When Oxygen Saturation Is Low: What to Do

What the number means

Oxygen saturation (SpO2) is the percentage of haemoglobin in the blood that is carrying oxygen. Healthy adults at rest typically show about 95 to 100 per cent. Falling below that range, called hypoxaemia, means the body may not be getting enough oxygen. Causes include chest infections and pneumonia, flare-ups of COPD or asthma, heart failure, blood clots in the lung, severe anaemia, sleep apnoea and other conditions. Often there are other signs such as breathlessness, fast breathing, cough or fever, though sometimes low oxygen is silent. See pulse oximeters: how they work and how to use one.

Different bodies give slightly different cut-offs, and a person with long-term lung disease may have a doctor-set target such as 88 to 92 per cent. In general:

• 95 per cent or above: usually reassuring if your parent looks well.
• 93 to 94 per cent, new and persistent: worth discussing with the doctor the same day, especially if symptoms exist.
• 92 per cent or below with symptoms, or below about 90 per cent at any time: seek urgent medical advice.
• Any reading with severe breathlessness, blue or grey lips, confusion, or drowsiness is an emergency.

These figures are general. Your doctor knows what is normal for your parent.

Step 1: check the reading is real

Many low readings are artefacts. Before worrying:

1. Have your parent sit upright and rest for five minutes. 2. Warm the hand by rubbing it or holding it in warm water, and dry it. 3. Remove nail polish or artificial nails from the finger. 4. Place the oximeter on the middle or index finger, nail up, with the hand resting on the chest or table at heart level. 5. Keep still and wait for a stable number and a steady waveform, if shown. 6. Try another finger or the other hand. 7. Check the battery; a weak battery can give odd readings.

See pulse oximeter accuracy: cold fingers, nail polish and skin tone for the common causes of false readings. But do not spend long on this if your parent looks unwell. If they are struggling to breathe, act first and check later.

Step 2: look at the person

The person matters more than the number. Ask and observe:

• Breathing: Is it fast, noisy, or laboured? Can they speak a full sentence? Are they using their shoulders or stomach muscles? Is there wheeze or a bubbling sound?
• Colour: Are lips, tongue or face blue, grey or very pale? Is the skin cold and clammy?
• Mental state: Are they confused, restless, unusually sleepy, hard to wake or behaving oddly? Low oxygen can show first as confusion in older people. See delirium in older adults.
• Pain: Is there chest pain, pressure or tightness?
• Fever, cough, sputum or recent illness?
• Swelling of feet or recent weight gain, which may suggest heart failure.
• Pulse: Very fast, very slow or irregular?
• Known conditions and medicines: COPD, asthma, heart disease, previous clots.

Step 3: decide what to do

Call 112 now (do not wait to recheck) if:

• Your parent is struggling to breathe, cannot speak in full sentences, or is gasping.
• Lips or face look blue or grey.
• There is chest pain or pressure.
• They are confused, very drowsy, hard to wake or collapse.
• The reading stays below about 90 per cent after a proper recheck.
• They have a known condition, such as heart or lung disease, and are rapidly worsening.

Call the doctor the same day if:

• The reading is 93 to 94 per cent or lower than usual on a proper recheck, even if your parent looks fairly well.
• There is new or worsening cough, breathlessness, fever or wheeze.
• Your parent is recovering from an infection and not improving.
• The reading is below the target the doctor gave.

Keep watching and recheck if the reading was a single low number that corrects on rewarming and re-testing, your parent is comfortable and nothing else is wrong. Record it and mention it at the next visit.

When in doubt, call. Older adults can deteriorate quickly.

What to do while waiting for help

• Sit your parent upright, leaning slightly forward, supported by pillows, with arms resting on a table or the chair back. This position helps breathing. Do not lie them flat.
• Loosen tight clothing and open a window for fresh air; if the room is hot or smoky, move to a cooler, cleaner space.
• Stay calm and reassure. Anxiety worsens breathlessness. Encourage slow breaths in through the nose and out through pursed lips, as in breathlessness: positions and breathing techniques that help.
• Use prescribed medicines as the doctor has instructed, such as a reliever inhaler for asthma or COPD, following the action plan. Do not take someone else's inhaler or give new medicines without a doctor's advice. See building a COPD action plan with your doctor.
• Use home oxygen only if it has been prescribed and you know the flow rate. Do not adjust the flow on your own; see oxygen flow rates and prescriptions. Never smoke or allow flames near oxygen.
• Do not give food or drink if breathing is laboured, because of the choking risk.
• Gather information for the responders: medicines, diagnoses, allergies, recent readings and temperature. A written one-page summary is ideal; see keeping a health record at home.
• Unlock the door and arrange for someone to meet the ambulance.
• Recheck the oximeter every few minutes if you can, noting the time and number, but do not delay seeking help to do it.

Chronic lung disease: different targets

People with COPD or other chronic lung disease may have normally lower saturation and, in some cases, are at risk if given too much oxygen. Their doctor may set a target range, often 88 to 92 per cent. Follow it. Do not self-prescribe oxygen. If readings fall below the target, call the doctor or follow the written action plan. See COPD at home guide.

Low oxygen after illness or at night

Some people have normal readings by day and low readings during sleep, as in sleep apnoea. Signs include loud snoring, pauses in breathing, morning headaches and daytime sleepiness. Checking oximeter readings at night is not routine; ask the doctor. See sleep apnoea in older adults. After pneumonia or other severe infection, a doctor may ask for home oximeter checks for a while. See home oxygen during recovery from pneumonia or severe infection.

Altitude, heat and pollution

At higher altitudes, such as hill stations, saturation may be lower than at sea level, and older adults with heart or lung disease may be more affected. Heavy air pollution can worsen lung conditions; see a pollution season plan for older adults. High heat and dehydration can worsen breathlessness. Talk to the doctor before travel to altitude.

Being prepared

• Keep a working oximeter with fresh batteries in an easy-to-reach box.
• Keep a list of the doctor's targets and 112 on the lid.
• Keep medicines, inhalers and spacer together and in date.
• Make sure family and household helpers know where the oximeter is and how to use it.
• Discuss with the doctor when to use home oxygen and how to arrange backup for power cuts; see oxygen at home and power cuts.
• Keep the hospital address and a transport plan, and know the nearest facility with a chest or emergency department.

When to ask a professional

Ask a doctor to set a personal target for your parent, to explain when to call and to show how to use any inhalers or oxygen. After any episode of low readings, arrange a medical review to find the cause. Call 112 for severe breathlessness, blue lips, confusion, chest pain or collapse, whatever the oximeter says. See also when breathlessness is an emergency.