The Journal of Maternal-Fetal & Neonatal Medicine
ISSN: 1476-7058 (Print) 1476-4954 (Online) Journal homepage: http://www.tandfonline.com/loi/ijmf20
Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation Anne Marthe Boldingh, Thomas Hagen Jensen, Ane Torvik Bjørbekk, Anne Lee Solevåg & Britt Nakstad To cite this article: Anne Marthe Boldingh, Thomas Hagen Jensen, Ane Torvik Bjørbekk, Anne Lee Solevåg & Britt Nakstad (2015): Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation, The Journal of Maternal-Fetal & Neonatal Medicine, DOI: 10.3109/14767058.2015.1119115 To link to this article: http://dx.doi.org/10.3109/14767058.2015.1119115
Accepted author version posted online: 13 Nov 2015. Published online: 15 Dec 2015. Submit your article to this journal
Article views: 50
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ijmf20 Download by: [University of Exeter]
Date: 01 April 2016, At: 21:10
http://informahealthcare.com/jmf ISSN: 1476-7058 (print), 1476-4954 (electronic) J Matern Fetal Neonatal Med, Early Online: 1–6 ! 2015 Taylor & Francis. DOI: 10.3109/14767058.2015.1119115
ORIGINAL ARTICLE
Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation Anne Marthe Boldingh1,2, Thomas Hagen Jensen1*, Ane Torvik Bjørbekk1*, Anne Lee Soleva˚g1, and Britt Nakstad1,2 Department of Pediatric and Adolescent Medicine, Akershus University Hospital, Lørenskog, Norway and 2Akershus Faculty Division, Institute of Clinical Medicine, University of Oslo, Lørenskog, Norway
Downloaded by [University of Exeter] at 21:10 01 April 2016
1
Abstract
Keywords
Objective: To assess development of objective, subjective and indirect measures of fatigue during simulated infant cardiopulmonary resuscitation (CPR) with two different methods. Methods: Using a neonatal manikin, 17 subject-pairs were randomized in a crossover design to provide 5-min CPR with a 3:1 chest compression (CC) to ventilation (C:V) ratio and continuous CCs at a rate of 120 min1 with asynchronous ventilations (CCaV-120). We measured participants’ changes in heart rate (HR) and mean arterial pressure (MAP); perceived level of fatigue on a validated Likert scale; and manikin CC measures. Results: CCaV-120 compared with a 3:1 C:V ratio resulted in a change during 5-min of CPR in HR 49 versus 40 bpm (p ¼ 0.01), and MAP 1.7 versus 2.8 mmHg (p ¼ 0.03); fatigue rated on a Likert scale 12.9 versus 11.4 (p ¼ 0.2); and a significant decay in CC depth after 90 s (p ¼ 0.03). Conclusions: The results indicate a trend toward more fatigue during simulated CPR in CCaV-120 compared to the recommended 3:1 C:V CPR. These results support current guidelines.
Manikin, neonatology, quality
Introduction Guidelines recommend using a 3:1 chest compression (CC) to ventilation (C:V) ratio for cardiopulmonary resuscitation (CPR) at birth. CCs should be delivered at a rate of 90 min1 synchronized with ventilations at a rate of 30 min1 to achieve a total of 120 events min1. However, the most effective method remains controversial [1]. There is limited evidence supporting one C:V ratio over another, but mathematical models suggest that higher CC rates than the currently recommended 90 min1 could optimize systemic perfusion [2]. In asphyxiated piglets, Schmo¨lzer et al. demonstrated that the time to return of spontaneous circulation (ROSC) was similar when using a 3:1 C:V ratio as compared to continuous CCs at a rate of 90 min1 with asynchronous ventilations (CCaV-90) [3]. In another study, using the same piglet model, better regional and systemic hemodynamics and shorter time to ROSC was achieved with uninterrupted CCs at a rate of 120 min1 when combined with sustained inflations [4]. Neonates may benefit from higher CC rates and possibly alternative C:V ratios, but the feasibility in terms of physical demands of performing uninterrupted CCs at higher CC rates remains to be determined. Li et al. investigated decay from
*Both contributed equally as second authors. Address for correspondence: Anne Marthe Boldingh, Department of Paediatric and Adolescent Medicine, Akershus University Hospital, P.O. Box 1000, N-1478 Lørenskog, Norway. Tel: +47 97006821. Fax: +47 67960900. E-mail: [email protected]
History Received 11 August 2015 Revised 8 November 2015 Accepted 9 November 2015 Published online 8 December 2015
baseline in peak CC pressure, used as a surrogate for fatigue, during a 10-min period of 3:1 C:V CPR, CCaV-90 and continuous CCs at a rate of 120 min1 with asynchronous ventilations (CCaV-120) [5]. They found a significant decay from baseline, occurring at 156, 96, and 72 s in 3:1, CCaV-90, and CCaV-120 groups. An adult-manikin study investigated performer fatigue comparing 30:2 and 15:2 C:V ratios and found similar objective physiologic measures, but a subjectively higher level of fatigue [6]. However, the two-thumb technique for neonatal CCs [1] may not be comparable with adult CPR, and thus objective and subjective measures of rescuers fatigue during neonatal CPR should be investigated. The primary aim of this study was to compare physiologic measures of rescuer fatigue during 5-min CPR sessions using the 3:1 C:V ratio and CCaV-120 in a population of healthcare workers with daily neonatal responsibilities. Furthermore, we sought to evaluate perceived fatigue and changes in CC quality as indirect measures of fatigue. We hypothesized that CCaV-120 compared to 3:1 C:V CPR would be more exhausting to perform resulting in a higher rescuer heart rate (HR) and mean arterial pressure (MAP) over time, greater perceived exhaustion, and a larger decay in CC depth over time.
