The effect of comorbidity on the prognosis of acute lung injury and acute respiratory distress syndrome.

Objective: We conducted a retrospective study assessing the relationship between comorbidity, using the Charlson Comorbidity Index (CCI), and the prognoses of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) patients.

Methods: We analyzed the data of 47 patients with ALI and ARDS who were admitted to our center between April 2004 and July 2009. The patients were classified into 2 groups (survival and non-survival) 3 months after diagnosis, and demographic and clinical characteristics were analyzed. We also evaluated the ROC curve and Akaike's information criterion (AIC) to determine the most appropriate cut-off level for the CCI at 3 months survival. The survival rate was estimated based on the AIC results.

Results: The mean age was 71.0 years; 25 (53%) of the patients died within 3 months of the diagnosis. Although age, etiology of ALI and ARDS, and APACHE II score did not differ between the two groups, smoking history, CCI, SOFA score, and steroid use were higher in the non-survival group than in the survival group. Age was not significantly correlated with CCI; however, CCI had weak, but statistically significant correlations with the APACHE II and SOFA scores (r=0.387, p<0.01 and r=0.288, p<0.05, respectively). AIC analysis revealed that a score of 4 on the CCI was the most appropriate cut off level for 3 months survival. The 3-month survival rate was lower in patients with a CCI≥4 than in those with a CCI<4 (9.5% vs. 55.5%, p<0.05).

Discussion: This study showed that the prognosis of ALI and ARDS was affected more by comorbidity than by age, and that the CCI was useful for assessing patient comorbidities in ALI and ARDS. We have to consider that patients with a CCI score of 4 or more are at risk of developing multi-organ failure and have a poor prognosis.