LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY
Asta Krikščionaitienė
THE QUALITY OF CHEST COMPRESSIONS:
IMPLEMENTATION AND EVALUATION OF THE
EXPERIMENTAL FOUR-HAND METHOD
Doctoral Dissertation Biomedical Sciences,
Medicine (06B)
The dissertation is defended extramurally Scientific Consultant
Prof. Dr. Dinas Vaitkaitis (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B)
Dissertation is defended at the Medical Research Council of the Medical Academy of Lithuanian University of Health Sciences
Chairperson
Prof. Dr. Andrius Macas (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B)
Members
Prof. Dr. Antanas Gulbinas (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B)
Prof. Dr. Rūta Jolanta Nadišauskienė (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B) Prof. Dr. Pranas Šerpytis (Vilnius University, Biomedical Sciences, Medicine – 06B)
Assoc. Prof. Dr. Anita Villerusa (Riga Stradins University (Latvia), Biomedical Sciences, Public Health – 09B)
Dissertation will be defended at the open session of the Medical Research Council of Lithuanian University of Health Sciences on the June 30th, 2015 at 1 p.m. in 204 auditorium of Faculty of Pharmacy of Lithuanian University of Health Sciences.
LIETUVOS SVEIKATOS MOKSLŲ UNIVERSITETAS MEDICINOS AKADEMIJA
Asta Krikščionaitienė
KRŪTINĖS LĄSTOS PASPAUDIMŲ KOKYBĖS
TYRIMAS, TAIKANT EKSPERIMENTINĘ
KETURIŲ RANKŲ METODIKĄ
Daktaro disertacija Biomedicinos mokslai,
medicina (06B)
Disertacija ginama eksternu Mokslinis konsultantas
prof. dr. Dinas Vaitkaitis (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)
Disertacija ginama Lietuvos sveikatos mokslų universiteto Medicinos akademijos medicinos mokslo krypties taryboje
Pirmininkas
prof. dr. Andrius Macas (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)
Nariai
prof. dr. Antanas Gulbinas (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)
prof. dr. Rūta Jolanta Nadišauskienė (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)
prof. dr. Pranas Šerpytis (Vilniaus universitetas, biomedicinos mokslai, medicina – 06B)
doc. dr. Anita Villerusa (Rygos Stradins universitetas (Latvija), biomedicinos mokslai, visuomenės sveikata – 09B)
Disertacija bus ginama viešame Medicinos mokslo krypties tarybos posėdyje 2015 m. birželio 30 d. 13 val. Lietuvos sveikatos mokslų universiteto Farmacijos fakulteto 204 auditorijoje.
Skiriu savo tėvams
Arvydui ir Ramutei Ališauskams Dedicated to my parents
CONTENTS
ABBREVIATIONS ... 9
INTRODUCTION ... 11
ORIGINALITY AND NOVELTY OF THE STUDY ... 13
AIM AND OBJECTIVES OF THE STUDY ... 14
1. REVIEW OF LITERATURE ... 15
1.1.Cardiac arrest... 15
1.1.1. Definition and epidemiology ... 15
1.1.2. Outcome ... 15 1.1.3. Chain of survival ... 17 1.2.Cardiopulmonary resuscitation (CPR) ... 18 1.2.1. History of CPR ... 18 1.2.2. Elements of CPR ... 19 1.2.3. Regulation of CPR ... 21 1.2.4. Bystander CPR ... 21 1.2.5. Hands-only CPR ... 22 1.2.6. Dispatcher-assisted CPR ... 23 1.3.Quality ofCPR ... 24 1.3.1. Significance of CPR quality ... 24
1.3.2. Main CPR quality determinants ... 25
1.3.3. Factors related to CPR quality ... 28
1.4.CPR training ... 35
2. METHODS ... 37
2.1.Study design and population... 37
2.1.1. The quality of the chest compressions in LUHS students (Study I) ... 37
2.1.2. Effects of the Andrew‘s manoeuvre on CC quality in LUHS students (Study II) ... 39
2.1.3. Effects of the Andrew‘s manoeuvre on CC quality in lay rescuers (Study III) . 40 2.2.Statistical analysis... 42
2.2.1. Study I ... 42
2.2.3. Study III ... 43
3. RESULTS ... 45
3.1.Characteristics of the participants ... 45
3.1.1. Study I ... 45 3.1.2. Study II ... 48 3.1.3. Study III ... 50 3.2.Main results ... 52 3.2.1. Study I ... 52 3.2.2. Study II ... 57 3.2.3. Study III ... 61 4. DISCUSSION ... 65
4.1.Quality of the chest compressions in the context of guidelines 2010... 65
4.2.Lightweight rescuers and the quality of chest compressions ... 66
4.3.Impact of the andrew’s manoeuvre on the chest compresions depth ... 72
4.4.Dispatcher-assisted cpr: improving bystander cpr quality ... 76
4.5.The importance of the female rescuers’ cpr quality... 81
4.6.Interaction between different cpr quality determinants... 81
LIMITATIONS OF THE STUDY ... 85
CONCLUSIONS ... 86
PRACTICAL RECOMMENDATIONS ... 87
REFERENCES ... 88
LIST OF PUBLICATIONS ... 112
Publications related to the results of dissertation (peer review) ... 112
Other publications... 112
LIST OF SCIENTIFIC CONFERENCES ... 113
SANTRAUKA... 121
CURRICULLUM VITAE ... 133
ABBREVIATIONS
AED Automated external defibrillatorAHA American Heart Association AID Automatinis išorinis defibriliatorius AKS Arterinis kraujo spaudimas
ALS Advanced life support
BCPR Bystander Cardiopulmonary Resuscitation BLS Basic life support
BMI Body mass index CA Cardiac Arrest CC Chest compressions
CCF Chest compression fraction CPR Cardiopulmonary Resuscitation
DA-CPR Dispatcher-assisted Cardiopulmonary Resuscitation ECC Emergency Cardiovascular Care
EGT Europos gaivinimo taryba EMS Emergency Medical Service ERC European Resuscitation Council GMP Greitoji medicinos pagalba
GUIDELINES Resuscitation guidelines from AHA and ERC HO-CPR Hands-only Cardiopulmonary Resuscitation
IHCA In-hospital cardiac arrest
ILCOR International Liaison Committee on Resuscitation IQR Interquartile range
KLP Krūtinės ląstos paspaudimai KMI Kūno masės indeksas
LUHS Lithuanian University of Health Sciences MED Medical emergency dispatcher
MPCD Mean proportion of correct chest compression depth MPDS Medical Priority Dispatch System
OHCA Out-of-hospital cardiac arrest ROSC Return of Spontaneous Circulation SD Standard deviation
ST-CPR Standard Cardiopulmonary Resuscitation (compressions plus ventilation)
ŠSD Širdies susitraukimų dažnis VF Ventricular Fibrillation VT Ventricular Tachycardia VSI Video self-instruction
INTRODUCTION
Cardiovascular disease is the most common cause of death amongst adult. Worldwide, there are >135 million cardiovascular deaths each year (1). Most cardiac arrests (CA) in adults are sudden, resulting from a primary cardiac cause; circulation produced by chest compressions (CC) is therefore paramount (2). Better resuscitation saves more lives. As outlined by the American Heart Association (AHA), ‘better resuscitation’ is closely related to ‘better chest compressions’ (3). Chest compressions deliver only 10-30% of normal cardiocerebral flow, even when optimally performed. Rather than minimizing the importance of compressions, this underscores that there is no room for suboptimal performance (3).
