Rescue breathing puts oxygen into a person’s lungs when they have stopped breathing on their own but still have a heartbeat, or as part of full CPR when both breathing and circulation have stopped. It is commonly called expired air resuscitation because the air you breathe out still contains enough oxygen to help another person.
Why It Works
The air you inhale is roughly 21 percent oxygen. The air you exhale still contains around 17 percent oxygen, since your body only uses a small fraction of what you breathe in. That remaining oxygen is more than enough to support another person’s blood oxygen levels while you breathe for them.
Mouth to Mouth Technique
- Open the airway with a head tilt and chin lift, and pinch the soft part of the nose closed.
- Take a normal breath, seal your mouth completely over the patient’s mouth, and blow steadily for about one second, watching for the chest to rise.
- Move your mouth away, let the chest fall, and take another breath before repeating.
- Check the chest rises with each breath. If it does not rise, recheck the head tilt and the seal of your mouth before trying again.
Mouth to Nose Technique
This method is used when the mouth cannot be sealed properly, such as with significant facial injury or jaw problems. Close the patient’s mouth with the hand supporting their chin, seal your mouth around their nose instead, and breathe in the same way, watching for chest rise. Open the mouth briefly between breaths to let air escape.
Mouth to Mask Technique
A resuscitation mask or shield creates a barrier between you and the patient, reducing direct contact for hygiene reasons. Position the narrow end of the mask on the bridge of the nose and the wider end covering the mouth and chin, apply firm pressure to achieve a seal, then breathe through the mouthpiece the same way as mouth to mouth. Many workplaces and vehicles now carry these as part of a basic first aid kit specifically for this reason.
Rescue Breathing Rate When a Pulse Is Present
If a person has a pulse but is not breathing adequately on their own, rescue breaths are given without chest compressions. Current guidance for adults is one breath approximately every six seconds, which works out to about ten breaths per minute. For infants and children the rate is faster, roughly one breath every two to three seconds. Recheck the pulse regularly, since if it disappears you need to start chest compressions immediately.
Adjusting for Infants and Children
Use a gentler head tilt, closer to neutral, since over extending a young child’s neck can close the airway rather than open it. For infants, seal your mouth over both the mouth and nose together rather than the mouth alone, and give smaller, gentler breaths, just enough to see the chest rise, since a baby’s lungs are easily over inflated.
Common Mistakes
Breathing too hard or too fast is the most frequent error, and it pushes air into the stomach instead of the lungs, which can cause vomiting and further complicate the airway. Not sealing the mouth or nose fully lets air escape uselessly. Skipping the head tilt means breaths often will not get past a blocked airway no matter how forcefully you blow.
Frequently Asked Questions
How long should each rescue breath last?
About one second, just long enough to see the chest visibly rise.
What do you do if the chest does not rise during a rescue breath?
Recheck the head tilt and chin lift, check your seal is complete, and look inside the mouth for any obstruction before trying again.
When is mouth to nose used instead of mouth to mouth?
When the mouth cannot be sealed properly, for example due to significant facial or jaw injury.
References and Last Reviewed
- American Heart Association, Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
- International Liaison Committee on Resuscitation (ILCOR), Consensus on Science and Treatment Recommendations
Jurisdiction: General first aid guidance, internationally applicable.
Last technically reviewed: September 2026
Reviewed by: EHS Guidelines Editorial Team
This article is educational and does not replace accredited first aid training or professional medical care. In a real emergency, call your local emergency number immediately.
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