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PubMed2000

Minimally invasive direct cardiac massage versus closed-chest cardiopulmonary resuscitation in a porcine model of prolonged ventricular fibrillation cardiac arrest.

Open chest cardiac massage has been shown to be superior to closed-chest cardiopulmonary resuscitation for both hemodynamics produced during resuscitation and ultimate resuscitation success. The inexperience of many rescuers with emergency thoracotomy, along with the associated morbidity contributes to the continued reluctance in the use of invasive cardiopulmonary resuscitation techniques. A device has been developed for performing 'minimally invasive' direct cardiac massage. This technique was compared to standard closed-chest CPR for resuscitation results in 20 swine during prolonged ventricular fibrillation cardiac arrest. Minimally invasive direct cardiac massage was superior to closed-chest CPR for return of spontaneous circulation (7/10 vs. 2/10; P<0.02) and coronary perfusion pressure at 30 min of CPR (17+/-9 vs. 6+/-6 mmHg; P<0.05). No significant injuries altering outcome were found with the invasive device. Throughout most of the time course of the study no significant differences in end-tidal expired carbon dioxide levels were noted. Nor were there any differences in 24-h survival. Improvements in assuring proper placement of the device on the epicardium should make this technique a potent advanced cardiac life support adjunct.

Analysis of Variance↗
PubMed2001

Fibrillation power, an alternative method of ECG spectral analysis for prediction of countershock success in a porcine model of ventricular fibrillation.

BACKGROUND: Noninvasive prediction of defibrillation success after cardiac arrest and cardiopulmonary resuscitation (CPR) may help in determining the optimal time for a countershock, and thus increase the chance for survival. METHODS: In a porcine model (n=25) of prolonged cardiac arrest, advanced cardiac life support was provided by administration of two or three doses of either vasopressin or epinephrine after 3 or 8 min of basic life support. After 4 min of ventricular fibrillation and 18 min of life support, defibrillation was attempted. The denoised power spectral density of 10 s intervals of the ventricular fibrillation electrocardiogram (ECG) was estimated from averaged and smoothed Fourier transforms. We have eliminated the spectral contribution of artifacts from manual chest compressions and provide a definition for the contribution of ventricular fibrillation to the power spectral density. This contribution is quantified and termed "fibrillation power". RESULTS: We tested fibrillation power and two established methods in their discrimination of survivors (n=16) vs. non-survivors (n=9) in the last minute before the countershock. A fibrillation power > or =79 dB predicted successful defibrillation with sensitivity, specificity, positive predictive value and negative predictive value of 98%, 98%, 99% and 97% while a mean fibrillation frequency > or =7.7 Hz was predictive with 85%, 83%, 90% and 77% and a mean amplitude > or =0.49 mV was predictive with 95%, 90%, 94% and 91%. CONCLUSIONS: We suggest that fibrillation power is an alternative source of information on the status of a fibrillating heart and that it may match the established mean frequency and amplitude analysis of ECG in predicting successful countershock during CPR.

Animals↗
PubMed2002

Optimizing ventilation in conjunction with phased chest and abdominal compression-decompression (Lifestick) resuscitation.

The best method for employment of phased chest and abdominal compression-decompression (Lifestick) cardiopulmonary resuscitation (CPR) has yet to be determined. Of particular concern with using this technique is the combining of ventilation with the phased compressions and decompressions. Twenty domestic swine (50+/-1 kg) were equally divided into four groups. Following 10 min of untreated VF, CPR was begun. Group 1 received Lifestick (LS) CPR with only passive ventilation ('passive'); Group 2 received LS-CPR with synchronized positive pressure ventilations (ppv) at a chest compression ratio of 15:2 (15:2 S); Group 3 had LS-CPR with synchronized ppv at 5:1 (5:1 S); and Group 4 received LS-CPR with asynchronous ppv at 5:1 (5:1 A). Endpoints included hemodynamics, blood gases, minute ventilation, and 24 h outcome. Asynchronous ventilation (5:1 A) had significantly worse hemodynamics including aortic and right atrial systolic, aortic diastolic, and coronary perfusion pressures than the other groups (P<0.05). Passive ventilation had the poorest arterial and mixed venous blood gases (P<0.05), but did not differ from 15:2 S in minute ventilation produced (8 vs 10 l/min). No differences in outcome were seen. The ventilation technique combined with LS-CPR can make a significant difference in hemodynamics as well as ventilation. Optimizing other forms of basic and advanced cardiac life support through different ventilation methods deserves new consideration, including a re-examination of the current single rescuer recommendation of a 15:2 ratio. Optimal ventilation strategy when using the LS device at 60 compressions per min appears to be 5:1 S. Such data is important for conducting clinical trials with this new CPR adjunct.

