Age-related changes in chest geometry during cardiopulmonary resuscitation

The landscape of paediatric in-hospital cardiac arrest in the United Kingdom National Cardiac Arrest Audit

AIM

To report the patient characteristics and clinical outcome of paediatric in-hospital cardiac arrest in the United Kingdom (UK) National Cardiac Arrest Audit (NCAA) database.

METHODS

Analysis of all recorded paediatric cardiac arrests in the NCAA dataset over a seven-year period ending on 31 December 2018, within acute children's hospitals (including standalone paediatric hospitals and hospitals with tertiary paediatric services) and acute general hospitals participating in NCAA. In this period 1456 patients (with 1580 events), 1 month to 16 years of age, received chest compressions and/or defibrillation and were attended by a hospital-based resuscitation team in response to an emergency call. The main outcome measure was survival to discharge.

RESULTS

For this cohort of paediatric in-hospital cardiac arrest patients the overall rates of sustained return of spontaneous circulation (ROSC) were 69.1% with unadjusted survival to hospital discharge of 54.2%. The presenting rhythm was shockable in 4.3% of events and non-shockable in 82.1% (remainder undetermined); rates of survival to hospital discharge associated with these rhythms were 63.9% and 51.7%. A difference in outcomes was observed between Children's hospitals and acute general hospitals with ROSC rates of 79.1% and 55.5% respectively and survival to hospital discharge rates of 57.7% and 49.3% respectively.

CONCLUSIONS

These first results from the NCAA database describing the outcome of paediatric in-hospital cardiac arrest in UK hospitals will serve as a benchmark from which to assess the future impact of changes in service delivery, organisation and treatment for in-hospital cardiac arrest in young people. Outcomes for specialist paediatric centres should be studied further as higher rates of ROSC and survival to hospital discharge were observed.

Open-chest cardiopulmonary resuscitation versus closed-chest cardiopulmonary resuscitation in patients with cardiac arrest: a systematic review and meta-analysis

Background

Cardiopulmonary resuscitation is the most urgent and critical step in the rescue of patients with cardiac arrest. However, only about 10% of patients with out-of-hospital cardiac arrest survive to discharge. Surprisingly, there is growing evidence that open-chest cardiopulmonary resuscitation is superior to closed-chest cardiopulmonary resuscitation. Meanwhile, The Western Trauma Association and The European Resuscitation Council encouraged thoracotomy in certain circumstances for trauma patients. But whether open-chest cardiopulmonary resuscitation is superior to closed-chest cardiopulmonary resuscitation remains undetermined. Therefore, the aim of this study was to summarize current studies on open-chest cardiopulmonary resuscitation in a systematic review, comparing it to closed-chest cardiopulmonary resuscitation, in a meta-analysis.

Methods

In this systematic review and meta-analysis, we searched the PubMed, EmBase, Web of Science, and Cochrane Library databases from inception to May 2019 investigating the effect of open-chest cardiopulmonary resuscitation and closed-chest cardiopulmonary resuscitation in patients with cardiac arrest, without language restrictions. Statistical analysis was performed using Stata 12.0 software. The primary outcome was return of spontaneous circulation. The secondary outcome was survival to discharge.

Results

Seven observational studies were eligible for inclusion in this meta-analysis involving 8548 patients. No comparative randomized clinical trial was reported in the literature. There was no significant difference in return of spontaneous circulation and survival to discharge between open-chest cardiopulmonary resuscitation and closed-chest cardiopulmonary resuscitation in cardiac arrest patients. The odds ratio (OR) were 0.92 (95%CI 0.36–2.31, P > 0.05) and 0.54 (95%CI 0.17–1.78, P > 0.05) for return of spontaneous circulation and survival to discharge, respectively. Subgroup analysis of cardiac arrest patients with trauma showed that closed-chest cardiopulmonary resuscitation was associated with higher return of spontaneous circulation compared with open-chest cardiopulmonary resuscitation (OR = 0.59 95%CI 0.37–0.94, P < 0.05). And subgroup analysis of cardiac arrest patients with non-trauma showed that open-chest cardiopulmonary resuscitation was associated with higher ROSC compared with closed-chest cardiopulmonary resuscitation (OR = 3.12 95%CI 1.23–7.91, P < 0.05).

