HIV-1 selection by epidermal dendritic cells during transmission across human skin.

Macrophage tropic HIV-1 is predominant during the initial viremia after person to person transmission of HIV-1 (Zhu, T., H. Mo, N. Wang, D.S. Nam, Y. Cao, R.A. Koup, and D.D. Ho. 1993. Science. 261:1179-1181.), and this selection may occur during virus entry and carriage to the lymphoid tissue. Human skin explants were used to model HIV-1 selection that may occur at the skin or mucosal surface. Macrophage tropic, but not T cell line tropic strains of HIV-1 applied to the abraded epidermis were recovered from the cells emigrating from the skin explants. Dermis and epidermis were separated by dispase digestion after virus exposure to determine the site of viral selection within the skin. Uptake and transmission to T cells of all HIV-1 isolates was found with the dermal emigrant cells, but only macrophage tropic virus was transferred by emigrants from the epidermis exposed to HIV-1, indicating selection only within the epidermis. CD3+, CD4+ T cells were found in both the dermal and epidermal emigrant cells. After cell sorting to exclude contaminating T cells, macrophage tropic HIV-1 was found in both the dermal emigrant dendritic cells and in dendritic cells sorted from the epidermal emigrants. These observations suggest that selective infection of the immature epidermal dendritic cells represents the cellular mechanism that limits the initial viremia to HIV-1 that can use the CCR5 coreceptor.

Heparin therapy: a simpler test of control.

A bedside test of heparin activity (whole blood activated partial thromboplastin time) was assessed during clinical control of anticoagulation. It correlated closely (r = 0.94) with the whole blood clotting time but had a number of advantages.

Four-step CPR--improving skill retention.

This study is an attempt to see if simplifying the teaching of basic life support leads to better skill acquisition and retention. Forty-eight lay volunteers received instruction in CPR; 24 were taught the standard 8-step sequence whereas 24 were taught a simplified 4-step sequence. Tests of performance were carried out on a manikin before and after training. Those in the 4-step group were significantly better than those in the 8-step group at remembering the sequence of skills immediately after training (P = 0.04), 1 week later (P < 0.001) and at 6 weeks (P < 0.001). Twenty-three out of the 24 volunteers in the 4-step group got the sequence completely correct each time they were tested, in contrast to only 2 out of the 24 in the 8-step group. There was no difference, however, in the quality of performance of the skills between the two groups. In addition, it was shown that use of the 4-step sequence should result in a useful reduction in the time taken before a rescuer calls for the emergency services and commences CPR. Whether such a radical change in teaching should be introduced is a matter for further discussion and research.

The relationship between rate of chest compression and compression:relaxation ratio.

One of the arguments put forward in support of a relatively fast rate of chest compression during CPR, is that it facilitates the achievement of a high compression:relaxation ratio. This has been shown to increase blood flow. In this study a group of volunteers carried out chest compression at the rate that each felt was correct and comfortable. There was no significant relationship between compression rate and compression:relaxation ratio. In a second study volunteers carried out chest compression on a manikin at rates of 40/min; 60/min; 80/min and 100/min. There was no significant rate related difference in the compression:relaxation ratios recorded. The ability to achieve a high compression duration is not related to compression rate, and should not be a consideration when guidelines on CPR are revised.

European Resuscitation Council Guidelines 2000 for Adult Basic Life Support. A statement from the Basic Life Support and Automated External Defibrillation Working Group(1) and approved by the Executive Committee of the European Resuscitation Council.

The European Resuscitation Council (ERC) last issued guidelines for Basic Life Support (BLS) in 1998 [1]. These were based on the "Advisory Statements" of the International Liaison Committee on Resuscitation (ILCOR) published in 1997 [2]. Following this, the American Heart Association, together with representatives from ILCOR, undertook a series of evidence-based evaluations of the science of resuscitation [3] which culminated in the publication of "Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" in August 2000 [4,5]. The Basic Life Support and Automated External Defibrillation Working Group (BLS&AED Group) has considered this document and has recommended changes in the ERC BLS guidelines. These are presented in this paper.

European Resuscitation Council Guidelines 2000 for Automated External Defibrillation. A statement from the Basic Life Support and Automated External Defibrillation Working Group(1) and approved by the Executive Committee of the European Resuscitation Council.

The European Resuscitation Council (ERC) last issued guidelines for Automated External Defibrillators (AEDs) in 1998 [1]. The American Heart Association, together with representatives from the International Liaison Committee on Resuscitation (ILCOR), then undertook a series of evidence-based evaluations of the science of resuscitation [2] which culminated in the publication of "Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" in August 2000 [3,4]. The Basic Life Support and Automated External Defibrillation Working Group (BLS&AED Working Group of the ERC) has considered this document and has recommended changes in the ERC AED guidelines. These are presented in this paper.

Randomised controlled trials of staged teaching for basic life support: 2. Comparison of CPR performance and skill retention using either staged instruction or conventional training.

