Obesity hypoventilation syndrome (OHS) is due to a mechanical load on the respiratory pump system and a blunted ventilatory response to CO2.

Pathophysiology of OHS

OHS can lead to biventricular heart failure, pulmonary hypertension.

Diagnosis of OHS

  1. Daytime hypercapnia (PaCO2 > 45 mmHg)
  2. Obesity
  3. Exclusion of other causes of hypoventilation

Treatment of OHS

  1. Weight loss is essential: Obesity management via lifestyle, pharmacotherapy, and surgery if indicated.
  2. CPAP is indicated for stable ambulatory patients with OHS and concomitant severe OSA (AHI > 30).
  3. BiPAP (+/- ST) or PSV is indicated for inpatients with OHS-related respiratory failure, which should be continued as an outpatient until the patient can be evaluated with a PSG and titrated with the appropriate PAP. Patients may need supplemental O2.

References

  1. MKSAP 19