The effects of oral contraceptives on respiration.

The effect synthetic progestins found in current oral contraceptives may exert on respiratory function has not been thoroughly investigated. This study monitored potential changes in respiratory parameters 3 and 6 months subsequent to beginning administration. Static and timed spirometric maneuvers showed significant increases in only tidal volume (P = 0.01). Ventilatory response to treadmill exercise monitored the oxygen uptake, CO2 elimination (VCO2), minute ventilation (VE), and respiratory exchange ratio at each of four workloads. An analysis of the covariance (ANCOVA) for the slopes revealed no significant variation between test periods. The ANCOVA for the means showed increases in VE and VCO2. These results suggest a stimulatory role for synthetic progestins, although ventilatory performance in response to moderate exercise does not appear compromised.