What physiological change occurs during CPR that is crucial for perfusion?

During cardiopulmonary resuscitation (CPR), the method of chest compressions creates a critical physiological change: increased intrathoracic pressure. When compressions are applied to the chest, the thoracic cavity is compressed, which increases the pressure within that space. This rise in intrathoracic pressure helps to facilitate blood flow back to the heart, especially during the release phase of compression, allowing the heart to refill with blood.

The increased pressure helps to create a pressure gradient that drives blood out of the heart and into systemic circulation, effectively maintaining perfusion to vital organs. This is particularly important in a cardiac arrest situation where normal cardiac function has ceased. The concept hinges on the principle that effective chest compressions can mimic the heart's pumping action, pushing blood through the arterial system even in the absence of a heartbeat.

Understanding this mechanism is vital for effective CPR performance because it emphasizes the importance of high-quality, continuous compressions with minimal interruptions to maintain that crucial intrathoracic pressure for adequate blood flow.