The impact of a heat and moisture exchange mask on respiratory symptoms and airway response to exercise in asthma

Respiratory symptoms, including cough are prevalent in asthmatic individuals when exercising. This study investigates whether a heat and moisture exchanger (HME) face mask is effective in modulating exercise induced bronchoconstriction (EIB) and post exercise cough in a cold, dry environment in asthmatic individuals. Twenty-six participants diagnosed with asthma (20 males, 6 females) completed three cycling exercise challenges (EX) at 8 oC and 24% relative humidity (RH) in a randomised order. Participants wore either an HME mask (MASK), sham mask (SHAM), or no mask (CON). Following a 3-min warm-up participants completed 6-min cycling at 80% peak power output. Before and after EX, maximal flow volume loops were recorded. Post EX cough was monitored with a Leicester Cough Monitor (LCM) for 24-hours. Results were analysed using repeated measures ANOVA and Friedman's tests and data presented as the mean ± SD or median (IQR). Eleven participants failed to demonstrate EIB (i.e.>10% fall in FEV1 post EX) and were removed from analysis. The % fall in FEV1 following EX in CON was greater than MASK (MASK: -6.0 (7.0), SHAM: -11.0 (11.0), CON: -13.0 (9.0) %; p <0.01). No difference was found between EX in cough count per hour over the 24-hour monitoring period or the number of coughs in the first hour post EX. HME masks can attenuate EIB when exercising in cold, dry environments. The SHAM mask may not have been entirely inert demonstrating the challenges of running randomised control trials utilising control and SHAM conditions.