Oxygen Therapy Methods - Types, Flow Rates, Indications and Safety

Oxygen therapy is a medical treatment used to give extra oxygen to a patient who is not getting enough oxygen through normal breathing. It is commonly used in hospitals, emergency rooms, ambulances, intensive care units, operation theatres, and home care settings.

The main aim of oxygen therapy is to improve the amount of oxygen in the blood and help vital organs such as the brain, heart, lungs, and kidneys function properly. Oxygen may be delivered through different devices, including a nasal cannula, simple face mask, Venturi mask, non-rebreather mask, and bag-valve mask.

Each oxygen delivery method has a specific purpose and flow rate. A nasal cannula usually delivers 1–6 L/min and is considered a low-flow device. A simple face mask delivers 5–10 L/min. A Venturi mask delivers 4–12 L/min and provides a precise oxygen concentration. A non-rebreather mask delivers 10–15 L/min and is used when high oxygen is needed. A bag-valve mask is used for emergency ventilation when the patient is not breathing adequately.

Oxygen Therapy Methods - Types, Flow Rates, Indications and Safety

What is oxygen therapy?

Oxygen therapy is the administration of supplemental oxygen to increase oxygen availability in the body. It is used when a patient has low oxygen levels, difficulty breathing, shock, cardiac arrest, or other conditions where oxygen delivery to tissues is reduced.

Normally, air contains about 21% oxygen. In many illnesses, the body may need more oxygen than room air can provide. Oxygen therapy helps increase the oxygen concentration the patient breathes in.

Why oxygen therapy is important

Oxygen is essential for life. Every cell in the body needs oxygen to produce energy. When oxygen levels fall, cells cannot work properly. The brain and heart are especially sensitive to low oxygen.

Low oxygen can cause confusion, restlessness, bluish lips, chest pain, rapid breathing, and eventually unconsciousness. Severe oxygen deficiency can damage organs and become life-threatening.

Oxygen therapy helps by:

Increasing oxygen in the blood
Reducing breathing effort
Supporting the heart and brain
Improving tissue oxygen delivery
Helping during emergencies
Supporting patients with lung or heart disease

Key oxygen therapy methods

The image highlights five important oxygen therapy methods:

Nasal cannula
Simple face mask
Venturi mask
Non-rebreather mask
Bag-valve mask

Each method has different oxygen delivery capacity, flow rate, and clinical use.

Oxygen therapy flow rate chart

Oxygen Device	Flow Rate	Oxygen Delivery Type	Common Use
Nasal cannula	1–6 L/min	Low flow	Mild hypoxia, stable patients
Simple face mask	5–10 L/min	Moderate oxygen	Moderate oxygen need
Venturi mask	4–12 L/min	Precise FiO₂	Controlled oxygen therapy
Non-rebreather mask	10–15 L/min	High oxygen	Severe hypoxia, emergency oxygen
Bag-valve mask	As needed with oxygen source	Emergency ventilation	Poor or absent breathing

Nasal cannula

A nasal cannula is a simple oxygen delivery device with two small prongs placed inside the nostrils. It is comfortable, easy to use, and commonly used for patients who need low-flow oxygen.

Nasal cannula flow rate

The usual flow rate is:

1–6 L/min

It is considered a low-flow oxygen device.

When nasal cannula is used

Nasal cannula may be used for:

Mild hypoxia
Stable patients needing low oxygen
Long-term oxygen therapy
Post-operative oxygen support
Patients who need oxygen but can breathe on their own
Patients who need to talk, eat, or drink while receiving oxygen

Advantages of nasal cannula

Nasal cannula is widely used because it is simple and comfortable.

Main advantages include:

Easy to apply
Allows talking
Allows eating and drinking
Comfortable for long periods
Less claustrophobic than a mask
Useful for mild oxygen requirement

Limitations of nasal cannula

Nasal cannula is not suitable for severe hypoxia because it provides limited oxygen concentration.

Limitations include:

Low oxygen delivery
Oxygen concentration may vary with breathing pattern
May dry the nose
Not ideal in severe respiratory distress
Not suitable when high oxygen is urgently needed

Important point

Do not use low-flow oxygen alone in severe hypoxia. If the patient has very low oxygen saturation or severe breathing difficulty, a higher oxygen delivery device may be needed.

Simple face mask

A simple face mask covers the nose and mouth and delivers oxygen at a higher flow rate than nasal cannula. It is useful when a patient needs more oxygen than a nasal cannula can provide.

Simple face mask flow rate

The usual flow rate is:

5–10 L/min

A minimum flow is needed to prevent the patient from rebreathing exhaled carbon dioxide inside the mask.

