The combined use of mechanical CPR and a carry sheet to maintain quality resuscitation in out-of-hospital cardiac arrest patients during extrication and transport

BackgroundQuality of manual cardiopulmonary resuscitation (CPR) during extrication and transport of out-of-hospital cardiac arrest victims is known to be poor. Performing manual CPR during ambulance transport poses significant risk to the attending emergency medical services crew. We sought to use pre-hospital video recording to objectively analyse the impact of introducing mechanical CPR with an extrication sheet (Autopulse, Zoll) to an advanced, second-tier cardiac arrest response team.MethodsThe study was conducted prospectively using defibrillator downloads and analysis of pre-hospital video recording to measure the quality of CPR during extrication from scene and ambulance transport of the OHCA patient. Adult patients with non-traumatic OHCA were included. The interruption to manual CPR to during extrication and to deploy the mechanical CPR device was analysed.ResultsIn the manual CPR group, 53 OHCA cases were analysed for quality of CPR during extrication. The median time that chest compression was interrupted to allow the patient to be carried from scene to the ambulance was 270 s (IQR 201–387 s). 119 mechanical CPR cases were analysed. The median time interruption from last manual compression to first Autopulse compression was 39 s (IQR 29–47 s). The range from last manual compression to first Autopulse compression was 14–118 s.ConclusionMechanical CPR used in combination with an extrication sheet can be effectively used to improve the quality of resuscitation during extrication and ambulance transport of the refractory OHCA patient. The time interval to deploy the mechanical CPR device can be shortened with regular simulation training.     

The effect of transport on quality of cardiopulmonary resuscitation in out-of-hospital cardiac arrest

IntroductionMost manikin and clinical studies have found decreased quality of CPR during transport to hospital. We wanted to study quality of CPR before and during transport for out-of-hospital cardiac arrest patients and also whether quality of CPR before initiation of transport was different from the quality in patients only receiving CPR on scene.Materials and methodsQuality of CPR was prospectively registered with a modified defibrillator for consecutive cases of out-of-hospital cardiac arrest in three ambulance services during 2002–2005. Ventilations were registered via changes in transthoracic impedance and chest compressions were measured with an extra chest compression pad placed on the patients’ sternum. Paired t-tests were used to analyse quality of CPR before vs. during transport with ongoing CPR. Unpaired t-tests were used to compare CPR quality prior to transport to CPR quality in patients with CPR terminated on site.ResultsQuality of CPR did not deteriorate during transport, but as previously reported overall quality of CPR was substandard. Quality of CPR performed on site was significantly better when transport was not initiated with ongoing CPR compared to episodes with initiation of transport during CPR: fraction of time without chest compressions was 0.45 and 0.53 (p < 0.001), compression depth 37 mm and 34 mm (p = 0.04), and number of chest compressions per minute 61 and 56 (p = 0.01), respectively.ConclusionCPR quality was sub-standard both before and during transport. Early decision to transport might have negatively affected CPR quality from the early stages of resuscitation.     

Quantitative analysis of chest compression interruptions during in-hospital resuscitation of older children and adolescents

AimTo quantitatively describe pauses in chest compression (CC) delivery during resuscitation from in-hospital pediatric and adolescent cardiac arrest. We hypothesized that CPR error will be more likely after a chest compression provider change compared to other causes for pauses.MethodsCPR recording/feedback defibrillators were used to evaluate CPR quality for victims ≥8 years who received CPR in the PICU/ED. Audiovisual feedback was supplied in accordance with AHA targets. Etiology of CC pauses identified by post-event debriefing/reviews of stored CPR quality data.ResultsAnalysis yielded 205 pauses during 304.8 min of CPR from 20 consecutive cardiac arrests. Etiologies were: 57.1% for provider switch; 23.9% for pulse/rhythm analysis; 4.4% for defibrillation; and 14.6% “other.” Provider switch accounted for 41.2% of no-flow duration. Compared to other causes, CPR epochs following pauses due to provider switch were more likely to have measurable residual leaning (OR: 5.52; CI⁹⁵: 2.94, 10.32; p < 0.001) and were shallower (43 ± 8 vs. 46 ± 7 mm; mean difference: ?2.42 mm; CI⁹⁵: ?4.71, ?0.13; p = 0.04). Individuals performing continuous CPR ≥ 120 s as compared to those switching earlier performed deeper chest compressions (42 ± 6 vs. 38 ± 7 mm; mean difference: 4.44 mm; CI⁹⁵: 2.39, 6.49; p < 0.001) and were more compliant with guideline depth recommendations (OR: 5.11; CI⁹⁵: 1.67, 15.66; p = 0.004).ConclusionsProvider switches account for a significant portion of no-flow time. Measurable residual leaning is more likely after provider switch. Feedback systems may allow some providers to continue high quality CPR past the recommended switch time of 2 min during in-hospital resuscitation attempts.     

