title: Effect of isoflurane on bronchomotor tone in man.
abstract: Twenty patients were anaesthetized with thiopentone, the trachea intubated and the lungs ventilated with 70% nitrous oxide and oxygen. Normocapnia was maintained and, following control measurements of the specific conductance of the lower airways (s.Glaw), either 1.7% isoflurane or 1.3% halothane was added to the inspired gas mixture, 10 patients receiving each drug. s.Glaw was measured repeatedly during the next 30 min. There was a tendency for s.Glaw to increase--indicating a reduction in bronchomotor tone--during the administration of isoflurane, the effect approaching statistical significance. The administration of halothane was associated with a significant increase in s.Glaw. There was a statistically significant increase in the expiratory reserve volume, and a decrease in mean respiratory resistance over the tidal range in both groups. These results indicate that isoflurane does not cause an increase in bronchomotor tone, and may have a tendency to decrease it. This suggests that the previously reported increase of respiratory resistance during isoflurane anaesthesia resulted from a reduction in lung volume, rather than a change in bronchomotor tone.
mesh_terms: D000293:Adolescent; D000328:Adult; D000403:Airway Resistance / Q000187:drug effects; D001980:Bronchi / Q000187:drug effects*; D005105:Expiratory Reserve Volume; D005260:Female; D006221:Halothane / Q000494:pharmacology; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D009129:Muscle Tonus / Q000187:drug effects
chemical_list: D008738:Methyl Ethers; D007530:Isoflurane; D006221:Halothane