Abdomen↗
PubMed2002

Simultaneous sterno-thoracic cardiopulmonary resuscitation improves short-term survival rate in canine cardiac arrests.

We have reported previously that simultaneous sterno-thoracic cardiopulmonary resuscitation (SST-CPR) using a device that compresses the sternum and constricts the thorax circumferentially during a compression systole that can be achieved using standard cardiopulmonary resuscitation (STD-CPR). This study was designed to assess whether SST-CPR improves the survival rate of dogs with cardiac arrest compared with STD-CPR. Twenty-nine mongrel dogs (19-31 kg) were enrolled in this study. After 4 min of ventricular fibrillation induced by an AC current, animals were randomized to be resuscitated by either STD-CPR (n=15) or SST-CPR (n=14). Defibrillation was attempted 10 min after the induction of cardiac arrest. Standard advanced cardiac life support was started if defibrillation was unsuccessful. Aortic blood pressure, coronary perfusion pressure, and end tidal CO(2) tension were measured during CPR and the post-resuscitation period. Survival was determined 12 h after the induction of cardiac arrest. SST-CPR resulted in a significantly (P<0.001) higher systolic arterial pressure (91+/-47 vs 47+/-24 mmHg), diastolic pressure (43+/-24 vs 17+/-10 mmHg), coronary perfusion pressure (35+/-25 vs 13+/-9 mmHg), and end tidal CO(2) tension (9+/-4 vs 3+/-2 mmHg). Two of 15 animals (13%) resuscitated by STD-CPR and seven of 14 animals (50%) resuscitated by SST-CPR survived for 12 h after cardiac arrest (P<0.05). In conclusion, SST-CPR improves the short-term survival rate in canine cardiac arrest compared with STD-CPR.

Animals↗
PubMed2002

Dynamic computed tomography: a novel technique to study lung aeration and atelectasis formation during experimental CPR.

OBJECTIVE: To develop an image based technique to study the effect of different ventilatory strategies on lung ventilation and alveolar recruitment during cardiopulmonary resuscitation (CPR). DESIGN: (1) Technical development of the following components: (a) construction of an external chest compression device, which does not interfere with CT imaging, and (b) development of a software tool to detect lung parenchyma automatically and to calculate radiological density parameters. (2) Feasibility studies: three strategies of CPR ventilation were performed and imaged in one animal each (pigs, 25 kg): volume-constant ventilation (VCV), no ventilation, or continuous airway pressure (CPAP). One minute after induction of circulatory arrest inside the CT scanner, external chest compressions started at a rate of 100 cpm, and one of the ventilation modes was initiated. After 1 min, intravenous epinephrine was added as a bolus (40 microg/kg), followed by a continuous infusion (13 microg/kg per min). Six minutes later, dynamic CT acquisitions (temporal resolution: 100 ms) commenced. Simultaneously, arterial blood gases, acid base status and haemodynamics were sampled. RESULTS: Using a modified chest compression device, dynamic CT acquisitions are feasible during closed-chest CPR. In three pilot experiments with different ventilation strategies, the dedicated software tool allowed to quantify ventilated, atelectatic and over-distended fractions of total lung area. VCV showed a large amount of atelectasis, which was recruited during every respiratory cycle. No ventilation led to atelectasis to govern over 50% of the total lung area. CPAP caused less atelectasis as VCV, and no cyclic recruitment and de-recruitment phenomena were observed. CONCLUSIONS: We demonstrate a novel experimental set up, which allows quantification of different lung compartments during ongoing CPR and may become useful in comparing the direct pulmonary effects of different ventilatory strategies in the settings of Basic and Advanced Cardiac Life Support.

