Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed when the heart stops beating. Historically, the standard technique followed the sequence of Airway, Breathing, and then Compressions, often referred to as A-B-C. This approach positioned opening the airway and delivering mouth-to-mouth rescue breaths as the immediate first steps for any rescuer. Over the last two decades, professional resuscitation science has undergone a significant evolution, driven by data on survival rates and bystander behavior. This shift in understanding and technique has led to new recommendations, prompting many to question the role of mouth-to-mouth in modern CPR protocols.
The Scientific Rationale for Prioritizing Compressions
In sudden cardiac arrest, which is often caused by an electrical malfunction in the heart, the victim’s lungs and blood typically contain a sufficient supply of oxygen for the first few minutes after collapse. This is because the person was usually breathing normally moments before the event, leaving a reservoir of residual oxygen in the bloodstream. The body’s immediate requirement is to move this existing, oxygen-rich blood to the brain and the heart muscle itself.
The most significant factor determining survival is the speed and quality of chest compressions. High-quality compressions manually perform the work of the stopped heart, creating artificial circulation to keep the brain cells alive until professional help arrives. For every interruption of compressions, the pressure required to perfuse the brain drops significantly and must be rebuilt from zero.
The current physiological understanding emphasizes maintaining continuous blood flow over immediately introducing new air. Therefore, professional guidelines have shifted the sequence from A-B-C to C-A-B, prioritizing Compressions first. Studies have shown that for unwitnessed adult cardiac arrests, the survival rates for compression-only CPR are comparable to, and sometimes better than, CPR that includes breaths.
Practical Barriers and Public Reluctance
Beyond the scientific rationale, the reluctance of bystanders to initiate CPR has been a major factor in the evolution of guidelines. Many people express significant apprehension about performing mouth-to-mouth resuscitation on a stranger, which creates a delay in treatment that is detrimental to the patient’s outcome. This delay can be caused by the rescuer worrying about opening the airway or retrieving a barrier device.
A primary concern for lay rescuers involves the aesthetic and hygienic aspects of the procedure, often referred to as the “ick” factor. Furthermore, the fear of transmitting infectious diseases, such as Human Immunodeficiency Virus or various forms of hepatitis, often serves as a psychological barrier to intervention. Though the actual risk of disease transmission is extremely low, the perception of risk is enough to prevent a bystander from acting.
The overarching goal of the simplified guideline is to eliminate any barrier that prevents a bystander from taking action. Training the public that fast, hard chest compressions are the immediate and only requirement maximizes the likelihood that someone will intervene quickly. In one survey, only 15% of respondents would provide compressions with ventilation on a stranger, compared to 68% who would perform compressions alone.
Current Guidelines and Critical Exceptions
For the untrained or lay rescuer who witnesses a sudden collapse in an adult, the current recommendation from many organizations is overwhelmingly compression-only CPR, sometimes called Hands-Only CPR. The simple instruction is to call emergency services immediately and begin pushing hard and fast in the center of the chest. Rescuers should aim for a rate of 100 to 120 compressions per minute, minimizing all pauses.
Despite the shift for the typical adult cardiac arrest, rescue breaths remain a necessary part of resuscitation in specific scenarios where the cause of the arrest is a lack of oxygen, rather than a primary heart problem. If the victim was not breathing adequately before the arrest, their blood is already depleted of oxygen upon collapse. In these situations, circulation alone will only move deoxygenated blood, making the immediate delivery of oxygen through rescue breaths necessary.
Situations caused by respiratory compromise include drowning, suffocation, trauma, and drug overdose. For victims of drowning, for example, the resuscitation priority must focus on restoring breathing as much as it does circulation. Studies show that people with cardiac arrest from non-cardiac causes survive at higher rates when CPR includes rescue breaths compared to compression-only CPR.
Critically, all infants and children are treated as primary respiratory arrests, meaning mouth-to-mouth or mouth-to-nose and mouth is still highly recommended. Children’s hearts usually stop due to prolonged lack of oxygen, not an electrical problem like in adults. Therefore, pediatric CPR protocols still mandate the combination of compressions and rescue breaths. Furthermore, highly trained professional rescuers are expected to perform full CPR, including rescue breaths, whenever feasible and with the use of specialized equipment.