Mechanical external chest compression: a new adjuvant technology in cardiopulmonary resuscitation. Yves Maule Head Nurse Accident and Emergency Dept and SMUR 1 Brugmann University Hospital, Paul Brien Site
Translation of French article in Urgences & Accueil, Volume 7, Numéro 29, Juin-JuilletAoût 2007
Introduction Up to the end of the 1990s, cardiopulmonary resuscitation was synonymous with manual chest compression, which had been shown to be quite effective but which was primarily dependent on the operator's skill and physical stamina, and the length of time compressions were performed for. A number of studies 2 had shown that compression quality deteriorated with duration, and in any case it was only possible to achieve low levels of cardiac blood flow capable of maintaining basic perfusion of vital organs. Trials of manual devices 3 had not demonstrated any striking improvement in the quality of resuscitation.
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SMUR = Service Mobile d'Urgence et de Réanimation = emergency ambulance service (with a crew that includes a doctor) 2 Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min A. Ashton, A. McCluskey, C.L. Gwinnutt, A.M. Keenan, Resuscitation 55 (2002) 151_/155 3 Cardiopump®
External chest compression: the Lund Experience At the end of the 1990s, a Swedish cardiothoracic surgeon 4 realised that the number of heart operations was reducing in relation to the increasing performance of noninvasive cardiology, and decided to refocus his work on transplantation. Accordingly, he developed a procedure for storing and reconditioning organs and was trying to find a way of maintaining cardiac blood flow by means of noninvasive mechanical external chest compression to get patients in refractory cardiac arrest to hospital for possible organ harvesting. His aim was therefore to increase the opportunities for organ harvesting by recruiting more potential donors. As CPB 5 could not be used in an out-of-hospital setting, he developed the first prototype of the LUCAS® system (Lund University Cardiac Assist System). Laboratory tests on an animal model produced excellent results as the system made it possible to maintain near-normal coronary perfusion, in addition to much better blood flows to organs than those obtained using traditional manual chest compression. During the animal studies, Professor Steen’s team noticed something remarkable: they found that the chest compression produced by the system was so effective and regular that it usually resulted in resumption of spontaneous heart rhythm and improved the success rate for defibrillation on a heart that had been in fibrillation for several minutes. At this point the team revised its development objectives and continued the research, but focusing on resuscitation rather than transplantation.
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Professor Stig Steen, Department of Cardiothoracic Surgery Lund University Sweden 5 Cardiopulmonary bypass
Other similar systems As might be expected, other companies are moving in the same direction and have developed external chest compression systems, with varying degrees of success. In many cases, the difference between them is the compression mechanism or the power source. Comparative studies are currently under way in a number of centres to establish how efficient the various systems are. The rest of this article will deal mainly with the LUCAS® system as it is known to the author and is currently being used successfully.
The LUCAS® system The LUCAS is a pneumatic mechanical system which performs a hundred chest compressions/decompressions a minute, just like manual chest compression but with one additional decompression and a constant compression force of 500N. The device is easy to apply around the chest of almost all adult patients, taking caregivers very little time and using very little energy, so interrupting manual chest compression for only a very short time (less than 10 seconds) before taking over from it. The device is light and made of synthetic, easy-tomaintain materials, and is simple and intuitive to use.
External chest compression using the LUCAS® device: Brugmann University Hospital’s experience At the end of 2004, the company developing the system asked us if we would test it. They asked us because of our existing collaboration in the field of defibrillation,
the volume of patients treated by our SMUR unit (2400 missions a year) and above all, the large number of cardiac arrests treated during the last few years (± 180 cardiac arrests/year); this gave our prehospital team considerable experience in the field of advanced resuscitation. The original objective was not to assess the system’s performance but to evaluate the possibility of using it in an out-of-hospital setting. To do this, we set up a working group of doctors and nurses to look at a number of aspects of the use of the system, namely ethics, logistics and our ability to incorporate the system into our normal practice. •
Ethics: was the device experimental? Had the system been validated by other centres? Did we risk reducing the chances of survival of patients who were already at-risk?. Ought we to change our practice with regard to duration of resuscitation? As it was possible to transport patients while the LUCAS® was being used, should we continue CPR while taking them to hospital? What should the family be told, given the size and unfamiliarity of the device? All these questions had to be answered. With regard to validation by other teams, we did a literature search and realised that there had actually been few studies, but that they were very encouraging. The system had been in use in Sweden since 2000 with some considerable success, reported in a number of publications. The United Kingdom had begun to use it in 2002. With regard to duration of CPR, after some discussion of conflicting views, both doctors and nurses decided not to continue resuscitation any longer than we had
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been doing previously, i.e. 30 minutes of CPR except in very precisely-defined cases such as hypothermia or post-infarction fibrinolysis, in other words, cases in which transport to hospital could be seen as beneficial to the patient. Finally, with regard to explaining to the patient’s family, the use of the LUCAS® freed up time which had previously been used for chest compression, so we decided to use this time to improve the quality of our work and also to look after the family, which had not previously been possible. Logistics: the system uses a large amount of compressed air. We could have used our portable oxygen cylinders as a power source, but we felt that the risk of discharging a large amount of oxygen around the resuscitation team (the LUCAS® uses 70 L/minute of gas) was too high, and we decided to use compressed air. Another problem was finding space for the equipment in the emergency vehicles, and to ensure stable supplies from a company external to the hospital. Incorporating the system into normal practice: the system required one additional backpack and a portable cylinder to be carried, in addition to a defibrillator and a resuscitation bag. The SMUR team consists of a nurse and a doctor, which limits the weight of equipment that can be carried. It was therefore not realistic to take all this equipment to each callout. The solution decided on was to follow a protocol based on the few data that we obtained during the call. If the fact that the patient was unconscious was mentioned, we carried the LUCAS® to the patient at
once, in addition to the usual equipment. If the patient had been found in cardiac arrest and we did not have the LUCAS®, we did not waste time fetching it, but performed a standard resuscitation procedure.
