A new device producing manual sternal compression with thoracic constraint for cardiopulmonary resuscitation

OBJECTIVE: Blood flow during conventional cardiopulmonary resuscitation (CPR) is usually less than adequate to sustain vital organ perfusion. A new chest compression device (LifeBelt) which compresses both the sternum and the lateral thoraces (compression and thoracic constraint) has been developed. The device is light weight, portable, manually powered and mechanically advantaged to minimize user fatigue. The purpose of this study was to evaluate the mechanism of blood flow with the device, determine the optimal compression force and compare the device to standard manual CPR in a swine arrest model. METHODS: Following anesthesia and instrumentation, intravascular contrast injections were performed in four animals and the performance characteristics of the device were evaluated in eight animals. In a comparative outcome study, 42 anesthetized and instrumented swine were randomized to receive LifeBelt or manual CPR. Ventricular fibrillation (VF) was induced electrically and was untreated for 7.5 min. After 7.5 min, countershocks were administered and chest compressions initiated. Pulseless electrical activity (PEA) was observed after one to three shocks in all animals. CPR was continued until restoration of spontaneous circulation (ROSC) or for 10 min after the first shock. If ROSC had not occurred within 5 min of beginning CPR, 0.01 mg/kg of epinephrine (adrenaline) was administered. During CPR, peak systolic aortic pressure (Ao), diastolic coronary perfusion pressure (CPP-diastolic aortic minus diastolic right pressure) and end-tidal CO(2) were measured. RESULTS: Angiographic studies demonstrated cardiac compression as the mechanism of blood flow. Optimal performance, determined by coronary perfusion pressure, was observed at a sternal force of 100-130 lb (45-59 kg). In the comparative trial, significant differences in the measured CPP were observed between LifeBelt and manual CPR both at 1 min (15+/-8 mmHg versus 10+/-6 mmHg, p<0.05) and 5 min (17+/-4 mmHg versus 13+/-7 mmHg, p<0.02) of chest compression. A greater (p<0.05) ETCO(2), a marker of cardiac output and systemic perfusion, was observed with LifeBelt CPR (20+/-7 mmHg) than with manual CPR (15+/-5 mmHg) at 1 min. Peak Ao pressures were not different between methods. With the device, 86% of animals were resuscitated compared to 76% in the manual group. CONCLUSIONS: Blood flow with the LifeBelt device is primarily the result of cardiac compression. At a sternal force of 100-130 lb (45-59 kg), the device produces greater CPP than well-performed manual CPR during resuscitation from prolonged VF.     

Ethyl pyruvate enhances intra-resuscitation hemodynamics in prolonged ventricular fibrillation arrest

Aims

As the duration of untreated cardiac arrest increases, the effectiveness of standard therapies declines, and may be more harmful than helpful. We investigated the hemodynamic, metabolic and anti-inflammatory effects of Ringer's ethyl pyruvate solution (REPS) versus Ringer's solution (RS) in the acute model of prolonged porcine arrest.

Methods

Seventeen mixed-breed swine were induced into ventricular fibrillation (VF) and left untreated for 8 min. CPR was begun using a mechanical chest compression device at a rate of 100 per minute. At the onset of CPR, animals were randomly assigned to treatment with either 25 mL/kg of RS or 25 mL/kg of REPS containing 40 mg/kg of ethyl pyruvate, infused over 5 min in blinded fashion. CPR continued with administration of a drug cocktail at 2 min and the first rescue shock was delivered at minute 13 of VF. Animals having ROSC were supported with standardized care for 2 h.

Results

Both groups had 100% ROSC and 100% 2-h survival. The REPS group exhibited higher median CPP (27.3 mmHg) than the control group (16.5 mmHg) by 3 min of CPR, which continued throughout the duration of CPR (p = 0.02). The median time to hypotension following ROSC was 9.64 min in the REPS group and 7.25 min in controls (p = 0.04) and there was a non-significant trend of decreased use of vasopressors for the duration of resuscitation. There was no difference in systemic or cerebral metabolism between groups. There were non-significant trends of decreased IL-6, increased Il-10 and decreased mesenteric bacterial colony growth in those treated with REPS when compared to RS.

