Interposed abdominal compression CPR: a comprehensive evidence based review

Physiology-Guided Resuscitation: Monitoring and Augmenting Perfusion during Cardiopulmonary Arrest

Given the high morbidity and mortality associated with cardiopulmonary arrest, there have been multiple trials aimed at better monitoring and augmenting coronary, cerebral, and systemic perfusion. This article aims to elucidate these interventions, first by detailing the physiology of cardiopulmonary resuscitation and the available tools for managing cardiopulmonary arrest, followed by an in-depth examination of the newest advances in the monitoring and delivery of advanced cardiac life support.

A proof-of-concept study evaluating cardiac compression techniques for cardiopulmonary resuscitation in laying hens (Gallus gallus)

OBJECTIVE

To determine in adult chickens which of 3 CPR techniques, sternal compressions (SC), SC with interposed caudal coelomic compressions (ICCC), or lateral compressions (LC), results in the highest mean systolic (SAP), diastolic (DAP), and mean arterial pressure (MAP) as measured directly from the carotid artery.

DESIGN

Prospective, nonblinded, experimental crossover study.

SETTING

University teaching hospital laboratory.

ANIMALS

Ten retired laying hens.

INTERVENTIONS

Birds were sedated, anesthetized, and placed in dorsal recumbency. A carotid artery catheter was placed to directly measure arterial pressure. Ventricular fibrillation was induced with direct cardiac stimulation using a 9-Volt battery. Each bird then received 2 minutes of the 3 different cardiac compression techniques in a random order by 3 different compressors, with the compressor order also randomized. Birds were subsequently administered IV epinephrine, and transthoracic defibrillation was attempted. At the end of experimentation, each bird was euthanized, and simple gross necropsies were performed. Linear mixed models followed by pairwise paired t-tests were performed to evaluate differences in pressures generated by each technique.

MEASUREMENTS AND MAIN RESULTS

The primary study outcomes were SAP, DAP, and MAP over 2 minutes of compressions for each compression technique. Pressures from ICCC (SAP: 27.6 ± 5.3 mm Hg, DAP: 18.7 ± 5.2 mm Hg, MAP: 21.7 ± 5.2 mm Hg) were significantly higher than those from LC (SAP: 18.9 ± 5.4 mm Hg, DAP: 11.6 ± 4.1 mm Hg, MAP: 14.1 ± 4.5 mm Hg). Pressures from SC (SAP: 24.5 ± 6.4 mm Hg, DAP: 15.2 ± 4.3 mm Hg, MAP: 18.3 ± 5.0 mm Hg) were not significantly different from ICCC or LC.

CONCLUSIONS

External compressions can generate detectable increases in arterial pressure in chickens with ventricular fibrillation. SC with ICCC generated significantly higher arterial pressures than LC. SC alone generated blood pressures that were not significantly different from those generated by SC with ICCC or LC.

Evaluation of abdominal compression-decompression combined with chest compression CPR performed by a new device: Is the prognosis improved after this combination CPR technique?

INTRODUCTION

This study was designed to compare the outcomes of standard cardiopulmonary resuscitation (STD-CPR) and combined chest compression and abdominal compression-decompression cardiopulmonary resuscitation (CO-CPR) with a new device following out-of-hospital cardiac arrest (OHCA). Moreover, we investigated whether patient prognosis improved with this combination treatment.

METHODS

This trial was a single-centre, prospective, randomized trial, and a blinded assessment of the outcomes was performed. A total of 297 consecutive patients with OHCA were initially screened, and 278 were randomized to the STD-CPR group (n = 135) or the CO-CPR group (n = 143). We compared the proportions of patients who achieved a return of spontaneous circulation (ROSC), survived to hospital admission and survived to hospital discharge. In addition, we also performed the Kaplan-Meier analysis with a log-rank test at the end of the follow-up period to compare the survival curves of the two groups.

RESULTS

The differences were not statistically significant in the proportion of patients who achieved ROSC [31/135 (23.0%) versus 35/143 (24.5%)] and survived to hospital admission [28/135 (20.7%) versus 33/143 (23.1%)] between the CO-CPR group and STD-CPR group. However, there was a significant difference in the proportion of patients who survived to hospital discharge [16/135 (11.9%) versus 7/143 (4.9%)] between the two groups. Nine patients (6.7%) in the CO-CPR group and 2 patients (1.4%) in the STD group showed good neurological outcomes according to the cerebral performance category (CPC) scale score, and the difference was statistically significant (P = 0.003). The Kaplan-Meier curves showed that the patients in the CO-CPR group achieved better survival benefits than those in the STD-CPR group at the end of the follow-up period (log-rank P = 0.007).

