The Physiology of Cardiopulmonary Resuscitation

Effect of real-time and post-event feedback in out-of-hospital cardiac arrest attended by EMS - A systematic review and meta-analysis

OBJECTIVES

A systematic review to determine if cardiopulmonary resuscitation (CPR) guided by either real-time or post-event feedback could improve CPR quality or patient outcome compared to unguided CPR in out-of-hospital cardiac arrest (OHCA).

METHODS

Four databases were searched; PubMed, Embase, CINAHL, and Cochrane Library in August 2020 for post 2010 literature on OHCA in adults. Critical outcomes were chest compression depth, rate and fraction. Important outcomes were any return of spontaneous circulation, survival to hospital and survival to discharge.

RESULTS

A total of 9464 studies were identified with 61 eligibility for full text screening. A total of eight studies was included in the meta-analysis. Five studies investigated real-time feedback and three investigated post-event feedback. Meta-analysis revealed that real-time feedback statistically improves compression depth and rate while post-event feedback improved depth and fraction. Feedback did not statistically improve patient outcome but an improvement in absolute numbers revealed a clinical effect of feedback. Heterogenity varied from "might not be important" to "considerable".

CONCLUSION

To significantly improve CPR quality real-time and post-event feedback should be combined. Neither real-time nor post event feedback could statistically be associated with patient outcome however, a clinical effect was detected. The conclusions reached were based on few studies of low to very low quality.

PROSPERO REGISTRATION

CRD42019133881.

Survival of pediatric patients after cardiopulmonary resuscitation for in-hospital cardiac arrest: a systematic review and meta-analysis

BACKGROUND

In-hospital cardiac arrest is a major public health issue. It is a serious condition; most probably end up with death within a few minutes even with corrective measures. However, cardiopulmonary resuscitation is expected to increase the probability of survival and prevent neurological disabilities in patients with cardiac arrest. Having a pooled prevalence of survival to hospital discharge after cardiopulmonary resuscitation is vital to develop strategies targeted to increase probability of survival among patients with cardiac arrest. Therefore, this systematic review and meta-analysis was aimed to assess the pooled prevalence of survival to hospital discharge among pediatric patients who underwent cardiopulmonary resuscitation for in-hospital cardiac arrest.

METHODS

PubMed, Google Scholar, and Cochrane review databases were searched. To have current (five-year) evidence, only studies published in 2016 to 2020 were included. The weighted inverse variance random-effects model at 95%CI was used to estimate the pooled prevalence of survival. Heterogeneity assessment, test of publication bias, and subgroup analyses were also employed accordingly.

RESULTS

Twenty-five articles with a total sample size of 28,479 children were included in the final analysis. The pooled prevalence of survival to hospital discharge was found to be 46% (95% CI = 43.0-50.0%; I2 = 96.7%; p < 0.001). Based on subgroup analysis by "continent" and "income level", lowest prevalence of pooled survival was observed in Asia (six studies; pooled survival =36.0% with 95% CI = 19.01-52.15%; I2 = 97.4%; p < 0.001) and in low and middle income countries (six studies, pooled survival = 34.0% with 95% CI = 17.0-51.0%, I2 = 97.67%, p < 0.001) respectively.

CONCLUSION

Although there was an extremely high heterogeneity among reported results (I2 = 96.7%), in this meta-analysis more than half of pediatric patients (54%) who underwent cardiopulmonary resuscitation for in-hospital cardiac arrest did not survived to hospital discharge. Therefore, developing further strategies and encouraging researches might be crucial.

ETView VivaSight single lumen vs. conventional intubation in simulated studies: a systematic review and meta-analysis

Objective

The ETView VivaSight single lumen airway tube (ETView) is a tracheal tube incorporating a video camera. We carried out a meta-analysis of previous simulation studies by inexperienced personnel to determine if the ETView could improve the success rate of first-attempt intubation.

Methods

We collected data from randomized controlled trials comparing the use of the ETView VivaSight single lumen versus a conventional endotracheal tube in a simulated manikin or cadaver study.

Results

Eleven studies (558 participants, 3,254 intubations, and 19 scenarios) were included. The ETView had a significantly higher success rate and shorter insertion time than conventional intubation in both normal airways (with or without chest compression) and in difficult airways. In addition, the ETView demonstrated better results in terms of a higher rate of Cormack−Lehane grade 1 and a lower incidence of dental trauma.

Conclusions

Inexperienced personnel can insert the ETView more rapidly and with a higher intubation success rate compared with a conventional tube.

Retrospective study of gross and histopathologic lesions associated with closed chest cardiopulmonary resuscitation in dogs

OBJECTIVES

To investigate and characterise the incidence of iatrogenic complications secondary to closed chest cardiopulmonary resuscitation in dogs.

MATERIALS AND METHODS

Necropsy reports and histologic sections of tissues were retrospectively examined from 180 dogs that had received closed chest cardiopulmonary resuscitation to determine lesions associated with resuscitation.

RESULTS

The most common complication was pulmonary haemorrhage (81/163, 49.7%, 95% confidence interval: 42.1 to 57.3), although only nine dogs had pulmonary haemorrhage of at least moderate severity. Liver fractures occurred in 16 of 180 cases (8.9%, 95% confidence interval: 5.5 to 14.0). Blood loss of >15% of blood volume into the abdomen and/or thorax occurred in 13 of 180 cases (7.2%, 95% confidence interval: 4.2 to 12.1).

CLINICAL SIGNIFICANCE

Significant haemorrhage secondary to cardiopulmonary resuscitation may decrease the chances of achieving the return of spontaneous circulation or may cause or compound ischemic damage to critical organs if the return of spontaneous circulation is achieved. Following successful cardiopulmonary resuscitation, animals should be screened for cavitary or pulmonary haemorrhage, as significant haemorrhage could be a factor in recurrence of cardiac arrest.

Alternating fast and slow chest compression rates during CPR improved hemodynamics

INTRODUCTION

Mechanical chest compression devices allow for variation in chest compression (CCs) characteristics from moment to moment, enabling therapy that is not feasible for manual CCs. Effects of varying compressions over time have not been studied. In a randomized trial in an experimental model of prolonged cardiac arrest, we compared time-varying CPR (TVCPR), alternating between 100 and 200 compressions per minute (cpm) every 6 s, to guidelines CPR (Control).