Methods Settings and participants This randomized crossover manikin study was performed during a pre-defined 1-week period at Akershus University
2
A. M. Boldingh et al.
Hospital in February 2014. The institutional privacy legislation authority approved the study. Because the study did not involve patients, and was considered very low-risk for the participating health care workers, the Regional Ethics Committees for Medical Research did not consider its approval necessary. A convenience sample of 34 subjects was recruited from the Department of Pediatric and Adolescent Medicine and the Department of Obstetrics (doctors (n ¼ 7), nurses (n ¼ 16) and midwifes (n ¼ 11)) after written informed consent. Exclusion criteria were any medical condition contraindicating the exertion associated with CPR. For each participant we registered by questionnaire, the number of CPR episodes during the career, episodes of weekly physical activity and the last time they participated in a CPR course.
Downloaded by [University of Exeter] at 21:10 01 April 2016
Experimental protocol We used a Resusci Baby QCPR manikin [7] (Laerdal Medical, Stavanger, Norway), simulating a 6-kg infant, with a non-progressive spring, needing a weight application of 6 kg (13 lb) to achieve a CC depth of 36 mm, equaling 1/3 of the anterior–posterior diameter of the manikin’s chest. Maximum CC depth was 40 mm. A 240 ml self-inflating bag with a facemask size 0/1 was used (Laerdal Medical, Stavanger, Norway), pressure relief valve at 35 cmH2O, no gas flow or peak end expiratory pressure valve. Subject-pairs provided 5-min CPR, randomized (http:// www.randomizer.org) to start with either a 3:1 C:V ratio (with a pause after every third CC to deliver one inflation) or CCaV-120 (uninterrupted CCs at a rate of 120 min1 with asynchronous ventilations at a rate of 40–60 min1), and to start with performing either ventilation or CCs. For each CC method, both subjects in each pair performed CCs once and assisted ventilations once; i.e. every subject performed in total four 5-min CPR sessions, separated by a rest of minimum 1-h between the first and the second CC method. Before the experiments each subject made him/herself comfortable with the equipment used. A standardized instruction was given before start: CCs by the two-thumb encircling hands method centered over the lower third of the sternum and a CC depth of 1/3 the anterior–posterior diameter of the chest [1]. CCs and ventilations should be given at a rate to achieve 120 events min1 and attention should be given to adequate inflation of the lungs [1]. During the sessions, metronome guidance at a rate of 120 min1 and verbal motivation and feedback on techniques were given. Immediately after completing CPR, participants assessed their level of perceived fatigue on a Likert scale. Data collection We collected participant demographic and baseline characteristics including age, gender, body mass index (BMI), HR (beats per minute, bpm), MAP (mmHg) and respiratory rate. Maximum HR was calculated by the formula (208–0.7 age), accuracy ± 20 bpm [8]. Baseline HR, respiratory rate and MAP were measured before initiation of CPR, using a Nihon Kohden BSM-2301K bedside monitor (Nihon Kohden Corporation, Tokyo, Japan) and Kendall hydrogel ECG electrodes (Covidien, Minneapolis, MN).
