Improving Risk Stratification for Critically Ill Patients with Obesity

UH Innovations in Pulmonology, Critical Care & Sleep Medicine | Summer 2025

Respiratory failure and re-intubation following planned extubation in the intensive care unit (ICU) are associated with increased complications, longer hospital stays and higher mortality rates. Patients at greater risk include those over 65 years old, individuals with preexisting cardiac or respiratory conditions, or those with a body mass index (BMI) of 30 or higher. Additionally, patients with primary medical causes of respiratory failure, rather than those in trauma/surgical units, have higher rates of failure.

Zachary Strumpf, MD

“We are talking about patients who overwhelmingly have a cardiac/pulmonary cause of respiratory failure and are, by definition, at higher risk for extubation failure than those who are intubated for anesthesia or other reasons,” says Zachary Strumpf, MD, a pulmonologist and sleep medicine physician within the UH Division of Pulmonary, Critical Care, and Sleep Medicine, University Hospitals Cleveland Medical Center. “An interesting subset is patients with obesity, where we see some surprising findings that I think could help us improve risk stratification for all patients.”

Understanding the Obesity Paradox

Obesity affects pulmonary mechanics through reduced lung compliance, decreased functional residual capacity and increased risk for obstructive sleep apnea or other sleep-related breathing disorders. “Clinicians have rightly taken these obesity-related factors into account when considering timing of extubation and potential rescue therapies for patients who fail,” Dr. Strumpf says.

However, he highlights a curious phenomenon: the obesity paradox. Some studies show that, despite elevated risk profiles, patients with obesity have measured clinical outcomes similar to those of patients without an elevated BMI.

The counterintuitive finding that many critically ill patients with obesity have similar rates of favorable outcomes following extubation has been observed in various studies, particularly regarding length of ICU stay and in-hospital mortality. A secondary analysis of the multicenter, prospective FREE-REA study published in CHEST highlighted this obesity paradox, showing similar extubation failure rates regardless of BMI.

“One theory is that clinicians are highly attuned to the risks in this patient population,” Dr. Strumpf says. “They anticipate potential failure and may start rescue therapies sooner or more aggressively. The overall conclusion is that failure rates were not more common in patients with obesity because these patients received timely, aggressive support, such as increased use of non-invasive ventilation and early mobilization.”

Beyond BMI: Refining Risk Stratification

However, Dr. Strumpf explains that using BMI alone is overly simplistic from a risk stratification standpoint. An editorial by Phillip Simon and colleagues, published in the American Journal of Respiratory and Critical Care Medicine, introduced P/FBMI, a BMI-adjusted P/F ratio (partial pressure of oxygen in blood divided by the fraction of oxygen in the inspired air), as a more accurate method to classify severity of hypoxemia in patients with obesity.

“The P/F ratio is a common measure of hypoxemia severity,” he says, “But the authors suggest that standard P/F ratios may overestimate risk.” While P/FBMI has yet to be clinically validated, Dr. Strumpf notes that the authors highlight the need for improved risk-stratification tools.

Toward a Clinical Decision Support Tool

“We currently have ICU protocols in place to guide liberation from mechanical ventilation and post-extubation strategies in patients hospitalized with respiratory failure,” Dr. Strumpf says. “Bedside clinicians typically make specific intervention decisions using these protocols with the goal of safe, timely and successful liberation.”

Dr. Strumpf is leading an analysis of patient-level physiological and clinical data at University Hospitals, employing machine learning techniques to support a more advanced clinical risk assessment tool for use in University Hospitals’ ICUs. “We are working to identify patterns and signals associated with conditions such as sleep hypoventilation and sleep apnea, which are predictive of extubation failure in patients with and without obesity.”

This initiative is a collaboration with colleagues at the Case School of Engineering to develop and validate a clinical decision support tool that Dr. Strumpf and the research team hope will improve risk stratification and post-extubation outcomes. “Ultimately, doing so can advance the patients’ care to eventual discharge from the hospital,” he says.

For more information, contact Dr. Strumpf at Zachary.Strumpf@UHhospitals.org.

Contributing Expert:
Zachary Strumpf, MD
Pulmonologist and Sleep Medicine Physician
UH Division of Pulmonary, Critical Care, and Sleep Medicine
University Hospitals Cleveland Medical Center
Assistant Professor of Medicine
Case Western Reserve University School of Medicine