Animals↗
PubMed2003

A comparison of alpha-methylnorepinephrine, vasopressin and epinephrine for cardiac resuscitation.

The objective of this research was to compare the effects of an alpha- and beta-adrenergic agonist, epinephrine, a selective alpha(2)-adrenergic agonist, alpha-methylnorepinephrine (alpha-MNE), and a non-adrenergic vasopressin on post-resuscitation myocardial function and duration of survival. Epinephrine continues to be the primary adrenergic agent for advanced cardiac life support. However, its major inotropic actions and especially its beta-adrenergic and, to a lesser extent, its alpha(1)-actions increase the severity of global ischemia during cardiac arrest and adversely affect post-resuscitation myocardial function and survival. We had previously observed significantly better outcomes with a selective alpha(2)-adrenergic agonist when compared with epinephrine. Non-adrenergic vasopressin also has promise of more favorable actions. The present study was, therefore, undertaken to compare a selective alpha(2)-adrenergic vasopressor drug with vasopressin, epinephrine, and saline placebo. Ventricular fibrillation (VF) was induced in 20 Sprague-Dawley rats. Mechanical ventilation and precordial compression were initiated after 8 min of untreated VF. About 2 min later, alpha-MNE in a dose of 100 microgram/kg, vasopressin in a dose of 0.4 U/kg, epinephrine in a dose of 30 microgram/kg, or saline control was administered. Defibrillation was attempted after 6 min of CPR. Left ventricular pressure, dP/dt(40), -dP/dt, and cardiac index were measured for an interval of 240 min after resuscitation. Except for saline controls, comparable increases in coronary perfusion pressure (CPP) were observed after each drug intervention. All animals were successfully resuscitated. Post-resuscitation myocardial function and survival were significantly better in animals treated with alpha-MNE. Both post-resuscitation myocardial function and survival were most improved after administration of the selective alpha(2)-adrenergic agonist, intermediate after vasopressin and least after epinephrine and saline placebo.

Analysis of Variance↗
PubMed2003

Dispatcher assisted CPR: implementation and potential benefit. A 12-year study.

OBJECTIVES: Our objectives are to describe details of the dispatcher assisted cardiopulmonary resuscitation (CPR) instruction program we implemented during a 12 years study and to provide estimates of the potential number of out-of-hospital cardiac arrests that might benefit from such instruction based on data from the last 77 months. METHODS: Basic data were obtained for all episodes of out-of-hospital cardiac arrest in the city of Seattle, as well as all emergency medical services (EMS) dispatches for suspected cardiac arrest. In addition to EMS run reports, data sources included audio tapes of dispatches, and interviews of callers. These data were used in a potential benefit analysis. RESULTS: Over a period of 77 months, 54% (3320/6130) of cardiac arrests received advanced cardiac life support (ACLS) by Seattle Fire Department emergency medical technicians (EMTs) and paramedics. We estimated that 29.9% (994/3320) of cardiac arrests in Seattle treated by EMS could have theoretically benefited from dispatcher assisted CPR. No serious adverse consequences of a dispatcher assisted CPR program were observed. Failure to identify a cardiac arrest by dispatchers was largely attributed to deviation from a well-defined protocol. However, non-arrests identified, initially as arrests appeared to be unavoidable. CONCLUSIONS: In the city of Seattle, some 29.9% of all out-of-hospital cardiac arrest victims who received ACLS had the potential to benefit from dispatcher assisted CPR.

Cardiopulmonary Resuscitation↗
PubMed1997

Predicting survival from out-of-hospital cardiac arrest: a multivariate analysis.

