Evaluation and Management of Obesity Hypoventilation Syndrome

Publication Date: August 1, 2019

Last Updated: October 30, 2024

Objective

The purpose of this guideline is to improve early recognition of obesity hypoventilation syndrome in adults and to help inform better treatment decisions to improve patient outcomes.

Background

Obesity hypoventilation syndrome (OHS) is defined by the combination of obesity, sleep-disordered breathing, and awake daytime hypercapnia after all other causes for hypoventilation have been eliminated.
- Obesity is defined as having a body mass index of 30 or more.
- Sleep disordered breathing refers to a wide spectrum of sleep-related conditions including increased resistance to airflow through the upper airway, heavy snoring, reduction in airflow (hypopnea), and complete stoppage of breathing (apnea).
- Awake daytime hypercapnia is a condition where there is too much carbon dioxide in the blood when a person is awake and is characterized by an arterial partial pressure of carbon dioxide (PaCO2) greater than 45 mm Hg.
If untreated, OHS can lead to severe health issues, including heart failure, pulmonary hypertension, hospitalization, and more.
The treatment for OHS depends on a number of factors, including:
- Whether you have confirmed OHS, or if not, what the probability is that you have it
- Whether you are in the hospital
- Whether you have obstructive sleep apnea, and if so, whether is is mild, moderate or severe
- Whether you are experiencing respiratory failure

Diagnosis and Assessment

One of the most important steps in the management of OHS is diagnosing it as early as possible.
OHS is usually diagnosed with one or more of the following:
- Measurement of PaCO2
- Measurement of serum bicarbonate levels
Pulse oximetry (SpO2) is not yet established for diagnosing OHS.
Polysomnography or sleep respiratory polygraphy is required to determine the pattern of sleep-disordered breathing and hypoventilation (obstructive or non-obstructive), to tailor treatment, and to establish the optimal settings of positive airway pressure (PAP) therapy.
Before a diagnosis of OHS is made, providers must rule out all other possible causes of hypercapnia (high carbon monoxide levels in the blood).

Treatment Overview

The treatment for OHS depends on a number of factors, including:
- Whether you have confirmed OHS, or if not, what the probability is that you have it
- Whether you are in the hospital
- Whether you have obstructive sleep apnea, and if so, whether is is mild, moderate or severe
- Whether you are experiencing respiratory failure
OHS is usually managed with one or more of the following:
- Non-invasive ventilation
- Positive airway pressure (PAPPositive airway pressure (PAP) or continuous positive airway pressure (CPAP) treatment
- Weight loss, including bariatric surgery
Positive airway pressure has become the primary management option for controlling sleep-disordered breathing and reversing awake hypoventilation in OHS.

Specified Treatment for patients with certain conditions

For obese patients with sleep-disordered breathing with a high probability of having obesity hypoventilation syndrome, measuring PaCO2 rather than serum bicarbonate or SpO2 is suggested.
- PaCO2 (Partial pressure of carbon dioxide): A measurement of the amount of carbon dioxide in a person's blood. It also indicates how easily carbon dioxide can leave the body.
- SpO2 (peripheral oxygen saturation): A measurement of how much oxygen is in your blood, typically measured using a non-invasive pulse oximeter on the finger.
- Serum Bicarbonate Level: Bicarbonate levels are measured on a routine blood test to monitor how acidic the blood is

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For patients with low to moderate probability of having obesity hypoventilation syndrome it is suggested to use serum bicarbonate levels to decide when to measure PaCO2.

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For patients with serum bicarbonate <27 mmol/l, measuring PaCO2 may be skipped, since the diagnosis of obesity hypoventilation syndrome is very unlikely.
- In patients with serum bicarbonate ≥27 mmol/l, PaCO2 measurements may be needed to confirm or rule out the diagnosis of obesity hypoventilation syndrome.

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Using oxygen saturation by pulse oximetry (SpO2) during wakefulness should be avoided when deciding to measure PaCO2 in patients suspected of having OHS.

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For patients with OHS, weight-loss interventions that produce sustained weight loss of 25–30% of actual body weight are recommended. This level of weight loss is most likely required to achieve resolution of hypoventilation.

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For stable non-hospitalized patients diagnosed with obesity hypoventilation syndrome, treatment with PAP during sleep is suggested.

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For stable non-hospitalized patients diagnosed with obesity hypoventilation syndrome and co-occurring severe obstructive sleep apnea (apnea-hypopnea index ≥30 events/hour), 1st line treatment with CPAP therapy rather than non-invasive ventilation (NIV) is suggested.

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Hospitalized patients with respiratory failure suspected of having obesity hypoventilation syndrome should be started on non-invasive ventilation before being discharged from the hospital until they undergo outpatient workup and titration of PAP therapy in the sleep laboratory, ideally within the first 3 months after hospital discharge.

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Abbreviations

CPAP: Continuous Positive Airway Pressure
OHS: Obesity Hypoventilation Syndrome
PAP: Positive Airway Pressure
PaCO2: Partial Pressure Of Carbon Dioxide

Source Citation

Mokhlesi B, Masa JF, Brozek JL, et al. Evaluation and management of obesity hypoventilation syndrome. An official American thoracic society clinical practice guideline. Am J Respir Crit Care Med. 2019 Aug 1;200:e6-e24.

Disclaimer

The information in this patient summary should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.