J Matern Fetal Neonatal Med, Early Online: 1–6
We evaluated objective fatigue by changes in HR, MAP and respiratory rate. The participants’ perceived level of fatigue after each CPR session was measured using the validated Likert scale (range 6–11: very, very light to fairly light, 12–15: somewhat hard to hard and 16–20: very hard to very, very hard). The seemingly odd range of 6–20 was chosen for comparison to the general HR of a healthy adult by multiplying by 10. After having performed all CPR sessions the participants completed a brief survey about how many more minutes they thought they would be able to perform CPR using each method; and which method they preferred. CPR quality measures were recorded using equipment from Laerdal Medical (Stavanger, Norway). The manikin was connected to a computer digitizing ventilation and CC values with Protocol Emulator recording program. The variables were displayed in BLS Emulator Viewer, version 1.0.5. A linear optical recorder measured CC rate and depth (depth ± 2 mm). CC measures were: the number of delivered CCs, CC rate, absolute and relative depth (mm), leaning (mm) and the proportion of CCs with a depth 1/3 the anterior– posterior diameter of the chest, i.e. 36 mm. Absolute depth was defined as the distance from a turning point of maximum force to baseline-at-start; relative depth as the distance from a turning point of maximum force to a turning point of minimum force. The depth of this latter turning point is a composite of incomplete chest wall recoil, i.e. leaning, thus absolute depth ¼ relative depth + leaning [9]. In all sessions we asked the participant to start with the thumbs above the manikin’s chest to ensure a baseline measure of 0 mm. Statistics Based on pilot data we calculated that 19 subjects were required to have a 80% chance of detecting, as significant at the 5% level, a HR difference from 1-min to 5-min of 29 in the 3:1 ratio compared to 43 during CCaV-120. As this was a small number, we decided to do a convenient sampling due to no ethical limitations. Pilot data are not included in the final analyses. Data are presented as means with 95% confidence interval (CI) and frequencies with percentages. We analyzed changes over time in the dependent variables HR, respiratory rate, the number of CCs performed and CC rate, each consecutive 1-min segment; CC depth and leaning for each consecutive 15-s segment, and MAP as a pre- and post-test measurement. Baseline was defined as the measured HR at start, and baseline for CC depth as the average depth generated in the first 15 s of CCs. Decay in CC depth was defined as a statistical significant decay from the respective baseline. Participant HR, MAP and respiratory rate for each ratio-group before each CPR session were compared using a paired t-test with 95% CI. The number of delivered CCs per minute was compared to the methods respective target; 90 CCs per minute in 3:1 C:V ratio and 120 CCs per minute in CCaV-120, using a one-sample Student’s t-test. A random intercept model, random for individuals, was estimated to assess the trend in HR from baseline to the end of the session. The fixed independent variables were time as a categorical variable, a dummy distinguishing between the ratio-groups, sequence-of-period to control for possible
Fatigue in infant CPR
DOI: 10.3109/14767058.2015.1119115
Downloaded by [University of Exeter] at 21:10 01 April 2016
fatigue/carry-over effects, and an interaction-term between time and ratio-group. Weekly physical activity and BMI were excluded from the model, as they did not change the estimates. As a secondary analysis, joint-test and pairwise comparisons between each 1-min segment and baseline were performed with the estimated contrast from the model. Similarly, secondary outcomes were fitted using the same model building and contrast testing. For analysis of outcome variables with 15-s segments, time and where necessary a quadratic term for time (time2), were included as continuous variables. An interaction-term between time2 and ratio-group was considered and included if significant. If the global timeeffect was significant, pairwise comparisons between ratiogroups at each time-point were performed with the estimated contrast. A p value50.05 was considered significant. All analyses were calculated with Stata software, version 13.1 (StataCorp, Lakeway, TX).
Results We enrolled 34 subjects, mean (95% CI) age was 40.6 (36.8; 44.3) years, 31 (91.2%) of the subjects were female; and 23 (64.6%) had completed a CPR training course within the last three months, 7 (20.6%) within the last 12 months and 4 (11.8%) had never completed a CPR course. The number of CPR episodes with CCs plus assisted ventilations that the subjects had participated in during their career was: no episodes 19 (55.9%); 1–5 episodes 11 (32.3%); 5–10 episodes 3 (8.8%); and more than 10 episodes 1 (2.9%). Subjects’ weekly physical activity was: zero 6 (17.6%), 1–3 times 26 (76.5%) and 4–6 times 2 (5.9%).
3
Average subjective exhaustion was ‘‘somewhat hard’’ for 3:1 C:V CPR and ‘‘hard’’ for CCaV-120 on the Likert scale, p50.001. When using the 3:1 C:V ratio, 30 (88.2%) subjects estimated being able to continue CPR for at least two more minutes, compared to only 19 (56%) when using CCaV-120. Thirty (80%) of the participants preferred the 3:1 CPR method. CPR quality We excluded three CC recordings for each of the 3:1 C:V ratio and CCaV-120 due to technical problems. There were significant differences between CCs in CCaV-120 versus 3:1 C:V CPR (Table 2). The proportion of CCs with adequate depth (36 mm) was 90.5% for 3:1 C:V ratio and 60.1% in CCaV-120. There was a difference between CC groups for absolute depth (p50.001), relative depth (p ¼ 0.016) and leaning (p ¼ 0.039). The difference in absolute and relative depth between 3:1 C:V CPR and CCaV-120 increased from the first 15 s to the last 15 s: from 2.4 to 3.3 mm for absolute depth, and from 0.9 to 2.5 mm for relative depth (Figure 2). Compared with baseline, absolute depth in CCaV120 decreased significantly 90 s after commencement of CCs (p ¼ 0.03). Absolute CC depth was reduced by 3% (1.2 mm) after three minutes, and by 7.8% (3.1 mm) after five minutes. Analyses adjusting for the amount of weekly physical activity; Likert score; and BMI confirmed the original findings.
