PROGNOSTIC RELEVANCE OF PREOPERATIVE PULM ONARY-FUNCTION TESTS

At Leipzig University, preoperative pulmonary function testing has bee n performed for about 3 years in order to detect and classify patients at high pulmonary risk. During the postoperative period, the risk of developing pulmonary complications is particularly high due to factors influencing respiratory mechanics such as the supine position, pain, residual effects of narcotic drugs, etc. It has often been emphasised that an underlying ventilatory disturbance such as obstructive lung di sease or smoking may enhance the postoperative pulmonary risk, althoug h the extent of the influence of preoperative pulmonary diseases on th e postoperative complication rate is still controversial. The predicti on of postoperative lung function from preoperative spirometric values is complicated by factors such as patient cooperation, pulmonary comp lications secondary to aspiration, infection, peritonitis, etc., and b y differing and therefore non-comparable postoperative care. For this reason, the criteria for assessing pulmonary risk vary widely. Methods . We examined 339 patients (mean age 59.3 years) preoperatively by qui et and forced spirometry; in most cases we also measured airway resist ance and functional residual capacity. We estimated the postoperative lung function using the quadrant scheme of Miller and compared this ri sk class with our spirometric diagnosis and the postoperative clinical course. Results. According to our results, Miller's classification se ems inadequately differentiated for patients with mild to moderate ven tilatory disturbances. A relatively high percentage of these patients were considered to have normal postoperative lung function. Some patie nts with severely diminished pulmonary function were classified as hav ing sufficient postoperative lung function. The number and severity of pulmonary complications also corresponded better with the spirometric diagnosis, which was made using all spirometric parameters and not on ly vital capacity (VC) and 1-s forced expiratory volume (FEV1). We fou nd that the percentage of primary respiratory complications increased with deterioration of the preoperative spirometric values. To provide a prognostic model combining both the advantages of using only a few p arameters (FEV1, VC) and appropriate risk assessment, we propose a mod ification of the Miller scheme consisting of five risk classes. The an alysis of the respiratory therapy regimen was unsatisfactory because o f discrepancies between the predicted pulmonary risk, the use of respi ratory therapy, and the occurrence of pulmonary complications. Conclus ions. For minimising perioperative pulmonary complications, respirator y care (prophylaxis and therapy) adequate for the functional risk of t he patient is necessary. We assume that intensive pre- and postoperati ve respiratory care and therapy in patients with underlying reductions in ventilatory function can help to avoid or reduce respiratory compl ications. The modification of Miller's scheme proposed after evaluatin g the postoperative course of our patients provides a differentiated p rognostic model that allows the establishment of an appropriate and ec onomical therapeutic regimen of perioperative pulmonary care.