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

The aforementioned studies investigated small cohorts of mechanically ventilated patients, and their results were inconsistent. The main strength of the present study was its relatively large cohort, which was restricted to patients requiring mechanical ventilation. This enabled the development of an individualized mortality prediction score for this specific population. An interesting and unexpected finding of the present study was the lack of association between the degree of lung destruction, tuberculosis activity, or the level of PaCO 2 and increased mortality. Instead, the prognostic factors in the present cohort were age and evidence of organ failure (vasopressor use and PaO 2 /FiO 2 <180), as suggested in other patient populations. These risk factors are consistent with those reported in previous studies of active pulmonary tuberculosis with acute respiratory failure 3,20,21 , thus supporting the hypothesis that lower physiologic reserve and organ dysfunction, rather than the destroyed lung per se, are better predictors of mortality in mechanically ventilated TDL patients. A low serum albumin level also correlated with mortality in active pulmonary tuberculosis with acute respiratory failure 23 . In this study, nonsurvivors had lower levels of serum albumin than survivors, although this trend did not reach statistical significance. In the present cohort, the TDL-Vent score (both model 1 and model 2) was superior in terms of discriminating between survivors and non-survivors than either the APACHE II score or the SOFA score. In addition, the score from model 1 showed very high specificity in patients with the highest risk of mortality, thus limiting the possibility of misclassifying a patient as very high risk. This is crucial, as such a classification may result in the decision to withhold or withdraw life support. Lastly, the clinician is able to calculate the TDL-Vent score at the bedside, rather than relying on complicated formulas, smear tests, or chest X-rays.