Background:
Continuing high quality chest compressions (CC) without interruption for active positive pressure ventilation (PPV) early in CPR has been demonstrated to improve patient outcomes in out-of-hospital cardiac arrest (OHCA). During the first minutes of CPR, passive oxygenation may be sufficient for oxygenating vital tissues. However, less is known about the later minutes of CPR. To evaluate this issue, in OHCA patients after hospital arrival, we quantified ventilation volumes during CCs in the ED.
Methods:
CPR quality metrics were obtained on patients who had CPR inside the ED with the E-Series defibrillator/monitor (Zoll Medical). Detailed ventilation data were obtained using a Non-Invasive Cardiac Output (NICO) Monitor (Philips/Respironics) with a CO2/flow sensor placed at the endotracheal tube. NICO waveform and breath-by-breath data were captured to measure ventilation volume associated with CCs.
Results:
Data files on 21 cardiac arrest patients who presented to the ED were included. [Male: 17, median age: 59 (IQR 47, 72)]. A total of 29,935 compressions (CCs) were analyzed [median depth 2.1 in (IQR=1.9, 2.5), median rate 126 CC/min (IQR=122-129). The median passive tidal volume during CCs was 5.8 mL, (IQR 3.4, 11.0). The highest volume was 124 mL, however 81% of the measured tidal volumes were <20 mL.
Conclusion:
This quantified analysis of ventilation volumes during chest compressions in the ED suggests that significant passive ventilation volumes may not occur later in CPR. Even in patients who were receiving effective compressions, passive tidal volumes were extremely low overall, suggesting that the value of compression only CPR may, in part, be due to the avoidance of the harmful effects of hyperventilation rather than any potential effect of passive ventilation.
Brain monitoring using near-infrared spectroscopy to predict outcome after cardiac arrest: a novel phenotype in a rat model of cardiac arrest