However, cardiopulmonary resuscitation (CPR) quality varies between providers and remains poor. Even health care professionals perform CC with shallower-than-recommended depths, as shown in previous clinical CPR studies in both in-hospital and out-of-hospital settings (4, 5). Potentially serious consequences can result from administering CC of insufficient depth: low CC depth is associated with suboptimal haemodynamics and poor outcomes after cardiac arrest (6-8). Following the International Consensus on Science and Treatment Recommendations on Resuscitation, the European Resuscitation Council (ERC) Guidelines 2010 for CPR (Guidelines) have increased the recommended CC depth from 38–50 mm to 50–60 mm, and the CC rate from 90–100 per min, to 100–120 per min (9, 10). The task is more difficult than previous guideline requirements. Still little is known about rescuer’s ability to perform CC according to the newest guidelines. There is no published studies on CPR quality from any settings in Lithuania. Some authors refer that the average rescuer on an ambulance crew can achieve adequate compression depth in a significant majority of women, but in only a relatively small percentage of men, who represent the majority of all out-of-hospital cardiac arrest (OHCA) victims (11). However, there is a controversy concerning gender differences in CC quality (11-14). Therefore, we hypothesised that it is more difficult to achieve the Guidelines 2010 requirements for the CC quality in comparison with previous requirements. We tested the first hypothesis in the Study I.
Understanding the reasons for variation in CPR quality may lead to improved BLS training methods and eventually improve CPR outcome. Little is known about relationship between CC quality and adult rescuer’s anthropometric characteristics. Most of the published data are retrieved from the small sample sizes (12) or children studies (15-17). We stated that
there is a relationship between adult rescuers’ anthropometric characteristics (weight, height, BMI) and CC quality data. The second hypothesis was tested in the Study I and II.
The largest group of OHCA occurred in males over the age of 60 at home, and accordingly, the most likely witness, if any, is the spouse or family member, most frequently an older woman (18-20). Most cardiac arrests in hospitals are witnessed by female nurses, whose key role in such emergency is to apply initial CPR. Based on the results from the Study I, we investigated new strategies to improve CC quality of the female rescuers. We hypothesised that our experimental four-hand CC method called Andrew’s manoeuvre could improve the quality of CCs in female students. The third hypothesis was tested in the Study II.
Overall, bystander-initiated cardiopulmonary resuscitation (CPR) is a vital link in improving survival for OHCA victims (21). Approximately 67% of cardiac arrest victims are first witnessed by bystanders (22). Less than 1% of patients who are not resuscitated in the field will leave the hospital alive (23). Medical emergency dispatcher (MED) telephone instructions to callers increase bystander CPR rates (24-26) and survival (24, 25) after OHCA. Recent data provide strong support for long-term mortality benefit of a dispatcher CPR instruction strategy consisting of chest compression alone rather than compression plus rescue breathing among adult patients with OHCA (27). However, hands-only cardiopulmonary resuscitation (HO-CPR) by itself seems to be more physically demanding than conventional 30:2 cardiopulmonary resuscitation (30:2 CPR) (28-31). Current guidelines recommends to push the chest to a depth of 50-60 mm (9), which is more difficult to achieve (31-35) not only for young motivated medical students (31-33), but even for health care professionals (34, 35).
In Kaunas region all the callers are instructed to perform dispatcher-assisted CPR (DA-CPR) using standard Medical Priority Dispatch System (MPDS) ProQA® cardiac arrest protocol from 2011. None of the studies examined the CC quality of untrained elderly laypeople in DA-CPR. On the basis of the Study’s II results, we hypothesized that deeper CCs could be reached using four hands during dispatcher-assisted CPR. Thus, the fourth hypothesis of the dissertation was that experimental four-hand CC method could improve the quality of CCs in the setting of the simulated dispatcher-assisted CPR in elderly lay-people population who are most likely to witness cardiac arrest (20).
influencing survival from cardiac arrest (3, 9, 36, 37), and there is still room for improvement.
Originality and novelty of the study
We were the first to conduct and publish the research on quality of chest compressions in Lithuania. There were only few studies published before our Study I, in which the relationship between adult rescuer’s anthropometric data and CC quality were evaluated (12, 38). Our study presented new information about the relationship between the female rescuer’s weight and CC depth.
Our group was among the first in the research community to identify the issue that it could be more difficult for female rescuers to achieve the required CC depth in accordance with the Guidelines 2010 in comparison to male rescuers (39). Such a statement was supported by later findings from other authors (31, 33).
To the best of our knowledge, the Study III was the first reported randomized controlled study that analysed the effectiveness of four-hand CC method for the quality of CCs in the presence of multiple rescuers. The original four-hand CC method or Andrew’s manoeuvre (pushing on the shoulders of the person while he/she performs CCs) was invented and first described in 2014 by our team (40). We raised a simple new old question: ‘How many hands do we need to achieve the required CC depth according to Guidelines 2010?’ One (41), two (42), three (43) or four (40)?’ Modification of the Andrew’s manoeuvre was successfully used by other authors (43) who repeated our experiment and published similar results about the improved quality of CCs.
Yet more, the results of the Andrew’s manoeuvre studies open the door for further investigations of this four-hand CC method in a clinical setting.
AIM AND OBJECTIVES OF THE STUDY
Aim of the study
The aim of the study was to evaluate the quality of chest compressions in adults using standard two-hand and experimental four-hand chest compression method.
Objectives of the study
1. To assess the quality of chest compressions after standard video self-instructional basic life support training in the Lithuanian University of Health Sciences (LUHS) students according to European Resuscitation Council 2010 guidelines.
2. To evaluate the associations between rescuers’ anthropometric characteristics (weight, height, body mass index) and the quality of chest compressions among the LUHS students.
3. To study the effects of the Andrew’s manoeuvre – an experimental four-hand chest compressions method on the quality of chest compressions performed by female LUHS students during standard video self-instructional basic life support training.
4. To assess the effectiveness of the Andrew’s manoeuvre on the quality of chest compressions in the setting of the simulated Emergency Medical System dispatcher-assisted cardiopulmonary resuscitation in elderly lay-people population.
5. To evaluate the lay-people’ opinion about their ability to perform chest compressions during dispatcher-assisted cardiopulmonary resuscitation, the helpfulness of the dispatcher’s assistance over the telephone, and the Andrew’s manoeuvre.
1. REVIEW OF LITERATURE
1.1. Cardiac arrest
1.1.1. Definition and epidemiology
Cardiac arrest is the cessation of cardiac mechanical activity, confirmed by the absence of a detectable pulse, unresponsiveness, and apnea (or agonal, gasping, respirations) (44). Globally, the incidence OHCA ranges from 20 to 140 per 100 000 people, and survival ranges from 2% to 11% (45). Data from systematic overview of 67 studies and 178,440 OHCAs in a source population of over a 100 million people, have found that the global average incidence was 55 adult OHCAs of presumed cardiac cause per 100,000 person-years (45). Approximately 85% of cardiac arrests occur in the out-of hospital setting. Of all OHCAs, 27% had VF as the initial rhythm (45). Men have a threefold higher incidence of OHCA than women, especially in middle age (46).
