Background: To investigate whether the effects of desflurane on inspiratory resistance are similar to those of isoflurane and sevoflurane during 30 min administration at 1 and 1.5 MAC in patients with healthy lungs.
Methods: Seventy-one patients undergoing elective surgery were randomly assigned to receive isoflurane, sevoflurane, or desflurane. Baseline inspiratory resistance was obtained after intubation and establishment of volume control ventilation. Anaesthesia was maintained with desflurane, isoflurane, or sevoflurane at 1 MAC for 30 min followed by 1.5 MAC for another 30 min. Tidal volume, flow, and inspiratory pressures were continuously recorded with a pneumotachograph. Total inspiratory resistance (R(rs)), minimal resistance (R(min)), and effective resistance (D(Rrs)) were calculated every 5 min using the end-inspiratory occlusion technique.
Results: No significant differences of the evaluated parameters (R(rs), R(min) and D(Rrs)) were observed during administration of the three agents at 1 MAC for 30 min. At 1.5 MAC, desflurane caused a maximum increase in R(rs) by 26% and in R(min) by 30% above baseline, in contrast to isoflurane and sevoflurane which did not display a significant effect on R(rs) (+3.7% by isoflurane and +7.6% by sevoflurane) and R(min) (+4.7% by isoflurane and +9.6% by sevoflurane). All parameters returned to baseline after discontinuation of the volatile agent.
Conclusions: In healthy adults, neither sevoflurane nor isoflurane produced bronchodilation at 1 and 1.5 MAC. Desflurane did not affect respiratory resistance at 1 MAC, but at 1.5 MAC caused significant increase in both total and airway resistance with return to near baseline values after discontinuation of the agent.