When simple face mask is used

A simple face mask may be used for:

Moderate hypoxia
Short-term oxygen therapy
Patients who need more oxygen than nasal cannula
Emergency department care
Post-operative support
Respiratory distress with moderate oxygen need

Advantages of simple face mask

Main advantages include:

Delivers more oxygen than nasal cannula
Easy to apply
Useful for short-term oxygen support
Covers both nose and mouth

Limitations of simple face mask

Limitations include:

May feel uncomfortable
Interferes with eating and talking
Oxygen concentration is not highly precise
Requires proper fitting
Can cause carbon dioxide rebreathing if flow is too low

Venturi mask

A Venturi mask is an oxygen delivery device that provides a precise concentration of oxygen. It uses color-coded adapters or valves to control the amount of oxygen delivered.

Venturi mask flow rate

The usual flow range shown is:

4–12 L/min

The exact flow depends on the Venturi adapter and desired oxygen concentration.

What is FiO₂?

FiO₂ means fraction of inspired oxygen. It refers to the percentage of oxygen the patient breathes in.

Room air has an FiO₂ of about 21%. Oxygen devices increase FiO₂ above room air level.

Why Venturi mask gives precise FiO₂

The Venturi mask mixes oxygen with room air in a controlled way. This allows a more accurate oxygen concentration than a simple mask or nasal cannula.

When Venturi mask is used

Venturi mask is commonly used when precise oxygen control is important.

It may be used for:

Patients with COPD
Controlled oxygen therapy
Moderate hypoxia
Patients at risk of carbon dioxide retention
Situations where exact FiO₂ is needed

Advantages of Venturi mask

Main advantages include:

Provides precise oxygen concentration
Useful for controlled oxygen therapy
Better control than simple mask
Helpful in COPD patients when oxygen must be carefully titrated

Limitations of Venturi mask

Limitations include:

Less convenient than nasal cannula
Can interfere with talking and eating
Needs correct adapter and flow setting
May not provide enough oxygen in severe hypoxia

Non-rebreather mask

A non-rebreather mask is used to deliver high-concentration oxygen. It has a face mask, reservoir bag, and one-way valves that reduce rebreathing of exhaled air.

Non-rebreather mask flow rate

The usual flow rate is:

10–15 L/min

This device is used when high oxygen delivery is needed.

When non-rebreather mask is used

A non-rebreather mask may be used in:

Severe hypoxia
Trauma
Shock
Carbon monoxide exposure
Severe respiratory distress
Emergency oxygen support
Patients waiting for advanced airway support

Advantages of non-rebreather mask

Main advantages include:

Delivers high oxygen concentration
Useful in emergencies
Rapidly improves oxygen delivery
Easy to apply

Limitations of non-rebreather mask

Limitations include:

Requires tight fitting
Patient must breathe spontaneously
Reservoir bag must remain inflated
Not a ventilation device
May be uncomfortable
Cannot be used effectively if breathing is inadequate

Important safety point

The reservoir bag should not collapse completely during inspiration. If it collapses, increase oxygen flow or reassess the device and patient.

Bag-valve mask

A bag-valve mask, also called BVM or Ambu bag, is used for emergency ventilation. It helps push air or oxygen into the lungs when the patient is not breathing properly.

Bag-valve mask use

A bag-valve mask is used for:

Emergency ventilation

It is not just an oxygen delivery device. It helps support breathing.

When bag-valve mask is used

A bag-valve mask may be used in:

Cardiac arrest
Respiratory arrest
Severe respiratory failure
Very slow or ineffective breathing
Unconscious patient with poor breathing
Emergency resuscitation
Before intubation

How bag-valve mask works

The mask is placed over the patient’s nose and mouth. The bag is squeezed by the healthcare provider to deliver breaths. When connected to oxygen, it can deliver high oxygen concentration.

Advantages of bag-valve mask

Main advantages include:

Provides assisted ventilation
Useful in emergencies
Can deliver high oxygen when connected to oxygen source
Used in resuscitation
Can be lifesaving in respiratory arrest

Limitations of bag-valve mask

Limitations include:

Requires proper training
Needs good mask seal
Can cause gastric inflation if ventilation is too forceful
May be difficult for one person to perform perfectly
Does not protect airway from aspiration

Indications of oxygen therapy

The image lists four important indications:

Hypoxia
Respiratory distress
Cardiac arrest
Shock

Hypoxia

Hypoxia means the body or tissues are not getting enough oxygen. It is one of the most common reasons for oxygen therapy.