Conclusions

In conclusion, for patients with cardiac arrest, we should implement closed-chest cardiopulmonary resuscitation as soon as possible. However, for cardiac arrest patients with chest trauma who cannot perform closed-chest cardiopulmonary resuscitation, open-chest cardiopulmonary resuscitation should be implemented as soon as possible.

Chest compression release velocity factors during out-of-hospital cardiac resuscitation

BACKGROUND

Higher chest compression release velocity (CCRV) has been associated with better outcomes after out-of-hospital cardiac arrest (OHCA), and patient factors have been associated with variations in chest wall compliance and compressibility. We evaluated whether patient sex, age, weight, and time in resuscitation were associated with CCRV during pre-hospital resuscitation from OHCA.

METHODS

Observational study of prospectively collected OHCA quality improvement data in two suburban EMS agencies in Arizona between 10/1/2008 and 12/31/2016. Subject-level mean CCRV during the first 10 min of compressions was correlated with categorical variables by the Wilcoxon rank-sum test and with continuous variables by the Spearman's rank correlation coefficient. Generalized estimating equation and linear mixed-effect models were used to study the trend of CCRV over time.

RESULTS

During the study period, 2535 adult OHCA cases were treated. After exclusion criteria, 1140 cases remained for analysis. Median duration of recorded compressions was 8.70 min during the first 10 min of CPR. An overall decline in CCRV was observed even after adjusting for compression depth. The subject-level mean CCRV was higher for minutes 0-5 than for minutes 5-10 (mean 347.9 mm/s vs. 339.0 mm/s, 95% CI of the difference -12.4 to -5.4, p < 0.0001). Males exhibited a greater mean CCRV compared to females [344.4 mm/s (IQR 307.3-384.6) vs. 331.5 mm/s (IQR 285.3-385.5), p = 0.013]. Mean CCRV was negatively correlated with age and positively correlated with patient weight.

CONCLUSION

CCRV declines significantly over the course of resuscitation. Patient characteristics including male sex, younger age, and increased weight were associated with a higher CCRV.

Thoracic cage volume and dimension assessment by optoelectronic molding in normal children and adolescents during growth

PURPOSE

The thoracic spine, the chondral and osseous ribs, and the sternum together make up the thoracic cage. These elements are strictly correlated, although their growth is not synchronous. The purpose of this study is to provide a comprehensive data set of thoracic dimensions and non-invasive volumetric assessment in a large cohort of males and females from early childhood to young adult age.

METHODS

In all, 622 healthy individuals (406 girls, 216 boys) aged 6-18 years were consecutively enrolled between 2006 and 2016. All had to be healthy with no history of spinal deformity, or any lung, cardiovascular, systemic or neuromuscular disease. The optical ORTEN system for trunk surface data acquisition was used to calculate thoracic cage volume (V) and perimeter (Pe), anterior-posterior depth (AP) and transverse diameter (TD), AP/TD ratio, sternal length (St), and T1-T12 distance (Tle) in all patients.

RESULTS

The overall average age was 11.1 ± 2.5 years (4-18) for girls and 11.0 ± 3.1 years (4-18) for boys. Average growth parameters were: standing height 146.2 ± 14.6 cm (103-172) for girls and 146.4 ± 20.0 cm (94-192) for boys, sitting height 75.4 ± 8.6 cm (61-91) for girls and 75.5 ± 10.3 cm (60-99) for boys, weight 37.6 ± 10.4 kg (16-65) for girls and 38.3 ± 14.3 kg (13.7-104) for boys, BMI 16.7 ± 3.7 (18.5-26) for girls and 17.0 ± 3.3 (18.7-34.3) for boys. At age 6-8 years: V was 52.5% of its final size in girls and 44.9% in boys; Pe was 80.2% its final length in girls and 76.8% in boys; St reached 68% of its final size in girls and 66.9% in boys; Tle reached 73.3% of its final length in girls and 71.2% in boys. At skeletal maturity, thoracic cage volume in boys was 19.4% greater than in girls (p < 0.05). AP/TD ratio remained < 1 in all age groups and did not differ between genders (p > 0.05).