Bystander CPR in out-of-hospital cardiac arrest: the role of limited English proficiency

BackgroundThe proportion of non-native English speakers is increasing in the United States. We sought to determine if limited English proficiency in callers to 9-1-1 for out-of-hospital cardiac arrest is associated with provision of bystander cardiopulmonary resuscitation (CPR) and delays in telephone-assisted CPR.Materials and methodsWe completed a secondary analysis of cohort data collected as part of a randomized trial of emergency dispatcher bystander CPR instructions. Included patients suffered confirmed cardiac arrest treated by emergency medical services. Callers were identified as limited English proficient through review of the dispatcher report.ResultsOf 971 eligible cardiac arrest cases, 5.9% (n = 57) of 9-1-1 callers were limited English proficient. Comparing arrest events of limited English proficient 9-1-1 callers with English-fluent callers, a lower proportion of limited English proficient arrest cases received bystander CPR (64.3% [36/56] vs. 77.5% [702/906]; p = 0.02) or survived to hospital discharge (8.8% [5/57] vs. 16.5% [151/914]; p = 0.12). Dispatchers took longer to recognize cardiac arrest with limited English proficient callers compared with English-fluent callers (median 84 vs. 50 s; p < 0.001). Among callers attempting bystander CPR, the interval from call receipt to initiation of CPR was longer for limited English proficient compared with English-fluent callers (median 237 vs. 163 s; p < 0.001).ConclusionIn this observational study of dispatcher-identified cardiac arrest, limited English proficiency in 9-1-1 callers was associated with less frequent provision of bystander CPR and delays in arrest recognition and implementation of telephone CPR, underscoring the health challenges and potential disparities of pre-hospital care related to limited English proficiency.     

Out-of hospital advanced life support with or without a physician: Effects on quality of CPR and outcome

BackgroundThe presence of physicians is believed to facilitate optimal management of out-of-hospital cardiac arrest, but has not been sufficiently documented.MethodsAdult non-traumatic cardiac arrests treated by Oslo EMS between May 2003 and April 2008 were prospectively registered. Patients were categorized according to being treated by the physician-manned ambulance (PMA) or by regular paramedic-manned ambulances (non-PMA). Patient records and continuous electrocardiograms (ECGs) with impedance signals were reviewed. Quality of cardiopulmonary resuscitation (CPR) and clinical outcomes were compared.ResultsResuscitation was attempted in 1128 cardiac arrests, of which 151 treated by non-PMA and PMA together were excluded from comparative analysis. Of the remaining 977 patients, 232 (24%) and 741 (76%) were treated by PMA and non-PMA, respectively. The PMA group was more likely to have bystander witnessed arrests and initial VF/VT, and received better CPR quality with shorter hands-off intervals and pre-shock pauses, and having a greater proportion of patients being intubated. Despite uneven distribution of positive prognostic factors and better CPR quality, short-term and long-term survival were not different for patients treated by the PMA vs. non-PMA, with 34% vs. 33% (p = 0.74) achieving return of spontaneous circulation (ROSC), 28% vs. 25% (p = 0.50) being admitted to ICU and 13% vs. 11% (p = 0.28) being discharged from hospital, respectively.ConclusionsSurvival after out-of-hospital cardiac arrest was not different for patients treated by the PMA and non-PMA in our EMS system.     