METHODS

Ventricular fibrillation (VF) was electrically induced in 20 anesthetized pigs (28.4-45.8 kg). Following 10 min of untreated VF, cardiopulmonary resuscitation (CPR) began, randomized to TVCPR or Control. Rate of return of spontaneous circulation (ROSC), 4-h survival, and hemodynamics during the first 5 min of CPR were compared between groups. Moment-to-moment hemodynamic effects of changing the CC rate were analyzed.

RESULTS

TVCPR improved the proportion of ROSC over time compared to Control (p < 0.05) but ROSC (9/10 vs. 5/10) and 4-h survival (8/10 vs 5/10) did not differ significantly between groups. During CPR, coronary and cerebral perfusion pressures and femoral artery pressure did not differ between groups; however, end-tidal CO2 and mixed venous O2 saturation were higher, and pulmonary artery pressure was lower (p < 0.05) for TVCPR than Control. During TVCPR, switching to 100 cpm increased coronary perfusion pressure (p < 0.05), and switching to 200 cpm increased cerebral perfusion pressure (p < 0.05).

CONCLUSIONS

Time-varying CPR significantly improved indicators of net forward blood flow and proportion of ROSC over time without negatively impacting perfusion pressures. Alternating CC rate alternates between perfusion pressures favoring the brain and those favoring the heart. Time-varying CPR represents a new avenue of research for optimizing CPR.

INSTITUTIONAL PROTOCOL NUMBER

University of Alabama at Birmingham Institutional Animal Care and Use Committee (IACUC) Protocol Number 140406860.

Influence of Cardiopulmonary Resuscitation Coaching on Interruptions in Chest Compressions During Simulated Pediatric Cardiac Arrest

OBJECTIVES

To determine the impact of a cardiopulmonary resuscitation coach on the frequency and duration of pauses during simulated pediatric cardiac arrest.

DESIGN

This is a secondary analysis of video data collected from a prospective multicenter trial. Forty simulated pediatric cardiac arrest scenarios (20 noncoach and 20 coach teams), each lasting 18 minutes in duration, were reviewed by three clinical experts to document events surrounding each pause in chest compressions.

SETTING

Four pediatric academic medical centers from Canada and the United States.

SUBJECTS

Two-hundred healthcare providers in five-member interprofessional resuscitation teams that included either a cardiopulmonary resuscitation coach or a noncoach clinical provider.

INTERVENTIONS

Teams were randomized to include either a trained cardiopulmonary resuscitation coach or an additional noncoach clinical provider.

MEASUREMENTS AND MAIN RESULTS

The frequency, duration, and associated factors with each interruption in chest compressions were recorded and compared between the groups with and without a cardiopulmonary resuscitation coach, using t tests, Wilcoxon rank-sum tests, or chi-squared tests, depending on the distribution and types of outcome variables. Mixed-effect linear models were used to explore the effect of cardiopulmonary resuscitation coaching on pause durations, accounting for multiple measures of pause duration within teams. A total of 655 pauses were identified (noncoach n = 304 and coach n = 351). Cardiopulmonary resuscitation-coached teams had decreased total mean pause duration (98.6 vs 120.85 s, p = 0.04), decreased intubation pause duration (median 4.0 vs 15.5 s, p = 0.002), and similar mean frequency of pauses (17.6 vs 15.2, p = 0.33) when compared with noncoach teams. Teams with cardiopulmonary resuscitation coaches are more likely to verbalize the need for pause (86.5% vs 73.7%, p < 0.001) and coordinate change of the compressors, rhythm check, and pulse check (31.7% vs 23.2%, p = 0.05). Teams with cardiopulmonary resuscitation coach have a shorter pause duration than non-coach teams, adjusting for number and types of tasks performed during the pause.

CONCLUSIONS

When compared with teams without a cardiopulmonary resuscitation coach, the inclusion of a trained cardiopulmonary resuscitation coach leads to improved verbalization before pauses, decreased pause duration, shorter pauses during intubation, and better coordination of key tasks during chest compression pauses.

Cardiopulmonary Resuscitation in the Prone Position in the Operating Room or in the Intensive Care Unit: A Systematic Review

The prone position is commonly used in certain surgical procedures and to improve oxygenation in mechanically ventilated patients with acute respiratory distress syndrome (ARDS). Cardiorespiratory arrest (CRA) in this position may be more challenging to treat because care providers trained in conventional cardiopulmonary resuscitation (CPR) may not be familiar with CPR in the prone position. The aim of this systematic review is to provide an overview of current evidence regarding the methodology, efficacy, and experience of CPR in the prone position, in patients with the airway already secured. The search strategy included PubMed, Scopus, and Google Scholar. All studies published up to April 2020 including CRA or CPR in the prone position were included. Of the 268 articles located, 52 articles were included: 5 review articles, 8 clinical guidelines in which prone CPR was mentioned, 4 originals, 27 case reports, and 8 editorials or correspondences. Data from reviewed clinical studies confirm that CPR in the prone position is a reasonable alternative to supine CPR when the latter cannot be immediately implemented, and the airway is already secured. Defibrillation in the prone position is also possible. Familiarizing clinicians with CPR and defibrillation in the prone position may improve CPR performance in the prone position.

Improving post-cardiac arrest cerebral perfusion pressure by elevating the head and thorax

AIM

The optimal head and thorax position after return of spontaneous circulation (ROSC) following cardiac arrest (CA) is unknown. This study examined whether head and thorax elevation post-ROSC is beneficial, in a porcine model.

METHODS

Protocol A: 40 kg anesthetized pigs were positioned flat, after 7.75 min of untreated CA the heart and head were elevated 8 and 12 cm, respectively, above the horizontal plane, automated active compression decompression (ACD) plus impedance threshold device (ITD) CPR was started, and 2 min later the heart and head were elevated 10 and 22 cm, respectively, over 2 min to the highest head up position (HUP). After 30 min of CPR pigs were defibrillated and randomized 10 min later to four 5-min epochs of HUP or flat position. Multiple physiological parameters were measured. In Protocol B, after 6 min of untreated VF, pigs received 6 min of conventional CPR flat, and after ROSC were randomized HUP versus Flat as in Protocol A. The primary endpoint was cerebral perfusion pressure (CerPP). Multivariate analysis-of-variance (MANOVA) for repeated measures was used. Data were reported as mean ± SD.