Conclusions

The administration of REPS with CPR significantly improved intra- and post-resuscitation hemodynamics in this swine model of prolonged cardiac arrest, but did not definitely change the metabolic or inflammatory profile during the acute resuscitation period.     

腹部提压法对窒息性心搏骤停猪复苏效果的实验研究

目的 比较胸外按压心肺复苏(CC-CPR)与腹部提压心肺复苏(ALC-CPR)对窒息性心搏骤停猪复苏时血流动力学指标和呼吸指标的影响,初步评价腹部提压法对窒息性心搏骤停猪的复苏效果.方法 健康家猪30只,按随机数字表法分为两组,每组15只.建立窒息性心搏骤停模型,分别实施CC-CPR和ALC-CPR.窒息前10 min开始连续记录心电图(ECG)、脉搏血氧饱和度(SpO2)、呼气末二氧化碳分压(PEICO2)、主动脉收缩压(SBP)、舒张压(DBP)、中心静脉压(CVP)和潮气量(VT)直至实验结束;计算主动脉平均动脉压(MAP)、冠状动脉灌注压(CPP)和分钟通气量(MV);分别在窒息前10 min、窒息后10 min及复苏后5、10、20 min抽取动脉血查血气.观察两组动物的自主循环恢复(ROSC)率、24 h存活率和24 h后神经功能缺损评分.结果 两组窒息前10 min和窒息后10 min各项指标均无明显差异.复苏后2min,CC-CPR组MAP( mm Hg,1 mm Hg=0.133 kPa)和CPP(mm Hg)高于ALC-CPR组(MAP:43.60±12.91比33.40±6.59,P＜0.05;CPP:21.67±11.28比11.80±4.16,P＜0.01);ALC-CPR组VT(ml)和MV( L/min)高于CC-CPR组(VT:111.67±18.12比56.60±7.76; MV:11.17±1.81比5.54±0.79,均P＜0.01).在复苏后5、10、20 min,ALC-CPR组pH值、动脉血氧分压(PaO2,mm Hg)和动脉血氧饱和度(SaO2)均升高,HCO3-(mmol/L)、剩余碱(BE,mmol/L)均降低,且均高于CC-CPR组(复苏20 min时pH值:7.16±0.16比7.01±0.14; PaO2:82.73±13.20比58.33±17.77;HCO3-:27.71±3.11比21.04±3.62; BE:-4.78±4.30比-10.23±2.12;SaO2:0.893±0.088比0.764±0.122),动脉血二氧化碳分压(PaCO2,mm Hg)、K+(mmol/L)和乳酸(Lac,mmol/L)均明显低于CC-CPR组(复苏20 min时PaCO2:49.40±15.60比79.80±15.35;K+:7.18±1.76比8.55±1.02;Lac:8.17±1.46比10.39±1.92),差异均有统计学意义(P＜0.05或P＜0.01).ALC-CPR组ROSC率、24 h存活率明显高于CC-CPR组(ROSC率:80.0％比26.7％,P＜0.01;24h存活率:60.0％比13.3％,P＜0.05),24 h神经功能评分(分)低于CC-CPR组(1.11±0.33比3.50±0.70,P＜0.01).结论 在窒息性心搏骤停猪的复苏早期,ALC-CPR较CC-CPR更具优势.     

Conceptual models of coronary perfusion pressure and their relationship to defibrillation success in a porcine model of prolonged out-of-hospital cardiac arrest

Introduction

The amount of myocardial perfusion required for successful defibrillation after cardiac arrest is unknown. Coronary perfusion pressure (CPP) is a surrogate for myocardial perfusion. One limited clinical study identifies a threshold of 15 mmHg required for return of spontaneous circulation (ROSC). Our exploration of threshold and dose models of CPP during the initial bout of CPR indicates higher levels than previously demonstrated are required. CPP required for shock success throughout on-going resuscitation is unknown and other conceptual models of CPP have not been explored.

