Slide 1: A patient suffers from cardiac arrest and expires despite cardiopulmonary resuscitation (CPR). A few minutes after resuscitation is stopped, the patient achieves return of spontaneous circulation (ROSC). Question: How did this happen?

Slide 2: Answer: Auto-resuscitation is spontaneous ROSC after termination of resuscitation in cardiac arrest. The pathophysiology is thought to be a result of excessive positive pressure ventilation during resuscitation efforts. Excessive positive pressure ventilation without adequate time for exhalation leads to hyperinflation of the lungs, and consequently high intra-thoracic pressure.

Slide 3: High intra-thoracic pressure has two main consequences. One. It prevents critical CPR medications from reaching the heart, preventing their full effect. Two. It leads to a decrease in preload, preventing adequate circulatory pressures for appropriate resuscitation.

Slide 4: After resuscitative efforts are terminated and the patient is no longer receiving positive pressure ventilation, intra-thoracic pressure decreases. This decrease in intra-thoracic pressure allows for CPR medications to reach the heart, and simultaneously for preload to increase and spontaneous circulation to return.

Graphic showing the sequence of events. CPR stops leading to hyperinflation resolution. This leads to a decrease in intra-thoracic pressure and an increase in preload. The result of increased preload is adequate circulatory pressures and medications reach the heart. These, together, lead to return of spontaneous circulation.

Slide 5: This occurrence is also known as the “Lazarus Phenomenon,” a biblical reference to the raising of Lazarus from the dead. In one scoping review, 30% of patients who have Lazarus phenomenon make a good recovery, highlighting the importance of avoiding excessive ventilation during CPR.