Obesity Hypoventilation Syndrome

A serious breathing disorder in people with obesity in which the body cannot ventilate properly, raising carbon dioxide, lowering oxygen and straining the heart and lungs.

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Overview

Obesity hypoventilation syndrome (OHS) is a breathing disorder in which people with obesity do not breathe deeply or often enough, causing carbon dioxide to build up in the blood during the day as well as at night. It is defined by obesity (a BMI of 30 or higher), an elevated daytime carbon dioxide level, and the absence of another cause such as lung or neuromuscular disease (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019).

OHS is a more serious condition than obstructive sleep apnea, although about 90% of people with OHS also have sleep apnea. It is estimated to affect roughly 10% to 20% of people with obesity who are referred for sleep apnea evaluation, and it is frequently undiagnosed until a hospital admission for respiratory failure (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019). Untreated, OHS carries a high risk of heart failure, pulmonary hypertension, hospitalization and early death.

Treatment combines positive airway pressure, usually CPAP or noninvasive ventilation, with substantial weight loss, which addresses the underlying cause.

Causes

Excess weight on the chest and abdomen, which makes breathing harder and reduces lung volumes
Blunted breathing drive in response to carbon dioxide
Leptin resistance, which may impair the brain's breathing control
Obstructive sleep apnea, which causes repeated drops in breathing during sleep

Risk Factors

Severe obesity, especially a BMI above 40
Obstructive sleep apnea, particularly when severe; see sleep apnea
Sedative and opioid medications
Hypothyroidism

Who It Affects

OHS mainly affects adults with severe obesity and is often first diagnosed during a hospital stay for breathing problems or heart failure.

Complications

Acute respiratory failure
Pulmonary hypertension and right heart failure
Fluid retention and leg swelling
Higher risk with anesthesia and sedation
Increased mortality when untreated (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019)

Symptoms

Severe daytime sleepiness
Shortness of breath with minimal exertion
Morning headaches
Loud snoring and witnessed breathing pauses
Leg swelling
Confusion or depressed mood

Diagnosis

Arterial blood gas showing daytime carbon dioxide above 45 mm Hg (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019)
Serum bicarbonate: a normal level makes OHS unlikely and can be used as a screening test (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019)
Sleep study to assess sleep apnea and nighttime breathing
Lung function tests and chest imaging to exclude other causes
Echocardiogram for pulmonary hypertension

Differential Diagnosis

Chronic obstructive pulmonary disease (COPD)
Neuromuscular disease
Chest wall disorders
Hypothyroidism
Sedative or opioid effects

Lifestyle Modifications

Use positive airway pressure every night.
Pursue substantial weight loss, the most effective long-term treatment (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019).
Avoid alcohol, sedatives and opioids.
Increase activity gradually as breathing improves.

Treatment Options

CPAP as first-line therapy for stable patients with OHS and severe sleep apnea; in the Pickwick trial, CPAP and noninvasive ventilation produced similar long-term outcomes in these patients (Masa et al., Pickwick trial, Lancet, 2019)
Noninvasive ventilation (BiPAP) for patients without severe sleep apnea or who do not improve on CPAP
Weight loss targeting 25% to 30% of body weight, which guidelines suggest is needed to resolve hypoventilation; bariatric surgery is often the most effective way to achieve this (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019). See bariatric surgery.
Medical weight loss with GLP-1 medications or tirzepatide; see medical weight loss
Careful perioperative planning, since patients with OHS need special monitoring around anesthesia

When to See a Doctor

See a doctor if you have obesity and severe daytime sleepiness, shortness of breath with minimal activity, morning headaches or leg swelling.

When to Seek Treatment

Seek emergency care for severe shortness of breath, confusion, extreme drowsiness or bluish lips.

Long-Term Outlook

Long-term success depends on nightly therapy and sustained weight loss. Patients who lose substantial weight should be re-evaluated, as their breathing support may be reduced or discontinued.

Prognosis

With consistent positive airway pressure therapy and weight loss, carbon dioxide levels improve, hospitalizations fall and survival improves. Large weight loss can resolve OHS in many patients (Mokhlesi et al., ATS Clinical Practice Guideline, American Journal of Respiratory and Critical Care Medicine, 2019).

Why Choose Dr. de la Cruz-Muñoz

Patients with obesity hypoventilation syndrome need careful preparation for surgery and substantial, durable weight loss. Dr. de la Cruz-Muñoz is a board-certified metabolic and bariatric surgeon whose team coordinates with pulmonary and sleep specialists to optimize breathing before surgery and offers the operations most likely to achieve the large weight loss needed to resolve hypoventilation.

Patients with obesity hypoventilation syndrome deserve a surgeon with deep bariatric experience. Dr. de la Cruz-Muñoz has completed more than 9,000 bariatric operations in over 25 years, a volume few surgeons reach.