Obesity Hypoventilation Syndrome
ICD-10 E66.2 · ICD-11 7A42.0

OHS with Obesity (BMI ≥30) and Severe OSA — When NIV Has Not Achieved Daytime CO₂ Targets

This protocol applies to patients with Obesity Hypoventilation Syndrome — obesity (BMI ≥30 kg/m²), daytime hypercapnia (arterial CO₂ ≥45 mmHg), and concomitant severe obstructive sleep apnoea (AHI ≥30 events/h) — in whom the preceding ventilatory approach did not reach its gas-exchange goals, or who are unable to tolerate PAP therapy.

Clinical Scenario

Obesity hypoventilation syndrome is defined by obesity (BMI ≥30 kg/m²), daytime hypercapnia (arterial CO₂ ≥45 mmHg), and sleep-disordered breathing. Nearly 70% of OHS patients have concomitant severe OSA (AHI ≥30 events/h). In this subgroup, PAP-based therapy is the established initial approach; however, a subset of patients cannot tolerate it or do not achieve adequate gas-exchange responses.

Previous Line — Goals Not Reached

Prior therapy: Noninvasive ventilation (NIV) delivered with bi-level pressure settings and PAP titration during sleep
Targets not met: Reduction in daytime arterial CO₂ tension and an increase in arterial O₂ tension, reassessed at approximately 2 months
This protocol describes the next step when NIV has failed to meet those gas-exchange targets, or when the patient cannot tolerate PAP.

Approach at This Line

A pharmacological class of respiratory stimulants that augment ventilation can be considered for patients who are intolerant of PAP therapy — used under close monitoring by specialised centres. The full selection criteria, specific agents, and monitoring requirements are in the structured protocol.

Instant Access to Structured Evidence-Based Regimens

References

  1. Obesity hypoventilation syndrome (OHS) is defined as a combination of obesity (body mass index ≥30 kg·m⁻²), daytime hypercapnia (arterial carbon dioxide tension ≥45 mmHg) and sleep disordered breathing, after ruling out other disorders that may cause alveolar hypoventilation. DOI: 10.1183/16000617.0097-2018
  2. Nearly 70% of patients have concomitant severe OSA (AHI ≥30 events·h⁻¹). DOI: 10.1183/16000617.0097-2018
  3. CPAP is considered the first-line treatment modality for OHS phenotype with concomitant severe obstructive sleep apnoea, whereas NIV is preferred in the minority of OHS patients with hypoventilation during sleep with no or milder forms of obstructive sleep apnoea (approximately <30% of OHS patients). DOI: 10.1183/16000617.0097-2018
  4. There are case report data and a small RCT assessing the role of respiratory stimulants, such as medroxyprogesterone and acetazolamide, which augment ventilation in patients with OHS and can be considered in patients intolerant of PAP. DOI: 10.1183/16000617.0097-2018
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