Lack of the mechanoreceptor influences on ventilatory control during halothane anesthesia in humans

Mechanical influences independent of chemoreceptor function on ventilatory control were studied in halothane-anesthetized, artificially ventilated patients using the technique reported by Altose et al. (Respir Physiol 66: 171–180, 1986). Contribution of mechanical factor was indirectly assessed by comparing the values of arterial carbon dioxide tension at which the subjects started breathing efforts during CO₂ loading induced by the following two methods. 1) Partial rebreathing of expired gas and 2) Mechanical hypoventilation (successive decrease in inflation volume). These two maneuvers resulted in a similar rate of increase in end-expiratory carbon dioxide tension. However, contrary to the observation made by Altose et al. in awake volunteers, we found comparable values of ventilatory recruitment threshold for Pa_{CO 2}. Thus, we speculate that halothane anesthesia and/or loss of consciousness impair transmission of afferent information from the lung and/or chest wall musculature. Such effects may be responsible for the depression of load compensatory mechanism during anesthesia.(Kochi T, Ide T, Isono S, et al.: Lack of the mechanoreceptor influences on ventilatory control during halothane anesthesia in humans. J Anesth 6: 387–394, 1992)