Eucapnic Voluntary Hyperventilation
What it measures: Respiratory function
Why have it? With incidence of exercise-induced asthma at around 20 per cent among track and field athletes (twice as high as the general population) respiratory testing is de rigueur at elite level. ‘Eucapnic Voluntary Hyperventilation (EVH) is the gold-standard test used to reveal any issues with the respiratory system,’ says Dr James Hull, a consultant respiratory physician at the Royal Brompton Hospital and Centre of Health and Human Performance. Normally, exercise is beneficial for asthma, but in elite endurance athletes, including runners, repeated intensive breathing can, over time, damage the airways.
But asthma isn’t the only cause of breathing problems. Exercise-induced laryngeal obstruction (EILO), a narrowing of the larynx during exercise, can cause wheezing, coughing, breathlessness and throat irritation during or after a run. ‘This is often misdiagnosed as asthma,’ says Hull. EILO can be precipitated by reflux, nasal hay fever symptoms or excessive mouth breathing. ‘While you have to breathe through the mouth during high-intensity exercise, it’s preferable to breathe through the nose at rest and when exercising at very low intensities, to protect the airways,’ says Dr John Dickinson, exercise respiratory physiologist at the clinic. ‘Nasal breathing is better because the nose performs several important functions, including filtering and humidifying atmospheric air, and slowing air flow.’
EVH can also reveal how you breathe. ‘Many people breathe very high up in the chest or use ‘accessory’ muscles in the neck and shoulders to expand the lungs,’ explains Dickinson. ‘It’s more efficient to breathe from the diaphragm. We observe athletes throughout the test and can teach those with dysfunctional breathing patterns exercises to improve breathing technique.’
What’s it like? The EVH test is simple, but not easy. It entails donning a face mask and breathing cold, dry air enriched with five per cent carbon dioxide through a mouth tube for six minutes, aiming to match a precalculated target breathing rate. It seems strange to be undertaking a test of maximal breathing sitting on a stool, but within a minute or two, you feel as if you’re racing the last kilometre of a 5K.
Before the test and at timed intervals afterwards, your FEV1 – the amount of air you can exhale in one second – is measured, to assess the effect the hard breathing has had on lung function and how quickly it recovers. ‘Assuming a normal baseline FEV1, performance in the test would need to drop by 10-15 per cent to be a cause for concern,’ says Hull. My pre-test FEV1 was 13 per cent above average for my age and gender, and dropped by eight per cent afterwards, making a swift return to normal. And while my post-race wheezing showed up like a bad penny, I felt reassured enough that there were no signs of asthma to take no further action.
Details: EVH test and consultation, £400 at the Centre of Health and Human Performance