Preoperative risk factors associated with mortality in lung biopsy patients with interstitial lung disease

The Objective of this study was to evaluate the risk factors associated with mortality in interstitial lung disease patients. We performed a retrospective study of 722 consecutive patients submitted for lung biopsy during the 1986-1990 period. Twenty-two (3%) died within the 30 days following surgery. Forty-four patients who survived after the surgery for the same time span were randomly chosen as control group. Dyspnea at rest was present in 18/44 of surviving group (SG) and in 18/22 of the nonsurviving group (NSG) (OR 6.5, 95% CI 1.8-22.4, p = .001). Systemic diseases (i.e., diabetes, systemic arterial hypertension) were mainly present in the NSG (OR 7.2, 95% CI 2.3-22.8, p < .001). The SG displayed significantly less respiratory insufficiency with a PaO2 of 52.2 +/- 8.4 versus 38.5 +/- 9.4 mm Hg, and PaCO2 of 28.8 +/- 4.5 versus 38.5 +/- 9.2 mm Hg, respectively (p < .001). Likewise, the SG exhibited a PaCO2/PaO2 ratio of 0.5+/-0.1, while in the NSG it was of 1+/-0.4 (p < .001), showing a sensitivity of 84% and specificity of 93% for mortality. Multiple logistic regression analysis for these variables showed that log likelihood was still significant for PaCO2 > 34 mm Hg, PaO2 < 48 mm Hg, and comorbid diseases. Logistic regression analysis of these three variables showed the greatest sensitivity and specificity (84 and 75%, respectively) for prediction of mortality. However, the strongest association was found when PaCO2/PaO2 ratio was analyzed alone (OR 21,073, CI 95% 28-15,946,357,p < .005). These data suggest that PaCO2/PaO2 ratio appears to be a predictor of mortality in this subset of patients. Its prospective use has reduced early mortality after surgery less than 1% in the last decade.