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Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min
Resuscitation 55 (2002) 151 /155 www.elsevier.com/locate/resuscitation
Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min A. Ashton a, A. McCluskey a,*, C.L. Gwinnutt b, A.M. Keenan a a
Department of Anaesthesia, Stepping Hill Hospital, Stockport SK2 7JE, UK Salford Royal Hospital NHS Trust, Hope Hospital, Salford M6 8HD, UK
b
Received 17 January 2002; received in revised form 8 May 2002; accepted 16 May 2002
Abstract Guidelines for the performance of cardiopulmonary resuscitation (CPR) have been revised recently and now advocate that chest compressions are performed without interruption for 3 min in patients during asystole and pulseless electrical activity. The aim of the present study was to determine if rescuer fatigue occurs during 3 min of chest compressions and if so, the effects on the rate and quality of compressions. Forty subjects competent in basic life support (BLS) were studied. They performed continuous chest compressions on a Laerdal SkillmeterTM Resusci-Anne† manikin for two consecutive periods of 3 min separated by 30 s. The total number of compressions attempted was well maintained at approximately 100 min 1 throughout the period of study. However, the number of satisfactory chest compressions performed decreased progressively during resuscitation (P B/0.001) as follows: first min, 82 min 1; second, 68 min 1; third, 52 min 1; fourth, 70 min 1; fifth, 44 min 1; sixth, 27 min 1. We observed significant correlations between the number of satisfactory compressions performed and both height and weight of the rescuer. Female subjects achieved significantly fewer satisfactory compressions compared with males (P /0.03). Seven subjects (five female, two male) were unable to complete the second 3-min period because of exhaustion. We conclude that rescuer fatigue adversely affects the quality of chest compressions when performed without interruption over a 3-min period and that this effect may be greater in females due to their smaller stature. Consideration should be given to rotating the rescuer performing chest compressions after 1 min intervals. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Advanced life support (ALS); Cardiopulmonary resuscitation (CPR); Chest compression; Manikin; Rescuer fatigue
Resumo As recomendac¸o˜es para a reanimac¸a˜o foram recentemente revistas e recomendam agora que as compresso˜es tora´cicas sejam, nos doentes com assistolia e actividade ele´ctrica sem pulso, feitas durante treˆs minutos sem interrupc¸a˜o. Este estudo teve como objectivo verificar se ha´ fadiga do reanimador durante treˆs minutos de compresso˜es tora´cicas e em caso afirmativo se isso influencia a frequeˆncia e qualidade dessas compresso˜es. O estudo foi feito com quarenta indivı´duos treinados em Suporte Ba´sico de Vida (SBV). Fizeram compresso˜es tora´cicas contı´nuas em manequim Laerdale SkillmeterTM e Resusci Anne† em dois perı´odos consecutivos de 3min espac¸ados por um perı´odo de 30s. O nu´mero de compresso˜es, durante o perı´odo do estudo, foi bem mantido a um ritmo de cerca de 100 min 1. Contudo, o nu´mero de compresso˜es satisfato´rias foi diminuindo ao longo da reanimac¸a˜o (P B/0.001) da seguinte forma: primeiro minuto 82 min 1, segundo 68 min 1, terceiro 52 min 1, quarto 70 min 1, quinto 44 min 1, e sexto 27 min 1. Verificou-se haver uma boa correlac¸a˜o entre o nu´mero de compresso˜es eficazes e o peso e altura do reanimador. As mulheres fizeram significativamente menos compresso˜es eficazes do que os homens (P /0.03) . Sete dos reanimadores (cinco mulheres e dois homens) foram incapazes de completar o segundo perı´odo de treˆs minutos de compresso˜es tora´cicas por exausta˜o. Concluı´mos que o cansac¸o dos reanimadores afecta negativamente a qualidade das compresso˜es tora´cicas, quando efectuada sem interrupc¸a˜o
* Corresponding author. Tel.: /44-161-419-5869; fax: /44-161-419-5045 E-mail address: [email protected] (A. McCluskey). 0300-9572/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 0 - 9 5 7 2 ( 0 2 ) 0 0 1 6 8 - 5
152
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
durante treˆs minutos e que este efeito pode ser maior nas mulheres por causa da sua menor estatura. Justifica-se considerar a hipo´tese de rodar os reanimadores ao fim de um minuto de compresso˜es tora´cicas. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Palavras chave: Suporte Avanc¸ado de Vida (SAV); Reanimac¸a˜o cardio-pulmonar; Compresso˜es tora´cicas; Fadiga do reanimador
