Cardiopulmonary Resuscitation

Anatomy and Physiology

CPR involves 2 primary components—chest compressions and artificial ventilation. Chest compressions are performed to manually pump blood through the heart, whereas artificial respirations provide oxygen to the lungs.

Chest compressions are the cornerstone of CPR. These compressions generate artificial circulation by increasing intrathoracic pressure, which compresses the heart and propels blood forward. Effective compressions maintain coronary perfusion pressure, which is the difference between aortic diastolic and right atrial diastolic pressure during the relaxation phase of compressions. Coronary perfusion pressure is crucial for myocardial blood flow and is a primary determinant of successful return of spontaneous circulation.

Ventilations provide oxygen to the lungs and helps maintain blood oxygenation. However, positive-pressure ventilation can reduce coronary perfusion pressure by increasing intrathoracic pressure and impeding venous return to the heart. Therefore, the balance between adequate ventilation and minimizing interruptions to chest compressions is critical.

The definitive treatment for ventricular fibrillation and pulseless ventricular tachycardia is electrical defibrillation, most commonly administered using an automated external defibrillator. If defibrillation is not performed promptly, brain death can occur in less than 10 minutes. CPR is a critical intervention to provide artificial circulation and ventilation until defibrillation is possible. When performed correctly, conventional manual CPR can deliver up to 33% of normal cardiac output and oxygenation.[5]

Indications

CPR is indicated when a patient is unresponsive, not breathing, or exhibiting abnormal breathing patterns. Prompt recognition of these signs is critical, as early initiation of CPR greatly increases the chances of survival and favorable neurological outcomes.

The primary indication for CPR is cardiac arrest, characterized by the sudden cessation of cardiac mechanical activity, absence of detectable pulses, unresponsiveness, and apnea or agonal breathing. Respiratory arrest is another indication, where the patient has a pulse but is not breathing. In such cases, rescue breathing should be provided until spontaneous respiration resumes or advanced airway management is available.

Other situations that may necessitate CPR include drowning, drug overdose, or severe trauma, as these situations can result in either respiratory or cardiac arrest. Initiating CPR can be life-saving while awaiting advanced medical support. 

Contraindications

Contraindications for CPR arise in situations where resuscitative efforts are considered medically futile or ethically inappropriate. These decisions are primarily guided by clinical judgment and established protocols. CPR should not be performed in cases of irreversible death, such as when there are unmistakable signs like rigor mortis, decapitation, or dependent lividity. A valid do-not-resuscitate order or advance directive indicating the patient's wish to forgo resuscitation is also a clear contraindication.

In addition, CPR may be deemed nonbeneficial in patients with terminal illnesses or in situations where meaningful recovery is highly unlikely. In such cases, the Society of Critical Care Medicine recommends using clinical judgment alongside institutional policies to guide decisions.[6]

Equipment

Essential CPR equipment includes basic and advanced tools to support adequate resuscitation. Automated external defibrillators are vital for treating ventricular fibrillation or pulseless ventricular tachycardia and are widely available in public areas for laypersons and healthcare providers. Bag-valve masks are key for delivering ventilation, especially in clinical settings. In contrast, advanced airway tools, such as endotracheal tubes and supraglottic devices, are used by trained professionals to secure the airway and improve oxygenation.

Mechanical CPR devices, such as load-distributing bands and pneumatic pistons, can provide consistent chest compressions during prolonged resuscitation. Personal protective equipment, including gloves and masks, protects rescuers from potential infection. 

Preparation

Patients requiring CPR are unconscious, unresponsive, and without detectable pulses. Determining when the patient was last assessed as normal—or more accurately, when pulses were lost—can provide important prognostic information. Collateral history from bystanders, family members, friends, or the patient's primary care physician can also aid in identifying the underlying cause of the arrest. 

Although no specific physical examination findings are pathognomonic for cardiac arrest, signs such as cyanosis and decreased peripheral perfusion may offer clues to the underlying etiology. Other findings, such as agonal respirations or fixed and dilated pupils, may also be present and support the clinical impression of cardiac arrest.

The evaluation to determine whether CPR should be performed begins with ensuring that the scene is safe for both the rescuer and the victim. Once safety is confirmed, the responder should check the individual for responsiveness by gently tapping and shouting, Are you okay? If there is no response, emergency services should be activated immediately, and an automated external defibrillator should be retrieved if available. CPR should be initiated without delay after briefly assessing breathing and pulse.[6]

Technique or Treatment

The technique for performing CPR involves several critical steps and requires equipment and preparation. Modifications for children, infants, and in-hospital scenarios are detailed. These recommendations reflect the 2020 AHA Guidelines Update for CPR and Emergency Cardiac Care.

