STUDIES ON THE PHYSIOLOGY OF RESPIRATION IN PREGNANCY. EFFECTS OF BARBITURATES ADMINISTERED DURING LABOR 1

Abstract

An analysis of total lung volume and its subdivisions was made on 17 obstetrical patients during the antepartum and postpartum periods. Total lung volume is not significantly altered during pegnancy although the avg. increase of vital capacity was 7% above normal. Patients delivered without analgesia or anesthesia showed no significant changes or an increase of total vol. and its subdivisions during the 1st wk. following delivery. Barbiturate and scopolamine analgesia during labor combined with ether anesthesia at delivery brought about a 10% reduction of total volume, subtidal air, and vital capacity as late as the 5th postpartum day. Barbiturates alone reduced the total vol. and subtidal air but the vital capacity remained unaffected. Ether anesthesia alone decreased the total vol., subtidal air, and vital capacity, but the reduction was less than that produced by a combination of analgesia and anesthesia. External measurements of the chest and roentgenographic studies of diaphragm levels suggest that flaring of the costal margins is an adjustment for an upward displacement of the diaphragm by the advancing pregnancy. Descent of the diaphragm, to compensate for the reduction of intra-abdominal pressure which follows delivery, was retarded by analgesic and anesthetic measures.