Impact of obesity on mortality differs based on ventilation or ECMO in ARDS

Key takeaways:

• Mortality among those undergoing mechanical ventilation was more likely with obesity vs. a normal BMI.
• The group with obesity receiving ECMO had decreased odds for mortality vs. the group with normal BMI.

BOSTON — Receipt of ventilation vs. extracorporeal membrane oxygenation in adults with obesity and acute respiratory distress syndrome changed the direction of odds for mortality, according to data presented at the CHEST Annual Meeting.

“This study is a step toward the principles of precision medicine, which emphasizes tailoring treatments based on individual patient characteristics,” Ishwari Chandran Iyer, MD, chief internal medicine resident at The Brooklyn Hospital Center, told Healio. “By exploring how obesity and possibly its phenotypes differentially affect outcomes in ARDS patients receiving mechanical ventilation compared to ECMO, we’re identifying a potential treatment pathway that may be more beneficial for a specific subset of patients.

“The findings suggest that obesity, rather than being a uniform risk factor for worse outcomes, can influence the response to different therapies,” Iyer said. “In the context of ARDS, this means that rather than using a one-size-fits-all approach, we can consider factors like BMI when deciding whether to initiate ECMO early in the course of treatment for ARDS patients.”

Using the 2016 to 2020 Nationwide Inpatient Database, Iyer and colleagues analyzed 61,009 adults with obesity (BMI > 30 kg/m²; mean age, 57 years) and 216,330 adults with a normal BMI (mean age, 62 years), all hospitalized for ARDS, to see how obesity impacts the odds for mortality and if the impact changes based on receipt of mechanical ventilation vs. ECMO.

Notably, researchers accounted for several variables in multivariate regression analysis: age, sex, race, tobacco use, coronary artery disease, diabetes mellitus, COPD, obstructive sleep apnea and history of stroke.

A greater number of patients with obesity underwent invasive mechanical ventilation vs. ECMO (15,260 patients vs. 8,269 patients).

Demographics/characteristics that appeared more frequently among those with vs. without obesity included female sex (51.27%), diabetes (49.47%) and OSA (17.24%), according to the abstract.

In contrast, researchers reported comparable proportions of white patients and patients with COPD in the group with obesity and the group with normal BMIs.

The group with obesity vs. normal BMI undergoing mechanical ventilation faced a significantly elevated likelihood for mortality (OR = 1.66; 95% CI, 1.05-2.63), whereas the group with obesity receiving ECMO faced a decreased likelihood for mortality vs. the group with normal BMI receiving ECMO (OR = 0.56; 95% CI, 0.28-1.11).

“The findings of this study were interesting, though not entirely novel, given the existing literature on the obesity paradox in ARDS,” Iyer told Healio. “While it is well-known that patients with obesity are at a higher risk for ARDS due to associated comorbidities like diabetes and coronary artery disease, the improved survival rates among those receiving ECMO align with recent studies that suggest obesity may confer protective advantages in ARDS.

“What was surprising, however, was the contrast in outcomes between the two treatment groups,” Iyer said. “In mechanically ventilated patients, obesity was linked to a significantly higher mortality rate, while those who received ECMO showed an increase in their odds of survival.”

Looking ahead, Iyer outlined three factors that should be considered in further research on this topic, with the first one being the impact of different obesity classes.

“Future studies can expand on the findings of our study by examining the outcomes with ECMO and invasive mechanical ventilation among a broader range of BMI categories,” Iyer told Healio. “It would also be valuable to analyze whether there is an interaction between respiratory function and the BMI spectrum.”

The second factor to be considered is fat distribution over BMI, Iyer said.

“Moving beyond BMI as a sole measure of obesity by incorporating metrics like waist circumference or waist-to-hip ratio could offer better insight into how fat distribution influences outcomes,” Iyer told Healio. “This could refine treatment approaches, especially for patients with central obesity, which has distinct metabolic effects compared to other fat distributions.”
The third and final factor is assessment of days to ECMO.

“Considering the number of days to initiating ECMO can be crucial in future studies as it would assist shaping future guidelines,” Iyer said.

“I am collaborating with my mentors in my sequential analysis,” Iyer added. “I intend to report additional results that will provide new clinical information.”

For more information:

Ishwari Chandran Iyer, MD, can be reached at ishwarichandran@gmail.com.