CONCLUSION

Growth of the thoracic cage is shown to be a gradual process that is more linear than previously reported. Only small increases in annual growth rates were observed during the pubertal growth spurt. The most important events characterizing thoracic cage development occurred during the first few years of postnatal growth. The circular cross-section of the very young child's thorax reached adult-like proportions together with its ovoid shape before age 6 years.

Quantification of ventilation volumes produced by compressions during emergency department cardiopulmonary resuscitation

BACKGROUND

Clinical investigations have shown improved outcomes with primary compression cardiopulmonary resuscitation strategies. It is unclear whether this is a result of passive ventilation via chest compressions, a low requirement for any ventilation during the early aspect of resuscitation or avoidance of inadvertent over-ventilation.

OBJECTIVES

To quantify whether chest compressions with guideline-compliant depth (>2 in) produce measurable and substantial ventilation volumes during emergency department resuscitation of out-of-hospital cardiac arrest.

METHODS

This was a prospective, convenience sampling of adult non-traumatic out-of-hospital cardiac arrest patients receiving on-going cardiopulmonary resuscitation in an academic emergency department from June 1, 2011 to July 30, 2013. Cardiopulmonary resuscitation quality files were analyzed using R-Series defibrillator/monitors (ZOLL Medical) and ventilation data were measured using a Non-Invasive Cardiac Output monitor (Philips/Respironics, Wallingford, CT).

RESULTS

cardiopulmonary resuscitation quality data were analyzed from 21 patients (17 males, median age 59). The median compression depth was 2.2 in (IQR = 1.9, 2.5) and the median chest compression fraction was 88.4% (IQR = 82.2, 94.1). We were able to discern 580 ventilations that occurred during compressions. The median passive tidal volume recorded during compressions was 7.5 ml (IQR 3.5, 12.6). While the highest volume recorded was 45.8 ml, 81% of the measured tidal volumes were <20 ml.

CONCLUSION

Ventilation volume measurements during emergency department cardiopulmonary resuscitation after out-of-hospital cardiac arrest suggest that chest compressions alone, even those meeting current guideline recommendations for depth, do not provide physiologically significant tidal volumes.

Are the current guideline recommendations for neonatal cardiopulmonary resuscitation safe and effective?

A recently published review of approaches to optimize chest compressions in the resuscitation of asphyxiated newborns discussed the current recommendations and explored potential determinants of effective neonatal cardiopulmonary resuscitation (CPR). However, not all potential determinants of effective neonatal CPR were explored. Chest compression shallower than the current guideline recommendation of approximately 33% of the anterior-posterior (AP) chest diameter may be safer and more effective. From a physiological standpoint, high-velocity brief duration shallower compression may be more effective than current recommendations. The application of a 1- or 2-finger method of high-impulse CPR, which would depend on the size of the subject, may be more effective than using a 2-thumb (TT) encircling hands method of CPR. Adrenaline should not be used in the treatment of asphyxiated neonates and when necessary titrated vasopressin should be used.

Relationship between arterial partial oxygen pressure after resuscitation from cardiac arrest and mortality in children

BACKGROUND

Observational studies in adults have shown a worse outcome associated with hyperoxia after resuscitation from cardiac arrest. Extrapolating from adult data, current pediatric resuscitation guidelines recommend avoiding hyperoxia. We investigated the relationship between arterial partial oxygen pressure and survival in patients admitted to the pediatric intensive care unit (PICU) after cardiac arrest.

