Hemodynamics in humans during conventional and experimental methods of cardiopulmonary resuscitation

Lung tissue injury and hemodynamic effects of ventilations synchronized or unsynchronized to continuous chest compressions in a porcine cardiac arrest model

Aim

Compare lung injury and hemodynamic effects in synchronized ventilations (between two chest compressions) vs. unsynchronized ventilations during cardiopulmonary resuscitation (CPR) in a porcine model of cardiac arrest.

Methods

Twenty pigs were randomized to either synchronized or unsynchronized group. Ventricular fibrillation was induced electrically and left for 1.5 minutes. Four minutes of basic chest compression:ventilation (30:2) CPR was followed by eight minutes of either synchronized or unsynchronized ventilations (10/min) during continuous compressions before defibrillation was attempted. Aortic, right atrial and intracerebral pressures, carotid and cerebral blood flow and cardiac output were measured. Airway monitoring included capnography and respiratory function monitor. Macro- and microscopic lung injuries were assessed post-mortem.

Results

There were no significant differences between groups in any of the measured hemodynamic variables or inspiration time (0.4 vs. 1.0 s, p = 0.05). The synchronized ventilation group had lower median peak inspiratory airway pressure (57 vs. 94 cm H2O, p < 0.001), lower minute ventilation (3.7 vs. 9.4 l min-1, p < 0.001), lower pH (7.31 vs. 7.53, p < 0.001), higher pCO2 (5.2 vs. 2.5 kPa, p < 0.001) and lower pO2 (31.6 vs. 54.7 kPa, p < 0.001) compared to the unsynchronized group after 12 minutes of CPR. There was significant lung injury after CPR in both synchronized and unsynchronized groups.

Conclusion

Synchronized and unsynchronized ventilations resulted in similar hemodynamics and lung injury during continuous mechanical compressions of pigs in cardiac arrest. Animals that received unsynchronized ventilations with one second inspiration time at a rate of ten ventilations per minute were hyperventilated and hyperoxygenated.Institutional protocol number: FOTS, id 6948.

The association of arterial blood pressure waveform-derived area duty cycle with intra-arrest hemodynamics and cardiac arrest outcomes

AIM

Develop a novel, physiology-based measurement of duty cycle (Arterial Blood Pressure-Area Duty Cycle [ABP-ADC]) and evaluate the association of ABP-ADC with intra-arrest hemodynamics and patient outcomes.

METHODS

This was a secondary retrospective study of prospectively collected data from the ICU-RESUS trial (NCT02837497). Invasive arterial waveform data were used to derive ABP-ADC. The primary exposure was ABP-ADC group (<30%; 30-35%; >35%). The primary outcome was systolic blood pressure (sBP). Secondary outcomes included intra-arrest physiologic goals, CPR quality targets, and patient outcomes. In an exploratory analysis, adjusted splines and receiver operating characteristic (ROC) curves were used to determine an optimal ABP-ADC associated with improved hemodynamics and outcomes using a multivariable model.

RESULTS

Of 1129 CPR events, 273 had evaluable arterial waveform data. Mean age is 2.9 years + 4.9 months. Mean ABP-ADC was 32.5% + 5.0%. In univariable analysis, higher ABP-ADC was associated with lower sBP (p < 0.01) and failing to achieve sBP targets (p < 0.01). Other intra-arrest physiologic parameters, quality metrics, and patient outcomes were similar across ABP-ADC groups. Using spline/ROC analysis and clinical judgement, the optimal ABP-ADC cut point was set at 33%. On multivariable analysis, sBP was significantly higher (point estimate 13.18 mmHg, CI95 5.30-21.07, p < 0.01) among patients with ABP-ADC < 33%. Other intra-arrest physiologic and patient outcomes were similar.

CONCLUSIONS

In this multicenter cohort, a lower ABP-ADC was associated with higher sBPs during CPR. Although ABP-ADC was not associated with outcomes, further studies are needed to define the interactions between CPR mechanics and intra arrest patient physiology.

Right-to-Left Shunts Occur During Cardiopulmonary Resuscitation: Echocardiographic Observations

OBJECTIVES

A significant proportion of the population has a patent foramen ovale (PFO). The intracardiac pressure during cardiopulmonary resuscitation (CPR) may differ from that of normal circulation, which may result in a right-to-left shunt in the presence of a PFO. In this study, transesophageal echocardiography (TEE) was conducted to evaluate whether CPR carried out in patients after cardiac arrest causes right-to-left shunt.

DESIGN

A retrospective observational study.

SETTING

One academic medical center from January 2017 to April 2020.

PATIENTS

Patients older than 20 years who suffered from nontraumatic out-of-hospital cardiac arrest (OHCA) and underwent intra-arrest TEE.

MEASUREMENT AND MAIN RESULTS

Patients who had microbubbles resulting from fluid injection in the right atrium, as indicated on TEE imaging, were included in the analysis. The presence of right-to-left shunt was defined as the appearance of microbubbles in the systemic circulation, including the left atrium, left ventricle, or aorta. A total of 97 patients were included in the final analysis. A right-to-left shunt was observed in 21 patients (21.6%), and no shunt was found in 76 patients (78.4%). The degree of the right-to-left shunt, determined by the number of microbubbles, was mild in 11 patients (52.4%), moderate in eight (38.0%), and severe in two (9.6%). Multivariate analysis showed that no factors were associated with the presence of right-to-left shunt during CPR.

CONCLUSIONS

Right-to-left shunts can be appreciated during CPR in patients who experience OHCA. Further studies are needed to verify its clinical significance.

