OBSERVATIONS DURING ENDOBRONCHIAL ANAESTHESIA I: VENTILATION AND CARBON DIOXIDE CLEARANCE

Abstract

SUMMARY Changes in the ability of the lungs to clear carbon dioxide were measured at different stages during non-cardiac thoracic operations. Studies were carried out in seventeen patients who had been intubated with Robertshaw double-lumen endobronchial tubes. Minute volume, carbon dioxide output, arterial carbon dioxide tension and physiological deadspace to tidal volume ratio (VD/VT) were statistically unchanged by moving patients from the supine to the lateral position and by opening die pleural cavity. During and after periods of one-lung ventilation, the physiological pattern of behaviour observed during lobectomies and pneumonectomies (resection group of patients) differed from that observed during exploratory thoracotomies and non-pulmonary surgery (non-resection group of patients). The resection group of patients showed a progressive improvement in the efficiency of carbon dioxide clearance (falling VD/VT) at the commencement of, and after 10 minutes of one-lung ventilation. The improvement was maintained when two-lung ventilation was resumed after lobectomy and after the pulmonary artery had been tied in pneumonectomy. The non-resection group of patients did not display any significant change in VD/VT in relation to periods of one-lung ventilation.