Exercise-induced oxyhaemoglobin desaturation, ventilatory limitation and lung diffusing capacity in women during and after exercise

Arterial haemoglobin saturation during exercise in healthy young women [eight subjects mean (SEM) age 20.8 (1.8) years] was measured to confirm the theory that young women experience exercise-induced arterial hypoxaemia (EIAH) at a lower relative percentage of maximal oxygen uptake (V̇O2max) than has been documented in their male counterparts. To determine if flow limitation [the percentage of the tidal volume (VT) that met or exceeded the boundary established by multiple maximal expiratory manoeuvres] and/or post-exercise lung diffusing capacity are linked to EIAH in women, and to investigate the influence of exercise intensity and duration on post-exercise carbon monoxide lung diffusing capacity (DL, CO), these parameters were measured during and after three exercise tests (incremental test until exhaustion, 5 km run and 5 km run with sprint). All subjects experienced physiologically significant EIAH (a fall of more than 3% in oxygen saturation of arterial blood from levels at rest) and seven subjects experienced flow limitation during the V̇O2max protocol [mean (SD) 12.2 (8.8)% of VT]. Even though there was no significant relationship between aerobic capacity and the degree of flow limitation (r = 0.33, P > 0.05), the flow limitation was related to absolute ventilation in the subjects studied (r = 0.82, P < 0.05). There was no significant relationship between decrements in post exercise DL, CO and EIAH (r = 0.05, P > 0.05), however there was a strong correlation between the extent of flow limitation (% of V T) and EIAH (r = 0.71). Significant decreases in DL, CO lasted for up to 16 h after each of the exercise tests (P < 0.05) and lasted for a further 8 h after the maximal test (P < 0.05). Exercise intensity was the main contributing factor to the observed decreases in post-exercise D L, CO with the percentage of V̇O2max attained during the various tests being significantly related to the fall in DL, CO for 1, 2, 3, 16 and 24 h after exercise (P < 0.05). As the appearance of flow limitation closely coincided with the appearance of EIAH, the results from the present study suggest that flow limitation is a contributing factor to EIAH in women although the exact mechanism remains unclear. © Springer-Verlag 2002.