The high impulse, palm lift technique for chest compression: Prospective, experimental, pilot study

BACKGROUND

The classic technique of high quality chest compression (HQCC) during cardiopulmonary resuscitation (CPR) is based on the International Liaison Committee on Resuscitation (ILCOR) guidelines which specify that the rescuer's hands should maintain constant contact with the chest surface but should not lean upon it, in order to provide full chest recoil. Since end-tidal CO2 (EtCO2) values have been shown to be a reliable indicator of CPR quality, we examined a method where classic HQCC was modified by a high impulse and palm lifting (HIPL) technique which merged rapid forceful compression with disconnection of the rescuer's palm from the patient's sternum during the recoil phase. The object of the study was to detect any differences in HIPL EtCO2 values in comparison with those from classic HQCC.

METHODS

We report a prospective pilot study in which we compared EtCO2 readings achieved during 2 min of classic HQCC technique with readings after implementing 2 min of the HIPL technique during out-of-hospital CPR, provided by medical emergency response teams for cases of cardiac arrest.

RESULTS

EtCO2 values obtained from16 cases who received HQCC followed by HIPL compressions showed a significant difference (p = 0.037) between the two techniques. Mean ± SD EtCO2 values after 2 min of each technique were: HQCC: 18 ± 9 mmHg; HIPL: 27 ± 11 mmHg; followed by a further 2 min of HQCC: 19 ± 11 mmHg. Linear regression showed that the differences in EtCO2 were associated with non - significant changes in ventilation rate (p = 0.493) and chest compression rate (p = 0.889).

CONCLUSIONS

The results obtained suggest that modifying HQCC with the HIPL technique led to a significant increase in EtCO2 values in comparison with classic HQCC, indicating an improvement in circulation during CPR. We think that these encouraging early results warrant a larger multi - centre study of HIPL.

Cardiopulmonary resuscitation may cause paradoxical embolism

This paper reports a case of paradoxical embolism of right heart thrombi visualized on transesophageal echocardiography during cardiopulmonary resuscitation (CPR). CPR may cause a right-to-left shunt by producing a sudden increase in right atrial pressure during the compression phase. In cardiac arrest patients with right heart thrombi who have received CPR, systemic embolization can occur owing to paradoxical embolism.

Kinetic analysis of cardiac compressions during cardiopulmonary resuscitation

PURPOSE

Little is known about the dynamics of cardiac compression during cardiopulmonary resuscitation (CPR). The purpose of this study was to investigate the dynamics of chest compressions by analyzing movement of the right ventricular free wall excursion during CPR.

MATERIALS AND METHODS

Patients older than 18 years with non-traumatic cardiac arrest who received CPR were enrolled. During CPR, transesophageal echocardiography (TEE) was performed and M-mode tracing was performed at the maximal compression area of the right ventricular free wall to measure the dynamics of cardiac compression.

RESULTS

Twenty patients (mean age, 71 years; 14 males) were enrolled. The median compression depth of the right ventricular free wall was 34.4 (IQR 24.5-44.5) mm. The median duration of one compression-relaxation cycle was 0.59 (IQR 0.58-0.60) s, which comprised 0.23 (IQR 0.19-0.27) s of compression and 0.36 (IQR 0.32-0.39) s of relaxation. The median compression velocity was 162 (IQR 95-215) mm/s, and the median relaxation velocity was 93 (IQR 75-121) mm/s. Compression depth was linearly correlated with mean compression velocity (r = 0.882, p < 0.001). Compression velocity had a negative correlation with the ratio of compression-relaxation time (r=-0.711, p < 0.001).

CONCLUSIONS

Maintaining high compression velocity is helpful in achieving adequate compression depth during CPR.

Mechanical versus manual chest compressions for cardiac arrest

BACKGROUND

Mechanical chest compression devices have been proposed to improve the effectiveness of cardiopulmonary resuscitation (CPR).

OBJECTIVES

To assess the effectiveness of resuscitation strategies using mechanical chest compressions versus resuscitation strategies using standard manual chest compressions with respect to neurologically intact survival in patients who suffer cardiac arrest.

SEARCH METHODS

On 19 August 2017 we searched the Cochrane Central Register of Controlled Studies (CENTRAL), MEDLINE, Embase, Science Citation Index-Expanded (SCI-EXPANDED) and Conference Proceedings Citation Index-Science databases. Biotechnology and Bioengineering Abstracts and Science Citation abstracts had been searched up to November 2009 for prior versions of this review. We also searched two clinical trials registries for any ongoing trials not captured by our search of databases containing published works: Clinicaltrials.gov (August 2017) and the World Health Organization International Clinical Trials Registry Platform portal (January 2018). We applied no language restrictions. We contacted experts in the field of mechanical chest compression devices and manufacturers.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), cluster-RCTs and quasi-randomised studies comparing mechanical chest compressions versus manual chest compressions during CPR for patients with cardiac arrest.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included five new studies in this update. In total, we included 11 trials in the review, including data from 12,944 adult participants, who suffered either out-of-hospital cardiac arrest (OHCA) or in-hospital cardiac arrest (IHCA). We excluded studies explicitly including patients with cardiac arrest caused by trauma, drowning, hypothermia and toxic substances. These conditions are routinely excluded from cardiac arrest intervention studies because they have a different underlying pathophysiology, require a variety of interventions specific to the underlying condition and are known to have a prognosis different from that of cardiac arrest with no obvious cause. The exclusions were meant to reduce heterogeneity in the population while maintaining generalisability to most patients with sudden cardiac death.The overall quality of evidence for the outcomes of included studies was moderate to low due to considerable risk of bias. Three studies (N = 7587) reported on the designated primary outcome of survival to hospital discharge with good neurologic function (defined as a Cerebral Performance Category (CPC) score of one or two), which had moderate quality evidence. One study showed no difference with mechanical chest compressions (risk ratio (RR) 1.07, 95% confidence interval (CI) 0.82 to 1.39), one study demonstrated equivalence (RR 0.79, 95% CI 0.60 to 1.04), and one study demonstrated reduced survival (RR 0.41, CI 0.21 to 0.79). Two other secondary outcomes, survival to hospital admission (N = 7224) and survival to hospital discharge (N = 8067), also had moderate quality level of evidence. No studies reported a difference in survival to hospital admission. For survival to hospital discharge, two studies showed benefit, four studies showed no difference, and one study showed harm associated with mechanical compressions. No studies demonstrated a difference in adverse events or injury patterns between comparison groups but the quality of data was low. Marked clinical and statistical heterogeneity between studies precluded any pooled estimates of effect.

