The effect of volatile anesthetics on respiratory system resistance in patients with chronic obstructive pulmonary disease.

We examined the effect of isoflurane and sevoflurane on respiratory system resistance (Rmin,rs) in patients with chronic obstructive pulmonary disease (COPD). The diagnosis of COPD rests on the presence of airway obstruction, which is only partially reversible after bronchodilator treatment. Ninety-six consecutive patients undergoing thoracic surgery for peripheral lung cancer were enrolled. They were divided into two groups: preoperative forced expiratory volume in 1 s/forced vital capacity ratio <70% or >70%. Rmin,rs was measured after 5 and 10 min of maintenance anesthesia by using the constant flow/rapid occlusion method. Maintenance of anesthesia was randomized to thiopental 0.30 mg . kg(-1) . min(-1) or 1.1 minimum alveolar anesthetic concentration end-tidal isoflurane or sevoflurane. Eleven patients were excluded: two because anesthesia was erroneously induced with propofol and nine because of an incorrect tube position. Maintenance with thiopental failed to decrease Rmin,rs, whereas both volatile anesthetics were able to decrease Rmin,rs in patients with COPD. The percentage of patients who did not respond to volatile anesthetics was larger in those with COPD as well. In conclusion, we have demonstrated that isoflurane and sevoflurane produce bronchodilation in patients with COPD.