METHODS AND RESULTS

We conducted a retrospective cohort study using the Pediatric Intensive Care Audit Network (PICANet) database between 2003 and 2010 (n=122,521). Patients aged <16 years with documented cardiac arrest preceding PICU admission and arterial blood gas analysis taken within 1 hour of PICU admission were included. The primary outcome measure was death within the PICU. The relationship between postarrest oxygen status and outcome was modeled with logistic regression, with nonlinearities explored via multivariable fractional polynomials. Covariates included age, sex, ethnicity, congenital heart disease, out-of-hospital arrest, year, Pediatric Index of Mortality-2 (PIM2) mortality risk, and organ supportive therapies. Of 1875 patients, 735 (39%) died in PICU. Based on the first arterial gas, 207 patients (11%) had hyperoxia (Pa(O)(2) ≥300 mm Hg) and 448 (24%) had hypoxia (Pa(O)(2) <60 mm Hg). We found a significant nonlinear relationship between Pa(O)(2) and PICU mortality. After covariate adjustment, risk of death increased sharply with increasing hypoxia (odds ratio, 1.92; 95% confidence interval, 1.80-2.21 at Pa(O)(2) of 23 mm Hg). There was also an association with increasing hyperoxia, although not as dramatic as that for hypoxia (odds ratio, 1.25; 95% confidence interval, 1.17-1.37 at 600 mm Hg). We observed an increasing mortality risk with advancing age, which was more pronounced in the presence of congenital heart disease.

CONCLUSIONS

Both severe hypoxia and, to a lesser extent, hyperoxia are associated with an increased risk of death after PICU admission after cardiac arrest.

What is the correct depth of chest compression for infants and children? A radiological study

OBJECTIVE

For infant and child resuscitation, current basic life support guidelines recommend a compression depth of one third to one half of the anteroposterior chest diameter. This study was conducted to assess the actual compression depths in infants and children when current guidelines are strictly followed.

PATIENTS AND METHODS

Chest computed tomography scans of 36 infants (<1 year old) and 38 children (1-8 years old) were reviewed. Patient demographic data were collected from medical records. Measurements of the anteroposterior diameter from chest computed tomography scans were taken from the anterior skin at either the internipple line or the middle of the lower half of the sternum, perpendicular to the skin on the posterior thorax.

RESULTS

In the infant group (25 boys, 11 girls), the mean age was 3.6 months. In the child-age group (21 boys, 17 girls), the mean age was 4.0 years. Compression depths were 3.4 to 5.1 cm in the infant group and 4.4 to 6.6 cm in the child group when current guidelines were followed. There was no difference in compression depths measured at internipple line versus in the lower half of the sternum. The intrathoracic structures observed beneath these 2 suggested that compression landmarks were similar.

CONCLUSIONS

Radiological assessment of infants' and children's chests indicates similar or higher compression depths for infants and children versus the recommended compression depths for adults (3.8-5.1 cm) according to current guidelines. More evidence is needed to guide the proper depth of chest compression in pediatric populations.

Pediatric cardiopulmonary resuscitation: advances in science, techniques, and outcomes

More than 25% of children survive to hospital discharge after in-hospital cardiac arrests, and 5% to 10% survive after out-of-hospital cardiac arrests. This review of pediatric cardiopulmonary resuscitation addresses the epidemiology of pediatric cardiac arrests, mechanisms of coronary blood flow during cardiopulmonary resuscitation, the 4 phases of cardiac arrest resuscitation, appropriate interventions during each phase, special resuscitation circumstances, extracorporeal membrane oxygenation cardiopulmonary resuscitation, and quality of cardiopulmonary resuscitation. The key elements of pathophysiology that impact and match the timing, intensity, duration, and variability of the hypoxic-ischemic insult to evidence-based interventions are reviewed. Exciting discoveries in basic and applied-science laboratories are now relevant for specific subpopulations of pediatric cardiac arrest victims and circumstances (eg, ventricular fibrillation, neonates, congenital heart disease, extracorporeal cardiopulmonary resuscitation). Improving the quality of interventions is increasingly recognized as a key factor for improving outcomes. Evolving training strategies include simulation training, just-in-time and just-in-place training, and crisis-team training. The difficult issue of when to discontinue resuscitative efforts is addressed. Outcomes from pediatric cardiac arrests are improving. Advances in resuscitation science and state-of-the-art implementation techniques provide the opportunity for further improvement in outcomes among children after cardiac arrest.