Consensus Statement From the AHA declared about 200 000 adult IHCA and 6000 pediatric IHCA in the United States each year (47). Single-institution studies using Utstein criteria have reported large variations in hospital CA rates of adult (IHCA), ranging from 3.8 to 13.1 per 1000 admissions (47). Recent systematic review by Efendijev and al have shown that the incidence of intensive care unit CA varied from 5.6 to 78.1 CA per 1000 intensive care unit admissions (48).
The incidence of OHCA in Lithuania is uncertain. There is no national cardiac arrest registry, and cardiac arrest is not an accepted cause of death in the national death registry. Calculations indicate that the annual number of OHCA in Lithuania could be about 1650 people (45). Official statistics from Lithuanian Ministry of Health have shown that more than a half of all deaths (56.3%) were caused by diseases of the circulatory system in 2013. The largest part of deaths due to circulatory system diseases was caused by ischaemic heart disease (64.7%) and cerebrovascular diseases (25.2%). The majority of all deceased from diseases of the circulatory system (86.1%) were aged 65 years old and over (49).
1.1.2. Outcome
The overall survival of patients with OHCA was essentially unchanged for 30 years—from 1978 to 2008 at 7.6% (45). An indicator of an emergency medical system’s (EMS) effectiveness in treating patients with OHCA is to
focus on the subgroup that has a reasonable chance of survival; patients found to be in ventricular fibrillation/ventricular tachycardia (VF/VT). Five core elements have consistently been associated with survival to hospital discharge: witnessed arrest (by a bystander or EMS); bystander CPR; shorter EMS response interval; first shockable rhythm; and return of spontaneous circulation (ROSC) in the field (50). During the past decade, there has been increased recognition of the importance of additional factors associated with the likelihood of survival after OHCA, such as dispatcher-assisted CPR (51), the quality of CPR (52, 53), and others (50). Systematic overview conducted in 2010 by Berdowski and al have shown that in Asia, the percentage of VF and survival to discharge rates were lower (11% and 2%, respectively) than those in Europe (35% and 9%, respectively), North America (28% and 6%, respectively), or Australia (40% and 11%, respectively) (45). The variability of survival rates among different locations given the same rhythm and same setting suggests that resuscitation performance may be a contributing factor. Bystander CPR and defibrillation are two of only a few modifiable factors clearly associated with increased survival for OHCA (37, 54-57). Numerous investigations have shown that bystander CPR results in a doubling or tripling of survival from OHCA, yet bystander CPR rates across the world have remained unacceptably low at around 30% (58-61). Communities with high bystanders CPR rate (40-70%) have achieved up to 40-50% survival rate after witnessed VF OHCA. Recent large population-based cohort studies from USA (62, 63), Canada (64), Denmark (55) and The Netherlands (56) reported about an improved survival from OHCA during past decade. Large studies by Safdar (65) and Bray (66) and al analysed the sex-associated variation in survival to hospital discharge in OHCA patients as well as the relationship between age and sex for predicting survival. Women were less likely to be younger, have a witnessed arrest, receive bystander CPR, arrest in a public place, have an initial shockable rhythm or receive transport to 24-h cardiac interventional hospital (65, 66). Survival to hospital admission and ROSC did not differ between women and men in Safdar study. Women had a higher probability of survival until age 47 years, after which men maintained a higher probability of survival (65). Bray and al have found that women were more likely to survive to hospital arrival than men, but no gender differences were seen in survival to hospital discharge (65).
Overall, there is a 10-fold global variation in reported OHCA incidences and outcome. This may reflect differences in methodology, in EMS systems, in case definitions, as well as true differences in risk and
1.1.3. Chain of survival
Successful resuscitation following cardiac arrest requires an integrated set of coordinated actions represented by the links in the Chain of Survival (see Figure 1.2.3.1) (67). The ‘chain of survival’ concept was first introduced in 1991, and this chain remains a symbol of resuscitation services in many parts of the world (68).
Figure 1.1.3.1. Chain of Survival (The 2010 AHA Guidelines for CPR and ECC)
The links include the following:
Immediate recognition of cardiac arrest and activation of the emergency response system;
Early CPR with an emphasis on chest compressions; Rapid defibrillation;
Effective advanced life support; Integrated post– cardiac arrest care.
The individual links are interdependent, and the success of each link is dependent on the effectiveness of those that precede it (67). The early links, those involving bystanders (immediate emergency activation and early bystander CPR), are essential for the effectiveness of subsequent links (51). In the out-of-hospital setting CPR is often provided by laypersons who may be involved in a resuscitation attempt only once in their lives. Thus, efforts that can improve early recognition of OHCA and increase bystander CPR are likely to improve survival from OHCA. It is already has been shown that strengthening all the links in the chain of survival may lead to 50% survival from OHCA (36, 57, 63, 69).
1.2. Cardiopulmonary resuscitation (CPR)
Cardiopulmonary resuscitation (CPR) is a series of lifesaving actions that improve the chance of survival following cardiac arrest (59).
1.2.1. History of CPR
Cardiopulmonary resuscitation has been practiced in various forms since the beginning of recorded history (70, 71). Galen in 175 AD described the use of bellows to inflate the lungs of a dead animal (72). The Old Testament in the King James Bible, II Kings 4:34 described the resuscitation of a young boy by the prophet Elijah. In 1741, The Paris Academy of Sciences officially recommended mouth-to-mouth resuscitation for drowning victims (72). In 1775, standards were set for resuscitation by the Royal Humane Society, which stated that the most efficacious method was "to blow with force into the lung, by applying the mouth to that part of the patient, closing his nostrils with one hand, and gently expelling the air again by pressing the chest with the other (73)". Sternal compression was suggested in 1786 by Sherwin, a surgeon of Enfield: "The surgeon should go on inflating the lungs and alternately compressing the sternum (73)". Cardiac massage began in 1874, when Schiff performed the first open-chest cardiac massage in the dog (72). Boehm in 1878 administered closed-chest cardiac massage to cats by compressing the sides of the thoracic cage together (74). Koenig is credited as the father of external cardiac compression and reported in 1885 successful resuscitative efforts in man (70). Maass in 1891 performed the first equivocally documented chest compression in humans and in 1892 reported a modification of the Koenig technique (70).
In 1960, a group of resuscitation pioneers, Drs Peter Safar, James Jude, and William Bennett Kouwenhoven, combined mouth-to-mouth breathing with chest compressions to create Cardiopulmonary Resuscitation, the lifesaving action we now call “CPR” (75). Kouwenhoven and al demonstrated the equality and greater ease of closed chest cardiac massage than open-chest cardiac massage. At this point, modern CPR was born (70).
Electrical defibrillation may have begun in 1775, but was not proven successful in animals internally until 1899. The technique was applied to man internally in 1947 by Beck and externally in 1956 by Zoll and al (72). The major limitation of defibrillators until the 1960’s was their lack of portability. They needed alternate current from the mains and heavy transformers to step up the voltage to approximately 1.000 Volts that was necessary to defibrillate
switched from alternate to direct current in his defibrillators (76). First successful defibrillation using direct current in Lithuania was applied by Lukoseviciute in 1963. Direct current also made battery operation possible. In 1979, the first portable automatic external defibrillator (AED) was developed, with a pharyngeal electrode for sensing, shocking electrodes on the abdomen and tongue, and a simple algorithm to detect abnormal rhythms and automatically deliver rescue pacing or a defibrillation shock, as appropriate (77).