Hypothesis

An array of conceptual models of CPP is associated with and predicts defibrillation success throughout resuscitation.

Methods

Data from 6 porcine cardiac arrest studies were pooled. Mean and area under the curve (AUC) CPP were derived for 30-s epochs. Five conceptual models of CPP were analyzed: threshold, delta, cumulative delta, dose, and cumulative dose. Comparative statistics were performed with one-way ANOVA and two-tailed t-test. Regression models assessed CPP trends and prediction of ROSC.

Results

For 316 defibrillation attempts in 124 animals, those resulting in ROSC (n = 75) had significantly higher threshold, delta, cumulative delta, dose, and cumulative dose CPP than those without. All conceptual models except delta CPP had significantly different values across successive defibrillation attempts and all five models were significant predictors of ROSC, along with experimental design.

Conclusions

Threshold, delta, cumulative delta, dose, and cumulative dose CPP predict individual defibrillation success throughout resuscitation.     

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.     

Augmentation of tissue perfusion by a novel compression device increases neurologically intact survival in a porcine model of prolonged cardiac arrest

OBJECTIVE: This study was performed to determine the potential efficacy of an automated device with a load-distributing band (AutoPulse, Revivant Corporation), in improving neurologically intact survival after cardiac arrest. DESIGN: Randomized, controlled trial. SETTING: University animal laboratory. SUBJECTS: Forty-four swine (18-23 kg). INTERVENTIONS: Eight minutes after induction of untreated ventricular fibrillation, pigs were randomized to AutoPulse-CPR (A-CPR, n = 22), conventional cardiopulmonary resuscitation (CPR) with 20% anterior-posterior chest displacement (C-CPR20, n = 10) or 30% chest displacement (C-CPR30, n = 12), followed by resuscitation protocol with ventilation, defibrillation and intravenous epinephrine (adrenaline). MEASUREMENTS AND MAIN RESULTS: Aortic and right atrium blood pressure was measured with micromanometers. Regional blood flows were measured with microspheres. Coronary perfusion pressure during A-CPR was significantly higher as compared to C-CPR without epinephrine (A-CPR versus C-CPR20 versus C-CPR30; 16 +/- 1 mmHg versus 7 +/- 2 mmHg versus 11 +/- 2 mmHg, p < 0.05). A-CPR improved both myocardial flow without epinephrine (A-CPR versus C-CPR20 versus C-CPR30; 23% versus 0% versus 4%; percent of baseline, p < 0.05) and cerebral blood flow (40% versus 4% versus 19%, percent of baseline, p < 0.05). Sixteen of 22 animals receiving A-CPR regained spontaneous circulation and survived; 14/22 had normal cerebral performance (CPC 1). Four of 12 animals receiving C-CPR30 regained spontaneous circulation and survived, but only one animal had normal neurological function (14/22 versus 1/12, p < 0.0001). No animal receiving C-CPR20 achieved spontaneous circulation. At necropsy, 67% of C-CPR30 had rib fracture and 33% showed lung injury, while A-CPR and C-CPR20 resulted in no detectable injuries. CONCLUSIONS: Improved hemodynamics with AutoPulse performed CPR results in improved neurologically intact survival without subsequent thoracic or pulmonary injuries in this porcine model of prolonged cardiac arrest.     

Correlation between coronary perfusion pressure and quantitative ECG waveform measures during resuscitation of prolonged ventricular fibrillation

Introduction

The ventricular fibrillation (VF) waveform is dynamic and predicts defibrillation success. Quantitative waveform measures (QWMs) quantify these changes. Coronary perfusion pressure (CPP), a surrogate for myocardial perfusion, also predicts defibrillation success. The relationship between QWM and CPP has been preliminarily explored. We sought to further delineate this relationship in our porcine model and to determine if it is different between animals with/without ROSC (return of spontaneous circulation).

Hypothesis

A relationship exists between QWM and CPP that is different between animals with/without ROSC.

