Quality of cardiopulmonary resuscitation before and during transport in out-of-hospital cardiac arrest

AIM OF THE STUDY: To evaluate quality of cardiopulmonary resuscitation (CPR) performed during transport after out-of-hospital cardiac arrest. MATERIALS AND METHODS: Retrospective, observational study of all non-traumatic cardiac arrest patients older than 18 years who received CPR both before and during transport between May 2003 and December 2006 from the community run EMS system in Oslo. Chest compressions and ventilations were detected from impedance changes in routinely collected ECG signals, and hands-off ratio calculated as time without chest compressions divided by total CPR time. RESULTS: Seventy-five of 787 consecutive out-of-hospital cardiac arrest patients met the inclusion criteria. Quality data were available from 36 of 66 patients receiving manual CPR and 7 of 9 receiving mechanical CPR. CPR was performed for mean 21+/-11 min before and 12+/-8 min during transport. With manual CPR hands-off ratio increased from 0.19+/-0.09 on-scene to 0.27+/-0.15 (p=0.002) during transport. Compression and ventilation rates were unchanged causing a reduction in compressions per minute from 94+/-14 min(-1) to 82+/-19 min(-1) (p=0.001). Quality was significantly better with mechanical than manual CPR. Four patients (5%) survived to hospital discharge; two with manual CPR (Cerebral performance categories (CPC) 1 and 2), and two with mechanical CPR (CPC scores 3 and 4). No discharged patients had any spontaneous circulation during transport. CONCLUSIONS: The fraction of time without chest compressions increased during transport of out-of-hospital cardiac arrest patients. Every effort should therefore be made to stabilise patients on-scene before transport to hospital, but all transport with ongoing CPR is not futile.     

Performance of cardiopulmonary resuscitation during prolonged basic life support in military medical university students: A manikin study

BACKGROUND: The quality of chest compressions can be significantly improved after training of rescuers according to the latest national guidelines of China. However, rescuers may be unable to maintain adequate compression or ventilation throughout a response of average emergency medical services because of increased rescuer fatigue. In the present study, we evaluated the performance of cardiopulmonary resuscitation(CPR) in training of military medical university students during a prolonged basic life support(BLS).METHODS: A 3-hour BLS training was given to 120 military medical university students. Six months after the training, 115 students performed single rescuer BLS on a manikin for 8 minutes. The qualities of chest compressions as well as ventilations were assessed.RESULTS: The average compression depth and rate were 53.7±5.3 mm and 135.1±15.7 compressions per minute respectively. The proportion of chest compressions with appropriate depth was 71.7%±28.4%. The average ventilation volume was 847.2±260.4 m L and the proportion of students with adequate ventilation was 63.5%. Compared with male students, significantly lower compression depth(46.7±4.8 vs. 54.6±4.8 mm, P0.001) and adequate compression rate(35.5%±26.5% vs. 76.1%±25.1%, P0.001) were observed in female students.CONCLUSIONS: CPR was found to be related to gender, body weight, and body mass index of students in this study. The quality of chest compressions was well maintained in male students during 8 minutes of conventional CPR but declined rapidly in female students after 2 minutes according to the latest national guidelines. Physical fitness and rescuer fatigue did not affect the quality of ventilation.     

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.

The effects of different instructional methods on students’ acquisition and retention of cardiopulmonary resuscitation skills

Background

The need was evident for the evaluation of applicability and effectiveness of different types of instructional strategies to teach CPR skills. Therefore, the aim of this study was to evaluate the effects of traditional, case-based, and web-based instructional methods on acquisition and retention of CPR skills.

Methods

Ninety university students (52 female, 48 male) who selected the first aid course as an elective were assigned randomly to traditional, case-based, and web-based instruction groups. The students were tested three times (pre-test, post-test and retention test) for their measurable and observable CPR skills by using a skill reporter manikin and skill observation checklist.

Results

Based on the CPR chest compression performance measurements by the skill reporter manikin, the web-based instruction group performed poorer than the traditional and case-based instruction groups in “average compression rate, percentage of correct chest compressions, the number of too low hand positions, the number of wrong hand positions, the number of incomplete releases, the average number of ventilations, the average volume of ventilations, the minute volume ventilations, the number of too fast ventilations, the total number of ventilations, and the percentage of correct ventilations” (p < .05). Additionally, 18-week time interval negatively affected students’ performance on “the percentage of correct chest compressions, and total number of compressions”. Similar poor performance by web-based instruction group was also detected by the skill observation checklist.

