Background
Eucapnic hyperventilation (eucapnic voluntary hyperventilation [EVH]) is a provocative indirect stimulus test used to diagnose exercise-induced asthma (EIA) (defined in a patient with preexisting asthma who has an exacerbation of the asthma with exercise) or exercise-induced bronchospasm. Exercise-induced bronchospasm (EIB) is considered if the patient has no evidence of asthma except during or after exercise. [1, 2]
Prolonged exercise at high ventilatory rates causes airway cooling and drying. Vessel dilation in response to the cooling induces airway edema, and the drying causes osmotic changes and inflammation at the airway surface resulting in EIB. [3] Approximately 90% of people with untreated asthma experience bronchoconstriction during exercise, but individuals without asthma can also be diagnosed with EIB. Rates of EIB are particularly high among elite athletes. [1, 4]
Traditionally, cardiopulmonary tests (CPET) have been used to diagnose EIB, but indirect bronchoprovocation tests such as EVH can be used to accurately identify individuals who do not have EIB. [5]
The EVH test was designed to mimic the effect that prolonged exercise has on the airways. The patient breathes a specific gas mixture (21% oxygen, 5% carbon dioxide, and balance nitrogen) at a high minute ventilation for 6 minutes. Spirometry is done at 0, 5, 10, and 20 minutes after the test. A 10% drop in forced expiratory volume in the first second (FEV1) at any point after the EVH test is considered positive for EIB.
Originally developed by the military to evaluate young active-duty soldiers for unexplained shortness of breath, EVH is used approved by The International Olympic committee and World Anti-Doping Code to confirm the diagnosis of EIB for preventive and treatment-related medications to be used in competition. [1, 6] EVH is an important tool for clinicians who treat athletes, whether they are elite or recreational. It has also been used to detect EIB in patients with cystic fibrosis. [7]
The two types of provocative tests are direct and indirect. Indirect provocation tests such as EVH, mannitol, or hypertonic saline are more specific for asthma than hyperresponsiveness to a direct stimulus such as methacholine. [8, 9] Eucapnic hyperventilation is also more sensitive than sport-specific field exercise. [8] However, a substantial number of athletes with no symptoms will have a positive EVH test using the 10% criterion. In a review of EVH results from 224 elite or international-level athletes who were completely asymptomatic and had normal lung function, almost every study subject had some degree of bronchoconstriction after EVH, and 20% of subjects met the 10% criterion. Although, given the absence of clinical signs or symptoms, none of these persons would be diagnosed with EIB. [10]
EVH can be used among pediatric patients aged 10-16 years to evaluate exercise-induced dyspnea. A good cutoff value for diagnosis is a minimum 10% fall in FEV1. [11]
Indications
Indications of eucapnic hyperventilation (eucapnic voluntary hyperventilation) include the following:
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High clinical suspicion of exercise-induced bronchospasm with normal spirometry values (forced expiratory volume in the first second [FEV 1]) >80%)
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If a high clinical suspicion of exercise-induced bronchospasm persists despite negative simple challenge tests like hypertonic saline or methacholine challenge
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In the setting where asthma needs to be excluded, for example amongst commercial divers or where asthma persists and patients wish to continue taking asthma medication, for example in elite athletes during competition (International Olympic Committee Medical Commission [IOC-MC]) [12]
Contraindications
Absolute contraindications to eucapnic hyperventilation (eucapnic voluntary hyperventilation) include the following:
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Patients with known significant airway obstructions (forced expiratory volume in the first second [FEV1 ] < 50% or FEV1< 1.5 L in adults, < 1 L in children)
-
Recent severe acute asthma
-
Recent myocardial infarct or stroke within 3 months
-
Uncontrolled hypertension
-
Known aortic aneurysm
Relative contraindications include the following:
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Patients with mild-moderate obstruction
-
Spirometry-induced bronchoconstriction
-
Pregnancy
-
Patients using cholinesterase inhibitors
-
Epilepsy
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Eucapnic Hyperventilation. Equipment for eucapnic hyperventilation test.
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Eucapnic Hyperventilation. Patient undergoing eucapnic hyperventilation procedure.
Tables
Drug Category |
Medication |
Time prior to test |
Inhaled bronchodilators |
Albuterol |
8 hours |
Ipratropium |
24 hours |
|
Salmeterol |
48 hours |
|
Oral bronchodilators |
Long-acting theophylline |
48 hours |
Inhaled glucocorticoid |
|
2-3 weeks |
Oral glucocorticoid |
|
2-3 weeks |
Mast cell stabilizers |
Cromolyn sodium |
8 hours |
Antihistamines |
Diphenhydramine |
72 hours |
Chlorpheniramine |
72 hours |
|
Hydroxyzine |
72 hours |
|
Cetirizine |
72 hours |
|
Leukotriene modifiers |
Montelukast |
24 hours |
Zafirlukast |
24 hours |