The duration of cardiopulmonary resuscitation in emergency departments after out-of-hospital cardiac arrest is associated with the outcome: A nationwide observational study

Aim of the studyThe appropriate duration of cardiopulmonary resuscitation (CPR) for patients who experience out-of-hospital cardiac arrest (OHCA) remains unknown. This study aimed to evaluate the duration of CPR in emergency departments (EDs) and to determine whether the institutions’ median duration of CPR was associated with survival-to-discharge rate.MethodsA cohort of adult patients from a nationwide OHCA registry was retrospectively evaluated. The main variable was the median duration of CPR for each ED (institutional duration), and the main outcome was survival to discharge. Multivariable logistic regression analysis was performed to adjust for individual and aggregated confounders.ResultsAmong the 107,736 patients who experienced OHCA between 2006 and 2010, 30,716 (28.5%) were selected for analysis. The median age was 65 years, and 67.1% were men. The median duration of CPR for all EDs was 28 min, ranging from 11 to 45 min. EDs were categorized into 3 groups according to their institutional duration of CPR: groups A (<20 min), B (20–29 min), C (≥30 min). The observed survival rates of the 3 groups were 2.11%, 5.20%, and 5.62%, respectively. Compared with group B, the adjusted difference (95% confidence interval) for survival to discharge was 3.01% (1.90–4.11, P < 0.001) for group A, and 0.33% (−0.64 to 1.30, P = 0.51) for group C.ConclusionThe duration of CPR varied widely among hospitals. The institutional duration of CPR less than 20 min was significantly associated with lower survival-to-discharge rate.     

Effects of AED device features on performance by untrained laypersons

ObjectiveOur study evaluates the impact of features of automated external defibrillators (AEDs) on the performance and speed of untrained laypersons to deliver a shock and initiate CPR after a shock.MethodsThis was a randomized trial of volunteer laypersons without AED or advanced medical training. Subjects were assigned to use one of six different models of AEDs on a manikin in simulated cardiac arrest. No instructions on AED operation were provided. Primary endpoints were shock delivery and elapsed time from start to shock. Secondary endpoints included time to power-on, initiation of CPR, adequacy of pad placement and subjects’ ratings of ease of use (1 = very easy, 5 = very difficult).ResultsMost subjects (109/120; 91%) were able to deliver a shock. Median time from start of scenario to shock delivery was 79 s (IQR: 67–99). Of the 11 participants who did not deliver shock, eight never powered on the device. Time to power-on was shorter in devices with open lid (median 12 s, IQR 8–27 s) and pull handle (17 s, IQR 9–20 s) mechanisms than with a push button (37 s, IQR 18–69 s; p = 0.000). Pad position on the manikin was judged adequate for 86 (77%) of the 111 subjects who placed pads. Devices which gave more detailed voice instruction for pad placement had higher rates of adequate pad position [38/39 (97%) versus 50/73 (68%), p = 0.001]. With AEDs that provided step-by-step CPR instruction, 49/58 (84%) subjects began CPR compared to 26/51 (51%) with AEDs that only prompted to start CPR (p = 0.01). Participants rated all the models easy to use (overall mean 1.48; individual device means 1.28–1.71).ConclusionsMost untrained laypersons were successful in delivering a shock. Device features had the most impact on these functions: ability and time to power-on device, adequacy of pad position and initiation of CPR.     

Impairment of carotid artery blood flow by supraglottic airway use in a swine model of cardiac arrest

ObjectiveSupraglottic airway devices (SGDs) are often used as an alternative to endotracheal tube (ETT) during cardiopulmonary resuscitation (CPR). SGDs can be inserted ‘blindly’ and rapidly, without stopping compressions. These devices utilize pressurized balloons to direct air to the trachea and prevent esophagus insufflation. We hypothesize that the use of a SGD will compress the carotid artery and decrease carotid blood flow (CBF) during CPR in pigs.MethodsVentricular fibrillation (VF) was induced in 9 female pigs (32 ± 1 kg) followed by 4 min without compressions. CPR was then performed continuously for 3–6-min intervals. During each interval, an ETT was used for the first 3 min, followed by 3 min of each SGD (King LTS-D?, LMA Flexible?, Combitube?) in a random order. The primary endpoint was mean CBF (ml/min). Statistical comparisons among the 4 airway devices were performed by Wilcoxon Rank test. Post mortem carotid arteriographies were performed with SGDs in place.ResultsCBF (median ml/min; 25/75 percentile) was significantly lower with each SGD [King (10; 6/41), LMA (10; 4/39), and Combitube (5; ?0.4/15)] versus ETT (21; 14/46) (p < 0.05 for each SGD compared with ETT). Arteriograms showed that with each SGD there was compression of the internal and external carotid vessels.ConclusionThe use of 3 different SGDs during CPR significantly decreased CBF in a porcine model of cardiac arrest. While the current study is limited to pigs, the findings suggest that further research on the effects of SGD use in humans and the effects on carotid artery blood flow is warranted.     