Conclusion

The students in traditional and case-based instruction groups showed better CPR performance than students in web-based instruction group that used video self-instruction as a learning tool.     

Measuring cardiopulmonary resuscitation performance: a comparison of the Heartsaver checklist to manikin strip

Both checklists and recording manikin strips (strips) are used for evaluation of cardiopulmonary resuscitation (CPR) performance. To examine their relationship, we simultaneously evaluated single rescuer CPR of 255 subjects using both checklists and strips. For Group 1 (N = 192; general public tested in Heartsaver course) we compared the total number of initial ventilations and compressions judged to be correct by checklists with those judged to be correct by strips. For Group II (N = 63; physicians, nurses, general public tested in retention studies) we compared each subjects checklist with their own strip for evaluation of correct ventilations and compressions. In Group I, CPR was judged to be correct two to four times more frequently by checklists than by strips. In Group II, all correlations were poor. The most common disagreements were with performances evaluated as correct by checklist but not by strip. Therefore, the current checklist may be a poor instrument for measuring CPR. More accurate evaluation should improve learning and therefore improve outcome following cardiac arrest.     

Cardiopulmonary resuscitation for cardiac arrest: the importance of uninterrupted chest compressions in cardiac arrest resuscitation

Over the last decade, the importance of delivering high-quality cardiopulmonary resuscitation (CPR) for cardiac arrest patients has become increasingly emphasized. Many experts are in agreement concerning the appropriate compression rate, depth, and amount of chest recoil necessary for high-quality CPR. In addition to these factors, there is a growing body of evidence supporting continuous or uninterrupted chest compressions as an equally important aspect of high-quality CPR. An innovative resuscitation protocol, called cardiocerebral resuscitation, emphasizes uninterrupted chest compressions and has been associated with superior rates of survival when compared with traditional CPR with standard advanced life support. Interruptions in chest compressions during CPR can negatively impact outcome in cardiac arrest; these interruptions occur for a range of reasons, including pulse determinations, cardiac rhythm analysis, electrical defibrillation, airway management, and vascular access. In addition to comparing cardiocerebral resuscitation to CPR, this review article also discusses possibilities to reduce interruptions in chest compressions without sacrificing the benefit of these interventions.     

Quality of BLS decreases with increasing resuscitation complexity

OBJECTIVE: Multiple procedures performed in parallel may cause each procedure to be performed less effectively than if performed in isolation. BLS performed by prehospital providers potentially includes artificial ventilations, chest compressions, and application of an automated external defibrillator (AED). This study examines the effectiveness of artificial ventilation and chest compressions both with and without an AED. METHODS: Thirty-six prehospital providers participated in a prospective observational study. Tested in pairs (n=18), subjects randomly completed three, 6-min scenarios [apneic patient with a pulse (VENT), a pulseless patient (CPR), and a pulseless patient with an AED available (CPR+AED)]. A full-torso manikin capable of generating a carotid pulse was connected to a computer to record number of ventilations, tidal volume, flow rate, number of compressions, and compression depth. Data were analyzed by t-test, ANOVA, and Mann-Whitney U-test. RESULTS: Artificial ventilation performed in isolation provided more correct ventilations than during CPR or CPR+AED (25.7%, 14.2%, 13.7%, p=0.02). Fewer ventilations were delivered during CPR and CPR+AED (p=0.03). More compressions were delivered with CPR alone vs. CPR+AED (51.9, 35.7 min(-1), p=0.00). More correct compressions were delivered during CPR alone vs. CPR+AED (p=0.05). CONCLUSIONS: Both the quality and quantity of BLS decreases as the number of procedures performed simultaneously increases. Further decrements might occur when ALS skills enter into resuscitation. These results suggest a need to automate and/or prompt the performance of BLS to optimize resuscitation.     

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.     

iCPR: a new application of high-quality cardiopulmonary resuscitation training

Objectives

The present study evaluates a new CPR feedback application for the iPhone (iCPR) designed to improve chest compression performance tested in a cardiac arrest simulation to evaluate performance and acceptance by healthcare professionals and lay people.

Methods

We built an application specifically dedicated to self-directed CPR training through a tutorial that includes a simple feedback module to guide training in order to improve the quality of chest compressions. We tested it in a sample of 50 users to evaluate the effect of iCPR on performance and it is acceptance. The participants were randomly assigned to one of the study groups and were asked to perform a trial of 2 min of chest compressions (CC), to answer a predefined set of questions and then to perform two more minutes of CC. The first group performing the sequence of CC with iCPR - questions - CC without feedback, and the second the sequence CC without feedback - questions CC with iCPR.