Resumen Las guı´as para la realizacio´n de reanimacio´n cardiopulmonar (RCP) han sido revisadas recientemente y ahora sostienen que las compresiones sean realizadas sin interrupcio´n por tres minutos en pacientes en asistolı´a y actividad ele´ctrica sin pulso. El objetivo de este estudio fue determinar si ocurre fatiga del reanimador durante tres minutos de compresiones tora´cicas, y si es ası´, los efectos sobre la frecuencia y profundidad de las compresiones. Se estudiaron cuarenta sujetos competentes en soporte vital ba´sico (BLS). Realizaron compresiones tora´cicas continuas en un maniquı´ Laerdal SkillmeterTM Resusci-Anne† por dos perı´odos consecutivos de 3 minutos, separados por 30 segundos. El nu´mero total de compresiones intentadas fue bien mantenido por aproximadamente 100 min 1 a lo largo de todo el perı´odo de estudio. Sin embargo, el numero de compresiones tora´cicas satisfactorias realizadas disminuyo´ progresivamente durante la resucitacio´n (P B/0.001) de la siguiente manera: primer minuto 82 min 1; segundo, 68 min 1; tercero, 52 min 1; cuarto, 70 min 1; quinto, 44 min 1; sexto, 27 min 1. Encontramos correlaciones significativas entre el numero de compresiones tora´cicas satisfactorias realizadas y tanto la estatura como el peso del reanimador. Reanimadoras femeninas alcanzaron significativamente menos compresiones satisfactorias comparadas con los reanimadores varones (P /0.03). Siete sujetos (cinco mujeres, dos varones) fueron incapaces de completar el segundo perı´odo de tres minutos por estar exhaustos. Concluimos que la fatiga del reanimador afecta adversamente la calidad de las compresiones tora´cicas cuando son realizadas sin interrupcio´n durante perı´odos de tres minutos y que este efecto puede ser mayor en mujeres debido a su menor estatura. Debe darse consideracio´n a la rotacio´n de los reanimadores que realizan las compresiones tora´cicas despue´s de intervalos de un minuto. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Palabras clave: Soporte vital avanzado (SVA); Reanimacio´n cardiopulmonar (RCP); Compresiones tora´cicas; Maniquı´; Fatiga del reanimador
1. Introduction
2. Materials and methods
Chest compression has been one of the principal elements of circulatory support during cardiopulmonary resuscitation (CPR) for more than 40 years [1]. The guidelines for performance of CPR during cardiac arrest have been revised recently [2,3] and reflect a stronger evidence base [4]. Once the airway has been secured with a cuffed tracheal tube, chest compressions now continue uninterrupted at a rate of 100 min 1. Thus, when following the asystole/pulseless electrical activity limb of the universal resuscitation algorithm, chest compressions must be performed continuously for 3 min. This reflects the observation that uninterrupted chest compressions may improve coronary perfusion [5]. Anecdotally we have noticed that some rescuers find it difficult to maintain their performance over this relatively prolonged period because of fatigue, leading on occasions to an ‘unofficial’ handover to another rescuer before the end of the 3 min cycle. It has been suggested previously that rescuer fatigue may become apparent after only a min of chest compressions [6,7]. Furthermore, fatigue and the resulting decrease in performance may not be recognised by the rescuer [7]. The aims of the present study were to evaluate the effect of rescuer fatigue on the rate and quality of chest compressions when following the new resuscitation guidelines and the influence of rescuer gender, weight and height on performance.
Forty subjects (20 male, 20 female) competent in basic life support (BLS) were recruited from doctors and nurses working in the Intensive Care Unit, Emergency Department, Emergency Admissions Unit and Operating Room Recovery Area of a large district general hospital in the UK. A Laerdal SkillmeterTM ResusciAnne† manikin located on the floor was adopted as our experimental model as it is used within the hospital for CPR training. The integral Skillmeter records both the total number of compressions attempted and the number of these considered satisfactory. For the purposes of the study a satisfactory compression was defined as one with a depth of 4 /5 cm. Subjects were immediately directed to rectify incorrect hand placement if necessary. After a preliminary period of familiarisation and practice during which time the subjects were permitted to view the display of the Skillmeter in order to perfect their performance, they performed 3 min of continuous chest compressions on the manikin aiming for a rate of 100 min 1. After a 30 s interval representing a maximal period during which the pulse, ECG electrodes, ECG lead and gain settings would be checked during an actual cardiac arrest, a further 3 min of chest compressions were performed as before. For each subject the following demographic parameters were recorded: rescuer gender, age, weight, height, profession (doctor or nurse) and whether or
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
not the subject was a certified advanced life support (ALS) provider. Data from a preliminary pilot study of the first ten subjects with a mean (S.D.) decline in performance of 25 (43) satisfactory compressions min 1 between the first and third min of resuscitation were used to determine that a sample size of 38 subjects was required to detect a decline in performance of 20 satisfactory compressions min 1 with 80% power. Statistical analyses were performed using SPSS version 7. Continuous normative data were analysed using Student’s unpaired t -test. Change in performance over time of chest compressions within subjects was analysed using Friedman’s non-parametric repeated measures analysis of variance (ANOVA) with Dunn’s multiple comparisons correction used as appropriate. Between group comparisons were made using the Mann /Whitney U -test. A value of P B/0.05 was considered significant.
