Postoperative respiratory morbidity: identification and risk factors.

Two hundred consecutive patients admitted for general surgery were studied prospectively to evaluate the contribution of risk factors to postoperative respiratory morbidity (PORM). PORM was expressed both in terms of individual clinical features present on the second postoperative day (when the incidence was greatest), and as an aggregate score incorporating many clinical features. The importance of recognised risk factors, such as previous respiratory disease, cigarette smoking, upper abdominal procedures and the duration of surgery was confirmed, in that these factors were associated with some of the individual clinical features of PORM. The relative importance and independent contribution of these risk factors were assessed by their association with the aggregate score. A naso-gastric tube (NGT) present for 24 hours postoperatively was the factor more associated with PORM. The NGT identified patients at risk more clearly than, and independently of, the next most important factor, upper abdominal surgery. The duration of surgery did not contribute to PORM after the influence of NGT and site of surgery had been considered. Previous respiratory disease predisposed to PORM, and was best identified by, in order of importance, an observed productive cough, a reduced one second forced expiratory volume, and purulent sputum. After the incidence of these factors had been considered, cigarette smoking and a history of a chronic productive cough did not contribute further to PORM.