1.2.2. Elements of CPR 1.2.2.1. Chest compressions
Chest compressions (CC) are a paramount component of CPR. External chest compressions were first described in 1960 by Kouwenhoven and al (75), and the technique remains essentially the same today. “Anyone, anywhere,
can now initiate cardiac resuscitative procedures. All that is needed are two hands” was written by Kouwenhoven and remains a cornerstone of CPR in
2015. Unlike other medical interventions, CC can be initiated by any first aid provider without a physician’s order. All rescuers, including laypeople, regardless of training, should provide CC to all cardiac arrest victims (67). If a patient is found unresponsive without a definite pulse or normal breathing then the first responder should assume that this patient is in cardiac arrest, activate the emergency response system and immediately start chest compressions (9, 36). Due to the importance of starting CC early, pulse and breathing checks were de-emphasized in the most recent CPR guidelines (9, 36). Thus, only healthcare providers should check for a pulse, but no longer than 10 seconds.
Chest compressions generate a small but critical amount of blood flow to the heart and brain. The precise mechanism of blood flow during CC has been controversial since the 1960s (78). The two main hypotheses are the external cardiac massage model and the thoracic pump model. The external cardiac massage model suggests that CC directly compress the heart between the depressed sternum and the thoracic spine (75). This ejects blood into the systemic and pulmonary circulations while backward flow during decompression is limited by the cardiac valves. The external cardiac massage model is supported by radiographic evidence of direct compression of cardiac structures during CC (79). The thoracic pump model suggests that CC intermittently increase global intra-thoracic pressure, with equivalent pressures exerted on vena cava, the heart and the aorta (80, 81). Thus blood
is ejected retrograde from the intra-thoracic venous vasculature as well as antegrade from the intra-thoracic arterial vasculature and both arterial as well as venous pressures rise concomitantly. The thoracic pump model is supported by arterial and venous pressure tracings demonstrating simultaneous peaks in venous and arterial pressures during chest compressions (82). The newest systematic review by Georgiou and al concluded that the available evidence suggests that both cardiac massage and the thoracic pump contribute to blood flow during CC (83).
The ERC Guidelines 2010 for CPR recommend for rescuers to compress the sternum of an adult victim of cardiac arrest “at least 5 cm (but not more than 6 cm) at a rate of “at least 100/min (but not more than 120/min)” (9).
1.2.2.2. Ventilation
In order to improve the quality and frequency of CC, the role of oxygen delivery and carbon dioxide removal (i.e. ventilation) has been de-emphasized in 2010. Tissue oxygenation is obviously still important, but the blood possesses several minutes of oxygen reserve, and whatever subsequent delivery occurs should occur with minimal disruption to cardiac contraction. Accordingly, the Guidelines 2010 recommended a ventilation rate of less than 12 breaths per minute, and a ventilation volume that produces no more than visible chest rise (36). The lone rescuer who is trained and able should open the airway and give 2 rescue breaths after each cycle of 30 CC. Ventilations should be provided if the victim has a high likelihood of an asphyxial cause of the arrest (eg, infant, child, or drowning victim). However, the Guidelines 2010 recommended to provide Hands-Only CPR (compressions without ventilations) for the untrained rescuer (36, 67).
1.2.2.3. Defibrillation
With the development of small, portable, automated external defibrillators (AED’s) of relatively low cost and long battery life, defibrillation became available far outside the hospital environment and integrated in basic life support (BLS). Placement of AEDs in public places was recommended by AHA in early 1990s (84). Early defibrillation is critical to survival from sudden CA for several reasons: the most frequent initial rhythm in witnessed OHCA is ventricular fibrillation (VF), the treatment for VF is defibrillation, the probability of successful defibrillation diminishes
no CPR is provided (86). Thus, CPR maintains the heart in a state favourable for defibrillation. When bystander CPR is provided, the decrease in survival rates is more gradual and averages 3% to 4% per minute from collapse to defibrillation (86, 87). CPR can double (86) or triple (88) survival from witnessed sudden CA at most intervals to defibrillation (85). The effectiveness of CC is one of the determinants of successful defibrillation. Defibrillation outcome is improved if interruptions in CC are kept to a minimum (89, 90).
1.2.3. Regulation of CPR
The International Liaison Committee on Resuscitation (ILCOR) includes representatives from the American Heart Association (AHA), the European Resuscitation Council (ERC), and other national Councils from different continents. Its mission is to identify and review international science and knowledge relevant to CPR and emergency cardiovascular care (ECC) and to offer treatment recommendations in 5-yearly cycles (91). The most recent International Consensus Conference was held in Dallas in February 2010 and the published conclusions and recommendations from that process formed the basis of ERC and AHA (36) Guidelines 2010. In Lithuania, regulation of CPR is based on the order of the Ministry of Health, which was drafted under the 2010 ERC guidelines, and valid from 31st August 2011.
1.2.4. Bystander CPR
Bystanders and immediate on-scene response is a critical part of the ‘chain of survival’ approach to resuscitation in OHCA (92). Less than 1% of patients who are not resuscitated in the field will leave the hospital alive (93). For every 30 people who receive bystander CPR, 1 additional life is saved (59). Approximately 67% of CA victims are first witnessed by bystanders (22) and the target time interval for Emergency Medical Services arrival is 8 min (94). For every minute that CPR is delayed, the likelihood of survival would decrease approximately 10% (86). In settings with prolonged EMS response or travel times, the resuscitative efforts of bystanders may be even more important to OHCA survival (95). However, only about a third of OHCA victims receive bystander resuscitation prior to the arrival of emergency personnel (58-60).
According to surveillance data reported and on victims of OHCA who received CPR in the prehospital setting between 2005 and 2010, 37.6% of OHCA events were witnessed by bystanders, only 43.8% of them performed CPR and significantly increased survival rate to 11.2% compared with 7.0%
in victims who did not receive CPR prior to EMS arrival (96). In other words, the analysis showed bystander CPR to have a 37.5% relative risk reduction and a number needed to treat of 24. To put this effect into perspective, aspirin given to prevent major cardiovascular events has a number needed to treat of 253 in patients without clinical evidence of cardiovascular disease (97).
Reluctance to perform CPR between bystanders including concern for injuring the victim (98), stress or panic (20, 99), fear of performing CPR incorrectly (20, 100, 101), physical limitations (98, 102, 103), fear of liability (98), or fear of infection (100). Different approaches have been used to encourage and improve bystander CPR. Popular strategies adopted to promote bystander CPR rates usually involve: trying to teach CPR to as many people as possible in the community (104), targeting CPR training for those most at risk to encounter a CA victim (105), and promoting dispatch-assisted CPR instructions (25).
1.2.5. Hands-only CPR
Different approaches have been used to encourage and improve
bystander CPR. One such approach is for the lay rescuer to provide bystander
CPR that consists of continuous CC only in contrast to standard CPR (ST-CPR) that comprises CC interposed with rescue breathing. CC alone is easier and quicker to initiate and so might provide for earlier CPR (103) among a greater number of persons with OHCA (106). Most laypeople are unlikely to perform ST-CPR, especially on a stranger or trauma victim, but are more likely to perform hands-only CPR (100).