Teaching CPR in stages is a strategy designed to improve skill acquisition and retention. This method has been compared with conventional teaching in a randomised trial involving 495 volunteers. The first ('bronze') stage was simplified by omitting ventilation and giving compressions in sets of 50 with pauses to open the victim's airway; in the second ('silver') stage ventilation was introduced in a ratio of 50 compressions to five breaths, and in the third ('gold') stage, the volunteers were converted to conventional CPR. 51% of those taught by this method reattended for the second ('silver') stage compared with 25% who were taught conventional CPR and advised to return for a revision session. 38% of the staged group reattended for the third ('gold') compared with 8% for the conventional group. Modest improvement in skill acquisition has earlier been reported for the 'bronze' stage teaching, and this has been followed by better performance in some of the components tested after the subsequent stages. Comparisons after the 'gold' stage were limited by the small numbers who reattended for a third session of conventional training, but no special difficulties were noted in changing the ratio of compressions to ventilation that was necessary to convert the staged training volunteers to conventional CPR. The increased number of compressions that can be achieved by teaching 'bronze' stage CPR with no ventilation was retained, to a lesser degree, when the 'silver' ratio of 50 compressions to five breaths was compared with the conventional 15:2 ratio. Our observations suggest that during the first critical 8 min of a resuscitation attempt, 58% more compressions might be delivered by using the 50:5 ratio - an increase that is likely to result in a significant augmentation of blood flow with important clinical implications. More comparative information will become available when the results of unannounced home testing are analysed.

Randomised controlled trials of staged teaching for basic life support. 1. Skill acquisition at bronze stage.

We have investigated a method of teaching community CPR in three stages instead of in a single session. These have been designated bronze, silver, and gold stages. The first involves only opening of the airway and chest compression with back blows for choking, the second adds ventilation in a ratio of compressions to breaths of 50:5, and the third is a conversion to conventional CPR. In a controlled randomised trial of 495 trainees we compared the performance in tests immediately after instruction of those who had received a conventional course and those who had had the simpler bronze level tuition. The tests were based on video recordings of simulated resuscitation scenarios and the readouts from recording manikins. Differences occurred as a direct consequence of ventilation being required in one group and not the other, some variation probably followed from unforeseen minor changes in the way that instruction was given, whilst others may have followed from the greater simplicity in the new method of training. A careful approach was followed by slightly more trainees in the conventional group whilst appreciably more in the bronze group remembered to shout for help (44% vs. 71%). A clear advantage was also seen for bronze level training in terms of those who opened the airway as taught (35% vs. 56%), for checking breathing (66% vs. 88%), and for mentioning the need to phone for an ambulance (21% vs. 32%). Little difference was observed in correct or acceptable hand position between the conventional group who were given detailed guidance and the bronze group who were instructed only to push on the centre of the chest. The biggest differences related to the number of compressions given. The mean delay to first compression was 63 s and 34 s, and the mean duration of pauses between compressions was 16 s and 9 s, respectively. Average performed rates were similar in the two groups, but more in the conventional group compressed too slowly whereas more in the bronze group compressed too rapidly. Observations were made for only three cycles of compression, but extrapolating these to the 8 min often considered a watershed for chances of survival for victims of cardiac arrest, an average of 308 compressions would be expected from those using conventional CPR compared with 675 for those using bronze level CPR. The implications of this difference are discussed.

A rationale for staged teaching of basic life support.

Basic life support is a crucial part of the Chain of Survival. Unfortunately, however the skill is complex and cannot readily be acquired--let alone retained--in the course of a single training session. Although the problem has long been recognised, no new strategies have been widely implemented to counter the problem. We believe that staged teaching of CPR might provide a solution, and we have devised a program to test this new method. It involves three stages of instruction that we have called bronze, silver, and gold standards. The bronze standard involves opening the airway and providing chest compression without active ventilation: this alone may widen the window of opportunity for successful defibrillation in adult victims in out-of-hospital cardiac arrest. Ventilation is introduced at silver stage using a ratio of 50:5, with emphasis on its value in the resuscitation of children being used as motivation to bring people back for a second period of instruction. The gold stage teaches conventional CPR. A pilot study has been encouraging and a randomized trial on skill acquisition and skill retention is planned.

BCLS.

The combined American Heart Association and ILCOR publication, International Guidelines 2000, presents a wealth of scientific data on the management of victims before, during and after cardiopulmonary resuscitation. By reference to this publication, individual National Resuscitation Councils can develop their own guidelines for basic and advanced and paediatric life support in the knowledge that they will be following uniform, international guidelines.

ACLS.

It must be emphasised that the published International Guidelines 2000 contain an in-depth presentation of the scientific evidence behind advanced life support. The exact interpretation of this evidence, and the algorithms adopted by a national resuscitation council will depend upon various factors such as local interpretation of the evidence, local practice and availability of drugs. The ERC is publishing its own summaries of the guideline changes and the sequences of action for both BLS and ALS and these papers are recommended for further reading.