Arterial oxygen tension during sleep in the third trimester of pregnancy.
BACKGROUND
Changes during pregnancy include reduced functional residual capacity (FRC) and residual volume (RV), increased alveolar difference for oxygen and, in the supine position, reduced cardiac output. In conjunction with sleep-related disturbances, these changes could lead to maternal oxygen desaturation during sleep.


OBJECTIVE
Because of conflicting data from respiratory sleep studies in pregnancy, we performed complete polysomnography on 21 pregnant women at the 36th week of gestation and again postpartum. We also measured the partial pressure of oxygen in the arterial blood (PaO2) in the supine and sitting positions.


METHODS
We tested 21 healthy pregnant women at the 36th week of gestation. Arterial samples were taken in the sitting position. Complete polysomnography was performed in all of the pregnant women. Before the polysomnography arterial samples were taken in the supine and sitting positions and then every 2 h until termination of the study.


RESULTS
We did not find any correlation between SaO2/PaO2 levels and apnea, hypopnea or percent of rapid eye movement (REM) sleep. The frequency of apnea and hypopnea was significantly lower during pregnancy (5.81 +/- 2.1 apneas or hypopneas per hour of sleep) than postpartum (12.1 +/- 2.7 apneas or hypopneas per hour of sleep) (p < 0.001), which may be due to the raised level of progesterone. The PaO2 levels in the supine position were significantly lower than in the sitting position at 36 weeks of gestation (p < 0.001). No differences were found between PaO2 levels in the sitting and supine positions postpartum (p < 0.5).


CONCLUSIONS
According to our results we conclude that 1) the frequency of apnea and hypopnea in pregnancy was significantly lower than postpartum, and 2) a significant difference in PaO2 levels in the sitting and supine positions was observed at 36 weeks of gestation.
Prodromakis
E
E
Division of Pulmonology, Laboratory of Sleep and the Department of Obstetrics and Gynecology, University of Patras Medical School, Patras, Greece.
Trakada
G
G
Tsapanos
V
V
Spiropoulos
K
K
D000328:Adult; D005260:Female; D006801:Humans; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D017286:Polysomnography; D011184:Postoperative Period; D011187:Posture; D011247:Pregnancy / Q000097:blood*; D011263:Pregnancy Trimester, Third; D012890:Sleep / Q000502:physiology*; D012891:Sleep Apnea Syndromes / Q000503:physiopathology; D016683:Supine Position
D010100:Oxygen