Theoretically Optimal Duty Cycles for Chest and Abdominal Compression during External Cardiopulmonary Resuscitation

Objective: To use an electronic model of human circulation to compare the hemodynamic effects of different durations of chest compression during external CPR, both with and without interposed abdominal compression (IAC).
Methods: An electrical analog model of human circulation was studied on digital computer workstations using SPICE, a general-purpose circuit simulation program. In the model the heart and blood vessels were represented as resistive-capacitive networks, pressures as voltages, blood flow as electric current, blood inertia as inductance, and cardiac and venous valves as diodes. External pressurization of the heart and great vessels, as would occur in IAC-CPR, was simulated by the alternate application of damped rectangular voltage pulses, first between intrathoracic vascular capacitances and ground, and then between intra-abdominal vascular capacitances and ground. With this model compression frequencies of 60, 80, and 100 cycles/min and duty cycles ranging from 10% to 90%, both with and without IAC, were compared.
Results: There was little difference in hemodynamics when the overall compression frequency was varied between 60 and 100 cycles/min, but the effects of duty cycle were substantial. During both standard CPR and IAC-CPR, total flow and coronary flow were greatest at chest compression durations equal to 30% of cycle time. Interposed abdominal compression substantially improved simulated systemic blood flow and perfusion pressure at all duty cycles, compared with standard CPR without abdominal compression. Mean arterial pressure > 75 mm Hg and artificial cardiac output > 2.0 L/min could be generated by 30% duty cycle compression with IAC. Coronary perfusion in the model is clearly optimized at 30% chest compression (i.e., high-impulse chest compression technique).
Conclusion: Combined high-impulse chest compressions and IACs maximize blood flow during CPR in the electrical analog model of human circulation.     

Hemodynamics of Interposed Abdominal Compression during Human Cardiopulmonary Resuscitation

Objective: Clinical studies of interposed abdominal compression CPR (IAC-CPR) have had diverse outcomes. This study compared the hemodynamics of standard CPR and IAC-CPR in humans.
Methods: A 24-month prospective nonrandomized analysis of hemo-dynamic parameters was performed in a convenience cohort of 20 adults who had had out-of-hospital, nontraumatic, normothermic cardiac arrests. The study took place in the resuscitation unit of a large urban hospital. Thoracic aortic and right atrial catheters were inserted and pressures were recorded during standard CPR and IAC-CPR. Coronary perfusion pressures (CPPs) were determined during standard CPR and IAC-CPR. The patients were separated into two groups based upon their responses to IAC-CPR. Responders had increases in CPP during IAC-CPR; nonresponders had decreases or no change in CPP during IAC-CPR. Aortic relaxation, right atrial relaxation, aortic compression, and right atrial compression phase pressures were compared between the two groups.
Results: CPPs increased in 13 patients and decreased in seven patients. The mean change in CPP with IAC-CPR was an increase of 5.8 ± 15.1 torr. An elevated right atrial compression phase pressure (RaComp) during standard CPR was predictive of an increase in CPP during IAC-CPR (p = 0.047). In those patients who showed improvements in CPP during IAC-CPR, mean aortic relaxation phase pressures (AoRelax) increased by 9.5 ± 14.2 torr (p = 0.026) and mean right atrial relaxation phase pressures (RaRelax) decreased by 2.6 ± 6.2 torr (p = 0.099) during IAC-CPR.
Conclusions: The variable effects of IAC-CPR on CPP appear to be multifactorial. The improvement in CPP that occurred in responders to IAC-CPR was secondary to an increase in AoRelax as well as a decrease in RaRelax.     

Hemodynamics, Survival Benefits, and Complications of Interposed Abdominal Compression during Cardiopulmonary Resuscitation

Objective: To review and describe the hemodynamics and mechanism of benefit of interposed abdominal compression cardiopulmonary resuscitation (IAC-CPR) as well as the current complications and survival data withtheuseoflAC-CPR.
Methods: Critical review of selected, published English-language studies analyzing IAC-CPR. Overview of hemodynamic effects, complications, and survival data of IAC-CPR vs standard CPR.
Results: Several investigators have demonstrated improvements in coronary perfusion pressure, carotid and cerebral blood flows, and augmented venous return using IAC-CPR compared with standard CPR. Recently, IAC-CPR has been shown to improve survival from in-hospital cardiac arrest. To date, there has been no increase in complications seen with the use of abdominal compression during CPR.
Recommendations: IAC-CPR should be considered an adjunct to standard CPR for adult patients experiencing in-hospital cardiac arrest, after an adequate airway has been secured. More research is needed before IAC-CPR can be recommended for out-of-hospital cardiac arrest, for patients who have not been intubated, or for children.     