Intra-arrest hypothermia: Both cold liquid ventilation with perfluorocarbons and cold intravenous saline rapidly achieve hypothermia,but only cold liquid ventilation improves resumption of spontaneous circulation

BackgroundRapid intra-arrest induction of hypothermia using total liquid ventilation (TLV) with cold perfluorocarbons improves resuscitation outcome from ventricular fibrillation (VF). Cold saline intravenous infusion during cardiopulmonary resuscitation (CPR) is a simpler method of inducing hypothermia. We compared these 2 methods of rapid hypothermia induction for cardiac resuscitation.MethodsThree groups of swine were studied: cold preoxygenated TLV (TLV, n = 8), cold intravenous saline infusion (S, n = 8), and control (C, n = 8). VF was electrically induced. Beginning at 8 min of VF, TLV and S animals received 3 min of cold TLV or rapid cold saline infusion. After 11 min of VF, all groups received standard air ventilation and closed chest massage. Defibrillation was attempted after 3 min of CPR (14 min of VF). The end point was resumption of spontaneous circulation (ROSC).ResultsPulmonary arterial (PA) temperature decreased after 1 min of CPR from 37.2 °C to 32.2 °C in S and from 37.1 °C to 34.8 °C in TLV (S or TLV vs. C p < 0.0001). Coronary perfusion pressure (CPP) was higher in TLV than S animals during the initial 3 min of CPR. Arterial pO₂ was higher in the preoxygenated TLV animals. ROSC was achieved in 7 of 8 TLV, 2 of 8 S, and 1 of 8 C (TLV vs. C, p = 0.03).ConclusionsModerate hypothermia was achieved rapidly during VF and CPR using both cold saline infusion and cold TLV, but ROSC was higher than control only in cold TLV animals, probably due to better CPP and pO₂. The method by which hypothermia is achieved influences ROSC.     

Delayed and intermittent CPR for severe accidental hypothermia

IntroductionCardiac arrest (CA) in patients with severe accidental hypothermia (core temperature <28 °C) differs from CA in normothermic patients. Maintaining CPR throughout the prehospital period may be impossible, particularly during difficult evacuations. We have developed guidelines for rescuers who are evacuating and treating severely hypothermic CA patients.MethodsA literature search was performed. The authors used the findings to develop guidelines.ResultsFull neurological recovery is possible even with prolonged CA if the brain was already severely hypothermic before CA occurred. Data from surgery during deep hypothermic CA and prehospital case reports underline the feasibility of delayed and intermittent CPR in patients who have arrested due to severe hypothermia.ConclusionsContinuous CPR is recommended for CA due to primary severe hypothermia. Mechanical chest-compression devices should be used when available and CPR-interruptions avoided. Only if this is not possible should CPR be delayed or performed intermittently. Based on the available data, a patient with a core temperature <28 °C or unknown with unequivocal hypothermic CA, evidence supports alternating 5 min CPR and ≤5 min without CPR. With core temperature <20 °C, evidence supports alternating 5 min CPR and ≤10 min without CPR.     

A randomised, double-blind, multi-centre trial comparing vasopressin and adrenaline in patients with cardiac arrest presenting to or in the Emergency Department

ObjectiveTo compare vasopressin and adrenaline in the treatment of patients with cardiac arrest presenting to or in the Emergency Department (ED).DesignA randomised, double-blind, multi-centre, parallel-design clinical trial in four adult hospitals.MethodEligible cardiac arrest patients (confirmed by the absence of pulse, unresponsiveness and apnea) aged >16 (aged > 21 for one hospital) were randomly assigned to intravenous adrenaline (1 mg) or vasopressin (40 IU) at ED. Patients with traumatic cardiac arrest or contraindication for cardiopulmonary resuscitation (CPR) were excluded. Patients received additional open label doses of adrenaline as per current guidelines. Primary outcome was survival to hospital discharge (defined as participant discharged alive or survival to 30 days post-arrest).Main resultsThe study recruited 727 participants (adrenaline = 353; vasopressin = 374). Baseline characteristics of the two groups were comparable. Eight participants (2.3%) from adrenaline and 11 (2.9%) from vasopressin group survived to hospital discharge with no significant difference between groups (p = 0.27, RR = 1.72, 95% CI = 0.65–4.51). After adjustment for race, medical history, bystander CPR and prior adrenaline given, more participants survived to hospital admission with vasopressin (22.2%) than with adrenaline (16.7%) (p = 0.05, RR = 1.43, 95% CI = 1.02–2.04). Sub-group analysis suggested improved outcomes for vasopressin in participants with prolonged arrest times.ConclusionsCombination of vasopressin and adrenaline did not improve long term survival but seemed to improve survival to admission in patients with prolonged cardiac arrest. Further studies on the effect of vasopressin combined with therapeutic hypothermia on patients with prolonged cardiac arrest are needed.     

