What is an eucapnic hyperventilation (EVH) test?
Which individuals require eucapnic hyperventilation (EVH) test?
Eucapnic voluntary hyperventilation (EVH) is usually done for below individuals:
- Occupations in which asthma needs to be excluded, such as divers and army personnel
- In professional athletes to prove that they have exercise-induced bronchospasm (EIB) and hence need to take medications for the same during a competition
- To evaluate young active-duty soldiers in the military for unexplained shortness of breath
In which patient conditions eucapnic hyperventilation test shouldn’t be done?
Eucapnic voluntary hyperventilation (EVH) shouldn’t be done in
- Patients with seizures
- Pregnant women
- Patients who may develop breathing problems due to spirometry
- Patients with a recent severe asthma attack or any other respiratory disease
- Patients who had heart disease condition within three months prior to EVH test
- Patients with uncontrolled hypertension
What should a patient avoid prior to an eucapnic hyperventilation test?
Eucapnic voluntary hyperventilation (EVH) is a painless test, and patients may need to be calm, which can help them during breathing challenges.
- Patients may need to avoid smoking at least six hours before the test because it may give false-positive results.
- Patients may need to avoid heavy meals or any alcoholic drinks. Patients might also need to avoid spicy foods and caffeine-containing drinks (which may cause heartburn, indigestion, or reflux) on the day of the procedure.
- Patients may be asked to avoid any strenuous exercise or excess exposure to cold/hot air within four hours prior to the test.
- Certain medications, such as steroids bronchodilators, need to be taken many hours prior to the procedure. Doctors may usually advise the patients regarding medications a day prior to the procedure.
What happens during the eucapnic hyperventilation test?
The eucapnic voluntary hyperventilation (EVH) test was designed to mimic the effect that prolonged exercise has on the airways. The procedure usually takes between 60 and 90 minutes depending on the patient’s breathing and further procedures.
- Spirometry testing will be done before and after the six-minute test. Spirometry is a test that measures how much and how fast a patient can force air out of their lungs. A value called FEV1 obtained during the spirometry test is used as a parameter during the test.
- The patient uses a nose clip to prevent air escape.
- During the procedure, the patient breathes a specific gas mixture (21% oxygen, 5% carbon dioxide, and balance nitrogen) at high minute ventilation.
- The patient actively hyperventilates for a total of six minutes.
- Spirometry testing is done at the end of the test and 5, 10, 15, and 20 minutes after the breathing challenge to measure FEV1.
- The test is considered positive if FEV1 falls to less than 10% of the pre-test value.
- Depending on FEV1 levels, bronchospasm is classified as mild, moderate, and severe (severe >30% fall in FEV1).
- The doctor may perform a laryngoscopy procedure after the breathing challenge. During laryngoscopy, the doctor will place a fiber optic probe (small tube) in the patient’s nose. The tube is passed through the nose to the back of their throat. The movement of the vocal cords can be seen with the probe.