Ventilation, EELV and diaphragmatic activity in rats during chronic normobaric hypoxia

Martin Vizek , Monique Bonora
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引用次数: 7

Abstract

We determined the effects of chronic hypoxia on end-expiratory lung volume (EELV), end-expiratory diaphragmatic activity (DE) and ventilation (V̇E) in 27 intact (awake and anesthetized) and six carotid body-denervated (CBD; anesthetized) rats. Twenty-nine control animals were also studied. Recordings were made during hypoxia and normoxia before and after 2 or 3 weeks of hypoxia (+3 days of recovery from chronic hypoxia). In awake rats, 2 weeks of chronic hypoxia increased only normoxic V̇E, while 3 weeks of chronic hypoxia did not change V̇E or DE. In anesthetized intact rats, after both exposures, hypoxic and normoxic V̇E tended to decrease, DE did not change and hypoxic and normoxic EELV were enlarged. In CBD animals, 2 weeks of chronic hypoxia did not affect hypoxic V̇E but decreased normoxic ventilation and enlarged EELV similar to the intact animals. After 3 days of recovery in normoxia, all parameters except EELV were restored to prehypoxic values. Also, transition from hypoxia to normoxia induced parallel changes in EELV and DE while chronic hypoxia increased only EELV. Therefore, chronic normobaric hypoxia induced, (1) an increase in normoxic ventilation reflecting a process of acclimatization; (2) an enlargement of EELV that did not depend on changes in DE and carotid chemoreceptors.

大鼠慢性常压缺氧时的通气、EELV和膈肌活动
我们测定了慢性缺氧对27例完整(清醒和麻醉)和6例颈动脉体去神经(CBD;大鼠麻醉)。29只对照动物也进行了研究。分别在缺氧前、缺氧后2、3周(慢性缺氧恢复后3天)进行记录。在清醒大鼠中,2周慢性缺氧仅使常氧V (E)升高,3周慢性缺氧未改变V (E)和DE。在麻醉完好的大鼠中,两种暴露后,低氧和常氧V (E)均有降低的趋势,DE无变化,低氧和常氧EELV均增大。在CBD动物中,2周的慢性缺氧不影响低氧V (E),但正常氧通气量降低,EELV增大,与未损伤动物相似。正常缺氧恢复3天后,除EELV外,所有参数均恢复到缺氧前值。此外,从缺氧到常氧的过渡会引起EELV和DE的平行变化,而慢性缺氧只会增加EELV。因此,慢性常压缺氧诱导,(1)常压通气的增加反映了一个适应过程;(2) EELV的增大不依赖于DE和颈动脉化学感受器的变化。
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