VARIATIONS IN LUNG VOLUME AND COMPLIANCE DURING PULMONARY SURGERY

Functional residual capacity (FRC) and breath-by-breath complianceof the ventilatory system (C₁₅) were measured in 10 mechanicallyventilated patients during anaesthesia for lung surgery (pneumonectomy,lobectomy, lung or pleural resections or exploratory thoracotomy).In eight patients not requiring pneumonectomy, FRC of the lowerlung decreased by 8±9% (mean± 1 SD) (P < 0.05)while that of the upper lung increased by 75±24% (P <0.001) when the patient was turned to the lateral position.When the pleura was opened, FRC of the lower lung decreasedby a further 10±10% (P <0.01). One-lung ventilation(OLV), however, increased FRC of the lower lung back to thevalue found in the supine position before surgery. When two-lungventilation was re-established, FRC of the lower lung was aboutthe same as during corresponding stages before OLV. In the twopatients who underwent pneumonectomy, FRC of the remaining lungwas about 30% greater after OLV than at corresponding stagesbefore surgery. In the patients not requiring pneumonectomy,C₁₅ decreased from 29±6ml/cm H₂O to 23±6ml/cmH₂O (P < 0.05) on the lower side when the patient was turnedon his side. The corresponding figures on the upper side were24±8 ml/cm H₂O and 30±5ml/cm H₂O respectively(P < 0.05). There was no further significant change whenthe pleura was opened. After surgery when the patient was turnedto the supine position, C₁₅ of the lung not operated on wasalmost the same as before surgery.