RESULTS

In Protocol A, intracranial pressure (ICP) (mmHg) was significantly lower post-ROSC with HUP (9.1 ± 5.5) versus Flat (18.5 ± 5.1) (p < 0.001). Conversely, CerPP was higher with HUP (62.5 ± 19.9) versus Flat (53.2 ± 19.1) (p = 0.004), respectively. Protocol A and B results comparing HUP versus Flat were similar.

CONCLUSION

Post-ROSC head and thorax elevation in a porcine model of cardiac arrest resulted in higher CerPP and lower ICP values, regardless of VF duration or CPR method.

IACUC PROTOCOL NUMBER

19-09.

Retracted: Facemasks in the COVID-19 era: A health hypothesis

Many countries across the globe utilized medical and non-medical facemasks as non-pharmaceutical intervention for reducing the transmission and infectivity of coronavirus disease-2019 (COVID-19). Although, scientific evidence supporting facemasks’ efficacy is lacking, adverse physiological, psychological and health effects are established. Is has been hypothesized that facemasks have compromised safety and efficacy profile and should be avoided from use. The current article comprehensively summarizes scientific evidences with respect to wearing facemasks in the COVID-19 era, providing prosper information for public health and decisions making.

Optimizing airway management and ventilation during prehospital advanced life support in out-of-hospital cardiac arrest: A narrative review

Airway management and ventilation are essential components of cardiopulmonary resuscitation to achieve oxygen delivery in order to prevent hypoxic injury and increase the chance of survival. Weighing the relative benefits and downsides, the best approach is a staged strategy; start with a focus on high-quality chest compressions and defibrillation, then optimize mask ventilation while preparing for advanced airway management with a supraglottic airway device. Endotracheal intubation can still be indicated, but has the largest downsides of all advanced airway techniques. Whichever stage of airway management, ventilation and chest compression quality should be closely monitored. Capnography has many advantages and should be used routinely. Optimizing ventilation strategies, harmonizing ventilation with mechanical chest compression devices, and implementation in complex and stressful environments are challenges we need to face through collaborative innovation, research, and implementation.

Acute-stage MRI cerebral oxygen consumption biomarkers predict 24-hour neurological outcome in a rat cardiac arrest model

Brain injury following cardiac arrest (CA) is thought to be caused by a sudden loss of blood flow resulting in disruption in oxygen delivery, neural function and metabolism. However, temporal trajectories of the brain's physiology in the first few hours following CA have not been fully characterized. Furthermore, the extent to which these early measures can predict future neurological outcomes has not been determined. The present study sought to perform dynamic measurements of cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO₂ ) with MRI in the first 3 hours following the return of spontaneous circulation (ROSC) in a rat CA model. It was found that CBF, OEF and CMRO₂ all revealed a time-dependent increase during the first 3 hours after the ROSC. Furthermore, the temporal trajectories of CBF and CMRO₂ , but not OEF, were different across rats and related to neurologic outcomes at a later time (24 hours after the ROSC) (P < .001). Rats who manifested better outcomes revealed faster increases in CBF and CMRO₂ during the acute stage. When investigating physiological parameters measured at a single time point, CBF (ρ = 0.82, P = .004) and CMRO₂ (ρ = 0.80, P = .006) measured at ~ 3 hours post-ROSC were positively associated with neurologic outcome scores at 24 hours. These findings shed light on brain physiological changes following CA, and suggest that MRI measures of brain perfusion and metabolism may provide a potential biomarker to guide post-CA management.

Rationale and Strategies for Development of an Optimal Bundle of Management for Cardiac Arrest

Objectives

To construct a highly detailed yet practical, attainable roadmap for enhancing the likelihood of neurologically intact survival following sudden cardiac arrest.

Design Setting and Patients

Population-based outcomes following out-of-hospital cardiac arrest were collated for 10 U.S. counties in Alaska, California, Florida, Ohio, Minnesota, Utah, and Washington. The 10 identified emergency medical services systems were those that had recently reported significant improvements in neurologically intact survival after introducing a more comprehensive approach involving citizens, hospitals, and evolving strategies for incorporating technology-based, highly choreographed care and training. Detailed inventories of in-common elements were collated from the ten 9-1-1 agencies and assimilated. For reference, combined averaged outcomes for out-of-hospital cardiac arrest occurring January 1, 2017, to February 28, 2018, were compared with concurrent U.S. outcomes reported by the well-established Cardiac Arrest Registry to Enhance Survival.

Interventions

Most commonly, interventions and components from the ten 9-1-1 systems consistently included extensive public cardiopulmonary resuscitation training, 9-1-1 system-connected smart phone applications, expedited dispatcher procedures, cardiopulmonary resuscitation quality monitoring, mechanical cardiopulmonary resuscitation, devices for enhancing negative intrathoracic pressure regulation, extracorporeal membrane oxygenation protocols, body temperature management procedures, rapid cardiac angiography, and intensive involvement of medical directors, operational and quality assurance officers, and training staff.

Measurements and Main Results

Compared with Cardiac Arrest Registry to Enhance Survival (n = 78,704), the cohorts from the 10 emergency medical services agencies examined (n = 2,911) demonstrated significantly increased likelihoods of return of spontaneous circulation (mean 37.4% vs 31.5%; p < 0.001) and neurologically favorable hospital discharge, particularly after witnessed collapses involving bystander cardiopulmonary resuscitation and shockable cardiac rhythms (mean 10.7% vs 8.4%; p < 0.001; and 41.6% vs 29.2%; p < 0.001, respectively).

Conclusions

The likelihood of neurologically favorable survival following out-of-hospital cardiac arrest can improve substantially in communities that conscientiously and meticulously introduce a well-sequenced, highly choreographed, system-wide portfolio of both traditional and nonconventional approaches to training, technologies, and physiologic management. The commonalities found in the analyzed systems create a compelling case that other communities can also improve out-of-hospital cardiac arrest outcomes significantly by conscientiously exploring and adopting similar bundles of system organization and care.

Consistency and variability in human performance during simulate infant CPR: a reliability study

Background

Positive outcomes from infant cardiac arrest depend on the effective delivery of resuscitation techniques, including good quality infant cardiopulmonary resuscitation (iCPR) However, it has been established that iCPR skills decay within weeks or months after training. It is not known if the change in performance should be considered true change or inconsistent performance. The aim of this study was to investigate consistency and variability in human performance during iCPR.