Chest Compression and Ventilation Rates during Cardiopulmonary Resuscitation: The Effects of Audible Tone Guidance

Objectives: To determine: 1) whether chest compressions during CPR are being performed according to American Heart Association (AHA) guidelines during cardiac arrest; and 2) the effect of an audio prompt to guide chest compressions on compliance with AHA guidelines and hemodynamic parameters associated with successful resuscitation. Methods: An observational clinical report and laboratory study was conducted. A research observer responded to a convenience sample of cardiac arrests within a 300-bed hospital and counted the rate of chest compressions and ventilations during CPR. To evaluate the effect of an audio prompt on CPR, health care providers performed chest compression without guidance using a porcine cardiac arrest model for 1 minute, followed by a second minute in which audio guidance was added. Chest compression rates, arterial and venous blood pressures, end-tidal CO₂ (ETCO₂) levels, and coronary perfusion pressures were measured and compared for the two periods. Results: Twelve in-hospital cardiac arrests were observed in the clinical part of the study. Only two of 12 patients had chest compressions performed within AHA guidelines. No patient had respirations performed within AHA guidelines. In the laboratory, 41 volunteers were tested, with 66% performing chest compressions outside the AHA standards for compression rate without audible tone guidance. With guided chest compressions, the mean (± SD) chest compression rate increased from 74 ± 22 to 100 ± 3/min (p < 0.01). End-tidal CO₂ levels increased from 15 ± 7 to 17 ± 7 torr (p < 0.01). Coronary perfusion pressure increased minimally with audible tone-guided chest compressions. Conclusions: The majority of Basic Cardiac Life Support-certified health care professionals did not perform CPR according to AHA-recommended guidelines. The use of audible tones to guide chest compression resulted in significantly higher chest compression rates and ETCO₂ levels.     

Who Gets Bystander Cardiopulmonary Resuscitation in a Witnessed Arrest?

Objective: To identify characteristics associated with provision of bystander CPR in witnessed out-of-hospital cardiac arrest cases.
Methods: An observational, prospective, cohort study was performed using cardiac arrest cases as identified by emergency medical services (EMS) agencies in Oakland County, MI, from July 1, 1989, to December 31, 1993. All patients who sustained a witnessed arrest prior to arrival of EMS personnel were reviewed.
Results: Of the 927 patients meeting entry criteria, the 229 patients receiving bystander CPR were younger: 60.9 ± 14.7 vs 67.9 ± 14.7 years (p < 0.01). Most (76.6%) cardiac arrests occurred in the home. In a multivariate logistic model, only the location of arrest outside the home was a significant predictor of receiving bystander CPR [odds ratio (OR) 3.8; 99% CI 2.5, 5.9]. Arrests outside the home were associated with significantly improved outcome, with 18.2% of out-of-home and 8.2% of in-home victims discharged from the hospital alive (OR 2.5; 99% CI 1.4, 4.4).
Conclusion: Patients who have had witnessed cardiac arrests outside the home are nearly 4 times more likely to receive bystander CPR, and are twice as likely to survive. This observation emphasizes the need for CPR training of family members in the authors' locale. This phenomenon may also represent a significant con-founder in studies of out-of-hospital cardiac arrest and resuscitation.     

Abdominal counterpulsation in cardiopulmonary resuscitation: animal models and theoretical considerations

Abdominal counterpulsation improves blood flow during otherwise standard CPR in animal models and in electronic models of the circulation. The method generates both central aortic and central venous pressure pulses. Success depends upon maximizing the former and minimizing the latter. Solution of a simple, first-order, differential equation may provide insight into proper technique. The equation suggests that the central arteriovenous pressure difference is maximized when pressure is applied directly over the abdominal aorta and when fluid loading is avoided. Proper technique may be critical in generating the largest possible arteriovenous pressure difference.     

Socioeconomic Status Is Associated with Provision of Bystander Cardiopulmonary Resuscitation

Objective. Although socioeconomic status (SES) has been linked to multiple health outcomes, there have been few studies of the effect of SES on the provision of bystander cardiopulmonary resuscitation (CPR) during cardiac arrest events and no studies that we know of on the effect of SES on the provision of dispatcher-assisted bystander CPR. This study sought to define the relationship between SES and the provision of bystander CPR in an emergency medical system that includes dispatcher-provided CPR instructions. Methods. This study was a retrospective, cohort analysis of cardiac arrests due to cardiac causes occurring in private residences in King County, Washington, from January 1, 1999, to December 31, 2005. We used the tax-assessed value of the location of the cardiac arrest as an estimate of the SES of potential bystanders as well as multiple measures from 2000 Census data (education, employment, median household income, and race/ethnicity). We also examined the effect of patient and system characteristics that may affect the provision of bystander CPR. Logistic regression models were used to analyze the association of these factors with two outcomes: the provision of bystander CPR with and without dispatcher assistance. Results. Forty-four percent (1,151/2,618) of cardiac arrest victims received bystander CPR. Four hundred fifty-seven people (17.5% of the entire study population, 39.7% of those who received any bystander CPR) received CPR without telephone instructions. A total of 694 people received dispatcher-assisted bystander CPR (25.6% of the entire population, 60.4% of those receiving any bystander CPR). After adjusting for demographic and care factors, we found a strong association between the tax-assessed value of the cardiac arrest location and increased odds of the provision of bystander CPR without dispatcher instructions and bystander CPR with dispatcher assistance compared with no bystander CPR. Conclusions. This study suggests that higher bystander SES is associated with increased rates of bystander CPR with and without dispatcher instructions. CPR training programs that target lower-SES communities and assessment of these training methods may be warranted.     

