Paul van Berkom

Does use of the CPREzy™ involve more work than CPR without feedback?

AIM Feedback during CPR may facilitate quality in chest compressions, but has also been associated with caregiver complaints such as stiff wrists, the need for more force and increased fatigue. This concern about extra work is, when using the CPREzy with its own spring-loaded surface, particularly relevant in the face of an increased number of successive compressions. This manuscript evaluates the objective workloads for caregivers with and without the CPREzy. MATERIALS AND METHODS An air pressure driven, piston device was used to generate controlled compressions in a manikin model. The pressure was applied for chest compressions with each of the following: the cylindrical end of the piston, a wooden block as dummy for the CPREzy, and the CPREzy itself. Three manikins with subjectively different spring compliances were selected for the tests. Series of 20 compressions were performed over a wide range of pressures. RESULTS No additional force is required to achieve a given depth of compression with or without the CPREzy. However, some additional work is required, ranging from 21 to 26.5%. This work is caused by the longer compression distance associated with the need to compress two springs (e.g. the CPREzy and the chest wall) instead of one (e.g. the chest wall). CONCLUSION The subjective feeling of increased rescuer fatigue with the CPREzy can, at least in part, be attributed to the extra work required for compressing the spring of the CPREzy. Improved accuracy in chest compression depth is likely to be another, more significant, factor in rescuer fatigue.

Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model

INTRODUCTION Reliable, non-invasive detection of return of spontaneous circulation (ROSC) with minimal interruptions to chest compressions would be valuable for high-quality cardiopulmonary resuscitation (CPR). We investigated the potential of photoplethysmography (PPG) to detect the presence of a spontaneous pulse during automated CPR in an animal study. METHODS Twelve anesthetized pigs were instrumented to monitor circulatory and respiratory parameters. Here we present the simultaneously recorded PPG and arterial blood pressure (ABP) signals. Ventricular fibrillation was induced, followed by 20 min of automated CPR and subsequent defibrillation. After defibrillation, pediatric-guidelines-style life support was given in cycles of 2 min. PPG and ABP waveforms were recorded during all stages of the protocol. Raw PPG waveforms were acquired with a custom-built photoplethysmograph controlling a commercial reflectance pulse oximetry probe attached to the nose. ABP was measured in the aorta. RESULTS In nine animals ROSC was achieved. Throughout the protocol, PPG and ABP frequency content showed strong resemblance. We demonstrate that (1) the PPG waveform allows for the detection of a spontaneous pulse during ventilation pauses, and that (2) frequency analysis of the PPG waveform allows for the detection of a spontaneous pulse and the determination of the pulse rate, even during ongoing chest compressions, if the pulse and compression rates are sufficiently distinct. CONCLUSIONS These results demonstrate the potential of PPG as a non-invasive means to detect pulse presence or absence, as well as pulse rate during CPR.

A ventilation technique for oxygenation and carbon dioxide elimination in CPR: Continuous insufflation of oxygen at three levels of pressure in a pig model

AIM Pulmonary ventilation remains an important part of cardiopulmonary resuscitation, affecting gas exchange and haemodynamics. We designed and studied an improved method of ventilation for CPR, constructed specifically to support both gas exchange and haemodynamics. This method uses continuous insufflation of oxygen at three levels of pressure, resulting in tri-level pressure ventilation (TLPV). We hypothesized that TLPV improves gas exchange and haemodynamics compared to manual gold standard ventilation (GSV). METHODS In 14 pigs, ventricular fibrillation was induced and automated CPR performed for 10 min with either TLPV or GSV. After defibrillation, CPR was repeated with the other ventilation method. Gas exchange and haemodynamics were monitored. Data are presented as mean±standard error of the mean. RESULTS TLPV was superior to GSV for PaO2 (163±36 mmHg difference; P=0.001), and peak AWP (-20±2 cmH2O difference; P=0.000) and higher for mean AWP (8±0.2 cmH2O difference; P=0.000). TLPV was comparable to GSV for CPP (5±3 mmHg difference; P=0.012), VCO2 (0.07±0.3 mL/min/kg difference; P=0.001), SvO2 (4±3%-point; P=0.001), mean carotid flow (-0.5±4 mL/min difference; P=0.016), and pHa (0.00±0.03 difference; P=0.002). The PaCO2 data do not provide a conclusive result (4±4 mmHg difference). CONCLUSION We conclude that the ventilation strategy with a tri-level pressure cycle performs comparable to an expert, manual ventilator in an automated-CPR swine model.