CONCLUSION

CO-CPR was more beneficial than STD-CPR in terms of survival benefits in patients who have suffered out-of-hospital cardiac arrest. Trial registration Chinese Clinical Trial Registry, registered number: ChiCTR2100049581 . Registered 30 July 2021- Retrospectively registered. http://www.medresman.org.cn/uc/index.aspx .

Standard CPR versus interposed abdominal compression CPR in shunted single ventricle patients: comparison using a lumped parameter mathematical model

INTRODUCTION

Cardiopulmonary resuscitation (CPR) in the shunted single-ventricle population is associated with poor outcomes. Interposed abdominal compression-cardiopulmonary resuscitation, or IAC-CPR, is an adjunct to standard CPR in which pressure is applied to the abdomen during the recoil phase of chest compressions.

METHODS

A lumped parameter model that represents heart chambers and blood vessels as resistors and capacitors was used to simulate blood flow in both Blalock-Taussig-Thomas and Sano circulations. For standard CPR, a prescribed external pressure waveform was applied to the heart chambers and great vessels to simulate chest compressions. IAC-CPR was modelled by adding phasic compression pressure to the abdominal aorta. Differential equations for the model were solved by a Runge-Kutta method.

RESULTS

In the Blalock-Taussig-Thomas model, mean pulmonary blood flow during IAC-CPR was 30% higher than during standard CPR; cardiac output increased 21%, diastolic blood pressure 16%, systolic blood pressure 8%, coronary perfusion pressure 17%, and coronary blood flow 17%. In the Sano model, pulmonary blood flow during IAC-CPR increased 150%, whereas cardiac output was improved by 13%, diastolic blood pressure 18%, systolic blood pressure 8%, coronary perfusion pressure 15%, and coronary blood flow 14%.

CONCLUSIONS

In this model, IAC-CPR confers significant advantage over standard CPR with respect to pulmonary blood flow, cardiac output, blood pressure, coronary perfusion pressure, and coronary blood flow. These results support the notion that single-ventricle paediatric patients may benefit from adjunctive resuscitation techniques, and underscores the need for an in-vivo trial of IAC-CPR in children.

Vallecular cyst with coexisting laryngomalacia: Successful diagnosis and laser therapy by flexible endoscopy with a novel noninvasive ventilation support in infants

OBJECTIVE

Vallecular cyst coexisting with laryngomalacia (VC-LM) can cause significant pharyngolaryngeal obstruction. Traditionally, it is diagnosed with flexible endoscopy (FE) and treated by rigid endoscopy. This study evaluates the effectiveness of solely using FE with novel noninvasive ventilation (NIV) of sustained pharyngeal inflation (SPI) support for both diagnosis and treatment in such infants.

METHODS

A retrospective review of consecutive infants who were diagnosed and treated for VC-LM in the 12-year period, 2007 to 2018, was conducted. Clinical variables, techniques, and outcomes were analyzed and reported.

RESULTS

Eighteen infants (10 males) were included. The mean age was 3.0 ± 0.6 months and the mean body weight was 4.6 ± 1.3 kg. Before FE, 14 infants were supported with bi-nasal prongs NIV (BN-NIV) and four infants with tracheal intubation. During diagnostic and therapeutic FE, all infants supported with a nasopharyngeal NIV (NP-NIV) only. All diagnoses were made in the first FE inspection of 3.5 ± 1.2 minutes. Thirteen lesions were immediately treated with FE laser therapy in 18.1 ± 1.7 minutes in the same FE course. Total FE time was 24.6 ± 2.8 minutes. Three infants needed revision laser therapy 4 days later. There was no desaturation (<90%), bradycardia (<100/min), or pneumothorax. After FE therapy, all infants were supported with BN-NIV only with significantly (<0.01) lower pressure and completely weaned off before being discharged 8.4 ± 1.5 days later. All infants, followed up for a 6-month period, showed many clinical improvements.

