Difference Between Low Flow and High Flow Oxygen

Oxygen therapy is a medical procedure in which oxygen is administered to a patient who is suffering from a low flow of oxygen, such as hypoxia. When anaesthesia is induced, oxygen therapy is also administered to maintain the flow of oxygen in the body.

The human body requires oxygen for cellular metabolism. If the concentration of oxygen in the body rises, it can cause oxygen toxicity, which can result in respiratory failure and lung damage. The use of oxygen for medical purposes began in 1917. It has since become the most widely used treatment in the world. The two types are low flow oxygen therapy and high flow oxygen therapy.

Supplemental oxygen is a lifeline for many critically ill patients, and it can be delivered through a variety of devices in nonintubated patients. There are two types of oxygen delivery systems: low-flow oxygen systems and high-flow oxygen systems. Understanding each system type is critical for proper clinical application. However, low- flow systems should not be confused with low oxygen concentrations. High flow does not necessarily imply high. The flow refers to the amount of oxygen given to the patient per minute. Let's take a closer look at the two delivery methods.

What is Low-Flow Oxygen?

Low-flow delivery systems are specific devices that deliver oxygen at lower flow rates than the patient's ventilatory requirements. When consistency in fraction of inspired oxygen (FiO2) delivery is not critical, these devices are used. It is based on the anatomic reservoir and minute ventilation of the patient. Low-flow delivery systems deliver oxygen at rates ranging from 0 to 15 litres per minute.

Nasal cannulas, simple masks, reservoir masks, partial rebreather, and nonrebreather/Tavish mask are all examples of low-flow oxygen delivery systems. Nasal cannulas are one of the most common and widely used oxygen delivery systems, both in hospitals and in outpatient settings. The primary benefits of low-flow delivery systems are ease of use and patient comfort. Cannulas and masks must fit properly on the patient's face and nose to ensure proper oxygen delivery.

A nasal cannula is a thin tube with two nozzles that is inserted into the person's nostrils. The nasal cannula delivers oxygen in concentrations ranging from 24 to 40%. It delivers oxygen at a rate of 1 to 6 litres per minute (LPM).

The oxygen concentration in the face mask ranges from 35 to 55%. The oxygen flow rate is 5 to 10 LPM. When there is a lack of oxygen, a partial rebreather can be used instead of face masks. A reservoir bag is the only component of a partial rebreather.

What is High-Flow oxygen?

High-flow oxygen delivery is a non-invasive respiratory support method for critically ill patients that delivers extremely accurate oxygen concentrations at flow rates that exceed the patient's respiratory requirements. It is commonly defined as the management of gas flows greater than 6-15 litres per minute. High-flow systems are the second type of oxygen delivery device, capable of delivering at least 40 litres of conditioned gas per minute and providing an accurate FiO2 regardless of the patient's breathing pattern.

High-flow oxygen therapy can be used to provide respiratory support and to avoid intubation in patients with acute hypoxemic respiratory failure. Venturi masks are likely the only devices capable of delivering controlled high-flow oxygen concentration in non-intubated patients. High-flow oxygen delivery systems include ventilators, oxygen tents, tracheostomy collars, and aerosol masks.

The patient is given oxygen after the oxygen flow rate is set. They must breathe in and out through their noses. It is a non-invasive treatment. It means that it does not cause skin damage. High-flow oxygen therapy carries very few risks. If there is a lot of mucous, the nasal prongs may become blocked. Acute heart failure, Asthma, Bronchiectasis, Pneumonia, Lung cancer, Pulmonary oedema, acute respiratory distress syndrome (ARDS), Chest trauma, and other severe respiratory problems necessitate high-flow oxygen therapy.

Similarities between Low-Flow and High-Flow Oxygen

  • Both low-flow oxygen and high-flow oxygen are related to conditions where oxygen is required.

  • In both low-flow and high-flow oxygen procedures, some preparations have to be made before starting the procedures.

  • Both have some risks that must be addressed.

Difference between Low-Flow and High-Flow Oxygen

The following table highlights the major differences between low-flow and high-flow oxygen −


Low-Flow Oxygen

High-Flow Oxygen

How do they act?

Low-flow systems provide relatively stable FiO2 levels in patients whose respiratory rate and pattern are stable

High-flow systems deliver very accurate oxygen concentration at flow rates that exceed patient’s respiratory requirements


Low-flow delivery systems provide oxygen flows from 0 to 15 litres per minute

High-flow delivery systems should provide flows of at least 50-60 litres per minute

Types of devices

Low-flow systems include nasal cannula, simple masks, reservoir masks, partial rebreather, and nonrebreather.

High-flow systems include ventilators, oxygen tents, tracheostomy collars, nebulizer, and aerosol masks.


Low-flow oxygen are provided to the ones who are stable

High-flow oxygen are provided to the ones who have respiratory requirements.

Risks involved

In low-flow oxygen, frostbite, fire connected to devices, Nasal irritation, skin rash, etc. are some of the risks involved.

In high-flow oxygen, Nasal prongs may get blocked.


In low-flow oxygen, first clinical history of patient and illness is verified for further procedures

In high-flow oxygen, Blood tests and Chest X-rays are checked.


In an emergency, both low flow and high flow oxygen are used to provide oxygen to patients. Both can provide the required level of FiO2. High and low flow do not imply a higher or lower concentration of oxygen. Rather, it is determined by the rate of flow provided to the patients per minute.

Low-Flow oxygen is provided to those who are stable and require very little oxygen in such conditions. Those suffering from severe respiratory problems are given oxygen, and the pattern of respiratory rate changes. When traditional methods fail, high-flow oxygen therapy works. It always exceeds the patient's respiration limit.

Updated on: 24-Jan-2023


Kickstart Your Career

Get certified by completing the course

Get Started