Signs of hypoxia

Signs may include:

Low SpO₂
Shortness of breath
Rapid breathing
Restlessness
Confusion
Bluish lips or fingers
Chest discomfort
Fatigue
Drowsiness

Oxygen therapy in hypoxia

The oxygen device depends on severity. Mild hypoxia may need nasal cannula. Severe hypoxia may need a non-rebreather mask or assisted ventilation.

Respiratory distress

Respiratory distress means the patient is struggling to breathe. Oxygen therapy supports the patient while the cause is treated.

Signs of respiratory distress

Common signs include:

Fast breathing
Use of accessory muscles
Nasal flaring
Chest retractions
Inability to speak full sentences
Sweating
Anxiety
Low oxygen saturation

Oxygen therapy in respiratory distress

Patients with respiratory distress may need higher oxygen delivery. If breathing becomes weak or ineffective, bag-valve-mask ventilation may be required.

Cardiac arrest

Cardiac arrest occurs when the heart stops pumping effectively. During cardiac arrest, oxygen delivery to the brain and organs stops.

Oxygen therapy in cardiac arrest

In cardiac arrest, oxygen is given as part of resuscitation. A bag-valve mask may be used to ventilate the patient. Advanced airway support may be needed depending on the situation.

Shock

Shock is a condition where the body’s organs do not get enough blood flow and oxygen. Oxygen therapy is commonly used in shock because tissue oxygen delivery is reduced.

Oxygen therapy in shock

Patients in shock may receive high-flow oxygen, often through a non-rebreather mask. If breathing is inadequate, bag-valve-mask ventilation may be needed.

Important points in oxygen therapy

The image lists four important points:

Do not use low flow in severe hypoxia
Monitor SpO₂ continuously
Humidify oxygen if needed
Check mask fitting properly

Do not use low flow in severe hypoxia

Low-flow devices like nasal cannula may not provide enough oxygen in severe hypoxia. A patient with severe oxygen deficiency may need a non-rebreather mask, assisted ventilation, or advanced respiratory support.

Why this matters

Severe hypoxia can rapidly damage the brain and heart. Waiting too long with inadequate oxygen can be dangerous.

Monitor SpO₂ continuously

SpO₂ is oxygen saturation measured by pulse oximeter. It shows how much oxygen is carried by hemoglobin in the blood.

Why SpO₂ monitoring is important

Monitoring helps assess whether oxygen therapy is working. If SpO₂ remains low despite oxygen, the patient may need higher support.

What to monitor

Monitor:

SpO₂
Respiratory rate
Pulse
Blood pressure
Mental status
Work of breathing
Skin color
Response to oxygen therapy

Humidify oxygen if needed

Oxygen can dry the nose, mouth, and airway, especially when used at higher flows or for long periods.

When humidification may be needed

Humidification may be considered when:

Oxygen is used for a long time
Flow rate is high
Patient has dry secretions
Patient complains of nasal dryness
Artificial airway is present

Humidification helps keep airways moist and comfortable.

Check mask fitting properly

A poorly fitted mask can reduce oxygen delivery. Oxygen may leak from the sides, and the patient may not receive the expected concentration.

Good mask fitting signs

A properly fitted mask should:

Cover nose and mouth
Fit comfortably
Have minimal air leakage
Not press too tightly on skin
Allow oxygen flow correctly
Keep reservoir bag inflated in non-rebreather mask

Difference between low-flow and high-flow oxygen

Oxygen devices can be broadly divided into low-flow and high-flow systems.

Low-flow oxygen devices

Low-flow devices provide oxygen at a flow lower than or close to the patient’s inspiratory demand. The final oxygen concentration may vary depending on breathing pattern.

Examples include:

Nasal cannula
Simple face mask
Non-rebreather mask

Although a non-rebreather mask delivers high oxygen concentration, it is still often classified as a low-flow system because it does not meet all inspiratory demand in a controlled way.

High-flow oxygen systems

High-flow systems can deliver oxygen at a flow that meets or exceeds the patient’s inspiratory demand. They provide more controlled oxygen delivery.

Examples include:

Venturi mask
High-flow nasal cannula systems

Oxygen therapy device comparison

Device	Flow Rate	Oxygen Level	Best For	Main Limitation
Nasal cannula	1–6 L/min	Low	Mild hypoxia	Not for severe hypoxia
Simple face mask	5–10 L/min	Moderate	Short-term moderate oxygen	Less precise FiO₂
Venturi mask	4–12 L/min	Controlled	Precise FiO₂ need	Requires correct setup
Non-rebreather mask	10–15 L/min	High	Severe hypoxia	Requires good seal
Bag-valve mask	Emergency use	High with oxygen	Poor/absent breathing	Needs trained provider

How to choose the right oxygen device

Choosing the right oxygen device depends on the patient’s oxygen level, breathing effort, diagnosis, and urgency.