AUTHORS' CONCLUSIONS

The evidence does not suggest that CPR protocols involving mechanical chest compression devices are superior to conventional therapy involving manual chest compressions only. We conclude on the balance of evidence that mechanical chest compression devices used by trained individuals are a reasonable alternative to manual chest compressions in settings where consistent, high-quality manual chest compressions are not possible or dangerous for the provider (eg, limited rescuers available, prolonged CPR, during hypothermic cardiac arrest, in a moving ambulance, in the angiography suite, during preparation for extracorporeal CPR [ECPR], etc.). Systems choosing to incorporate mechanical chest compression devices should be closely monitored because some data identified in this review suggested harm. Special attention should be paid to minimising time without compressions and delays to defibrillation during device deployment.

Effectiveness of feedback with a smartwatch for high-quality chest compressions during adult cardiac arrest: A randomized controlled simulation study

Previous studies have demonstrated the potential for using smartwatches with a built-in accelerometer as feedback devices for high-quality chest compression during cardiopulmonary resuscitation. However, to the best of our knowledge, no previous study has reported the effects of this feedback on chest compressions in action. A randomized, parallel controlled study of 40 senior medical students was conducted to examine the effect of chest compression feedback via a smartwatch during cardiopulmonary resuscitation of manikins. A feedback application was developed for the smartwatch, in which visual feedback was provided for chest compression depth and rate. Vibrations from smartwatch were used to indicate the chest compression rate. The participants were randomly allocated to the intervention and control groups, and they performed chest compressions on manikins for 2 min continuously with or without feedback, respectively. The proportion of accurate chest compression depth (≥5 cm and ≤6 cm) was assessed as the primary outcome, and the chest compression depth, chest compression rate, and the proportion of complete chest decompression (≤1 cm of residual leaning) were recorded as secondary outcomes. The proportion of accurate chest compression depth in the intervention group was significantly higher than that in the control group (64.6±7.8% versus 43.1±28.3%; p = 0.02). The mean compression depth and rate and the proportion of complete chest decompressions did not differ significantly between the two groups (all p>0.05). Cardiopulmonary resuscitation-related feedback via a smartwatch could provide assistance with respect to the ideal range of chest compression depth, and this can easily be applied to patients with out-of-hospital arrest by rescuers who wear smartwatches.

A Randomized Controlled Trial of Compression Rates during Cardiopulmonary Resuscitation

The objective of this study was to compare the efficacy of cardiopulmonary resuscitation (CPR) with 120 compressions per minute (CPM) to CPR with 100 CPM in patients with non-traumatic out-of-hospital cardiac arrest. We randomly assigned patients with non-traumatic out-of-hospital cardiac arrest into two groups upon arrival to the emergency department (ED). The patients received manual CPR either with 100 CPM (CPR-100 group) or 120 CPM (CPR-120 group). The primary outcome measure was sustained restoration of spontaneous circulation (ROSC). The secondary outcome measures were survival discharge from the hospital, one-month survival, and one-month survival with good functional status. Of 470 patients with cardiac arrest, 136 patients in the CPR-100 group and 156 patients in the CPR-120 group were included in the final analysis. A total of 69 patients (50.7%) in the CPR-100 group and 67 patients (42.9%) in the CPR-120 group had ROSC (absolute difference, 7.8% points; 95% confidence interval [CI], -3.7 to 19.2%; P = 0.183). The rates of survival discharge from the hospital, one-month survival, and one-month survival with good functional status were not different between the two groups (16.9% vs. 12.8%, P = 0.325; 12.5% vs. 6.4%, P = 0.073; 5.9% vs. 2.6%, P = 0.154, respectively). We did not find differences in the resuscitation outcomes between those who received CPR with 100 CPM and those with 120 CPM. However, a large trial is warranted, with adequate power to confirm a statistically non-significant trend toward superiority of CPR with 100 CPM. (

CLINICAL TRIAL REGISTRATION INFORMATION

www.cris.nih.go.kr, cris.nih.go.kr number, KCT0000231).

Hands-on defibrillation during active chest compressions: eliminating another interruption

After decades of research, effective chest compressions have emerged as a key component of high-quality cardiopulmonary resuscitation (CPR) for cardiac arrest patients. Minimizing interruptions in chest compressions is garnering increasing attention as a method to improve CPR quality and outcomes. Hands-on defibrillation has been suggested as both a safe and effective means of reducing interruptions in chest compressions. This article discusses the safety and efficacy of a novel and controversial method to reduce interruptions: hands-on defibrillation.

Brief inhalation of nitric oxide increases resuscitation success and improves 7-day-survival after cardiac arrest in rats: a randomized controlled animal study

Introduction

Inhaled nitric oxide (iNO) improves outcomes when given post systemic ischemia/reperfusion injury. iNO given during cardiopulmonary resuscitation (CPR) may therefore improve return of spontaneous circulation (ROSC) rates and functional outcome after cardiac arrest (CA).

Methods

Thirty male Sprague-Dawley rats were subjected to 10 minutes of CA and at least 3 minutes of CPR. Animals were randomized to receive either 0 (n = 10, Control), 20 (n = 10, 20 ppm), or 40 (n = 10, 40 ppm) ppm iNO during CPR until 30 minutes after ROSC. A neurological deficit score was assessed daily for seven days following the experiment. On day 7, brains, hearts, and blood were sampled for histological and biochemical evaluation.