Methods

Utilizing a prior experiment in our porcine model of prolonged out-of-hospital VF cardiac arrest, we calculated mean CPP, cumulative dose CPP, and percent recovery of three QWM during resuscitation before the first defibrillation: amplitude spectrum area (AMSA), median slope (MS), and logarithm of the absolute correlations (LAC). A random effects linear regression model with an interaction term CPP*ROSC investigated the association between CPP and percent recovery QWM and how this relationship changes with/without ROSC.

Results

For 12 animals, CPP and QWM measures (except LAC) improved during resuscitation. A linear relationship existed between CPP and percent recovery AMSA (coefficient 0.27; 95%CI 0.23, 0.31; p < 0.001) and percent recovery MS (coefficient 0.80; 95%CI 0.70, 0.90; p < 0.001). A linear relationship existed between cumulative dose CPP and percent recovery AMSA (coefficient 2.29; 95%CI 2.0, 2.56; p < 0.001) and percent recovery MS (coefficient 6.68; 95%CI 6.09, 7.26; p < 0.001). Animals with ROSC had a significantly “steeper” dose–response relationship.

Conclusions

There is a linear relationship between QWM and CPP during chest compressions in our porcine cardiac arrest model that is different between animals with/without ROSC.     

叹息样呼吸与猪心肺复苏过程中血流动力学变化的研究

目的 研究CPR的病理生理过程,探讨叹息样呼吸对CPR过程中血流动力学的影响.方法 12头北京长白猪,体质量(30±1)kg,麻醉后气管插管,机械通气,连续记录实时呼吸参数.股动脉置管测量主动脉压(AOP),并抽取动脉血;肺动脉漂浮导管置测最右心房压(RAP)及心输出量(CO).以程控电刺激制作室颤(VF)模型.VF4 min后进行标准30:2 CPR 12 min,记录相关参数.结果 CPR过程中pH,PaCO2及乳酸逐渐升高,而PaO2逐渐降低,但PaO2在整个实验过程中均大于50mmHg.10只动物出现叹息样呼吸,但随时间推移逐渐减弱;未出现叹息样乎吸的2只动物均未复苏成功.标准心外按压在多数动物均可产生大干死腔量(VD)的被动通气,但其潮气量随时间推移逐渐减少.因此人工通气在总分钟通气量中所占比例逐渐增加.CO、冠脉灌注压(CPP)与叹息样呼吸分钟通气量(MVg)呈正相关(r分别等于0.736,0.721,P＜0.01);RAP与MVg呈负相关(r=-0.744,P＜0.01).结论 标准CPR能够维持机体12min的氧合;心外按压能够产生大于VD的被动通气;叹息样呼吸可以通过增加CO、CPP及降低RAP产生对自主循环的恢复产生有益的生理作用.

Abstract：

Objective Gasp was defined as a pathology respiration during cardiac arrest. This study was to investigate its effect on hemodynamics during CPR. Method Twelve domestic pigs, weighening (30 ± 1) kg,were anaesthetized. After tracheal intubation and mechanical ventilation, continuous respiratory variables were recorded. An artery catheter was inserted for reference blood samples and measuring aortic artery pressure (AOP).Right atrial pressure (RAP) and cardiac output (CO) were detected by Swan-Ganz catheter. Ventricular fibrillation (VF) was induced by programmed electrical stimulation instruments. After 4 minutes untreated VF, standard 30:2 CPR was done for 12 minutes and the parameters were recorded. Results pH, PaCO2 and lactic acid increased and PaO2 decreased progressively during CPR, whereas PaO2 was up to 50mmHg during the whole protocol. Gasps were observed in 10 animals, but weaken gradually; the left 2 animals with no gasp did not restore of spontaneous circulation (ROSC). Standard CPR could produce passive ventilation more than dead space (VD), but its tidal volume decreased gradually, which led to the percentage of rescue ventilation increased progressively. Positive correlations were found between CO, coronary perfusion pressure (CPP) and minute ventilation of gasps (MVg) (r was 0.736 and 0.721 respectively, both P ＜0.01); negative correlation were found between RAP and MVg (r= -0. 744, P ＜ 0.01). Conclusions Standard CPR could maintain 12 minutes oxygenation of body; compressions could produce enough passive ventilation more than VD; gasps were benefit to ROSC by increasing CO, CPP and decreasing RAP.     

