Ventilatory response to hypoxia in humans: Influences of subanesthetic desflurane

Background: At low dose, the halogenated anesthetic agents halothane, isoflurane, and enflurane depress the ventilatory response to isocapnic hypoxia in humans. In the the influence of subanesthetic desflurane (0.1 minimum alveolar concentration [MAC]) on the isocapnic hypoxic ventilatory response was assessed in healthy volunteers during normocapnia and hypercapnia. Methods: A single hypoxic ventilatory response was obtained at each of 4 target end-tidal partial pressure of oxygen concentrations: 75, 53, 44, and 38 mmHg, before and during 0.1 MAC desflurane administration. Fourteen subjects were tested at a normal end-tidal partial pressure of carbon dioxide (43 mmHg), with 9 subjects tested at an end-tidal carbon dioxide concentration of 49 mmHg (hypercapnia). The hypoxic sensitivity (S) was computed as the slope of the linear regression of inspired minute ventilation (V-I) on (100 - SpO2), Values are mean +/- SE. Results: Sensitivity was unaffected by desflurane during normocapnia (control: S = 0.45 +/- 0.07 1 . min(-1) . %(-1) vs. 0.1 MAC desflurane: S = 0.43 +/- 0.09 1 . min(-1) . %(-1)). With hypercapnia S decreased by 30% during desflurane inhalation (control: S = 0.74 +/- 0.09 1 . min(-1) . %(-1) vs. 0.1 MAC desflurane: S = 0.53 +/- 0.06 1 . min(-1) . %(-1); P < 0.05). Conclusions: On the basis of the data, subanesthetic desflurane has no detectable effect on the normocapnic hypoxic ventilatory response sensitivity. However, the carbon dioxide-induced augmentation of the hypoxic response was reduced. This indicates that subanesthetic desflurane affects the chemoreceptors at the carotid bodies.