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Hyperbaric oxygenation increases arousal and breathing movements in fetal lambs
M H Tiktinsky-Rupp1, S U Hasan, B Bishop
1Department of Physiology, State University of New York at Buffalo 14214.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1994
Summary
Elevating oxygen levels without lung inflation increases fetal arousal and fetal breathing movements (FBM) in late-gestation sheep fetuses. This response primarily occurs during arousal and non-rapid-eye-movement (NREM) sleep.
Area of Science:
- Fetal Physiology
- Respiratory Control
Background:
- Oxygenation via lung distension stimulates fetal breathing movements (FBM) and arousal in late-gestation fetal sheep.
- Previous studies focused on lung distension, leaving the effects of oxygenation alone unclear in earlier gestations.
Purpose of the Study:
- To investigate fetal breathing and behavioral responses to increased arterial oxygen partial pressure (PaO2) without lung distension.
- To examine these responses in fetal sheep at earlier gestational ages (128-132 days).
Main Methods:
- Twelve chronically instrumented fetal sheep (128-132 days gestation) were studied.
- Fetal PaO2 was increased using hyperbaric oxygenation (100% O2 at 3 ATA) in the ewe.
- Breathing, behavioral state, blood pressure, and blood gases were monitored.
Main Results:
- Hyperbaric oxygenation increased fetal PaO2 by approximately 20 Torr in both groups.
- A significant increase in arousal occurred in both groups during hyperbaric oxygenation.
- Fetal breathing movements (FBM) increased during arousal, and also during rapid-eye-movement (REM) sleep (group 1) and non-rapid-eye-movement (NREM) sleep (group 2).
Conclusions:
- Oxygenation without lung distension elevates arousal and FBM in fetuses before 135 days of gestation.
- The primary occurrence of FBM was during arousal and NREM sleep.
- Distinct patterns of diaphragmatic activity were observed during arousal and different sleep states.