长时程室颤先行心肺复苏对复苏效果的影响及机制研究

目的 比较7 min室颤先行心肺复苏2 min后除颤与直接除颤的复苏效果,并探讨其机制.方法 建立猪闭胸电诱发室颤模型,CPR First组优先心肺复苏2 min后连续三次除颤,Shock First组直接予连续三次除颤,观察冠脉灌注压、室颤波频率和振幅变化,计算除颤成功率和自主循环恢复率.结果 CPR First组先行心肺复苏2 min后可提高初次除颤前的冠脉灌注压、室颤波的频率和振幅, CPR First组比Shock First组有高的除颤成功率和自主循环恢复率(P＜0.05).结论 7 min室颤除颤前先行胸外按压和人工呼吸可明显提高复苏成功率,其机制与增加冠脉灌注,改善心脏能量储备,提高室颤波的频率和振幅有关.     

短时程复合亚低温改善长时间室颤家猪复苏预后的研究

目的 比较短时程亚低温对长时间室颤家猪短期复苏预后的影响.方法 采取体质量34～ 36 kg左右健康雄性种猪14头,通过右心室致颤电极诱发室颤并维持11 min,之后采取人工胸外按压及球囊面罩通气,按压通气比为30:2,每2 min轮换操作者.复苏6 min后给予120 J双向波除颤,若未能获得自主循环恢复(return of spontaneous circulation,ROSC),继续给予心肺复苏及必要时电除颤.连续复苏12 min仍无ROSC认为复苏失败.对ROSC家猪,随机(随机数字法)分为常温组(normothermia group,NT)及复合降温组(combined hypothermia group,CH).CH组立即给予4℃生理盐水静脉输注并联合体表物理降温,在120 min内将核心体温降至32 ～ 34℃并维持2h后主动复温,2h将体温升至基础体温水平.记录两组家猪致颤前基础状态下血流动力学、血气及乳酸.记录ROSC后心输出量、心率、核心体温变化.每24h评估动物神经功能直至观察终点.组间比较采用Fisher检验或方差分析,以P＜0.05为差异有统计学意义.结果 两组动物基础状态下体质量、平均动脉压、心输出量、Ph、呼气末二氧化碳水平、血乳酸水平差异均无统计学意义(P＞0.05).在复苏过程中,两组动物在总复苏时间、首次除颤成功率、ROSC比例、首次除颤ROSC比例、总除颤次数及肾上腺素用量差异均无统计学意义(P＞0.05).存活时间上,CH组明显长于NT组[(96.00±0.00) h vs.(49.71 ±43.65)h,P=0.031],同时NT组96 h生存率亦高于NT组,差异有统计学意义(P＜0.05).神经功能方面,CH组在复苏后96 h内各时间段均优于NT组,差异有统计学意义(P＜0.05).结论 即使2h短时程的亚低温,也可以明显改善11 min室颤家猪的短期复苏预后.     

Discriminating the effect of accelerated compression from accelerated decompression during high-impulse CPR in a porcine model of cardiac arrest

Aim of the study

Piston based mechanical chest compression devices deliver compressions and decompressions in an accelerated pattern, resulting in superior haemodynamics compared to manual compression in animal studies. The present animal study compares haemodynamics during two different hybrid compression patterns to a standard compression pattern resembling that of modern mechanical chest compression devices.

Method

In 12 anaesthetized domestic pigs in ventricular fibrillation, coronary perfusion pressures (CPP) and cerebral cortical blood flow (CCBF) was measured, and transesophageal echocardiography (TEE) was performed. Two hybrid compression patterns, one with accelerated trapezoid compression and slower sinusoid decompression (TrS), and one with slower sinusoid compression and accelerated trapezoid decompression (STr), were tested against a standard accelerated trapezoid compression-decompression pattern (TrTr) in a cross-over randomised setup.