Methods

An experimental, prospective, observational study conducted within a university setting with 27 healthcare students (mean (SD) age 32.6 (11.6) years, 74.1% female). On completion of paediatric basic life support (BLS) training, participants performed three trials of 2-min iCPR on a modified infant manikin on two occasions (immediately after training and after 1 week), where performance data were captured. Main outcome measures were within-day and between-day repeated measures reliability estimates, determined using Intraclass Correlation Coefficients (ICCs), Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC_95%) for chest compression rate, chest compression depth, residual leaning and duty cycle along with the conversion of these into quality indices according to international guidelines.

Results

A high degree of reliability was found for within-day and between-day for each variable with good to excellent ICCs and narrow confidence intervals. SEM values were low, demonstrating excellent consistency in repeated performance. Within-day MDC values were low for chest compression depth and chest compression rate (6 and 9%) and higher for duty cycle (15%) and residual leaning (22%). Between-day MDC values were low for chest compression depth and chest compression rate (3 and 7%) and higher for duty cycle (21%) and residual leaning (22%). Reliability reduced when metrics were transformed in quality indices.

Conclusion

iCPR skills are highly repeatable and consistent, demonstrating that changes in performance after training can be considered skill decay. However, when the metrics are transformed in quality indices, large changes are required to be confident of real change.

CPR Compression Rotation Every One Minute Versus Two Minutes: A Randomized Cross-Over Manikin Study

Background

The current basic life support guidelines recommend two-minute shifts for providing chest compressions when two rescuers are performing cardiopulmonary resuscitation. However, various studies have found that rescuer fatigue can occur within one minute, coupled with a decay in the quality of chest compressions. Our aim was to compare chest compression quality metrics and rescuer fatigue between alternating rescuers in performing one- and two-minute chest compressions.

Methods

This prospective randomized cross-over study was conducted at Songklanagarind Hospital, Hat Yai, Songkhla, Thailand. We enrolled sixth-year medical students and residents and randomly grouped them into pairs to perform 8 minutes of chest compression, utilizing both the one-minute and two-minute scenarios on a manikin. The primary end points were chest compression depth and rate. The secondary end points included rescuers' fatigue, respiratory rate, and heart rate.

Results

One hundred four participants were recruited. Compared with participants in the two-minute group, participants in the one-minute group had significantly higher mean (standard deviation, SD) compression depth (mm) (45.8 (7.2) vs. 44.5 (7.1), P=0.01) but there was no difference in the mean (SD) rate (compressions per min) (116.1 (12.5) vs. 117.8 (12.4), P=0.08), respectively. The rescuers in the one-minute group had significantly less fatigue (P < 0.001) and change in respiratory rate (P < 0.001), but there was no difference in the change of heart rate (P=0.59) between the two groups.

Conclusion

There were a significantly higher compression depth and lower rescuer fatigue in the 1-minute chest compression group compared with the 2-minute group. This trial is registered with TCTR20170823001.

Randomised simulation trial found an association between rescuers' height and weight and chest compression quality during paediatric resuscitation

AIM

Our aim was to examine the relationship between rescuers' anthropometric data and chest compression quality during paediatric resuscitation training.

METHODS

This study focused on 224 medical students (53% women) who performed 2 minutes of paediatric resuscitation at the Medical University of Vienna, Austria: 116 on a baby manikin and 108 on an adolescent manikin. Skill Reporter software measured chest compression quality by recording compression depth, frequency, hand position and complete recoil. The participants' height, weight and body mass index (BMI) were recorded.

RESULTS

Participants with a lower BMI achieved higher total chest compression scores on both the baby and adolescent manikins than participants with a higher BMI. The latter were more likely to exceed the correct compression depth and not achieve complete chest recoil in the adolescent manikin. When it came to the baby manikin, the female participants achieved better chest recoil and the males achieved a higher number of compressions at the correct rate. Males also achieved better chest recoil with the adolescent manikins. Being tall only correlated with incomplete recoil in the adolescent manikin.

CONCLUSION

The results indicate that anthropometric variables were associated with chest compression quality in paediatric patients and should be considered by future education programmes.

Should chest compressions be considered an aerosol-generating procedure? A literature review in response to recent guidelines on personal protective equipment for patients with suspected COVID-19

There is disagreement between international guidelines on the level of personal protective equipment (PPE) required for chest compressions for patients with suspected COVID-19. This discrepancy centres on whether they are considered to be an aerosol-generating procedure (AGP), thus requiring airborne protection to prevent transmission to healthcare workers (HCWs). The need to don higher-level PPE has to be weighed against the resulting delay to emergency treatment.We performed a literature search on this topic which found eight relevant studies. All were observational with low patient numbers and multiple confounding factors, but describe cases of acute respiratory infection transmission during chest compressions. One systematic review concluded that chest compressions were not an AGP. Two simulated studies (released as preprints) potentially demonstrate aerosol generation. Given that there is evidence for infection transmission during chest compressions, we conclude that a precautionary approach with appropriate PPE is necessary to protect HCW from contracting a potentially fatal infection.

The effect of positive end-expiratory pressure on cardiac output and oxygen delivery during cardiopulmonary resuscitation

Background

Positive end-expiratory pressure (PEEP) is used to optimize oxygenation by preventing alveolar collapse. However, PEEP can potentially decrease cardiac output through cardiopulmonary interactions. The effect of PEEP on cardiac output during cardiopulmonary resuscitation (CPR) is not known.

Methods

This was a preclinical randomized, controlled, animal study conducted in an animal research facility on 25 Landrace-Yorkshire pigs. After inducing cardiac arrest, CPR was performed with LUCAS 3. During CPR, pigs were ventilated at a PEEP of 0, 5, 10, 15, 20 cmH₂O (randomly determined via lottery) for 9 min. Cardiac output, obtained via ultrasound dilution, and PaO₂ were measured, and oxygen delivery calculated for each PEEP.

Results

A mixed-effects repeated-measures analysis of variance was used to compare the baseline value adjusted mean cardiac output, PaO₂, and oxygen delivery between PEEP groups. Least significant difference test was used to conduct pairwise comparisons between PEEP groups. To determine optimum PEEP, Gaussian mixture model was applied to the adjusted means of cardiac output and oxygen delivery. Increasing PEEP to 10 and higher resulted in significant declines in cardiac output. A PEEP of 15 and higher resulted in significant declines in oxygen delivery. As PEEP was increased from 0 to 20, PaO₂ increased significantly. Gaussian mixture model identified the 0–5 PEEP group as providing optimal cardiac output and oxygen delivery, with PEEP of 5 providing the highest oxygen delivery.

