T3 Increased respiratory neural drive and work of breathing in exercise-induced laryngeal obstruction. (15th November 2017) - Walsted, ES
Abstract : Background: Exercise induced laryngeal obstruction (EILO), a clinical phenomenon in which the larynx closes inappropriately during physical activity, is a prevalent cause of exertional dyspnoea in young individuals and is often misdiagnosed as asthma. The physiological ventilatory impact of EILO and its relationship with dyspnoea has not been studied and we therefore sought to provide new insight by developing a methodology to facilitate synchronous evaluation of exercise related changes in laryngeal aperture on breathing pattern, pulmonary mechanics and respiratory neural drive. Methods: We prospectively evaluated six subjects with EILO and six healthy age- and gender-matched control subjects. Subjects underwent detailed physiological assessment and a symptom-limited incremental exercise test with simultaneous and synchronised laryngoscopic video, gastric-, oesophageal- and transdiaphragmatic pressures, diaphragm electromyography and respiratory airflow. Results: The EILO and control groups had a similar peak power output and minute ventilation (VE) (power: 227±35 vs. 237±35 watts; VE: 103±20 vs. 98±23 L/min; p>0.05). At submaximal work rates (140–240 W) subjects with EILO demonstrated increased work of breathing (p<0.05) and respiratory neural drive (p<0.05), developing in close temporal association with onset of endoscopic evidence of laryngeal closure (p<0.05). Unexpectedly, there were no differences in dyspnoea intensity whilst a ventilatory increase, driven by augmented tidal volume (p<0.05), was seen in subjects with EILO, before the onset of laryngeal closure. Conclusions: Using novel methodology, we found respiratory work and respiratory neural drive increases in close association with paradoxical laryngeal closure; highlighting the importance of the upper airway contribution to respiratory loading.