Over the course of the last decade, evidence from animal experiments (107, 108) and observational human studies (109-113) questioned the usefulness of rescue ventilation during adult CPR. These studies have found chest compression-only or HO-CPR either equivalent to standard CPR with rescue ventilation or suggested even a benefit (107, 114). In a realistic swine model of single-bystander out-of-hospital VF cardiac arrest in which defibrillation was first attempted at 12 minutes of the arrest, HO-CPR resulted in more 24-hour neurologically normal survivors than did the 2005 guideline– recommended 30:2 CPR (107). Uninterrupted CC produced higher integrated coronary perfusions pressures relative to the 30:2 CPR groups because of the required pauses in CC in the latter group to provide breaths. Furthermore, HO-CPR generated more consistent arterial systolic pressures, which provided cerebral perfusion and presumably contributed to the better neurologically normal survival in this group. The study by Ewy and al
first 12 minutes of VF even if initiation of bystander resuscitation is delayed for as long as 6 minutes after the onset of VF (107). Wang and al also have found that in the first 12 min of CPR, continuous CC could maintain relatively better coronary perfusion pressure, PaO2, and global ventilation/perfusion values than 30:2 CPR. Therefore, rescue ventilation during 12 min of simulated bystander CPR did not improve haemodynamics or outcomes compared with HO-CPR (115). The later his experimental study with animals have shown that both groups with or without rescue breathing had similar 24-hr survivals and cerebral performance categories (116).
Researchers have found that rescue breathing during CPR did not influence restoration of spontaneous circulation (ROSC), neurologic outcome, or haemodynamics after ROSC, but it did improve postarrest lung function and alleviated lung injury. Rottenberg argued that Wang and al achieved these results only because rescuers performed adequate-force/depth high-impulse HO-CPR (117). During high-impulse HO-CPR, substantial compression-induced ventilation that was apparently generated was enough to achieve similar ROSC and neurologic outcome as high-impulse S-CPR, but not enough to influence postarrest lung function. It seems that rescue breathing as a double-edged sword: it is harmful to haemodynamics during CPR but protects the lung after CPR (116).
By advocating HO-CPR for bystanders of patients with primary OHCA, survival of patients with primary cardiac arrest in Arizona increased over a 5-year period from 17.7% to 33.7% (118). In the recent large, follow-up investigation of 2 randomized trials comparing dispatcher CPR instruction, patients with cardiac arrest randomly assigned to CC alone instruction had better long-term survival than patients randomly assigned to CC plus rescue breathing instruction (27). A growing body of scientific evidence supports current resuscitation guidelines to recommend HO-CPR for untrained lay-rescuers and trained lay-rescuers who are not able to perform rescue breaths (36, 119). Professional rescuers should provide CC with ventilations for CA victims (91). For children who have OHCA mostly from non-cardiac causes, ST-CPR is superior (120).
1.2.6. Dispatcher-assisted CPR
Dispatcher-assisted cardiopulmonary resuscitation was first conceived in the early 1970s (121). Untrained callers could be instructed to perform CPR by trained dispatchers over the telephone, but more important that medical emergency dispatcher (MED) telephone instructions to callers increase bystander CPR rates (24-26) and survival (24, 25) after OHCA. Recent data
provide strong support for long-term mortality benefit of a dispatcher CPR instruction strategy consisting of chest CC alone rather than compression plus rescue breathing among adult patients with OHCA (27, 122, 123). The meta-analysis conducted in 2010 has shown that dispatcher-assisted bystander HO-CPR is associated with improved survival after OHCA in adults patients compared to ST-CPR. The pooled analyses from three published randomized clinical trials have shown that DA-CPR for adult OHCA was associated with a 22% improved chance of survival compared to standard CPR. The absolute increase in survival was 2.4%; the number needed to treat was 41 (114). The findings provided strong support for long-term mortality benefit of dispatcher CPR instruction strategy consisting of CC alone rather than CC plus rescue breathing among adult patients with cardiac arrest requiring dispatcher assistance (27).
The globally used medical priority dispatch system (MPDS V12.1 Priority Dispatch Inc., Salt Lake City, UT) is a standardized caller interrogation and emergency triage system combined with pre-arrival first aid and CPR instructions. Although, the MPDS is lacking prospective testing, more than 2800 emergency dispatch centers in 44 countries worldwide are currently using this protocol (124). Therefore, a more effective instruction would have a relevant and global impact on quality in telephone-assisted, lay rescuer CPR. In Lithuania, MPDS system was implemented and used in Kaunas region from 2011. Our Study III was the first study in Lithuania, there the effectiveness of the dispatcher-assisted pre-arrival first aid instructions to lay-people were evaluated.
1.3. Quality of CPR 1.3.1. Significance of CPR quality
It is clear that high-quality CPR is the primary component in influencing survival from cardiac arrest (3, 9, 36, 37). Without bystander CPR, cardiac arrest survival decreases 7%–10% for every minute of delay (86). There are 5 critical components of high-quality CPR: minimize interruptions in chest compressions, provide CC of adequate rate and depth, avoid leaning between compressions, and avoid excessive ventilation (3). CPR is inherently inefficient; it provides only 10% to 30% of normal blood flow to the heart and 30% to 40% of normal blood flow to the brain (125) even when delivered according to guidelines (3). This inefficiency highlights
However, even health care professionals performed CCs with shallower-than-recommended depths, as shown in previous clinical CPR studies in both in-hospital and out-of-hospital settings when the target depth was up to 50 mm (4, 5, 52). Wik and al (4) reported that during adult OHCA resuscitations, 33% of CC were too shallow and were being delivered only 48% of the time during the arrest. Similar deficiencies (23% of CC with incorrect rates; 36% of CC too shallow) were also seen during adult IHCA (5).
1.3.2. Main CPR quality determinants 1.3.2.1. Chest compression depth
ERC Guidelines 2010 for CPR recommend for all rescuers to compress the sternum of an adult victim of cardiac arrest “at least 5 cm (but not more than 6 cm)” (9). AHA recommends to compress the chest at least 5 cm without the recommendation for upper limit because no upper limit for CC depth has been established in human studies (36). The recommendation not to exceed 6 cm is supported by experts opinion (42). The previous Guidelines 2005 recommended to compress the sternum “4 to 5 cm” (10). The main reason for this change in guidelines are data from human observational studies which have shown that deeper compression depth is associated with higher success of defibrillation, a higher chance of admission to hospital and better survival (52, 53, 126-129). Increasing CC depth results in favorable hemodynamic changes, such as an increased arterial blood pressure, in adult humans (6) and an increase in coronary blood flow in mature pigs (7). Chest compression depth is linearly related to cardiac output, which is also linked to the likelihood of achieving a ROSC after defibrillation (126, 130). Meta-analysis published in 2013 have shown that cardiac arrest survivors were significantly more likely to have received deeper chest compressions than nonsurvivors (53).
1.3.2.2. Chest compression rate
ERC Guidelines 2010 recommend for all rescuers to compress the chest at a rate of “at least 100/min (but not more than 120/min)” (9). AHA recommends for lay rescuers and healthcare providers to perform chest compressions for adults at a rate of at least 100 compressions per minute without upper limit (36). The CC rate refers to the speed of compressions, not the actual number of compressions delivered per minute. One study of IHCA patients showed that delivery of 80 compressions/min was associated with
ROSC (131). Extrapolation of data from an OHCA observational study showed improved survival to hospital discharge when at least 68 to 89 chest compressions per minute were delivered; the study also demonstrated that improved survival occurred with CC rates as high as 120/min (89).
