Related Experiment Videos
Responses of respiratory drive and breathing pattern to inspiratory loading during nitrous oxide and isoflurane
1Department of Anesthesiology and Intensive Care, Karolinska Hospital, Stockholm, Sweden.
Background:
Increased inspiratory resistance in combination with mild gas narcosis is common during recovery after a general anesthesia, but there are only few previous studies on inspiratory loading during subanesthetic gas narcosis.
Methods:
Responses of respiratory drive (central inspiratory activity, P0.1) and ventilatory pattern to an inspiratory threshold load of -6 cm H2O were studied in 16 healthy subjects during mild subanesthetic gas narcosis. One group (n = 9) was exposed to 13, 26 and 39% nitrous oxide (N2O) and air control (Group N). Another group (n = 7) was exposed to 0.1, 0.2 and 0.3% isoflurane and air control (Group I). Measurements were done after 1 min adaptation to the load.
Results:
Nitrous oxide and isoflurane had no effect on respiratory drive and VT either during unloaded breathing or during inspiratory threshold loading. Across all gas concentrations (including 0% control), inspiratory threshold loading resulted in significant P0.1 increases, amounting to 62% in group N and 38% in group I. At the same time VT decreased by 11 and 12%, respectively. A significantly increased end-expired CO2 and decreased minute volume compared to air control was found during isoflurane inhalation but could be ascribed to normalization of the hyperventilation in the control situation.
Conclusions:
It is concluded that the steady-state ventilatory responses to loading, consisting of increased P0.1 and decreased VT, are maintained during inhalation of subanesthetic doses of N2O (0.13-0.38 MAC) and isoflurane (0.09-0.26 MAC).