Patients with ALI/ ARDSexp had higher maximum SOFA scores, but the ASOFA (signifying the new-onset organ dysfunction and/or organ failure) scores were similar in the two groups (Table 2). Similarly, there was no difference between the two groups in terms of the length of time to the first development of nonpulmonary organ dysfunction and organ failure (Table 2).
Figure 1 shows the Pa02/Fl02 scores and PEEP levels, and Figure 2 shows Cstat and Pplat values over the course of the hospital stay. Although the initial Pplat values (ie, day 0 to day 3) were higher in ALI/ARDSp patients than in ALI/ARDSexp patients, there were no significant differences in the progression of lung mechanics and gas exchange variables over time. Ninety-four of the 180 patients with ALI/ARDS were discharged from the hospital; there was no difference in hospital survival between the two categories of ARDS patients (ALI/ARDSp, 70 of 123 [56.9%]; ALI/ARDSexp, 24 of 57 [42.1%]). review
Logistic regression analysis was performed to study the effect of the category of ALI/ARDS on ultimate hospital survival. In the univariate model, the factors that predicted survival included female gender, ALI/ ARDSexp, SOFA score, and ASOFA score (Table 3). However, in the multivariate model, after adjustment, the only variables that predicted outcome were female gender, baseline SOFA scores, and ASOFA scores (Table 3); although there was a trend toward decreased hospital survival with ALI/ARDSexp, this was not statistically significant (OR, 1.6; 95% CI, 0.8 to 3.2).
Survival curves were plotted for patients with ALI/ARDSp and ALI/ARDSexp vis-a-vis the RICU stay (Fig 3). The median RICU stay in patients with ALI/ARDSp was 5 days (IQR, 6 days; range, 1 to 53 days) vs 5 days in patients without ALI/ARDSexp (IQR, 9.5 days; range, 1 to 64 days). The difference between the curves was analyzed using the log-rank test and was found to be statistically insignificant (p = 0.4) [Fig 3]. Only a few studies have investigated the prevalence of ALI/ARDSp and ALI/ARDSexp and the mortality of patients with those conditions. However, in the majority of available studies, as in the present study, the prevalence of ARDSp was higher compared to ARDSexp, although, in the most recent retrospective analysis of patients enrolled in the ARDS Network trial of low-tidal volume ventilation, roughly an equal proportion of ARDSp and ARDSexp patients were identified. In two stud-ies, patients with pulmonary trauma were reported to have a higher survival rate, whereas patients with opportunistic pneumonia, but not aspiration pneumonia, had a lower survival rate. However, the reported mortality rate in patients with ARDS that is attributable to pulmonary and ex-trapulmonary causes varies considerably, with one study suggesting increased mortality with direct pulmonary insult triggering ARDS, and another study finding no relationship between direct pulmonary insults and increased mortality.
Figure 1. Time course of PEEP levels (top) and Pao2/Fio2 scores (bottom) from baseline to day 7 in the two groups of patients. There were no significant differences in the two groups. Circles = mean values; error bar = SD.
Figure 2. Time course of Cstat scores and Pplat levels from baseline to day 7 in the two groups ofpatients. Although the Pplat levels were higher in patients in the pulmonary ARDS group than in those in the extrapulmonary ARDS group, these levels were not significant over time. Circles = mean; error bar = SD.
Figure 3. Timing of hospital discharge in patients with ALI/ ARDSp and ALI/ARDSexp (Kaplan-Meier analysis). There was no difference in length of RICU stay with ALI/ARDSp or ALI/ARDSexp (log-rank test).
Table 3—Risk Factors Affecting Outcome of ALI/ARDS Patients in the RICU (Multivariate Logistic Regression Model)
|Variables||Survivors (n = 94)||Nonsurvivors (n = 86)||Crude OR(95% CI)||Adjusted OR (95% CI)|
|Age,* yr Mean (SD)||41 (19)||45 (18)||1.01 (0.99-1.03)|
|Female sex,t||47 (50)||30 (34.9)||0.54 (0.29-0.98)|||0.49 (0.25-0.94)||
|ARDSexp patients,t||24 (25.5)||33 (38.4)||1.82 (0.96-3.43)§||1.6 (0.8-3.2)|
|Pplat at admission,* cm H2O||22 (6)||23(7)||1.02 (0.96-1.1)|
|PEEP at admission,* cm H2O||7(3)||8 (4)||1.1 (0.97-1.3)|
|SOFA score||||7 (2-18)||10 (3-21)||1.18(1.08-1.29)!||1.18(1.07-1.3)!|
|A SOFA score|||0 (0-8)||0.5 (0-15)||1.21 (1.07-1.36)!||1.24(1.09-1.41)!|
Age,* yr Mean (SD)