CONCLUSIONS

FE, with this NP-NIV and SPI supports, could offer accurate diagnosis and successful laser therapy of the VC-LM with procedural sedation in the same session in infants.

A Dynamic Model of Rescuer Parameters for Optimizing Blood Gas Delivery during Cardiopulmonary Resuscitation

Introduction

The quality of cardiopulmonary resuscitation (CPR) has been shown to impact patient outcomes. However, post-CPR morbidity and mortality remain high, and CPR optimization is an area of active research. One approach to optimizing CPR involves establishing reliable CPR performance measures and then modifying CPR parameters, such as compressions and ventilator breaths, to enhance these measures. We aimed to define a reliable CPR performance measure, optimize the CPR performance based on the defined measure and design a dynamically optimized scheme that varies CPR parameters to optimize CPR performance.

Materials and Methods

We selected total blood gas delivery (systemic oxygen delivery and carbon dioxide delivery to the lungs) as an objective function for maximization. CPR parameters were divided into three categories: rescuer dependent, patient dependent, and constant parameters. Two optimization schemes were developed using simulated annealing method: a global optimization scheme and a sequential optimization scheme.

Results and Discussion

Variations of CPR parameters over CPR sequences (cycles) were analyzed. Across all patient groups, the sequential optimization scheme resulted in significant enhancement in the effectiveness of the CPR procedure when compared to the global optimization scheme.

Conclusions

Our study illustrates the potential benefit of considering dynamic changes in rescuer-dependent parameters during CPR in order to improve performance. The advantage of the sequential optimization technique stemmed from its dynamically adapting effect. Our CPR optimization findings suggest that as CPR progresses, the compression to ventilation ratio should decrease, and the sequential optimization technique can potentially improve CPR performance. Validation in vivo is needed before implementing these changes in actual practice.

Evolving Strategies in Cardiac Arrest Management

Cardiac arrest is a leading cause of death in the United States, with a hospital discharge rate of approximately 10%. International resuscitation guidelines offer standardized cardiac arrest management approaches, but beyond the guidelines, are promising innovations to improve resuscitative care. Although clinical data do not yet support the routine use of mechanical chest compressions, corticosteroids, thrombolytics, and adjunctive ventilation devices during arrest, these therapies may have an important role in select patients. Extracorporeal membrane oxygenation during cardiopulmonary resuscitation is a promising advancement and may have survival benefit in select patients. The evidence for standard therapies and these innovations is discussed.

Clinical evaluation of active abdominal lifting and compression CPR in patients with cardiac arrest

BACKGROUND

Chest compression is a standard recommendation during cardiopulmonary resuscitation (CPR). However, chest compression cannot be effectively applied under certain situations, such as chest wall deformity, rib fracture, or hemopneumothorax. An alternative method, abdominal compression, was reported to achieve better resuscitation outcomes in these patients.

MATERIALS AND METHODS

A prospective study was performed in adult patients with cardiac arrest and anticipated ineffective chest compression (thoracic trauma, chest deformity, rib fracture, and hemopneumothorax). Active abdominal lifting and compression cardiopulmonary resuscitation was used. Primary outcome was success rate of restoration of spontaneous circulation (ROSC). Secondary outcomes included heart rate (HR), mean arterial pressure (MAP), pulse oximetry saturation (SpO₂), arterial blood pH value, arterial oxygen pressure (PaO₂), and arterial carbon dioxide tension (PaCO₂), which were measured during the periods of pre-CPR, CPR, and 30min post-ROSC.

RESULTS

A total of 35 patients were enrolled into the study. Five of them had ROSC (14.3%), which was statistically significantly higher than that (0%) reported in the 2015 Advanced Cardiovascular Life Support manual. HR, MAP, and SpO₂ during CPR were also statistically significantly higher during CPR when compared to the period of pre-CPR period (HR 58 versus 0 beats/min, P<0.01; MAP 25 versus 0mm Hg, P<0.01; SpO₂ 0.68 versus 0.48%, P<0.01). In post-ROSC period, HR was statistically significantly higher than that during pre-CPR period (121 versus 0 best/min, P<0.01).

CONCLUSIONS

Active abdominal lifting and compression cardiopulmonary resuscitation could reach better resuscitation outcomes in certain cardiac arrest patients.

