Introduction
Exercise-induced laryngeal obstruction (EILO) is a common cause of exertional breathing problems and affects 5%–7% of otherwise healthy adolescents.1 EILO seems even more prevalent among athletes reported to be 27% or more.2 Prevalence studies in general adult populations are lacking. Key symptoms of EILO are inspiratory breathing problems during high-intensity exercise, often accompanied by coarse or high-pitched inspiratory breath sounds, feeling of tightness in the throat or neck area and sometimes stridor.3 These symptoms are associated with a paradoxical obstruction of laryngeal structures that otherwise appear normal, most often predominantly involving the supraglottic folds, but often followed by adduction also of the vocal cords. Symptoms of EILO typically resolve within minutes after exercise has ended but may also be prolonged in some cases.4 Episodes of EILO can be associated with profound and frightening symptoms. Affected individuals might have difficulties performing in sports, and some refrain from taking part in even modest physical activities. While historically often misdiagnosed as asthma, studies have demonstrated that EILO and asthma can coexist.2
The laryngeal obstruction observed in EILO is exclusively linked to exercise as trigger,5 but several risk factors have been proposed but not proven, including asthma, gastro-oesophagal reflux disease, anatomic factors related to the upper airways and genetic factors.4 While the pathophysiology is poorly understood, the increased airflow induced by the high-volume ventilation required to perform exercise, somehow triggers the paradoxical adduction we can observe in the laryngoscope.6 There is currently consensus that we should distinguish between EILO with predominantly glottic and supraglottic obstruction, as these might represent different phenotypes.5,7 Some few studies have suggested how the larynx normally should respond to exercise in non-athletes.1 8 Athletes have increased physical and ventilatory capacity compared with the more sedentary part of the population, implying higher volumes of air passing through the larynx at higher velocities, setting up a condition with increased negative intraluminal laryngeal pressures. Conceivably, this might lead to inward collapse of laryngeal structures in susceptible individuals. Accordingly, several studies have revealed high prevalence of EILO in athletes compared with non-athletes.2 4
This raises the question of whether the higher prevalence of EILO observed in athletes is directly attributable to the increased ventilatory demands imposed by their rigorous training and performance regimes. Such a hypothesis underscores the importance of further research into the interplay between heightened ventilatory needs during intense exercise and the risk of EILO, aiming to clarify the underlying mechanisms that predispose athletes to this condition.
Endurance athletes, during years of training, repetitively expose their airways to high-volume ventilation, and we do not know how this influences laryngeal structure and function over time. Thus, we lack the necessary knowledge to confidently decipher what should be considered normal laryngeal movements during high-intensity exercise in these individuals. This has implications for how EILO could be diagnosed in this group. The main purpose of the CLE test is to identify abnormal laryngeal movement during exercise. If the larynx behaves differently in athletes with higher ventilation volumes compared with the general population, it could potentially lead to misdiagnosis of EILO.
We therefore aimed to investigate laryngeal response patterns to high-intensity exercise in a healthy population of athletes with no prior self-reported perception of respiratory problems. We hypothesised that in this population, no objective signs of laryngeal obstruction would be present during the CLE test.