1.3.2.3. Duty cycle
Duty cycle represents a fraction of the time spent compressing the chest (compression phase) in the time between the start of one cycle of compression and the start of the next. A duty cycle of 50% is recommended in the current guidelines because it is easy to achieve with practice (36). Thus the duration of the compression phase should be equivalent to the duration of the decompression phase. However, Chung and al have shown that there is an interaction between the CC duty cycle and the depth. Induction of a shorter compression phase was correlated with a deeper chest compression during metronome-guided CPR in their recent study (132). Recent data from retrospective observational OHCA study conducted by Johnson and al (133) supported the experimental findings from Chung. Duty cycle comprised only about a third of the compression–decompression cycle, and was well below the recommended guideline. A relatively shorter compression phase (lower duty cycle) was associated with greater compression depth and slower compression rate (133).
1.3.2.4. Chest compression fraction and Hands-off time
The proportion of time in which chest compressions are performed in each minute of CPR is defined a chest compression fraction (CCF). CCF is an important modifiable aspect of CPR quality. Fewer interruptions are associated with increased ROSC, and increased likelihood of survival to hospital discharge (131, 134). AHA expert consensus is that a CCF of 80% is achievable in a variety of settings (3). Christenson and al have found that an increased CCF is independently predictive of better survival in patients who experience a prehospital VF/VT cardiac arrest (89). The highest survival (29%) was observed in the group of patients where 61–80% of CPR time was spent doing CC. The large multi-center prospective cohort study by Vaillancourt and al also suggested that increased CCF resulted in a higher likelihood of ROSC in a population of OHCA patients presenting with initial rhythms other than VF/VT - representing the majority of CA in this setting (134). EMS providers typically perform CC only 50% of the time during their
Pauses or hands-off time in CC delivery were defined as periods of interruption >1.5 s (CC rate <40 CC/min) (5). Sutton and al quantitatively described pauses in CC delivery during resuscitation from paediatric and adolescent IHCA. Etiologies were: 57.1% for provider switch; 23.9% for pulse/rhythm analysis; 4.4% for defibrillation; and 14.6% “other”. Provider switch accounted for 41.2% of no-flow duration. Compared to other causes, CPR epochs following pauses due to provider switch were more likely to have measurable residual leaning and were shallower. Individuals performing continuous CPR≥120 s as compared to those switching earlier performed deeper CC and were more compliant with guideline depth recommendations (135). Some out-of-hospital strategies that include continuous compressions without pauses for ventilations have been associated with improved outcomes (90). Interruptions for even a few seconds can decrease coronary blood flow (136), and are associated with worsened neurological outcome in animal models (107), and may decrease survival to discharge in OHCA (112). According to the Guidelines recommendations, pauses should be no longer than 10 s (36, 42). Such a statement is supported by recent study from Cheskes and al (137). Researchers have found that the odds of survival to hospital discharge were significantly higher for patients with pre-shock pause <10 s and peri-shock pause <20 s when compared to patients with pre-shock pause >/= 20 s and peri-shock pause >/= 40 s (137). Edelson and al have found that pauses in CC of ≥10 seconds’ duration have been associated with decreased success of defibrillation (126).
1.3.2.5. Recoil
CPR guidelines recommend to allow the chest to recoil completely (9, 36). Complete recoil is achieved by releasing all pressure from the chest and not leaning on the chest during the relaxation phase of the chest compressions (9). Although data are sparse regarding outcomes related to leaning, animal studies have shown that leaning increases right atrial pressure and decreases cerebral and coronary perfusion pressure, cardiac index, and left ventricular myocardial flow (138-140). Zuercher and al also have found that leaning of 10% to 20% (i.e., 1.8-3.6 kg) during CPR substantially decreased coronary perfusion pressure, cardiac index, and myocardial blood flow (138). Human studies showed that a majority of rescuers often lean during CPR and do not allow the chest to recoil fully (141, 142). Edelson and al have found that leaning is a bigger concern for taller rescuers and those using a step stool (143).
1.3.2.6. Total chest compression number
The number of chest compressions delivered per minute is an important determinant of return of spontaneous circulation (ROSC) and neurologically intact survival (89, 131). The actual number of chest compressions delivered per minute is determined by the CC rate and the number and duration of interruptions to open the airway, deliver rescue breaths, and allow AED analysis (36).
1.3.3. Factors related to CPR quality 1.3.3.1. Constant factors
1.3.3.1.1. Gender
Peberdy (13), Ashton (12), Riegel (144), Verplancke (145) and al have found that female participants performed CC of lower depth compared to male participants. All of them concluded that the gender effect might be explained by physical characteristics such as body weight or muscle strength, however, only Ashton reported anthropometric data of their study participants. Peberdy and al reported that gender (r=0.13, p = 0.001) was a significant predictor of CC depth (13). On contrary, Ochoa and al. (14) reported that an observed decrease in compression quality did not depend on gender, age, height, weight or the rescuer’s profession. All the studies were conducted according to Guidelines 2005 or earlier. There is no published data about relationship between gender and CC quality data in accordance with the Guidelines 2010.
1.3.3.1.2. Weight, height and BMI
Several studies had previously evaluated the effects of the rescuers’ physical characteristics on CPR performance. Before 2012, most of the data about relationship between rescuer’s anthropometric data (weight, height and BMI) and CC quality data came from the CPR studies with schoolchildren (15, 16, 146). Plant and Taylor summarized that CC depth of schoolchildren correlates with their physical factors such as increasing weight, BMI and height (147). However, only few data are available on relationship between CC quality and anthropometric data in adults and the outcomes are inconsistent. Ashton and al. have found that females achieved significantly fewer adequate compressions over a three minute period of CPR, and that this
studies was related to anthropometric and muscle strength differences between genders (13, 145), but both of the authors did not report weight, height, and BMI of their participants. On contrary, Ochoa and al did not found any relationship between CC quality data and rescuer’s weight, height, age and gender, but their sample size might be too small to detect such a difference (N=38) (14).
Although it has been demonstrated that the quality of CPR provided by female rescuers is worse comparing to male rescuers, the question has not been examined on a larger scale. There is still unknown what weight or BMI is related to the insufficient CC performance. Our data from the Study I and II filled that knowledge gap (39, 40).
1.3.3.1.3. Age
Only few studies examined the relationship between rescuer age and CC performance in adults. Peberdy and al have found that age (rpart =−0.09,
p = 0.02) was significant predictor of CC depth (13). Older individuals (51–
60 yr) performed CC of lower mean depth and performed a greater percentage of CC below AHA guidelines 2005 for depth compared to that performed by younger individuals (21–30 yr, 31–40 yr). Rate of CC did not differ by subject age. The authors explained that the age-related decline in CC performance could be due to a loss of muscle mass and strength with aging (13). Riegel and al also have found that rescuer’s age was associated with adequate CPR performance (OR 0.78 per 10-year increment) in large sample of laypersons (N=7261) (144).
1.3.3.2. Variable factors 1.3.3.2.1. Body position
The patient in cardiac arrest should be placed in supine position with the rescuer standing beside the patient’s bed or kneeling beside the patient’s chest (9). Compression mechanics are affected by rescuer positioning, but there is no consensus on the optimal rescuer position for chest compressions (149).