Immediate recognition of cardiac arrest is critical for activating emergency medical services (EMS) response and starting CPR as soon as possible. First, the safety of the scene should be ensured before the individual is approached. Responsiveness should be checked by tapping the person and calling out loudly. Help should be summoned immediately. In today's world of widespread mobile phone access, calling 911 while staying with the individual is often possible. 

An automated external defibrillator and emergency equipment should be obtained, or someone nearby should be instructed to retrieve them. The individual should be assessed for breathing and a pulse. If spontaneous breathing and palpable pulses are present, the individual should be monitored closely until emergency services arrive.

If a pulse is present but breathing is abnormal, such as gasping, rescue breathing should be initiated at a rate of 10 breaths/min, or 1 breath per 6 seconds. If an opioid overdose is suspected, naloxone should be administered according to established protocols. The pulse should be reassessed every 2 minutes. If the pulse is no longer detectable, CPR should be started immediately.

If the individual is not breathing and has no pulse, CPR should be initiated using the CAB sequence—chest compressions (C), airway (A), and breathing (B). Chest compressions should be started by placing the hands on the lower half of the sternum. Compressions should be delivered at 100 to 120 per minute, with a depth of at least 2 inches, while avoiding excessive force. Full recoil of the chest should be allowed between compressions to maintain coronary artery perfusion pressure.[7] 

Thirty chest compressions should be performed, followed by a brief pause for 2 rescue breaths.. Because chest compressions are essential for maintaining blood flow, interruptions should be minimized. Any necessary pauses should be brief to ensure continuous perfusion to vital organs.[8][9]

After completing 30 chest compressions, the rescuer should open the airway using the head tilt-chin lift maneuver, provided there is no suspicion of a cervical spine injury. If a cervical spine injury is suspected, the airway should be opened with a jaw-thrust maneuver without tilting the head. Two rescue breaths are then administered. The rescuer takes a normal (not deep) breath and delivers each breath over approximately 1 second, just enough to make the individual's chest rise. A second breath is given in the same manner before immediately resuming chest compressions. 

Ideally, healthcare providers acting as out-of-hospital rescuers should have access to a barrier device, such as a rescue mask. However, such equipment may not always be available. In these cases, mouth-to-mouth breathing has traditionally been the alternative, though many untrained rescuers hesitate to perform it, especially on strangers. This decision is ultimately a personal one for healthcare professionals. For untrained laypersons, compression-only CPR is considered an acceptable alternative. Similarly, if a healthcare provider in an out-of-hospital setting cannot perform rescue breathing due to a lack of a barrier device or other extenuating circumstances, compression-only CPR should be performed until EMS arrives.[10][11]

The cycle of 30 chest compressions followed by 2 rescue breaths should be continued until an automated external defibrillator becomes available or until additional help arrives. Once an automated external defibrillator is on scene, its pads should be applied to the front and back of the chest while minimizing any delay in resuming chest compressions. Most modern automated external defibrillators provide verbal instructions, automatically analyzing the cardiac rhythm and advising whether a shock is necessary. If a shock is advised, chest compressions should be paused, and everyone should stand clear while the automated external defibrillator delivers defibrillation. Immediately after the shock, or if no shock is advised, CPR should be resumed without delay, continuing the CAB sequence until further assistance or advanced care arrives.  

A quick physical exam focused on assessing palpable pulses and mental status is essential, as certain conditions, such as drug overdose or heavy alcohol intoxication, can mimic the presentation of cardiac arrest. In such cases, the individual may appear unresponsive or exhibit shallow breathing but still retain a pulse, making accurate assessment critical to avoid unnecessary chest compressions.

Pediatric Cardiopulmonary Resuscitation

Pediatric CPR is divided into 2 categories based on age—infant CPR applies to patients younger than 1, whereas child CPR applies from 1 year until puberty. From puberty onward, adult CPR guidelines should be followed. Although pediatric CPR follows the adult approach in many respects, key modifications exist.

For children, chest compressions are performed using the heel of 1 or both hands (depending on the child's size) placed over the lower half of the sternum. Compressions should be at a depth of 2 inches at a rate of 100 to 120 per minute. After 30 compressions, 2 breaths should be given, then compressions are resumed. The cycle of 30 compressions and 2 breaths should be continued until advanced help is available.

