Guidance

2 Obesity hypoventilation syndrome

2 Obesity hypoventilation syndrome

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Please note that the following guidance from the Driver and Vehicle Licensing Agency (DVLA) and the UK government is relevant to these recommendations:

Obesity hypoventilation syndrome (OHS) is defined as the combination of obesity (body mass index [BMI] of 30 kg/m2 or more), raised arterial or arterialised capillary carbon dioxide (CO2) level when awake, and breathing abnormalities during sleep, which may consist of obstructive apnoeas and hypopnoeas, or hypoventilation, or a combination of both. OHS is a specific form of chronic ventilatory failure.

2.1 Initial assessment for OHS

When to suspect OHS

2.1.1 Take a sleep history and assess people for OHS if they have a BMI of 30 kg/m2 or more with:

  • features of obstructive sleep apnoea/hypopnoea syndrome (OSAHS; see recommendation 1.1.1) or

  • features of nocturnal hypoventilation such as:

    • waking headaches

    • peripheral oedema

    • hypoxaemia (arterial oxygen saturation less than 94% on air)

    • unexplained polycythaemia.

For a short explanation of why the committee made this recommendation and how it might affect practice, see the rationale and impact section on when to suspect OHS.

Full details of the evidence and the committee's discussion are in evidence review A: when to suspect OSAHS, OHS and COPD–OSAHS overlap syndrome.

Assessment scales for suspected OHS

2.1.2 Use the Epworth Sleepiness Scale in the preliminary assessment of sleepiness in people with suspected OHS.

2.1.3 Do not use the Epworth Sleepiness Scale alone to determine if referral is needed, because not all people with OHS have excessive sleepiness.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on assessment scales for suspected OHS.

Full details of the evidence and the committee's discussion are in evidence review B: assessment tools for people with suspected OSAHS, OHS or COPD–OSAHS overlap syndrome.

2.2 Prioritising people for rapid assessment by a sleep service

See also recommendation 4.1.1 on providing information for people with suspected OHS who are being referred to a sleep service.

2.2.1 When referring people with suspected OHS to a sleep service, include the following information in the referral letter to facilitate rapid assessment:

  • results of the person's sleepiness score

  • how sleepiness affects the person

  • BMI

  • comorbidities

  • occupational risk

  • oxygen saturation and blood gas values, if available

  • any history of emergency admissions and acute non-invasive ventilation.

2.2.2 Within the sleep service, prioritise people with suspected OHS for rapid assessment if any of the following apply:

  • they have severe hypercapnia (PaCO2 [partial pressure of carbon dioxide] over 7.0 kPa when awake)

  • they have hypoxaemia (arterial oxygen saturation less than 94% on air)

  • they have acute ventilatory failure

  • they have a vocational driving job

  • they have a job for which vigilance is critical for safety

  • they are pregnant

  • they have unstable cardiovascular disease, for example, poorly controlled arrhythmia, nocturnal angina, heart failure or treatment-resistant hypertension

  • they are undergoing preoperative assessment for major surgery

  • they have non-arteritic anterior ischaemic optic neuropathy.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on prioritising people for rapid assessment by a sleep service.

Full details of the evidence and the committee's discussion are in evidence review C: prioritisation for rapid assessment at a sleep centre of people with suspected OSAHS, OHS or COPD–OSAHS overlap syndrome.

2.3 Diagnostic tests for OHS

See also section 4 on providing information for people who have been diagnosed with OHS.

Diagnosing OHS and assessing ventilatory failure

2.3.1 Consider measuring serum venous bicarbonate as a preliminary test if the pre-test probability of OHS is low. If bicarbonate levels are below 27 mmol/litre, OHS is unlikely.

2.3.2 Measure arterial or arterialised capillary blood gases when the person with suspected OHS is awake, to diagnose OHS and assess the extent of chronic ventilatory failure.

2.3.3 Do not delay treatment for acute ventilatory failure to carry out further investigations for OHS.

Diagnosing the presence of OSAHS or nocturnal hypoventilation in people with OHS

2.3.4 Offer respiratory polygraphy, either in hospital or at home, to determine the presence of OSAHS in people with suspected OHS.

2.3.5 Consider adding transcutaneous CO2 monitoring during sleep to respiratory polygraphy in people with suspected OHS to determine the extent of nocturnal hypoventilation and provide additional information to guide treatment.

2.3.6 Do not use oximetry alone to determine the presence of OSAHS in people with OHS.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on diagnostic tests for OHS.

Full details of the evidence and the committee's discussion are in evidence review D: diagnostic tests for OSAHS, OHS and COPD–OSAHS overlap syndrome.

2.4 Lifestyle advice for OHS

2.4.1 Discuss appropriate lifestyle changes with all people with OHS. Provide support and information on losing weight, stopping smoking, reducing alcohol intake and improving sleep hygiene tailored to the person's needs and in line with the NICE guidelines on:

For a short explanation of why the committee made this recommendation and how it might affect practice, see the rationale and impact section on lifestyle advice for OHS.

2.5 Treatments for OHS

See also section 4 on providing information for people starting treatment for OHS.

CPAP and non-invasive ventilation

People with OHS who do not have acute ventilatory failure

2.5.1 Offer continuous positive airway pressure (CPAP) to people with OHS and severe OSAHS as first-line treatment.

2.5.2 Offer non-invasive ventilation as an alternative to CPAP for people with OHS and severe OSAHS if symptoms do not improve, hypercapnia persists, apnoea–hypopnoea index (AHI) or oxygen desaturation index (ODI) are not sufficiently reduced or CPAP is poorly tolerated.