153
Fig. 1. Effect of rescuer fatigue on performance of chest compressions. Data are median (interquartile range). *P B/0.05; **P B/0.01; ***P B/ 0.001 for the difference from first minute of respective period of chest compressions.
3. Results Forty subjects (20 males and 20 females) took part in the study. Twenty-three were nurses (17 females, six males) and 17 were doctors (three females, 14 males). Male subjects were significantly heavier (mean 78.2 (S.D. 10.4) vs. 66.1 (12.8) kg, P /0.0024) and taller (177.5 (5.7) vs. 161.9 (6.7) cm, P B/0.0001) than their female counterparts. The number of compressions attempted was well maintained at approximately 100 min 1 (Table 1). Male and female subjects did not differ in the rate of compressions attempted. However, the number of satisfactory chest compressions performed by the entire study group decreased during both 3-min periods of simulated resuscitation (P B/0.0001) (Fig. 1). Performance recovered transiently during the fourth minute (P B/0.05), following the 30 s interval separating the two
Fig. 2. Comparison of rescuer fatigue between male and female subjects during each 3-min period of chest compressions. Data are median (interquartile range). *P /0.03.
periods. Significantly fewer satisfactory compressions were performed during the second 3-min period compared with the first (P /0.02). Female subjects achieved significantly fewer satisfactory compressions during the
Table 1 Rate of attempted chest compressions and rate satisfactory (min 1) during simulated CPR Minute
1 2 3 4 5 6 1st 3-min period 2nd 3-min period
All subjects (n 40)
Males (n 20)
Females (n 20)
Rate of attempted compressions
Rate of satisfactory compressions
Rate of attempted compressions
Rate of satisfactory compressions
Rate of attempted compressions
Rate of satisfactory compressions
108 105 105 110 105 103 107
82 68 52 70 44 27 66
108 104 106 110 107 102 107
90 70 64 72 53 43 71
107 105 105 109 105 103 106
69 46 16 60 29 22 48
(96 /128) (95 /124) (94 /126) (95 /128) (88 /123) (81 /125) (96 /124)
101 (82 /123)
(55 /100) (29 /76) (16 /67) (43 /92) (8 /83) (3 /75) (40 /78)
46 (23 /76)
Data are median (interquartile range).
(94 /116) (92 /119) (92 /117) (96 /124) (89 /113) (87 /114) (93 /120)
103 (89 /113)
(62 /102) (57 /81) (48 /79) (46 /83) (19 /91) (13 /89) (60 /83)
57 (26 /82)
(97 /131) (95 /112) (95 /130) (95 /124) (87 /116) (54 /116) (98 /130)
101 (80 /118)
(47 /90) (15 /72) (5 /58) (30 /92) (2 /54) (0 /34) (28 /73)
37 (20 /61)
154
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
first 3-min period compared with males (P /0.03) and also tended towards poorer performance during the second period although this latter difference was not significant (P /0.18) (Fig. 2). Seven subjects (five female, two male) were unable to complete the second 3-min period because of exhaustion. We observed good correlations between the number of correct compressions performed over both 3-min periods with height (first period: Spearman r /0.40, P /0.01; second period: r /0.32, P /0.05) and weight (r /0.51, P /0.0008; r /0.48, P /0.002). No significant correlations were found between performance and age or ALS certification. We did not attempt to correlate performance with subjects’ professions as there was such a prominent gender bias.
