Speaker's Highlight

• Don Sin University of British Columbia, St. Paul Hospital (Canada)
  Kenneth R. Chapman Toronto General Hospital Research Institute (Canada)
• Parameswaran Nair McMaster University (Canada)
  Carolyn Calfee UCSF (U.S.A.)
• Gregory P. Downey University of Colorado School of Medicine (U.S.A.)
  David A. Schwartz University of Colorado School of Medicine (U.S.A.)
• Neil Schluger Tuberculosis Control Branch, California Department of Public Health (U.S.A.)
  Nick Kim Critical Care & Sleep Medicine, University of California San Diego (U.S.A.)
• Nicola Hananiah Baylor College of Medicine (U.S.A.)
  Jae-Joon Yim Seoul National University College of Medicine (Republic of Korea)
• Koichiro Asano Tokai University School of Medicine (Japan)
  Diahn-Warng Perng Taipei Veterans General Hospital (Taiwan)
• Konstantinos Kostikas University of Ioannina (Greece)
  Karin Klooster University Medical Center Groningen (Kingdom of the Netherlands)

• Noninvasive ventilation for obesity-related breathing failure

  Obesity hypoventilation syndrome (OHS) occurs when excess body weight is associated with raised carbon dioxide levels during wakefulness, usually alongside sleep-disordered breathing. The condition can cause morning headaches, poor concentration, daytime sleepiness, breathlessness and repeated hospital admissions. It is different from uncomplicated snoring or obstructive sleep apnoea because the body is failing to remove enough carbon dioxide.

  Noninvasive ventilation (NIV) supports breathing through a mask rather than an invasive airway. Continuous positive airway pressure (CPAP) may be sufficient when obstructive events dominate, while bilevel positive airway pressure, commonly called bilevel PAP or BiPAP, provides separate inspiratory and expiratory pressures when ventilatory assistance is needed.

  For Australians, treatment may involve a GP, respiratory physician, sleep specialist, respiratory scientist and accredited home-care supplier. Access can vary between metropolitan services in Sydney, Melbourne or Brisbane and regional areas, so a clear diagnosis, a practical equipment plan and regular review are central to safe care.

  Why obesity changes breathing

  Fat around the chest and abdomen makes the respiratory system harder to expand. During sleep, muscle activity falls and the upper airway is more likely to narrow. In OHS, these effects combine with a reduced breathing response to carbon dioxide, leading to sustained nocturnal and daytime hypoventilation.

  A raised serum bicarbonate level can signal chronic carbon dioxide retention, although it is not a diagnosis by itself. Arterial or venous blood gases, overnight oximetry, polysomnography and lung function testing help distinguish OHS from severe COPD, neuromuscular disease, medication-related hypoventilation and other causes.

  Sleep apnoea commonly coexists with OHS, but an apparently modest apnoea-hypopnoea index does not exclude clinically important hypoventilation. Assessment should consider oxygen levels, carbon dioxide trends, sleep quality, fluid retention, pulmonary hypertension and the person’s ability to manage a mask independently.

  Selecting the right form of support

  CPAP is often considered first when severe obstructive sleep apnoea is present and daytime hypercapnia improves with control of upper-airway obstruction. It splints the airway open with one continuous pressure and is generally simpler, quieter and less expensive than bilevel equipment.

  Bilevel NIV is more appropriate when hypercapnia persists, CPAP is poorly tolerated, or there is significant ventilatory failure. It delivers higher inspiratory pressure and lower expiratory pressure, increasing tidal volume and reducing the work of breathing. Some devices add a backup rate when the person’s respiratory effort becomes unreliable.

  A sleep study and supervised titration help establish effective pressures without causing excessive leak, discomfort or central apnoeas. Oxygen should not be added casually: in a person retaining carbon dioxide, oxygen without adequate ventilation can worsen hypercapnia. Any supplemental oxygen needs a documented target and monitoring plan.

  Starting therapy safely

  Early education should cover mask fitting, humidification, cleaning, tubing position and what to do if the mask leaks. Nasal, nasal-pillow and oronasal masks suit different facial shapes and breathing patterns. Mouth breathing, nasal congestion, claustrophobia, skin sensitivity and dental work may require a different interface rather than abandonment of treatment.

  A gradual acclimatisation routine can help: wearing the mask while awake, using the device during a short rest, then progressing to overnight use. Heated humidification is valuable in dry indoor environments, while Australian coastal regions may require attention to condensation in tubing. Partners can help identify loud leaks, unusual breathing pauses or confusion on waking.