Real-Time Cardiopulmonary Resuscitation Feedback and Targeted Training Improve Chest Compression Performance in a Cohort of International Healthcare Providers

BackgroundOptimal cardiopulmonary resuscitation (CPR) performance is the foundation of successful cardiac arrest resuscitation. However, health care providers perform inadequate compressions. Better training techniques and real-time CPR feedback may improve compression performance.ObjectiveWe sought to evaluate the impact of a targeted training program combined with real-time defibrillator CPR feedback on chest compression performance in an international cohort of health care providers.MethodsPhysicians, nurses, respiratory therapists, and technicians from 6 hospitals in 5 countries (Taiwan, Singapore, China, Bahrain, and Kuwait) participated in a standardized resuscitation workshop. Chest compression was measured before and after didactics and activation of CPR feedback. Compressions were performed for 1 min on standard CPR manikins placed on a hospital bed and backboard and measured using ZOLL R Series defibrillators. The percentage of compressions meeting target values for depth and rate were compared before and after the workshop and activation of real-time CPR feedback. No depth maximum was defined to allow for mattress compression.ResultsChest compressions were more likely to meet targets for depth (71–95%, odds ratio [OR] 8.61 [95% confidence interval {CI} 4.42–16.77], p < 0.001), rate (41–81%, OR 6.4 [95% CI 4.2–9.8], p < 0.001), and both depth and rate (5–42%, OR 2.4 [95% CI 6.7–22.9], p < 0.001) after the workshop and activation of real-time CPR feedback.ConclusionsA targeted training intervention combined with real-time CPR feedback improved chest compression performance among health care providers from various countries.     

Predictive Factors of Successful Telephone-assisted Cardiopulmonary Resuscitation

Background

Our emergency medical service developed a telephone (phone)-assisted cardiopulmonary resuscitation (PACPR) procedure.

Objectives

To describe this procedure and study the factors modulating its implementation.

Methods

We conducted a single-center prospective study of telephone calls to our emergency medical communication center for cardiac arrest, for which PACPR was initiated.

Results

Thirty-eight patients were included in the study. In six cases, cardiopulmonary resuscitation (CPR) had been started before the call. When PACPR was initiated, CPR was performed until the rescue team arrived in 27 cases. One-third (n = 9) of the bystanders in these cases knew first-aid interventions, and all of these bystanders continued CPR until the rescue team arrived. The absence of a familial relationship between bystander and patient facilitated the continuation of CPR (100% vs. 37% with family ties, p = 0.01). CPR was continued more often if the bystander immediately agreed to PACPR than when he or she did not agree at first (88% vs. 45%, respectively, p = 0.01). When an obstacle to performing CPR was encountered, CPR was then performed in 57% of cases vs. 100% of cases with no obstacle (p = 0.003). These obstacles were associated with either the bystander (panic, apprehension, feelings of inadequacy, physical inability, indirect witness, tiredness) or the victim (morphotype, physical position). The presence of an obstacle, compared to no obstacle, associated with the bystander lowered the CPR performance rate (58% vs. 94%, respectively, p = 0.01). The presence of an obstacle, compared to no obstacle, associated with the victim also lowered CPR performance rate (50% vs. 85%, respectively, p = 0.04).

Conclusion

Our study demonstrates the feasibility of PACPR. The results may lead to a better understanding of facilitating factors and obstacles to telephone-assisted CPR, with the goal of improving its implementation. Good command of communication tools, identification of an appropriate bystander, and appropriate victim positioning are three fundamental factors of success.     

Abdominal Pumping

This article reviews the author's experience with a form of interposed abdominal compression cardiopulmonary resuscitation (IAC-CPR) in the United Kingdom. The development of the technique based upon animal resuscitation, including the use of phasic compression (abdominal pumping) for the resuscitation of rats from 30 minutes of cardiac arrest due to hypothermia, is reviewed. A simple technique for clinical use is described. The technique uses a hard-covered book or bean-shaped board applied to the abdomen below the umbilicus and compressed alternately with cardiac massage while respiration is assisted. Anecdotal clinical results suggest that further controlled clinical investigation is warranted.     