Results

The mean compression rate was 101 ± 2.8 min⁻¹ when CC were performed with iCPR and 107.8 ± 20.5 min⁻¹ when performed without iCPR (p < 0.01). Overall, the participants considered iCPR useful to maintain CC at the desired rate of 100 compressions per minute.

Conclusions

The iCPR feedback tool was able to significantly improve the performance of chest compressions in terms of the compression rate in a simulated cardiac arrest scenario. The participants also believed that iCPR helped them to achieve the correct chest compression rate and most users found this device easy to use.     

Automated External Defibrillator Program Does Not Impair Cardiopulmonary Resuscitation Initiation in the Public Access Defibrillation Trial

Objectives: To evaluate whether automated external defibrillator (AED) training and AED availability affected the response of volunteer rescuers and performance of cardiopulmonary resuscitation (CPR) in presumed out‐of‐hospital cardiac arrest (OOH‐CA) during the multicenter Public Access Defibrillation Trial. Methods: The Public Access Defibrillation Trial recruited 1,260 facilities in 24 North American regional sites to participate in a trial addressing survival from OOH‐CA when AED training and availability were added to a volunteer‐based emergency response team. Volunteers at each facility were trained to perform either CPR alone (CPR) or CPR in conjunction with AED use (CPR+AED) according to randomized assignments. This study reports the frequency of response and initiation of CPR actions (chest compressions and/or ventilations) by volunteers in the CPR and CPR+AED study groups. Results: A total of 314 presumed OOH‐CA episodes occurred in CPR facilities, and 308 occurred in CPR+AED facilities. The volunteers were matched well for age, gender, and other features. Overall, ventilations (23.1% vs. 13.1%), chest compressions (24.4% vs. 12.1%), and both actions (19.8% vs. 10.5%; all p < 0.05) were more commonly performed in OOH‐CA cases in the CPR+AED group. However, when only OOH‐CA cases with volunteers responding were analyzed, the rates of CPR actions were similar. In the subgroup of CPR+AED cases with a responding volunteer, the AED was turned on for only 47% of cases. Volunteers initiated a CPR action more commonly when the AED was turned on (60.7% vs. 39.3%; p = 0.003). Conclusions: In the Public Access Defibrillation Trial, rates of CPR actions for presumed OOH‐CA victims were low but similar for CPR and CPR+AED responding volunteer rescuers. Factors associated with volunteer response, CPR action initiation, and AED activation warrant further investigation.     

Comparison of two instructional modalities for nursing student CPR skill acquisition

Aims

The purpose of the study was to compare performance based measures of CPR skills (compressions, ventilations with bag-valve-mask (BVM), and single rescuer CPR) from two types of CPR courses: a computer-based course (HeartCode™ BLS) with voice advisory manikin (VAM) feedback and instructor-led (IL) training with traditional manikins.

Methods

604 nursing students from 10 schools of nursing throughout the United States were randomized by school to course type. After successful course completion, students performed 3 min each of compressions; ventilations with BVM; and single rescuer CPR on a Laerdal Resusci Anne^® SkillReporter™ manikin. The primary outcome measures were: (1) compression rate, (2) percentage of compressions performed with adequate depth, (3) percentage of compressions performed with correct hand placement, (4) number of ventilations/min, and (5) percentage of ventilations with adequate volume.

Results

There were no differences in compression rates between the two courses. However, students with HeartCode BLS with VAM training performed more compressions with adequate depth and correct hand placement and had more ventilations with adequate volume than students who had IL courses particularly when learning on hard molded manikins. During single rescuer CPR, students who had HeartCode BLS with VAM training had more compressions with adequate depth and ventilations with adequate volume than students with IL training.

Conclusion

Students who trained using HeartCode BLS and practiced with VAMs performed more compressions with adequate depth and ventilations with adequate volume than students who had IL courses. Results of this study provide evidence to support use of HeartCode BLS with VAM for training nursing students in CPR.     

Continuous chest compression resuscitation in arrested swine with upper airway inspiratory obstruction

Background

This study was designed to compare 24-h survival rates and neurological function of swine in cardiac arrest treated with one of three forms of simulated basic life support CPR.