Objective and subjective rescuer fatigue All the included participants completed all four 5-min CPR sessions. There were no significant differences between CC methods in baseline HR, MAP and respiratory rate. One outlier-measure of HR was excluded from statistics. Calculated BMI and maximum HR (SD) were 23.9 (3.4) kg/m2 and 180 (8) bpm, respectively. At the end of the session, 3:1 C:V CPR resulted in 60% and CCaV-120 65% of calculated maximum HR, p ¼ 0.03. The average of the participants’ objective and subjective measures of fatigue are presented in Table 1. HR from baseline until 5-min, increased with 40 and 49 bpm for 3:1 C:V CPR and CCaV-120, respectively (Figure 1). Analyses adjusting for the amount of physical activity and BMI confirmed the original findings.
Figure 1. Average for each 1-min segment (raw data). Random intercept model (random: id), controlled for sequence of period. Significant difference between 3:1 and CCaV-120 at 5th minute, p¼0.029. There was a significant change from baseline for both groups when comparing each 1-min sequence with baseline. CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations, HR: heart rate.
Table 1. Average measures of participants’ physiological measures and subjective perception of fatigue (Likert-scale rating) in chest compression to ventilation ratio 3:1 and CCaV-120. Variable Max HR (bpm) DHR DMAP (mmHg) DRF Likert-score compressions
3:1 118 39 2.8 15 12.6
(109; 126) (33; 46) (6.5; 0.8) (12; 18) (11.6; 13.5)
CCaV-120 122 49 1.7 14 14.9
(114; 131) (43; 55) (1.9; 5.3) (11; 16) (14.0; 15.8)
p value
ICC
0.05 0.005 0.013 0.273 50.001
0.85 0.58 0.43 0.3 0.72
Values are mean (95% confidence interval). Random intercept model (random effect: subject id), controlled for sequence of period. Baseline group 3:1 ratio. D ¼ variable end minus variable start. CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations; HR: heart rate; ICC: intra cluster correlation coefficient; RF: respiratory frequency.
4
A. M. Boldingh et al.
J Matern Fetal Neonatal Med, Early Online: 1–6
Discussion In this study, we used an infant manikin to study rescuer fatigue during simulated CPR. In a population of healthcare workers with daily neonatal responsibilities, CCaV-120 resulted in a greater increase in rescuer HR and MAP and perceived fatigue, compared to the recommended 3:1 C:V ratio. In CCaV-120 CC depth decreased significantly during Table 2. Chest compression parameters in chest compression to ventilation ratio 3:1 and CCaV-120. Explanatory variable
Downloaded by [University of Exeter] at 21:10 01 April 2016
Number of CC/min CC rate CC depth (absolute) (mm) CC depths (relative) (mm) Leaning (mm) Adequate depth (41/3 AP diameter) (%)
3:1 89 129 40.2 37.6 2.6 89.9
(87; 91) (127; 131) (39.5; 40.9) (36.5; 38.7) (1.8; 3.3) (81.8; 97.9)
CCaV-120 113 125 38.3 34.5 3.8 58.0
(106; 120) (123; 126)** (36.9; 39.6)** (33.1; 35.8)** (3.0; 4.6)* (44.9; 71.1)**
Values are mean (95% confidence interval). The number of CC/min was compared to the respective target in each C:V group; 90 CC/min in 3:1 and 120 CC/min in CCaV-120. Random intercept model (random effect: subject id), controlled for sequence of period, baseline group 3:1 ratio. AP: anterior posterior; CC: chest compression; CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations. *Significant at p5(0).05. **Significant at p50.001.
