Fig. 2. Effects of isoflurane and desflurane on pulmonary arterial impedance spectra, in hyperoxia (  top ) and in hypoxia (  bottom ). Values are presented as mean (SDs not shown for clarity). No significant difference was found between isoflurane and desflurane. Both anesthetics increased total resistance in hyperoxia and in hypoxia and increased characteristic impedance only in hyperoxia (  P < 0.05 by trend analysis). MAC = minimal alveolar concentration; rad = radians.