Anesthetic effects on ventilation in patients with chronic obstructive pulmonary disease

The effects of 1.0 per cent end-tidal halothane-oxygen anesthesia on spontaneous ventilation, ventilatory deadspace, functional residual capacity (FRC), and alveolar-arterial oxygen difference (A-aD-O-2) were measured in patients with chronic obstructive pulmonary disease and in normal patients of similar age. results obtained were compared with values obtained preoperatively from the same patients. The following were measured: 1) ventilation and ventilatory deadspace, breathing room air and breathing 100 per cent oxygen; 2) functional residual capacity (FRC) and alveolar-arterial oxygen tension difference (A-aD-O-2); 3) forced expiratory volume in 1 second (FEV1.0); 4) ventilatory response to exogenous carbon dioxide. Findings indicated that ventilation is depressed more during halothane anesthesia in patients with emphysema than in normal patients and that the extent of depression is best related to a preoperative measurement of FEV1.0 (P less than 0.001, r = 0.86). The depression in alveolar ventilation results primarily from a reduction in tidal volume. A-aD-O-2 and ventilatory deadspace-to-tidal volume ratio are increaded and FRC decreased with anesthesia in patients with COPD, but the changes are no greater than those found in normal patients.