CPR-why the new emphasis?

The importance of high quality, prompt cardiopulmonary resuscitation (CPR) for patients in cardiac arrest is receiving new attention and emphasis. This extends to CPR for children. In this article, the authors examine the differences in pediatric anatomy and the mechanisms of blood flow during CPR. Additionally, new evidence on the frequent poor performance of CPR and mechanisms to improve it are presented.

Higher survival rates among younger patients after pediatric intensive care unit cardiac arrests

BACKGROUND

Age is an important determinant of outcome from adult cardiac arrests but has not been identified previously as an important factor in pediatric cardiac arrests except among premature infants. Chest compressions can result in more effective blood flow during cardiac arrest in an infant than an older child or adult because of increased chest wall compliance. We, therefore, hypothesized that survival from cardiac arrest would be better among infants than older children.

METHODS

We evaluated 464 pediatric ICU arrests from the National Registry of Cardiopulmonary Resuscitation from 2000 to 2002. NICU cardiac arrests were excluded. Data from each arrest include >200 variables describing facility, patient, prearrest, arrest intervention, outcome, and quality improvement data. Age was categorized as newborn (<1 month; N = 62), infant (1 month to <1 year; N = 105), younger child (1 year to <8 years; N = 90), and older child (8 years to <21 years; N = 207). Multivariable logistic regression was performed to examine the association between age and survival.

RESULTS

Overall survival was 22%, with 27% of newborns, 36% of infants, 19% of younger children and 16% of older children surviving to hospital discharge. Newborns and infants demonstrated double and triple the odds of surviving to hospital discharge from a cardiac arrest in an intensive care setting when compared with older children. When potential confounders were controlled, newborns increased their advantage to almost fivefold, while infants maintained their survival advantage to older children.

CONCLUSIONS

Survival from pediatric ICU cardiac arrest is age dependent. Newborns and infants have better survival rates even after adjusting for potential confounding variables.

Cariporide enables hemodynamically more effective chest compression by leftward shift of its flow-depth relationship

When given during closed-chest resuscitation, cariporide (4-isopropyl-methylsulfonylbenzoyl-guanidine methanesulfonate; a selective inhibitor of the Na(+)/H(+) exchanger isoform-1) enables generation of viable perfusion pressures with less depth of compression. We hypothesized that this effect results from greater blood flows generated for a given depth of compression. Two series of 14 rats each underwent 10 min of untreated ventricular fibrillation followed by 8 min of chest compression before defibrillation was attempted. Compression depth was adjusted to maintain an aortic diastolic pressure (ADP) between 26 and 28 mmHg in the first series and between 36 and 38 mmHg in the second series. Within each series, rats were randomized to receive cariporide (3 mg/kg) or NaCl (0.9%; control) before chest compression was started. Blood flow was measured using 15-mum fluorescent microspheres. Less depth of compression was required to maintain the target ADP when cariporide was present in both series 1 (13.6 +/- 1.2 vs. 16.6 +/- 1.2 mm; P < 0.001) and series 2 (15.3 +/- 1.0 vs. 18.9 +/- 1.5 mm; P < 0.001). Despite less compression depth, the cardiac index in cariporide-treated rats was comparable to control rats in series 1 (11.1 +/- 0.7 vs. 11.3 +/- 1.4 ml.min(-1).kg(-1); P = not significant) but higher in series 2 (15.5 +/- 2.3 vs. 9.9 +/- 1.4 ml.min(-1).kg(-1); P < 0.05). Increases in compression depth (from series 1 to series 2) increased myocardial, cerebral, and adrenal blood flow in cariporide-treated rats. We conclude that cariporide enhances the efficacy of closed-chest resuscitation by leftward shift of the flow-depth relationship.