Female sex is not associated with improved rates of ROSC or short term survival following prolonged porcine ventricular fibrillation

ObjectivesThere may be a survival benefit in female patients experiencing cardiac arrest, which could affect the interpretation of in vivo animal studies. We hypothesized that sex predicts return of spontaneous circulation (ROSC) and short-term survival (SURV) in porcine studies of prolonged ventricular fibrillation (VF).MethodsRetrospective analysis of eight comparable experiments performed in our lab using mixed-breed domestic swine of either sex. All experiments included prolonged untreated VF, CPR, defibrillation, and drugs. We defined ROSC as systolic blood pressure ≥80 mmHg for ≥1 min. Short-term survival was defined 20 or 60 min, depending on protocol. Categorical variables were compared with chi-square test and Fisher's exact test. Continuous variables were compared with two-sample t-test and one-way ANOVA. Multiple logistic regression determined predictors of ROSC and SURV, utilizing cluster analysis by experimental protocol. Candidate variables were sex, weight, anesthesia duration, VF duration, and CPR ratio.ResultsOf 263 swine analyzed (53.2% male), 58.6% of males and 68.3% of females had ROSC (p = 0.10), whereas 50.0% of males and 61.0% of females experienced SURV (p = 0.07).ResultsOf 263 swine analyzed (53.2% male), 58.6% of males and 68.3% of females had ROSC (p = 0.10), whereas 50.0% of males and 61.0% of females experienced SURV (p = 0.07). Neither sex nor any identified candidate variable predicted ROSC or SURV. Both models had acceptable fit with Hosmer–Lemeshow values of 0.35 and 0.31, respectively.ConclusionsSex predicts neither ROSC nor SURV in a swine model of prolonged VF.     

Reduced hands-off-time and time to first shock in CPR according to the ERC Guidelines 2005

Background and aimChest compressions and early defibrillation are crucial in cardiopulmonary resuscitation (CPR). The Guidelines 2005 brought major changes to the basic life support and automated external defibrillator (BLS–AED) algorithm. We compared the European Resuscitation Council's Guidelines 2000 (group ‘00) and 2005 (group ‘05) on hands-off-time (HOT) and time to first shock (TTFS) in an experimental model.MethodsIn a randomised, cross-over design, volunteers were assessed in performing BLS–AED over a period of 5 min on a manikin in a simulated ventricular fibrillation cardiac arrest situation. Ten minutes of standardised teaching and 10 min of training including corrective feedback were allocated for each of the guidelines before evaluation. HOT was chosen as the primary and TTFS as the secondary outcome parameter.ResultsForty participants were enrolled; one participant dropped out after group allocation. During the 5-min evaluation period of adult BLS–AED, HOT was significantly (p < 0.001) longer in group ‘00 [273 ± 3 s (mean ± standard error)] than in group ‘05 (188 ± 3 s). The TTFS was significantly (p < 0.001) longer in group ‘00 (91 ± 3 s) than in group ‘05 (71 ± 3 s).ConclusionIn this manikin setting, HOT and TTFS improved with BLS–AED performed according to Guidelines 2005.     

Assessment of CPR interruptions from transthoracic impedance during use of the LUCAS™ mechanical chest compression system