Our experience showed that the system had the following benefits: •
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Increased regularity and quality of compressions as confirmed by the physiological values measured during resuscitations (systolic blood pressure could be measured during CPR with the LUCAS®, while this is hardly ever possible during classical manual CPR; SaO2 readings of around 95%, patients showing signs of life again (moving, etc) while they were still in ventricular fibrillation or had a heart rhythm that produced no blood flow. It is possible to envisage moving the patient while maintaining optimum compression quality, which is not the case with manual CPR. So it becomes possible to take the patient to hospital so that they can benefit from an invasive procedure not available in an out-of-hospital setting, although we have only tried this in two or three very specific cases, and with a very restricted field of application. Better use of human resources during resuscitation. The caregiver formerly occupied with performing CPR is released from the CPR post by the system. They can then be used for other activities beneficial to the patient.
The LUCAS® / Brugmann University Hospital study: basic premises As we wanted to assess the possibility of using the LUCAS® in an out-of-hospital setting, we established a usage registry. After correlating the records of our use of the LUCAS® with the results of our resuscitations, it became clear after 50 uses that the system was producing more cases of ROSC 6 . At this point, reluctant to be carried away too much by these results, we decided to continue the study while refocusing it a little more on achieving ROSC. We therefore decided to include 150 patients resuscitated using the LUCAS® system and to compare the data collected with historical data from 2004, when we did not have the system. At the initiative of the nursing team, a research database has been kept updated since the SMUR unit was established in 2003 and our defibrillator recordings have been archived, which enabled us to obtain reliable data even though they had not originally been recorded for research purposes. The personnel involved, territory covered, and intervention times were similar in both cohorts. However, a change in the guidelines at the end of 2005 posed a problem as it could have led to bias in the study.
Was the improvement in ROSC levels due to the change in the guidelines at the end of 2005, or to the use of LUCAS®? After discussion, we could not ethically justify carrying out a randomised trial, and the solution was found from within our working practice: we noticed that since introducing the LUCAS®, there had been interventions during which it had been used 6
Return Of Spontaneous Circulation
straight away (the LUCAS® was taken to the patient straight away when the initial call mentioned that they were unconscious), and others when the call provided only insufficient or incomplete data and the patient had been resuscitated in the conventional manner but in accordance with the 2005 guidelines, as they had been discovered by chance in cardiac arrest or had gone into cardiac arrest during management. So, by comparing this arm of the study with our 2004 data, if the figures obtained were virtually the same in both cohorts it would mean that application of the new guidelines was not the reason for the significant difference in ROSC levels observed. And in fact, this is what our data analysis showed.
Brugmann University Hospital study: the figures
C1: historical data 2004. n=140 ROSC No ROSC
31 (22.14%) 109 (77.86%)
C2: LUCAS® study n=150 Group 1: ROSC LUCAS® used No ROSC n=123 Group 2: ROSC LUCAS® not available n=27 No ROSC
71 (57.7%) 52 (42.2%) 7 (25.9%)
20 (74.1%)
In graphic form Conclusions •
Comparison between the 2 cohorts (ROSC / No ROSC) as % 74.10%
77.80%
57.70% 42.20% 25.90% 22.14%
C1
80.00% 60.00% 40.00% 20.00%
C1 C2 Gp 1 C2 Gp 2
0.00% C2 Group 2 C2 Group Cohorts
Notes: The front row shows ROSC observed in cohort C1 and in both arms of C2. Cases of no ROSC are shown at the back. There are few differences between C1 and C2 Group2. For C2 Group2, cases of ROSC were those observed during the period when the system was being evaluated, but when it was not being used because it was not available. These figures suggested that there was no bias in the study following the introduction of the new ERC guidelines at the end of 2005, as the figures with and without the new guidelines are very similar. However, when these figures are compared with those obtained with the LUCAS® (C2 Group1), it becomes clear that almost 2.5 times as many ROSC were achieved with the system than with manual CPR as practised in C1 or in C2 Group2. Mean age in the 3 groups was 68.5 ± 2.5 years, so this uniformity guarantees an absence of bias; male/female distribution was 67% ± 3% males in all 3 groups, which was equally uniform. To make the figures more realistic, we compared the same periods for 2004/2005 with those for 2005/2006.