Standard versus Abdominal Lifting and Compression CPR

Background. This study compared outcomes of abdominal lifting and compression cardiopulmonary resuscitation (ALP-CPR) with standard CPR (STD-CPR). Materials and Methods. Patients with cardiac arrest seen from April to December 2014 were randomized to receive standard CPR or ALP-CPR performed with a novel abdominal lifting/compression device. The primary outcome was return of spontaneous circulation (ROSC). Results. Patients were randomized to receive ALP-CPR (n = 40) and STD-CPR (n = 43), and the groups had similar baseline characteristics. After CPR, 9 (22.5%) and 7 (16.3%) patients in the ALP-CPR and STD-CPR groups, respectively, obtained ROSC. At 60 minutes after ROSC, 7 (77.8%) and 2 (28.6%) patients, respectively, in the ALP-CPR and STD-CPR groups survived (P = 0.049). Patients in the ALP-CPR group had a significantly higher heart rate and lower mean arterial pressure (MAP) than those in the STD-CPR group (heart rate: 106.8 versus 79.0, P < 0.001; MAP: 60.0 versus 67.3 mm Hg, P = 0.003). The posttreatment PCO₂ was significantly lower in ALP-CPR group than in STD-CPR group (52.33 versus 58.81, P = 0.009). PO₂ was significantly increased after ALP-CPR (45.15 to 60.68, P < 0.001), but it was not changed after STD-CPR. PO₂ after CPR was significantly higher in the ALP-CPR group (60.68 versus 44.47, P < 0.001). There were no differences between genders and for patients who are > 65 or ≤ 65 years of age. Conclusions. The abdominal lifting and compression cardiopulmonary resuscitation device used in this study is associated with a higher survival rate after ROSC than standard CPR.

Combination of chest compressions and interposed abdominal compressions in a swine model of ventricular fibrillation

PURPOSE

The aim of this study was to investigate the effects of the combination of chest compressions and interposed abdominal compressions (IAC-CPR) in a swine model of ventricular fibrillation (VF).

METHODS

Twenty healthy female Landrace-Large White pigs were the study subjects. At the end of the eighth minute of VF, animals in the control group (Group A) received chest compressions at a rate of 100/min, while animals in the experimental group received chest compressions and simultaneous interposed abdominal compressions (CC-IAC - Group B), both at a rate of 100/min. The primary end point of the experiment was return of spontaneous circulation (ROSC). Secondary outcomes were 48-h survival rate and 48-h neurologic outcome.

RESULTS

Six animals (60%) from Group A and 9 animals (90%) from Group B achieved ROSC (P=.121). There was a statistically significant difference in systolic aortic pressure, mean aortic pressure, right atrial pressures, and end-tidal carbon dioxide (ETCO2) between the two groups during the first cycle of CPR, while during the second cycle, diastolic aortic pressure was significantly higher in Group B. Coronary perfusion pressure (CPP) values in group B were significantly higher compared with those in Group A during the first and second cycle of CPR. Neurologic examination was statistically significantly better in Group B (75.00±10.00 vs. 90.00±10.00, P=.037).

CONCLUSION

ROSC did not differ statistically significant in the IAC-CPR compared to the CPR group only, while CPP was significantly higher in IAC-CPR-treated animals.

A tourniquet assisted cardiopulmonary resuscitation augments myocardial perfusion in a porcine model of cardiac arrest

OBJECTIVE

During cardiopulmonary resuscitation (CPR), myocardial blood flow generated by chest compression rarely exceeds 35% of its normal level. Cardiac output generated by chest compression decreases gradually with the prolongation of cardiac arrest and resuscitation. Early studies have demonstrated that myocardial blood flow during CPR is largely dependent on peripheral vascular resistance. In this study, we investigated the effects of chest compression in combination with physical control of peripheral vascular resistance assisted by tourniquets on myocardial blood flow during CPR.

METHODS

Ventricular fibrillation was induced and untreated for 7 min in ten male domestic pigs weighing between 33 and 37 kg. The animals were then randomized to receive CPR alone or a tourniquet assisted CPR (T-CPR). In the CPR alone group, chest compression was performed by a miniaturized mechanical chest compressor. In the T-CPR group, coincident with the start of resuscitation, the thin elastic tourniquets were wrapped around the four limbs from the distal end to the proximal part. After 2 min of CPR, epinephrine (20 μg/kg) was administered via the femoral vein. After 5 min of CPR, defibrillation was attempted by a single 150 J shock. If resuscitation was not successful, CPR was resumed for 2 min before the next defibrillation. The protocol was continued until successful resuscitation or for a total of 15 min. Five minutes after resuscitation, the elastic tourniquets were removed. The resuscitated animals were observed for 2h.