BackgroundQuality of cardiopulmonary resuscitation (CPR) is a key determinant of outcome following out-of-hospital cardiac arrest (OHCA). Recent evidence shows manual chest compressions are typically too shallow, interruptions are frequent and prolonged, and incomplete release between compressions is common. Mechanical chest compression systems have been developed as adjuncts for CPR but interruption of CPR during their use is not well documented.AimAnalyze interruptions of CPR during application and use of the LUCAS? chest compression system.Methods54 LUCAS 1 devices operated on compressed air, deployed in 3 major US emergency medical services systems, were used to treat patients with OHCA. Electrocardiogram and transthoracic impedance data from defibrillator/monitors were analyzed to evaluate timing of CPR. Separately, providers estimated their CPR interruption time during application of LUCAS, for comparison to measured application time.ResultsIn the 32 cases analyzed, compressions were paused a median of 32.5 s (IQR 25–61) to apply LUCAS. Providers’ estimates correlated poorly with measured pause length; pauses were often more than twice as long as estimated. The average device compression rate was 104/min (SD 4) and the average compression fraction (percent of time compressions were occurring) during mechanical CPR was 0.88 (SD 0.09).ConclusionsInterruptions in chest compressions to apply LUCAS can be <20 s but are often much longer, and users do not perceive pause time accurately. Therefore, we recommend better training on application technique, and implementation of systems using impedance data to give users objective feedback on their mechanical chest compression device use.     

Prospective determination of medical necessity for ambulance transport by paramedics

ObjectiveIt has been estimated that between 11% and 61% of ambulance transports to emergency departments are not medically necessary. This study's objective was to analyze paramedic ability to determine the medical necessity of ambulance transport to the emergency department.MethodsParamedics prospectively assessed adult patients transported to an emergency department during a six-week period. The setting was an urban, all advanced life support, public utility model emergency medical services (EMS) system with 58,000 transports per year. Paramedics determined medical necessity of patient transport based on the following five criteria: 1) need for out-of-hospital intervention; 2) need for expedient transport; 3) potential for self-harm; 4) severe pain; or 5) other. On arrival in the emergency department, the emergency physician made a blinded determination based on the same criteria. Kappa statistics were used to assess agreement.ResultsData forms were completed on 825 of 1,420 (58%) patients transported. Emergency physicians determined 248 (30%) transports were not necessary, paramedics 236 (29%), with agreement in 76.2% (K = 0.42) of cases. Paramedics undertriaged 92 patients (11%). Rates of agreement on the five criteria were: 1) 71.9% (K = 0.43); 2) 77.7% (K = 0.22); 3) 89.6% (K = 0.40); 4) 89.6 (K = 0.32); and 5) 82.2% (K = 0.29).ConclusionsParamedics and emergency physicians agreed that a significant percentage of patients did not require ambulance transport to the emergency department. Despite only moderate agreement regarding which patients needed transport, the undertriage rate was low.     

Two minutes CPR versus five cycles CPR prior to reanalysis of the cardiac rhythm: A prospective,randomized simulator-based trial

Aim of the studyWhile the 2005 cardiopulmonary resuscitation (CPR) guidelines recommended to provide CPR for five cycles before the next cardiac rhythm check, the current 2010 guideline now recommend to provide CPR for 2 min. Our aim was to compare adherence to both targets in a simulator-based randomized trial.Methods119 teams, consisting of three to four physicians each, were randomized to receive a graphical display of the simplified circular adult BLS algorithm with the instruction to perform CPR for either 2 min or five cycles 30:2. Subsequently teams had to treat a simulated unwitnessed cardiac arrest. Data analysis was performed using video-recordings obtained during simulations. The primary endpoint was adherence, defined as being within ±20% of the instructed target (i.e. 96–144 s in the 2 min teams and 4–6 cycles in the fivex30:2 teams).Results22/62 (35%) of the “two minutes” teams and 48/57 (84%) of the “five × 30:2″ teams provided CPR within a range of ± 20% of their instructed target (P < 0.0001). The median time of CPR prior to rhythm check was 91 s and 87 s, respectively, (P = 0.59) with a significant larger variance (P = 0.023) in the “two minutes” group.ConclusionsThis randomized simulator-based trial found better adherence and less variance to an instruction to continue CPR for five cycles before the next cardiac rhythm check compared to continuing CPR for 2 min. Avoiding temporal targets whenever possible in guidelines relating to stressful events appears advisable.     