4. Discussion The performance of effective chest compressions has been recognised as a key determinant of successful outcome from cardiac arrest for over 40 years. Recently the guidelines for performance of chest compressions during BLS have been altered after evidence suggesting that coronary perfusion pressure is better maintained during cardiac arrest when compressions are continuous rather than interrupted to perform ventilation [5]. Accordingly, when following the asystole/pulseless electrical activity limb of the universal resuscitation algorithm, chest compressions should be performed continuously for 3 min provided the patient’s airway has been secured. The effect of rescuer fatigue on chest compressions performed in accordance with the new guidelines has not been studied previously. It is known that performance of chest compressions is physically arduous [8,9] and the results of our study suggest that performance of chest compressions over 3 min declines progressively. This observation is in agreement with two other studies of rescuer fatigue using previous resuscitation guidelines. Hightower et al. in a small study of 11 subjects found that the proportion of satisfactory compressions (attempted at a rate of 80 min 1) decreased from 93 to 39% after 3 min and only 18% were satisfactory after 5 min [6]. Similarly, a decrease in performance was observed in another study after only 1 min and the authors concluded that ‘leaders of CPR teams should ask for a change of rescuer after 1 min of chest compressions’ [7]. This study also demonstrated that rescuers were unaware of the deterioration in the efficacy of their compressions. We observed a gender influence on the performance of satisfactory chest compressions not previously reported [7,10] and our data suggest that height and weight have a significant bearing on the physical capacity of the rescuer. It is possible that continuous
CPR is more demanding than a 15:2 or 5:1 compression /ventilation ratio, and the former may favour the heavier and taller rescuer (who is more likely to be male). Our study is subject to a number of limitations. Although the Resusci-Anne† manikin is widely used in resuscitation skills studies, there are intrinsic inadequacies in the model. For example, the assessment of whether or not a compression is satisfactory is an all or none phenomenon. Thus a subject performing chest compressions just short of the required standard would register as unsatisfactory, whereas it could be argued that in vivo these compressions would be of some value. However, as even optimally performed CPR provides at best only a third of normal cardiac output [11], even a modest deterioration in performance may have a clinically significant adverse effect. In common with most other resuscitation studies, the manikin was located on the floor, which is not typical of most in-hospital cardiac arrests. Whilst our purpose in this was to standardise conditions for rescuers of differing height, our study may have underestimated fatigue in shorter, lighter rescuers who would normally be working at a relative greater mechanical disadvantage when performing compressions on a patient on a hospital bed or trolley. It may be considered that the 30 s interval between successive 3 min episodes of chest compressions, simulating a period for checking the pulse, ECG electrodes, ECG lead and gain settings, is longer than occurs during a typical cardiac arrest. Our data suggest that subjects did benefit from this ‘resting’ period and explains the transient improvement in performance during the first minute of the second period of resuscitation. We chose this interval as the maximum that might reasonably occur during a real cardiac arrest scenario and to avoid the criticism that another arbitrarily chosen resting interval was too short, thereby tending to exaggerate the effects of rescuer fatigue. It is likely that we would have observed an even greater effect with a shorter time interval and thus our observations may again have underestimated the influence of rescuer fatigue. In conclusion, fatigue adversely affects the performance of an individual to maintain satisfactory chest compressions in a manikin model over 3 min. We postulate that some of the potential advantage of improved coronary perfusion offered by continuous chest compressions may be lost because of increasing rescuer fatigue. As individuals appear not to recognise their deterioration in performance, it is essential that cardiac arrest team leaders closely monitor the performance of chest compressions. It may be necessary to consider rotating the rescuer at intervals of less than 3 min if there are signs of decreasing efficacy of chest compressions.
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
References [1] Kouvenhoven WB, Jude JR, Knickerbocker GG. Closed chest cardiac massage. J Am Med Assoc 1960;173:94 /7. [2] de Latorre F, Nolan J, Robertson C, Chamberlain D, Baskett P. European Resuscitation Council Guidelines for Adult Advanced Life Support. Resuscitation 2001;48:211 /21. [3] American Heart Association in collaboration with the International Liaison Committee on Resuscitation (ILCOR). Guidelines 2000 for cardiopulmonary resuscitation and emergency cardiovascular Care-an international consensus on science. Resuscitation 2000;46:1 /448. [4] Lockey AS, Nolan JP. Cardiopulmonary resuscitation in adults (editorial). Br Med J 2001;323:819 /20. [5] Kern KB, Hilwig RW, Berg RA, Ewy GA. Efficacy of chest compression-only BLS CPR in the presence of an occluded airway. Resuscitation 1998;39:179 /88. [6] Hightower D, Thomas SH, Stone CK, Dunn K, March JA. Decay in quality of closed-chest compressions over time. Ann Emerg Med 1995;26:300 /3.