the 5-min CPR session and more CCs with inadequate depth were delivered compared to the 3:1 C:V ratio. These findings indicate that CCaV-120 is more exhausting than 3:1 C:V CPR. This is the first study to measure resuscitators’ physiological responses while performing CPR with different CC methods in an infant manikin. Previous infant manikin studies have investigated different C:V ratios with respect to CC and ventilation parameters [5,10,11]. One of these investigated fatigue, using the amount of pressure in a saline-bag inside the manikin’s chest as a fatigue surrogate. During a 10-min session, the peak pressure decreased more in CCaV-120 and CCaV-90 than in 3:1 C:V CPR [5]. In the current study, CCaV-120 compared with a 3:1 C:V ratio, resulted in a HR closer to an estimated age-adjusted maximum and a significantly greater change in HR and MAP. Although the measured changes were small, our combined results indicate that CCaV-120 is more exhausting than a 3:1 C:V ratio. A possible explanation may be the brief pauses in CCs in 3:1 C:V CPR. Also, the degree of physical fitness may impact physiological differences and some studies have suggested that a smaller stature and limited physical fitness can adversely affect CPR performance [12–14]. We did not test the physical fitness of the participants, but adjusting for weekly physical activity and BMI did not significantly change our conclusions. Furthermore, the subjects operated as their own controls in a crossover study design. However, as the
Figure 2. Average mean for each 15-s segment (raw data). Random intercept models (random: id), controlled for sequence of period, baseline group: 3:1 ratio; post-estimation pairwise contrast testing for differences between groups from baseline. Absolute depth: Difference between groups over time, p50.001, difference between groups from baseline, p50.001 at all time points. Relative depth: Difference between groups over time, p ¼ 0.016, difference between groups from baseline, p50.001 at all time points. Leaning: Difference between groups over time, p ¼ 0.039, difference between groups from baseline, 15–270 s: p50.001; 275–300 s: p ¼ 0.012. C: chest compression; CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations, HR: heart rate.
Fatigue in infant CPR
Downloaded by [University of Exeter] at 21:10 01 April 2016
DOI: 10.3109/14767058.2015.1119115
majority of our participants were female, with potentially smaller stature than their male counterparts, we do not know if the fatiguing effect of the two CC methods would have been the same had we included more male participants. But as the gender distribution in our study closely reflects the gender distribution at the ward, we believe our results are generalizable to clinical practice. Fatigue can have physical or mental causes. Physical fatigue is the transient inability of a muscle to maintain optimal physical performance and is made more severe by intense physical exercise [15]. Mental fatigue is a temporary inability to maintain optimal cognitive performance and has also been shown to decrease physical performance [16]. A person’s intrinsic motivation is important for optimizing physical performance [17]. We aimed to explore physical fatigue and thus we motivated the participants with verbal feedback during the sessions to optimize performance. We argue that the physiological difference we observed is a consequence of physical, not mental fatigue. Rating of perceived fatigue was higher in CCaV-120 compared to the 3:1 C:V ratio. This finding is supported by the differences in the physiologic measures of fatigue, the smaller proportion of adequate CCs, and more leaning in CCaV-120 compared to the 3:1 C:V ratio. By self-assessment more subjects estimated being able to continue CPR for at least two additional minutes when using the 3:1 C:V ratio compared to CCaV-120. These results are in agreement with other studies [5,10]. Rescuer fatigue can affect CC depth [6] and thus the coronary perfusion pressure [18]. We demonstrated that CCaV-120 resulted in a significant decline in CC depth 90 s after commencement of CCs and a 7.8% reduction in CC depth after 5 min. Li et al. [5] found a reduction in peak pressure in CCaV-120 of 50% using the same size manikin, but different setup, which may explain the difference in effect size. In agreement with Li et al. [5], if using CCaV-120, we recommend CC operator to switch every 90 s to avoid suboptimal CPR quality. Importantly, this should not compromise CC quality by increasing interruptions in CC and hands-off-time. Until now, no studies have compared different techniques in manikins to real-life situations [5,10,19,20], which makes it difficult to extrapolate the results to real-life situations. This represents a limitation to our study, however, the objective physiologic measures strengthen the indirect CC findings of fatigue measured in the manikin. The CPR duration in our experiments was five minutes although current resuscitation guidelines advise to continue CPR if HR remains undetectable for up to 10 min [1]. The rationale for conducting 5-min trials was twofold: A pilot study showed fatigue already after two minutes, and in real-life it is not common for the same rescuer to perform CCs for 10 min or more. The rest time between CC methods could potentially have been longer. However, the baseline measurements of HR and MAP were similar and none of the subjects reported to be fatigued when starting their second CC session. Finally, we enrolled subjects with limited CPR experience and who had not participated in a CPR course the last 12 months. This might have affected the results. However, all subjects were given a standardized briefing and they were given time before the session to
5
practice CPR techniques and make themself comfortable with the equipment used. In conclusion, this study indicates that performing CCs is more exhausting with CCaV-120 than a 3:1 C:V ratio as measured by a higher rescuer HR and MAP, greater perceived fatigue and decay in CC depth.
Acknowledgements We wish to thank Helge Myklebust, Øystein Gomo and Mette Stavland, Laerdal Medical for technical support, the participating neonatal healthcare professionals who contributed to this study and Jonas Christoffer Lindstrøm, HØKH, Akershus University Hospital, Norway, for statistical guidance.
Declaration of interest A.M.B. has received financial support from the Laerdal Foundation for Acute Medicine. Laerdal Medical (Stavanger, Norway) provided the manikin for the study. The other authors report no declarations of interest.