From 954 attempts to resuscitate patients from out-of-hospital cardiac arrest two datasets were derived, namely 861 cases of cardiac arrest and 906 cases of either cardiac or primary respiratory arrest. For each dataset, multivariate analysis was performed by fitting a number of explanatory variables with respect to the outcomes of admission to hospital and discharge home in logistic regression models. There were numerous interactions between these variables. Being conscious at the time of the arrival of the ambulance crew and subsequently having cardiac arrest strongly predicted survival, as did both the presence of a witness to the arrest and the initiation of cardiopulmonary resuscitation (CPR) by a bystander; this latter effect was a marker for early CPR. The strongest predictor of a poor outcome was delay to CPR or delay to advanced cardiac life support.

Age Distribution↗
PubMed1997

The decision to terminate resuscitative efforts: results of a questionnaire.

Despite all the progress made in emergency medicine, out-of-hospital resuscitative efforts still remain unsuccessful in the majority of cases and a decision concerning termination of cardiopulmonary resuscitation (CPR) has to be made. We used a multi-question survey to assess the attitude of emergency physicians towards the duration of an unsuccessful resuscitation attempt in non-traumatic cardiac arrest, and to identify the criteria affecting the decision to terminate CPR in the prehospital setting. More than 400 physicians participated in the inquiry on CPR in adults. If spontaneous circulation cannot be restored, the majority (65%) abandon the resuscitation attempt at the latest after performing advanced cardiac life support for 45 min. The participants indicated the following factors as criteria for the termination of unsuccessful CPR: pre-existing diseases (92%), presumed interval between onset of arrest and application of CPR (92%), duration of the resuscitation attempt (90%), age of the patient (89%), electrocardiographic (ECG) alterations such as persistent asystole/ventricular fibrillation or electromechanical dissociation (83%), persistent fixed and dilated pupils (78%), lack of brain stem reflexes (31%), body temperature (12%) and suspected drug intoxication (8%). The answers reflect the physicians opinions on termination of CPR even if they do not present real decisions under emergency conditions. The results indicate that in addition to the failure to restore spontaneous circulation, other factors are involved in decision making at the scene. A high rate of respondents include criteria of weak diagnostic value such as the pupillary status, or factors of doubtful prognostic significance such as the patient's age. Concerning the patient's history and underlying diseases, the emergency physician often has to resort to presumptions. We conclude that the decision to terminate CPR is made by most physicians considering the specific circumstances of the cardiac arrest.

Adult↗
PubMed1997

Magnesium in cardiac arrest (the magic trial).

The prognosis of out of hospital cardiac arrest (OHCA) is dismal. Recent reports indicate that high dose magnesium may improve survival. A prospective randomized double blind placebo controlled trial was conducted at the emergency department (ED) of Royal Perth Hospital, a University teaching hospital. Patients with OHCA of cardiac origin received either 5 g MgSO4 or placebo as first line drug therapy. The remainder of their management was standard advanced cardiac life support (ACLS). Study endpoints were: (1) ECG rhythm 2 min after the trial drug; (2) return of spontaneous circulation; (3) survival to leave the ED; (4) survival to leave intensive care; and (5) survival to hospital discharge. Of 67 patients enrolled, 31 received magnesium and 36 placebo. There were no significant differences between groups for all criteria, except that there were significantly more arrests witnessed after arrival of EMS personnel in the magnesium group (11 or 35% vs 4 or 11%). Return of spontaneous circulation occurred in seven (23%) patients receiving magnesium and eight (22%) placebo. Four patients in each group survived to leave the ED and one from the magnesium group survived to hospital discharge. There were no survivors in the placebo group. In this study, the use of high dose magnesium as first line drug therapy for OHCA was not associated with a significantly improved survival. Early defibrillation remains the single most important treatment for ventricular fibrillation (VF). Further studies are required to evaluate the role of magnesium in cardiac and cerebral resuscitation.

Aged↗
PubMed1997

Adenosine receptor antagonism in refractory asystolic cardiac arrest: results of a human pilot study.

