We were interested to read Professor Baraka's description of the value of differential lung ventilation in preventing the hypoxaemia associated with one-lung ventilation (Anaesthesia 1994; 4 9 881-2). He describes the use of a screw clamp to partially occlude one limb of the double-lumen catheter mount. The lung of the operated side is therefore ventilated with small tidal volumes and a degree of expiratory resistance. Oxygenation is maintained, but lung movement is reduced to a level which does not interfere with surgery.Two years ago, we briefly described the usefulness of this technique during thoracoscopic ligation of pulmonary bullae [ 11. Full deflation of the operated lung is not desirable in such cases, since a degree of ventilation allows bullae to be more easily identified, and the site of an air leak can occasionally be verified by visual inspection. The associated reduction in lung movement facilitates the snaring of bullae. With the patient anaesthetised and a double-lumen endobronchial tube in place, carbon dioxide is insufflated into the pleural cavity to generate an intrapleural pressure of 6-8 mmHg (0.8-1 kPa), and the thoracoscopic telescope is introduced. A gate-clamp is then used to gradually compress the limb of the double-lumen catheter mount which is connected to the operated lung. The surgebn and anaesthetist observe the effects on the video screen and the degree of compression is adjusted until a satisfactory result is achieved. We tind that effects vary markedly from patient to patient, presumably influenced by the intrinsic resistance and compliance of the affected lung. However, it should be stated that with increasing surgical expertise at snaring bullae, this procedure is generally now performed in our hospital with full ventilation to both lungs.

No abstract