RESULTS

T-CPR generated significantly greater coronary perfusion pressure, end-tidal carbon dioxide and carotid blood flow. There was no difference in both intrathoracic positive and negative pressures between the two groups. All animals were successfully resuscitated with a single shock in both groups. There were no significant changes in hemodynamics observed in the animals treated in the T-CPR group before-and-after the release of tourniquets at post-resuscitation 5 min.

CONCLUSIONS

T-CPR improves myocardial and cerebral perfusion during CPR. It may provide a new and convenient method for augmenting myocardial and cerebral blood flow during CPR.

Is a palpable pulse always restored during cardiopulmonary resuscitation in a patient with a left ventricular assist device?

End-stage heart failure patients are being supported with continuous flow left ventricular assist devices (CF-LVAD) in increasing numbers. The severe physiologic and pharmacologic derangements associated with end-stage heart failure therapies predispose these patients to delirium. During a delirious episode, a patient may inadvertently disconnect CF-LVAD equipment, which may have dangerous consequences. Unfortunately, it is not yet routine to use readily available clinical monitoring tools to allow early detection of delirium in this high-risk population. The authors present a case of acute hyperactive delirium leading to pump power disconnection and cardiopulmonary arrest occurring 7 days after CF-LVAD implantation. The case highlights the need for delirium awareness in the cardiovascular intensive care unit and the unique challenges associated with resuscitation of CF-LVAD patients. The authors propose that cardiovascular intensive care unit patients undergo at least twice daily delirium monitoring and provide a novel resuscitation algorithm for patients who have CF-LVADs.

RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 7: Clinical guidelines

OBJECTIVE

To present a series of evidence-based, consensus guidelines for veterinary CPR in dogs and cats.

DESIGN

Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. Questions in five domains were examined: Preparedness and Prevention, Basic Life Support, Advanced Life Support, Monitoring, and Post-Cardiac Arrest Care. Standardized worksheet templates were used for each question, and the results reviewed by the domain members, by the RECOVER committee, and opened for comments by veterinary professionals for 4 weeks. Clinical guidelines were devised from these findings and again reviewed and commented on by the different entities within RECOVER as well as by veterinary professionals.

SETTING

Academia, referral practice and general practice.

RESULTS

A total of 74 worksheets were prepared to evaluate questions across the five domains. A series of 101 individual clinical guidelines were generated. In addition, a CPR algorithm, resuscitation drug-dosing scheme, and postcardiac arrest care algorithm were developed.

CONCLUSIONS

Although many knowledge gaps were identified, specific clinical guidelines for small animal veterinary CPR were generated from this evidence-based process. Future work is needed to objectively evaluate the effects of these new clinical guidelines on CPR outcome, and to address the knowledge gaps identified through this process.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Heart rate monitored hypothermia and drowning in a 48-year-old man. survival without sequelae: a case report

INTRODUCTION

Victims of severe hypothermia and cardiac arrest may appear dead. They are often unresponsive to on-scene resuscitation including defibrillation while profoundly hypothermic. Several cases of extreme hypothermia and prolonged cardiac arrest with good outcome have been published. We present a case of heart rate monitored (by pulse-watch) hypothermia, prolonged cardiac arrest and survival with complete recovery of neurological functions.

CASE PRESENTATION

On December 22nd 2007 a physically fit, ethnic Norwegian 48-year-old male kayaker set out to paddle alone around an island in a Norwegian fjord. 3 hours 24 min into his trip the kayak capsized in 3.5 degrees C seawater about 500m from the closest shore. The accident was not observed. He managed to call for help using his cellular phone. After a search and rescue operation he was found by our air ambulance helicopter floating, prone, head submerged, with cardiopulmonary arrest and profound hypothermia. He was wearing a personal heart rate monitor/pulse watch. Following extraction, he received cardiopulmonary resuscitation during transport by air ambulance helicopter to hospital. He was warmed on cardiopulmonary bypass from 20.6 degrees C core temperature and return of spontaneous circulation was achieved 3h 27 m after cardiac arrest occurred. After 21 days of intensive care he was discharged from hospital 32 days after his accident. Testing revealed normal cognitive functions one year after the incident. He has returned to his job as an engineer, and has also taken up kayaking again. We provide heart rate and time data leading up to his cardiac arrest.