Results

There were 7% (1, 14, p = 0.046) lower CCBF and 3 mmHg (1, 5, p = 0.017) lower CPP with the TrS compared to TrTr pattern. No significant difference between STr and TrTr pattern in either CCBF, 6% (−3, 15, p = 0.176) or CPP, 0 mmHg (−2, 3, p = 0.703) was present. Our TEE recordings were insufficient for haemodynamic comparison between the different compression-decompression patterns. Despite standardized sternal piston position and placement of the pigs, TEE revealed varying degree of asymmetrical heart chamber compression in the animals.

Conclusion

Both cardiac and cerebral perfusion benefited from accelerated decompression, while accelerated compression did not improve haemodynamics. The evolution of mechanical CPR is dependent on further research on mechanisms generating forward blood flow during external chest compressions.     

Miniaturized mechanical chest compressor improves calculated cerebral perfusion pressure without compromising intracranial pressure during cardiopulmonary resuscitation in a porcine model of cardiac arrest

Objective

One of the major goals of cardiopulmonary resuscitation (CPR) is to provide adequate oxygen delivery to the brain for minimizing cerebral injury resulted from cardiac arrest. The optimal chest compression during CPR should effectively improve brain perfusion without compromising intracranial pressure (ICP). Our previous study has demonstrated that the miniaturized mechanical chest compressor improved hemodynamic efficacy and the success of CPR. In the present study, we investigated the effects of the miniaturized chest compressor (MCC) on calculated cerebral perfusion pressure (CerPP) and ICP.

Methods

Ventricular fibrillation was electrically induced and untreated for 7 min in 13 male domestic pigs weighing 39 ± 3 kg. The animals were randomized to receive mechanical chest compression with the MCC (n = 7), or the Thumper device (n = 6). CPR was performed for 5 min before defibrillation attempt by a single 150 J shock. At 2.5 min of CPR, the epinephrine at a dose of 20 μg/kg was administered. Additional epinephrine was administered at an interval of 3 min thereafter. If resuscitation was not successful, CPR was resumed for an additional 2 min prior to the next defibrillation until successful resuscitation or for a total of 15 min. Post-resuscitated animals were observed for 2 h.

Results

Significantly greater intrathoracic positive and negative pressures during compression and decompression phases of CPR were observed with the MCC when compared with the Thumper device. The MCC produced significantly greater coronary perfusion pressure and end-tidal carbon dioxide. There were no statistically significant differences in systolic and mean ICP between the two groups; however, both of the measurements were slightly greater in the MCC treated animals. Interestingly, the diastolic ICP was significantly lower in the MCC group, which was closely related to the significantly lower negative intrathoracic pressure in the animals that received the MCC. Most important, systolic, diastolic and mean calculated CerPP were all significantly greater in the animals receiving the MCC.

Conclusions

In the present study, mechanical chest compression with the MCC significantly improved calculated CerPP but did not compromise ICP during CPR. It may provide a safe and effective chest compression during CPR.Protocol number: P1205.     

The need to resume chest compressions immediately after defibrillation attempts: An analysis of post-shock rhythms and duration of pulselessness following out-of-hospital cardiac arrest

AimCurrent consensus guidelines for cardiopulmonary resuscitation (CPR) recommend that chest compressions resume immediately after defibrillation attempts and that rhythm and pulse checks be deferred until completion of 5 compression:ventilation cycles or minimally for 2 min. However, data specifically confirming the post-shock duration of asystole or pulseless electrical activity before return of spontaneous circulation (ROSC) are lacking. Our aim was to describe the frequency of the various post-shock cardiac rhythms and the duration of post-shock pulselessness in out-of-hospital non-traumatic cardiac arrest.MethodUsing prospectively-collected data from the Resuscitation Outcomes Consortium (ROC) Epistry database, the investigators reviewed monitor-defibrillator recordings of 176 patients who received defibrillation attempts in the out-of-hospital setting for ventricular fibrillation (VF) or ventricular tachycardia (VT) with absent pulses,.ResultsAmong 376 different defibrillation attempts delivered in the 176 patients, there were 182 resulting episodes of post-shock asystole. The mean interval of asystole after defibrillation was 69 ± 136 s (median 20 s; IQR 36) and the mean interval for return of an organized rhythm was 64 ± 157 s (median 7 s; IQR 26). The mean time to ROSC was 280 ± 320 s (median 136 s; IQR 445).ConclusionAfter defibrillation attempts, the majority of patients remain pulseless for over 2 min and the duration of asystole before return of pulses is longer than 120 s beyond the shock gap in as many as 25%. These data support the recommendation to immediately resume chest compressions for 2 min following attempted defibrillation.     