Methods

Thirty swine were randomized equally among three experimental groups to receive either 30:2 CPR with an unobstructed endotracheal tube (ET) or continuous chest compression (CCC) CPR with an unobstructed ET or CCC CPR with a collapsable rubber sleeve on the ET allowing air outflow but completely restricting air inflow. The swine were anesthetized but not paralyzed. Two min of untreated VF was followed by 9 min of simulated single rescuer bystander CPR. In the 30:2 CPR group, each set of 30 chest compressions was followed by a 15-s pause to simulate the realistic duration of interrupted chest compressions required for a single rescuer to deliver 2 mouth-to-mouth ventilations. The other two groups were provided continuous chest compressions (CCC) without assisted ventilations. At 11 min post-arrest a biphasic defibrillation shock (150 J) was administered followed by a period of advanced cardiac life support.

Results

In the 30:2 group, 8 of 10 animals had good neurological function at 24-h post-resuscitation. In the CCC open airway group, 10 of 10, and in the CCC inspiratory obstructed group, 9 of 10. The number of shocks (P < 0.05) and epinephrine doses (P < 0.05) required for ROSC was greater in the 30:2 CPR group than in the other two groups.

Conclusions

There were no differences in 24-h survival with good neurological function among these three different CPR protocols.     

Feasibility of automated rhythm assessment in chest compression pauses during cardiopulmonary resuscitation

Aim

To demonstrate the feasibility of doing a reliable rhythm analysis in the chest compression pauses (e.g. pauses for two ventilations) during cardiopulmonary resuscitation (CPR).

Methods

We extracted 110 shockable and 466 nonshockable segments from 235 out-of-hospital cardiac arrest episodes. Pauses in chest compressions were already annotated in the episodes. We classified pauses as ventilation or non-ventilation pause using the transthoracic impedance. A high-temporal resolution shock advice algorithm (SAA) that gives a shock/no-shock decision in 3 s was launched once for every pause longer than 3 s. The sensitivity and specificity of the SAA for the analyses during the pauses were computed.

Results

We identified 4476 pauses, 3263 were ventilation pauses and 2183 had two ventilations. The median of the mean duration per segment of all pauses and of pauses with two ventilations were 6.1 s (4.9–7.5 s) and 5.1 s (4.2–6.4 s), respectively. A total of 91.8% of the pauses and 95.3% of the pauses with two ventilations were long enough to launch the SAA. The overall sensitivity and specificity were 95.8% (90% low one-sided CI, 94.3%) and 96.8% (CI, 96.2%), respectively. There were no significant differences between the sensitivities (P = 0.84) and the specificities (P = 0.18) for the ventilation and the non-ventilation pauses.

Conclusion

Chest compression pauses are frequent and of sufficient duration to launch a high-temporal resolution SAA. During these pauses rhythm analysis was reliable. Pre-shock pauses could be minimised by analysing the rhythm during ventilation pauses when CPR is delivered at 30:2 compression:ventilation ratio.     

Protective athletic equipment slows initiation of CPR in simulated cardiac arrest

Objective

Standard protective athletic equipment used in collision sports such as American football poses a unique challenge to rescuers because they block access to both the airway and chest. The main objective of this investigation was to determine the effect of athletic equipment on the initiation of CPR. The feasibility of performing compressions over the chest protector as a potential time-saving step was also evaluated.

Methods

Thirty-four certified athletic trainers performed CPR on a manikin wearing protective equipment during a simulated episode of cardiac arrest. For one trial the protective equipment was removed or unfastened prior to initiating CPR, and for another, chest compressions were initiated over the protective equipment. The following were recorded for comparison purposes: time until first breath and first compression; percentage of compressions delivered to the recommended depth; compression rate; accuracy of hand placement; percentage of compressions without full chest recoil.

Results

Although chest compressions began sooner when compressions were delivered over the chest protector, this improvement was not statistically significant. A more notable positive outcome resulting from keeping the chest protector on was an increase in the number of compressions that were delivered to the recommended depth. Unfortunately, one of the significant negative outcomes of performing chest compression over the chest pad was the increased percentage of compressions that did not obtain full chest recoil.

Conclusions

Although removal of the chest protector delays the initiation of chest compressions, keeping the chest protector on during CPR does not appear to be a feasible option.     

Transthoracic impedance for the monitoring of quality of manual chest compression during cardiopulmonary resuscitation

Objective

The quality of cardiopulmonary resuscitation (CPR), especially adequate compression depth, is associated with return of spontaneous circulation (ROSC) and is therefore recommended to be measured routinely. In the current study, we investigated the relationship between changes of transthoracic impedance (TTI) measured through the defibrillation electrodes, chest compression depth and coronary perfusion pressure (CPP) in a porcine model of cardiac arrest.