Hypoxia-ischemia causes abnormalities in glutamate transporters and death of astroglia and neurons in newborn striatum

The neonatal striatum degenerates after hypoxia-ischemia (H-I). We tested the hypothesis that damage to astrocytes and loss of glutamate transporters accompany striatal neurodegeneration after H-I. Newborn piglets were subjected to 30 minutes of hypoxia (arterial O2 saturation, 30%) and then 7 minutes of airway occlusion (O2 saturation, 5%), producing cardiac arrest, followed by cardiopulmonary resuscitation. Piglets recovered for 24, 48, or 96 hours. At 24 hours, 66% of putaminal neurons were injured, without differing significantly thereafter, but neuronal densities were reduced progressively (21-44%). By DNA nick-end labeling, the number of dying putaminal cells per square millimeter was increased maximally at 24 to 48 hours. Glial fibrillary acidic protein-positive cell body densities were reduced 48 to 55% at 24 to 48 hours but then recovered by 96 hours. Early postischemia, subsets of astrocytes had fragmented DNA; later postischemia, subsets of astrocytes proliferated. By immunocytochemistry, glutamate transporter 1 (GLT1) was lost after ischemia in the astroglial compartment but gained in cells appearing as neurons, whereas neuronal excitatory amino acid carrier 1 (EAAC1) dissipated. By immunoblotting, GLT1 and EAAC1 levels were 85% and 45% of control, respectively, at 24 hours of recovery. Thus, astroglial and neuronal injury occurs rapidly in H-I newborn striatum, with early gliodegeneration and glutamate transporter abnormalities possibly contributing to neurodegeneration.

Effects of simulated mouth-to-mouth ventilation during external cardiac compression or active compression-decompression in a swine model of witnessed cardiac arrest

STUDY OBJECTIVE

To assess the effects of simulated mouth-to-mouth (MTM) ventilation on blood gases, gas exchange, and minute ventilation during external cardiac compression (ECC) or active compression-decompression (ACD) in a swine model of witnessed cardiac arrest and bystander CPR.

METHODS

Twenty swine were anesthetized, intubated, ventilated with room air, and monitored for aortic and right atrial pressure and blood gas sampling. After 1 minute of ventricular fibrillation cardiac arrest, ECC or ACD was manually performed at a rate of 100 per minute for 12 minutes. Animals in the room air group had their endotracheal tubes open to air, whereas those in the MTM group were mechanically ventilated with a gas mixture of 16% oxygen and 4% carbon dioxide. Arterial and venous PO2, PCO2, and pH values; oxygen consumption (VO2); carbon dioxide production (VCO2); and minute ventilation (VE) were measured at baseline and 1, 5, 9, and 13 minutes after induction of cardiac arrest.

RESULTS

MTM ventilation did not alter arterial or venous PO2 values in comparison with room air but did result in higher arterial PCO2 values at 5 and 9 minutes (although the mean PCO2 was 40 mm Hg or less [5.3 kPa] in all groups) and significant central venous hypercarbic acidosis at 9 and 13 minutes. Arterial PO2 values were greater in the ACD than the ECC groups at 5, 9, and 13 minutes, although all groups maintained acceptable PO2 (mean values > or = 60 mm Hg [8.0 kPa]) through 9 minutes of CPR and through 13 minutes in all but the ECC-room air group. PCO2 values were lower in the ACD groups beyond 1 minute, with the ACD-room air group showing extreme hyperventilation (mean PCO2 < or = 20 mm Hg [2.7 kPa]). MTM ventilation resulted in negative VO2 and VCO2 for the first few minutes, reflecting changes in pulmonary gas stores. As equilibrium was approached, VO2 and VCO2 approached zero in all groups, reflecting low cardiac output. MTM ventilation did not improve VE over room air at any time during ACD. It did improve VE during ECC, but only at the 12th interval.

