Effect of severity of pulmonary disease on nitrous oxide washin and washout characteristics.

The influence of chronic obstructive pulmonary disease (COPD) on the nitrous oxide (N2O) washin and washout characteristics was evaluated in 90 (ASA II-III) males undergoing elective peripheral surgery under general anaesthesia with controlled ventilation. Patients were classified by preoperative bedside pulmonary function testing into three groups. Group I (n = 30), patients without COPD (FEV1/FVC > 80% predicted values; control group); Group II (n = 30), patients with mild COPD (FEV1/FVC = 65-79% of predicted values); and Group III (n = 30), patients with moderate COPD (FEV1/FVC = 50-64% of predicted values). The anaesthetic technique was standardized for all patients. The Datex Capnomac Ultima monitor was used to measure the inspired and expired concentrations of nitrous oxide (N2O), carbon dioxide (CO2), and isoflurane. The duration of both N2O washin (time from start of N2O administration to equilibrium of inspired and expired N2O concentrations) and 5 per cent washout (time from discontinuation of N2O to an expired N2O concentration of 5 per cent of the equilibrium value) were recorded. The duration of N2O washin and washout were significantly prolonged in Groups II and III (P < 0.001) as compared to the control group (Group I). The end-tidal CO2 concentration decreased significantly during N2O washout without causing oxygen desaturation (SpO2 < 90%). We conclude that the duration of N2O washin and washout were significantly prolonged in anaesthetized patients with COPD which may delay the induction and recovery from N2O anaesthesia.

Effects of nebulized beta 2-adrenergic agonists on pulmonary mechanics in anesthetized patients with chronic obstructive pulmonary disease.

We evaluated the effects of nebulized beta 2-adrenergic agonists on pulmonary mechanics in patients with COPD undergoing peripheral surgery with a standardized general anesthetic technique. Thirty males with COPD were randomized into one of three groups. Group I (control group; n = 10) received nebulized saline 3 ml, Group II (n = 10) received nebulized albuterol (2.5 mg in 3 ml), and Group III (n = 10) received nebulized metaproterenol (15 mg in 3 ml). At 20 min after tracheal intubation, the study drugs were nebulized over 20 min. Datex Capnomac Ultima monitor was used to measure pulmonary mechanics on a breath-by-breath basis. There was no difference between the three groups with respect to demographic data and preoperative respiratory parameters. A similar degree of DPH occurred with the initiation of mechanical ventilation in all three groups. Patients receiving nebulized bronchodilators (Groups II and III) displayed a significant decrease in DPH and an increase in total dynamic compliance. However, there were no differences in DPH and total dynamic compliance between Groups II and III. We conclude that nebulization of either albuterol or metaproterenol can alleviate DPH resulting from mechanical ventilation in anesthetized patients with COPD.