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A clear, practical guide for UK patients who need supplemental oxygen alongside their sleep apnoea therapy covering how the combination works, the steps involved, and what to discuss with your clinical team.
For most people, CPAP therapy treats obstructive sleep apnoea effectively on its own. But for a growing number of patients those living with COPD, heart failure, obesity hypoventilation syndrome, or other conditions that affect blood oxygen levels prescribed supplemental oxygen is also part of the picture. When a clinician determines that both therapies are needed simultaneously, connecting a CPAP machine to an oxygen concentrator becomes a practical necessity.
This guide explains what that combination involves, how it is set up, and the important safety and clinical considerations that every patient should be aware of before making any changes to their respiratory equipment at home.
A home-based combined CPAP and oxygen therapy setup, used when sleep apnoea and low blood oxygen co-exist.
Why Some Patients Need Both CPAP and Supplemental Oxygen
CPAP therapy works by delivering a continuous stream of pressurised air through a mask, holding the airway open to prevent apnoea events. It does not enrich the oxygen content of that air beyond normal atmospheric levels (approximately 21% oxygen). For patients whose bodies cannot maintain adequate blood oxygen saturation on room air alone even with their airway held open additional oxygen supplementation is necessary.
The conditions most commonly associated with this need include:
- Chronic obstructive pulmonary disease (COPD) with co-existing sleep apnoea
- Heart failure with reduced cardiac output affecting oxygenation during sleep
- Obesity hypoventilation syndrome (OHS), where reduced breathing effort leads to low oxygen and high carbon dioxide levels
- Pulmonary fibrosis or other restrictive lung conditions
- Persistent nocturnal hypoxaemia identified during an overnight oximetry study or sleep study
The decision to prescribe supplemental oxygen alongside CPAP is always a clinical one. Your GP, respiratory consultant, or sleep medicine specialist will base this on oximetry data, lung function tests, and your broader medical history. If you have been prescribed both, your care team will typically provide initial guidance though the practical details of home setup are not always covered in depth.
Understanding How the Connection Works
An oxygen concentrator draws in ambient air and filters out nitrogen, delivering a concentrated stream of oxygen typically at 90–95% purity through an outlet port. A CPAP machine draws in ambient air separately and pressurises it for delivery through your mask.
To combine them, the oxygen concentrator's output is connected into the CPAP circuit, typically at one of two points:
Method 1: Inline Oxygen Enrichment via the CPAP Tubing
The most common approach uses a purpose-made oxygen enrichment adapter sometimes called an inline oxygen connector or bleed-in adapter. This small device fits between the CPAP machine's air outlet and the main flexible tubing. The oxygen concentrator's tubing connects to the adapter's secondary port, and the concentrated oxygen blends into the pressurised airstream before it reaches your mask.
This method is simple, compatible with most standard CPAP machines, and does not require any modification to the device itself. The oxygen flow rate typically set between 1 and 4 litres per minute is prescribed by your clinical team and dialled in on the concentrator.
Method 2: Mask-Level Oxygen Delivery
Some clinicians prefer oxygen to be introduced at the mask rather than in the tubing. Certain full face masks and some nasal masks include a dedicated oxygen inlet port a small, capped fitting on the mask body that accepts the concentrator's delivery tube directly. This approach can be appropriate when precise oxygen delivery at the airway is a priority, or when the patient's CPAP device and tubing configuration makes inline adapters impractical.
Not all masks include this port. If mask-level delivery is recommended, confirm with your equipment supplier which masks in your size and style are compatible.
Step-by-Step: Setting Up the Connection at Home
The following steps apply to the inline adapter method, which is the most widely used approach for home patients in the UK. Always follow the specific instructions provided by your equipment supplier or clinical team, as configurations can vary between device brands.
Oxygen-enriched air is highly flammable. Never use your CPAP and oxygen concentrator combination near open flames, lit candles, gas hobs, or in a room where anyone smokes. Ensure your bedroom has a working smoke alarm. If you smell burning or notice the equipment becoming unusually hot, turn both devices off immediately and contact your supplier.
Oxygen Flow Rate and Its Effect on Delivered Concentration
When oxygen is bled into a pressurised CPAP circuit, the final concentration of oxygen reaching your lungs depends on both the concentrator's flow rate and the CPAP pressure setting. Higher CPAP pressures dilute the blended oxygen more than lower pressures, because more total airflow is passing through the circuit.
This is why flow rate prescriptions for CPAP-combined oxygen use are typically calibrated differently from those used with simple nasal cannula oxygen therapy. Your clinical team should be aware of your CPAP pressure when prescribing the concentrator flow rate. If your CPAP pressure is subsequently adjusted for example, following a titration study report this to your respiratory team so that the oxygen prescription can be reviewed if necessary.
If you use an auto-titrating CPAP device (APAP) that varies pressure throughout the night, the effective oxygen concentration at your airway will fluctuate accordingly. Some clinicians prefer fixed-pressure CPAP for patients also receiving supplemental oxygen, as this makes the delivered oxygen concentration more predictable. Discuss this with your sleep medicine team if you are on auto-titrating therapy.
Monitoring Your Therapy at Home
Once the combined setup is in place, ongoing monitoring is an important part of safe, effective therapy. There are several practical ways to track whether the combination is working as intended.
Overnight Pulse Oximetry
A pulse oximeter worn on the finger overnight records your blood oxygen saturation (SpO₂) throughout the night. Your clinical team may ask you to carry out periodic oximetry checks at home and share the data at follow-up appointments. Target saturation levels are typically 88–92% for patients with COPD, or 94–98% for those without chronic lung disease your clinician will specify your individual target.
CPAP Device Data
Most modern CPAP devices record nightly data including AHI, leak rate, and usage hours. Reviewing this data either on the device's built-in display or via a connected app helps you confirm that therapy is running effectively and that the inline connection has not introduced significant additional leakage into the circuit.
Concentrator Performance Checks
Oxygen concentrators have filters that require regular cleaning typically weekly for the foam inlet filter. Most devices also have an audible alarm that sounds if oxygen output falls below an acceptable level. If an alarm sounds during use, stop therapy, remove your mask, breathe room air, and contact your equipment supplier or out-of-hours respiratory service.
When to Speak to Your Clinical Team
Combining two forms of respiratory therapy is not something to adjust independently at home. Contact your GP, respiratory nurse, or sleep clinic in the following circumstances:
- Your overnight oxygen saturation readings are consistently outside your prescribed target range
- You are waking frequently, feeling breathless on waking, or experiencing morning headaches (which can indicate raised CO₂ levels)
- Your CPAP data shows a significant increase in leak rate since adding the oxygen connection
- Your AHI has risen despite the equipment being in place and functioning
- You wish to travel and need guidance on portable oxygen concentrator options compatible with your CPAP therapy
- You are considering a mask change that may affect the oxygen delivery method
Travelling With Combined CPAP and Oxygen Therapy
Travel with a combined setup requires additional planning, particularly for air travel. Most airlines will not permit the use of a standard home oxygen concentrator on board. Portable oxygen concentrators (POCs) approved for aviation use such as those on the FAA-cleared or EASA-approved lists are available and may be compatible with CPAP therapy, though the flow delivery method (continuous versus pulse-dose) needs to be reviewed with your clinical team before travel.
For road and rail travel within the UK, a portable concentrator is typically far more practical than travelling with oxygen cylinders, which carry additional safety and logistics requirements. Always notify airlines, ferry operators, or rail providers in advance, and carry a copy of your oxygen prescription and a letter from your GP or respiratory specialist.
