Knowledge
EILO is a transient narrowing of the larynx during hard exertion, and one of several possible causes of breathlessness in sport. It is frequently mistaken for asthma, and many people are therefore treated the wrong way for years. What the condition is. How it differs from asthma. How the diagnosis is made.
EILO stands for exercise-induced laryngeal obstruction. The larynx sits at the top of the airway, where the air passes on its way to the lungs. During hard exertion the structures of the larynx can move inwards and narrow the opening at the very moment the need for air is greatest. The result is that it becomes hard to breathe. The movement itself is well described and can be seen directly during an examination; why it happens is not settled, and recent work suggests EILO covers several subtypes with different mechanisms.
The condition has gone by several names. EILO has also been called VCD (vocal cord dysfunction) in the past. That term is outdated and imprecise, and at times simply wrong: the narrowing most often begins above the vocal folds, in the supraglottic structures, and in some people it does not involve the vocal folds at all. Today the conditions are grouped under the term inducible laryngeal obstruction (ILO), and EILO is the form brought on by exertion.
The narrowing can sit at different levels. In some people it is the vocal folds themselves that close together (glottic), in others the soft-tissue structures above them (supraglottic), and in some it is both. The narrowing most often begins supraglottically, and in some people a glottic component follows secondarily; purely glottic narrowing is less common. Establishing which level is involved is part of what the examination does, and it is reflected directly in the Danish diagnosis codes.
EILO is not in itself dangerous. The narrowing is transient, and breathing normalises within minutes once the exertion stops. But it can be frightening in the moment, and left unexplained it makes many people avoid exactly the training they would like to do. A few people faint during a severe episode. Diving can be problematic and dangerous if you have EILO and have an episode during a dive.
Symptoms
The symptoms come at high intensity, during the effort itself, and they ease quickly once you stop. That timing is one of the clearest clues.
A short audio or video clip of your breathing during symptoms is often the single most useful thing you can bring to the first consultation. The sound of the inhalation says a great deal on its own. Note as well when the symptoms came, what you were doing, and how quickly they eased.
EILO is seen most often in teenagers and younger adults, and among those assessed for the condition, girls and women predominate. It is common among athletes and physically active people, but it is by no means confined to competitive sport: anyone who pushes themselves hard enough can experience it. It is probably more common than many assume: population studies in young people have found EILO in around 5 to 7 per cent, but the studies are few and fairly small.
Among athletes assessed for exercise-related breathlessness, EILO accounts for a substantial share of the cases. It occurs across sports, and it is seen particularly where the intensity is high and sustained: running, cycling, swimming, rowing, cross-country skiing, football, handball and combat sports.
A recurring pattern is worth noting: many people have already been treated for asthma for years, without effect, before anyone looks at the larynx.
This is the single most important distinction, and it is also the one most often got wrong. Asthma is a narrowing of the lower airways inside the lungs; EILO is a narrowing at the entrance to the airways, in the larynx. Asthma is heard as a wheeze from the chest and is worst in the minutes after exercise; EILO is heard as audible, laboured breathing from the throat, is worst during the effort itself and settles quickly once you stop. Asthma responds to medication; EILO essentially does not. And the two can perfectly well coexist, which is why a work-up should look at both rather than settle on the first plausible answer.
Diagnosis
Symptoms alone are unreliable, in both directions. The diagnosis therefore rests on objective testing, and on ruling the alternatives in or out rather than guessing between them.
When do the symptoms come, at what intensity, how quickly do they ease, what does the breathing sound like, and what has already been tried? Bring your recording if you have one.
Spirometry, and where needed a bronchial provocation test, confirms or rules out asthma. For athletes this is typically EVH (eucapnic voluntary hyperventilation) or an exercise challenge.
Continuous laryngoscopy during exercise is the only examination that shows the narrowing directly, while it is happening. It is what settles the question.
A thin, flexible endoscope camera is passed through the nose and held in place while you cycle or run up to maximal effort. The larynx can therefore be watched at the precise moment the symptoms appear, and the degree and level of the narrowing can be described rather than inferred. It sounds more uncomfortable than it is: the vast majority complete the test without difficulty.
The clinic will establish CLE in the near future. Until then, assessment and advice are given by a specialist with substantial personal experience of the examination. In the meantime the assessment includes a sport-specific history, your own audio or video recording, objective testing for asthma, an assessment by an ear, nose and throat specialist and, where relevant, a speech and language therapy assessment. If that has not already been done, we can refer you for it. If EILO is still suspected after the initial work-up, a CLE can form part of the assessment, either at the clinic once it is established or by referral to a hospital.