CONCLUSION

Hypothermia has well established neuro-protective effects in cardiac arrest, as our case also shows. Simple cardiopulmonary resuscitation without use of drugs or defibrillation, should be continued until the patients can be re-warmed, preferably using cardiopulmonary bypass. This approach can be highly effective even in seemingly lost cases.

Heart rate monitored hypothermia and drowning in a 48-year-old man. survival without sequelae: a case report

Introduction

Victims of severe hypothermia and cardiac arrest may appear dead. They are often unresponsive to on-scene resuscitation including defibrillation while profoundly hypothermic. Several cases of extreme hypothermia and prolonged cardiac arrest with good outcome have been published. We present a case of heart rate monitored (by pulse-watch) hypothermia, prolonged cardiac arrest and survival with complete recovery of neurological functions.

Case presentation

On December 22nd 2007 a physically fit, ethnic Norwegian 48-year-old male kayaker set out to paddle alone around an island in a Norwegian fjord. 3 hours 24 min into his trip the kayak capsized in 3.5°C seawater about 500m from the closest shore. The accident was not observed. He managed to call for help using his cellular phone. After a search and rescue operation he was found by our air ambulance helicopter floating, prone, head submerged, with cardiopulmonary arrest and profound hypothermia. He was wearing a personal heart rate monitor/pulse watch. Following extraction, he received cardiopulmonary resuscitation during transport by air ambulance helicopter to hospital. He was warmed on cardiopulmonary bypass from 20.6°C core temperature and return of spontaneous circulation was achieved 3h 27 m after cardiac arrest occurred. After 21 days of intensive care he was discharged from hospital 32 days after his accident. Testing revealed normal cognitive functions one year after the incident. He has returned to his job as an engineer, and has also taken up kayaking again. We provide heart rate and time data leading up to his cardiac arrest.

Conclusion

Hypothermia has well established neuro-protective effects in cardiac arrest, as our case also shows. Simple cardiopulmonary resuscitation without use of drugs or defibrillation, should be continued until the patients can be re-warmed, preferably using cardiopulmonary bypass. This approach can be highly effective even in seemingly lost cases.

The Donders Model of the Circulation in Normo- and Pathophysiology

The solution of some recent as well as of long standing problems, unanswerable due to experimental inaccessibility or moral objections are addressed. In this report, a model of the closed human cardiovascular loop is developed. This model, using one set of 88 equations, allows variations from normal resting conditions to exercise, as well as to the ultimate condition of a circulation following cardiac arrest. The principal purpose of the model is to evaluate the continuum of physiological conditions to cardiopulmonary resuscitation (CPR) effects within the circulation.Within the model, Harvey's view of the circulation has been broadened to include impedance-defined flow as a unifying concept, and as a mechanism in CPR. The model shows that depth of respiration, sympathetic stimulation of cardiac contractile properties and baroreceptor activity can exert powerful influences on the increase in cardiac output, while heart and respiratory rate increases tend to exert an inhibiting influence, with the pressure and flow curves compatible with accepted references. Impedance-defined flow encompasses both positive and negative effects.The model also demonstrates the limitations to cardiopulmonary resuscitation caused by external force applied to intrathoracic structures, with effective cardiac output being limited by collapse and sloshing. Stroke volumes from 6 to 51 ml are demonstrated. It shows that the clinical inclination to apply high pressures to intrathoracic structures may not be rewarded with improved net flow.

Optimal strategy for cardiopulmonary resuscitation with continuous chest compression

OBJECTIVES

To apply the mathematical techniques of optimal control theory (OCT) to a validated model of the human circulation during cardiopulmonary resuscitation (CPR), so as to discover improved waveforms for chest compression and decompression that maximize the coronary perfusion pressure (CPP).

METHODS

The human circulatory system is represented by seven difference equations that describe the pressure changes in systemic vascular compartments that are caused by chest compression. The forcing term is the intrathoracic pressure that is generated by the external chest compression, which is taken as the control variable for the system. The optimum waveform of this forcing pressure as a function of time, determined from OCT, is that which maximizes the calculated CPP between the thoracic aorta and the superior vena cava over a period of 13.3 seconds of continuous chest compression.

