From the Guidelines
Obesity hypoventilation syndrome (OHS) should be treated with positive airway pressure therapy, with continuous positive airway pressure (CPAP) being first-line for most patients, as recommended by the American Thoracic Society 1.
Key Considerations
- OHS is defined by the combination of obesity (body mass index [BMI] > 30 kg/m2), sleep-disordered breathing, and awake daytime hypercapnia (awake resting PaCO2 > 45 mm Hg at sea level) 1.
- The treatment goals for OHS include improving gas exchange, reducing symptoms, and enhancing quality of life, with a focus on reducing morbidity and mortality.
- Weight loss is crucial for long-term management, with a goal of 25-30% reduction through dietary changes, increased physical activity, and possibly bariatric surgery for those with BMI >40 kg/m² or >35 kg/m² with comorbidities 1.
Treatment Approach
- CPAP therapy is recommended as the first-line treatment for stable ambulatory patients with OHS and coexistent severe obstructive sleep apnea (OSA) 1.
- For patients with severe hypercapnia or who don't respond to CPAP, bilevel positive airway pressure (BiPAP) may be necessary.
- Supplemental oxygen may be needed if hypoxemia persists despite positive airway pressure therapy.
- Medications like acetazolamide (250-500 mg twice daily) can help stimulate breathing in some cases.
Monitoring and Follow-up
- Regular follow-up with pulmonary function tests and arterial blood gases is essential to monitor progress and adjust treatment as needed.
- The underlying mechanism of OHS involves decreased respiratory drive, increased work of breathing due to excess weight on the chest wall, and sleep-disordered breathing that worsens gas exchange during sleep.
From the Research
Definition and Diagnosis of Obesity Hypoventilation Syndrome
- Obesity hyperventilation syndrome (OHS), also known as Pickwickian syndrome, is a respiratory consequence of morbid obesity, characterized by a combination of obesity, daytime hypercapnia, and sleep-disordered breathing 2, 3.
- The diagnosis is firmly established after arterial blood gases and a sleep study, with the presence of daytime hypercapnia explained by several co-existing mechanisms such as obesity-related changes in the respiratory system, alterations in respiratory drive, and breathing abnormalities during sleep 3.
Treatment and Management of OHS
- Non-invasive positive airway pressure (PAP) therapies and weight loss are commonly used to treat OHS, with continuous positive airway pressure (CPAP) considered the first-line treatment modality for OHS phenotype with concomitant severe obstructive sleep apnea 3.
- Noninvasive ventilation (NIV) is preferred in patients with hypoventilation during sleep with no or milder forms of obstructive sleep apnea, and is also used to treat acute-on-chronic hypercapnic respiratory failure 3, 4.
- The role of supplemental oxygen therapy in OHS is still uncertain, with some studies suggesting marginal changes and insufficient evidence to consider it globally beneficial or deleterious 5.
Prognosis and Outcomes of OHS
- Appropriate management of comorbidities, including medications and rehabilitation programs, is key to improving prognosis in patients with OHS 3.
- Weight loss alone may not improve hypoventilation and wean patients from non-invasive positive-pressure ventilation (NPPV), highlighting the need for a comprehensive assessment of hypoventilation, including monitoring of transcutaneous pressure of carbon dioxide (PtcCO₂) 2.
- PAP therapy during sleep has been associated with increased resolution of OHS, improvements in mortality, gas exchange, daytime sleepiness, sleep quality, quality of life, and emergency department visits, although the certainty in the estimated effects is low or very low for most outcomes 4.