Methods

In 14 male pigs weighing between 28 and 34 kg, ventricular fibrillation (VF) was electrically induced and untreated for 6 min. Animals were randomized to either optimal or suboptimal chest compression group. Optimal depth of manual compression in 7 pigs was defined as a decrease of 25% (50 mm) in anterior posterior diameter of the chest, while suboptimal compression was defined as 70% of the optimal depth (35 mm). After 2 min of chest compression, defibrillation was attempted with a 120-J rectilinear biphasic shock.

Results

There were no differences in baseline measurements between groups. All animals had ROSC after optimal compressions; this contrasted with suboptimal compressions, after which only 2 of the animals had ROSC (100% vs. 28.57%, p = 0.021). The correlation coefficient was 0.89 between TTI amplitude and compression depth (p < 0.001), 0.83 between TTI amplitude and CPP (p < 0.001).

Conclusion

Amplitude change of TTI was correlated with compression depth and CPP in this porcine model of cardiac arrest. The TTI measured from defibrillator electrodes, therefore has the potential to serve as an indicator to monitor the quality of chest compression and estimate CPP during CPR.     

Do manual chest compressions provide substantial ventilation during prehospital cardiopulmonary resuscitation?

IntroductionChest compressions have been suggested to provide passive ventilation during cardiopulmonary resuscitation. Measurements of this passive ventilatory mechanism have only been performed upon arrival of out-of-hospital cardiac arrest patients in the emergency department. Lung and thoracic characteristics rapidly change following cardiac arrest, possibly limiting the effectiveness of this mechanism after prolonged resuscitation efforts. Goal of this study was to quantify passive inspiratory tidal volumes generated by manual chest compression during prehospital cardiopulmonary resuscitation.Materials and methodsA flowsensor was used during adult out-of-hospital cardiac arrest cases attended by a prehospital medical team. Adult, endotracheally intubated, non-traumatic cardiac arrest patients were eligible for inclusion. Immediately following intubation, the sensor was connected to the endotracheal tube. The passive inspiratory tidal volumes generated by the first thirty manual chest compressions performed following intubation (without simultaneous manual ventilation) were calculated.Results10 patients (5 female) were included, median age was 64 years (IQR 56, 77 years). The median compression frequency was 111 compression per minute (IQR 107, 116 compressions per minute). The median compression depth was 5.6 cm (IQR 5.4 cm, 6.1 cm). The median inspiratory tidal volume generated by manual chest compressions was 20 mL (IQR 13, 28 mL).ConclusionUsing a flowsensor, passive inspiratory tidal volumes generated by manual chest compressions during prehospital cardiopulmonary resuscitation, were quantified. Chest compressions alone appear unable to provide adequate alveolar ventilation during prehospital treatment of cardiac arrest.     

Availability and quality of cardiopulmonary resuscitation information for Spanish-speaking population on the Internet

Background

Bystander cardiopulmonary resuscitation (CPR) is a vital link in the chain of survival for out-of-hospital cardiac arrest (OHCA); however, there are racial/ethnic disparities in the provision of bystander CPR. Approximately 32% of Hispanics perform CPR when confronted with cardiac arrest, whereas approximately 41% of non-Hispanics perform CPR. Public education, via the Internet, may be critical in improving the performance of bystander CPR among Hispanics. The objective of this study was to evaluate the availability and quality of CPR-related literature for primary Spanish-speaking individuals on the Internet.

Methods

Two search engines (Google and Yahoo!) and a video-site (YouTube) were searched using the following terms: “resucitacion cardiopulmonar” and “reanimacion cardiopulmonar.” Inclusion criteria were: education of CPR technique. Exclusion criteria were: instruction on pediatric CPR technique, failure to provide any instruction on CPR technique, or duplicated website. Data elements were collected on the content and quality of the websites and videos, such as assessing scene safety, verifying responsiveness, activating EMS, properly positioning hands on chest, performing accurate rate and depth of compressions.