Conclusions

A PEEP of 0–5 resulted in the optimal oxygen delivery and cardiac output during CPR, with PEEP of 5 resulting in higher oxygen delivery, and a slightly lower, statistically insignificant cardiac output than PEEP of 0.

In-Depth Extracorporeal Cardiopulmonary Resuscitation in Adult Out-of-Hospital Cardiac Arrest

The use of extracorporeal cardiopulmonary resuscitation (E‐CPR) for the treatment of patients with out‐of‐hospital cardiac arrest who do not respond to conventional cardiopulmonary resuscitation CPR) has increased significantly in the past 10 years, in response to case reports and observational studies reporting encouraging results. However, no randomized controlled trials comparing E‐CPR with conventional CPR have been published to date. The evidence from systematic reviews of the available observational studies is conflicting. The inclusion criteria for published E‐CPR studies are variable, but most commonly include witnessed arrest, immediate bystander CPR, an initial shockable rhythm, and an estimated time from CPR start to establishment of E‐CPR (low‐flow time) of <60 minutes. A shorter low‐flow time has been consistently associated with improved survival. In an effort to reduce low‐flow times, commencement of E‐CPR in the prehospital setting has been reported and is currently under investigation. The provision of an E‐CPR service, whether hospital based or prehospital, carries considerable cost and technical challenges. Despite increased adoption, many questions remain as to which patients will derive the most benefit from E‐CPR, when and where to implement E‐CPR, optimal post‐arrest E‐CPR care, and whether this complex invasive intervention is cost‐effective. Results of ongoing trials are awaited to determine whether E‐CPR improves survival when compared with conventional CPR.

Impact of dispatcher assisted CPR on ROSC rates: A National Cohort Study

INTRODUCTION

Out of hospital cardiac arrest (OHCA) is a leading cause of mortality. Bystander CPR is associated with increased OHCA survival rates. Dispatcher assisted CPR (DA-CPR) increases rates of bystander CPR, shockable rhythm prevalence, and improves ROSC rates. The aim of this article was to quantify and qualify DA-CPR (acceptance/rejection), ROSC, shockable rhythms, and associations between factors as seen in MDA, Israel, during 2018.

METHODS

All 2018 OHCA incidents in Israel's national EMS database were studied retrospectively. We identified rates and reasons for DA-CPR acceptance or rejection. Reasons DA-CPR was rejected/non-feasible by caller were categorized into 5 groups. ROSC was the primary outcome. We created two study groups: 1) No DA-CPR (n = 542). 2) DA-CPR & team CPR (n = 1768).

RESULTS

DA-CPR was accepted by caller 76.5% of incidents. In group 1, ROSC rates were significantly lower compared to patients in group 2 (12.4% vs. 21.3% p < .001). Group 1 had 12.4% shockable rhythms vs. 17.1% in group 2 (DA-CPR and team CPR). Of the total 369 shockable cases, 42.3% (156) achieved ROSC, in the non-shockable rhythms only 14.8% achieved ROSC.

CONCLUSIONS

OHCA victims receiving dispatcher assisted bystander CPR have higher rates of ROSC and more prevalence of shockable rhythms. MDA dispatchers offer DA-CPR and it is accepted 76.5% of the time. MDA patients receiving DA-CPR had higher ROSC rates and more shockable rhythms. MDA's age demographic is high, possibly affecting ROSC and shockable rhythm rates.

"Six-dial Strategy"-Mechanical Ventilation during Cardiopulmonary Resuscitation

As per current guidelines, whenever an advanced airway is in place during cardiopulmonary resuscitation, positive pressure ventilation should be provided without pausing for chest compression. Positive pressure ventilation can be provided through bag-valve resuscitator (BV) or mechanical ventilator (MV), which was found to be equally efficacious. In a busy emergency department, with less trained personnel use of MV is advantageous over BV in terms of reducing human errors and relieving the airway manager to focus on other resuscitation tasks. Currently, there are no guidelines specific to MV settings in cardiac arrest. We present a concept of "six-dial ventilator strategy during CPR" that encompasses the evidence-based settings appropriate during chest compression. We suggest use of volume control ventilation with the following settings: (1) positive end-expiratory pressure of 0 cm of water (to allow venous return), (2) tidal volume of 8 mL/kg with fraction of inspired oxygen at 100% (for adequate oxygenation), (3) respiratory rate of 10 per minute (for adequate ventilation), (4) maximum peak inspiratory pressure or P _max alarm of 60 cm of water (to allow tidal volume delivery during chest compression), (5) switching OFF trigger (to avoid trigger by chest recoil), and (6) inspiratory to expiratory time ratio of 1:5 (to provide adequate inspiratory time of 1 second). How to cite this article: Sahu AK, Timilsina G, Mathew R, Jamshed N, Aggarwal P. "Six-dial Strategy"-Mechanical Ventilation during Cardiopulmonary Resuscitation. Indian J Crit Care Med 2020;24(6):487-489.

Multimedia-aided instruction in teaching basic life support to undergraduate nursing students

Basic life support (BLS) knowledge is a necessity for nursing students, as they have to deal with cardiac arrest events during their professional career. Existing studies indicate poor BLS knowledge among health science students, including nursing students. Learning BLS requires an understanding of basic sciences, such as anatomy, physiology, and biochemistry, subjects perceived to be difficult, resulting in misconceptions. Hence, a multimedia-aided instruction on BLS, supplemented with cooperating learning groups, was developed to assist nursing students in gaining correct BLS knowledge. A pretest-posttest designed for single cooperating groups was employed to evaluate students' achievements. Sixty-five undergraduate nursing students took the pretest and posttest that consisted of 10 open-ended questions, each designed to evaluate an aspect of their BLS knowledge. The results show significantly more students (60 vs. 20%) answered more questions correctly on the posttest compared with the pretest (P value <0.05, Wilcoxon signed-rank test). Thus the multimedia-aided instruction package enhanced undergraduate nursing students' understanding of BLS and also assisted to generate a positive perception of multimedia-aided instructions, supplemented with a cooperating learning group.

The effects of thoracic cage dimension and chest subcutaneous adipose tissue on outcomes of adults with in-hospital cardiac arrest: A retrospective study

BACKGROUND

The associations between thoracic cage dimension, chest subcutaneous adipose tissue (SAT) depth and outcomes of adults with in-hospital cardiac arrest (IHCA) remain unknown.

