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The effects of hypoxia on the ventilatory response to sudden changes in CO2 in newborn piglets.
Author(s) -
Wolsink J G,
Berkenbosch A,
DeGoede J,
Olievier C N
Publication year - 1992
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1992.sp019325
Subject(s) - hypercapnia , anesthesia , pco2 , hypoxia (environmental) , medicine , peripheral chemoreceptors , peripheral , chemoreceptor , respiration , hypoxemia , room air distribution , chemistry , acidosis , oxygen , anatomy , physics , receptor , organic chemistry , thermodynamics
1. The ventilatory response to square‐wave challenges in end‐tidal partial pressure of CO2 (PCO2) was investigated at three levels of arterial PO2 (Pa,O2) in nineteen anaesthetized 2‐ to 11‐day‐old piglets. 2. The ventilatory responses, measured on a breath‐to‐breath basis, were separated into a peripheral and a central component using a two‐compartment model. Both components were described by a CO2 sensitivity, a time constant, a time delay and a single offset. 3. Fifty‐six responses were analysed against a background of normoxaemia (Pa,O2 = 12.70 +/‐ 0.72 kPa, mean +/‐ S.D.), fifty‐three against a background of moderate hypoxaemia (Pa,O2 = 8.63 +/‐ 0.34 kPa) and fifty‐one against a background of severe hypoxaemia (Pa,O2 = 4.98 +/‐ 0.30 kPa). 4. The sensitivity of the peripheral chemoreceptors in mediating the response to CO2 increased from 38.3 +/‐ 17.0 ml min‐1 kPa‐1 kg‐1 during normoxaemia to 48.8 +/‐ 15.3 ml min‐1 kPa‐1 kg‐1 during moderate hypoxaemia and to 72.9 +/‐ 24.0 ml min‐1 kPa‐1 kg‐1 at severe hypoxaemia. 5. As compared with the central CO2 sensitivity during moderate hypoxaemia and normoxaemia (104.0 +/‐ 39.0 and 100.8 +/‐ 41.6 ml min‐1 kPa‐1 kg‐1, respectively) it decreased to 85.9 +/‐ 54.1 ml min‐1 kPa‐1 kg‐1 at severe hypoxaemia. 6. We conclude that in newborn piglets there is a positive interaction between hypoxia and hypercapnia at the level of the peripheral chemoreceptors while severe hypoxaemia reduced the CO2 sensitivity centrally.