Inhalation anaesthetics produce asynchronous reversal of ventilation inhomogeneity and increased lung resistance in a canine model of bronchial asthma.
Bronchial asthma is characterized by not only an increase in lung resistance but also inhomogeneous ventilation. We aimed to investigate how two inhalation anaesthetics, isoflurane and sevoflurane, relieve ventilation inhomogeneity and reduce lung resistance in the bronchoconstricted lung. We provoked bronchoconstriction in dogs by a continuous i.v. infusion of methacholine, then administered either isoflurane or sevoflurane. Ventilation inhomogeneity was quantified by the difference in respiratory phases between the regional alveolar pressures measured at two distinct lobes. We constructed a mathematical model that simulated our experimental results. Both anaesthetics decreased lung resistance (P < 0.01). Isoflurane significantly reduced the indices of inhomogeneity (P < 0.01). Sevoflurane exerted only a tendency to reduce uneven ventilation. Our model simulation suggested that the anaesthetics reduced ventilation inhomogeneity in preference to lung resistance when the dogs suffered from severe bronchoconstriction.
Ishikawa
T
T
Department of Anesthesiology, School of Medicine, Chiba University, Japan.
Shinozuka
N
N
Sato
J
J
Nishino
T
T
D000403:Airway Resistance / Q000187:drug effects; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001249:Asthma / Q000139:chemically induced / Q000503:physiopathology*; D016085:Bronchoconstrictor Agents; D004195:Disease Models, Animal; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D016210:Methacholine Chloride; D015656:Respiratory Mechanics / Q000187:drug effects*
D018685:Anesthetics, Inhalation; D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride