胸外按压的作用及研究

胸外按压是基础生命支持中重要内容之一,其地位越来越受到重视。其机制、频率、通气和按呼比等的研究对提高心肺复苏成功率具有重要意义。     

心肺复苏中胸外按压作用及研究进展

心肺复苏(CPR)中基础生命支持(BLS)是整个复苏过程的基础和关键,胸外按压在BLS的地位越来越受到重视,有关胸外按压的频率问题、胸外按压与呼吸比例的问题以及胸外按压确切机制一直是急诊医学界关注的焦点,我国心肺复苏的基础研究应该进一步的加强。     

心肺复苏胸外按压的生物力学研究

目的 通过对人体尸体标本的生物力学测试,研究人体胸廓在外力作用下的应力、应变特点,探讨胸外按压时胸廓受力变形的机制.方法 成年男性尸体标本1具,使用MTS材料试验机和引伸仪,采用O～200 N载荷,分别模拟人体按压时胸廓所承受的负重工况,测试垂直加压情况下胸廓的位移和应变.结果 测试得出静态加压和动态加压时胸廓的载荷-位移关系和载荷-应变关系数据并得出统计曲线.结论 通过人体胸廓生物力学测试发现了胸外按压时人体胸廓下压深度与按压力量的关系,并提出初步的计算公式.     

心肺脑的复苏及护理

心肺脑复苏 (ＣＰＣＲ)是对心脏呼吸骤停病人采用急救措施 ,以恢复和维持病人有效的自主血液循环、呼吸功能及神经系统功能 ,进而达到防止突然意外死亡、脑损害并恢复智能的目的。自 80年代以来ＣＰＣＲ以早期基本生命支持 (ＢＬＳ)、进一步生命支持 (ＡＬＳ)和持续生命支持 (ＰＬＳ)三期紧密联系 ,相互制约地将复苏全程进行已被广泛应用 ,而与其相适应的ＣＰＣＲ护理技术也得到了进一步发展 ,现就ＣＰＣＲ及护理的若干问题综述如下。1　胸外心脏按压及人工呼吸1.1　胸外心脏按压　 1992年美国心脏病学会修订了心肺复苏 (ＣＰＲ)指南 ,首先…     

胸外心脏按压机制探讨

目的：探讨临床心跳骤停病人行胸外按压时的血流动力学机制。方法：13例使用Swan－Ganz导管和有创血压监测的危重病人在呼吸心跳停止后给予高浓度吸氧，并持续胸外按压（频率80～170次／min）心肺复苏，分段测血流动力学指标。结果：1．心排量（0．98～4．18L／min，平均2．34±1．19L／min）在按压的前1～3min内呈先升后降变化；2．所测各处右房压、肺动脉压、外周动脉压不等，心脏灌注压为5．60±6．80／0．80±1．87（平均压2．00±3．33）kPa。由于收缩压差大，舒张压差小，故按压期可能为心脏的灌注期；3．心排量在按压频率100～150次／min范围可获得较高心排量，高频率的作用在于使胸壁、胸腔、大血管（动脉、静脉）、心腔之间产生了最佳的频率共振，达到了较理想的心排量，可能最佳胸外按压频率在120～140次／min之间，能有2倍于常规频率（80～100次／min）的能量传递；4．肺循环阻力（PVR）大于外周循环阻力（SVR），右心室功（RVW）及右室每搏功（RVSW）下降幅度小于左心室功（LVW）、左室每搏功（LVSW），说明胸外按压更多影响在肺循环和右心腔部分。结论：胸外心脏按压在高频率时存在频率共振机制，最佳的共振频率可能在120～140次／min。     

MSCPR-1A数字化多功能心肺复苏机在急诊心肺复苏中的应用体会

目的:比较MSCPR-1A心肺复苏机和人工心肺复苏2种方法的临床效果。方法:53例心跳呼吸骤停患者分为心肺复苏机复苏组和人工标准复苏组,比较2组优缺点及循环、呼吸恢复率。结果:使用心肺复苏机进行心肺复苏,患者的循环和呼吸恢复率均高于人工标准心肺复苏(CPR),而且可以克服人工CPR的缺陷。结论:心肺复苏机与人工心肺复苏相比具有较大的优越性,可以提高复苏质量,值得在临床推广。     

自动心肺复苏机胸外按压在心跳骤停患者中的应用进展

自动心肺复苏机是一种全自动的、同步胸外心脏按压、间歇正压通气的仪器。自2005年心肺复苏指南进一步强调有效按压是建立人工循环的关键以来[1],已有许多研究比较自动心肺复苏胸外按压仪在临床的优势,如早期就有报道自动心肺复苏机可     

与胸外心脏按压同时和非同时机械通气对心肺复苏影响的比较

目的：探讨与胸外心脏按压同时和非同时机械通气在心肺复苏中应用的效果。方法：将12例心跳呼吸骤停患者随机分为与胸外心脏按压同时控制机械通气组和与胸外按压非同时手控机械通气组。采用控制通气模式机械通气与持续循手胸外心脏按压同时进行;后者采用手控通气模式机械通气（MAMV）与间断徒手胸外心脏按压非同时配配合进行心肺复苏,胸外心脏按压每5次后暂停1次,在暂停间期给予MAMV1次,之后通气与按压依此比例进行。2组均进行无创动脉血压、心电、经皮氧饱和度（SpO2)、潮气量（VT)、气道峰压（Ppeak)等监测。结果：与胸外心脏按压非同时手控机械通气组的SpO2、VT均明显高于与胸外心脏按压同时模式通气组的SpO2和VT,P均＜0．05;而peak则明显低于后者,P＜0．05;2组的平均动脉压无显著差别。结论：与胸外心脏按压非同时手控机械通气在提高SpO2、VT,降低Ppeak,恢复窦性心律及提高心肺复苏成功率等方面明显优于与胸外心脏按压同时控制机械通气。     

胸外按压影响因素的分析与对策

总结了影响胸外按压效果的各种影响因素，并分析提出相关对策。其中主要影响因素包括人－机不协调、合并胸部外伤、按压有效性降低、按压频率无具体指标等，认为胸外按压质量是提高心肺复苏成功率的重要保障，本院针对影响胸外按压质量采取的各种措施效果明显，值得临床推广，但有待于循证医学依据进一步支持。     

心肺复苏胸外按压深度控制器的研究

目的 研究设计出一种装置,使医务人员在心肺复苏时能够明确胸外按压的有效深度,以减少按压不足或按压过度,有利于提高心肺复苏效果.方法 采用自主研制的胸外按压深度控制器,结合心肺复苏模拟人系统,随机挑选具有心肺复苏经验的医务人员进行操作实验,同时设立对照组,对两组胸外按压有效率进行比较分析.结果 实验组胸外按压有效率高于对照组(P<0.01).结论 胸外按压深度控制器能够提高医务人员心肺复苏时胸外按压的有效率.     

Metronome improves compression and ventilation rates during CPR on a manikin in a randomized trial

Aim

We hypothesized that a unique tock and voice metronome could prevent both suboptimal chest compression rates and hyperventilation.

Methods

A prospective, randomized, parallel design study involving 34 pairs of paid firefighter/emergency medical technicians (EMTs) performing two-rescuer CPR using a Laerdal SkillReporter Resusci Anne^® manikin with and without metronome guidance was performed. Each CPR session consisted of 2 min of 30:2 CPR with an unsecured airway, then 4 min of CPR with a secured airway (continuous compressions at 100 min⁻¹ with 8-10 ventilations/min), repeated after the rescuers switched roles. The metronome provided “tock” prompts for compressions, transition prompts between compressions and ventilations, and a spoken “ventilate” prompt.

Results

During CPR with a bag/valve/mask the target compression rate of 90-110 min⁻¹ was achieved in 5/34 CPR sessions (15%) for the control group and 34/34 sessions (100%) for the metronome group (p < 0.001). An excessive ventilation rate was not observed in either the metronome or control group during CPR with a bag/valve/mask. During CPR with a bag/endotracheal tube, the target of both a compression rate of 90-110 min⁻¹ and a ventilation rate of 8-11 min⁻¹ was achieved in 3/34 CPR sessions (9%) for the control group and 33/34 sessions (97%) for the metronome group (p < 0.001). Metronome use with the secured airway scenario significantly decreased the incidence of over-ventilation (11/34 EMT pairs vs. 0/34 EMT pairs; p < 0.001).

Conclusions

A unique combination tock and voice prompting metronome was effective at directing correct chest compression and ventilation rates both before and after intubation.     

Incomplete chest wall decompression: a clinical evaluation of CPR performance by trained laypersons and an assessment of alternative manual chest compression-decompression techniques

BACKGROUND: Complete chest wall recoil improves hemodynamics during CPR by generating relatively negative intrathoracic pressure, which draws venous blood back to the heart, providing cardiac preload prior to the next chest compression. OBJECTIVE: This study was designed to assess the quality of CPR delivered by trained laypersons and to determine if a change in CPR technique or hand position would improve complete chest wall recoil, while maintaining adequate duty cycle, compression depth, and proper hand position placement. Standard manual CPR and three alternative manual CPR approaches were assessed. METHODS: This randomized prospective trial was performed on an electronic test manikin. Thirty laypersons (mean age of 40.6 years (range 28-55)), who were trained in CPR within the last 24 months, signed an informed consent and participated in the trial. Subjects performed 3 min of CPR on a Laerdal Skill Reportertrade mark CPR manikin using the Standard Hand Position followed by 3 min of CPR (in random order) using three alternative CPR techniques: (1) Two-Finger Fulcrum Technique - lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using the thumb and little finger as a fulcrum; (2) Five-Finger Fulcrum Technique - lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using all five fingers as a fulcrum; (3) Hands-Off Technique - lifting the heel and all fingers of the hand slightly but completely off the chest during the decompression phase of CPR. The participants did not know the purpose of the study prior to, or during this investigation. RESULTS: Adequate compression depth was poor for all hand positions tested and ranged only from 18.6 to 35.7% of all compressions. When compared with the Standard Hand Position, the Hands-Off Technique decreased the mean compression duty cycle from 39.0 +/- 1.0 to 33.5 +/- 1.0%, (P < 0.0001) but achieved the highest rate of complete chest wall recoil (92.5% versus 24.1%, P < 0.0001) and was 46.3 times more likely to provide complete chest wall recoil (OR: 46.3; CI: 16.4-130.3). There were no significant differences in accuracy of hand placement, adequate depth of compression, or perceived discomfort with its use compared with the Standard Hand Position. CONCLUSIONS: The Hands-Off Technique decreased compression duty cycle but was 46.3 times more likely to provide complete chest wall recoil (OR: 46.3; CI: 16.4-130.3) compared to the Standard Hand Position without differences in accuracy of hand placement, adequate depth of compression, or perceived discomfort with its use. All forms of manual CPR tested (including the Standard Hand Position) in trained laypersons produced an inadequate depth of compression for two-thirds of the time. These data support development and testing of more effective layperson CPR training programmes and more effective means to deliver manual as well as mechanical CPR.     

The physiological effect on rescuers of doing 2min of uninterrupted chest compressions

OBJECTIVES: To analyse how rescuers tolerate the effort derived of giving uninterrupted chest compressions during 2min. MATERIALS AND METHODS: Twenty-three healthy volunteers, nurses and doctors of the Intensive Care Unit (ICU), members of the hospital cardiac arrest team, were enrolled in the study. Using a training manikin, participants were asked to perform chest compressions during 2min at a rate of 100min(-1). The oxygen saturation and cardiac rate of the subjects were monitored using pulse oximetry before and after one and 2min performing chest compressions. The percentage of the maximal heart rate of the rescuer over the theoretical maximum allowed in a conventional stress test was calculated, taking into account age and body mass index (BMI) of the subjects. Fatigue was measured using a visual analogical scale (VAS). RESULTS: The means (+/-S.D.) of chest compressions in the first and second minutes were 103+/-12, and 104+/-11, respectively. The mean percent of the maximum heart rate observed was 61+/-8%. None of the subjects had difficulties to complete the test. All subjects recovered their basal values in less than 2min, and the mean value recorded in the VAS was 3+/-2. CONCLUSIONS: The practice of uninterrupted chest compressions during 2min by the same rescuer is well tolerated by health professionals trained in cardiopulmonary resuscitation (CPR).     

Simplified dispatch-assisted CPR instructions outperform standard protocol

OBJECTIVE: Dispatch-assisted chest compressions only CPR (CC-CPR) has gained widespread acceptance, and recent research suggests that increasing the proportion of compression time during CPR may increase survival from out-of-hospital cardiac arrest. We created a simplified CC-CPR protocol to reduce time to start chest compressions and to increase the proportion of time spent delivering chest compressions. This simplified protocol was compared to a published protocol, Medical Priority Dispatch System (MPDS) Version 11.2, recommended by the National Academies of Emergency Dispatch. METHODS: Subjects were randomized to the MPDS v11.2 protocol or a simplified protocol. Data was recorded from a Laerdal Resusci Anne Skillreporter manikin. A simulated emergency medical dispatcher, contacted by cell phone, delivered standardized instructions for both protocols. Outcomes included chest compression rate, depth, hand position, full release, overall proportion of compressions without error, time to start of CPR and total hands-off chest time. Proportions were analyzed by Wilcoxon's Rank Sum tests and time variables with Welch ANOVA and Wilcoxon's Rank Sum test. All tests used a two-sided alpha-level of 0.05. RESULTS: One hundred and seventeen subjects were randomized prospectively, 58 to the standard protocol and 59 to the simplified protocol. The average age of subjects in both groups was 25 years old. For both groups, the compression rate was equivalent (104 simplified versus 94 MPDS, p = 0.13), as was the proportion with total release (1.0 simplified versus 1.0 MPDS, p = 0.09). The proportion to the correct depth was greater in the simplified protocol (0.31 versus 0.03, p < 0.01), as was the proportion of compressions done without error (0.05 versus 0.0, p = 0.16). Time to start of chest compressions and total hands-off chest time were better in the simplified protocol (start time 60.9s versus 78.6s, p < 0.0001; hands-off chest time 69 s versus 95 s, p < 0.0001). The proportion with correct hand position, however, was worse in the simplified protocol (0.35 versus 0.84, p < 0.01). CONCLUSIONS: The simplified protocol was as good as, or better than the MPDS v11.2 protocol in every aspect studied except hand position, and the simplified protocol resulted in significant time savings. The protocol may need modification to ensure correct hand position. Time savings and improved quality of CPR achieved by the new set of instructions could be important in strengthening critical links in the cardiac chain of survival.     

Comparison of ventilation and cardiac compressions using the Impact Model 730 automatic transport ventilator compared to a conventional bag valve with a facemask in a model of adult cardiopulmonary arrest

PURPOSE: To determine the performance of two person CPR on an instrumented manikin by registered nurses using conventional bag valve mask (BVM) ventilation or the Impact Model 730 automatic transport ventilator (Impact 730, Impact Instrumentation, Inc., West Caldwell, NJ) in CPR mode using a face mask. DESIGN: Randomized crossover quasi-experimental. SETTING: Laboratory simulation. SUBJECTS: Twenty-eight registered nurses trained in performing adult cardiopulmonary resuscitation (CPR). INTERVENTIONS: Basic Life Support was provided by subjects using a conventional bag valve mask (BVM) ventilation or mask ventilation with an automatic transport ventilator, the Impact 730, which incorporates a metronome to facilitate chest compression timing. Subjects alternated performing 4min of CPR using the BVM or Impact 730 to deliver breaths with a mask while the other subject performed compressions. MEASUREMENTS AND MAIN RESULTS: Flow, volume and pressure were measured using a pneumotachograph and pressure transducer, and ease of use was measured using a 10cm visual analogue scale. There was no statistical or clinical difference between the actual and recommended tidal lung volume (mean+/-S.D.) delivered by the Impact 730 (-120.4+/-91.5ml) versus the BVM (-119.8+/-187.3+/-ml). Ventilation with the BVM resulted in more (137.7+/-143.9ml) air per breath passing through the simulated lower esophageal sphincter compared to the Impact 730 (14.0+/-16.8ml, p<0.05). The reduced mask leak per breath with the Impact 730 (176.1+/-98.3ml) compared to the BVM (367.6+/-337.7ml, p<0.05) is likely to have resulted from the subject being able to manage the mask with two rather than one hand and is reflected in the higher ease of use score on a 10cm visual analogue scale with the Impact 730 (8.06+/-1.35cm) versus the BVM (6.46+/-2.46cm, p<0.05). Subjects tended to deliver slightly more compressions and breaths when using the BVM. CONCLUSION: Compared to the BVM, the Impact 730 is as effective, easier to use and limits the amount of gas entering the stomach when used during adult CPR in a simulated setting.     

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.     

The impact of chest compression rates on quality of chest compressions - a manikin study

Purpose

Chest compressions are often performed at a variable rate during cardiopulmonary resuscitation (CPR). The effect of compression rate on other chest compression quality variables (compression depth, duty-cycle, leaning, performance decay over time) is unknown. This randomised controlled cross-over manikin study examined the effect of different compression rates on the other chest compression quality variables.

Methods

Twenty healthcare professionals performed 2 min of continuous compressions on an instrumented manikin at rates of 80, 100, 120, 140 and 160 min⁻¹ in a random order. An electronic metronome was used to guide compression rate. Compression data were analysed by repeated measures ANOVA and are presented as mean (SD). Non-parametric data was analysed by Friedman test.

Results

At faster compression rates there were significant improvements in the number of compressions delivered (160(2) at 80 min⁻¹ vs. 312(13) compressions at 160 min⁻¹, P < 0.001); and compression duty-cycle (43(6)% at 80 min⁻¹ vs. 50(7)% at 160 min⁻¹, P < 0.001). This was at the cost of a significant reduction in compression depth (39.5(10) mm at 80 min⁻¹ vs. 34.5(11) mm at 160 min⁻¹, P < 0.001); and earlier decay in compression quality (median decay point 120 s at 80 min⁻¹ vs. 40 s at 160 min⁻¹, P < 0.001). Additionally not all participants achieved the target rate (100% at 80 min⁻¹ vs. 70% at 160 min⁻¹). Rates above 120 min⁻¹ had the greatest impact on reducing chest compression quality.

