Hyperventilation-Induced Hypotension During Cardiopulmonary Resuscitation

TLDR

Rescuers consistently hyperventilated patients during out‑of‑hospital CPR, as shown by a clinical observational study. The study aimed to quantify excessive ventilation during CPR in humans and determine whether similar rates in animal models decrease coronary perfusion pressure and survival. Hemodynamic effects were examined in pigs in cardiac arrest ventilated at 12, 20, or 30 breaths per minute, and survival was compared across groups ventilated at 12, 30, or 30 with CO₂. Human patients received an average of 30 breaths per minute during CPR and none survived, whereas in pigs higher ventilation rates increased intrathoracic pressure, lowered coronary perfusion pressure, and reduced survival from 86 % at 12 breaths per minute to 14 % at 30 breaths per minute and 14 % with CO₂.

Abstract

A clinical observational study revealed that rescuers consistently hyperventilated patients during out-of-hospital cardiopulmonary resuscitation (CPR). The objective of this study was to quantify the degree of excessive ventilation in humans and determine if comparable excessive ventilation rates during CPR in animals significantly decrease coronary perfusion pressure and survival.In humans, ventilation rate and duration during CPR was electronically recorded by professional rescuers. In 13 consecutive adults (average age, 63+/-5.8 years) receiving CPR (7 men), average ventilation rate was 30+/-3.2 per minute (range, 15 to 49). Average duration per breath was 1.0+/-0.07 per second. No patient survived. Hemodynamics were studied in 9 pigs in cardiac arrest ventilated in random order with 12, 20, or 30 breaths per minute. Survival rates were then studied in 3 groups of 7 pigs in cardiac arrest that were ventilated at 12 breaths per minute (100% O2), 30 breaths per minute (100% O2), or 30 breaths per minute (5% CO2/95% O2). In animals treated with 12, 20, and 30 breaths per minute, the mean intrathoracic pressure (mm Hg/min) and coronary perfusion pressure (mm Hg) were 7.1+/-0.7, 11.6+/-0.7, 17.5+/-1.0 (P<0.0001), and 23.4+/-1.0, 19.5+/-1.8, and 16.9+/-1.8 (P=0.03), respectively. Survival rates were 6/7, 1/7, and 1/7 with 12, 30, and 30+ CO2 breaths per minute, respectively (P=0.006).Professional rescuers were observed to excessively ventilate patients during out-of-hospital CPR. Subsequent animal studies demonstrated that similar excessive ventilation rates resulted in significantly increased intrathoracic pressure and markedly decreased coronary perfusion pressures and survival rates.