2.5.3 Consider non-invasive ventilation for people with OHS and nocturnal hypoventilation who do not have OSAHS, or in whom OSAHS is not severe.

2.5.4 Consider heated humidification in addition to CPAP for people with OHS and OSAHS and upper airway side effects such as nasal and mouth dryness, and CPAP-induced rhinitis.

People with OHS and acute ventilatory failure

2.5.5 Offer non-invasive ventilation to people with OHS with acute ventilatory failure:

  • If hypercapnia persists, consider continuing and further optimising non-invasive ventilation.

  • If hypercapnia resolves, consider stopping non-invasive ventilation and monitoring the response.

2.5.6 After a person with OHS and acute ventilatory failure has been stabilised on non-invasive ventilation with control of hypercapnia, consider:

  • stopping non-invasive ventilation and carrying out respiratory polygraphy and

  • a trial of CPAP in people with frequent episodes of obstructive apnoea and minimal hypoventilation.

    If the person decompensates after stopping non-invasive ventilation, offer to restart non-invasive ventilation.

Reducing the risk of transmission of infection when using CPAP or non-invasive ventilation

2.5.7 Be aware that CPAP and non-invasive ventilation are aerosol-generating procedures and, if there is a risk of airborne infection, such as COVID‑19, appropriate infection control precautions should be taken. These may include setting up the device at home by video consultation or with precautions in hospital.

For more information, see the UK government guidance on COVID-19: infection prevention and control and local guidance.

Oxygen therapy

2.5.8 Consider supplemental oxygen therapy with CPAP or non-invasive ventilation for people with OHS who remain hypoxaemic despite optimal control of nocturnal hypoventilation and AHI on CPAP or non-invasive ventilation, and address any additional underlying causes of hypoxaemia where possible.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on treatments for OHS.

Full details of the evidence and the committee's discussion are in evidence review F: positive airway pressure therapy variants for OSAHS, OHS and COPD–OSAHS overlap syndrome and evidence review I: oxygen therapy.

2.6 Managing rhinitis in people with OHS

2.6.1 Assess people with nasal congestion and OHS for underlying allergic or vasomotor rhinitis.

2.6.2 If rhinitis is diagnosed in people with OHS, offer initial treatment with:

  • topical nasal corticosteroids or antihistamines for allergic rhinitis or

  • topical nasal corticosteroids for vasomotor rhinitis.

2.6.3 For people with OHS and persistent rhinitis, consider referral to an ear, nose and throat specialist if:

  • symptoms do not improve with initial treatment or

  • anatomical obstruction is suspected.

2.6.4 Be aware that:

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on managing rhinitis in people with OHS.

Full details of the evidence and the committee's discussion are in evidence review K: rhinitis.

2.7 Follow-up and monitoring for people with OHS

2.7.1 Tailor follow-up to the person's overall treatment plan, which may include lifestyle changes and treating comorbidities. See the recommendations on tailoring healthcare services for each patient in the NICE guideline on patient experience in adult NHS services.

Follow-up for people using CPAP or non-invasive ventilation

2.7.2 Offer face-to-face, video or phone consultations, including review of telemonitoring data (if available), to people with OHS having non-invasive ventilation or CPAP. This should include:

  • an initial consultation within 1 month and

  • subsequent follow-up according to the person's needs and until optimal control of symptoms, AHI or ODI, oxygenation and hypercapnia is achieved.

2.7.3 When non-invasive ventilation or CPAP (with or without oxygen therapy) has been optimised for people with OHS and their symptoms are controlled, consider 6‑monthly to annual follow-up according to the person's needs.

2.7.4 Offer people with OHS having non-invasive ventilation or CPAP access to a sleep and ventilation service for advice, support and equipment between follow-up appointments.

Follow-up for drivers with excessive sleepiness

2.7.5 Ensure follow-up is in line with Driver and Vehicle Licensing Agency guidance on assessing fitness to drive.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on follow-up for people with OHS.

Full details of the evidence and the committee's discussion are in evidence review L: monitoring.

Monitoring treatment efficacy for people with OHS

2.7.6 Assess the effectiveness of treatment with CPAP or non-invasive ventilation in people with OHS by reviewing the following:

  • OHS symptoms, including the Epworth Sleepiness Scale and vigilance, for example, when driving

  • severity of OSAHS, using AHI or ODI

  • improvement in oxygenation and hypercapnia while awake and asleep

  • adherence to therapy

  • telemonitoring or download information from the device (if available).

2.7.7 Explore with the person their understanding and experience of treatment, and review the following:

  • mask type and fit, including checking for leaks

  • nasal and mouth dryness, and the need for humidification

  • other factors affecting sleep disturbance such as insomnia, restless legs and shift work

  • sleep hygiene

  • cleaning and maintenance of equipment.

2.7.8 For people with OHS having supplemental oxygen therapy, review whether this is still needed after treatment with non-invasive ventilation or CPAP has been optimised.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on monitoring treatment efficacy for people with OHS.

Full details of the evidence and the committee's discussion are in evidence review M: demonstration of efficacy.

2.8 Supporting adherence to treatment for OHS

2.8.1 Offer people with OHS educational or supportive interventions, or a combination of these, tailored to the person's needs and preferences, to improve adherence to CPAP and non-invasive ventilation.

2.8.2 Interventions to support adherence to treatment for OHS should be given by trained specialist staff when treatment is started and as needed at follow-up.

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on supporting adherence to treatment for OHS.

Full details of the evidence and the committee's discussion are in evidence review N: adherence.

  • National Institute for Health and Care Excellence (NICE)