Different roles of nitric oxide synthase isoforms in cardiopulmonary resuscitation in pigs

The purpose of the present study was to identify the roles of the three nitric oxide synthase (NOS) isoforms on whole body ischemia-reperfusion injury during cardiopulmonary resuscitation (CPR) with periodic acceleration (pGz) in pigs. Thirty-two anesthetized pigs (27.6+/-3.4 kg) were monitored for hemodynamics and selected echocardiographic variables. Twenty minutes after NOS inhibition or placebo administration, ventricular fibrillation (VF) was induced and remained untreated for 3 min, followed by CPR with pGz for 15 min, plus 3 min of manual chest compressions and defibrillation attempt. Four groups were studied: (1) saline control; (2) L-NAME (non-selective NOS inhibitor); (3) aminoguanidine (inducible NOS inhibitor); (4) TRIM (neuronal NOS inhibitor). Return of spontaneous circulation (ROSC) to 180 min occurred in 6/8 controls, 4/8 L-NAME, 7/8 aminoguanidine, and 2/8 TRIM animals. The L-NAME group had significantly lower organ blood flow, impaired cardiac function, but higher vascular tone than control group. The aminoguanidine group had the highest organ blood flows and survival rate. Six out of eight TRIM treated animals had initial return of heartbeat; however, with impaired heart contractility and could not survive more than 20 min of ROSC. This study reveals the differential role of endogenous NO produced from the three NOS isoforms during pGz-CPR. Both endothelial and neuronal NOS derived NO show predominantly protective effects while inducible NOS derived NO plays a detrimental role in pGz-CPR. The present study has shown that cardiac arrest and resuscitation appears to be associated with a different expression of NOS isoforms which appear to affect resuscitation outcomes differently.     

Effect and mechanism of esmolol given during cardiopulmonary resuscitation in a porcine ventricular fibrillation model

Objectives

The aim of the study was to investigate the effect on calcium cycling protein and electrical restitution of β₁-adrenergic receptor antagonist esmolol administered during cardiopulmonary resuscitation in the porcine ventricular fibrillation model.

Methods

Ventricular fibrillation untreated for four minutes was induced by dynamic steady state pacing protocol in 40 healthy male pigs, in which local unipolar electrograms were recorded using one 10-electrode catheter that was sutured to the left ventricular epicardium. During CPR, animals were randomized into two groups to receive saline as placebo or esmolol after two standard doses of epinephrine. At post-resuscitation 2-h, six pigs were randomly selected from each group and the second VF induction was performed. Local activation-recovery intervals (ARI) restitutions and the VF inducibility between control group and esmolol group were compared. Western blotting was performed to determine expression of Ca²⁺/calmodulin-dependent protein kinase IIδ(CaMKIIδ) and cardiac ryanodine receptor (RyR2) protein, and their phosphorylation status.

Results

Injection of esmolol combined with epinephrine during CPR significantly decreased recurrent rate of ventricular fibrillation during 2-h post-resuscitation, meanwhile it has no adverse affect on the restore of spontaneous circulation. Esmolol significantly flattened ARI restitution slope, lessened regional difference of ARI restitution, decreased the VF inducibility, and alleviated CaMKIIδ hyper-activation and RyR2 hyper-phosphorylation.

