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Poikilocapnic hypoxic ventilatory response in humans during 0.85 MAC isoflurane anesthesia
Author(s) -
SJOGREN D.,
SOLLEVI A.,
EBBERYD A.,
LINDAHL S. G. E.
Publication year - 1994
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1994.tb03857.x
Subject(s) - hypercapnia , medicine , isoflurane , anesthesia , hypoxic ventilatory response , hypoxia (environmental) , anesthetic , halothane , respiratory system , capnography , airway , respiratory minute volume , oxygen , acidosis , chemistry , organic chemistry
Ventilatory responses to hypoxia (HVR) were investigated using poikilocapnic conditions (i.e. end–tidal CO 2 ′s allowed to seek it's own level) in 15 cardio–pulmonary healthy patients who were first studied awake and then at 0.85 MAC isoflurane. The influence of hypercapnia (HyperCapnic Ventilatory Response, HCVR) was also elucidated. Pneumotachography, capnography and airway occlusion pressures at 0.1 s (P < u) were used before and during both mild hypoxia (end–tidal O 2 tension 8.7 kPa) and hypercapnia achieved by an inspired CO 2 concentration of 5%. HCVR was attenuated by 60% during anesthesia ( P < 0.01). In the awake state , five of the 15 patients decreased HVR during hypoxia as compared with during normoxia. This resulted in a V E that on average increased by 0.6 l–min ‐1 ( P < 0.05) whereas P E 0 1 was unchanged. In the anesthetized state , no case of decreased HVR was seen and hypoxia induced a mean V E increase (±s.d.) by 1.0± 0.2 lmin ‐1 ( P < 0.001) and a P E 0 1 that on average was improved by 0.63 ± 0.27 cm H 2 O ( P < 0.01). It is suggested that when the aim is to evaluate the influence of volatile anesthetic agents on HVR and to quantitate its clinical relevance during and immediately after anesthesia, a poikilocapnic technique should be used. It is concluded that the poikilocapnic HVR to P F .o 2 ′s of 8.7 kPa was maintained during 0.85 MAC isoflurane.