  Clinicians should review symptoms, usage hours, residual respiratory events, leak data and overnight oxygen or carbon dioxide measurements. Weight reduction, management of reflux and nasal disease, medication review and treatment of heart or lung disease complement ventilatory support. Respiratory teams also interpret evidence across complex comorbidity, including immunotherapy in oesophageal cancer, when coordinating care for patients with several active conditions.

  Approach	Typical use	Main benefit	Important limitation
  CPAP	OHS with prominent obstructive sleep apnoea	Simple airway splinting and broad familiarity	May not correct persistent daytime hypercapnia
  Bilevel PAP	Ongoing hypercapnia or ventilatory failure	Adds inspiratory assistance and reduces breathing effort	Requires careful titration and follow-up
  Bilevel PAP with backup rate	Unreliable spontaneous breathing or complex hypoventilation	Maintains a minimum respiratory rate	More complex settings and monitoring
  Supplemental oxygen	Documented hypoxaemia alongside effective ventilation	Raises oxygen saturation	Can worsen carbon dioxide retention if used alone

  Making treatment work at home

  Adherence is shaped by comfort, routine and confidence. A person who works early shifts may need to establish a consistent bedtime rather than rely on catching up at weekends. Travel between Melbourne and Perth, camping, or sleeping away from a reliable power supply requires advance planning, a suitable battery option and advice about device protection.

  Australian CPAP retailers and hospital loan programs offer different masks, machines and consumables, and private health cover varies. Medicare may cover clinical consultations and investigations under the relevant arrangements, but equipment costs and replacement schedules should be checked with the treating service and supplier. A written prescription and current settings are particularly useful when travelling.

  Weight management should be framed as part of respiratory care rather than a test of motivation. Dietitians, exercise physiologists and bariatric services can support gradual change, while clinicians should avoid stopping NIV simply because weight has begun to fall. Improvement needs objective confirmation with blood gases and sleep assessment.

  Oral health and airway care

  Dry mouth, nasal blockage and mask pressure can undermine consistent use. Saline rinses, prescribed nasal treatment, correct humidifier settings and regular dental care may improve comfort. A well-sealed mask should be firm without leaving persistent marks or causing pressure injury.

  Oral health also matters because inflammation, poor dentition and aspiration risk can complicate respiratory illness. The relationship between mouth disease and lung outcomes is relevant beyond OHS; discussion of periodontal disease and COPD illustrates why respiratory clinicians may include dental history in broader airway assessment.

  Avoiding alcohol close to bedtime and reviewing sedatives, opioids and sleeping tablets are important everyday measures. These substances can further suppress breathing or worsen upper-airway obstruction. Any medication change should be made with the prescribing clinician, particularly when chronic pain or anxiety is also present.

  Australian safety and follow-up

  A sudden increase in sleepiness, morning confusion, worsening breathlessness, blue lips, chest pain or inability to tolerate NIV needs urgent medical assessment. Acute decompensated OHS may require hospital-based NIV, blood gas testing and treatment of infection, heart failure or another trigger rather than a simple pressure adjustment at home.

  Driving deserves explicit attention. The Austroads medical standards for licensing require consideration of sleep disorders, excessive daytime sleepiness and crash risk. People with untreated or poorly controlled OHS should discuss private and commercial driving with their doctor and follow the relevant state or territory licensing requirements.

  Follow-up is especially important after hospital discharge, a major weight change, a new sedating medicine or a move between health services. Remote monitoring can identify poor use, but it does not replace clinical assessment when symptoms or carbon dioxide levels remain abnormal.

  Building a sustainable long-term plan

  Effective NIV is a partnership between physiology and daily life. The most suitable device is the one that corrects hypoventilation, is tolerated through the night and can be supported by local clinicians and equipment services. Regular checks should confirm that the original diagnosis still fits and that treatment targets remain appropriate.

  People living in hot northern cities such as Darwin may need extra attention to sweating, mask seal and bedroom cooling, while those in rural Australia may need longer lead times for servicing or replacement equipment. Keeping a spare mask, recording device settings and carrying a treatment summary can reduce disruption during travel or power outages.

  The practical takeaway is to treat persistent daytime carbon dioxide elevation as a medical problem requiring objective assessment, then match CPAP or bilevel NIV to the underlying breathing pattern and review its effectiveness over time.

  Richard Russell Nuffield Department of Clinical Medicine, University of Oxford (United Kingdom)
• Mona Bafadhel King’s College London (United Kingdom)
  David Jackson Guy’s and St Thomas’ Hospital, King’s College London (United Kingdom)
• James Chalmers University of Dundee (United Kingdom)
  David Price University of Aberdeen (United Kingdom)