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EXERCISE-INDUCED ASTHMA: FRESH INSIGHTS AND AN OVERVIEW

DIAGNOSIS

EIA is invariably diagnosed by the medical history. Atopic individuals with or without asthma should be questioned regarding possible EIA symptoms. Persons who give a history of cough, wheezing, dyspnoea, chest pain or chest tightness following aerobic activity should be questioned in detail regarding other symptoms related to EIA. Children who cannot keep pace with their peers during sporting activities should be asked whether breathing becomes difficult during those activities.

EIA is best detected by a free-run challenge test. Here, the patient is asked to run at full speed for 3-5 minutes and achieving a heart rate at least two-thirds of their target heart rate (or 180 beats per minute in children). The patient should stop after 5 minutes or earlier if symptoms arise. Pulmonary function should be measured by PEFR and FEV1 at baseline, immediately after stopping the run and at 5, 10, 15, 20 and 30 minutes after the activity is completed. A decrease of 15% in FEV1 and PEFR is diagnostic of EIA. Sensitivity of exercise testing ranges from 55% to 80%, and specificity is approximately 93%.²

It must be remembered however, that testing is contraindicated during acute exacerbations of asthmatic attacks.

TREATMENT MODALITIES

EIA has several treatment modalities. The aim of treatment should always be to help maximise the patients ability to participate in aerobic activity be it at his work place, recreation, serious athletics or school-related activities. The purpose of treatment in EIA is to enhance the patients’ sense of self worth, physical conditioning, socialization and sometimes even to help retain employment.

Can EIA be successfully treated? YES!!

The 1988 US Olympic team included 67 members (of 597) affected with EIA. These athletes won 15 gold, 21 silver and 5 bronze medals in multiple sporting events including long–distance running.

Non-pharmacological treatment

Medication is not the only way to treat EIA but type of physical activity undertaken is also very important. Clinicians should encourage patients to choose less asthmogenic activities whenever possible. Ambient conditions should also be considered – the more humid and warmer the air, the less the chance of provoking EIA. Thus indoor activities are less likely to provoke an attack of EIA. Wearing a face mask may also help to warm and humidify the outdoor air. Physical activity on days of high air pollution should be avoided. For asthmatic patients who are highly sensitive to pollen, activity should be timed to occur when diurnal pollen counts are lowest.

The refractory period may also be used beneficially by encouraging athletes to exercise in several 2-3 minute increments as “warm ups”, 10-20 minutes before the main event. As a result this may induce a period of up to one hour during which EIA would not develop. This would certainly help those whose duration of planned physical activity is short such as sprinters.

Pharmacological treatment

Many factors play a role while initiating treatment:

• Does the patient have predictable periods of aerobic activity (e.g. jogs every morning, is a day labourer, or is a playful 5-year-old child).
• Are the ambient conditions in which activity takes place controllable?
• Can the patient effectively use a metered-dose inhaler?
• How long will the physical activity continue and how intense aerobically is the physical activity?

In general, drug therapy is effective for patients whose physical activity is brief and predictable and who can use the metered-dose inhaler effectively. However, if physical activity continues for more than 2-3 hours or if the patient cannot use a metered-dose inhaler effectively, consideration of oral medication may be warranted.

Treatment is chosen from three types of medication: beta-adrenergic drugs, mast cell inhibitors and leukotriene antagonists. Beta-adrenergic drugs are the first-choice medication for treating patients whose activity is limited in duration i.e. less than 3 hours. These drugs can be used 15 minutes before activity is begun and are relatively safe. Since bronchospasm is the main component of EIA, these drugs are highly effective. Salbutamol and terbutaline are most commonly used. Recent data indicate that salmeterol remains effective for 10-12 hours.¹¹ Clinicians should emphasize to patients that salmeterol dosing should never be repeated more frequently than every 12 hours because overuse can induce cardiac toxicity. Oral beta-adrenergic agents may also be used but must be taken at least 30-45 minutes before the activity is begun. Beta-adrenergic agents may cause more side-effects when taken orally than when they are administered by metered-dose inhalers.

Another group of medications used in the treatment of EIA are called the mast cell inhibitors, but whether inhibition of mast cells is their primary role is unclear. They are a very good choice for preventing EIA and they have an excellent safety profile. Among them cromolyn and nedocromil also have the twin advantage of blocking early-phase and late-phase responses. These drugs are delivered by metered–dose inhalers, 2-3 sprays being administered 10-15 minutes before the onset of activity. They are also usually needed after 2-4 hours of continuous activity.  

Leukotriene antagonists constitute the third group of medications used in the treatment of EIA. Of this group, montelukast (Singulair) is effective in preventing EIA. It has been observed that long-term use (longer than 12 weeks) is not associated with shortened duration of action or with diminution in protection offered as measured by FEV1.¹² The medication is given orally in tablet form in a single dose each day. However, montelukast is not approved for children less than 6 years of age.

Other medications such as inhaled steroids have been used to decrease airway hyperreactivity. For this, a month or more of moderate-to-high dose daily use may be required. These drugs are best reserved for use in controlling asthma that is not specifically related to exercise. Theophylline can also be used and may be beneficial, but timing its use to activity is more difficult.  Overall, medications benefit 60-80% of patients who are susceptible to EIA and reduce the decrease in FEV1 in these patients from 40-80%.¹²

Athletic activities and EIA

Diagnosis and treatment of athletes who participate in competitive sporting activities is essentially the same as for other people except that competitive athletes tend to recognise even small changes in airway function, and this small amount of change may not respond noticeably to medication therapy. In addition, the degree of response achieved by using these medications may not warrant use of the large amounts of medication needed to relieve all symptoms. This fact needs to be discussed carefully with each affected athlete.

In addition, athletes in competition are also likely to behave stoically when experiencing physical discomfort and thus may underreport symptoms. This may be due to peer pressure, embarrassment, fear of losing position on the team, or plain misinterpretation as post-exercise fatigue.

CONCLUSION

EIA is a common problem that affects millions of people annually all over the world. It is often unrecognised by patients and physicians. However, a high index of suspicion and some simple screening methods can lead to a presumptive diagnosis in most cases. EIA is treated both, by pharmacological and non-pharmacological means. Most important, control of any underlying asthma is essential for control of EIA.

The importance of recognising and treating EIA therefore cannot be over-emphasised if we hope to provide all affected persons with the opportunity for better overall health, better social life and better self-image.

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