Heliox moderates multidimensional domains of exertional dyspnoea in people with COPD

Introduction Avoidance and premature cessation of exercise resulting from exertional dyspnoea are common in people with COPD. Dyspnoea includes multidimensional domains of intensity, unpleasantness and sensory descriptors. Low viscosity Helium gas mixes are known to improve exercise tolerance, but their effect on multidimensional domains of exertional dyspnoea in people with COPD are unknown. Aim To determine if a mixture of 79:21 Helium:Oxygen (Heliox [HeO 2 ]) alters the perception of exertional dyspnoea during constant work rate (CWR) exercise in people with COPD. Methods Using a randomized, double blind, cross over design, participants completed four cycle ergometry tests including, an incremental symptom limited test to WR max , a familiarisation CWR (at 60% WR max ) test on medical air (MA) and CWR tests on HeO 2 and MA. Gas mixes were administered via closed breathing circuits. On large format charts, participants indicated VAS ratings (intensity, unpleasantness) and applicable descriptors every two minutes. VAS ratings and descriptors were analysed using random effects mixed modelling. Results 14 people (11 male; mean age 69.3±6.6 yrs, FEV 1 39±9 %pred) completed all sessions. Endurance time significantly increased under HeO 2 conditions (9.3±9.2 vs. 14.3±9.1 min). Significantly slower rates of increase were observed under HeO 2 conditions for both dyspnoea intensity (p = 0.04) and unpleasantness (p=0.03). The frequency with which the dyspnoea descriptors Air Hunger (p=0.04) and Work/Effort (p=0.003) were selected was also significantly lower under HeO 2 conditions. Conclusion Heliox reduces unpleasant sensations of exertional dyspnoea thereby contributing to improved exercise tolerance in people with COPD.