Results

Of the 515 websites or videos screened, 116 met criteria for inclusion. The majority of websites (86%; 95% Confidence Interval [CI] 79–92%) educated viewers on traditional bystander CPR (primarily, 30:2 CPR), while only 14% (95% CI 9–21%) taught hands-only CPR. Of websites that used video (N = 62), 84% were conducted in Spanish and 16% in English. The quality of CPR education was generally poor (median score of 3/6, IQR of 3.0). Only half of websites properly educated on how to check responsiveness, activate EMS and position hands on chest. Eighty-eight percent of websites failed to educate viewers on assessing scene safety. The majority of websites had improper or no education on both rate and depth of compressions (59% and 63%, respectively). Only 16% of websites included 5 or more quality markers for proper bystander CPR.

Conclusions

A small proportion of internet resources have high quality CPR education for a Spanish-speaking population. More emphasis should be placed on improving the quality of educational resources available on the Internet for Spanish-speaking populations, and with particular emphasis on current basic life support recommendations.     

Mechanical cardiopulmonary resuscitation for patients with cardiac arrest

BACKGROUND:

Although modern cardiopulmonary resuscitation (CPR) substantially decreases the mortality induced by cardiac arrest, cardiac arrest still accounts for over 50% of deaths caused by cardiovascular diseases. In this article, we address the current use of mechanical devices during CPR, and also compare the CPR quality between manual and mechanical chest compression.

METHODS:

We compared the quality and survival rate between manual and mechanical CPR, and then reviewed the mechanical CPR in special circumstance, such as percutaneous coronary intervention, transportation, and other fields.

RESULTS:

Compared with manual compression, mechanical compression can often be done correctly, and thus can compromise survival; can provide high quality chest compressions in a moving ambulance; enhance the flow of blood back to the heart via a rhythmic constriction of the veins; allow ventilation and CPR to be performed simultaneously.

CONCLUSION:

Mechanical devices will be widely used in clinical practice so as to improve the quality of CPR in patients with cardiac arrest.KEY WORDS: Cardiopulmonary resuscitation, Manual compression, Mechanical compressionCardiopulmonary resuscitation (CPR), also called basic life support, is an emergency medical procedure performed to restore blood flow (circulation) and breathing. The goal of CPR is to provide oxygen quickly to the brain, heart, lungs, and other organs until normal function of the heart and lung is restored. CPR can help prevent brain damage and death in children.[1] It is reported that approximately 600 000 individuals suffer from cardiac arrest and receive cardiopulmonary resuscitation in the United States and Europe each year.[2,3] Although modern CPR substantially decreases the mortality induced by cardiac arrest, cardiac arrest still accounts for over 50% of deaths caused by cardiovascular diseases.[4]The success rate of CPR ranging widely from 5% to 10% is based on many factors such as (1) causes of cardiac or respiratory arrest; (2) underlying health conditions of victims; (3) time elapse between arrest and CPR; and (4) techniques for CPR.[5,6] The survival rate is affected not only by CPR but more importantly by its quality. Effective CPR can contribute more blood flow to the brain, heart and other organs, and thus increase the survival rate of patients with cardiac arrest.[7] In November 2005 the AHA revised CPR guidelines to emphasize chest compression and its effect on blood pressure.[8] Studies[7,9,10] showed that by taking fewer breaks between compressions, rescuers can keep blood pressure higher, which helps to pump blood to the brain and other vital organs. However, during CPR even with the best manual chest compressions, cardiac output is approximately 20% to 30% of normal value, and performer''s fatigue may also reduce the quality of the compressions. Besides, chest compressions can not be performed during the transportation of patients, which prolong the time between the arrest and CPR, and also increase the difficulty of resuscitation.[11,12] Therefore, to avoid or reduce these negative factors and to improve the CPR quality, mechanical devices are frequently used.In this article we address the current use of mechanical devices during CPR, and also compare the CPR quality between manual and mechanical chest compression.