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Our experience shows that while mechanical external chest compression is not a universal panacea, it is an important addition to the treatment employed in cardiopulmonary resuscitation, like moderate hypothermia. All this study shows at the moment is that this type of device achieves more ROSC, but we do not have enough follow-up to assess the long-term survival of these patients or their quality of life on discharge from the intensive care unit. Clearly a unit should think carefully about the ethical aspects before adopting this type of device, to prevent Accident and Emergency units from turning into improvised mortuaries where patients in refractory cardiac arrest under mechanical chest compression are brought to be declared dead. In addition, this system is just one link in the chain of survival; teaching the public BLS 7 should remain the primary concern, together with automatic defibrillation for the general public. Without early manual resuscitation, the LUCAS® cannot provide much assistance to a brain already irremediably damaged by hypoxaemia caused by deficient blood supply to the brain. In the same vein, we found that the earlier the system is introduced, the more convincing the results seem to be. In 90% of interventions, an ambulance crew arrives at the scene a few minutes before we do and therefore one option would be to make this technology available to these first-
Basic Life Support
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line teams, as happens already in Sweden and in the United Kingdom. We became aware that our findings did not include any data on longterm benefit to the patient, se we decided to start again with a new cohort of 150 patients for whom we will try to obtain post-intensive care status at 3 months, 6 months and one year. This study carried out in our unit has been primarily supported by the nursing team, not because the doctors were not interested in the topic but rather because most of the implementation was done by the nursing team. Within our unit, this research has prompted a reexamination of nursing practices in the context of resuscitations, which makes us feel that it proved to be an opportunity for the whole team; this new approach to our work is now beginning to extend to other sectors beyond that of resuscitation in an out-of-hospital setting. So as "coach" to this team, I feel that this research work has been doubly beneficial to us. I would add that the fact that the study prompted discussions between doctors and nurses has brought the two professions even closer together than they were before.
References: The effect of rescuer fatigue on the quality of chest compressions Ochoa et al., Resuscitation 37 (1998) 149–152 Quality of cardiopulmonary resuscitation during out of hospital cardiac arrest Wik et al, JAMA, January 19, 2005, Vol.293 No.3 Hightower et al; Decay in quality of closed-chest compression over time; Ann Emerg Med 1995;26:300-303
Ashton et al; Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min; Resuscitation 55 (2): 147-157 Aufderheide et al; Incomplete chest wall decompression: A clinical evaluation of CPR; performance by trained laypersons and an assessment of alternative manual chest compressiondecompression techniques; Resuscitation. 2006 Oct 26 Abella, et al; Circulation Chest Compression Rates During Cardiopulmonary Resuscitation Are Suboptimal; February 1, 2005 Coronary perfusion pressure and the return of spontaneous circulation in human cardiopulmonary resuscitation. Paradis et al: JAMA 1990;263:11061113 The critical importance of minimal delay between chest compressions and subsequent defibrillations: a haemodynamic explanation Steen et al, Resuscitation 58 (2003); 249-258 Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation. Wik et al, JAMA, March 19, 2003-vol 289 no. 11. Cobb et al; JAMA, 1999, 281:1182-8; Influence of cardiopulmonary resuscitation prior to defibrillation in patients with out of hospital ventricular fibrillation Edelson et al; Resuscitation Resuscitation 71 (2006) 137-145; Effects on compression depth and pre.shock pauses predict defibrillation failure during cardiac arrest Kern et al; Resuscitation 58 (2003) 273-274; Limiting interruptions of chest compressions during cardiopulmonary resuscitation Rea et al; Circulation 2006 Dec 11; Increasing Use of Cardiopulmonary Resuscitation During Out-ofHospital Ventricular Fibrillation Arrest. Survival Implications of Guideline Changes Evaluation of LUCAS, a new device for automatic mechanical chest compression and active decompression for cardiopulmonary resuscitation. Steen et al, Resuscitation 2002; 55:285-299 Clinical consequences of the introduction of mechanical chest compression in the EMS system for treatment of out-of-hospital cardiac arrest—– A pilot study Axelsson et al, Resuscitation (2006) 71, 47-55 Increased restoration of spontaneous circulation after cardiac arrest with the LUCAS device compared to manual chest compressions – A pilot study Rubertsson et al, Resuscitation (2006) 69, 46 (Abstract) Mechanical Chest Compressions in a Patient with Left Main Closure during PCI Olivecrona, Case Study – published at TCTmd.com 24th of October 2006
