Blow-by oxygen deliver illustration

What is Blow-By Oxygen? (2024)

by | Updated: Jan 9, 2024

Blow-by oxygen is a method of oxygen delivery that primarily serves patients who cannot tolerate more traditional delivery systems such as nasal cannulas or face masks.

This approach involves directing the flow of oxygen towards the patient’s nose and mouth from a close distance, without a direct interface.

This article will provide an overview of blow-by oxygen, its benefits and potential drawbacks, as well as how it compares to other forms of oxygen delivery.

What is Blow-by Oxygen?

At its most basic level, blow-by oxygen involves administering oxygen to patients by allowing it to ‘blow by’ their nose and mouth from a close range, rather than delivering it through a direct interface like a nasal cannula or a face mask. This process is achieved by attaching an oxygen source to tubing, which is then directed towards the patient’s face.

The oxygen concentration inhaled by the patient is influenced by various factors, such as the flow rate of the oxygen, the distance of the tubing from the patient’s face, the patient’s respiratory rate, and the ambient air.

In theory, the simplicity of blow-by oxygen delivery seems ideal. However, it’s worth noting that it is generally less efficient in ensuring a precise concentration of oxygen delivery than other methods due to the many variables in play.

Thus, it’s most commonly used in specific situations where other delivery methods are unsuitable or impractical.

Blow-by oxygen delivery vector illustration

When is Blow-by Oxygen Used?

Blow-by oxygen is often used in pediatric care, particularly in scenarios where a child is too distressed or agitated to tolerate a face mask or nasal cannula.

It’s a particularly crucial tool in emergency situations where immediate oxygen delivery is paramount, and there’s no time to coax a frightened or uncooperative child into accepting a more standard oxygen delivery device.

In addition, blow-by oxygen can be used for adults who refuse or cannot tolerate standard oxygen delivery methods.

In some cases, patients suffering from claustrophobia may prefer blow-by oxygen as it does not involve the use of confining masks or cannulas.

It’s also worth mentioning that blow-by oxygen is sometimes used during endotracheal intubation or during anesthesia, where it can help maintain oxygenation between the removal of an old tube and the insertion of a new one.

How to Set Up Blow-By Oxygen

Setting up a blow-by oxygen system is relatively straightforward. Here are step-by-step instructions:

  1. Secure the Oxygen Source: First, ensure you have a reliable source of oxygen. This could be an oxygen concentrator, a compressed oxygen cylinder, or a hospital oxygen outlet. Make sure the oxygen source is properly set up according to its specific instructions.
  2. Attach the Oxygen Tubing: The next step is to attach one end of the oxygen tubing to the oxygen source. Make sure it’s securely connected to prevent any leakage.
  3. Adjust the Flow Rate: You should adjust the flow rate as directed by the healthcare provider. This typically depends on the patient’s specific needs and can range from 1 to 15 liters per minute (L/min) or more. The flow meter on the oxygen source will help you set this rate.
  4. Direct the Tubing: The other end of the tubing should be directed towards the patient’s face. Ensure the tubing is close enough (typically 1 to 2 inches) to the patient’s nose and mouth to allow them to inhale the oxygen effectively, but not so close as to cause discomfort.
  5. Monitor the Patient: Once you have set up the system, it’s essential to monitor the patient closely to ensure they are receiving enough oxygen. Watch for signs of improved breathing and oxygen saturation, using a pulse oximeter if available.
  6. Adjust as Necessary: As conditions change, you may need to adjust the flow rate or reposition the tubing. Always be prepared to make these adjustments as needed, and to switch to a different oxygen delivery method if the patient’s condition warrants it.

Remember: Blow-by oxygen is a less precise method of oxygen delivery and should only be used in certain situations, typically when a more direct delivery method is not tolerated by the patient. Always follow the instructions of the patient’s healthcare provider, and seek medical help if you’re unsure about any aspect of the process.

Cautions and Considerations

While blow-by oxygen can be a lifesaver in certain situations, healthcare professionals must consider its limitations.

For one, it’s challenging to determine the precise amount of oxygen the patient is receiving, as this method is influenced by many uncontrollable factors.

Therefore, while it can be used in emergency situations or as a temporary measure, it is generally not appropriate for situations where a patient requires a specific and consistent concentration of oxygen.

FAQs About Blow-By Oxygen

What Does Blow-By Mean in Medical Terms?

In medical terms, “blow-by” refers to a method of delivering supplemental oxygen to a patient.

Instead of inserting a device such as a mask or nasal cannula directly onto the patient’s face, the oxygen is allowed to “blow by” the patient’s face from a close range, allowing them to inhale it indirectly.

How Effective is Blow-By Oxygen?

The effectiveness of blow-by oxygen can vary significantly based on several factors. It can be quite effective for delivering emergency oxygen or for patients who cannot tolerate other delivery methods.

However, it’s less efficient than other methods for ensuring a precise and consistent concentration of oxygen delivery because many variables can influence the actual amount of oxygen the patient inhales.

What Percentage is Blow-By Oxygen?

The oxygen concentration or percentage delivered via the blow-by method can vary widely, depending on factors such as the oxygen flow rate, the distance of the tubing from the patient’s face, the patient’s breathing rate, and the ambient air.

It’s typically less than what can be achieved with a tightly fitted face mask or nasal cannula. The percentage can range from around 21% (the same as room air) to up to 60%, but it’s difficult to measure precisely.

What is the Flow Rate for Blow-By Oxygen?

The flow rate for blow-by oxygen is usually set between 1 to 15 liters per minute (L/min) or more, depending on the patient’s condition and the healthcare provider’s instructions.

The flow rate determines the amount of oxygen delivered, but the actual amount the patient receives can be influenced by many other factors, as discussed above.

Higher flow rates deliver higher concentrations of oxygen, but the relationship is not linear or precise.

Final Thoughts

In the right circumstances, blow-by oxygen can be a valuable tool for delivering oxygen to patients who cannot tolerate more conventional methods.

It is particularly useful in emergency and pediatric care but must be used with caution due to its inability to deliver a precise concentration of oxygen and the potential risks associated with high oxygen levels.

As with all medical procedures and interventions, healthcare providers must weigh the benefits and risks, using their clinical judgement to ensure the best possible patient outcomes.

John Landry, BS, RRT

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


  • Barends CRM, Yavuz P, Molenbuur B, Absalom AR. Performance of blow-by methods in delivering oxygen to pediatric patients during transport: A laboratory study. Paediatr Anaesth. 2018 Dec.

Recommended Reading