Chest
Volume 149, Issue 3, March 2016, Pages 856-868
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Contemporary Reviews in Sleep Medicine
Obesity Hypoventilation Syndrome: Weighing in on Therapy Options

https://doi.org/10.1378/chest.15-0681Get rights and content

Obesity hypoventilation syndrome is becoming an increasingly encountered condition both in respiratory outpatient clinics and in hospitalized patients. The health consequences and social disadvantages of obesity hypoventilation syndrome are significant. Unfortunately, the diagnosis and institution of appropriate therapy is commonly delayed when the syndrome is not recognized or misdiagnosed. Positive airway pressure therapy remains the mainstay of treatment and is effective in controlling sleep-disordered breathing and improving awake blood gases in the majority of individuals. Evidence supporting one mode of therapy over another is limited. Both continuous and bilevel therapy modes can successfully improve daytime gas exchange, with adherence to therapy an important modifiable factor in the response to treatment. Despite adherence to therapy, these individuals continue to experience excess mortality primarily due to cardiovascular events compared with those with eucapnic sleep apnea using CPAP. This difference likely arises from ongoing systemic inflammation secondary to the morbidly obese state. The need for a comprehensive approach to managing nutrition, weight, and physical activity in addition to reversal of sleep-disordered breathing is now widely recognized. Future studies need to evaluate the impact of a more aggressive and comprehensive treatment plan beyond managing sleep-disordered breathing. The impact of early identification and treatment of sleep-disordered breathing on the development and reversal of cardiometabolic dysfunction also requires further attention.

Section snippets

Why Does OHS Occur?

On first consideration, it may seem obvious that changes in lung mechanics associated with obesity would explain the emergence of daytime hypoventilation through simple changes in ventilation. Individuals with OHS exhibit more pronounced decreases in lung volumes, more impaired respiratory muscle performance, and greater reductions in respiratory system compliance compared to those with eucapnic obesity.5 These changes are at least in part attributable to a more central pattern of fat

Consequences of OHS

The early identification and treatment of OHS is considered crucial given the significant health and social consequences experienced by these individuals. Systemic inflammation, endothelial dysfunction, and insulin resistance are more pronounced in people with OHS compared with eucapnic obesity,21 resulting in the development of an array of cardiovascular and metabolic morbidities some years prior to definitive diagnosis and treatment.3 Pulmonary hypertension is both more prevalent and of

Screening and Diagnosis of OHS

Given the high morbidity and mortality associated with OHS compared with eucapnic obesity with or without OSA, recognition and early intervention is considered critical. The prevalence of OHS in the general population is currently unknown, although estimates based on obesity and OSA rates suggest 0.3% to 0.48% of the general adult population may be affected.31, 32 Among obese individuals, the prevalence of OHS ranges from around 8% in premenopausal women being evaluated for bariatric surgery33

Treatment Options

The goals of therapy in OHS are to reverse the major physiologic abnormalities giving rise to the disorder, namely to normalize breathing during sleep, reduce weight, and improve respiratory drive. PAP therapy remains firstline treatment, providing the most immediate improvements in nocturnal gas exchange. However, the impact of PAP therapy on cardiovascular complications and mortality in OHS appears limited, highlighting the importance of a more comprehensive long-term management approach in

PAP Therapy

The goal of PAP therapy in stable OHS is to normalize breathing during sleep, consolidate sleep, and improve nocturnal gas exchange. Since upper airway obstruction is very common in OHS, not surprisingly, CPAP therapy effectively controls sleep-disordered breathing and reverses daytime respiratory failure in 50% to 80% of individuals presenting to sleep laboratories.20, 31, 53 In addition to maintaining upper airway patency, the volume-inflating effect of CPAP improves oxygenation through

Managing Acute Respiratory Failure

While the majority of patients with OHS present through respiratory and sleep clinics with chronic respiratory failure, 30% to 70% of individuals will be first diagnosed during an acute hospitalization with respiratory decompensation.29, 60, 69 Unfortunately, it may take a number of acute presentations before a correct diagnosis and appropriate management plan is put in place.9, 26 No randomized trials comparing different forms of PAP therapy for decompensated respiratory acidosis have been

Weight Loss

Significant improvements in awake CO2 and lung volumes can be achieved with sufficient weight loss,73 and a weight reduction program should be incorporated into the long-term management of individuals with OHS. Surgical approaches are more effective than conservative options in maximizing and maintaining weight loss.74 Although few studies have specifically enrolled patients with OHS undergoing bariatric surgery, significant improvements in gas exchange, sleep apnea, lung volumes, and pulmonary

Tracheostomy

Nowadays, tracheostomy is rarely used for the treatment of OHS although it should be considered for patients intolerant of PAP therapy and where other treatment options such as significant weight loss are not feasible. Significant risks and complications are associated with tracheostomy in the morbidly obese including obstruction of the tube by soft tissue and displacement of the tube out of the tracheal lumen, in addition to the usual physical and social consequences of tube placement. Few

Pharmacotherapy

Improved respiratory drive can be achieved pharmacologically and there are a small number of reports of respiratory stimulants being used successfully in the short-term. In postmenopausal women with sleep-disordered breathing, 2 weeks of medroxyprogesterone improved nocturnal oxygen saturation and reduced CO2 compared with a placebo group.80 Furthermore, CO2 was lower than when the subjects were using overnight CPAP, with stimulatory effects maintained at least 3 weeks after ceasing medication.

Conclusions

OHS is a complex, multifactorial disorder necessitating a comprehensive management approach. Although PAP therapy can effectively abolish sleep-disordered breathing, unload the respiratory muscles, reduce the work of breathing, and improve ventilatory drive, it appears to have little impact on the excess cardiovascular risk and comorbidity associated with persisting obesity.28, 52 As OHS is associated with a more extreme inflammation and greater endothelial dysfunction than eucapnic obesity,21

Acknowledgments

Financial/nonfinancial disclosures: A. P. has received speaking fees from ResMed, Philips Respironics (Koninklijke Philips NV), Novartis AG, and SenTec AG and reimbursement for travel costs from SenTec AG. A. P. also received a grant from the ResMed Foundation to study PAP therapy in obesity hypoventilation syndrome.

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