Neonatal CPR: Room at the top—A mathematical study of optimal chest compression frequency versus body size

ObjectiveTo explore in detail the expected magnitude of systemic perfusion pressure during standard CPR as a function of compression frequency for different sized people from neonate to adult.MethodA 7-compartment mathematical model of the human cardiopulmonary system – upgraded to include inertance of blood columns in the aorta and vena cavae – was exercised with parameters scaled to reflect changes in body weight from 1 to 70 kg.ResultsMaximal systemic perfusion pressure occurs at chest compression rates near 60, 120, 180, and 250/min for subjects weighing 70, 10, 3, and 1 kg, respectively. Such maxima are predicted by analytical models describing the dependence of stroke volume on pump-filling time in the presence of blood inertia. This mathematical analysis reproduces earlier experimental results of Fitzgerald et al.¹⁰ in 10 kg dogs.ConclusionsFundamental geometry and physics suggest that the most effective chest compression frequency in CPR depends upon body size and weight. In neonates there is room for improvement at the top of the compression frequency scale at rates >120/min. In adults there may be benefit from lower compression frequencies near 60/min.     

Antecedent bradycardia and in-hospital cardiopulmonary arrest mortality in telemetry-monitored patients outside the ICU

Background Patients with in-hospital cardiopulmonary arrest (IHCA) precipitated by respiratory insufficiency often exhibit bradycardia before the arrest. We hypothesized that bradycardia frequently occurs in the 10 min preceding IHCA and is associated with poor outcomes when IHCA occurs outside the intensive care unit (ICU).ObjectivesTo determine the prevalence and association of antecedent bradycardia with outcome in adult patients with IHCA occurring outside the ICU.Methods We performed a retrospective cohort study among telemetry monitored adults with IHCA outside the ICU in a two-hospital health system between 2008 and 2010 with follow-up until their discharge or death in-hospital.We defined (1) IHCA as >1 min of chest compressions or trans-thoracic defibrillation, (2) Antecedent bradycardia as at least 2 min of continuous heart rate between 1 and 59 beats per minute in the 10 min preceding IHCA, and (3) ventricular tachyarrhythmia arrests as presence of sustained ventricular tachyarrhythmia for >20 s in the 10 min preceding IHCA.ResultsOf 98 IHCAs, 39 (39.8%) survived to hospital discharge. Of 98 IHCAs, 53 (54.1%) had antecedent bradycardia. After adjusting for potential confounders, antecedent bradycardia was associated with death prior to hospital discharge (adjusted OR = 3.80, 95%CI: 1.47–9.81, p = 0.006). Among patients with ventricular tachyarrhythmia arrests, antecedent bradycardia was associated with a higher risk of death (OR = 13.1, 95%CI 1.92–89.5, p = 0.009).ConclusionsAntecedent bradycardia occurred frequently and was associated with death prior to hospital discharge in non-ICU hospitalized adults on telemetry monitoring who developed IHCA.     

Accelerometer as a tool to assess sedentarity and adherence to physical activity recommendations after cardiac rehabilitation program

PurposeTo objectively assess, in stable cardiac patients, the adherence to physical activity (PA) recommendations using an accelerometer at 2 or 12 months after the discharge of cardiac rehabilitation program (CRP).MethodsEighty cardiac patients wore an accelerometer at 2 months (group 1, short-term adherence, n = 41) or one-year (group 2, long-term adherence, n = 39) after a CRP including therapeutic education about regular PA. PA was classified as “light” (1.8–2.9 Metabolic Equivalent of Task [METs]), “moderate” (3–5.9 METs), or “intense” (> 6 METs). Energy expenditure (EE, in Kcal) and time (min) spent in these three different levels were measured during a one-week period with the MyWellness Key actimeter (MWK). Motivational readiness for change was also assessed at the end of CRP. Patients were considered as physically active when a minimum of 150 min of moderate PA during the one-week period was achieved.ResultsBoth groups were comparable, except for exercise capacity at the end of the CRP which was slightly higher in group 1 (167.5 ± 42.3 versus 140.7 ± 46.1 W, P < 0.01). The total weekly active EE averaged 676.7 ± 353.2 kcal and 609.5 ± 433.5 kcal in group 1 and 2, respectively. The time spent within the light-intensity range PA was 319.4 ± 170.9 and 310.9 ± 160.6 min, and the time spent within the moderate-intensity range averaged 157.4 ± 115.4 and 165 ± 77.2 min per week for group 1 and 2, respectively. Fifty-three percent and 41% of patients remained active in both groups respectively.ConclusionAbout half of the patients are non-adherent to PA after CRP and do not reach target levels recommended by physicians. The first 2 months following the discharge of CRP seem to be of outmost importance for lifestyle modifications maintenance, and further study monitoring more closely PA decrease could help to clarify the optimal follow-up options.