PURPOSE: Strenuous exercise performed at altitude increases cardiac output and pulmonary arterial and capillary pressures to levels that may exceed a tolerable alveolar-capillary load, thereby evoking fluid leakage into the interstitial space. Accordingly, this study aimed to determine whether running an ultramarathon at moderate altitude increases extravascular lung water (EVLW) and whether this inhibits the transfer of gas across the alveolar-capillary membrane.
METHODS: Cardiac biomarkers (cTnI & BNP), exhaled nitric oxide (ExNO), echocardiographic signs of EVLW, and lung (DLco) and alveolar-capillary membrane (Dm) diffusing capacity for carbon monoxide (determined via a single-breath DLco/DLno method) were assessed in 53 runners (10 Females; Age:41±10y BMI:23±2kg/m2) before, 1-4h and 24h after a 100km (CCC: 6,100m of ascent, altitude range of 1,035-2,584m) or 170km (UTMB: 10,000m of ascent, altitude range of 1,035-2,565m) mountain ultramarathon.
RESULTS: Participants finished the ultramarathon in 27±12h with an average heart rate of 124±13bpm. Cardiac biomarkers were increased acutely after the race (cTnI: 0.01±0.00 vs. 0.04±0.01ng/ml, p<0.01; BNP: 21±2 vs. 123±12pg/ml, p<0.01), while ExNO decreased (25.6±2.0 vs. 14.5±1.3 ppb, p<0.01). Signs of EVLW increased after the race (average comet tails count: 2±1 vs. 7±1, p<0.01) while DLco decreased (31.6±1.0 vs. 28.6±0.9 ml/min/mmHg, p<0.01) but Dm remained unchanged (171.4±7.6 vs. 167.2±8.8 ml/min/mmHg, p>0.05). Cardiac biomarkers, ExNO, EVLW and Dm were similar to baseline values after 24h of recovery, while DLco remained mildly reduced (30.6±1.6 ml/min/mmHg, p<0.05).
CONCLUSIONS: These data suggest a mild and transient increase in cardiac biomarkers and extravascular lung water occur after completing an ultramarathon at moderate altitude, but this has minimal impact on the transfer of gas across the alveolar-capillary membrane, despite an overall reduction in lung diffusion. In some subjects an exaggerated increase in extravascular lung water and decrease in alveolar-capillary membrane diffusion was observed, suggesting that some individuals may have an increased propensity for developing mild exercise-induced pulmonary edema at altitude.