Exercise-Induced Bronchoconstriction

Chapter 41

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Exercise-Induced Bronchoconstriction

BreAnna Kinghorn, MD

Introduction/Etiology/Epidemiology

Exercise-induced bronchoconstriction (EIB) involves acute, transient airway narrowing that occurs during and after exercise.

EIB is most often defined by ≥10% decline in forced expiratory volume in 1 second (FEV1) at spirometry after exercise provocation.

EIB occurs in 90% of individuals with asthma.

EIB also can occur in individuals without a known diagnosis of asthma.

Prevalence of EIB is higher in the competitive athlete population (30%–70%) than the nonathlete population (≤10%).

Pathophysiology

Breathing dry and/or cold air causes airway narrowing via osmotic and thermal consequences of evaporative water loss from the airway surface.

Dry or cold air in the distal airways causes hyperemia of bronchial vasculature and airway edema, which further causes airway narrowing.

Airway narrowing causes cough.

Although the events that trigger EIB and the role of inflammatory cells are not fully understood, a hyperosmolar environment is thought to trigger the release of inflammatory mediators, including histamine, tryptase, and leukotrienes from eosinophils and mast cells.

Several studies have demonstrated that individuals who are prone to EIB have increased levels of exhaled nitric oxide, increased airway leukotriene levels, greater expression of mast cell genes, and/or peripheral eosinophilia.

Clinical Features

Clinical manifestations can range from mild impairment to severe bronchospasm and, rarely, respiratory failure.

Symptoms include coughing, wheezing, chest tightness, and dyspnea.

More subtle symptoms include fatigue, abdominal discomfort, poor performance, and avoidance of activities.

Exercise duration for a minimum of 5–8 minutes at 80% of maximum predicted oxygen consumption typically generates bronchospasm.

Symptoms peak 5–10 minutes after exercise ceases and can last 60–90 minutes.

Differential Diagnosis

(Note: Children may have EIB [Figure 41-1] in addition to any of the disorders listed here.)

Unrecognized or poorly controlled asthma

Anxiety

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Figure 41-1. Diagnostic flowchart for exercise-induced bronchoconstriction (EIB). Reprinted with permission from Krafczyk MA, Asplund CA. Exercise-induced bronchoconstriction: diagnosis and management. Am Fam Physician. 2011;84(4):427– 434. Copyright © 2011 American Academy of Family Physicians. All Rights Reserved.

Deconditioning

Vocal cord dysfunction

Exercise-induced laryngomalacia

Exercise-induced anaphylaxis

Exercise-induced reflux

Central airway obstruction arrhythmias

Pulmonary or cardiac shunt

Diagnostic Considerations

Comprehensive History and Physical Examination

Obtaining a history alone has been shown to lead to under- and over-diagnosis of EIB.

Rule out other etiologic origins, including vocal cord dysfunction, arrhythmias, and pulmonary or cardiac shunt.

Obtain a complete family history, including asthma or relatives with atopy.

Pulmonary Function Testing

While spirometry is the most important pulmonary function test, there are other tests that can be considered when evaluating a patient with exercise-related respiratory symptoms, including some that are more sensitive and/or less effort-dependent than spirometry alone. For the purpose of this review, discussion will be limited to the use of spirometry in the diagnosis of EIB.

Spirometry

All patients with suspected EIB should perform spirometry.

Assess the patient for baseline airway obstruction (ratio of FEV1 to forced vital capacity up to the lower limit of normal for age).

Bronchodilator Responsiveness

Identify bronchodilator responsiveness, defined as an increase of ≥12% in FEV1 after inhalation of a short-acting bronchodilator.

Bronchoprovocation Techniques

FEV1 decrease ≥10% from a pre-exercise level is diagnostic of EIB, with an FEV1 decline of ≥50% considered to indicate severe EIB.

Indirect testing: Exercise, eucapnic voluntary hyperpnea, inhaled powdered mannitol, or nebulized hypertonic saline (see Table 41-1)

Elicits inflammatory response to release mediators and provokes airway smooth muscle constriction

Measurements obtained 5, 10, 15, and 30 minutes after exercise

Direct challenges: Methacholine or histamine

Acts directly with airway smooth muscle receptors to cause constriction independent of airway inflammation

Table 41-1. Indirect Testing (Performed in a Pulmonary Function Laboratory) for the Diagnosis of Exercise-Induced Bronchoconstriction
Test Description
Exercise Laboratory or field basedInvolves 2 min of warm up to 85% MVV, then sustaining for 6 minFEV1 measured pre-exercise and at 5, 10, 15, and 30 min after exercise in the laboratory settingFEV1 measured before and after exercise in the field
Eucapnic voluntary hyperpnea Voluntary breathing of hypercapnic air (4.5%–5% CO2, 21% O2) at 85% MVV for 6 minFEV1 measured pre-exercise and at 5, 10, 15, and 30 min after exercise
Mannitol Inhalation of dry powder mannitol with measurement of FEV1 1 min after inhalationMannitol dose doubled until FEV1 change ≥15%, in between dose decrease ≥10% FEV1 or maximum cumulative dose
Hypertonic saline Inhalation of 4.5% hypertonic saline with FEV1 measured every 60 s Repeat dosing until FEV1 change ≥15%

FEV1, forced expiratory volume in 1 second; MVV, maximal voluntary ventilation.

Management

Pharmacological and nonpharmacological management strategies are summarized in Box 41-1.

Pharmacological Therapy

Pretreatment before exercise

Short-acting β-agonists

▪First-line treatment for EIB

▪Two puffs 15 minutes prior to exercise

▪Peak bronchodilation at 15–60 minutes, coverage for 3 hours

Leukotriene receptor antagonist: Montelukast therapy offers protection against EIB and improvement of decrease of FEV1 after exercise

▪Onset of action within 2 hours, with continued benefit for ≤24 hours

▪Often suggested in individuals with allergic rhinitis

Daily inhaled corticosteroids should be used in patients with refractory or daily symptoms or asthma

▪Long-term control of asthma with anti-inflammatory medication reduces airway responsiveness and frequency and severity of EIB

▪May take 1–2 weeks after therapy initiation to see maximal improvement

Additional therapies

Antihistamine may be helpful in individuals with allergies.

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Aug 22, 2019 | Posted by in PEDIATRICS | Comments Off on Exercise-Induced Bronchoconstriction

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