Cardiopulmonary resuscitation - Foundations of CPR

Cardiopulmonary Resuscitation (CPR) What is CPR and Why Do We Use It? Cardiopulmonary resuscitation (CPR) is an emergency procedure performed when someone's heart stops beating or breathing stops. It's designed to preserve brain function and maintain circulation until the person can be restored to normal breathing and heartbeat, or until professional medical help can take over. The fundamental goal of CPR is straightforward: deliver oxygenated blood to the brain and heart to prevent permanent tissue damage. Time is critical in this process. Brain cells can survive without blood flow for approximately four minutes before damage begins. After seven minutes of circulatory arrest, irreversible brain damage typically occurs. This is why CPR must begin immediately—every minute counts. The Main Components of CPR CPR has two primary components working together: Chest compressions are the primary technique. For adults, compressions must be performed at a depth of 5–6 cm at a rate of 100–120 compressions per minute. The rhythmic compression of the chest manually pumps blood out of the heart to deliver oxygenated blood to vital organs. It's important to note that compression rates exceeding 120 per minute can actually reduce venous return (blood flowing back to the heart), which decreases survival chances. This is why the 100–120 range is specified—it represents the "sweet spot" for effectiveness. Artificial ventilation provides oxygen by either mouth-to-mouth breathing or mechanical ventilation devices. However, modern CPR guidelines have shifted emphasis. For untrained rescuers, high-quality chest compressions are prioritized over ventilation. This recognizes that the continuous pumping action is more critical than perfect breathing ratios. Compression-to-Ventilation Ratios Different age groups have different recommended ratios: Adults: 30 compressions followed by 2 breaths (30:2) Children with two trained rescuers: 15 compressions followed by 2 breaths (15:2) The different ratios reflect developmental differences in how children's cardiovascular systems respond to resuscitation. When Should CPR Be Started? CPR is indicated for any unresponsive person with no breathing or only agonal gasps (gasping is not normal breathing and should be treated as respiratory arrest). There's an important distinction to understand: If a person has a pulse but is not breathing, ventilation should be prioritized over compressions. However, laypeople are instructed not to stop and check for a pulse—the reasoning is that untrained individuals often cannot accurately detect a pulse, and the seconds spent checking may delay critical compressions. Only trained healthcare providers should take time to assess pulses. Why Brain Function is So Vulnerable The brain's extreme sensitivity to oxygen deprivation is what makes CPR so urgent. Unlike some tissues that can survive brief periods without blood flow, brain cells begin experiencing damage within minutes. This is why the 4-minute and 7-minute windows are so important to remember—they define the window of opportunity for successful resuscitation without permanent brain damage. One exception worth understanding: Low body temperature can extend this tolerance window. In near-drowning cases, for example, cold water can lower body temperature and reduce the brain's oxygen demands, allowing for longer survival times without blood flow. This is why drowning victims in cold water may sometimes recover even after extended periods without breathing. Special Clinical Situations Traumatic Cardiac Arrest In cases of traumatic cardiac arrest (cardiac arrest caused by physical injury), CPR alone is considered insufficient to restore the heartbeat. However, CPR is still recommended while emergency teams work to identify and correct the underlying cause—such as a tension pneumothorax (collapsed lung) or pericardial tamponade (fluid around the heart compressing it). In these situations, CPR buys time for definitive surgical or emergency interventions. Drowning and Unconscious Children For drowning victims and unconscious children, the protocol differs slightly. Immediate CPR is prioritized before obtaining an automated external defibrillator (AED). This reflects the recognition that these populations particularly benefit from immediate oxygenation and circulation support.