RESULTS

The optimal waveform included both compression and decompression of the chest to the maximum allowable extent. Compression-decompression waveforms were rectangular in shape. The frequency of optimal compression-decompression that was found by OCT was 90 per minute. The optimal duty cycle (compression duration per cycle time) was 40%. The CPP for the optimum control waveform was 36 mm Hg vs. 25 mm Hg for standard CPR.

CONCLUSIONS

Optimal control theory suggests that both compression and decompression of the chest are needed for best hemodynamics during CPR.

Design of near-optimal waveforms for chest and abdominal compression and decompression in CPR using computer-simulated evolution

OBJECTIVE

To discover design principles underlying the optimal waveforms for external chest and abdominal compression and decompression during cardiac arrest and cardiopulmonary resuscitation (CPR).

METHOD

A 14-compartment mathematical model of the human cardiopulmonary system is used to test successive generations of randomly mutated external compression waveforms during cardiac arrest and resuscitation. Mutated waveforms that produced superior mean perfusion pressure became parents for the next generation. Selection was based upon either systemic perfusion pressure (SPP = thoracic aortic minus right atrial pressure) or upon coronary perfusion pressure (CPP = thoracic aortic pressure minus myocardial wall pressure). After simulations of 64,414 individual CPR episodes, 40 highly evolved waveforms were characterized in terms of frequency, duty cycle, and phase. A simple, practical compression technique was then designed by combining evolved features with a constant rate of 80 min(-1) and duty cycle of 50%.

RESULTS

All ultimate surviving waveforms included reciprocal compression and decompression of the chest and the abdomen to the maximum allowable extent. The evolved waveforms produced 1.5-3 times the mean perfusion pressure of standard CPR and greater perfusion pressure than other forms of modified CPR reported heretofore, including active compression-decompression (ACD)+ITV and interposed abdominal compression (IAC)-CPR. When SPP was maximized by evolution, the chest compression/abdominal decompression phase was near 70% of cycle time. When CPP was maximized, the abdominal compression/chest decompression phase was near 30% of cycle time. Near-maximal SPP/CPP of 60/21 mmHg (forward flow 3.8 L/min) occurred at a compromise compression frequency of 80 min(-1) and duty cycle for chest compression of 50%.

CONCLUSIONS

Optimized waveforms for thoraco-abdominal compression and decompression include previously discovered features of active decompression and interposed abdominal compression. These waveforms can be used by manual (Lifestick-like) and mechanical (vest-like) devices to achieve short periods of near normal blood perfusion non-invasively during cardiac arrest.

Relative effectiveness of interposed abdominal compression CPR: Sensitivity analysis and recommended compression rates

Interposed abdominal compression, IAC-CPR incorporates alternating chest and abdominal compressions to generate enhanced artificial circulation during cardiac arrest. The technique has been generally successful in improving blood flow and survival compared to standard CPR; however, some questions remain.

OBJECTIVE

To determine "why does IAC-CPR produce more apparent benefit in some subjects than in others?" and "what is the proper compression rate, given that there are actually two compressions (chest and abdomen) in each cycle?"

METHOD

Computer models provide a means to search for subtle effects in complex systems. The present study employs a validated 12-compartment mathematical model of the human circulation to explore the effects upon systemic perfusion pressure of changes in 35 different variables, including vascular resistances, vascular compliances, and rescuer technique. CPR with and without IAC was modeled.

RESULTS AND CONCLUSIONS

Computed results show that the effect of 100 mmHg abdominal compressions on systemic perfusion pressure is relatively constant (about 16 mmHg augmentation). However, the effect of chest compression depends strongly upon chest compression frequency and technique. When chest compression is less effective, as is often true in adults, the addition of IAC produces relatively dramatic augmentation (e.g. from 24 to 40 mmHg). When chest compression is more effective, the apparent augmentation with IAC is relatively less (e.g. from 60 to 76 mmHg). The optimal frequency for uninterrupted IAC-CPR is near 50 complete cycles/min with very little change in efficacy over 20-100 cycles/min. In theory, the modest increase in systemic perfusion pressure produced by IAC can make up in part for poor or ineffective chest compressions in CPR. IAC appears relatively less effective in circumstances when chest pump output is high.