Conclusions

Esmolol given during CPR has significant effects on modulating electrical restitution property and intracellular calcium handling, which contributes the most important reasons why β₁-blockade significantly reduced the onset and maintenance of VF.     

Chest compression quality variables influencing the temporal development of ROSC-predictors calculated from the ECG during VF

Background

Predictive measures that reflect the probability of return of spontaneous circulation (ROSC) if the patient is defibrillated can be calculated from the electrocardiogram during ventricular fibrillation (VF) and ventricular tachycardia (VT). It has not been studied how the quality of chest compressions affect the development of such ROSC predictors.

Materials and methods

We have formulated a model for the effect of chest compressions on the ROSC predictor median-slope (MS). For untreated VF/VT MS is assumed to decay with time and increases in MS are attributed to the effect of chest compressions. The model correlates observed trends in MS with compression quality variables derived from measurements of compression depth and force recorded during out-of-hospital cardiac arrest. Among the quality variables tested were compression rate, depth, duty cycle, leaning depth, force, work and a novel quality indicator termed residual heart force. The model was first developed on an exploration dataset and thereafter validated against independent data.

Results

When testing the indicators one by one, residual heart force (p < 0.0001), force (p < 0.0001) and work (p = 0.0210) were significantly correlated to MS development. In multivariate analysis, residual heart force (p < 0.0001) was the most significant indicator. Adjusting for residual heart force, there was a tendency that increased depth was associated with smaller effect of compressions (p = 0.0330).

Conclusion

Using MS as an indicator of the state of the myocardium, force-based compression quality variables are better indicators of efficient CPR than compression depth. A novel indicator termed residual heart force gives the best correlation with observed trends in MS.     

Effects of sustained abdominal aorta compression on coronary perfusion pressures and restoration of spontaneous circulation during cardiopulmonary resuscitation in swine

Objectives

The present study was undertaken to explore whether sustained abdominal aorta compression-cardiopulmonary resuscitation (SAAC-CPR), as a means, can raise coronary perfusion pressure (CPP) as well as restoration of spontaneous circulation (ROSC) during CPR. In the present study, we hypothesised that SAAC-CPR elevates CPP during CPR and improves ROSC, without causing liver laceration.

Methods

Animals were randomised into one of two groups (Standard CPR and SAAC-CPR). Ten domestic swine (22-25 kg) were anaesthetised, intubated and mechanically ventilated. Ventricular fibrillation was induced, and after 3 min of untreated ventricular fibrillation, the animals were treated with standard CPR (with simplex chest compression (SCC) and epinephrine) or SAAC-CPR (SCC with sustained abdominal aorta compression, without epinephrine). CPP and ROSC were compared.

Results

SCC with sustained abdominal aorta compression (SCC + SAAC) significantly increased CPP in comparison with SCC during CPR (p < 0.05). The increase in CPP with SCC + SAAC is equivalent to that achieved with epinephrine (p > 0.05). All animals in the standard CPR and SAAC-CPR groups restored spontaneous circulation. No liver damage was found in post-mortem examinations of the swine subjects.

Conclusions

During CPR, non-invasive SAAC can rapidly and reversibly raise the CPP as much as can epinephrine and is especially suitable for out-of-hospital CPR.     

心肺复苏中自主循环恢复预测及识别方法研究进展

心肺复苏(cardiopulmonary resuscitation,CPR)是心搏骤停时最常用的抢救方法.2010年CPR指南强调高质量胸外按压,建议除颤后继续按压2 min后再判断循环以减少按压中断时间.然而,临床中自主循环恢复(return of spontaneous circulation,ROSC)多发生在按压过程中,此时持续按压不利于自主循环稳定.因此在CPR中识别ROSC十分重要.目前临床上可用于CPR中ROSC的预测和识别方法包括:触及脉搏搏动、波幅谱面积、呼气末二氧化碳分压、冠脉灌注压、中心静脉氧饱和度、胸外按压分数、局部脑氧饱和度、光学容积描记图、结膜氧张力、经胸阻抗容积描记术及超声心动图.本文对以上CPR过程中ROSC预测及识别方法做一综述.