Results

During CPR, 20 ppm iNO significantly increased diastolic arterial pressure (Control: 57 ± 5.04 mmHg; 20 ppm: 71.57 ± 57.3 mmHg, p < 0.046) and decreased time to ROSC (Control: 842 ± 21 s; 20 ppm: 792 ± 5 s, (p = 0.02)).

Thirty minutes following ROSC, 20 ppm iNO resulted in an increase in mean arterial pressure (Control: 83 ± 4 mmHg; 20 ppm: 98 ± 4 mmHg, p = 0.035), a less pronounced rise in lactate and inflammatory cytokine levels, and attenuated cardiac damage. Inhalation of NO at 20 ppm improved neurological outcomes in rats 2 to 7 days after CA and CPR. This translated into increases in 7 day survival (Control: 4; 20 ppm: 10; 40 ppm 6, (p ≤ 0.05 20 ppm vs Control and 40 ppm).

Conclusions

Our study revealed that breathing NO during CPR markedly improved resuscitation success, 7-day neurological outcomes and survival in a rat model of VF-induced cardiac arrest and CPR. These results support the beneficial effects of NO inhalation after cardiac arrest and CPR.

Simultaneous beat-to-beat assessment of arterial blood pressure and quality of cardiopulmonary resuscitation in out-of-hospital and in-hospital settings

OBJECTIVE

The current recommendation for depth and rate of chest compression (CC) during cardiopulmonary resuscitation (CPR) is based on limited hemodynamic data recorded during human CPR. We have evaluated the possible association between CC depth and rate and continuously measured arterial blood pressure during adult CPR.

METHODS

This prospective study included data from 104 patients resuscitated inside or outside hospital. Adequate data on continuously measured invasive arterial blood pressure (BP) and the quality of CPR from a defibrillator capable recording CPR quality parameters was successful in 39 patients. We used logistic regression and mixed effects modeling to identify CC depths and rates associated with systolic blood pressure (SBP) ≥ 85 mm Hg and diastolic blood pressure (DBP) ≥ 30 mm Hg.

RESULTS

We analyzed 41,575 compression-BP pairs. The values for blood pressure varied greatly between the patients. SBP varied from 25 to 225 mm Hg and DBP from 2 to 59 mm Hg. CC rate 100-120/min and CC depth ≥ 60 mm (without mattress deflection correction) was associated with DBP ≥ 30 mm Hg in both femoral (OR 1.14; 95% CI 1.03, 1.26; p<0.05) and radial (OR 4.70; 95% CI 3.92, 5.63; p<0.001) recordings. For any given subject there was a weak upward trend in blood pressure as CC depth increased.

CONCLUSION

Deeper CC does not equal higher BP in every patient. The heterogeneity of patients creates a challenge to find the optimal way to resuscitate patients individually.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov NCT00951704.

Chest compression rates and survival following out-of-hospital cardiac arrest

OBJECTIVE

Guidelines for cardiopulmonary resuscitation recommend a chest compression rate of at least 100 compressions/min. A recent clinical study reported optimal return of spontaneous circulation with rates between 100 and 120/min during cardiopulmonary resuscitation for out-of-hospital cardiac arrest. However, the relationship between compression rate and survival is still undetermined.

DESIGN

Prospective, observational study.

SETTING

Data is from the Resuscitation Outcomes Consortium Prehospital Resuscitation IMpedance threshold device and Early versus Delayed analysis clinical trial.

PARTICIPANTS

Adults with out-of-hospital cardiac arrest treated by emergency medical service providers.

INTERVENTIONS

None.

MEASUREMENTS MAIN RESULTS

Data were abstracted from monitor-defibrillator recordings for the first five minutes of emergency medical service cardiopulmonary resuscitation. Multiple logistic regression assessed odds ratio for survival by compression rate categories (<80, 80-99, 100-119, 120-139, ≥140), both unadjusted and adjusted for sex, age, witnessed status, attempted bystander cardiopulmonary resuscitation, location of arrest, chest compression fraction and depth, first rhythm, and study site. Compression rate data were available for 10,371 patients; 6,399 also had chest compression fraction and depth data. Age (mean±SD) was 67±16 years. Chest compression rate was 111±19 per minute, compression fraction was 0.70±0.17, and compression depth was 42±12 mm. Circulation was restored in 34%; 9% survived to hospital discharge. After adjustment for covariates without chest compression depth and fraction (n=10,371), a global test found no significant relationship between compression rate and survival (p=0.19). However, after adjustment for covariates including chest compression depth and fraction (n=6,399), the global test found a significant relationship between compression rate and survival (p=0.02), with the reference group (100-119 compressions/min) having the greatest likelihood for survival.

CONCLUSIONS

After adjustment for chest compression fraction and depth, compression rates between 100 and 120 per minute were associated with greatest survival to hospital discharge.

Mechanical versus manual chest compressions for cardiac arrest

BACKGROUND

This is the first update of the Cochrane review on mechanical chest compression devices published in 2011 (Brooks 2011). Mechanical chest compression devices have been proposed to improve the effectiveness of cardiopulmonary resuscitation (CPR).

OBJECTIVES

To assess the effectiveness of mechanical chest compressions versus standard manual chest compressions with respect to neurologically intact survival in patients who suffer cardiac arrest.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Studies (CENTRAL; 2013, Issue 12), MEDLINE Ovid (1946 to 2013 January Week 1), EMBASE (1980 to 2013 January Week 2), Science Citation abstracts (1960 to 18 November 2009), Science Citation Index-Expanded (SCI-EXPANDED) (1970 to 11 January 2013) on Thomson Reuters Web of Science, biotechnology and bioengineering abstracts (1982 to 18 November 2009), conference proceedings Citation Index-Science (CPCI-S) (1990 to 11 January 2013) and clinicaltrials.gov (2 August 2013). We applied no language restrictions. Experts in the field of mechanical chest compression devices and manufacturers were contacted.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), cluster RCTs and quasi-randomised studies comparing mechanical chest compressions versus manual chest compressions during CPR for patients with atraumatic cardiac arrest.