Mild hypoxia

A nasal cannula may be enough if the patient is stable and only needs low oxygen support.

Moderate hypoxia

A simple face mask may be used when nasal cannula is not enough.

Need for precise oxygen

A Venturi mask is useful when exact oxygen concentration is important, such as in selected COPD patients.

Severe hypoxia

A non-rebreather mask is commonly used when high oxygen is required urgently.

Poor or absent breathing

A bag-valve mask is used when the patient cannot breathe adequately on their own.

Oxygen therapy and SpO₂ targets

Oxygen should be given according to the patient’s need and monitored carefully. In many acutely ill patients, oxygen is adjusted to maintain adequate saturation. However, some patients, especially those with chronic lung disease, may require controlled oxygen targets.

Why oxygen targets matter

Too little oxygen can cause organ damage. Too much oxygen may also be harmful in certain patients, especially those at risk of carbon dioxide retention. This is why oxygen therapy should be monitored and adjusted.

Signs oxygen therapy is working

Oxygen therapy may be helping if:

SpO₂ improves
Breathing becomes easier
Patient becomes less restless
Skin color improves
Heart rate decreases toward normal
Confusion improves
Work of breathing reduces

Signs oxygen therapy is not enough

Oxygen therapy may not be enough if:

SpO₂ remains low
Breathing becomes worse
Patient becomes drowsy
Chest retractions increase
Cyanosis persists
Patient cannot speak
Respiratory rate becomes very high or very low
Consciousness decreases

In such cases, urgent escalation is needed.

Common mistakes in oxygen therapy

Using nasal cannula in severe hypoxia

Nasal cannula may not provide enough oxygen in severe hypoxia. A higher oxygen delivery method should be used when needed.

Not checking oxygen flow

If flow is too low, the patient may not receive enough oxygen. For masks, too-low flow can also increase rebreathing risk.

Poor mask fitting

Mask leakage reduces oxygen delivery. Always check fit.

Not monitoring SpO₂

Oxygen therapy should be guided by patient response and oxygen saturation.

Forgetting humidification

Long-term or high-flow oxygen may cause dryness and discomfort if humidification is needed.

Ignoring patient comfort

A patient may remove an uncomfortable mask. Comfort and proper explanation improve cooperation.

Complications of oxygen therapy

Oxygen therapy is usually safe when used correctly, but complications can occur.

Dryness and irritation

Oxygen can dry the nose, throat, and mouth. Humidification may help when needed.

Skin pressure injury

Masks and tubing can cause pressure marks, especially with prolonged use.

Carbon dioxide retention

Some patients with chronic lung disease may retain carbon dioxide if oxygen is not controlled carefully.

Fire risk

Oxygen supports combustion. It does not burn by itself, but it makes fire spread faster. Keep oxygen away from flames, smoking, and sparks.

Delayed escalation

A major risk is continuing simple oxygen therapy when the patient actually needs ventilation or advanced airway support.

Oxygen safety precautions

Keep oxygen away from fire

Do not smoke near oxygen. Keep oxygen away from flames, candles, gas stoves, and sparks.

Check tubing

Make sure oxygen tubing is not kinked, blocked, or disconnected.

Confirm flow rate

Set the oxygen flow rate according to the prescribed device and patient need.

Monitor patient

Observe breathing, oxygen saturation, mental status, and comfort.

Use clean equipment

Use clean oxygen devices and replace them according to protocol.

Oxygen therapy in emergency care

In emergency care, oxygen therapy is often started quickly because oxygen deficiency can be life-threatening. Patients with trauma, shock, cardiac arrest, severe asthma, pneumonia, or respiratory failure may need immediate oxygen support.

Emergency oxygen priorities

The priorities are:

Open airway
Support breathing
Give oxygen
Monitor SpO₂
Treat the cause
Escalate if the patient worsens

Oxygen therapy in respiratory diseases

Oxygen therapy is commonly used in respiratory diseases such as pneumonia, asthma, COPD, pulmonary edema, and respiratory failure.

Pneumonia

Pneumonia can reduce oxygen exchange in the lungs. Oxygen therapy helps maintain blood oxygen while antibiotics and other treatments address the infection.

Asthma

Severe asthma can cause low oxygen due to airway narrowing. Oxygen may be needed along with bronchodilators and other medicines.