References 1. Kattwinkel J, Perlman JM, Aziz K, et al. Part 15: neonatal resuscitation: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S909–19. 2. Babbs CF, Meyer A, Nadkarni V. Neonatal CPR: room at the top – a mathematical study of optimal chest compression frequency versus body size. Resuscitation 2009;80:1280–4. 3. Schmolzer GM, O’Reilly M, Labossiere J, et al. 31 Compression to ventilation ratio versus continuous chest compression with asynchronous ventilation in a porcine model of neonatal resuscitation. Resuscitation 2014;85:270–5. 4. Schmolzer GM, O’Reilly M, Labossiere J, et al. Cardiopulmonary resuscitation with chest compressions during sustained inflations: a new technique of neonatal resuscitation that improves recovery and survival in a neonatal porcine model. Circulation 2013;128: 2495–503. 5. Li ES, Cheung PY, O’Reilly M, et al. Rescuer fatigue during simulated neonatal cardiopulmonary resuscitation. J Perinatol 2015; 35:142–5. 6. Vaillancourt C, Midzic I, Taljaard M, Chisamore B. Performer fatigue and CPR quality comparing 30:2 to 15:2 compression to ventilation ratios in older bystanders: a randomized crossover trial. Resuscitation 2011;82:51–6. 7. Laerdal Medical AS. ResusciÕ Baby with QCPR. Laerdal Medical AS; 2014 March 25 – cited 2014 March 25. Available from: http:// www.laerdal.com/no/ResusciBaby. 8. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37:153–6. 9. Kramer-Johansen J, Edelson DP, Losert H, et al. Uniform reporting of measured quality of cardiopulmonary resuscitation (CPR). Resuscitation 2007;74:406–17. 10. Hemway RJ, Christman C, Perlman J. The 3:1 is superior to a 15:2 ratio in a newborn manikin model in terms of quality of chest compressions and number of ventilations. Arch Dis Child Fetal Neonatal Ed 2013;98:F42–5. 11. Solevag AL, Madland JM, Gjaerum E, Nakstad B. Minute ventilation at different compression to ventilation ratios, different ventilation rates, and continuous chest compressions with asynchronous ventilation in a newborn manikin. Scand J Trauma Resusc Emerg Med 2012;20:73. 12. Pierce EF, Eastman NW, McGowan RW, Legnola ML. Metabolic demands and perceived exertion during cardiopulmonary resuscitation. Percept Motor Skills 1992;74:323–8. 13. Ashton A, McCluskey A, Gwinnutt CL, Keenan AM. Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min. Resuscitation 2002;55:151–5.
6
A. M. Boldingh et al.
Downloaded by [University of Exeter] at 21:10 01 April 2016
14. Baubin M, Schirmer M, Nogler M, et al. Rescuer’s work capacity and duration of cardiopulmonary resuscitation. Resuscitation 1996; 33:135–9. 15. Hawley JA, Reilly T. Fatigue revisited. J Sports Sci 1997;15:245–6. 16. Marcora SM, Staiano W, Manning V. Mental fatigue impairs physical performance in humans. J Appl Physiol 2009;106: 857–64. 17. Teixeira PJ, Carraca EV, Markland D, et al. Exercise, physical activity, and self-determination theory: a systematic review. Int J Behav Nutr Phys Act 2012;9:78.
J Matern Fetal Neonatal Med, Early Online: 1–6
18. Wyckoff MH, Berg RA. Optimizing chest compressions during delivery-room resuscitation. Semin Fetal Neonatal Med 2008;13: 410–15. 19. Christman C, Hemway RJ, Wyckoff MH, Perlman JM. The twothumb is superior to the two-finger method for administering chest compressions in a manikin model of neonatal resuscitation. Arch Dis Childhood Fetal Neonat Ed 2011;96:F99–101. 20. Dorfsman ML, Menegazzi JJ, Wadas RJ, Auble TE. Two-thumb vs. two-finger chest compression in an infant model of prolonged cardiopulmonary resuscitation. Acad Emerg Med 2000;7:1077–82.
