Exercise-induced laryngeal obstruction (EILO) is an important and possibly treatable cause of exertional dyspnea, affecting about 5.7–7.6% of a general population and 8.1–27% of athletic populations[1–4]. EILO is an umbrella term, encompassing glottic obstruction—previously described by a variety of terms including vocal cord dysfunction (VCD) and paradoxical vocal fold movement disorder (PVFMD)—as well as supraglottic obstruction[5]. EILO causes respiratory symptoms of especially inspiratory character during high-intensity effort[6, 7]. It is important to test for EILO in patients with exercise-induced dyspnea, because EILO is often mistaken for asthma and the two conditions often co-exist[1, 2, 8]. Because symptoms of EILO abate quickly upon exercise cessation, diagnosis requires visualizing the larynx during, or in close association to, exercise or heavy breathing[6, 9, 10]. Examination post-exercise likely has low sensitivity[10]. A common test used in the clinical and research setting is the continuous laryngoscopy during exercise (CLE) test[11]. The test involves the use of a flexible nasolaryngoscope during a maximal effort exercise bout, usually on a treadmill or bicycle[12, 13]. Other exercise-modalities have been tested[14, 15]. The laryngeal obstruction at the glottic (i.e., vocal cord) and supraglottic levels is then graded, usually by an observer using a 0–3-point visual grade score[13, 16].
Only one study has described the natural course of CLE-based EILO in teenagers given advice on breathing techniques and having predominantly supraglottic EILO. Obstruction and respiratory symptom decreased to some extent over a period of 2–5 years[17]. Non-surgical treatment of EILO may be most effective in glottic EILO, as indicated in two recent small studies focusing on inspiratory muscle training and on breathing techniques combined with cognitive behavioral therapy[18, 19]. Nonetheless, advice on breathing techniques during exercise is recommended to patients with mild EILO regardless of the location of obstruction, whereas surgical treatment is an option in selected highly motivated patients with severe supraglottic EILO[10, 17, 20, 21]. Other interventions such as biofeedback, speech therapy, and laryngeal control therapy may also have an effect on EILO[9, 10, 22–24]. However, the few longitudinal studies on EILO patients have not included asymptomatic controls. Indeed, there is currently a lack of evidence regarding treatment of EILO, and no randomized controlled trials of treatment have been published.
The assessment of laryngeal obstruction using the CLE test with the visual grade score is observer-reliant and therefore somewhat subjective. Between-rater agreement regarding visual grade scores varies from slight to identical[16, 25, 26]. Intra-rater agreement ranges from fair to identical, when observers repeat the visual scoring 3 weeks to 2 months after the first scoring[16, 26]. When the CLE test was repeated during a 3-week period in subjects who mainly had EILO, there were changes in the grading of laryngeal obstruction resulting in diagnostic implications[26]. A recent review on EILO in highlighted our scarce knowledge on the natural history and prognosis of EILO [27].
We need more understanding of the validity of the CLE test, the natural history of EILO and effects of treatment. The aim of this prospective study was to examine the variability of CLE scores in athletes, irrespective of EILO diagnosis, treatment, and respiratory symptoms.