Predicting Mortality in Patients with Tuberculous Destroyed Lung Receiving Mechanical Ventilation

Kim, Won-Young; Kim, Mi-Hyun; Jo, Eun-Jung; Eom, Jung Seop; Mok, Jeongha; Kim, Ki Uk; Park, Hye-Kyung; Lee, Min Ki; Lee, Kwangha

Baseline characteristics of the study cohort are shown in Table 1. Nonsurvivors were older. No significant difference was found between survivors and nonsurvivors in terms of sex, body mass index, smoking status, or comorbidities. Mechanical ventilation was primarily due to pneumonia in 54% (48/89) of survivors and 69% (25/36) of non-survivors (p=0.11). Nonsurvivors had significantly higher APACHE II and SOFA scores and had a higher rate of vasopressor use within 24 hours of ICU admission. Active infection was found in 44 (35%) of the cohort, with no significant difference being found between survivors and non-survivors. The following pathogens were considered to be associated with pneumonia: methicillinresistant Staphylococcus aureus (n=14); Acinetobacter (n=9); Mycobacterium tuberculosis (n=6); Pseudomonas (n=5); extended-spectrum beta-lactamase-producing organism (n=4); Klebsiella pneumoniae (n=3); Stenotrophomonas (n=3); and Aspergillus species (n=3). The median arterial partial pressure of oxygen (PaO 2 )/fraction of inspired oxygen (FiO 2 ) ratio was significantly lower in non-survivors. Compared with survivors, non-survivors had numerically lower serum albumin and higher BNP, although the results were not statistically significant. Survivors and non-survivors had similar median field scores. Pulmonary function test results were available for 54 (43%) of the cohort. The median FEV 1 /FVC ratio was <0.70, and no significant differences between survivors and nonsurvivors were found for median FVC and FEV 1 . Echocardiographic findings were available for 64 (51%) of the cohort. Cor pulmonale was diagnosed in nearly half of the patients. However, the survivor and non-survivor groups showed no difference in terms of left ventricular systolic function or the proportion of patients with high RV systolic pressure. Clinical outcomes in the cohort are shown in Table 2 . Table 3 shows the results of the univariate and multivariate analyses of risk factors predicting ICU mortality. The following cut-off values were identified via inspection of locally weighted scatterplot smoothing curves: age ≥65 years, PaO 2 /FiO 2 ratio <180, PaCO 2 <52 mm Hg, serum albumin <3.0 g/dL, BNP ≥330 pg/mL, and field score ≥2 (Supplementary Figure S1) . Based on the β coefficient values observed in model 1, a TDL-Vent score comprising the following factors was proposed: (1) age ≥65 years (+1 point); (2) vasopressor use (+1 point); and (3) PaO 2 /FiO 2 ratio <180 (+1 point). This model had acceptable discrimination (AUC, 0.74) and calibration (Hosmer and Lemeshow chi-square, 14.74; p=0.06). Figure 1A shows the Kaplan-Meier survival curves, as stratified according to the TDL-Vent score. The 60-day mortality rates for scores ranging from 0 to 3 were 11%, 27%, 30%, and 77%, respectively (logrank test, p<0.001). The AUC of the TDL-Vent score for predicting ICU mortality was 0.72 (95% confidence interval [CI], 0.63-0.80). This was larger than the AUC for the APACHE II score (0.63; 95% CI, 0.54-0.72) and SOFA score (0.62; 95% CI, 0.53-0.71) (Figure 2 ). The cut-off score for predicting mortality based on the maximum Youden' s index was ≥2, with a sensitivity of 44% and a specificity of 93%.