In the Danish classification system these conditions sit under DJ38.8, inducible laryngeal obstruction (ILO). The subcodes distinguish the level of the narrowing, glottic, supraglottic or combined, and what brings it on, exertion or irritants. The exercise-induced forms, that is EILO, are the codes ending in 1.
Management
There is no medication that targets the narrowing itself. The first-line treatment is speech and language therapy with a specialist familiar with EILO and ILO. Everything else depends on the individual picture.
The first-line choice is targeted training with a speech and language therapist who knows EILO and ILO. You learn techniques that keep the larynx open under load, and you practise using them at the intensity where the symptoms actually appear. This rests on clinical experience and case series. Speech and language therapy for EILO has not yet been tested in a published randomised trial.
For many people this alone changes a great deal. When you know that the narrowing is transient and harmless, the fear takes up less room in the moment. That the fear itself amplifies the narrowing is a widely held clinical assumption, but it has not been demonstrated. It is part of the treatment, not a substitute for it.
Depending on the individual picture, other measures can be tried, for instance adjusted warm-up and pacing, or breathing physiotherapy. The benefit for the narrowing itself is not established, and that belongs in the decision. Coexisting asthma, nasal symptoms or reflux are a different matter and should be treated on their own terms.
For a few people, and it is genuinely few, surgery of the larynx is the right solution. It applies above all to the supraglottic form, and it becomes relevant only when the problem is severe and has not responded to speech and language therapy. The procedure is irreversible and carries possible complications, so it is handled at specialist centres.
Breathlessness during exercise has a range of possible explanations, and EILO is only one of them. Exercise-induced asthma is probably more common; dysfunctional breathing, poor asthma control, nasal obstruction, anaemia and cardiac causes all belong on the list too. Which of them is in play cannot be settled from the symptoms alone, and that is precisely why the work-up looks at the whole picture rather than at one condition.
If you compete or train seriously, the work-up also needs to take your sport into account, including the anti-doping rules if asthma treatment turns out to be relevant.
Breathlessness during hard exercise is often labelled asthma, but the cause can be exercise-induced laryngeal obstruction (EILO), which sits in the larynx. The treatment differs entirely, so telling them apart matters.
Sport-specific assessment of exercise-related breathlessness in athletes: exercise-induced asthma (EIB), EILO and dysfunctional breathing.
Selected references behind this page.
FAQ
No. EILO can be intensely uncomfortable and feel frightening, but the narrowing is transient, and breathing normalises once the exertion stops. That knowledge forms part of the management. That the fear of an episode itself amplifies it is a widely held clinical assumption, but it has not been demonstrated. If you dive, however, having an episode during a dive can be dangerous.
They are closely related. ILO (inducible laryngeal obstruction) is the current umbrella term for narrowing of the larynx brought on by a trigger, and EILO is the form brought on by exertion. VCD (vocal cord dysfunction) is an earlier term for the same thing, but outdated and imprecise, because it points to the vocal folds alone, and in supraglottic EILO it is simply wrong.
Rarely. Inhaled medication acts on the lower airways in the lungs, whereas EILO sits in the larynx. A lack of effect from correctly used asthma medication is often precisely what raises the suspicion of EILO. If asthma is also present, it should of course still be treated.
The first-line treatment is speech and language therapy with a specialist familiar with EILO and ILO, where you learn techniques that keep the larynx open under load. There is no medication that targets the narrowing itself. Other measures can be tried depending on the individual picture, but without established benefit, and for a small minority surgery is the right solution. Speech and language therapy for EILO has not yet been tested in a published randomised trial, so the recommendation rests on clinical experience.
Yes, and it is not uncommon. That is why a proper work-up does not stop at the first plausible answer but looks at the whole picture: both the lower airways and the larynx.
CLE stands for continuous laryngoscopy during exercise. A thin, flexible camera is passed through the nose and held in place while you cycle or run up to maximal effort. The larynx can therefore be seen at the precise moment the symptoms appear. It is the only examination that shows the narrowing directly while it happens, and it is therefore regarded as the reference test for EILO.
In a number of young people the symptoms diminish over the years. But it is not something to wait passively for if the symptoms limit training, schooling or quality of life, and certainly not before the diagnosis has been settled.
Yes. EILO is in fact seen most often in teenagers and younger adults, and among those assessed for the condition, girls and women predominate. Many are given the correct diagnosis only after several years of treatment for asthma that did not work.
A subsidised visit under the public health insurance normally requires a referral from your GP. You can also be seen as a private or insurance patient, and no referral is required for that.
The clinic assesses exercise-related breathlessness with objective testing, and EILO is one of its areas of special expertise. A referral from your GP is normally required; you can also be seen as a private or insurance patient. This page is general information and does not replace a medical assessment.