Expanding automatic external defibrillators to include automated detection of cardiac, respiratory, and cardiorespiratory arrest
University of California, Los Angeles, Los Ángeles, California, United States Critical Care Medicine
(Impact Factor: 6.31).
05/2002; 30(4 Suppl):S176-8. DOI: 10.1097/00003246-200204001-00012
The new Guidelines of the American Heart Association state that lay rescuers can no longer rely on the manual pulse check to confirm cardiac arrest in an unresponsive patient. We were therefore prompted to develop a method for automated determination of the presence or absence of cardiac contraction and breathing. The technique was designed to be incorporated into conventional automated external defibrillators and to work in conjunction with the information derived from rhythm analyses by the automated defibrillator. Using conventional electrocardiographic sensing and defibrillation electrodes, the transthoracic impedance was measured by passing a constant amplitude alternating current of 5 mA through the thorax at a frequency of 35 kHz. In five anesthetized male domestic swine, we observed pulses that were coincident with cardiac contraction documented by esophageal echocardiography. In addition, we observed larger signals of lower frequency that were time related to ventilation and documented by capnography. Both signals disappeared after inducing ventricular fibrillation. The impedance measurement identified respiratory arrest in anesthetized animals and primary cardiac arrest after ventricular fibrillation was induced. The cardiac arrest detector is therefore likely to augment the current information provided by automated defibrillators and to allow for more precise verbal prompting of lay rescuers.
- "This method, as reviewed by Morimoto et al. , is generally a good indicator for the patient's return of spontaneous circulation, but it is not always effective in detecting the absence of circulation (i.e., it cannot reliably detect pulselessness) because the ETlevel may significantly differ between cardiac arrest patients. A third possible monitoring approach, which is recently proposed by Pellis et al. , is to measure the transthoracic electrical impedance that varies during cardiac contraction and breathing. Nevertheless, this method can only provide an indirect indication for the return of circulation, and it has so far been studied merely in the context of cardiac arrest detection. "
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ABSTRACT: During cardiac arrest emergencies, lay rescuers are required to manually check the patient's carotid pulse after the delivery of defibrillation shocks to assess the cardiac resuscitation progress of the patient. As a more automated way of monitoring the resuscitation progress, a new Doppler-ultrasound-based carotid pulse assessment approach is presented in this paper. The method works by analyzing the temporal aperiodicity of Doppler shifts seen in the ultrasound echoes returned from the patient's carotid arteries. As a quantitative investigation with this method, we derived a new measure called the pulselessness indicator to assess whether a carotid pulse is absent based on the given Doppler information. To study the performance of the new carotid pulse checking method, we built a multi-channel CW Doppler prototype device to acquire Doppler data in vivo during cardiac arrest experiments conducted on five different swines and computed pulselessness indicator estimates with these data. Our results indicated that the Doppler-based pulse checking approach has good sensitivity and specificity: it had a pulselessness detection rate greater than 0.9 for a given false alarm rate of 0.05. As a further analysis, the prototype device was applied to other experiments where the swine had suffered cardiac arrest for over five minutes. It showed a consistent assessment performance on the monitoring of the swine's resuscitation progress after defibrillation and chest compressions.
IEEE Transactions on Biomedical Engineering 04/2008; 55(3-55):1072 - 1081. DOI:10.1109/TBME.2007.908104 · 2.35 Impact Factor
Available from: Jo Kramer-Johansen
- "Due to redistribution of blood in the thorax and changes in blood velocity, there is a small temporary change in impedance ( m ) with each pulse-generating heart beat. The defibrillator is already continuously measuring the impedance between self-adhesive defibrillator pads, and information about the possible temporary impedance changes occuring synchronized with an organized rhythm on the electrocardiogram (ECG) might help distinguish between PR and PEA , . If AEDs could be modified with the ability to automatically discriminate between PEA and PR, the no-flow time could be significantly reduced and thereby have a positive effect on the chance of survival from cardiac arrest. "
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ABSTRACT: The main problem during pulse check in out-of-hospital cardiac arrest is the discrimination between normal pulse-generating rhythm (PR) and pulseless electrical activity (PEA). It has been suggested that circulatory information can be acquired by measuring the thoracic impedance via the defibrillator pads. To investigate this, we performed an experimental study where we retrospectively analyzed 127 PEA segments and 91 PR segments out of 219 and 113 segments. A PEA versus PR classification framework was developed, that uses short segments (< 10 s) of ECG and impedance measurements to discriminate between the two rhythms. Using realistic data analyzed over a duration of 3 s, our system correctly identifies 90.0% of the segments with rhythm being pulseless electrical activity, and 91.5% of the normal pulse rhythm segments. Automatic identification of pulse could avoid unnecessary pulse checks and thereby reduce no-flow time and potentially increase the chance of survival.
IEEE Transactions on Biomedical Engineering 02/2008; 55(1):60-8. DOI:10.1109/TBME.2007.910644 · 2.35 Impact Factor
Available from: Trygve Eftestøl
- "It would be valuable for a rescuer to have circulatory information about a patient undergoing resuscitation due to cardiac arrest. It has been suggested  to measure the thoracic impedance through the defibrillator pads, and thereby acquire information related to blood circulation . We wanted to explore the information that could be drawn from such measurements, and therefore simultaneously recorded the thoracic impedance by using standard defibrillator pads and the blood pressure arterially from 79 patients undergoing resuscitation and 37 hemodynamically stable patients. "
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ABSTRACT: It has been suggested to acquire circulatory information from patients undergoing resuscitation from cardiac arrest by analyzing their thoracic electrical impedance using modified automated external defibrillators (AEDs). To investigate the potential of this idea, we studied the correlation between two impedance-derived parameters related to circulation, the negative peak of the impedance fluctuation (Z<sub>peak</sub>) and its first time derivative (dZ<sub>peak</sub>), and arterial blood pressure measurements in 26 patients undergoing resuscitation and 32 hemodynamically stable patients. The highest correlation coefficient, rho=0.4338 was found between the systolic blood pressure and the magnitude of the negative peak of the first time derivative of the impedance. The poor correlation indicates that the impedance-derived parameters are not suitable for quantification of circulation, but can be used to indicate circulation
Computers in Cardiology, 2005; 10/2005
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