Extreme Obesity in the Intensive Care Unit

Abstract

Extreme obesity is currently a common medical condition. It is defined as having a body mass index (BMI) of >40 kg/m and is associated with an increased risk of mortality. A review of the clinical literature has shown that extreme obese patients are commonly admitted to the intensive care unit (ICU) for obstructive airway disease, pneumonia, and sepsis. A recent study found that patients with a BMI of >40 kg/m required greater mechanical ventilation and, therefore, a corresponding prolonged stay in the ICU. What are the other factors affecting the outcome of extreme obese patients in the ICU? In this issue of the Journal of Intensive Care Medicine, a new obesity-related condition among patients in the ICU with obesity hypoventilation syndrome (OHS) is now being described. The OHS is defined as the triad of obesity, daytime hypoventilation, and sleep-disordered breathing in the absence of an alternative neuromuscular, mechanical, or metabolic explanation for the hypoventilation episodes. Given this definition, a subtype condition has been identified in the extreme obese patients who had hypercapnic respiratory failure and multiorgan system dysfunction related to obesity, labeled as malignant obesity hypoventilation syndrome (MOHS). Marik and Desai coined this new term using a retrospective electronic chart review of 61 patients admitted to the ICU with a BMI of >40 kg/m and a PaCO2 greater than 45 mm Hg in patients admitted with hypercapnic respiratory failure. Supporting the description of MOHS, a statistical analysis of the documentation from this study confirmed the presence of multisystem disorder in extreme obesity by finding that 86% of the patients had congestive heart failure treated with diuretics, 71% had left ventricular failure, 61% had left ventricular diastolic dysfunction, 77% had pulmonary hypertension above 45 mm Hg, 90% had essential hypertension, and 64% had abnormal liver function tests and diagnosed with nonalcoholic steatohepatitis. Moreover, this retrospective study showed that based on the clinical documentation, these patients fit the clinical criteria for OHS, however, only 3 were diagnosed with this condition and the remaining (75%) were diagnosed with and treated for chronic obstructive lung disease (COPD). A primary question that arises after reading the study of Marik and Desai is ‘‘Are patients with extreme obesity admitted to the ICU with a diagnosis of COPD/asthma being misdiagnosed when in fact they could have unrecognized OHS?’’ It is known that patients with extreme obesity statistically have hypercapnic respiratory failure that increases the length of stay in the ICU due to prolonged necessity for mechanical ventilation. It is also well known that hypoventilation and oxygen disturbances are related to obesity even if there is no intrinsic lung disease. Therefore, mechanical ventilation in the extreme obese patient is one of many challenges clinicians face since the increase in the prevalence of obesity, with a corresponding increase in ICU admissions. It is very concerning that only 3 of 61 patients had a confirmed diagnosis of OHS. More interestingly, the management of extreme obese patients with bilevel positive airway pressure (BiPAP) in this study failed in 23% of the patients, thus requiring mechanical ventilation. This was an unexpected finding which highlights again the challenge of managing respiratory failure and the use of mechanical ventilation in extremely obese patients. What would have happened if OHS was part of the medical history of these patients admitted to the ICU? It is well known that extremely obese patients with concomitant untreated obstructive sleep apnea (OSA) present