DATA COLLECTION AND ANALYSIS

Two review authors abstracted data independently; disagreement between review authors was resolved by consensus and by a third review author if consensus could not be reached. The methodologies of selected studies were evaluated by a single author for risk of bias. The primary outcome was survival to hospital discharge with good neurological outcome. We planned to use RevMan 5 (Version 5.2. The Nordic Cochrane Centre) and the DerSimonian & Laird method (random-effects model) to provide a pooled estimate for risk ratio (RR) with 95% confidence intervals (95% CIs), if data allowed.

MAIN RESULTS

Two new studies were included in this update. Six trials in total, including data from 1166 participants, were included in the review. The overall quality of included studies was poor, and significant clinical heterogeneity was observed. Only one study (N = 767) reported survival to hospital discharge with good neurological function (defined as a Cerebral Performance Category score of one or two), demonstrating reduced survival with mechanical chest compressions when compared with manual chest compressions (RR 0.41, 95% CI 0.21 to 0.79). Data from four studies demonstrated increased return of spontaneous circulation, and data from two studies demonstrated increased survival to hospital admission with mechanical chest compressions as compared with manual chest compressions, but none of the individual estimates reached statistical significance. Marked clinical heterogeneity between studies precluded any pooled estimates of effect.

AUTHORS' CONCLUSIONS

Evidence from RCTs in humans is insufficient to conclude that mechanical chest compressions during cardiopulmonary resuscitation for cardiac arrest are associated with benefit or harm. Widespread use of mechanical devices for chest compressions during cardiac events is not supported by this review. More RCTs that measure and account for the CPR process in both arms are needed to clarify the potential benefit to be derived from this intervention.

Timing positive-pressure ventilation during chest compression: the key to improving the thoracic pump?

Given the importance of increased coronary and cerebral perfusion pressure during cardiopulmonary resuscitation, the recommendation of limiting tidal volume and ventilation rate to 10 per minute in order not to inhibit venous return seems to be correct. However, although the resuscitation community believes that positive-pressure ventilation during cardiopulmonary resuscitation is bad for the circulation, proper timing of compression and ventilation may actually improve the circulation.

Relationship between chest compression rates and outcomes from cardiac arrest

BACKGROUND

Guidelines for cardiopulmonary resuscitation recommend a chest compression rate of at least 100 compressions per minute. Animal and human studies have reported that blood flow is greatest with chest compression rates near 120/min, but few have reported rates used during out-of-hospital (OOH) cardiopulmonary resuscitation or the relationship between rate and outcome. The purpose of this study was to describe chest compression rates used by emergency medical services providers to resuscitate patients with OOH cardiac arrest and to determine the relationship between chest compression rate and outcome.

METHODS AND RESULTS

Included were patients aged ≥ 20 years with OOH cardiac arrest treated by emergency medical services providers participating in the Resuscitation Outcomes Consortium. Data were abstracted from monitor-defibrillator recordings during cardiopulmonary resuscitation. Multiple logistic regression analysis assessed the association between chest compression rate and outcome. From December 2005 to May 2007, 3098 patients with OOH cardiac arrest were included in this study. Mean age was 67 ± 16 years, and 8.6% survived to hospital discharge. Mean compression rate was 112 ± 19/min. A curvilinear association between chest compression rate and return of spontaneous circulation was found in cubic spline models after multivariable adjustment (P=0.012). Return of spontaneous circulation rates peaked at a compression rate of ≈ 125/min and then declined. Chest compression rate was not significantly associated with survival to hospital discharge in multivariable categorical or cubic spline models.

CONCLUSIONS

Chest compression rate was associated with return of spontaneous circulation but not with survival to hospital discharge in OOH cardiac arrest.

Post-cardiac arrest syndrome: Mechanisms and evaluation of adrenal insufficiency

Cardiac arrest is one of the leading causes of death and represents maximal stress in humans. After restoration of spontaneous circulation, post-cardiac arrest syndrome is the predominant disorder in survivors. Besides the post-arrest brain injury, the post-resuscitation myocardial stunning, and the systemic ischemia/reperfusion response, this syndrome is characterized by adrenal insufficiency, a disorder that often remains undiagnosed. The pathophysiology of adrenal insufficiency has not been elucidated. We performed a comprehensive search of three medical databases in order to describe the major pathophysiological disturbances which are responsible for the occurrence of the disorder. Based on the available evidence, this article will help physicians to better evaluate and understand the hidden yet deadly post-cardiac arrest adrenal insufficiency.

Mechanical versus manual chest compressions for cardiac arrest

BACKGROUND

Mechanical chest compression devices have been proposed to improve the effectiveness of cardiopulmonary resuscitation (CPR).

OBJECTIVES

To assess the effectiveness of mechanical chest compressions versus standard manual chest compressions with respect to neurologically intact survival in patients who suffer cardiac arrest.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Studies (CENTRAL) on The Cochrane Library, MEDLINE, EMBASE, Science Citation abstracts, Biotechnology and Bioengineering abstracts and Clinicaltrials.gov in November 2009. No language restrictions were applied. Experts in the field of mechanical chest compression devices and manufacturers were contacted.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), cluster RCTs and quasi-randomised studies comparing mechanical chest compressions to manual chest compressions during CPR for patients with atraumatic cardiac arrest.

DATA COLLECTION AND ANALYSIS

Two authors (SCB and LJM) abstracted data independently. Disagreement between reviewers was resolved by consensus and a third author (BB) if consensus could not be reached. The methodologies of selected studies were evaluated for risk of bias by a single author (SCB). The primary outcome was survival to hospital discharge with good neurologic outcome. We used the DerSimonian & Laird method (random-effects model) to provide a pooled estimate for relative risk with 95% confidence intervals.