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[7] Ochoa FJ, Ramalle-Gomara E, Lisa V, Saralegui I. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation 1998;37:149 /52. [8] Bridgewater FHG, Bridgewater KJ, Zeitz CJ. Using the ability to perform CPR as a standard of fitness: a consideration of the influence of ageing on the physiological responses of a select group of first aiders performing cardiopulmonary resuscitation. Resuscitation 2000;45:97 /103. [9] Lucia A, de las Heras JF, Perez M, Elvira JC, Carvajal A, Alvarez AJ, Chicharro JL. The importance of physical fitness in the performance of adequate cardiopulmonary resuscitation. Chest 1999;115:158 /64. [10] Sandroni C, Bocci MG, Damiani F, Proietti R, Speranza D. Can the body size affect students’ performance during CPR training. Resuscitation 1997;34:191. [11] Paradis NA, Martin GB, Goetting MG, Rosenberg JM, Rivers EP, Appleton TJ, Nowak RM. Simultaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Insights into mechanisms. Circulation 1989;80:361 /8.
Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min A. Ashton a, A. McCluskey a,*, C.L. Gwinnutt b, A.M. Keenan a a
Department of Anaesthesia, Stepping Hill Hospital, Stockport SK2 7JE, UK Salford Royal Hospital NHS Trust, Hope Hospital, Salford M6 8HD, UK
b
Received 17 January 2002; received in revised form 8 May 2002; accepted 16 May 2002
Abstract Guidelines for the performance of cardiopulmonary resuscitation (CPR) have been revised recently and now advocate that chest compressions are performed without interruption for 3 min in patients during asystole and pulseless electrical activity. The aim of the present study was to determine if rescuer fatigue occurs during 3 min of chest compressions and if so, the effects on the rate and quality of compressions. Forty subjects competent in basic life support (BLS) were studied. They performed continuous chest compressions on a Laerdal SkillmeterTM Resusci-Anne† manikin for two consecutive periods of 3 min separated by 30 s. The total number of compressions attempted was well maintained at approximately 100 min 1 throughout the period of study. However, the number of satisfactory chest compressions performed decreased progressively during resuscitation (P B/0.001) as follows: first min, 82 min 1; second, 68 min 1; third, 52 min 1; fourth, 70 min 1; fifth, 44 min 1; sixth, 27 min 1. We observed significant correlations between the number of satisfactory compressions performed and both height and weight of the rescuer. Female subjects achieved significantly fewer satisfactory compressions compared with males (P /0.03). Seven subjects (five female, two male) were unable to complete the second 3-min period because of exhaustion. We conclude that rescuer fatigue adversely affects the quality of chest compressions when performed without interruption over a 3-min period and that this effect may be greater in females due to their smaller stature. Consideration should be given to rotating the rescuer performing chest compressions after 1 min intervals. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Advanced life support (ALS); Cardiopulmonary resuscitation (CPR); Chest compression; Manikin; Rescuer fatigue
Resumo As recomendac¸o˜es para a reanimac¸a˜o foram recentemente revistas e recomendam agora que as compresso˜es tora´cicas sejam, nos doentes com assistolia e actividade ele´ctrica sem pulso, feitas durante treˆs minutos sem interrupc¸a˜o. Este estudo teve como objectivo verificar se ha´ fadiga do reanimador durante treˆs minutos de compresso˜es tora´cicas e em caso afirmativo se isso influencia a frequeˆncia e qualidade dessas compresso˜es. O estudo foi feito com quarenta indivı´duos treinados em Suporte Ba´sico de Vida (SBV). Fizeram compresso˜es tora´cicas contı´nuas em manequim Laerdale SkillmeterTM e Resusci Anne† em dois perı´odos consecutivos de 3min espac¸ados por um perı´odo de 30s. O nu´mero de compresso˜es, durante o perı´odo do estudo, foi bem mantido a um ritmo de cerca de 100 min 1. Contudo, o nu´mero de compresso˜es satisfato´rias foi diminuindo ao longo da reanimac¸a˜o (P B/0.001) da seguinte forma: primeiro minuto 82 min 1, segundo 68 min 1, terceiro 52 min 1, quarto 70 min 1, quinto 44 min 1, e sexto 27 min 1. Verificou-se haver uma boa correlac¸a˜o entre o nu´mero de compresso˜es eficazes e o peso e altura do reanimador. As mulheres fizeram significativamente menos compresso˜es eficazes do que os homens (P /0.03) . Sete dos reanimadores (cinco mulheres e dois homens) foram incapazes de completar o segundo perı´odo de treˆs minutos de compresso˜es tora´cicas por exausta˜o. Concluı´mos que o cansac¸o dos reanimadores afecta negativamente a qualidade das compresso˜es tora´cicas, quando efectuada sem interrupc¸a˜o