PRIMARY OBJECTIVE: To determine if adenosine receptor antagonism has any beneficial impact on victims of asystolic cardiac arrest and whether or not it warrants further clinical study as a treatment for cardiac asystole. MATERIALS AND METHODS: A 6-month prospective, randomized, double-blinded, placebo-controlled trial, set in an urban emergency medical services system, in adults with nontraumatic asystolic out-of-hospital cardiac arrest. Patients in whom standard advanced cardiac life support pharmacotherapy failed were randomized to receive placebo or aminophylline, a nonspecific competitive adenosine receptor antagonist. Rhythms were recorded before and after intervention. RESULTS: Twenty-two patients were appropriately entered into the trial. Eight patients served as controls and 14 patients received aminophylline. The groups were similar in all measured parameters except for initial rhythm. None of the patients in the placebo group responded to the intervention. Half of the patients in the treatment group had return of organized cardiac electrical activity. CONCLUSION: Our results suggest that adenosine receptor antagonism may have a role in the treatment of cardiac asystole. Further clinical studies to validate these findings and clarify the appropriate use of adenosine receptor antagonists in cardiac asystole may be justified.

Adult↗
PubMed1998

Hemodynamic effects of repeated doses of epinephrine after prolonged cardiac arrest and CPR: preliminary observations in an animal model.

STUDY PURPOSE: To assess the hemodynamic response to repeated doses of epinephrine (EPI) in an animal model of prolonged cardiac arrest and CPR. DESIGN: Basic laboratory investigation. Fourteen canines were subjected to electrically induced ventricular fibrillation (VF) followed by 7.5 min of VF without CPR. INTERVENTIONS: After 7.5 min of VF, manual closed-chest CPR (80-100 compressions per minute, compression to ventilation ratio 8:1) was initiated. Countershocks were performed, recommended advanced cardiac life support drugs were given, and CPR was continued until restoration of spontaneous circulation (ROSC) or for 20 min. Epinephrine, 1 mg (approximately 0.04 mg kg(-1)), was administered when indicated and at recommended time intervals. METHODS: Aortic and right atrial pressures were measured with micromanometer catheters before and after EPI, and CPR coronary perfusion pressure (CPP) was calculated (CPR diastolic aortic to right atrial pressure difference). Survival was defined as maintenance of ROSC for 30 min. RESULTS: Countershocks after 7.5 min resulted in asystole in ten animals and persistant VF in four. In those animals successfully resuscitated (n = 3), the change in CPP was 21 +/- 11 mm Hg after the first dose of EPI. Only one animal required a second dose of EPI. The majority of the study group (n = 11) could not be resuscitated. The increase in CPP after EPI averaged only 3 +/- 2 mm Hg and subsequent doses produced no significant effect on CPP (2 +/- 4 mm Hg). CONCLUSIONS: The hemodynamic response to the first dose of EPI determines if the critical CPP needed for ROSC and survival will occur. Repeat doses of EPI do not appear to improve CPP to a degree to affect clinically meaningful measures of outcome, i.e., successful countershock and survival.

Adrenergic alpha-Agonists↗
PubMed1998

Transthoracic defibrillation: does electrode adhesive pad position alter transthoracic impedance?

