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Halothane effects on ventilatory responses to changes in intrapulmonary CO2 in geese
J Pizarro1, J W Ludders, M A Douse
1Department of Comparative Biosciences, University of Wisconsin, Madison 53706.
Respiration Physiology
|December 1, 1990
Summary
Halothane anesthesia disrupts avian CO2-sensitive intrapulmonary chemoreceptors (IPC), affecting ventilation. This impairment occurs at low CO2 levels, influencing breathing patterns in birds.
Area of Science:
- Anesthesiology
- Comparative Physiology
- Respiratory Physiology
Background:
- Avian respiratory systems possess unique CO2-sensitive intrapulmonary chemoreceptors (IPC).
- Halothane anesthesia is known to affect respiratory control, but its specific impact on avian IPC is not well understood.
Purpose of the Study:
- To investigate the hypothesis that halothane anesthesia functionally disrupts CO2-sensitive IPC in birds.
- To elucidate the effects of halothane on ventilatory reflexes mediated by intrapulmonary CO2.
Main Methods:
- Experiments were conducted on 6 unidirectionally ventilated geese under pentobarbital anesthesia.
- Each lung was independently ventilated, with halothane introduced only to the left lung.
- The left pulmonary artery was occluded, and the right lung was vagally denervated to isolate effects.
Main Results:
- Halothane (1-2%) increased respiratory amplitude (RA) within a limited range of left lung CO2.
- Neither halothane nor CO2 in the left lung affected respiratory frequency.
- Higher CO2 levels were required to initiate ventilation in geese compared to previous chicken studies.
Conclusions:
- Halothane impairs avian lung CO2 reflexes primarily by affecting IPC.
- Intrapulmonary halothane augments ventilatory activity at low, but not high, intrapulmonary CO2 levels.
- Halothane's effects on IPC may explain its distinct ventilatory actions in birds versus mammals.