* Corresponding author. Tel.: /44-161-419-5869; fax: /44-161-419-5045 E-mail address: [email protected] (A. McCluskey). 0300-9572/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 0 - 9 5 7 2 ( 0 2 ) 0 0 1 6 8 - 5
152
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
durante treˆs minutos e que este efeito pode ser maior nas mulheres por causa da sua menor estatura. Justifica-se considerar a hipo´tese de rodar os reanimadores ao fim de um minuto de compresso˜es tora´cicas. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Palavras chave: Suporte Avanc¸ado de Vida (SAV); Reanimac¸a˜o cardio-pulmonar; Compresso˜es tora´cicas; Fadiga do reanimador
Resumen Las guı´as para la realizacio´n de reanimacio´n cardiopulmonar (RCP) han sido revisadas recientemente y ahora sostienen que las compresiones sean realizadas sin interrupcio´n por tres minutos en pacientes en asistolı´a y actividad ele´ctrica sin pulso. El objetivo de este estudio fue determinar si ocurre fatiga del reanimador durante tres minutos de compresiones tora´cicas, y si es ası´, los efectos sobre la frecuencia y profundidad de las compresiones. Se estudiaron cuarenta sujetos competentes en soporte vital ba´sico (BLS). Realizaron compresiones tora´cicas continuas en un maniquı´ Laerdal SkillmeterTM Resusci-Anne† por dos perı´odos consecutivos de 3 minutos, separados por 30 segundos. El nu´mero total de compresiones intentadas fue bien mantenido por aproximadamente 100 min 1 a lo largo de todo el perı´odo de estudio. Sin embargo, el numero de compresiones tora´cicas satisfactorias realizadas disminuyo´ progresivamente durante la resucitacio´n (P B/0.001) de la siguiente manera: primer minuto 82 min 1; segundo, 68 min 1; tercero, 52 min 1; cuarto, 70 min 1; quinto, 44 min 1; sexto, 27 min 1. Encontramos correlaciones significativas entre el numero de compresiones tora´cicas satisfactorias realizadas y tanto la estatura como el peso del reanimador. Reanimadoras femeninas alcanzaron significativamente menos compresiones satisfactorias comparadas con los reanimadores varones (P /0.03). Siete sujetos (cinco mujeres, dos varones) fueron incapaces de completar el segundo perı´odo de tres minutos por estar exhaustos. Concluimos que la fatiga del reanimador afecta adversamente la calidad de las compresiones tora´cicas cuando son realizadas sin interrupcio´n durante perı´odos de tres minutos y que este efecto puede ser mayor en mujeres debido a su menor estatura. Debe darse consideracio´n a la rotacio´n de los reanimadores que realizan las compresiones tora´cicas despue´s de intervalos de un minuto. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Palabras clave: Soporte vital avanzado (SVA); Reanimacio´n cardiopulmonar (RCP); Compresiones tora´cicas; Maniquı´; Fatiga del reanimador
1. Introduction
2. Materials and methods
Chest compression has been one of the principal elements of circulatory support during cardiopulmonary resuscitation (CPR) for more than 40 years [1]. The guidelines for performance of CPR during cardiac arrest have been revised recently [2,3] and reflect a stronger evidence base [4]. Once the airway has been secured with a cuffed tracheal tube, chest compressions now continue uninterrupted at a rate of 100 min 1. Thus, when following the asystole/pulseless electrical activity limb of the universal resuscitation algorithm, chest compressions must be performed continuously for 3 min. This reflects the observation that uninterrupted chest compressions may improve coronary perfusion [5]. Anecdotally we have noticed that some rescuers find it difficult to maintain their performance over this relatively prolonged period because of fatigue, leading on occasions to an ‘unofficial’ handover to another rescuer before the end of the 3 min cycle. It has been suggested previously that rescuer fatigue may become apparent after only a min of chest compressions [6,7]. Furthermore, fatigue and the resulting decrease in performance may not be recognised by the rescuer [7]. The aims of the present study were to evaluate the effect of rescuer fatigue on the rate and quality of chest compressions when following the new resuscitation guidelines and the influence of rescuer gender, weight and height on performance.
