Exhaled particle size and phospholipid composition of the respiratory tract lining fluid following moderate-intensity...

Exercise-induced bronchoconstriction (EIB) commonly develops after exercise in cold, dry environments, but the effects of acute exercise in the cold on airway physiology remain incompletely understood. Exhaled particle (PEx) analysis offers a novel, non-invasive approach to assess respiratory tract lining fluid (RTLF) composition and may provide mechanistic insights into airway responses before clinically detectable changes occur. This study investigated the PEx response to moderate-intensity exercise in sub-zero conditions among healthy atopic and non-atopic individuals. Eighteen participants (14 male, 29 ± 6 years) performed two moderate-intensity exercise trials (30 and 90 min duration) in a climate chamber at -15 °C. PEx samples were collected using the PExA® method, before and 30 min after exercise to assess particle mass and count across eight size bins (0.4-5µm) and for subsequent lipidomic analysis. Exercise induced a significant increase in smaller PEx (0.4-0.7μm;p< 0.01). Three lipid species were altered after 30 min exercise, and 11 after 90 min exercise. Phosphatidylethanolamine PE(16:1_18:0) was the only lipid that consistently increased across both exercise durations (30 min:p= 0.023; 90 min:p= 0.044;g= 0.97). Three specific lipid species showed differential exercise responses between atopic and non-atopic participants, including an oxidised phosphatidylcholine species PC(16:0_9:0;O) (p= 0.006,q= 0.59,g= 0.86). These results provide preliminary insight into airway surfactant responses to exercise in a cold climate and contribute to the growing understanding of how the PExA® method can be applied as a non-invasive tool for respiratory health assessment in an acute setting.