Oxygen Therapy

Oxygen therapy is a treatment in which a patient breathes air that contains more oxygen than normal room air, in order to raise the level of oxygen in the blood.

Healthy lungs pull oxygen from the air and pass it into the bloodstream, where it travels to every organ in the body. When the lungs or heart are not working properly, the blood can carry too little oxygen — a state doctors call hypoxemia (low blood-oxygen level). Oxygen therapy corrects this by delivering a higher concentration of oxygen through a mask, a tube placed under the nose (called a nasal cannula), or, in serious cases, through a breathing machine called a ventilator.

Oxygen therapy is used whenever a patient's blood-oxygen level falls below a safe range, or when the body is working so hard to breathe that extra oxygen relieves the strain. It is prescribed for short-term emergencies as well as long-term, ongoing care at home.

• COPD (chronic obstructive pulmonary disease — a long-term condition that blocks airflow in the lungs), including emphysema and chronic bronchitis
• Pneumonia (a lung infection that fills the air sacs with fluid)
• Severe asthma attacks that do not respond quickly to other treatments
• COVID-19 or other viral infections causing breathing difficulty
• Heart failure, when the heart cannot pump enough blood to keep oxygen levels normal
• Pulmonary fibrosis (scarring of the lung tissue that makes breathing harder over time)
• Sleep apnea (repeated pauses in breathing during sleep) in selected cases
• Recovery after major surgery or a serious injury
• Carbon monoxide poisoning, where oxygen helps flush the harmful gas out of the blood
• Cluster headaches (severe, one-sided head pain), in which high-flow oxygen can abort an attack

Oxygen therapy is not suitable for every patient with breathing difficulties. Doctors carefully check blood-oxygen levels before prescribing it, because giving too much oxygen to certain patients — particularly those with advanced COPD — can actually reduce the drive to breathe and cause harm. It is also not used as a general energy booster or wellness treatment in healthy people whose oxygen levels are already normal.

• Patients whose blood-oxygen level is already within the normal range
• People seeking oxygen for fatigue or stress without a diagnosed medical condition
• Certain COPD patients who retain carbon dioxide (CO₂) — these patients need carefully controlled, low-flow oxygen rather than high-flow oxygen

When used correctly and at the level prescribed by a doctor, oxygen therapy is generally very safe; most unwanted effects come from giving too much oxygen or from the equipment itself rather than from oxygen at the right dose.

• Dry or irritated nose and throat — the most common complaint, especially with nasal cannulas; a humidifier attached to the oxygen supply usually helps
• Skin soreness or pressure marks where the mask or cannula rests against the face
• Nosebleeds caused by dry nasal passages
• Headache, particularly if oxygen flow is higher than needed
• Oxygen toxicity (damage to the lungs or other organs from breathing too high a concentration of oxygen for too long) — this is rare at the doses used in standard care but is monitored carefully in intensive settings
• Hypercapnia (a build-up of carbon dioxide in the blood) in patients with advanced COPD who are given too much oxygen — this is why flow rates are individually set and monitored
• Fire hazard — oxygen makes fires burn more intensely; patients using home oxygen are advised to keep away from open flames, candles, and smoking

Preparation for oxygen therapy depends on whether it is being started in a hospital emergency, planned as part of an inpatient stay, or set up for long-term use at home. In an emergency, there is little preparation — the team acts quickly to restore safe oxygen levels. For planned or home therapy, there are several steps.

Before oxygen therapy begins, the medical team usually carries out some or all of the following assessments to find the right flow rate and delivery method for that patient:

• Pulse oximetry — a small clip placed on a finger to measure the percentage of oxygen carried by the red blood cells; this is painless and takes seconds
• Arterial blood gas (ABG) test — a blood sample taken from an artery (usually at the wrist) to measure oxygen, carbon dioxide, and the acid-base balance of the blood more precisely
• Chest X-ray or CT scan to look at the lungs and identify the cause of low oxygen
• Spirometry (a breathing test in which the patient blows into a mouthpiece) to measure how well the lungs move air
• A full medical history review, including current medications, especially blood thinners or sedatives that affect breathing

For home oxygen, there is usually no fasting required. Patients are asked about smoking habits because smoking near oxygen equipment is a serious fire risk, and the care team will provide safety guidance. No specific fasting or medication pause is needed for oxygen therapy itself, though other treatments for the underlying condition may have their own requirements.

Once the assessment is complete, oxygen therapy is started in a series of steps:

• The doctor prescribes a specific flow rate (measured in litres per minute) and a target blood-oxygen range for that patient.
• The care team selects the delivery device — nasal cannula, simple face mask, high-flow mask, or, in severe cases, a non-invasive ventilation mask or ventilator.
• The equipment is connected to a piped oxygen supply (in hospital) or a portable oxygen concentrator or cylinder (at home or during travel).
• The mask or cannula is fitted to the patient and adjusted for comfort.
• Oxygen levels are checked again with a pulse oximeter shortly after starting, and the flow rate is adjusted if needed.
• For long-term home therapy, a nurse or respiratory therapist explains how to use, clean, and store the equipment safely before the patient is discharged.

After oxygen therapy is started, the level of monitoring and the restrictions placed on the patient depend on whether the therapy is short-term in hospital or long-term at home. In hospital, nurses check blood-oxygen levels regularly and adjust the flow rate as the patient's condition changes. Once oxygen levels are stable and the underlying cause is being treated, the flow rate is gradually reduced — a process called weaning — and therapy is stopped when it is no longer needed. For patients going home on long-term oxygen, regular follow-up with a respiratory medicine specialist is important to make sure the prescription still matches the patient's needs.

• Monitoring: Blood-oxygen levels are checked frequently in hospital using a pulse oximeter; at home, patients may be given their own device and shown how to record readings for their doctor.
• Activity: Many patients on home oxygen can move around with a portable oxygen device; the care team will advise on safe activity levels based on the patient's condition.
• Skin care: The area around the nose, ears, and cheeks where the cannula or mask sits should be checked daily for soreness or pressure marks; soft padding or a different mask size may help.
• Humidification: If dryness or nosebleeds occur, a humidifier bottle attached to the oxygen supply is usually recommended.
• Equipment maintenance: Oxygen tubing, cannulas, and mask cushions should be cleaned or replaced regularly according to the manufacturer's schedule; concentrator filters need routine cleaning.
• Fire and home safety: No smoking anywhere near the oxygen supply; keep the equipment away from open flames, gas cookers, and heat sources; store cylinders upright and away from direct sunlight.
• Smoking cessation: Patients who smoke are strongly encouraged by their care team to stop, as smoking worsens the lung conditions that make oxygen therapy necessary and creates a direct fire hazard.
• Follow-up: The doctor will usually schedule repeat blood-gas or pulse-oximetry checks after discharge to decide whether the oxygen prescription needs to be changed or can be stopped.
• Air travel: Most airlines allow passengers to use approved portable oxygen concentrators on board, but arrangements must be made well in advance; the care team can advise on this.