Is lung diffusing capacity lower in expiratory flow limited women compared to non-flow limited women during exercise

Women tend to have smaller lungs than men of the same size as well as narrower airway diameters compared to men matched for the same sized lungs. Additionally, women with smaller airways relative to lung size are more likely to experience expiratory flow limitation (EFL) as well as exercise-induced arterial hypoxemia (EIAH). One of the possible causes of EIAH is a diffusion limitation, evidenced by widening in the alveolar to arterial oxygen pressure difference (A-aDO2). This study tested the hypothesis that lung diffusing capacity (DLCO) is lower in women with EFL compared to non-flow limited (NEFL) women during exercise. DLCO was measured using a rebreathing technique at rest and at 40-, 60-, and 80-percent of VO 2max in women with EFL (n = 7) and women without (NEFL, n = 9). Arterial saturation was measured using pulse oximetry (SpO2) . There was no difference in DLCO between groups, however SpO2 was significantly lower in the EFL females compared to NEFL females. Since there were no differences in DLCO between the two groups, this has been eliminated as a possible cause for differences in SpO2 between EFL and NEFL females during exercise.