Researchers compared rescuer fatigue by doing CPR in different positions (150-153). Although there were no degradation in compression quality over a short duration (150, 152, 153), rescuer work appeared to increase in the standing position compared with use of a step stool or when kneeling (151, 154). In addition, step stools have been shown to increase CC depth, especially for rescuers of short stature (143). The AHA expert panel
recommended adjustable-height surface (such as a hospital bed), that the height of the surface be lowered, or that a step stool be used to enable rescuers to achieve optimal depth during CPR (3). Adjustment of the bed height or standing on a stool allows leveraging the body weight above the waist for mechanical advantage.
Jones and al evaluated whether energy consumption during CPR is higher with the rescuer standing than with the rescuer kneeling or in the bed-mount position, and whether CPR delivered with the rescuer standing induces an unfavourable mechanical loading in the rescuer’s lower back (154). Their results suggested that delivery of CC while standing produced greater spinal compression and mechanical energy flow than did delivery while kneeling. Thus, CC delivered while standing might be associated with increased loading of the spine. Jones and al have found that effectiveness of CC decreased when they were delivered while rescuers were standing rather than while kneeling (154).
Perkins and al. found that kneeling on the bed adjacent to the patient or lowering the bed did not affect the quality of chest CC in the first 3 min of continuous CPR. Sub-optimal CC were performed on all surfaces and participants failed to recognise their poor quality CPR (152). Chi and al. reported that rescuer position did not affect the compression force, depth, and frequency as performed by experienced providers for 5 min (153). However, the durations of CPR in these two studies were short, possibly affecting the outcome of rescuer fatigue.
In a study by Jantti and al Intensive Care Unit (ICU) nurses performed 10 minutes CPR, rotating every 2 minutes. The 44% of CC on the floor and 58% of CC on the bed were within correct depth, however, the mean CC depth decreased over time on both surfaces indicating rescuer fatigue (150).
Foo and al have found that experienced health-care providers were able to maintain effective compressions for 2 min while kneeling and standing on a taboret, but only for 1 min while standing on the floor. Moreover, the total pain 24h after CPR were significantly lower for the kneeling position (151). Later RCT by Hong supported data by Foo. Hong and al also have found that the number of adequate CC (depth > 50 mm) and the mean CC depth were significantly greater in the kneeling and footstool positions than in the standing position (155).
All of the participants in the Studies I-III were kneeling beside the manikin lying on the floor because kneeling position is most common during OHCA. According to the MPDS CPR protocol, the dispatcher prompts
1.3.3.2.2. Role of the surface
The Guidelines 2010 recommended to perform CPR on a firm, hard surface (9, 36). Backboards are commonly used during IHCA to achieve target depths (156) and reduce rescuer exertion (157), but their placement interrupts CPR (152). Noordergraaf and al have shown that hand movement is significantly larger (up to 110% at 50 mm target sternum-to-spine compression depth) when CPR is performed on a compliant mattress (157). The amount of extra movement is directly related to the type of mattress and may be confusing during both compression and relaxation phases. The extraneous movement can be reduced by at least 50%, but not eliminated, when a backboard is applied. The increased travel of the caregiver’s hands and proportionally increased workload are significant risks for unnoticed inappropriately shallow compressions during in-hospital CPR (157). For this reason, the AHA expert panel recommended placement of a backboard or firm, hard surface as soon as possible in coordination with other mandatory pauses in CCs to minimize interruption time (3). In out of the hospital setting CPR mostly is performed on the floor.
In the Studies I-III participants performed CPR on the floor in order to eliminate the effect of the surface to CC depth.
1.3.3.2.3. Role of the feedback
Recent systematic review of literature have found that use of audiovisual feedback devices during CPR can result in rescuers providing CC parameters closer to recommendations but there is no evidence that this translates into improved patient outcomes (158). Real-time CPR feedback devices, as well as low-cost solutions such as metronomes and music, are known to decrease variability and result in compression rates closer to the target rate of 100 to 120/min (132, 159, 160). Cason and al examined the effects of feedback (none, auditory only and visual only) on the quality of 10-min CPR and rescuer fatigue. Their data have shown that feedback mitigated the negative effects of fatigue on CPR performance and visual feedback yielded better CPR performance than did no feedback or auditory feedback (161). However, in most of the OHCA cases a first bystander does not have any type of feedback except EMS dispatcher or AED prompts, if available.
1.3.3.2.4. Role of the training and occupation
Very few studies have reported the effect of training on survival from cardiac arrest. In 1 study performed at a 550-bed tertiary care center, the
survival rate of patients initially resuscitated by a nurse trained in advanced cardiac life support (ACLS) was almost 4 times higher (37.5% vs 10.3%) than when resuscitation was initiated by a nurse without ACLS training (162). Sodhi and al also reported a significantly higher survival to hospital discharge in the post-BLS/ACLS training period than in the pre-BLS/ACLS training period (69.1% vs 23.1%) (163), however, their study had some methodological concerns (47).
Peberdy and al have found no difference in mean CC depth and rate between ACLS, BLS and CPR certified participants. Surprisingly, non-healthcare professionals provide CC of greater mean depth compared with nurses, but their rate was lower comparing with healthcare professionals (13). Swor and al determined factors associated with CPR provision by CPR-trained bystanders and factors associated with CPR performance by trained bystanders (20). Important overall predictors of CPR performance were the following: witnessed arrest (OR = 2.3; 95% CI = 1.4 to 3.8); bystander was CPR trained (OR = 6.6; 95% CI = 3.5 to 12.5); bystander had more than a high-school education (OR = 2.0; 95% CI = 1.2 to 3.1), or arrest occurred in a public location (OR = 3.1; 95% CI = 1.7 to 5.8). CPR training within five years (OR = 4.5; 95% CI = 2.8 to 7.3) was significant predictors of CPR performance among CPR-trained bystanders.
In order to eliminate the effects of the previous training to the outcomes, we excluded all BLS-certified students from the Study I and II. Most of the participants in the Study III were without prior CPR training, all of them were not certified in BLS.
1.3.3.2.5. Interaction between multiple rescues
Several ways have been suggested to improve quality of CPR, such as the use of some form of real-time feedback, HO-CPR, or CC performance by a mechanical device. However, in most situations the most practical way of improving the continued quality of CC is to change the rescuer performing them (164). Current CPR guidelines recommended provider switches approximately every 2 min (9) to limit the decrement in CPR quality over time that is observed with rescuer fatigue (150, 165, 166). Ashton (12) demonstrated that the quality of CC decreases within the first minute, and therefore suggest rotating every minute. However, Sutton and al have found that a significant portion of providers were able to continue high quality CPR for longer than 2 min when CPR quality feedback systems are used (135). They suggested that with CPR quality feedback systems deployed, an
recommended switch time of 2 min may be beneficial to improve CPR quality by minimizing switches, no-flow time, and risk for CPR error (135).
1.3.3.2.6. Rescue fatigue
It has been demonstrated that rescuer fatigue is a serious problem affecting the quality of CC (12, 14, 167). CCs are physically demanding and it has been generally assumed that rescuer fatigue can lead to degradation in compression quality (168, 169). Given the recent changes to CPR rates and a greater emphasis on pushing faster and deeper, has raised questions surrounding rescuer fatigue and efficacy of CC (170). Different studies have shown that physical fatigue in the rescuer occurs as soon as one minute after starting compressions on mannequins (12, 14, 32, 165, 171). Data from actual IHCA CPR study demonstrated statistically significant decay in CC depth, starting after 90 sec (148). Furthermore, it was also reported that the rescuer is unaware that fatigue has reduced their performance of compression effectiveness (12, 14, 152, 165). In contrast, data by Riera and al have shown that medical professionals were able to physically tolerate 2 minutes of CC without fatigue (172). However, the evaluation on the quality of chest compressions was not fully objective and quantitative in that study.
