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Hypoxic and hypercapnic ventilatory responses during isoflurane sedation and anaesthesia in women
Author(s) -
Sollevi A.,
Lindahl S. G. E.
Publication year - 1995
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.1399-6576.1995.tb04200.x
Subject(s) - isoflurane , medicine , anesthesia , hypoxic ventilatory response , tidal volume , respiratory minute volume , ventilation (architecture) , hypoxia (environmental) , respiratory rate , inhalation , respiratory system , hypoventilation , hypercapnia , acidosis , heart rate , oxygen , mechanical engineering , chemistry , organic chemistry , blood pressure , engineering
This study primarily examined the effect of three endtidal isoflurane concentrations (0.2, 1.0 and 1.4%) on the isocapnic hypoxic ventilatory response (HVR), as well as the hypercapnic ventilatory response (HCVR), in 18 women (ASA I) who were all in the follicular phase of their menstrual cycle. Capnography was used, together with pulseoximetry to indicate desired levels of hypoxia (SpO 2 75–80%). This hypoxic challenge resulted, after 3–4 min, in a stable ventilation, and ventilation measurements were then taken during a 90 s period. The HCVR provocation (inhalation of 4.5% CO 2 in air) and measurements were conducted using a similar time frame as for HVR. Isoflurane 0.2% did not affect any ventilatory parameter. Isoflurane 1.0 and 1.4% dose‐dependently increased endtidal CO 2 and respiratory rate, while tidal volumes decreased. Minute ventilation was not reduced. HVR, as well as HCVR, were both uninfluenced by isoflurane 0.2%. HVR was reduced by 60–70% at isoflurane 1.4% ( P <0.0l), and was parallelled by a similar depression of HCVR ( P <0.01). The HVR during anaesthesia was accomplished by a respiratory rate response, while the increase in tidal volume, seen in the awake state, was abolished. The HCVR during anaesthesia was, on the other hand, the result of a dose‐dependently depressed tidal volume response, without any increase in respiratory rate. In conclusion, isoflurane 0.2% did not affect the ventilatory response to mild isocapnic hypoxia, nor to mild hypercapnic challenge. During anaesthesia with isoflurane (1.0 and 1.4%), there was a parallel reduction of HVR and HCVR.