ISSN: 1476-7058 (Print) 1476-4954 (Online) Journal homepage: http://www.tandfonline.com/loi/ijmf20
Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation Anne Marthe Boldingh, Thomas Hagen Jensen, Ane Torvik Bjørbekk, Anne Lee Solevåg & Britt Nakstad To cite this article: Anne Marthe Boldingh, Thomas Hagen Jensen, Ane Torvik Bjørbekk, Anne Lee Solevåg & Britt Nakstad (2015): Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation, The Journal of Maternal-Fetal & Neonatal Medicine, DOI: 10.3109/14767058.2015.1119115 To link to this article: http://dx.doi.org/10.3109/14767058.2015.1119115
Accepted author version posted online: 13 Nov 2015. Published online: 15 Dec 2015. Submit your article to this journal
Article views: 50
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ijmf20 Download by: [University of Exeter]
Date: 01 April 2016, At: 21:10
http://informahealthcare.com/jmf ISSN: 1476-7058 (print), 1476-4954 (electronic) J Matern Fetal Neonatal Med, Early Online: 1–6 ! 2015 Taylor & Francis. DOI: 10.3109/14767058.2015.1119115
ORIGINAL ARTICLE
Rescuers’ physical fatigue with different chest compression to ventilation methods during simulated infant cardiopulmonary resuscitation Anne Marthe Boldingh1,2, Thomas Hagen Jensen1*, Ane Torvik Bjørbekk1*, Anne Lee Soleva˚g1, and Britt Nakstad1,2 Department of Pediatric and Adolescent Medicine, Akershus University Hospital, Lørenskog, Norway and 2Akershus Faculty Division, Institute of Clinical Medicine, University of Oslo, Lørenskog, Norway
Downloaded by [University of Exeter] at 21:10 01 April 2016
1
Abstract
Keywords
Objective: To assess development of objective, subjective and indirect measures of fatigue during simulated infant cardiopulmonary resuscitation (CPR) with two different methods. Methods: Using a neonatal manikin, 17 subject-pairs were randomized in a crossover design to provide 5-min CPR with a 3:1 chest compression (CC) to ventilation (C:V) ratio and continuous CCs at a rate of 120 min1 with asynchronous ventilations (CCaV-120). We measured participants’ changes in heart rate (HR) and mean arterial pressure (MAP); perceived level of fatigue on a validated Likert scale; and manikin CC measures. Results: CCaV-120 compared with a 3:1 C:V ratio resulted in a change during 5-min of CPR in HR 49 versus 40 bpm (p ¼ 0.01), and MAP 1.7 versus 2.8 mmHg (p ¼ 0.03); fatigue rated on a Likert scale 12.9 versus 11.4 (p ¼ 0.2); and a significant decay in CC depth after 90 s (p ¼ 0.03). Conclusions: The results indicate a trend toward more fatigue during simulated CPR in CCaV-120 compared to the recommended 3:1 C:V CPR. These results support current guidelines.
Manikin, neonatology, quality
Introduction Guidelines recommend using a 3:1 chest compression (CC) to ventilation (C:V) ratio for cardiopulmonary resuscitation (CPR) at birth. CCs should be delivered at a rate of 90 min1 synchronized with ventilations at a rate of 30 min1 to achieve a total of 120 events min1. However, the most effective method remains controversial [1]. There is limited evidence supporting one C:V ratio over another, but mathematical models suggest that higher CC rates than the currently recommended 90 min1 could optimize systemic perfusion [2]. In asphyxiated piglets, Schmo¨lzer et al. demonstrated that the time to return of spontaneous circulation (ROSC) was similar when using a 3:1 C:V ratio as compared to continuous CCs at a rate of 90 min1 with asynchronous ventilations (CCaV-90) [3]. In another study, using the same piglet model, better regional and systemic hemodynamics and shorter time to ROSC was achieved with uninterrupted CCs at a rate of 120 min1 when combined with sustained inflations [4]. Neonates may benefit from higher CC rates and possibly alternative C:V ratios, but the feasibility in terms of physical demands of performing uninterrupted CCs at higher CC rates remains to be determined. Li et al. investigated decay from
*Both contributed equally as second authors. Address for correspondence: Anne Marthe Boldingh, Department of Paediatric and Adolescent Medicine, Akershus University Hospital, P.O. Box 1000, N-1478 Lørenskog, Norway. Tel: +47 97006821. Fax: +47 67960900. E-mail: [email protected]
History Received 11 August 2015 Revised 8 November 2015 Accepted 9 November 2015 Published online 8 December 2015
baseline in peak CC pressure, used as a surrogate for fatigue, during a 10-min period of 3:1 C:V CPR, CCaV-90 and continuous CCs at a rate of 120 min1 with asynchronous ventilations (CCaV-120) [5]. They found a significant decay from baseline, occurring at 156, 96, and 72 s in 3:1, CCaV-90, and CCaV-120 groups. An adult-manikin study investigated performer fatigue comparing 30:2 and 15:2 C:V ratios and found similar objective physiologic measures, but a subjectively higher level of fatigue [6]. However, the two-thumb technique for neonatal CCs [1] may not be comparable with adult CPR, and thus objective and subjective measures of rescuers fatigue during neonatal CPR should be investigated. The primary aim of this study was to compare physiologic measures of rescuer fatigue during 5-min CPR sessions using the 3:1 C:V ratio and CCaV-120 in a population of healthcare workers with daily neonatal responsibilities. Furthermore, we sought to evaluate perceived fatigue and changes in CC quality as indirect measures of fatigue. We hypothesized that CCaV-120 compared to 3:1 C:V CPR would be more exhausting to perform resulting in a higher rescuer heart rate (HR) and mean arterial pressure (MAP) over time, greater perceived exhaustion, and a larger decay in CC depth over time.
