Static compliance before and after vaginal delivery.

Static total and lung compliance measurements were made in five healthy term-pregnant women immediately before and after vaginal delivery using a super-syringe and oesophageal balloon. Chest wall compliance was calculated from the formula of Comroe and associates (1962). The influence of supine recumbent v. lithotomy position was also evaluated and compared to five non-pregnant women. Following parturition, total and chest wall compliances increased significantly while lung compliance changes were variable and of smaller magnitude. In most patients, recumbent total and chest wall compliances were higher than lithotomy position values. The difference was greatest in the antepartum group and smallest in the control group. The mass factor of the enlarged uterus elevating the diaphragm appears to be the main cause for the antepartum decreases in total and chest wall compliance.