Pre-Operative Evaluation of Regional Pulmonary Function
In patients with lung cancer, quantitative studies play an important role in determining the risk of post-operative pulmonary insufficiency. A forced expiratory volume in 1 second (FEV1) > 2L or greater than 60% of the predicted value usually indicates that pneumonectomy is feasible [2]. The values are lower (FEV1 > 1.5 or over 40% predicted) for lobectomy [2]. Estimating post-operative pulmonary function employs lung scintigraphy for a more accurate determination of the patient's ability to undergo surgery [2]. A predicted post-operative FEV1 of less than 0.8 liters (or less than 40% of predictive) is indicative of a high risk for morbidity and mortality following lung resection surgery and generally precludes surgical intervention [2].
The American College of Chest Physicians recommends using quantitative perfusion scintigraphy in patients with borderline lung function (FEV1 < 2.0 L or less than 60% predicted) to predict post operative lung function in pneumonectomy candidates [1]. Due to the close relationship between ventilation and perfusion, quantitative differential perfusion scans can be used to determine the patients expected post-op FEV1. Split function of each lung is determined by computing the geometric mean of counts collected from both anterior and posterior images. The post-op FEV1 is calculated by multiplying the global pre-op FEV1 by the split function of the remaining lung. The correlation with actual post operative lung function is between r = 0.67 to 0.94 with scintigraphy typically predicting lower than actual remaining lung function [1]. Ventilation scintigraphy may be a better predictor of post operative function, but central airway tracer deposition can potentially limit the results [1]. The technique could be enhanced by the use of ventilation gases (Techne-gas) [1]. SPECT perfusion imaging can also be performed [2].
REFERENCES:
(1) AJR 2006; Win T, et al. Ventilation-perfusion scintigraphy to predict
postoperative pulmonary function in lung cancer patients undergoing
pneumonectomy. 187: 1260-1265
(2) Ann Thorac Surg 2006; Mineo TC, et al. Usefulness of lung perfusion scintigraphy before lung cancer resection in patients with ventilation obstruction. 82: 1828-1834
