Assessment and management of patients with obesity hypoventilation syndrome

Abstract

Obesity hypoventilation syndrome (OHS) is characterized by obesity, daytime hypercapnia, and sleep-disordered breathing in the absence of significant lung or respiratory muscle disease. Compared with eucapnic morbidly obese patients and eucapnic patients with sleep-disordered breathing, patients with OHS have increased health care expenses and are at higher risk of developing serious cardiovascular disease leading to early mortality. Despite the significant morbidity and mortality associated with this syndrome, diagnosis and institution of effective treatment occur late in the course of the syndrome. Given that the prevalence of extreme obesity has increased considerably, it is likely that clinicians will encounter patients with OHS in their clinical practice. Therefore maintaining a high index of suspicion can lead to early recognition and treatment reducing the high burden of morbidity and mortality and related health care expenditure associated with undiagnosed and untreated OHS. In this review we define the clinical characteristics of the syndrome and review the pathophysiology, morbidity, and mortality associated with it. Last, we discuss currently available treatment modalities.

Figure 1.

Prevalence of obesity hypoventilation syndrome (OHS) in patients with obstructive sleep apnea (OSA) by categories of body mass index (BMI) in the United States (10), France (15), and Italy. The data from Italy were provided by O. Resta (University of Bari, Bari, Italy). In the study from the United States the mean BMI was 43 kg/m² and 60% of the subjects had a BMI above 40 kg/m². In contrast, the mean BMI in the French study was 34 kg/m² and 15% of the subjects had a BMI above 40 kg/m². Consequently, OHS may be more prevalent in the United States compared with other nations because of its more exuberant obesity epidemic. Reprinted by permission from Reference .

Figure 2.

Mechanisms by which obesity can lead to chronic daytime hypercapnia.

Figure 3.

Survival curves for patients with untreated obesity hypoventilation syndrome (OHS) (n = 47; mean age, 55 ± 14 yr; mean body mass index [BMI], 45 ± 9 kg/m²; mean Pa_CO2, 52 ± 7 mm Hg) and eucapnic, morbidly obese patients (n = 103; mean age, 53 ± 13 yr; mean BMI, 42 ± 8 kg/m²) as reported by Nowbar and colleagues (21) compared with patients with OHS treated with noninvasive positive airway pressure (NPPV) therapy (n = 126; mean age, 55.6 ± 10.6 yr; mean BMI, 44.6 ± 7.8 kg/m²; mean baseline Pa_CO2, 55.5 ± 7.7 mm Hg; mean adherence with NPPV, 6.5 ± 2.3 h/d). Data for patients with OHS treated with NPPV were provided by S. Budweiser and colleagues (University of Regensburg, Regensburg, Germany) (27). Modified by permission from Reference .

Figure 4.

Management of patients with OHS requiring hospitalization because of acute-on-chronic hypercapnic respiratory failure. EPAP = expiratory positive airway pressure; ICU = intensive care unit; IPAP = inspiratory positive airway pressure; RR = respiratory rate; Sp_O2 = oxygen saturation by pulse oximetry.