What does a eucapnic voluntary hyperpnea (EVH) test show?

From the Guidelines

A eucapnic voluntary hyperpnea (EVH) test primarily shows whether a person has exercise-induced bronchoconstriction (EIB), also known as exercise-induced asthma. The test is used to diagnose EIB by measuring the change in forced expiratory volume in one second (FEV1) after a subject inhales a eucapnic gas mixture (5% CO, 21% O2, and balance N2) for about 6 minutes, as described in the study by 1. During this test, the patient breathes at a high ventilation rate, which mimics the respiratory conditions experienced during intense exercise. The test measures lung function before and after this breathing challenge, typically using spirometry to assess FEV1, with a significant drop in FEV1 (usually 10% or more) after the challenge indicating a positive test result, suggesting the presence of EIB, as supported by the guidelines outlined in 1. The EVH test is considered more sensitive than standard exercise challenges for diagnosing EIB, particularly in athletes, because it creates a more standardized stimulus to the airways. Some key points to consider when interpreting the results of an EVH test include:

• The severity of EIB can be graded as mild, moderate, or severe if the percent fall in FEV1 from pre-exercise level is > 10% but <25%, >25% but <50%, and >50%, respectively, as outlined in 1.
• The test works by triggering airway cooling and drying, which are the primary mechanisms that provoke bronchoconstriction in susceptible individuals.
• The eucapnic (normal CO2) component ensures that hypocapnia (low CO2) doesn't occur during the high ventilation rates, which could otherwise affect the results, as noted in 1. Overall, the EVH test is a valuable tool for diagnosing EIB and assessing airway responsiveness in individuals, especially athletes, as discussed in 1 and 1.

From the Research

Eucapnic Voluntary Hyperpnea Test

The eucapnic voluntary hyperpnea (EVH) test is a diagnostic tool used to assess exercise-induced bronchospasm (EIB) or exercise-induced bronchoconstriction (EIB-C).

What the Test Shows

• The EVH test measures the response of the airways to hyperpnea (rapid breathing) with a gas mixture that maintains a normal carbon dioxide level 2, 3.
• It is used to diagnose EIB, a condition characterized by acute, transient airway narrowing associated with exercise 2.
• The test can also help identify other conditions, such as exercise-induced laryngeal obstruction (EILO) 3.
• EVH testing has been shown to be diagnostic in a large majority of patients, with a high sensitivity and specificity for EIB diagnosis 2, 3.

Key Findings

• A study published in 2009 found that EVH testing was diagnostic in 81% of patients tested, with a threshold of 60% of the predicted maximum voluntary ventilation (MVV) per minute used as a criterion for an adequate EVH test 2.
• Another study published in 2022 found that EVH was a feasible diagnostic modality to evaluate for EIB in a community pulmonary practice, with 85% of patients achieving an interpretable test with a maximum voluntary ventilation (MVV) >60% 3.
• The reproducibility of EVH testing has been evaluated in asthmatic children and adolescents, with a study published in 2021 finding a short-term test-retest agreement of 72.5% and a Cohen's kappa coefficient of 0.452 4.

Clinical Applications

• EVH testing can be used in various clinical settings, including general pulmonary practice, community-based pulmonary practice, and specialized university clinics 2, 3, 4.
• The test can help guide treatment decisions and minimize misdiagnosis and mistreatment of EIB and other respiratory conditions 3, 4.
• EVH testing has been compared to other diagnostic tests, such as mannitol challenge, and has been found to have a high sensitivity and specificity for EIB diagnosis 5.