Successful termination of ventricular fibrillation by transthoracic shocks is dependent on achieving adequate current flow, which in turn is governed by transthoracic impedance (TTI). The American Heart Association (AHA) Advanced Cardiac Life Support textbook recommends three electrode positions for defibrillation: (1) anterior-apex, (2) apex-posterior and (3) anterior-posterior. However, there are few data available comparing TTI of these positions. To study this, we applied large (78 cm2) self-adhesive monitor-defibrillator pads to 20 subjects (ten male, ten female, ages 21-79) and measured TTI using a validated test-pulse technique which does not require actual shocks. We performed two studies. In Study 1 (all 20 subjects) the electrode pads were applied in the three positions recommended by the AHA, with the posterior electrode placed in the right infrascapular location. All TTI measurements were made at end-expiration and body surface area (BSA) was recorded. The results (TTI, omega, mean +/- S.D.) for the respective positions were the following: anterior-apex, 82.0+/-24.7; apex-posterior, 71.2+/-23.5; anterior-posterior, 77.0+/-24.7 (P NS). In Study 2 (six subjects) we compared the effect of right vs. left infrascapular posterior electrode placement (TTI, omega): apex-right infrascapular (RIS), 76.8+/-18.4; apex-left infrascapular (LIS), 72.1+/-18.7; anterior-RIS, 72.5+/-19.4; anterior-LIS, 71.6+/-18.6 (P NS). Correlation of TTI (anterior-apex placement) with BSA: TTI = 15.9 (BSA) + 46.7, r = 0.60, P < 0.01; the correlations of TTI and BSA were similar in the other two electrode positions. Thus, the three AHA-recommended electrode positions for transthoracic defibrillation have equivalent and acceptable TTIs; current flow should be similar using any of these positions. Furthermore, the posterior electrode may be placed in either the right or the left infrascapular position without affecting TTI. TTI is related to BSA in any of the three recommended positions; patients with high BSA and TTI may require higher energy selection to achieve defibrillation.

Adult↗
PubMedDate not supplied

Training needs and qualifications of anaesthesiologists not exposed to ALS.

OBJECTIVES: To establish which needs exist for specific training in Advanced Cardiac Life Support (ALS) in anaesthesiology residents and interns not exposed to structured ALS courses. METHODS: 48 residents, and seven interns accepted for training in anaesthesiology, were tested in a spontaneous, blind, cross-sectional, prospective assessment using a recording manikin with validated scoring system, a questionnaire, and 35 multiple-choice questions. RESULTS: 65% admitted not having had any CPR training within the last 2 years. The answers were correct in 55 +/- 14% of the cases, increasing significantly with the length of training (P = 0.001). One-rescuer CPR skills were inadequate: only 13% (n = 7) of participants scored within acceptable limits when using the Berden Scoring system (Berden et al., Resuscitation 1992;13:31-41), which assigned weighted error points to BLS skills. No correlation with skill was noted with increased length of residency, confidence, ER or ICU experience, or participation in CPR-incidents. CONCLUSIONS: Anaesthesiology residents and interns were not able to demonstrate BLS skills properly even while in training and did not recognize this themselves. CPR-related knowledge is poor and increases only incidentally over the years of residency even though participants were frequently confronted with seminars and resuscitation situations, and see protocols daily. The use of multiple-choice questions and the Berden scoring system avoids difficulties in evaluating case-scenario type of tests. We suggest that trainees are motivated to take part in standardized, intensive, recognised ALS courses which emphasize BLS skills and require (re)certification.

Adult↗
PubMed1999

Aminophylline in undifferentiated out-of-hospital asystolic cardiac arrest.

PRIMARY OBJECTIVE: To determine if the introduction of intravenous aminophylline, a nonspecific adenosine receptor antagonist, into the resuscitation algorithm of asystole will increase return of spontaneous circulation when used in undifferentiated prehospital cardiac arrest. METHODS: An urban, prehospital, prospective, randomized, double-blind, placebo-controlled trial of nonpregnant normothermic adults suffering nontraumatic out-of-hospital asystolic cardiac arrest. Subjects were treated in accordance with published advanced cardiac life support guidelines and standard pharmacotherapy. They were randomly assigned to receive either placebo or aminophylline along with the initial boluses of atropine and epinephrine. Cardiac rhythms and carotid pulses were monitored throughout the resuscitation. RESULTS: Eighty-two patients were entered into the trial. Forty-five patients were assigned to the placebo group and 37 received aminophylline. Nine of 45 controls (20%; 95% CI 10-35%) achieved return of spontaneous circulation compared to ten of 37 (27%; 95% CI 14-44%) in the aminophylline group. CONCLUSIONS: We were not able to show a statistically significant improvement in return of spontaneous circulation when aminophylline was given during the early resuscitation phase of undifferentiated asystolic cardiac arrest in the prehospital setting with this sample size.

