Small airway testing and smoking in predicting risk in surgical patients

A prospective study was performed on 185 surgical patients without overt respiratory disease to determine whether three sensitive tests for early airway obstruction or cigarette smoking at the time of hospitalization were useful in identifying the patient at risk for a postoperative pulmonary complication. Subjects were evaluated by questionnaire. Pulmonary function testing consisted of the single breath nitrogen test (SBN2) to determine the closing volume (CV) and slope of the alveolar plateau, and a maximum expiratory flow volume curve (MEFV) to determine expiratory flow at low lung volumes. Fifty-five patients had upper abdominal surgery and 130 a major surgical procedure under general or spinal anesthesia upon another part of the body. Ninety-six (52%) of the 185 patients were smokers. Seventy-nine patients (43%) had one or more abnormal function parameters. The CV was abnormal in 59, alveolar plateau in 18, and MEFV in 12. Fifty-four percent of smokers and 30 percent of nonsmokers had abnormal small airway tests. Sixteen of 185 patients (8.6%) developed a postoperative respiratory complication determined by review of the hospital record. Eleven were in the 96 smokers, but 13 were in the 79 patients with abnormal small airway tests. The incidence was highest (38%) in smokers with an abnormal alveolar plateau who underwent upper abdominal surgery. Identification of the patient at risk was better served by tests of small airway abnormality than by smoking history alone.