METHODS

We retrospectively evaluated IHCA patients between January 2016 and October 2017. The thoracic cage transverse diameter, internal AP diameter, cross-sectional area, anterior and posterior SAT depths were measured in computed-tomography (CT) images. Using logistic regression models, we determined the adjusted associations between thoracic cage dimension, SAT depths and the prognosis for IHCA. The primary outcome was sustained return of spontaneous circulation (ROSC) and the secondary outcome was survival to hospital discharge.

RESULTS

Among 423 IHCA patients, 258 patients achieved ROSC and 70 survived to discharge. Smaller cross-sectional area and posterior SAT depth were significantly related to ROSC. Smaller posterior SAT depth was associated with ROSC. After multivariate adjustment, the smaller cross-sectional area was independently associated with ROSC (Odds ratio [OR] 0.99, 95% confidence interval [95%CI] 0.99-1.00; p = 0.008) and survival to discharge (OR 0.99, 95%CI 0.98-1.00; p = 0.024), and the smaller posterior SAT depth was independently related to ROSC (OR 0.65, 95%CI 0.44-0.96; p = 0.030), whereas no relation to survival to discharge was found.

CONCLUSIONS

In adults with IHCA, the smaller thoracic cage dimension and posterior SAT depth are associated with better survival. An adjustable compression depth based on the thoracic cage dimension might be better than the "one-size-fits-all" compression depth for resuscitating CA patients. In addition, physicians should pay extra attention to compression efficacy when resuscitating obese patients.

Personalized physiology-guided resuscitation in highly monitored patients with cardiac arrest-the PERSEUS resuscitation protocol

Resuscitation guidelines remain uniform across all cardiac arrest patients, focusing on the delivery of chest compressions to a standardized rate and depth and algorithmic vasopressor dosing. However, individualizing resuscitation to the appropriate hemodynamic and ventilatory goals rather than a standard "one-size-fits-all" treatment seems a promising new therapeutic strategy. In this article, we present a new physiology-guided treatment strategy to titrate the resuscitation efforts to patient's physiologic response after cardiac arrest. This approach can be applied during resuscitation attempts in highly monitored patients, such as those in the operating room or the intensive care unit, and could serve as a method for improving tissue perfusion and oxygenation while decreasing post-resuscitation adverse effects.

Confirming the Clinical Safety and Feasibility of a Bundled Methodology to Improve Cardiopulmonary Resuscitation Involving a Head-Up/Torso-Up Chest Compression Technique

OBJECTIVES

Combined with devices that enhance venous return out of the brain and into the thorax, preclinical outcomes are improved significantly using a synergistic bundled approach involving mild elevation of the head and chest during cardiopulmonary resuscitation. The objective here was to confirm clinical safety/feasibility of this bundled approach including use of mechanical cardiopulmonary resuscitation provided at a head-up angle.

DESIGN

Quarterly tracking of the frequency of successful resuscitation before, during, and after the clinical introduction of a bundled head-up/torso-up cardiopulmonary resuscitation strategy.

SETTING

9-1-1 response system for a culturally diverse, geographically expansive, populous jurisdiction.

PATIENTS

All 2,322 consecutive out-of-hospital cardiac arrest cases (all presenting cardiac rhythms) were followed over 3.5 years (January 1, 2014, to June 30, 2017).

INTERVENTIONS

In 2014, 9-1-1 crews used LUCAS (Physio-Control Corporation, Redmond, WA) mechanical cardiopulmonary resuscitation and impedance threshold devices for out-of-hospital cardiac arrest. After April 2015, they also 1) applied oxygen but deferred positive pressure ventilation several minutes, 2) solidified a pit-crew approach for rapid LUCAS placement, and 3) subsequently placed the patient in a reverse Trendelenburg position (~20°).

MEASUREMENTS AND MAIN RESULTS

No problems were observed with head-up/torso-up positioning (n = 1,489), but resuscitation rates rose significantly during the transition period (April to June 2015) with an ensuing sustained doubling of those rates over the next 2 years (mean, 34.22%; range, 29.76-39.42%; n = 1,356 vs 17.87%; range, 14.81-20.13%, for 806 patients treated prior to the transition; p < 0.0001). Outcomes improved across all subgroups. Response intervals, clinical presentations and indications for attempting resuscitation remained unchanged. Resuscitation rates in 2015-2017 remained proportional to neurologically intact survival (~35-40%) wherever tracked.

CONCLUSIONS

The head-up/torso-up cardiopulmonary resuscitation bundle was feasible and associated with an immediate, steady rise in resuscitation rates during implementation followed by a sustained doubling of the number of out-of-hospital cardiac arrest patients being resuscitated. These findings make a compelling case that this bundled technique will improve out-of-hospital cardiac arrest outcomes significantly in other clinical evaluations.

Airway and ventilation management during cardiopulmonary resuscitation and after successful resuscitation

After cardiac arrest a combination of basic and advanced airway and ventilation techniques are used during cardiopulmonary resuscitation (CPR) and after a return of spontaneous circulation (ROSC). The optimal combination of airway techniques, oxygenation and ventilation is uncertain. Current guidelines are based predominantly on evidence from observational studies and expert consensus; recent and ongoing randomised controlled trials should provide further information. This narrative review describes the current evidence, including the relative roles of basic and advanced (supraglottic airways and tracheal intubation) airways, oxygenation and ventilation targets during CPR and after ROSC in adults. Current evidence supports a stepwise approach to airway management based on patient factors, rescuer skills and the stage of resuscitation. During CPR, rescuers should provide the maximum feasible inspired oxygen and use waveform capnography once an advanced airway is in place. After ROSC, rescuers should titrate inspired oxygen and ventilation to achieve normal oxygen and carbon dioxide targets.

Supraglottic airway device placement by respiratory therapists

OBJECTIVE

Respiratory Therapists (RTs) are some of the first staff to arrive at in-hospital incidents where cardiopulmonary resuscitation (CPR) is needed, yet at some facilities, their ability to intubate is limited by hospital scope of practice. During the intubation process, CPR is often interrupted which could potentially increase the likelihood of adverse patient outcomes. Training RTs to secure the airway using non-intubation methods may reduce or eliminate time for CPR interruptions and allow for earlier continuous/uninterrupted chest compressions.

