Pulmonary Physiologic Assessment of Operative Risk

UPPER ABDOMINAL SURGERY Postoperative pulmonary collapse is related to diaphragm dysfunction, which is manifest in 50 to 60 % reduction in vital capacity for few hours to 5 days. Preoperative PFT( pulmonary function test )with spirometry is unproven to predict increased postoperative pulmonary risk.

LUNG RESECTION SURGERY If no lung is resected, the vital capacity declines 25% in early postoperative period and normalizes 4 to 6 weeks. When normal lung tissue is resected, the first is reduction of the pulmonary capillary bed. If pulmonary dysfunction exists, pulmonary hypertension will lead to cor pulmonale and death.

LUNG RESECTION SURGERY The 2 nd effect of lung resection is reduction of ventilatory capacity. Inoperability means inability of tolerance after loss of functional lung tissue. The mortality of pneumonectomy is less than 5%.

Routine Pulmonary Function Studies

Ferguson et al reported DLCO( diffusing capacity of lung for CO ) was the best predictor of postoperative pulmonary complications. DLCO measures the volume of diluted CO taken up by lung during a single breath held for 10 seconds.

Split Lung Function Studies Unilateral ventilation is measured by inhalation Xe 133 and perfusion is measured by IV Tc 99m albumin macroaggregates.

Split Lung Function Studies Postoperative FEV 1 = preoperative FEV 1 - preoperative FEV 1 x % of function of tumor- containing lung X( no. of segments of resected lobe/ total no. of segments of the lung ) E.g. preoperative FEV 1 = 2.0L right lung function=40% RUL lobectomy will be done. Postoperative FEV 1 = x40%x3/10=1.76L

Postoperative FEV 1 If radiospirometry is not done, then Postoperative FEV 1 = preoperative FEV 1 - preoperative FEV 1 x 1/19x no. of resected segments E.g. preoperative FEV 1 = 2.0L RUL lobectomy will be done. Postoperative FEV 1 = x1/19x3=1.684

Hemodynamic Studies TUPAO( temporary unilateral pulmonary artery occlusion ): inflation of the 50-ml balloon in the main PA to induce a physiologic pneumonectomy A PVR (pulmonary vascular resistance) is more than 190 dyne-sec-cm -5 than postoperative mortality is predicted.

Exercise Test Maximum oxygen consumption (VO 2 max) is measured.

SUMMARY The PFT appears to play a minor role in upper abdominal surgery and open heart surgery. No patient should be rejected for curative surgery for lung cancer based solely on spirometric finding.