then switch to albuterol. Patients must be cautioned against using these medicines too frequently, as with such use their efficacy may decline, producing desensitization resulting in an exacerbation of symptoms which may lead to refractory asthma and death.
* Older, less selective adrenergic agonists, such as inhaled epinephrine and ephedrine tablets, have also been used. Cardiac side effects occur with these agents at either similar or lesser rates to albuterol. When used solely as a relief medication, inhaled epinephrine has been shown to be an effective agent to terminate an acute asthmatic exacerbation. In emergencies, these drugs were sometimes administered by injection. Their use via injection has declined due to related adverse effects.
* Anticholinergic medications, such as ipratropium bromide may be used instead. They have no cardiac side effects and thus can be used in patients with heart disease; however, they take up to an hour to achieve their full effect and are not as powerful as the β2-adrenoreceptor agonists.
* Inhaled glucocorticoids are usually considered preventive medications while oral glucocorticoids are often used to supplement treatment of a severe attack. They should be used twice daily in children with mild to moderate persistent asthma. A randomized controlled trial has demonstrated the benefit of 250 microg beclomethasone when taken as an as-needed combination inhaler with 100 microg of albuterol.
Emergency
When an asthma attack is unresponsive to a patient's usual medication, other treatment options available for emergency management include:
* Oxygen to alleviate the hypoxia that results from extreme asthma attacks (but not the asthma attack itself).
* Nebulized salbutamol or terbutaline (short-acting beta-2-agonists), often combined with ipratropium (an anticholinergic).
* Systemic steroids, oral or intravenous (prednisone, prednisolone, methylprednisolone, dexamethasone, or hydrocortisone). Some research has looked into an alternative inhaled route.
* Other bronchodilators that are occasionally effective when the usual drugs fail:
o Intravenous salbutamol
o Nonspecific beta-agonists, injected or inhaled (epinephrine, isoetharine, isoproterenol, metaproterenol)
o Anticholinergics, IV or nebulized, with systemic effects (glycopyrrolate, atropine, ipratropium)
o Methylxanthines (theophylline, aminophylline)
o Inhalation anesthetics that have a bronchodilatory effect (isoflurane, halothane, enflurane)
o The dissociative anaesthetic ketamine, often used in endotracheal tube induction
o Magnesium sulfate, intravenous
* Intubation and mechanical ventilation, for patients in or approaching respiratory arrest.
* Heliox, a mixture of helium and oxygen, may be used in a hospital setting. It has a more laminar flow than ambient air and moves more easily through constricted airways.
Non-medical treatments
Many asthma patients, like those who suffer from other chronic disorders, use alternative treatments; surveys show that roughly 50% of asthma patients use some form of unconventional therapy. There is little data to support the effectiveness of most of these therapies. However, the Buteyko method of controlling hyperventilation hypocapnia has shown in five randomized controlled trials to result in a significant reduction in need for medications without an effect on bronchial hyperreactivity or lung function. In May 2008 the updated British Guidelines for the Management of Asthma endorsed Buteyko Technique. A Cochrane systematic review of acupuncture for asthma found no evidence of efficacy. A similar review of air ionisers found no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators. Another systematic study reviewed a range of dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others. Overall these methods had no effect on asthma symptoms. A study of "manual therapies" for asthma, including osteopathic, chiropractic, physiotherapeutic and respiratory therapeutic manoeuvres, found there is insufficient evidence to support or refute their use in treating asthma; these manoeuvers include various osteopathic and chiropractic techniques to "increase movement in the rib cage and the spine to try and improve the working of the lungs and circulation"; chest tapping, shaking, vibration, and the use of "postures to help shift and cough up phlegm." One meta-analysis finds that homeopathy may have a potentially mild benefit in reducing the intensity of symptoms. However, the number of patients involved in the analysis was small, and subsequent studies have not supported this finding. Several small trials have suggested some benefit from various yoga practices, ranging from integrated yoga programs, yogasanas, Pranayama, meditation, and kriyas, to Sahaja yoga, a form of 'new religious' meditation.
Подписаться на:
Комментарии к сообщению (Atom)
Комментариев нет:
Отправить комментарий