Comparison of quality between manual and mechanical CPR

In 1961, Harrison-Paul[13] applied the electric pneumatic device clinically, and then Kouwenhoven et al[14] introduced closed chest cardiac massage for CPR in 1969. The Kouwenhoven technique has been shown repeatedly its clinically inefficacy. Although this technique can clearly save lives, its inherent inefficiency and the challenges related to teaching and retaining the skills needed to perform the technique correctly have limited its overall effectiveness. This has prompted us to develop new life-saving CPR techniques and devices.At present, the most commonly used mechanical chest-compression devices include LUCASTM, Autopluse, Lifebelt, Thumper and Brunswick-TM HLR R30. Compared with manual compression, mechanical compression can: (1) often be done correctly, and thus can compromise survival; (2) potentially improve the quality of chest compression with automatic mechanical devices, which can potentially apply compression more consistently than manually; (3) can provide high quality chest compressions in a moving ambulance, which is very difficult to accomplish with manual CPR; (4) allow a reduction in a number of emergency medical systems (EMS) personnel needed to perform resuscitation;[15] (5) allow ventilation and CPR to be performed simultaneously; (6) enhance the flow of blood back to the heart via a rhythmic constriction of the veins.[16]Autopulse can markedly increase the mean systolic blood pressure from 72 mmHg to 106 mmHg, and the average diastolic blood pressure from 17 mmHg to 23 mmHg as compared with manual compression (P<0.05). In addition, Autopulse can obviously improve coronary perfusion, and generate approximately 36% of the normal blood flow, which is much higher than that generated by manual compression (13%).[17] But before and after use of Autopulse, there is no significant difference in the pressure of end tidal carbon dioxide (PETCO₂), which serves as an important parameter for evaluating cardiac output and pulmonary blood flow.[18] Axelsson et al[5] reported that in 126 patients who participated in the study, 64 were enrolled in a mechanical chest compression group and 62 in a control group. The group receiving mechanical ACD-CPR showed highest PETCO₂ values in contrast to the average (P=0.04), initial (P=0.01) and minimum (P=0.01) values. There was no significant difference in the maximum values between the two groups. This indicated that chest compression can increase blood supply to the heart and lung.

Comparison of survival rate

Although mechanical CPR can increase cardiac output, coronary and cerebral blood flow, arterial blood pressure, and PETCO₂, whether mechanical CPR can increase the survival rate of patients with cardiac arrest is still in debate. Skogvoll et al[19] reported that there were no significant differences between mechanical and manual CPR compression (survival rates 13% vs. 12%) in 302 patients with cardiac arrest. Another prospective trial showed that the survival rate of patients after hospitalization for 24, 48, and 72 hours and the number of patients who had reestablished spontaneous circulation was increased in the mechanical compression group, but no differences were observed between the mechanical and manual CPR compression groups.[18] In a prospective randomized trial conducted by Kouwenhoven[14], 1410 patients received mechanical CPR and 1456 received manual CPR. The survival rate of the mechanical CPR group was significantly higher than that of the manual CPR group (23.8% vs. 20.6%, P< 0.05). Ong et al[17] also reported that mechanical CPR increased the survival rate of patients. But Skogvoll et al[19] described in their randomized clinical trial that mechanical CPR increased the mortality of patients. Thus further clinical studies or animal experiments are needed to confirm this finding.

Mechanical CPR in special circumstance

Percutaneous coronary intervention (PCI)

In most cases, cardiopulmonary arrest is derived from the heart. Myocardial ischemia caused by acute coronary occlusion can lead to the development of ventricular fibrillation. PCI was thought to be useful in patients with acute ST elevation myocardial infarction (STEMI),[20,21] and it was also beneficial to patients after recovery of spontaneous circulation.[22] Sunde et al[23,24] found that the mortality of patients treated with PCI (n=12) was significantly lower than that of patients treated conservatively (n=20) (17% vs. 70%). However, PCI is seldom used in patients with cardiac arrest.[25] CPR is still required to perform PCI during cardiac arrest, but it is very difficult to simultaneously perform manual CPR and PCI. Mechanical chest compression allows for continued PCI despite ongoing cardiac or circulatory arrest with artificially sustained circulation. A study[25] reported that in 3058 patients treated with PCI for ST-elevation myocardial infarction (STEMI), 118 were in cardiogenic shock and 81 required defibrillation. LUCAS was used in 38 patients, 1 underwent a successful pericardiocentesis, and 36 were treated with PCI. Eleven of these patients were discharged alive in good neurological conditions. Similarly, other studies have shown that that it is feasible to perform mechanical CPR during PCI.[26–29]

Transportation

During ambulance transport to hospital, it may not be possible to perform manual CPR, while mechanical devices may play an important role in maintaining circulation.

Other fields

Mechanical devices have been used in imaging diagnosis. Agostoni et al[30] evaluated both CT image quality in a phantom study and feasibility in an initial case series using automated chest compression (A-CC) devices for cardiopulmonary resuscitation (CPR), and they found under CPR conditions multidetector CT diagnostics supports either focused treatment or the decision to terminate efforts.