CONCLUSION

In this swine model of witnessed CPR, simulated MTM ventilation was not beneficial for blood gases, gas exchange, or ventilation during ECC or ACD CPR.

Paediatric life support. An advisory statement by the Paediatric Life Support Working Group of the International Liaison Committee on Resuscitation

This document reflects the deliberations of ILCOR. The epidemiology and outcome of paediatric cardiopulmonary arrest and the priorities, techniques and sequence of paediatric resuscitation assessments and interventions differ from those of adults. The working group identified areas of conflict and controversy in current paediatric basic and advanced life support guidelines, outlined solutions considered and made recommendations by consensus. The working group was surprised by the degree of conformity already existing in current guidelines advocated by the American Heart Association (AHA), the Heart and Stroke Foundation of Canada (HSFC), the European Resuscitation Council (ERC), the Australian Resuscitation Council (ARC), and the Resuscitation Council of Southern Africa (RCSA). Differences are currently based upon local and regional preferences, training networks and customs, rather than scientific controversy. Unresolved issues with potential for future universal application are highlighted. This document does not include a complete list of guidelines for which there is no perceived controversy and the algorithm/decision tree figures presented attempt to follow a common flow of assessments and interventions, in coordination with their adult counterparts. Survival following paediatric prehospital cardiopulmonary arrest occurs in only approximately 3-17% and survivors are often neurologically devastated. Most paediatric resuscitation reports have been retrospective in design and plagued with inconsistent resuscitation definitions and patient inclusion criteria. Careful and thoughtful application of uniform guidelines for reporting outcomes of advanced life support interventions using large, randomized, multicenter and multinational clinical trials are clearly needed. Paediatric advisory statements from ILCOR will, by necessity, be vibrant and evolving guidelines fostered by national and international organizations intent on improving the outcome of resuscitation for infants and children worldwide.

Diaphragmatic fatigue assessed by 31P-magnetic resonance spectroscopy in vivo

We tested whether fatigue of the piglet diaphragm is associated with inadequate oxidative metabolism as measured by magnetic resonance spectroscopy (MRS). An MRS measured ratio of inorganic phosphate to phosphocreatine (Pi/PCr) > or = 1 was taken as evidence of inadequate oxidative metabolism. Piglets (n = 10) underwent phrenic nerve pacing for 90 min with stimulation frequency of 30 Hz and duty cycle of 0.33. In a separate group of six piglets PCr, Pi, ATP, and intracellular pH were measured by in vivo MRS, and diaphragmatic blood flow was measured with radioactive microspheres at control, 2, 10, 45, 60, and 90 min of pacing. Transdiaphragmatic pressure fell from 25 +/- 3 to 15 +/- 2 mmHg (61 +/- 5%) at 2 min and remained depressed in a separate group of four piglets (P < 0.05). Conversely, compound action potential amplitude remained constant for the first 10 min of pacing and fell to 68 +/- 5% of control at 45 min (P < 0.05). Pi/PCr rose from a control value of 0.32 +/- 0.06 to 0.92 +/- 0.23 at 2 min and 0.79 +/- 0.03 at 10 min (P < 0.05) before returning toward control at 45-90 min. O2 delivery increased from 4.6 +/- 1.2 to 24.7 +/- 4.8 ml.min-1.100 g-1 at 2 min and 18.4 +/- 2.2 ml.min-1.100 g-1 at 10 min (P < 0.05) but then fell to lower levels at 45-90 min. ATP and intracellular pH remained constant except for a decline in pH to 6.98 +/- 0.09 at 45 min (P < 0.05) from the control value of 7.26 +/- 0.06.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of chest compressions between mechanical and manual CPR by monitoring end-tidal PCO2 during human cardiac arrest

STUDY OBJECTIVE

To compare the use of mechanical and manual chest compressions during cardiac arrest based on continuous monitoring of end-tidal PCO2 (PETCO2).

