Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed when the heart stops beating. Its goal is to keep blood flowing to the brain and vital organs until professional help arrives. CPR combines chest compressions, which manually pump blood, with rescue ventilations, which supply oxygen to the lungs. Effective CPR requires maintaining the correct ratio between compressions and ventilations, which is determined by the victim’s age and the number of rescuers present.
Standard Ratios for Adult Victims
For any victim who has reached puberty or is older, the standard compression-to-ventilation ratio is 30:2. This means a rescuer delivers 30 chest compressions followed by two rescue ventilations, then immediately repeats the cycle. This protocol applies whether a single person is performing CPR or if two rescuers are working together as a team.
The rationale behind this emphasis on compressions is rooted in the typical cause of cardiac arrest in adults. Most adult sudden cardiac arrests result from a primary heart problem, meaning the blood is already oxygenated when the heart stops. Therefore, the immediate need is to circulate that oxygenated blood through the body, which requires a high priority on compressions with minimal interruption.
Scientific research shows that continuous, high-quality chest compressions are what maintain adequate coronary perfusion pressure, which is the pressure that drives blood to the heart muscle itself. Interruptions, even brief ones for ventilations, significantly reduce this pressure, diminishing the overall effectiveness of the procedure. The 30:2 ratio balances the need for oxygenation with the necessity of maximizing blood flow to the brain and heart.
Modified Ratios for Children and Infants
The protocols for children and infants differ from those for adults because pediatric cardiac arrest is most often caused by respiratory failure or shock rather than a sudden cardiac event. Since the cause is typically a lack of oxygen first, ventilations play a relatively more significant role in the resuscitation effort for younger victims.
For infants, defined as less than one year old, and children, defined as one year old up to the onset of puberty, the ratio changes based on the number of rescuers. When a single rescuer is present, the standard adult ratio of 30 compressions to 2 ventilations is maintained. This single-rescuer protocol is primarily used to simplify the instruction and recall for lay rescuers in a high-stress emergency situation.
The ratio changes to 15 compressions to 2 ventilations when two or more rescuers are present. This 15:2 ratio effectively provides twice as many ventilations per minute compared to the 30:2 ratio, which is necessary to address the underlying respiratory cause of the arrest. Team-based CPR allows for a more efficient and coordinated approach, with one rescuer focusing on compressions and the other on delivering the more frequent ventilations.
This modified ratio ensures the smaller, developing body receives the higher proportion of oxygen needed to combat the respiratory distress that led to the collapse. The age cutoff of puberty is used because once a victim is physically mature, their body and the likely cause of cardiac arrest align more closely with adult physiology.
Essential Mechanics of High-Quality Compressions
Knowing the correct ratio is only one part of effective CPR; the quality of the compressions is equally important for a successful outcome. High-quality chest compressions must be delivered at a specific rate and depth to create sufficient blood flow. The recommended compression rate for all age groups is a consistent 100 to 120 compressions per minute.
The required compression depth varies significantly by age and physical size.
Compression Depths
- For an adult, the chest should be compressed to a depth of at least 2 inches, but no more than 2.4 inches.
- For a child, the depth should be approximately 2 inches, or about one-third the depth of the chest.
- For an infant, compressions should be delivered to a depth of about 1.5 inches, also equating to one-third the depth of the chest.
Rescuers should use two fingers for infant compressions or the heel of one hand for a small child. Proper hand placement for all victims involves the center of the chest, specifically on the lower half of the breastbone.
Another mechanical detail is allowing for complete chest recoil after each compression. A full recoil permits the chest wall to return to its normal position, which creates a vacuum effect that allows the heart to refill with blood. Leaning on the chest between compressions prevents this vital refilling process and lowers the effectiveness of the next compression.
Recognizing the Need for CPR and When to Stop
The need for CPR is recognized when a person is unresponsive and not breathing, or is only gasping for breath. The first step for a lay rescuer should be to ensure the scene is safe, then to call emergency medical services immediately before beginning compressions. CPR should be initiated right away if the victim is not moving, is not responding, and there are no signs of normal breathing.
Once CPR is started, the effort should continue without interruption until certain conditions are met. The most common signal to stop is the arrival of trained emergency medical personnel who are ready to take over the resuscitation effort. Rescuers should continue compressions until specifically told to pause or stop by the advanced providers. CPR should also be discontinued if the person shows definitive signs of life, such as moving, waking up, or beginning to breathe normally, which indicates a return of spontaneous circulation. In rare circumstances, if the scene becomes unsafe, or if the rescuer becomes too physically exhausted to continue delivering high-quality compressions, it is acceptable to stop. The guiding principle for a bystander is to keep delivering high-quality chest compressions until professional help arrives.