The Effect of Progesterone on the Respiration of Patients With Emphysema and Hypercapnia*

The possibility that progesterone could influence breathing was first suggested by studies investigating the respiration of pregnant women. In 1912 Leimdorfer, Novak and Porges (1) found that the alveolar concentration of CO2 was lower in pregnant women than it was in the same individuals when they were not.pregnant. These observa- tions were amplified and confirmed in 1915 by Hasselbalch and Gammeltoft (2). Beginning in 1947, Dbring, Heerhaber and co-workers (3-5) investigated the effect of pregnancy in lowering the alveolar CO2 tension and later extended the stud- ies to measurements of CO, tension made during the normal menstrual cycle. They were able to show that the alveolar CO2 tension was depressed in the luteal phase of the cycle and that if preg- nancy occurred this depression continued through- out gestation, rising shortly after delivery. This suggested to them that progesterone might play a role in the genesis of the decrease in alveolar CO2 tension and they were able to show that 50 mg. of progesterone given intramuscularly to normal men caused a stimulus to breathing which reached its maximum about 12 hours after injection.