126例心跳骤停心肺复苏临床分析

目的：探讨急诊抢救心跳骤停的程序及方法，以便提高心肺复苏成功率。方法：回顾性分析126例在急诊抢救心跳骤停患者的临床资料，分析抢救程序及方法对心肺复苏的影响。结果：126例患者中31例复苏成功，63例复苏有效，32例复苏无效。结论：心肺复苏抢救成功与开始抢救时间、胸外按压方法、抢救药物及仪器的合理应用有密切关系。     

血管加压素联合肾上腺素抢救心脏骤停的临床观察

目的:研究血管加压素联合肾上腺素对心脏骤停的疗效。方法:64例呼吸心跳骤停患者随机分为肾上腺素组(对照组)和血管加压素联合肾上腺素组(治疗组)各32例,观察自主心律恢复时间、1h有效率、24h有效复苏成功率。结果:对照组、治疗组自主心律恢复时间分别为(20.5±4.5)min、(8.5±3.5)min、1h有效率分别为38%、72%;24h有效复苏成功率分别为13%、44%。治疗组的自主心律恢复时间明显短于对照组,1h有效率、24h有效复苏成功率明显高于对照组。结论:对心脏骤停患者,在标准心肺复苏(CPR)中,联合应用血管加压素和肾上腺素,可有效缩短自主心律恢复时间,提高1h有效率和24h有效复苏成功率。     

Gastric insufflation during IAC-CPR and standard CPR in a canine model

This study was undertaken to determine the effect of interposed abdominal compressions (IAC) during cardiopulmonary resuscitation (CPR) on gastric insufflation when the airway is not secured with an endotracheal tube. A canine model was used in which a common ventilation pressure was applied to separate cuffed esophageal and tracheal tubes. Gas entering the stomach was collected by a pre-placed gastrostomy tube leading to a bell spirometer. Gas entering the lungs was measured with a Wright Respirometer in series with the endotracheal tube. During standard CPR, measurable gastric gas volume was collected in 28 of 30 trials (mean 215 +/- 93 ml/ventilation). During IAC-CPR, in which abdominal pressure was maintained during ventilation after every 5th chest compression, measurable gastric gas was collected in 15 of 30 trials (mean 40 +/- 11 ml/ventilation). Interposed abdominal compressions as an adjunct to standard CPR may not only be of hemodynamic benefit, but may also reduce the incidence of gastric insufflation and attendant complications.     

Extracorporeal Resuscitation of Cardiac Arrest

OBJECTIVE: Extracorporeal support of heart and lung function (venoarterial perfusion) during cardiac arrest (ECPR) has been advocated as a means of improving survival following cardiac arrest. The authors retrospectively reviewed their institution's seven-year experience with this intervention. METHODS: Emergency department patients and inpatients in cardiac arrest or immediately postarrest were considered candidates. ECPR was instituted using venoarterial bypass and was continued until patients regained sufficient cardiopulmonary function to allow weaning from the device or until their condition was deemed irrecoverable. RESULTS: ECPR was attempted in 25 patients and successfully instituted in 21. Four patients (16%) were converted from ECPR to ventricular assist devices, two of whom survived and await transplantation. Seven additional patients were discharged from the hospital, resulting in an overall survival of 36%. Because none of the children treated survived, there was a trend toward higher age among survivors (survivors 40 +/- 14 yr, nonsurvivors 33 +/- 15 yr, p = 0.29). The duration of conventional CPR was shorter among survivors (survivors 21 +/- 16 min, nonsurvivors 43 +/- 32 min, p = 0.04), as was the duration of extracorporeal support (survivors 44 +/- 21 hr, nonsurvivors 87 +/- 96 hr, p = 0.18). Survival was seen only in patients whose conditions were amenable to a definitive therapeutic intervention, particularly cardiac arrest due to respiratory or pulmonary embolic disease. While four of the five patients treated in the ED were successfully supported, none survived to discharge. CONCLUSION: In select patients with reversible disease, extracorporeal CPR can be used to successfully treat cardiac arrest. Further investigation into its most appropriate application is warranted.     

人工通气在早期心肺复苏中价值的探讨

目的:评价早期心肺复苏(CPR)中A(气道)、B(呼吸)、C(循环)抢救步骤的价值。方法:收集132例心跳、呼吸骤停行CPR患者的临床资料,对43例复苏成功病例,按原发疾病进行分类统计以及实施心肺复苏所采取C、CAB及ABC的步骤,比较各组的成功率。结果:心源性疾患所引起心跳、呼吸骤停C组复苏成功率为50.0％明显高于其他各组(P<0.05)。C组与ABC组比较复苏成功率有显著性差异(P<0.05)。结论:C及CAB是各种原因引起的心跳、呼吸骤停患者CPR中有效的抢救步骤。