Etiology and Outcomes of Pulmonary and Extrapulmonary Acute Lung Injury/ARDS in a Respiratory ICU in North India: Discussion

Etiology and Outcomes of Pulmonary and Extrapulmonary Acute Lung Injury/ARDS in a Respiratory ICU in North India: DiscussionIn our study, although patients with ALI/ARDSexp were younger and sicker (ie, higher baseline and maximum SOFA scores) than their ALI/ARDSp counterparts, we found no difference in the occurrence of new organ dysfunction/failure (ie, ASOFA scores), time to the development of the first organ dysfunction/organ failure, the duration of RICU stay, and length of hospital survival between the two categories of patients. Moreover, the classification of ARDS had no impact on the ultimate length of hospital survival after adjusting for various other risk factors like gender, baseline disease severity (ie, baseline SOFA scores), and the occurrence of new-onset organ dysfunction (ie, ASOFA scores). The lack of agreement among various studies can be explained by differences in baseline status, the prevalence of the disease precipitating ARDS in each center, the impact of therapy, and the overall distribution of these factors in the studied population. Another reason for the lack of agreement is probably the fact that the differentiation between direct and indirect insult is often straightforward only in patients with pneumonia or ARDS originating from intraabdominal sepsis, but a precise identification of the pathogenetic pathway is somewhat difficult to ascertain in other situations. Source
In our study, one interesting feature was the fact that women with ALI/ARDS had longer survival times, irrespective of the category or severity of the ARDS. A few studies have described gender differences in the occurrence of sepsis and ARDS and in the outcomes of patients with those conditions, with a higher incidence and poorer outcomes in men compared to women. Sex steroids probably play an important modulatory role in the regulation of immune function, and reports have shown that female sex hormones are immunostimulatory, whereas male sex hormones are immunosuppressive.
Although some more recent studies have shown that mortality secondary to ARDS has decreased, the mortality rate in this study was 48%; the reasons for higher mortality can probably be attributed to obvious differences in case mix, delays in the transfer of critically ill patients from the emergency department to the ICU because of the limited availability of beds, possible selection bias as sickest patients with multiple organ failure are admitted to the ICU, and other logistical reasons.
The strengths of this study include outcome analysis by the characterization of lung injury into pulmonary and extrapulmonary subsets, and the fact that the data from the developing world are sparse on this subject. The major limitations of our study include its retrospective nature and the small numbers of patients in each group. Also, there were significant differences in baseline characteristics between the two groups. Finally, because of the retrospective nature of the study, there were limitations in the collection of data set.
In conclusion, within the limitations of this study, the major factors that affect patient outcome were female gender, baseline disease severity, and the fresh development of organ dysfunction/failure in hospital. The category of lung injury (ie, from pulmonary or direct causes vs extrapulmonary or indirect causes) did not influence the length of ICU stay or the ultimate length of hospital survival time.

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