ONE-LUNG VENTILATION IN THE PIG - CARDIOPULMONARY EFFECTS OF ENDOSCOPIC AND SURGICAL TECHNIQUES

In the pig, the right upper lobe bronchus originates from the trachea. This precludes the standard method of one-lung ventilation using a do uble-lumen endobronchial tube. The aim of this study was to find a sui table non-invasive approach of lung separation in the pig, and to comp are the haemodynamic and pulmonary effects with an invasive open chest technique. In group I (n = 10), an endotracheal tube with a movable b ronchial blocker (Univent tube) was inserted into the trachea, and the blocker was advanced into the left main bronchus. Accurate position o f the blocker and occlusion of the bronchus was confirmed by fiberopti c bronchoscopy. In group II (n = 10), after lateral thoracotomy and hi lar dissection, the left main bronchus was clamped under direct vision . Proper placement of the bronchial blocker and a seal was obtained in all pigs under fiberoptic guidance. There were no significant differe nces between the groups with respect to tidal volume, peak and mean ai rway pressure, lung compliance and airway resistance. Right heart func tion as assessed by a fast-response thermodilution pulmonary artery ca theter was equivalent in both groups. Using the endoscopic technique, the pigs showed a strong hypoxic pulmonary vasoconstrictor response wi th a low intrapulmonary shunt fraction (7.1 +/- 2.3%). In contrast, an imals treated invasively with thoracotomy had a significantly higher s hunt fraction (19.9 +/- 11.0%) and lower PaO2 (73.7 +/- 16.3 vs. 88.4 +/- 11.4 mmHg; FIO2 0.21). Since both groups revealed identical mixed venous oxygen and carbon dioxide tensions, hypoxic pulmonary vasoconst riction must have been attenuated by direct surgical manipulation of t he lung.