In infants, compressions are delivered using 2 fingers placed on the sternum just below the nipple line. The chest should be compressed to a depth of about 1.5 inches at a rate of 100 to 120 per minute. After 30 compressions, 2 breaths should be delivered, and the cycle should be repeated until professional help arrives.

In-Hospital Cardiopulmonary Resuscitation

In the hospital setting, multiple trained rescuers are typically available, and ventilation is commonly provided using a bag-valve-mask device. Proper use of the bag-valve-mask requires training and should be performed by qualified personnel. If the patient is not intubated, CPR is performed with 1 healthcare provider giving chest compressions and another delivering breaths using the bag-valve-mask. In this case, the compression-to-ventilation ratio changes to 15:2.

Once the patient is intubated, compressions should continue without interruption, and breaths are delivered independently at a rate of 10 per minute (1 breath every 6 seconds). Importantly, novice healthcare providers often tend to ventilate too quickly, which can be detrimental and should be avoided.

Complications

CPR can lead to various complications, both skeletal and visceral, which may impact patient outcomes. Skeletal injuries are among the most common, with rib fractures occurring in up to 70% of cases and sternal fractures in about 30% of cases, often due to prolonged or forceful chest compressions.[12]

Visceral injuries include contusions and lacerations to internal organs such as the heart, lungs, liver, and pericardium. Studies have documented cardiac and pulmonary contusions in more than 50% of CPR cases, along with occurrences of hemothorax and hemopericardium.[12] Cardiac injuries may involve transmural contusions or ruptures of the right atrium or aorta.

Acute lung injury, including CPR-associated lung edema, can result from aggressive compressions and poor ventilation techniques. Hemothorax and pneumothorax are also recognized complications, typically secondary to fractured ribs and lung trauma. Other potential injuries include retrosternal and mediastinal hematomas and liver lacerations, especially with mechanical CPR devices. 

Clinical Significance

The clinical significance of CPR includes its impact on patient outcomes, the potential for complications, and overall prognosis. CPR substantially improves survival in both out-of-hospital cardiac arrest and in-hospital cardiac arrest cases. Over the past 4 decades, global survival rates for out-of-hospital cardiac arrest cases have improved, with return of spontaneous circulation reported at 29.7%, survival rate to hospital admission at 22.0%, and discharge rate at 8.8%. Bystander CPR increases the chance of survival by 2 to 3 times. In in-hospital cardiac arrest, 66.9% of patients achieve return of spontaneous circulation, and 22.6% survive to discharge. However, survival likelihood decreases significantly with longer CPR durations.[13][14][15]

Overall prognosis following CPR depends on multiple factors, such as the length of resuscitation efforts, the presence of bystander intervention, and the speed of defibrillation. Favorable outcomes are more likely when CPR is initiated promptly and effectively, particularly in areas with robust emergency systems. Notably, survival rates drop to less than 1% when CPR exceeds 39 minutes. CPR remains a vital intervention that greatly enhances survival chances when applied early and correctly, as current AHA guidelines support.[16]

Enhancing Healthcare Team Outcomes

Improving patient-centered care, safety, outcomes, and team performance during CPR requires a comprehensive approach that includes clinical skills, ethical considerations, communication, and coordinated care systems. This approach ensures that resuscitation efforts are effective, respectful of patient preferences, and supported by well-trained, collaborative healthcare teams.

High-quality CPR depends on maintaining proper compression rate and depth while minimizing interruptions. Training programs should include simulation-based exercises, leadership development, and cognitive aids to reinforce best practices and reduce errors. The AHA recommends incorporating these strategies into life support training to enhance outcomes.[17]

Ethical responsibilities include respecting do-not-resuscitate orders and recognizing when CPR may be medically futile. Healthcare providers must weigh the urgency of intervention against patient preferences and prognosis.

Effective communication is critical during resuscitation. To improve coordination and performance, teams should have clear roles, a designated leader, and regular debriefings. A systems-level approach, including public CPR education, access to defibrillators, and structured emergency response systems, also supports better outcomes.[18][19]

Post-resuscitation care requires coordination across disciplines to manage ventilation, hemodynamics, and neurological function. Teamwork and leadership training have improved adherence to guidelines, communication, and overall CPR quality.[17]

Enhancing CPR outcomes involves a multifaceted strategy combining clinical training, ethical awareness, clear communication, and integrated care systems. These elements work together to ensure timely, effective, patient-centered interventions during resuscitation efforts.