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Hyperoxic exposure affects the ventilatory response to hypoxia in awake rats
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 1, 1988
Summary
Hyperbaric oxygen (HBO) therapy can temporarily reduce the body's response to low oxygen levels (hypoxic ventilatory drive). This effect on breathing is reversible and likely impacts oxygen sensors in the carotid bodies.
Area of Science:
- Physiology
- Respiratory Medicine
- Hyperbaric Medicine
Background:
- Hyperbaric oxygen (HBO) therapy involves breathing pure oxygen under increased atmospheric pressure.
- The effects of HBO on the hypoxic ventilatory drive, crucial for maintaining breathing during low oxygen conditions, are not fully understood.
Purpose of the Study:
- To investigate the potential adverse effects of hyperbaric oxygen (HBO) on the hypoxic ventilatory drive in rats.
- To determine the reversibility and duration of any observed effects on respiratory parameters.
Main Methods:
- Rats were exposed to hyperbaric oxygen (HBO) at various pressures (1.67, 1.90, 2.15 ATA) or air (1.90 ATA) for 550 minutes.
- Ventilatory parameters, including frequency, tidal volume, and minute ventilation, were measured using whole-body plethysmography.
- Measurements were taken before, immediately after, and up to 20 days post-exposure under various inspired gas conditions.
Main Results:
- HBO at 1.90 and 2.15 ATA reduced breathing frequency and increased tidal volume.
- Minute ventilation was largely unaffected except for a marked attenuation during initial breaths of 4.5% O2.
- Hypoxic ventilation significantly decreased by 48-68% after HBO exposure, with recovery observed within days.
Conclusions:
- Hyperbaric oxygen (HBO) therapy reversibly depresses the hypoxic ventilatory drive.
- The primary mechanism is likely a direct effect on the carotid O2 chemoreceptors, which sense oxygen levels.
- These findings highlight a potential physiological consequence of HBO therapy that warrants consideration.