COMMENTARY

The Eucapnic Voluntary Hyperventilation Test: When It's Used, What It Means

Aaron B. Holley, MD

Disclosures

August 12, 2016

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. The result is bronchoconstriction.[1]

Approximately 90% of people with untreated asthma experience bronchoconstriction during exercise. Patients without asthma also experience airway drying and cooling with exercise, which is diagnosed as exercise-induced bronchoconstriction (EIB). Elite athletes in particular often have EIB.[2,3,4]

The eucapnic voluntary hyperventilation (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.

The EVH test was developed and extensively studied at the Walter Reed Army Medical Center in Washington, DC.[5] It is an indirect bronchoprovocation test and has been endorsed by the International Olympic Committee. It is considered the test of choice for diagnosing EIB.[6,7]

Specificity has always been an issue, however. A 10% drop in FEV1 at any point after the EVH test is considered positive for EIB. However, in certain populations, positive rates run very high.[2,3,4] In our laboratory, we found that when patients were tested with both the methacholine challenge and EVH, there were three times as many positive results with EVH testing.[8] We attributed this to the methacholine challenge being insensitive for EIB, which is plausible. It is also possible that a portion of the abnormal EVH tests were false-positive.

A short communication that was published in the American Journal of Respiratory Care[9] this year showed that a substantial number of athletes with no symptoms will have a positive EVH test using the 10% criterion. The authors retrospectively reviewed EVH results from 224 elite or international-level athletes who were completely asymptomatic and had normal lung function. They found that almost every study subject had some degree of bronchoconstriction after EVH, and 20% of subjects met the 10% criterion. Given the absence of clinical signs or symptoms, none of these persons would be diagnosed with EIB.

EVH is a huge part of our practice in the military, because we often evaluate young active-duty soldiers for unexplained shortness of breath. EIB is among the most common diagnoses.[10,11] EVH is also an important tool for clinicians who treat athletes, whether they are elite or simply recreational. As we continue to push our patients to exercise, pulmonary clinicians should understand when to order an EVH or other indirect bronchoprovocation test and how to interpret it.

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