DESIGN

A pilot study was developed to assess the effectiveness of a new policy for RT scope of practice.

METHODS

RTs were trained for supraglottic airway device placement prior to procedure initiation. After each device insertion event, RTs completed a written survey. Time between cardiac arrest and device insertion, number of insertion attempts, ease of placement, technical specifications of the device, complications, and survival were compiled and compared between supraglottic airway device and endotracheal tube (ETT) placement.

RESULTS

Procedural information from 23 patients who received a supraglottic airway device during the trial was compared to retrospective data of CPR events requiring intubation from the previous year. Time between initiation of cardiac arrest and advanced airway placement decreased significantly (p < 0.0001) when RTs placed the supraglottic airway device (4.7 min) versus ETT at CPR events the previous year (8.6 min). Device-associated complications were minimal and patient mortality was the same regardless of device.

CONCLUSION

We propose that more RTs should be trained to insert supraglottic airway devices during inpatient CPR events.

A new method for the performance of external chest compressions during hypogravity simulation

INTRODUCTION

2015 UK resuscitation guidelines aim for 50-60 mm depth when giving external chest compressions (ECCs). This is achievable in hypogravity if the rescuer flexes and extends their arms during CPR, or using a new method trialed; the 'Mackaill-Russomano' (MR CPR) method.

METHODS

10 participants performed 3 sets of 30 ECCs in accordance with 2015 guidelines. A control was used at 1Gz, with eight further conditions using Mars and Moon simulations, with and without braces in the terrestrial position and using the MR CPR method. The MR CPR method involved straddling the mannequin, using its legs for stabilization. A body suspension device, with counterweights, simulated hypogravity environments. ECC depth, rate, angle of arm flexion and heart rate (HR) were measured.

RESULTS

Participants completed all conditions, and ECC rate was achieved throughout. Mean (± SD) ECC depth using the MR CPR method at 0.38Gz was 54.1 ± 0.55 mm with braces; 50.5 ± 1.7 mm without. ECCs were below 50 mm at 0.17Gz using the MR CPR method (47.5 ± 1.47 mm with braces; 47.4 ± 0.87 mm without). In the terrestrial position, ECCs were more effective without braces (49.4 ± 0.26 mm at 0.38Gz; 43.9 ± 0.87 mm at 0.17Gz) than with braces (48.5 ± 0.28 mm at 0.38Gz; 42.4 ± 0.3 mm at 0.17Gz). Flexion increased from approximately 2° - 8° with and without braces respectively. HR did not change significantly from control.

DISCUSSION

2015 guidelines were achieved using the MR CPR method at 0.38Gz, with no significant difference with and without braces. Participants were closer to achieving the required ECC depth in the terrestrial position without braces. ECC depth was not achieved at 0.17Gz, due to a greater reduction in effective body weight.

Morbid obesity impairs adequacy of thoracic compressions in a simulation-based model

Adequate cardiopulmonary resuscitation is an important predictor of survival, however, obesity provides a significant physical barrier to thoracic compressions. This study explores the effect of morbid obesity on compression adequacy. We performed a prospective randomised controlled crossover study, assessing the adequacy of thoracic compressions on a manikin modified to emulate a morbidly obese patient. Participants recruited from critical care departments were randomised to perform continuous compressions for two minutes on each manikin. Accelerometers were used to measure thoracic wall movement. The primary endpoint was a composite measure of compression adequacy (rate, depth and recoil). Secondary endpoints were the individual components of the composite outcome and measures of perceived effectiveness, fatigue, and pain. One hundred and one participants were recruited. There was a significant difference between the obese and control groups in the composite endpoint (4% versus 30%, <i>P</i> <0.001), as well as the individual components of adequacy (<i>P</i> <0.01 for all). Quartile data showed significant deterioration in adequacy of depth and recoil in both groups, and this occurred significantly earlier in the obese group (<i>P</i> ≤0.001). Participants' perception of effectiveness was significantly lower (<i>P</i> ≤0.001) in the obese group, and levels of fatigue (<i>P</i> ≤0.001) and pain (<i>P</i> ≤0.001) significantly higher. Morbid obesity impairs the adequacy of thoracic compressions for trained rescuers in a simulation-based model. Participants were not fully aware of how ineffective compressions were. There is evidence of earlier fatigue further reducing effectiveness. These findings have significant implications for the training of rescuers in a clinically relevant population and the planning of future research.

Correlation of end tidal carbon dioxide, amplitude spectrum area, and coronary perfusion pressure in a porcine model of cardiac arrest

Amplitude Spectrum Area (AMSA) values during ventricular fibrillation (VF) correlate with myocardial energy stores and predict defibrillation success. By contrast, end tidal CO₂ (ETCO2) values provide a noninvasive assessment of coronary perfusion pressure and myocardial perfusion during cardiopulmonary resuscitation (CPR). Given the importance of the timing of defibrillation shock delivery on clinical outcome, we tested the hypothesis that AMSA and ETCO2 correlate with each other and can be used interchangably to correlate with myocardial perfusion in an animal laboratory preclinical, randomized, prospective investigation. After 6 min of untreated VF, 12 female pigs (32 ± 1 Kg), isoflurane anesthetized pigs received sequentially 3 min periods of standard (S) CPR, S‐CPR+ an impedance threshold device (ITD), and then active compression decompression (ACD) + ITD CPR. Hemodynamic, AMSA, and ETCO2 measurements were made with each method of CPR. The Spearman correlation and Friedman tests were used to compare hemodynamic parameters. ETCO2, AMSA, coronary perfusion pressure, cerebral perfusion pressure were lowest with STD CPR, increased with STD CPR + ITD and highest with ACD CPR + ITD. Further analysis demonstrated a positive correlation between AMSA and ETCO2 (r = 0.37, P = 0.025) and between AMSA and key hemodynamic parameters (P < 0.05). This study established a moderate positive correlation between ETCO2 and AMSA. These findings provide the physiological basis for developing and testing a novel noninvasive method that utilizes either ETCO2 alone or the combination of ETCO2 and AMSA to predict when defibrillation might be successful.

European cardiovascular nurses’ and allied professionals’ knowledge and practical skills regarding cardiopulmonary resuscitation

Purpose:

Cardiopulmonary resuscitation (CPR) remains a cornerstone in the treatment of cardiac arrest, and is directly linked to survival rates. Nurses are often first responders and need to be skilled in the performance of cardiopulmonary resuscitation. As cardiopulmonary resuscitation skills deteriorate rapidly, the purpose of this study was to investigate whether there was an association between participants’ cardiopulmonary resuscitation training and their practical cardiopulmonary resuscitation test results.

