From the Guidelines
Obesity hypoventilation syndrome (OHS) should be treated with positive airway pressure therapy, either continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP), and weight-loss interventions that produce sustained weight loss of 25% to 30% of actual body weight. OHS is a serious breathing disorder characterized by obesity (BMI >30 kg/m²) and daytime hypercapnia (elevated carbon dioxide levels in the blood) that cannot be attributed to other causes 1. The American Thoracic Society (ATS) recommends using positive airway pressure therapy, either CPAP or BiPAP, to treat OHS, with the goal of improving symptoms and reducing the risk of complications such as pulmonary hypertension, right heart failure, and increased mortality 1.
Key Recommendations
- For patients with severe OHS, initial BiPAP settings might start at inspiratory pressure of 12-16 cmH2O and expiratory pressure of 4-6 cmH2O, adjusted based on clinical response.
- Weight loss is crucial for long-term management, with a goal of 7-10% reduction in body weight through dietary changes and increased physical activity.
- Bariatric surgery may be considered for those with BMI >40 kg/m² or >35 kg/m² with comorbidities.
- Supplemental oxygen therapy may be needed if hypoxemia persists despite positive airway pressure.
Diagnosis and Screening
The ATS recommends measuring PaCO2 rather than serum bicarbonate or SpO2 to diagnose OHS in patients with a high pretest probability of having OHS 1. For patients with low to moderate probability of having OHS, a serum bicarbonate level < 27 mmol/L can be used to exclude the diagnosis of OHS, while a level > 27 mmol/L may require further testing with arterial blood gases 1.
Treatment Outcomes
The goal of treatment is to improve symptoms, reduce the risk of complications, and improve quality of life. Weight loss is a critical component of treatment, with a goal of 25% to 30% of actual body weight, which is most likely to be achieved with bariatric surgery 1. By prioritizing morbidity, mortality, and quality of life, healthcare providers can develop effective treatment plans for patients with OHS.
From the Research
Definition and Mechanisms of Obesity Hypoventilation Syndrome
- Obesity hypoventilation syndrome (OHS) is a sleep disorder characterized by insufficient sleep-related ventilation, resulting in abnormally elevated arterial carbon dioxide pressure (PaCO2) during sleep and demonstration of daytime hypoventilation 2.
- The primary mechanisms that can generate diurnal hypoventilation in obese patients include alteration of the respiratory mechanics secondary to obesity, central hypoventilation secondary to leptin resistance, and sleep disorder with sleep hypoventilation and obstructive apnoeas 2.
Treatment Options for OHS
- Non-invasive positive airway pressure (PAP) therapy, including non-invasive ventilation (NIV) and continuous positive airway pressure (CPAP), is a common treatment for OHS 2, 3, 4.
- The choice between NIV and CPAP as the initial treatment for OHS is uncertain, with some studies suggesting similar effectiveness in improving gas exchange, sleep quality, and quality of life 3, 4.
- A systematic review and meta-analysis found no significant difference in mortality, cardiovascular events, and healthcare resource use between patients with OHS treated with NIV or CPAP 4.
Efficacy of NIV in OHS without Severe Obstructive Sleep Apnea
- NIV has been shown to be effective in improving daytime PaCO2, sleepiness, and polysomnographic parameters in patients with OHS without severe obstructive sleep apnea (OSA) 5.
- A randomized controlled trial found that NIV led to a significantly larger improvement in PaCO2 and serum bicarbonate compared to lifestyle modification in patients with OHS without severe OSA 5.