Limitations of mechanical CPR

Delayed time-elapse between arrest and CPR

Device use may delay the time-elapse between arrest and CPR. Ong et al[31] reported that LUCAS device delayed CPR for 2.9±2.1 minutes when compared with manual compression. Another study showed that the median no-flow time, defined as the sum of all pauses between compressions longer than 1.5 seconds, during the first 5 minutes of resuscitation, was manual CPR 85 seconds (interquartile range [IQR] 45 to 112 seconds) versus mechanical CPR 104 seconds (IQR 69 to 151 seconds). The mean no-flow ratio, defined as no-flow time divided by segment length, was manual 0.28 versus mechanical CPR 0.40 (difference=−0.12; 95% confidence interval −0.22 to −0.02). However, from 5 to 10 minutes into the resuscitation, the median no-flow time was manual 85 seconds (IQR 59 to 151 seconds) versus mechanical CPR 52 seconds (IQR 34 to 82 seconds) and the mean no-flow ratio manual 0.34 versus mechanical CPR 0.21 (difference=0.13; 95% confidence interval 0.02 to 0.24). The average time to apply mechanical CPR during this period was 152 seconds. This suggests that in the first 5 minutes, the quality of manual CPR is higher than that of mechanical CPR; while during 5-10 minutes, the quality of mechanical CPR was improved. Hallstrom et al[19] reported that use of an automated LDB-CPR device as used in this study was associated with worse neurological outcomes and a trend toward worse survival than manual CPR. These factors might partly explain the varied outcomes treated with mechanical CPR.

Injuries associated with mechanical CPR

Mechanical chest compression can also cause injuries in patients. Hallstrom et al[32,33] reported that fracture was present in 10/47 in the manual group and in 11/38 in the LUCAS group (P=0.46), and there were multiple rib fractures (> or =3 fractures) in 13/47 in the manual group and in 17/38 in the LUCAS group (P=0.12). Bleeding in the ventral mediastinum was noted in 2/47 and 3/38 in the manual and LUCAS groups respectively (P=0.65), retrosternal bleeding in 1/47 and 3/38 (P=0.32), epicardial bleeding in 1/47 and 4/38 (P=0.17), and hemopericardium in 4/47 and 3/38 (P=1.0), respectively. This finding indicates that mechanical chest compression with the LUCAS device appears to be associated with the same variety and incidence of injuries as manual chest compression. For the injuries caused by mechanical CPR, we still need further clinical studies.In conclusion, mechanical devices will be widely used in clinical practice so as to improve the quality of CPR in patients with cardiac arrest.     

Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study

AIMS: To compare quality of CPR during out-of-hospital cardiac arrest with and without automated feedback. MATERIALS AND METHODS: Consecutive adult, out-of-hospital cardiac arrests of all causes were studied. One hundred and seventy-six episodes (March 2002-October 2003) without feedback were compared to 108 episodes (October 2003-September 2004) where automatic feedback on CPR was given. Automated verbal and visual feedback was based on measured quality with a prototype defibrillator. Quality of CPR was the main outcome measure and survival was reported as specified in the protocol. RESULTS: Average compression depth increased from (mean +/- S.D.) 34 +/- 9 to 38 +/- 6 mm (mean difference (95% CI) 4 (2, 6), P < 0.001), and median percentage of compressions with adequate depth (38-51 mm) increased from 24% to 53% (P < 0.001, Mann-Whitney U-test) with feedback. Mean compression rate decreased from 121 +/- 18 to 109 +/- 12 min(-1) (difference -12 (-16, -9), P = 0.001). There were no changes in the mean number of ventilations per minute; 11 +/- 5 min(-1) versus 11 +/- 4 min(-1) (difference 0 (-1, 1), P = 0.8) or the fraction of time without chest compressions; 0.48 +/- 0.18 versus 0.45 +/- 0.17 (difference -0.03 (-0.08, 0.01), P = 0.08). With intention to treat analysis 7/241 control patients were discharged alive (2.9%) versus 5/117 with feedback (4.3%) (OR 1.5 (95% CI; 0.8, 3), P = 0.2). In a logistic regression analysis of all cases, witnessed arrest (OR 4.2 (95% CI; 1.6, 11), P = 0.004) and average compression depth (per mm increase) (OR 1.05 (95% CI; 1.01, 1.09), P = 0.02) were associated with rate of hospital admission. CONCLUSIONS: Automatic feedback improved CPR quality in this prospective non-randomised study of out-of-hospital cardiac arrest. Increased compression depth was associated with increased short-term survival. TRIAL REGISTRATION: ClinicalTrials.gov (NCT00138996), http://www.clinicaltrials.gov/.