The Relationship Between Exhaled Volatile Organic Compounds And Respiratory Function In Response To Ultra-endurance Exercise

Abstract

PURPOSE: To date, limited studies have examined exhaled VOC profiles in response to a physiologic stressor such as ultra-endurance exercise. Accordingly, this study evaluated VOC production in exhaled breath and the relationship to respiratory function in response to running an ultramarathon. METHODS: Breath samples (VOC Breath Biopsy, Owlstone Medical, Cambridge UK) were collected from 29 ultra-endurance runners before and after participating in either the 2019 Ultra-Trail du Mont-Blanc (171 km) or Courmayeur-Champex-Chamonix (100 km) ultramarathon. Additionally, subjects performed pulmonary function tests (PFT) before and after the race. A Wilcoxon signed-rank test was performed to evaluate changes in the intra-participant exhaled VOCs between the pre- and post-race breath samples. A Pearson Correlation Coefficient was used to determine any correlations between changes in exhaled VOCs and PFTs. Only participants who performed PFTs and “breath biopsies” pre- and post-race were included in the analysis (n = 23). RESULTS: Participants completed the ultra-marathons on average in 29.3 ± 12.1 hours. In total, 811 unique VOCs were measured and studied for differences between the pre- and post-race participant breath samples, with 63 having significant (P < 0.05) changes pre to post-race (12 decreased, 51 increased). Of these, 10 had identities assigned from the Breath Biopsy Laboratory. These VOCs were predominately comprised of methyl- and ethyl-containing compounds (n = 9) and ketones (n = 6), which possibly relate to inflammation or metabolic shifts. Four of the identified VOCs (Isopropyl Alcohol, Methyl Vinyl Ketone, Hexamethyldisiloxane, and 2, 3-Butanediol) correlated significantly to changes in inspiratory volumes and flows, possibly linking these VOCs to a reduction in lung function. For example, increases in 2,3-Butanediol were correlated to decreases in forced inspiratory vital capacity (R = -0.51, P = 0.01), FIV1(R = -0.50, P = 0.02), and peak inspiratory flow rate (R = -0.047, P = 0.02). CONCLUSIONS: These data suggest there are exhaled VOCs of biological origin that may significantly change in response to ultra-endurance exercise. Additionally, the magnitude of change in a subset of these VOCs may correspond to decrements in respiratory function resulting from this extreme physical activity.