MAIN RESULTS

Four trials, including data from 868 patients, were included in the review. The overall quality of included studies was poor and significant clinical heterogeneity was observed. Only one study (N = 767) reported survival to hospital discharge with good neurologic function (as defined as a Cerebral Performance Category score of 1 or 2), demonstrating reduced survival with mechanical chest compressions when compared with manual chest compressions (RR 0.41 (95% CI 0.21- 0.79). Data from other studies included in this review were used to calculate relative risks for having a return of spontaneous circulation (2 studies, N = 51, pooled RR 2.81, 95% CI 0.96 to 8.22) and survival to hospital admission (1 study, N = 17, RR 4.13, 95% CI 0.19 to 88.71) in patients who received mechanical chest compressions versus those who received manual chest compressions.

AUTHORS' CONCLUSIONS

There is insufficient evidence from human RCTs to conclude that mechanical chest compressions during cardiopulmonary resuscitation for cardiac arrest is associated with benefit or harm. Widespread use of mechanical devices for chest compressions during cardiac is not supported by this review. More RCTs that measure and account for CPR process in both arms are needed to clarify the potential benefit from this intervention.

Part 7: CPR techniques and devices: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

A variety of CPR techniques and devices may improve hemodynamics or short-term survival when used by well-trained providers in selected patients. All of these techniques and devices have the potential to delay chest compressions and defibrillation. In order to prevent delays and maximize efficiency, initial training, ongoing monitoring, and retraining programs should be offered to providers on a frequent and ongoing basis. To date, no adjunct has consistently been shown to be superior to standard conventional (manual) CPR for out-of-hospital basic life support, and no device other than a defibrillator has consistently improved long-term survival from out-of-hospital cardiac arrest.

Chest compression-only cardiocerebral resuscitation

PURPOSE OF REVIEW

Conventional cardiopulmonary resuscitation (CPR) by bystanders with chest compressions and mouth-to-mouth ventilation has been documented to save life. Nevertheless, despite four decades of promulgation, it is a serious problem that the majority of bystanders are unwilling or unable to perform conventional CPR. I review the efficacy of chest compression-only cardiocerebral resuscitation (CCR) for all adult patients with out-of-hospital cardiac arrest.

RECENT FINDINGS

Recent observational studies showed that chest compression-only CCR by bystanders was equivalent or superior to conventional CPR in adult patients with out-of-hospital cardiac arrest in terms of neurological benefits. In 2008, the American Heart Association Emergency Cardiovascular Care committee recommended that bystanders who witness a sudden collapse in an adult should give chest compressions without ventilations (chest compression-only CCR; hands-only CPR). Furthermore, an observational study showed that chest compression-only CCR by emergency medical services personnel was a preferable approach to advanced cardiovascular life support for adult patients with out-of-hospital cardiac arrest.

SUMMARY

To save more lives, I hope that compression-only CCR by citizen is generally, known, recommended, and taught to the public, because chest compression-only CCR by citizen is the preferable approach to basic life support for adult victims with out-of-hospital cardiac arrest.

Percutaneous left ventricular assist in ischemic cardiac arrest

BACKGROUND

Ischemic cardiac arrest represents a challenge for optimal emergency revascularization therapy. A percutaneous left ventricular assist device (LVAD) may be beneficial.

OBJECTIVE

To determine the effect of a percutaneous LVAD during cardiac arrest without chest compressions and to assess the effect of fluid loading.

DESIGN

Totally, 16 pigs randomized to either conventional or intensive fluid with LVAD support during ventricular fibrillation (VF).

SETTING

Acute experimental trial with pigs under general anesthesia.

SUBJECTS

Farm pigs of both sexes.

INTERVENTIONS

After randomization for fluid infusion, VF was induced by balloon occlusion of the proximal left anterior descending artery. LVAD and fluid were started after VF had been induced.

MEASUREMENTS

Brain, kidney, myocardial tissue perfusion, and cardiac index were measured with the microsphere injection technique at baseline, 3, and 15 minutes. Additional hemodynamic monitoring continued until 30 minutes.

MAIN RESULTS

At 15 minutes, vital organ perfusion was maintained without significant differences between the two groups. Mean cardiac index at 3 minutes of VF was 1.2 L x min(-1) x m2 (29% of baseline, p < 0.05). Mean perfusion at 3 minutes was 65% in the brain and 74% in the myocardium compared with baseline (p < 0.05), then remained unchanged during the initial 15 minutes. At 30 minutes, LVAD function was sustained in 11 of 16 animals (8 of 8 intensified fluid vs. 3 of 8 conventional fluid) and was associated with intensified fluid loading (p < 0.001).

CONCLUSIONS

During VF, a percutaneous LVAD may sustain vital organ perfusion. A potential clinical role of the device during cardiac arrest has yet to be established.

Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway

THE AIM OF THE STUDY

Despite the emphasis of cardiopulmonary resuscitation (CPR) quality, the performance of on-site CPR is reported to be frequently unsuccessful. In order to improve CPR quality, various feedback systems have been developed, but they have not yet been widely used on site due to low economic efficiency. The present study was attempted to determine whether CPR quality can be improved using audio tone guidance.

THE METHODS

A total of 80 seniors at our medical school and college of nursing participated in the study. After they were trained in CPR according to the 2005 guidelines, they performed CPR using a cardiac arrest model with an advanced airway. The participants were organized into 40 groups. After they took Test 1 without any feedback for 2 min, they were randomly assigned to the feedback and control groups and took Test 2 for 2 min. In the feedback group, a low-pitched sound was delivered every 0.6 s for the guidance of chest compression and a high-pitched sound was simultaneously delivered every 10 deliveries of a low-pitched sound for the guidance of ventilation at 6s intervals.

