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Home oxygen

A patient on home oxygen is usually at risk of hypercapnia. The danger in the ED is giving them too much, not too little.

AdultAirwayGuideline

Also called: LTOT, long-term oxygen therapy, oxygen concentrator, home oxygen cylinder, ambulatory oxygen, portable oxygen

What it is

Home oxygen is supplied as a concentrator (mains-powered, for long-term use at home), cylinders (portable or back-up), or occasionally liquid oxygen. It is prescribed for chronic hypoxaemia - most often COPD, but also interstitial lung disease, pulmonary hypertension, cystic fibrosis and other chronic lung disease.

The ED-relevant point is that a large share of home-oxygen patients are at risk of hypercapnic respiratory failure, so uncontrolled high-flow oxygen can raise their CO2 and drop their pH. Home oxygen is not a licence to give unlimited oxygen in a crisis - the target saturation still applies.

How to recognise it

What it gets confused with

Home ventilation controls breathing and CO2; home oxygen adds oxygen only. A hypercapnic patient's problem is often ventilation, not oxygenation, and more oxygen can make it worse. If the patient uses an overnight mask machine, that is ventilation, not oxygen.

Open that entry →

What goes wrong

Oxygen-induced hypercapnia

A COPD or other at-risk patient becomes drowsy and more acidotic after being given high-flow oxygen; the gas shows a rising CO2 and falling pH.

Red flag
This is iatrogenic and preventable. Bring the saturation down into the target range with a controlled device rather than removing oxygen abruptly, and recheck the gas.

Acute exacerbation of the underlying disease

Worsening breathlessness, cough, sputum change, hypoxia below the patient's usual level.

Red flag
Treat the exacerbation; the home-oxygen flow that keeps them comfortable at home may not be the right ED prescription during an acute illness.

Equipment or supply failure

Concentrator fault, empty cylinder, power cut affecting a mains concentrator.

Red flag
A genuinely oxygen-dependent patient who has lost their supply needs prompt replacement oxygen, titrated to target - not reflex high flow.

The first ten minutes

  1. Check an oxygen alert card first if the patient has one. The guideline: If a patient has an oxygen alert card, initial oxygen therapy should be based on the guidance on the card until the results of blood gases are available.
  2. Set a target saturation range, do not just turn oxygen up. The guideline target: Oxygen should be prescribed to achieve a target saturation of 94-98% for most acutely ill patients or 88-92% or patient-specific target range for those at risk of hypercapnic respiratory failure.
  3. For an at-risk patient before gases are back, the guideline specifies controlled delivery for those with risk factors for hypercapnia but no prior history of respiratory acidosis: use a 24% Venturi mask at 2-3 L/min or 28% Venturi mask at 4 L/min or nasal cannulae at 1-2 L/min and aim for an oxygen saturation of 88-92%.
  4. Get a blood gas to see whether the patient retains CO2, and adjust the target to 94-98% if the CO2 is normal - but note the guideline's caveat unless there is a history of previous NIV or IMV: a patient with prior ventilatory failure keeps their lower (88-92% or specialist) target even with an incidentally normal gas.
  5. Treat the underlying cause of the deterioration rather than treating the number in isolation.

Do not

Do not give uncontrolled high-flow oxygen to an at-risk patient.
In a patient at risk of hypercapnic respiratory failure, excess oxygen can raise CO2 and cause a respiratory acidosis. The target is a saturation range, delivered by a controlled device, not maximal oxygen.
Do not ignore an oxygen alert card.
The card records the patient's known safe range and prior hypercapnia. The guideline directs that initial therapy follow the card until blood gases are available.
Do not assume 'they are on home oxygen, so more is fine'.
Home oxygen is a long-term flow for chronic hypoxaemia, not an emergency prescription. During an acute illness the right flow is whatever hits the target saturation range, which may be more or less than their home setting.
Do not withhold oxygen from a hypoxic patient out of fear of CO2.
The danger is uncontrolled oxygen, not oxygen itself. A hypoxic at-risk patient still needs enough oxygen to reach 88-92% - titrate to the range rather than refusing it.

Who owns it

Acute management sits with the ED and acute medical / respiratory teams; the home-oxygen assessment service owns the long-term prescription. Tell the respiratory team the patient's usual flow and device, their target range or alert-card range, and the current gas.

Who to call

The team and the criteria are national. The phone number is local, and this tool does not know it. Find it once, now, and write it on the department's own card — that is the part no website can do for you.

Say the device name first
Open with laryngectomy, LVAD, shunt — the single word changes who comes and what they bring. Do not bury it in the history.
Say what you have already established
Whether the device is patent, whether it has been removed or disturbed, and what you have already tried. The specialist is deciding whether to walk or run.
Ask who owns it out of hours
Device ownership and the on-call route often differ from the implanting specialty, and it is frequently a regional centre rather than your own hospital.
The patient's own team is a resource, not an afterthought
Named nurse specialists, home-care companies and device helplines answer questions nobody else can, and the patient usually has the number.

When the device is not the problem

A patient with a device gets pneumonia, sepsis, pulmonary oedema and myocardial infarction at the same rate as everybody else. The device is the most visible thing about them and it attracts the whole assessment.

The NTSP says it out loud
The project's own manual warns that patients with tracheostomies can become unwell with all the problems that other patients get too. It is easy to become fixated with the tracheostomy. The same sentence applies to every device in this tool.
Clear the device, then leave it
Establish that the device is doing its job — the stoma is patent, the line draws back, the pump is running — and then assess the patient as you would anyone else.
The anchoring runs both ways
The opposite error is treating a device complication as a medical illness: a blocked gastrostomy read as vomiting, a baclofen pump failure read as sepsis.

What the patient will be carrying

Many at-risk patients carry an oxygen alert card stating their target saturation and whether they retain CO2. It is the single most useful piece of paper in the first minutes - ask for it.

Scope of this page

This page covers the ED oxygen decision in a patient who uses home oxygen: read the alert card, set a target saturation range, use controlled delivery for the at-risk patient, and confirm on a gas. It does not cover assessment for or prescription of long-term oxygen therapy, which is done by the home-oxygen service, nor the detailed management of the underlying lung disease.

Sources