How does a quantitative ventilation perfusion scan assist in preparing patients for lung surgery?
Quantitative V/Q scans help in the preoperative assessment of patients by demonstrating areas of the lung that have the poorest overall function. This may help direct surgeons to preferentially resect those areas of lung that have the worst function. Perhaps more importantly, the quantitative analysis provides a percentage of function for the various lobes of the lung and for the lungs overall. When this percentage is multiplied by the forced expiratory volume in 1 second (FEV 1 ), the surgeon can predict how much overall lung function will be left if certain parts of the lung are removed. For example, if a patient requires a right upper and right middle lobectomy for lung cancer, and the remaining right lower lobe and the whole left lung account for 70% of the lung function, then the surgeon can determine whether the patient will be able to maintain adequate respiratory reserve after surgery. In general, the remaining FEV 1 should be at least 700 mL/min. In the example described, the patient needs to have an FEV 1 prior to surgery of at least 1000 mL/min so that the remaining 70% will provide the necessary function for postoperative survival.