Unconsciousness is a state where a person is unresponsive to stimuli and unable to voluntarily interact with their surroundings. This differs from normal sleep, where the brain remains active and the person responds to strong external signals. The immediate answer to whether an unconscious person breathes is yes; breathing usually continues, but this condition is always a serious medical event. The primary danger is that the breathing mechanism, while functioning, can easily become compromised.
The Mechanism That Keeps You Breathing
The fundamental process of respiration is controlled automatically by the autonomic nervous system, which manages body functions without conscious thought. This involuntary control is centered in the brainstem, specifically the medulla oblongata, located at the base of the brain. The medulla contains respiratory centers that constantly monitor the body’s needs.
These centers receive information from chemoreceptors, which detect levels of oxygen and, more importantly, carbon dioxide in the blood. When carbon dioxide levels rise, the medulla signals the diaphragm and intercostal muscles to contract, increasing the rate and depth of breathing to expel the excess gas. Because this regulation is an automatic function managed by the brainstem, it operates even when higher brain functions are offline. This ensures that a person generally continues to breathe after losing consciousness.
When Breathing Fails: Loss of Airway Control
Although the brainstem continues to send signals to the breathing muscles, unconsciousness causes a complete relaxation of all skeletal muscles, including those in the pharynx and jaw. This loss of muscle tone is the primary reason breathing becomes compromised when an unconscious person lies on their back. The tongue, a large muscle attached to the lower jaw, loses the support of these relaxed muscles.
The tongue then falls backward against the posterior wall of the throat, creating a mechanical obstruction that can significantly block the airway. Other soft tissues in the throat can worsen this blockage, making it difficult or impossible for air to pass. Protective reflexes, such as the ability to cough or gag to clear the throat, are suppressed or absent in this state. This suppression creates a risk of aspiration, where vomit, blood, or other fluids can enter the lungs.
Identifying Adequate Versus Compromised Breathing
A person who is unconscious but breathing normally will show a rhythmic and quiet rise and fall of the chest or abdomen, with an expected rate of 12 to 20 breaths per minute. A layperson can use observation methods, though the traditional “Look, Listen, and Feel” technique is now often condensed into a simple check for normal breathing. One should look closely for movement in the chest or abdomen that indicates air entry.
Breathing that is compromised will often be noisy, shallow, or slow. Sounds such as gurgling, rattling, or snoring can indicate a partial obstruction from the tongue or secretions. Gasping, which is irregular and ineffective, is not considered normal breathing and indicates a severe lack of oxygen. If breathing is absent or only gasping is present, it signals a life-threatening emergency requiring immediate intervention.
Immediate Steps for Assisting an Unconscious Person
The first step upon finding an unresponsive person is to call emergency services, such as 911 or the local equivalent. While waiting for help, the rescuer must focus on maintaining an open airway, which takes precedence. The simple head-tilt/chin-lift maneuver can often open the airway by lifting the tongue away from the back of the throat.
If the person is breathing adequately, they should be carefully rolled onto their side into the recovery position. This position helps maintain an open airway and allows any fluids or vomit to drain out of the mouth, preventing aspiration. If a spinal injury is suspected, the person should generally be left in the position they were found, unless the airway is actively obstructed. If the person is not breathing normally, CPR must be initiated immediately.