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Hypoxia potentiates, oxygen attenuates deflation-induced reflex tracheal constriction
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1985
Summary
The reflex tracheal constriction in dogs intensifies during hypoxia and lessens during hyperoxia. This oxygen-dependent reflex involves pulmonary stretch and carotid body receptors.
Area of Science:
- Respiratory Physiology
- Autonomic Nervous System Regulation
Background:
- Tracheomotor responses are crucial for airway patency.
- The influence of oxygenation status on airway reflexes is not fully understood.
Purpose of the Study:
- To investigate how varying oxygen levels affect reflex tracheal constriction.
- To elucidate the neural pathways involved in this reflex.
Main Methods:
- Monitoring reflex tracheomotor responses in isolated canine tracheal segments.
- Evoking reflex tracheal constriction via passive lung deflation.
- Manipulating arterial oxygen tension (PaO2) to induce normoxia, hypoxia, and hyperoxia.
Main Results:
- Hypoxia (PaO2 = 44 Torr) increased reflex tracheal constriction threefold compared to normoxia (PaO2 = 78 Torr).
- Hyperoxia (PaO2 > 250 Torr) reduced the reflex response by approximately 50%.
- Denervation studies indicated a significant role for both tracheal innervation and vagal/carotid body pathways.
Conclusions:
- The magnitude of reflex tracheal constriction is significantly modulated by the prevailing state of oxygenation.
- A synergistic interaction between pulmonary stretch receptors and carotid body chemoreceptors likely mediates these oxygen-dependent reflex alterations.