Exercise-induced laryngeal obstruction (EILO) is a transient, reversible narrowing of the

larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...

that occurs during high intensity exercise. This acts to impair airflow and cause

shortness of breath Shortness of breath (SOB), known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that con ...

stridor Stridor () is an extra-thoracic high-pitched breath sound resulting from turbulent air flow in the larynx or lower in the bronchial tree. It is different from a stertor, which is a noise originating in the pharynx. Stridor is a physical sig ...

and often discomfort in the throat and upper chest. EILO is a very common cause of breathing difficulties in young athletic individuals but is often misdiagnosed as

asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...

or exercise-induced bronchoconstriction.

Causes

EILO may arise because of a relative mechanical 'insufficiency' of the laryngeal structures that should act to maintain glottic patency. It has been proposed that a narrowing at the laryngeal inlet during the state of high airflow (e.g. when running fast), can act to cause a pressure drop across the larynx which then acts to 'pull' the laryngeal structures together. The Bernoulli principle states that increasing airflow through a tube creates increasing negative pressures within that tube. Complex neuromuscular functioning is required to maintain laryngeal opening and to allow the larynx to achieve a great number of tasks (i.e. speaking, airway protection, swallowing). It is thus also possible that EILO may arise as form a degree of neuromuscular failure. A small heredity study indicated that an autosomal dominant model of inheritance with variable expressivity and reduced penetrance in males may be relevant; because in ten families studied, there was at least one affected person in every generation in which both parents were examined. Further work is needed to determine if structural deficiencies in the laryngeal tissue of individuals with EILO are present.

Mechanism

EILO is typically caused by a narrowing of the supra-glottic structures of the larynx. In severe cases, these structures, also called

arytenoids The arytenoid cartilages () are a pair of small three-sided pyramids which form part of the larynx. They are the site of attachment of the vocal cords. Each is pyramidal or ladle-shaped and has three surfaces, a base, and an apex. The arytenoid ...

, can close over to almost completely close the laryngeal inlet. In fewer cases, the glottic (i.e. vocal cord) structures close together and this is typically what happens during exercise-induced vocal-cord dysfunction. EILO develops during intense exercise and closure develops as exercise becomes more intense. Closure of the voice box during exercise causes increased 'loading' on the breathing system and the respiratory muscles have to work much harder.

Epidemiology

The prevalence of EILO in adolescents and young adults appears to be in the range of 5–7% in northern Europe, with some indication that EILO may be more prevalent in highly trained athletes. Some, but not all studies report a higher female prevalence. Thus, in a study of 94 patients diagnosed using the CLE test, average age was ~15 years, and 68% were female. In athletic individuals EILO appears to be a highly prevalent cause of cough and wheeze and can co-exist with EIB. In one study, of almost 90 athletes, with unexplained respiratory symptoms, EILO was found to be present in approximately 30% of athletes, whilst EILO and EIB co-existed in one in ten. This condition can co-exist with other conditions, including severe asthma.

Clinical features

* Key clinical features often include: ** Difficulty 'catching a breath' ** Wheeze or whistling sound; typically when breathing in when exercising hard ** Throat or upper chest discomfort * Symptoms often start to improve from the time of exercise cessation / reducing exercise intensity * No improvement with standard asthma medication (e.g.

salbutamol Salbutamol, also known as albuterol and sold under the brand name Ventolin among others, is a medication that opens up the medium and large airways in the lungs. It is a short-acting β2 adrenergic receptor agonist that causes relaxation of ...

, albuterol).

Diagnosis

The current gold-standard means for diagnosing EILO is the continuous laryngoscopy during exercise test (CLE-test). This test involves the placement of a flexible laryngoscope via nostril, which is then secured in place and held with headgear. It allows continuous visualization of the laryngeal aperture during exercise. The CLE test can be used during indoor treadmill or cycle-ergometer exercise but also whilst rowing or swimming or exercising outdoors. The examiner visually evaluates the relative change of the laryngeal inlet in the patient throughout the CLE-test. One common grading system uses 4 steps (0-3) on glottic and supraglottic level respectively. Grades 0-1 are considered normal, whereas grades 2-3 on either or both levels are consistent with EILO. There is a need to identify other less-invasive means of making a secure diagnosis.

Treatment

The current mainstay of treatment is therapy-based. Specialist breathing techniques, most commonly termed biphasic breathing techniques or EILOBI are recommended to reduce turbulent inspiratory airflow and thus reduce chance of laryngeal closure. Direct laryngeal visualisation during exercise to deliver biofeedback has been employed with success. The place of inspiratory muscle training (IMT) is yet to be defined in EILO therapy. Surgical treatment with supraglottoplasty has also been utilised with success. Avoiding unnecessary treatment with asthma inhalers is important.