Conclusions

For Guidelines 2005 trained rescuers, a chest compression rate of 100–120 min⁻¹ for 2 min is feasible whilst maintaining adequate chest compression quality in terms of depth, duty-cycle, leaning, and decay in compression performance. Further studies are needed to assess the impact of the Guidelines 2010 recommendation for deeper and faster chest compressions.     

牵引力对颈椎间盘作用的三维有限元分析

目的　比较不同牵引力对颈椎间盘的作用 ,从而获得有效的牵引条件。方法　通过建立颈椎三维有限元模型 ,使用MARCK72通用有限元分析软件计算 ,获得不同力量、不同角度的牵引条件下各颈椎间隙髓核部分的应力分布、体积改变 ,并进行分析。结果　在牵引力的作用下 ,髓核上产生不均匀的应力分布 ,最高应力出现在后部。髓核的前缘均略减小 ,后缘均略增宽。髓核的体积均略增大 ,且随牵引力、牵引角度的增加而增大 ,上部髓核体积的增大较下部明显 ,且增大率的差异较增大量更突出。结论　以前倾 3 0° ,90N牵引颈椎 ,可最大程度地增大髓核体积 ,利于间盘还纳     

Fully automatic rhythm analysis during chest compression pauses

Aim: Chest compression artefacts impede a reliable rhythm analysis during cardiopulmonary resuscitation (CPR). These artefacts are not present during ventilations in 30:2 CPR. The aim of this study is to prove that a fully automatic method for rhythm analysis during ventilation pauses in 30:2 CPR is reliable an accurate.Methods: For this study 1414 min of 30:2 CPR from 135 out-of-hospital cardiac arrest cases were analysed. The data contained 1942 pauses in compressions longer than 3.5 s. An automatic pause detector identified the pauses using the transthoracic impedance, and a shock advice algorithm (SAA) diagnosed the rhythm during the detected pauses. The SAA analysed 3-s of the ECG during each pause for an accurate shock/no-shock decision.Results: The sensitivity and PPV of the pause detector were 93.5% and 97.3%, respectively. The sensitivity and specificity of the SAA in the detected pauses were 93.8% (90% low CI, 90.0%) and 95.9% (90% low CI, 94.7%), respectively. Using the method, shocks would have been advanced in 97% of occasions. For patients in nonshockable rhythms, rhythm reassessment pauses would be avoided in 95.2% (95% CI, 91.6–98.8) of occasions, thus increasing the overall chest compression fraction (CCF).Conclusion: An automatic method could be used to safely analyse the rhythm during ventilation pauses. This would contribute to an early detection of refibrillation, and to increase CCF in patients with nonshockable rhythms.     

Comparison of ventilation and chest compression performance by bystanders using the Impact Model 730 ventilator and a conventional bag valve with mask in a model of adult cardiopulmonary arrest

"Bystanders" or lay persons are typically the first caregivers to attend to a victim of out-of-hospital cardiopulmonary arrest. Astronaut crew medical officers (CMO) play a similar role to bystanders aboard the International Space Station (ISS). Studies have demonstrated the importance of bystander cardiopulmonary resuscitation (BCPR) for patient survival before the arrival of emergency medical care. Recent apprehension from bystanders about the threat of contracting communicable diseases during BCPR, however, has led to the consideration of other ventilation systems such as the bag-valve mask (BVM) and automatic transport ventilators (ATV). BVM use is called for during CPR aboard the ISS. This study evaluated the ventilation and compression performance of 40 basic CPR-trained bystanders using either a BVM (adult-sized self-inflating bag with face mask) or an ATV (Model 730 ventilator (M730), Impact Instrumentation, Inc., West Caldwell, NJ). Each two-bystander team gave BCPR to a simulated cardiopulmonary arrest victim using the 2-breath/15-compression cycle for 4 min and then switched roles for another 4-min interval. Compared to BVM use, the M730 led to significantly (p<0.05) lower number of breaths, smaller tidal volumes, airway flows, airway pressures, volume of gas entering the stomach per breath and chest compressions for the 4-min period. The M730 also enabled a bystander to meet the recommendation of 4-breath and compression cycles per minute as per Guidelines 2000. Lastly, ease-of-use scores were significantly higher for the M730 compared to the BVM. Overall, the data suggest that the M730 improves the quality of performance for a bystander performing BCPR.