COPD

COPD patients may need controlled oxygen therapy. Venturi mask is often useful when precise oxygen concentration is required.

Pulmonary edema

In pulmonary edema, fluid in the lungs interferes with oxygen exchange. Oxygen support may be needed, sometimes with advanced breathing support.

Oxygen therapy in shock

In shock, oxygen delivery to organs is reduced because blood flow is poor. Even if the lungs are working, tissues may not receive enough oxygen.

Why oxygen is given in shock

Oxygen increases the amount available in the blood. It supports vital organs while fluids, medicines, or other treatments correct the cause of shock.

Oxygen therapy in cardiac arrest

During cardiac arrest, breathing and circulation are severely impaired. Oxygen is delivered through bag-valve mask or advanced airway during resuscitation.

Key goal

The goal is to provide oxygen to the lungs while chest compressions help circulate blood to the brain and heart.

Oxygen therapy for students

For students, oxygen therapy becomes easier when learned by device, flow rate, and purpose.

Easy memory guide

Nasal cannula: low oxygen, 1–6 L/min
Simple mask: moderate oxygen, 5–10 L/min
Venturi mask: precise oxygen, 4–12 L/min
Non-rebreather mask: high oxygen, 10–15 L/min
Bag-valve mask: emergency ventilation

Quick revision table

Method	Flow Rate	Key Feature
Nasal cannula	1–6 L/min	Low flow
Simple face mask	5–10 L/min	Covers nose and mouth
Venturi mask	4–12 L/min	Precise FiO₂
Non-rebreather mask	10–15 L/min	High oxygen
Bag-valve mask	Emergency ventilation	Supports breathing

Did you know?

Did you know 1

A nasal cannula allows patients to talk, eat, and drink while receiving oxygen, making it comfortable for mild oxygen support.

Did you know 2

A Venturi mask is useful when doctors need to give a specific oxygen concentration instead of an approximate amount.

Did you know 3

A bag-valve mask is not just an oxygen mask. It is a ventilation device used when a patient is not breathing properly.

FAQs on oxygen therapy methods

What is oxygen therapy?

Oxygen therapy is a treatment that gives extra oxygen to a patient who has low oxygen levels or difficulty breathing. It helps improve oxygen in the blood and supports vital organs. It may be given through nasal cannula, masks, or ventilation devices.

What are the main oxygen therapy methods?

The main oxygen therapy methods include nasal cannula, simple face mask, Venturi mask, non-rebreather mask, and bag-valve mask. Each device has a different oxygen flow rate and clinical use. The choice depends on the patient’s oxygen level and breathing condition.

What is the flow rate of nasal cannula?

A nasal cannula usually delivers oxygen at 1–6 L/min. It is used for mild hypoxia and stable patients who need low-flow oxygen. It is comfortable and allows the patient to talk and eat.

What is the flow rate of a simple face mask?

A simple face mask usually delivers oxygen at 5–10 L/min. It is used when the patient needs more oxygen than a nasal cannula can provide. The mask should fit properly over the nose and mouth.

What is a Venturi mask used for?

A Venturi mask is used to deliver a precise oxygen concentration, also called precise FiO₂. It is especially useful when controlled oxygen therapy is needed. It may be used in patients where oxygen levels must be carefully adjusted.

What is the flow rate of a non-rebreather mask?

A non-rebreather mask usually uses 10–15 L/min oxygen flow. It delivers high oxygen concentration and is commonly used in severe hypoxia, shock, trauma, and emergency situations. The reservoir bag should remain inflated during use.

When is a bag-valve mask used?

A bag-valve mask is used for emergency ventilation when a patient is not breathing properly or has stopped breathing. It is commonly used in cardiac arrest, respiratory arrest, and severe respiratory failure. It requires proper technique and a good mask seal.

Why should SpO₂ be monitored during oxygen therapy?

SpO₂ monitoring shows how much oxygen is being carried in the blood. It helps determine whether oxygen therapy is working or whether the patient needs more support. Continuous monitoring is important in severe illness.

Why should low-flow oxygen not be used in severe hypoxia?

Low-flow oxygen, such as nasal cannula, may not provide enough oxygen in severe hypoxia. Severe oxygen deficiency can quickly damage vital organs. Higher oxygen delivery devices or assisted ventilation may be needed.

Why is mask fitting important in oxygen therapy?

Proper mask fitting ensures that the patient receives the intended oxygen concentration. A loose mask allows oxygen to leak out and reduces effectiveness. Poor fitting can also cause discomfort and pressure marks.