Forty subjects (20 male, 20 female) competent in basic life support (BLS) were recruited from doctors and nurses working in the Intensive Care Unit, Emergency Department, Emergency Admissions Unit and Operating Room Recovery Area of a large district general hospital in the UK. A Laerdal SkillmeterTM ResusciAnne† manikin located on the floor was adopted as our experimental model as it is used within the hospital for CPR training. The integral Skillmeter records both the total number of compressions attempted and the number of these considered satisfactory. For the purposes of the study a satisfactory compression was defined as one with a depth of 4 /5 cm. Subjects were immediately directed to rectify incorrect hand placement if necessary. After a preliminary period of familiarisation and practice during which time the subjects were permitted to view the display of the Skillmeter in order to perfect their performance, they performed 3 min of continuous chest compressions on the manikin aiming for a rate of 100 min 1. After a 30 s interval representing a maximal period during which the pulse, ECG electrodes, ECG lead and gain settings would be checked during an actual cardiac arrest, a further 3 min of chest compressions were performed as before. For each subject the following demographic parameters were recorded: rescuer gender, age, weight, height, profession (doctor or nurse) and whether or
A. Ashton et al. / Resuscitation 55 (2002) 151 /155
not the subject was a certified advanced life support (ALS) provider. Data from a preliminary pilot study of the first ten subjects with a mean (S.D.) decline in performance of 25 (43) satisfactory compressions min 1 between the first and third min of resuscitation were used to determine that a sample size of 38 subjects was required to detect a decline in performance of 20 satisfactory compressions min 1 with 80% power. Statistical analyses were performed using SPSS version 7. Continuous normative data were analysed using Student’s unpaired t -test. Change in performance over time of chest compressions within subjects was analysed using Friedman’s non-parametric repeated measures analysis of variance (ANOVA) with Dunn’s multiple comparisons correction used as appropriate. Between group comparisons were made using the Mann /Whitney U -test. A value of P B/0.05 was considered significant.
153
Fig. 1. Effect of rescuer fatigue on performance of chest compressions. Data are median (interquartile range). *P B/0.05; **P B/0.01; ***P B/ 0.001 for the difference from first minute of respective period of chest compressions.
3. Results Forty subjects (20 males and 20 females) took part in the study. Twenty-three were nurses (17 females, six males) and 17 were doctors (three females, 14 males). Male subjects were significantly heavier (mean 78.2 (S.D. 10.4) vs. 66.1 (12.8) kg, P /0.0024) and taller (177.5 (5.7) vs. 161.9 (6.7) cm, P B/0.0001) than their female counterparts. The number of compressions attempted was well maintained at approximately 100 min 1 (Table 1). Male and female subjects did not differ in the rate of compressions attempted. However, the number of satisfactory chest compressions performed by the entire study group decreased during both 3-min periods of simulated resuscitation (P B/0.0001) (Fig. 1). Performance recovered transiently during the fourth minute (P B/0.05), following the 30 s interval separating the two
Fig. 2. Comparison of rescuer fatigue between male and female subjects during each 3-min period of chest compressions. Data are median (interquartile range). *P /0.03.
periods. Significantly fewer satisfactory compressions were performed during the second 3-min period compared with the first (P /0.02). Female subjects achieved significantly fewer satisfactory compressions during the
Table 1 Rate of attempted chest compressions and rate satisfactory (min 1) during simulated CPR Minute
1 2 3 4 5 6 1st 3-min period 2nd 3-min period
All subjects (n 40)
Males (n 20)
Females (n 20)
Rate of attempted compressions
Rate of satisfactory compressions
Rate of attempted compressions
Rate of satisfactory compressions
Rate of attempted compressions
Rate of satisfactory compressions
108 105 105 110 105 103 107
82 68 52 70 44 27 66
108 104 106 110 107 102 107
90 70 64 72 53 43 71
107 105 105 109 105 103 106
69 46 16 60 29 22 48
(96 /128) (95 /124) (94 /126) (95 /128) (88 /123) (81 /125) (96 /124)
101 (82 /123)
(55 /100) (29 /76) (16 /67) (43 /92) (8 /83) (3 /75) (40 /78)
46 (23 /76)
Data are median (interquartile range).