Methods:

This comparative study was conducted at the 2014 EuroHeartCare meeting in Stavanger ( n=133) and the 2008 Spring Meeting on Cardiovascular Nursing in Malmö ( n=85). Participants performed cardiopulmonary resuscitation for three consecutive minutes CPR training manikins from Laerdal Medical®. Data were collected with a questionnaire on demographics and participants’ level of cardiopulmonary resuscitation training.

Results:

Most participants were female (78%) nurses (91%) from Nordic countries (77%), whose main role was in nursing practice (63%), and 71% had more than 11 years’ experience ( n=218). Participants who conducted cardiopulmonary resuscitation training once a year or more ( n=154) performed better regarding ventilation volume than those who trained less (859 ml vs. 1111 ml, p=0.002). Those who had cardiopulmonary resuscitation training offered at their workplace ( n=161) also performed better regarding ventilation volume (889 ml vs. 1081 ml, p=0.003) and compression rate per minute (100 vs. 91, p=0.04) than those who had not.

Conclusion:

Our study indicates a positive association between participants’ performance on the practical cardiopulmonary resuscitation test and the frequency of cardiopulmonary resuscitation training and whether cardiopulmonary resuscitation training was offered in the workplace. Large ventilation volumes were the most common error at both measuring points.

Hemodynamically Directed Two-Person Chest Compressions: A Case Report

Cardiopulmonary resuscitation has a low success rate both in and out of the hospital setting. Return of spontaneous circulation, however, is considerably higher for intraoperative cardiac arrests. Chest compressions remain of utmost importance. Optimal chest compression depth is believed to be greater than 5 cm. However, this depth is often not achieved. We describe a case in which the adequacy of chest compressions, based on hemodynamic monitoring, was achieved with 2 persons simultaneously providing a compressive force. This hemodynamic-directed care resulted in return of spontaneous circulation on 2 separate occasions.

Body mass index and thoracic subcutaneous adipose tissue depth: possible implications for adequacy of chest compressions

Objective

Adequacy of cardiopulmonary resuscitation relies on compression of the thoracic cage to produce changes in intra-thoracic pressures sufficient to generate a pressure gradient. In order to evaluate the efficacy of cardiopulmonary resuscitation in morbid obesity, it is first necessary to determine the depth of thoracic subcutaneous adipose tissue (SAT) and to correlate this with body mass index (BMI).

Results

Computerised-tomography images of the thorax of 55 patients with a diagnosis of obesity or morbid obesity (mean BMI 45.95 kg/m²) were evaluated to determine the depth of SAT at the level at which chest compressions would be applied by a trained rescuer, and correlated with BMI. Mean anterior SAT was 36.53 mm, and mean posterior SAT was 50.73 mm. There was a significant correlation between BMI and anterior and posterior SAT for males (p < 0.05 for both), and females (p < 0.05 for both). The slope of the functions was considered sufficiently close to allow combining the data. This also showed a significant correlation between SAT and BMI (p < 0.01 for both). Both anterior and posterior SAT is correlated with BMI. This data allows development of a model to explore the efficacy of chest compressions in morbid obesity.

Electronic supplementary material

The online version of this article (10.1186/s13104-017-2918-9) contains supplementary material, which is available to authorized users.

Ideal (i) CPR: Looking beyond shadows in a cave

Survival rates after cardiac arrest have shown minimal improvement in the last 60 years. However, in some forward-thinking cities and hospitals, out-of and in-hospital cardiac arrest survival rates exceed 20% and 40% respectively. These beacons of hope can enlighten us, providing a clearer vision of what it takes to provide Ideal cardiopulmonary resuscitation. To make progress in a field that has seemingly stagnated for too many decades, we must be open to new ideas and develop bundles of care that work in communities with varying EMS systems and various existing infrastructure to bring the best practices to the rest of the country.

Chest compliance is altered by static compression and decompression as revealed by changes in anteroposterior chest height during CPR using the ResQPUMP in a human cadaver model

INTRODUCTION

Chest compliance plays a fundamental role in the generation of circulation during cardiopulmonary resuscitation (CPR). To study potential changes in chest compliance over time, anterior posterior (AP) chest height measurements were performed on newly deceased (never frozen) human cadavers during CPR before and after 5min of automated CPR. We tested the hypothesis that after 5min of CPR chest compliance would be significantly increased.

METHODS

Static compression (30, 40, and 50kg) and decompression forces (-10, -15kg) were applied with a manual ACD-CPR device (ResQPUMP, ZOLL) before and after 5min of automated CPR. Lateral chest x-rays were obtained with multiple reference markers to assess changes in AP distance.

RESULTS

In 9 cadavers, changes (mean±SD) in the AP distance (cm) during the applied forces were 2.1±1.2 for a compression force of 30kg, 2.9±1.3 for 40kg, 4.3±1.0 for 50kg, 1.0±0.8 for a decompression force of -10kg and 1.8±0.6 for -15kg. After 5min of automated CPR, AP excursion distances were significantly greater (p<0.05). AP distance increased to 3.7±1.4 for a compression force of 30kg, 4.9±1.6 for 40kg, 6.3±1.9 for 50kg, 2.3±0.9 for -10kg of lift and 2.7±1.1 for -15kg of lift.

CONCLUSIONS

These data demonstrate chest compliance increases significantly over time as demonstrated by the significant increase in the measured AP distance after 5min of CPR. These findings suggest that adjustments in compression and decompression forces may be needed to optimize CPR over time.

[Interaction between heart and brain in sudden cardiac death]

The heart and brain are constantly interacting under normal physiological conditions. This interaction is under the control of the autonomic nervous system with parasympathetic and sympathetic nerve fibers including the participating brain structures. Pathological conditions, such as epilepsy and ischemic cerebral stroke influence heart function, especially the frequency and may result in severe arrhythmia. An asymmetric influence of the left and right brain hemispheres on the heart rate is still under debate. Conversely, the influence of the heart in cases of acute cardiac arrest on brain function is equally relevant and a common clinical problem after resuscitation. We review the damaging cascade of global cerebral hypoxia and the value of different diagnostic procedures as well as the ethical problem of the point in time of termination of consciousness and the instruments for estimating the prognosis.