[Relation of the fall in PO2 in ventilation of the lower lung in pulmonary surgery and the preoperative distribution of respiratory function].

Hypoxaemia during one-lung ventilation is influenced by the anatomic distribution of lung perfusion and hypoxic vasoconstriction. This study aimed to assess whether preoperative selective bronchospirometry could predict the degree of peroperative hypoxaemia. Twelve patients scheduled for pneumonectomy, lobectomy, wedge resection or decortication were included in the study. Preoperative data included the usual spirometric parameters, oxygen consumption, minute ventilation of each lung and arterial blood gases. A Carlens or Robertshaw tube was inserted in each case; the patients were ventilated with 100% oxygen and halothane was used for anaesthesia. Blood gases were measured during surgery before and after upper lung exclusion. When both lungs were ventilated, mean PaO2 was 390.5 +/- 92.4 mmHg; during one-lung ventilation, it fell to 210.8 +/- 109.2 mmHg. Routine spirometry could not predict the magnitude of fall in PaO2; however, it was correlated with the bronchospirometric oxygen consumption of each lung (r = 0.83; p less than 0.01). The anatomical distribution of lung perfusion seemed to be the predominant factor influencing the decrease in PaO2 during one-lung ventilation.