THE RESULTS

In the feedback group the mean compression rate significantly improved in accuracy from 111.5+/-13.7/min to 100.1+/-3.2/min (P<0.01), and ventilation counts significantly improved in accuracy from 7.4+/-1.8/min to 9.9+/-0.3/min (P<0.01). However, the mean compression depth significantly decreased from 39.3+/-9.5 mm to 35.8+/-8.2 mm (P<0.01).

THE CONCLUSION

Audio tone guidance ensures better chest compression rate and ventilation rate but this does not necessarily result in a better CPR quality.

Two rescuer resuscitation—Mission impossible?

OBJECTIVE

Advanced life support (ALS) in a cardiac arrest is usually performed by a team consisting of three people. The medical team of a Helicopter Emergency Medical Service (HEMS) often consists of two rescuers only. Due to that reason an algorithm was developed to provide ALS with two people. During the initial phase the rescuer in the over-the-head position provides one man CPR while the second rescuer prepares all advanced measures. When all preparations are complete both rescuers are able to provide ALS.

MATERIAL AND METHODS

A computer controlled manikin (Ambu Mega Code Simulator System MCS with online documentation was used to test the entire medical staff during 10 min of persistent VF.

RESULTS

The 20 teams were tested. Following data were recorded: no-flow-time 96.4+/-11s (16.1+/-1.8%), chest compression frequency 120.1+/-5.1 min (-1), ventilation frequency=9 min (-1), number of chest compressions per session 1013.7+/-45.9, depth of chest compressions 46.6+/-2.5mm, total number of chest compressions=20,274, total number of ventilations=1893. For ALS measures the following data were recorded: tracheal intubation (TI) was finished after 60.7+/-9.8s, duration of TI : maneuver = 15.7+/-4.4s, end of initial phase=188.9+/-26.3s, i.v. administration of adrenaline after 387.7+/-33.6s, i.v. administration of amiodarone after 507.9+/-36.9s and four shocks after: 138.0+/-15.9, 266.8+/-16.1, 398.0+/-20.1 and 526.8+/-23.6s.

CONCLUSION

We proved the feasibility of the algorithm in a manikin setting. Further observations have to prove the algorithm in real CPR situations.

[The new 2005 resuscitation guidelines of the European Resuscitation Council: comments and supplements]

The new CPR guidelines are based on a scientific consensus which was reached by 281 international experts. Chest compressions (100/min, 4-5 cm deep) should be performed in a ratio of 30:2 with ventilation (tidal volume 500 ml, Ti 1 s, FIO2 if possible 1.0). After a single defibrillation attempt (initially biphasic 150-200 J, monophasic 360 J, subsequently with the respective highest energy), chest compressions are initiated again immediately for 2 min. Endotracheal intubation is the gold standard; other airway devices may be employed as well depending on individual skills. Drug administration routes for adults and children: first choice IV, second choice intraosseous, third choice endobronchial [epinephrine dose 2-3x (adults) or 10x (pediatric patients) higher than IV]. Vasopressors: 1 mg epinephrine every 3-5 min IV. After the third unsuccessful defibrillation attempt amiodarone IV (300 mg); repetition (150 mg) possible. Sodium bicarbonate (1 ml/kg 8.4%) only in excessive hyperkalemia, metabolic acidosis, or intoxication with tricyclic antidepressants. Consider atropine (3 mg) and aminophylline (5 mg/kg). Thrombolysis during spontaneous circulation only in myocardial infarction or massive pulmonary embolism; during CPR only during massive pulmonary embolism. Cardiopulmonary bypass only after cardiac surgery, hypothermia or intoxication. Pediatrics: best improvement in outcome by preventing cardiocirculatory collapse. Alternate chest thumps and chest compression (infants), or abdominal compressions (>1-year-old) in foreign body airway obstruction. Initially five breaths, followed by chest compressions (100/min; approximately 1/3 of chest diameter): ventilation ratio 15:2. Treatment of potentially reversible causes (4 "Hs", "HITS": hypoxia, hypovolemia, hypo- and hyperkaliemia, hypothermia, cardiac tamponade, intoxication, thrombo-embolism, tension pneumothorax). Epinephrine 10 microg/kg IV or intraosseously, or 100 microg (endobronchially) every 3-5 min. Defibrillation (4 J/kg; monophasic oder biphasic) followed by 2 min CPR, then ECG and pulse check. Newborns: inflate the lungs with bag-valve mask ventilation. If heart rate<60/min chest compressions:ventilation ratio 3:1 (120 chest compressions/min). Postresuscitation phase: initiate mild hypothermia [32-34 degrees C for 12-24 h; slow rewarming (<0.5 degrees C/h)]. Prediction of CPR outcome is not possible at the scene; determining neurological outcome within 72 h after cardiac arrest with evoked potentials, biochemical tests and physical examination. Even during low suspicion for an acute coronary syndrome, record a prehospital 12-lead ECG. In parallel to pain therapy, aspirin (160-325 mg PO or IV) and in addition clopidogrel (300 mg PO). As antithrombin, heparin (60 IU/kg, max. 4000 IU) or enoxaparine. In ST-segment elevation myocardial infarction, define reperfusion strategy depending on duration of symptoms until PCI (prevent delay>90 min until PCI). Stroke is an emergency and needs to be treated in a stroke unit. A CT scan is the most important evaluation, MRT may replace a CT scan. After hemorrhage exclusion, thrombolysis within 3 h of symptom onset (0.9 mg/kg rt-PA IV; max 90 mg within 60 min, 10% of the entire dosage as initial bolus, no aspirin, no heparin within the first 24 h). In severe hemorrhagic shock, definite control of bleeding is the most important goal. For successful CPR of trauma patients, a minimal intravascular volume status and management of hypoxia are essential. Aggressive fluid resuscitation, hyperventilation, and excessive ventilation pressure may impair outcome in severe hemorrhagic shock. Despite bad prognosis, CPR in trauma patients may be successful in select cases. Any CPR training is better than nothing; simplification of contents and processes remains important.

