Diaphragm insertion increases human vaginal oxygen tension.

The normal insertion of a contraceptive diaphragm into the vagina of five young women induced a dramatic increase in the vaginal oxygen tension (131 +/- 13 mm Hg, mean +/- SD, n = 5), which slowly fell at an initial rate of 0.9 +/- 0.2 mm Hg/min. Withdrawal of the diaphragm immediately restored vaginal oxygen tension to the normal hypoxic state (11 +/- 12 mm Hg). The change in gaseous equilibrium created by the trapped air of the diaphragm could have significant actions on the microbial activity and balance of the vagina.