Influences on the cardiovascular response to graded levels of systemic hypoxia of the accompanying hypocapnia in the rat

The Journal of Physiology
J M Marshall, J D Metcalfe

Abstract

1. In spontaneously breathing, anaesthetized rats, a study was made of the effects upon the graded cardiovascular responses to systemic hypoxia (inspiratory fractional O2 concentration, Fi, O2: 0.15, 0.12, 0.08, 0.06) of maintaining arterial CO2 pressure (Pa,CO2) at the air-breathing level by adding CO2 to the inspirate (eucapnic hypoxia), rather than allowing Pa,CO2 to fall (hypocapnia hypoxia). 2. At each Fi,O2, maintenance of eucapnia significantly reduced the increase in respiratory frequency, but significantly accentuated the increase in tidal and minute volume: as a result the fall in Pa,O2 at each Fi,O2 was significantly reduced. 3. Concomitantly, maintenance of eucapnia reduced the increase in heart rate (HR) and fall in arterial pressure (ABP), the effects being significant at Fi,O2 0.08 and/or 0.06. There was also a tendency for the increases in renal and femoral vascular conductances (RVC, FVC) to be reduced; at Fi,O2 0.06 mean increases from control were 2 +/- 10 vs. 16 +/- 7% (eucapnia vs. hypocapnia) for RVC, and 62 +/- 11 vs. 106 +/- 27% for FVC. 4. As maintenance of eucapnia reduced the fall in Pa,O2 at each Fi,O2, the above results were also considered as a function of Pa,O2. Then, maintenance of eucapnia had s...Continue Reading

Citations

Jul 1, 2008·Respiratory Physiology & Neurobiology·Richard J A Wilson, Kevin J Cumming
Jul 21, 2016·Scientific Reports·Kathleen CantowErdmann Seeliger
Aug 12, 1998·Brazilian Journal of Medical and Biological Research = Revista Brasileira De Pesquisas Médicas E Biológicas·J M Marshall
Aug 8, 2002·Clinical and Experimental Pharmacology & Physiology·Janice M Marshall
Aug 12, 2004·British Journal of Cancer·O ThewsP Vaupel
May 17, 2000·Pediatric Research·O HafströmH W Sundell
Apr 1, 1997·Journal of Applied Physiology·G BaoE C Fletcher
Sep 12, 2015·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Jennifer Magnusson, Kevin J Cummings
Jul 1, 2017·Anesthesiology Research and Practice·Koichi ShimoKenji Shigemi

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