(94 /116) (92 /119) (92 /117) (96 /124) (89 /113) (87 /114) (93 /120)
103 (89 /113)
(62 /102) (57 /81) (48 /79) (46 /83) (19 /91) (13 /89) (60 /83)
57 (26 /82)
(97 /131) (95 /112) (95 /130) (95 /124) (87 /116) (54 /116) (98 /130)
101 (80 /118)
(47 /90) (15 /72) (5 /58) (30 /92) (2 /54) (0 /34) (28 /73)
37 (20 /61)
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A. Ashton et al. / Resuscitation 55 (2002) 151 /155
first 3-min period compared with males (P /0.03) and also tended towards poorer performance during the second period although this latter difference was not significant (P /0.18) (Fig. 2). Seven subjects (five female, two male) were unable to complete the second 3-min period because of exhaustion. We observed good correlations between the number of correct compressions performed over both 3-min periods with height (first period: Spearman r /0.40, P /0.01; second period: r /0.32, P /0.05) and weight (r /0.51, P /0.0008; r /0.48, P /0.002). No significant correlations were found between performance and age or ALS certification. We did not attempt to correlate performance with subjects’ professions as there was such a prominent gender bias.
4. Discussion The performance of effective chest compressions has been recognised as a key determinant of successful outcome from cardiac arrest for over 40 years. Recently the guidelines for performance of chest compressions during BLS have been altered after evidence suggesting that coronary perfusion pressure is better maintained during cardiac arrest when compressions are continuous rather than interrupted to perform ventilation [5]. Accordingly, when following the asystole/pulseless electrical activity limb of the universal resuscitation algorithm, chest compressions should be performed continuously for 3 min provided the patient’s airway has been secured. The effect of rescuer fatigue on chest compressions performed in accordance with the new guidelines has not been studied previously. It is known that performance of chest compressions is physically arduous [8,9] and the results of our study suggest that performance of chest compressions over 3 min declines progressively. This observation is in agreement with two other studies of rescuer fatigue using previous resuscitation guidelines. Hightower et al. in a small study of 11 subjects found that the proportion of satisfactory compressions (attempted at a rate of 80 min 1) decreased from 93 to 39% after 3 min and only 18% were satisfactory after 5 min [6]. Similarly, a decrease in performance was observed in another study after only 1 min and the authors concluded that ‘leaders of CPR teams should ask for a change of rescuer after 1 min of chest compressions’ [7]. This study also demonstrated that rescuers were unaware of the deterioration in the efficacy of their compressions. We observed a gender influence on the performance of satisfactory chest compressions not previously reported [7,10] and our data suggest that height and weight have a significant bearing on the physical capacity of the rescuer. It is possible that continuous
CPR is more demanding than a 15:2 or 5:1 compression /ventilation ratio, and the former may favour the heavier and taller rescuer (who is more likely to be male). Our study is subject to a number of limitations. Although the Resusci-Anne† manikin is widely used in resuscitation skills studies, there are intrinsic inadequacies in the model. For example, the assessment of whether or not a compression is satisfactory is an all or none phenomenon. Thus a subject performing chest compressions just short of the required standard would register as unsatisfactory, whereas it could be argued that in vivo these compressions would be of some value. However, as even optimally performed CPR provides at best only a third of normal cardiac output [11], even a modest deterioration in performance may have a clinically significant adverse effect. In common with most other resuscitation studies, the manikin was located on the floor, which is not typical of most in-hospital cardiac arrests. Whilst our purpose in this was to standardise conditions for rescuers of differing height, our study may have underestimated fatigue in shorter, lighter rescuers who would normally be working at a relative greater mechanical disadvantage when performing compressions on a patient on a hospital bed or trolley. It may be considered that the 30 s interval between successive 3 min episodes of chest compressions, simulating a period for checking the pulse, ECG electrodes, ECG lead and gain settings, is longer than occurs during a typical cardiac arrest. Our data suggest that subjects did benefit from this ‘resting’ period and explains the transient improvement in performance during the first minute of the second period of resuscitation. We chose this interval as the maximum that might reasonably occur during a real cardiac arrest scenario and to avoid the criticism that another arbitrarily chosen resting interval was too short, thereby tending to exaggerate the effects of rescuer fatigue. It is likely that we would have observed an even greater effect with a shorter time interval and thus our observations may again have underestimated the influence of rescuer fatigue. In conclusion, fatigue adversely affects the performance of an individual to maintain satisfactory chest compressions in a manikin model over 3 min. We postulate that some of the potential advantage of improved coronary perfusion offered by continuous chest compressions may be lost because of increasing rescuer fatigue. As individuals appear not to recognise their deterioration in performance, it is essential that cardiac arrest team leaders closely monitor the performance of chest compressions. It may be necessary to consider rotating the rescuer at intervals of less than 3 min if there are signs of decreasing efficacy of chest compressions.
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