DESIGN

Prospective, randomized, crossover design.

SETTING AND PARTICIPANTS

Fifteen consecutive adults ranging in age from 33 to 78 years who presented in nontraumatic cardiac arrest to the emergency department of a large teaching hospital.

INTERVENTIONS

Study protocols were begun late in the resuscitation after initial resuscitation attempts were unsuccessful. Patients received four alternating five-minute trials (two manual and two mechanical), being randomized to begin with either technique. Mechanical compressions were performed by a mechanical device at a compression depth of 2 in. Both mechanical and manual compressions were delivered at a rate of 80 with a ventilation delivered after every fifth compression. Persons performing manual CPR were experienced American Heart Association basic life support providers, and no person performed manual CPR more than once during the study period. No resuscitative drugs were administered during the study period. PETCO2 was monitored continuously; those performing manual CPR were blinded to the PETCO2 monitor. Data were analyzed with repeated-measures analysis of variance and Scheffé multiple comparisons with the alpha error rate set of .05.

MEASUREMENTS AND RESULTS

Mean PETCO2 during mechanical CPR was 13.6 +/- 4.14 mm Hg compared with 6.9 +/- 2.42 mm Hg during manually performed CPR (P < .001), a difference of 97%. Average mechanical CPR PETCO2 was higher in all cases. No patient was resuscitated successfully. Capnography also indicated that most CPR providers were inconsistent in their chest compressions.

CONCLUSION

This study suggests that cardiac output produced with mechanical chest compressions is greater than that produced with manual compressions as demonstrated by the significantly higher PETCO2 levels during mechanical CPR. Reasons for this are unclear. In addition, monitoring of PETCO2 may help optimize chest compressions during CPR.

Improved blood flow during prolonged cardiopulmonary resuscitation with 30% duty cycle in infant pigs

BACKGROUND

Sustained compression is recommended to maximize myocardial and cerebral blood flow during cardiopulmonary resuscitation (CPR) in adults and children. We compared myocardial and cerebral perfusion during CPR in three groups of 2-week-old anesthetized swine using compression rates and duty cycles (duration of compression/total cycle time) of 100 per minute, 60%; 100 per minute, 30%; and 150 per minute, 30%.

METHODS AND RESULTS

Ventricular fibrillation was induced and CPR was begun immediately with a sternal pneumatic compressor. Epinephrine was continuously infused during CPR. Microsphere-determined blood flow and arterial and sagittal sinus blood gas measurements were made before cardiac arrest was induced and after 5, 10, 20, 35, and 50 minutes of CPR. At 5 minutes of CPR, ventricular and cerebral blood flows were greater than 25 ml.min-1 x 100 g-1 and were not significantly different between groups. When CPR was prolonged, however, myocardial and cerebral blood flows were significantly higher with the 30% duty cycle than with the 60% duty cycle. By 35 minutes, all myocardial regions had less than 5 ml.min-1 x 100 g-1 flow with the 60% duty cycle. In contrast, CPR with the 30% duty cycle at either compression rate provided more than 25 ml.min-1 x 100 g-1 to all ventricular regions for 50 minutes. By 20 minutes, most brain regions received 50% less flow with the 60% duty cycle compared with animals undergoing CPR with the 30% duty cycle (p less than 0.05). Cerebral oxygen uptake was better preserved with the 30% duty cycle. Chest deformation from loss of recoil was greater with the 60% duty cycle compared with the 30% duty cycle.

CONCLUSIONS

We conclude that the shorter duty cycle provides markedly superior myocardial and cerebral perfusion during 50 minutes of CPR in this infant swine model. These data do not support recommendations for prolonged compression at rates of 100 per minute during CPR in infants and children.