Haemodynamics of cardiac arrest and resuscitation

PURPOSE OF REVIEW

This review will summarize the available data regarding the haemodynamic changes occurring following cardiac arrest in humans and animal models.

RECENT FINDINGS

Following cardiac arrest due to ventricular fibrillation without cardiopulmonary resuscitation, blood flow exponentially falls but continues for approximately 5 min until the pressure gradient between the aorta and the right heart is completely dissipated. During cardiopulmonary resuscitation forward flow occurs into the aorta during the compression phase. Coronary blood flow is retrograde during the compression phase and antegrade during the decompression phase. Carotid blood flow takes over a minute to reach plateau levels following the initiation of chest compressions, and even brief interruptions of compressions result in a dramatic reduction in carotid blood flow which takes a minute or so to recover to plateau levels when compressions are reinstituted. Coronary perfusion pressure during the release phase of cardiopulmonary resuscitation has been shown to be a powerful predictor of the likelihood of recovery of spontaneous circulation following restoration of electrical activity.

SUMMARY

Recent studies have provided important insights into the haemodynamics of cardiac arrest and of cardiopulmonary resuscitation which may inform more effective strategies for the management of cardiac arrest in the future.

Improved hemodynamic performance with a novel chest compression device during treatment of in-hospital cardiac arrest

INTRODUCTION

The purpose of this pilot clinical study was to determine if a novel chest compression device would improve hemodynamics when compared to manual chest compression during cardiopulmonary resuscitation (CPR) in humans. The device is an automated self-adjusting electromechanical chest compressor based on AutoPulse technology (Revivant Corporation) that uses a load distributing compression band (A-CPR) to compress the anterior chest.

METHODS

A total of 31 sequential subjects with in-hospital sudden cardiac arrest were screened with institutional review board approval. All subjects had received prior treatment for cardiac disease and most had co-morbidities. Subjects were included following 10 min of failed standard advanced life support (ALS) protocol. Fluid-filled catheters were advanced into the thoracic aorta and the right atrium and placement was confirmed by pressure waveforms and chest radiograph. The coronary perfusion pressure (CPP) was measured as the difference between the aortic and right atrial pressure during the chest compression's decompressed state. Following 10 min of failed ALS and catheter placement, subjects received alternating manual and A-CPR chest compressions for 90 s each. Chest compressions were administered without ventilation pauses at 100 compressions/min for manual CPR and 60 compressions/min for A-CPR. All subjects were intubated and ventilated by bag-valve at 12 breaths/min between compressions. Epinephrine (adrenaline) (1mg i.v. bolus) was given at the request of the attending physician at 3-5 min intervals. Usable pressure signals were present in 16 patients (68 +/- 6 years, 5 female), and data are reported from those patients only. A-CPR chest compressions increased peak aortic pressure when compared to manual chest compression (153 +/- 28 mmHg versus 115 +/- 42 mmHg, P < 0.0001, mean +/- S.D.). Similarly, A-CPR increased peak right atrial pressure when compared to manual chest compression (129 +/- 32 mmHg versus 83 +/- 40 mmHg, P < 0.0001). Furthermore, A-CPR increased CPP over manual chest compression (20 +/- 12 mmHg versus 15 +/- 11 mmHg, P < 0.015). Manual chest compressions were of consistent high quality (51 +/- 20 kg) and in all cases met or exceeded American Heart Association guidelines for depth of compression.

CONCLUSION

Previous research has shown that increased CPP is correlated to increased coronary blood flow and increased rates of restored native circulation from sudden cardiac arrest. The A-CPR system using AutoPulse technology demonstrated increased coronary perfusion pressure over manual chest compression during CPR in this terminally ill patient population.

Resuscitating an idea: prone CPR

Cardiopulmonary resuscitation (CPR) is widely recognized as an essential part of the medical response to cardiac arrest. Traditional ('basic') CPR has remained essentially unchanged for 40 years despite major problems with training and performance, and survival rates from out-of-hospital cardiac arrest remain disappointingly low, despite massive resources devoted to CPR training and public awareness. More than a decade ago, an article described an alternative method-prone CPR-which offered many potential advantages over traditional CPR, including much simpler training and increased likelihood of actual performance by bystanders. The article received little notice at the time; however, the method of prone CPR merits further consideration based on a number of subsequent supporting studies and case reports. Prone CPR may represent a superior alternative to traditional CPR; research into its effectiveness should be given high priority.

Cardiopulmonary resuscitation using the cardio vent device in a resuscitation model

To compare the "Bellows on Sternum Resuscitation" (BSR) device that permits simultaneous compression and ventilation by one rescuer with two person cardiopulmonary resuscitation (CPR) with bag-valve-mask (BVM) ventilation in a single blind crossover study performed in the laboratory setting. Tidal volume and compression depth were recorded continuously during 12-min CPR sessions with the BSR device and two person CPR. Six CPR instructors performed a total of 1,894 ventilations and 10,532 compressions in 3 separate 12-min sessions. Mean tidal volume (MTV) and compression rate (CR) with the BSR device differed significantly from CPR with the BVM group (1242 mL vs. 1065 mL, respectively, p = 0.0018 and 63.2 compressions per minute (cpm) vs. 81.3 cpm, respectively, p = 0.0076). Error in compression depth (ECD) rate of 9.78% was observed with the BSR device compared to 8.49% with BMV CPR (p = 0.1815). Error rate was significantly greater during the second half of CPR sessions for both BSR and BVM groups. It is concluded that one-person CPR with the BSR device is equivalent to two-person CPR with BVM in all measured parameters except for CR. Both groups exhibited greater error rate in CPR performance in the latter half of 12-min CPR sessions.