Paul Aelen

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.

Dynamic prediction of ROSC: Is the art of prognostication in Resuscitation becoming science?

87 In this issue, Kim et al. challenge the reader with their anuscript entitled “Dynamic predication of patient outcomes uring ongoing cardiopulmonary resuscitation”.1 Those expecting alidation of a smart phone based App, have the concept right, but o need to be patient a little longer. The authors have chosen a core issue in resuscitation: when o start and when to stop.2 If we know, up front, whether what e intend to achieve could benefit that patient in their specific ituation at a specific point in time, imagine the impact on our art! Kim et al. use a standardized setting for this study. In their sysem, patients typically received BLS up to Emergency Department ED) admission, after which ACLS is started. Routine blood gas analsis is done at presentation. They limit themselves to patients with ngoing CPR at ED presentation, and with the first occurrence of OSC in the first 30 min of their treatment. Patients with ROSC at resentation, and those with ROSC after 30 min ACLS in the ED were xcluded from the main analysis. In essence, using data from some 727 patients, they created a odel which could predict ROSC likelihood and conditional probbilities for short and long term survival chance and quintessential oal of good neurological outcome. Specifically, this is the chance hat a specific patient, under the specific conditions at that moment n time within the ED has for these outcomes. In the model they sed parameters such as whether the arrest was witnessed, the nitial rhythm, ACLS duration and pCO2 at ED presentation.3,4 They hen used scenarios to test if the model would reproduce actual ndings. The authors note a number of interesting outcomes. Noteworhy are the biphasic survival probability for ROSC and the usefulness f an initial blood gas analysis. The first showed increasing ROSC hances from ED admission up to 10 min. Since in their study ALS as started at ED admission and the authors note that there are no ut-of-hospital TOR rules, delayed but advanced care in a controlled nvironment seems to offer ROSC opportunities. The authors also ntroduce blood gas values as variables: close to admission, which eflect both the prehospital as well as the initial ED care, and dd potential for ‘objectifying’ the internal environment and offer nsight in the potential for good outcome at that point.4 Physicians and scientists have sought the objective – right –