Aged↗
PubMed1977

Cardiac arrest in the Emergency Medical Service System: guidelines for resuscitation.

A two-year study of 198 consecutive patients treated for cardiac arrest in the emergency department at Stanford University Medical Center was undertaken. The relatively poor overall survival rate of 3% and the complexity of deciding how to treat cardiac arrest victims suggest the need for guidelines to assist the emergency physician when resuscitating cardiac arrest patients. From the above study and a survey of the literature, the authors formulated the following guidelines of when resuscitation should be discontinued or not attempted: Cases of apnea and pulselessness known to have exceeded 10 minutes, no response after more than 30 minutes of advanced cardiac life support (ACLS), no ventricular EKG activity after more than 10 minutes of ACLS, and preexisting terminal illness.

Adult↗
PubMed1979

Incidence, etiology, and outcome of pulseless idioventricular rhythm treated with dexamethasone during advanced CPR.

The cardiac resuscitation records of 458 patients who received advanced cardiac life support at Detroit General Hospital during the last two years were reviewed to identify patients who had pulseless idioventricular rhythm (PIVR) recognized and treated with dexamethasone. Twenty-five cases were identified. The initial successful resuscitation rate of 52% in these patients contrasts sharply with other published data indicating 100% failure with the use of conventional chronotropic drugs. The most common etiology of cardiac arrest in our patients who display PIVR during resuscitation is hypoperfusion shock. Dexamethasone may counteract the lethal arrhythmia by causing the release of aditional adenosine triphosphate into the cytoplasm from the mitochondria.

Adenosine Triphosphate↗
PubMed1998

Effectiveness of mechanical versus manual chest compressions in out-of-hospital cardiac arrest resuscitation: a pilot study.

A prospective, randomized effectiveness trial was undertaken to compare mechanical versus manual chest compressions as measured by end-tidal CO2 (ETCO2) in out-of-hospital cardiac arrest patients receiving advanced cardiac life support (ACLS) resuscitation from a municipal third-service, emergency medical services (EMS) agency. The EMS agency responds to approximately 6,700 emergencies annually, 79 of which were cardiac arrests in 1994, the study year. Following endotracheal intubation, all cardiac arrest patients were placed on 100% oxygen via the ventilator circuit of the mechanical cardiopulmonary resuscitation (CPR) device. Patients were randomized to receive mechanical CPR (TCPR) or human/manual CPR (HCPR) based on an odd/even day basis, with TCPR being performed on odd days. ETCO2 readings were obtained 5 minutes after the initiation of either TCPR or HCPR and again at the initiation of patient transport to the hospital. All patients received standard ACLS pharmacotherapy during the monitoring interval with the exception of sodium bicarbonate. CPR was continued until the patient was delivered to the hospital emergency department. Age, call response interval, initial electrocardiogram (ECG) rhythm, scene time, ETCO2 measurements, and arrest outcome were identified for all patients. Twenty patients were entered into the study, with 10 in each treatment group. Three patients in the TCPR group were excluded. Measurements in the HCPR group revealed a decreasing ETCO2 during the resuscitation in 8 of 10 patients (80%) and an increasing ETCO2 in the remaining 2 patients. No decrease in ETCO2 was noted in the TCPR group, with 4 of 7 patients (57%) actually showing an increased reading and 3 of 7 patients (43%) showing a constant ETCO2 reading. The differences in the ETCO2 measurements between TCPR and HCPR groups were statistically significant. Both groups were similar with regards to call response intervals, patient ages, scene times, and initial ECG rhythms. One patient in the TCPR group was admitted to the hospital but later died, leaving no survivors in the study. TCPR appears to be superior to standard HCPR as measured by ETCO2 in maintaining cardiac output during ACLS resuscitation of out-of-hospital cardiac arrest patients.

Carbon Dioxide↗