Systematic review conducted in 2009 by Williams and al have shown that there is low level evidence determining the most appropriate length of time in providing quality CC before rescuer fatigue occurs. Overall CC were shallower at least half of the time due to fatigue, and the mean compression rate was found to be higher than recommended (170).
All those studies were performed with medical students or medical professionals. Less is known about lay rescuers’ ability to perform HO-CPR and the fatigue. Delivery of nonstop compressions without fatiguing is quite difficult and could limit the effectiveness of HO-CPR strategy.
We evaluated the quality of HO-CPR performed by the elderly lay rescuers in the Study III, including the fatigue.
1.3.3.2.7. Fitness and muscle strength in CPR performance
Physical activity obviously also plays a role in assisting the rescuer to perform adequate CC over time during CPR. The workload at which physical fatigue occurs is, at least in part, determined by the physical fitness. Previous research suggested that CPR is physiologically demanding on rescuers, including well-trained professionals (167). The physical fitness is composed of two main features: cardiopulmonary (or physical) exercise capacity and muscle strength (171). Hansen and al have found that after 5 min quality of
CPR was related to maximal muscle strength (171). Ock and al reported that CPR represented a modest workload, on average requiring 65% of the predicted maximum achievable workload (38). Baubin and al have reported about raised blood lactate concentrations of approximately 3.0 mmol/L and heart rates (HRs) of approximately 130 beats/min in experienced professional CPR rescuers after a 30-min session of ST-CPR (173).
The study by Lucia and al (167) evaluated the influence of physical fitness in the performance of CPR providers as well as their physiologic response in performing 18 min CPR. All nonexpierenced in CPR, but physically fit healthcare providers were able to complete a 18 min HO-CPR trial, whereas 4 of 14 experienced CPR rescuers showed signs of physical fatigue that forced them to stop CCs before 18 min (167). Heart rate and oxygen uptake remained significantly lower in physically active but not experienced in CPR healthcare professionals during sustained CCR, when compared with sedentary CPR professionals. However, a different CCR quality was not demonstrated between the two groups (167). Their results indicated that a good physical fitness lowered the cardiopulmonary response to CCR, but it does not seem to affect CCR quality (171).
Russo and al also have found that rescuers with a better physical fitness and higher BMI performed better and showed less fatigue during 9 min CPR session (174). They found a significant correlation between BMI, workload required to reach a heart rate of 170 (PWC170), heart rate at 75 watts (HR75) and mean CC depth for compression-ventilation ratio of 30:2, indicating that participants with a higher BMI, a higher PWC170 and a lower heart rate at 75 watts performed deeper CC (174).
Ock and al evaluated the influence of physical fitness of CPR provider on the quality of CC, and the physiological changes during continuous CC for 5 min (38). They observed good correlations between the numbers of correct CCs with muscle strength at each minute except the first minute. In multiple regression analyses, the researchers have found that only muscle strength affected the quality of correct CC (38).
It seems that undertaking a light to moderate aerobic exercise program can have a positive impact on reducing rescuer fatigue whether experienced in CPR or no (167). We used body fat percentage as the measure of fitness level in the Study I, as it is the only body measurement that directly calculates an individual's body composition without regard to height or weight.
1.4. CPR training
Optimal training is important for achieving the necessary skills to save cardiac arrest patients. Training should be tailored to the needs of different types of learners and learning styles to ensure acquisition and retention of resuscitation knowledge and skills (175). CPR skills and their application depend on the rescuer’s training, experience, and confidence. According to the AHA Guidelines 2010, all rescuers, regardless of training, should provide chest compressions to all cardiac arrest victims (Figure 1.5.1). Because of their importance, CC should be the initial CPR action for all victims regardless of age. Rescuers who are able should add ventilations to CC. Highly trained rescuers working together should coordinate their care and perform CC as well as ventilations in a team-based approach (67).
Figure 1.5.1. Building Blocks of CPR (The 2010 AHA Guidelines for CPR and ECC)
Intuitively, the higher the number of persons trained in CPR skills in a given community, the more frequently it is performed (176). A relationship between CPR training and an increase in resuscitation attempts by bystanders has been reported by different studies (55, 57, 177, 178). For example, in Los Angeles, where the relative percentage of citizens trained in CPR is estimated to be relatively low, only a small percentage of bystanders performed CPR and just 1.4% of OHCA victims survived (179). However, 10-fold
improvements in survival rates (>15%) have been reported in Seattle, where the frequency of bystander-performed CPR is one of the highest (>50%) in the USA (176, 180).
Resuscitation manikins have been an essential element of CPR training for half a century. Meta-analysis of 114 studies indicated that simulation-based resuscitation training was highly effective when compared with no-intervention (181).
There are different ways to transfer CPR skills to the population. Traditional, instructor-led training courses remain the most frequently used method for basic life support and AED training. Self-instruction programmes (e.g., video, DVD, computer driven) with minimal or no instructor coaching are progressively used as alternatives to instructor-led courses for laypeople and healthcare providers. Large-scale dissemination of CPR training can be achieved through video self-instruction (VSI) (104, 177). Studies have demonstrated that lay rescuer CPR skills can be acquired and retained at least as well through interactive computer- and video-based synchronous practice instruction when compared with instructor-led courses (182-185). Short video instruction combined with synchronous hands-on practice was recommended as effective alternative to instructor-led basic life support courses by AHA in 2010 (Class I, LOE A) (149).
In an attempt to address the barriers to learning CPR, the AHA has produced the CPR Anytime kit, featuring a 22-minute instruction video to be watched at the viewer’s convenience. Lynch and al (182) demonstrated that the 22-minute video self-instruction program was as effective in training subjects as a 4-hour course. VSI course resulted in better overall CPR performance compared to the standard AHA Heartsaver® course (182). The study by Roppolo and al has shown that CPR performance following 30-min training was either equivalent or superior to the multi-hour
Heartsaver-Automated External Defibrillator training in all measurements, both
immediately and 6 months after training (184). Einspruch and al also demonstrated that CPR skill performance for self-trained and traditionally trained groups declined during the 2-month interval at similar rates (183).
In Lithuania, we delivered instructor-led BLS courses from AHA and ERC for more than a decade. Supported by the AHA recommendation about the efficiency of the VSI course, we decided to employ the 22 min. video-based lecture titled AHA Family and Friends, CPR Anytime in to teach practical CPR skills in the Study I and II.
2. METHODS
2.1. Study design and population
We evaluated the CC quality in three studies. The Study I and Study II were non-randomised cohort trials conducted in the Department of Disaster Medicine of the LUHS in students. The study III was a randomized control trial conducted in the Department of Disaster Medicine of the LUHS in elderly bystanders. The flow chart of the dissertation’s studies is presented in Figure 2.1.1.
The LUHS Bioethics Centre approved the study (Protocol No. BC-MF-188/2011), and all participants provided written informed consent.
Figure 2.1.1. Flow chart of the dissertation’s studies
2.1.1. The quality of the chest compressions in LUHS students (Study I)
The participants included in the Study I were sixth-year medical and fourth-year pharmacy students who underwent basic life support (BLS) training according to the LUHS curriculum between January and March 2011. We excluded students who had already received practical training in BLS,