Methods Settings and participants This randomized crossover manikin study was performed during a pre-defined 1-week period at Akershus University
2
A. M. Boldingh et al.
Hospital in February 2014. The institutional privacy legislation authority approved the study. Because the study did not involve patients, and was considered very low-risk for the participating health care workers, the Regional Ethics Committees for Medical Research did not consider its approval necessary. A convenience sample of 34 subjects was recruited from the Department of Pediatric and Adolescent Medicine and the Department of Obstetrics (doctors (n ¼ 7), nurses (n ¼ 16) and midwifes (n ¼ 11)) after written informed consent. Exclusion criteria were any medical condition contraindicating the exertion associated with CPR. For each participant we registered by questionnaire, the number of CPR episodes during the career, episodes of weekly physical activity and the last time they participated in a CPR course.
Downloaded by [University of Exeter] at 21:10 01 April 2016
Experimental protocol We used a Resusci Baby QCPR manikin [7] (Laerdal Medical, Stavanger, Norway), simulating a 6-kg infant, with a non-progressive spring, needing a weight application of 6 kg (13 lb) to achieve a CC depth of 36 mm, equaling 1/3 of the anterior–posterior diameter of the manikin’s chest. Maximum CC depth was 40 mm. A 240 ml self-inflating bag with a facemask size 0/1 was used (Laerdal Medical, Stavanger, Norway), pressure relief valve at 35 cmH2O, no gas flow or peak end expiratory pressure valve. Subject-pairs provided 5-min CPR, randomized (http:// www.randomizer.org) to start with either a 3:1 C:V ratio (with a pause after every third CC to deliver one inflation) or CCaV-120 (uninterrupted CCs at a rate of 120 min1 with asynchronous ventilations at a rate of 40–60 min1), and to start with performing either ventilation or CCs. For each CC method, both subjects in each pair performed CCs once and assisted ventilations once; i.e. every subject performed in total four 5-min CPR sessions, separated by a rest of minimum 1-h between the first and the second CC method. Before the experiments each subject made him/herself comfortable with the equipment used. A standardized instruction was given before start: CCs by the two-thumb encircling hands method centered over the lower third of the sternum and a CC depth of 1/3 the anterior–posterior diameter of the chest [1]. CCs and ventilations should be given at a rate to achieve 120 events min1 and attention should be given to adequate inflation of the lungs [1]. During the sessions, metronome guidance at a rate of 120 min1 and verbal motivation and feedback on techniques were given. Immediately after completing CPR, participants assessed their level of perceived fatigue on a Likert scale. Data collection We collected participant demographic and baseline characteristics including age, gender, body mass index (BMI), HR (beats per minute, bpm), MAP (mmHg) and respiratory rate. Maximum HR was calculated by the formula (208–0.7 age), accuracy ± 20 bpm [8]. Baseline HR, respiratory rate and MAP were measured before initiation of CPR, using a Nihon Kohden BSM-2301K bedside monitor (Nihon Kohden Corporation, Tokyo, Japan) and Kendall hydrogel ECG electrodes (Covidien, Minneapolis, MN).
J Matern Fetal Neonatal Med, Early Online: 1–6
We evaluated objective fatigue by changes in HR, MAP and respiratory rate. The participants’ perceived level of fatigue after each CPR session was measured using the validated Likert scale (range 6–11: very, very light to fairly light, 12–15: somewhat hard to hard and 16–20: very hard to very, very hard). The seemingly odd range of 6–20 was chosen for comparison to the general HR of a healthy adult by multiplying by 10. After having performed all CPR sessions the participants completed a brief survey about how many more minutes they thought they would be able to perform CPR using each method; and which method they preferred. CPR quality measures were recorded using equipment from Laerdal Medical (Stavanger, Norway). The manikin was connected to a computer digitizing ventilation and CC values with Protocol Emulator recording program. The variables were displayed in BLS Emulator Viewer, version 1.0.5. A linear optical recorder measured CC rate and depth (depth ± 2 mm). CC measures were: the number of delivered CCs, CC rate, absolute and relative depth (mm), leaning (mm) and the proportion of CCs with a depth 1/3 the anterior– posterior diameter of the chest, i.e. 36 mm. Absolute depth was defined as the distance from a turning point of maximum force to baseline-at-start; relative depth as the distance from a turning point of maximum force to a turning point of minimum force. The depth of this latter turning point is a composite of incomplete chest wall recoil, i.e. leaning, thus absolute depth ¼ relative depth + leaning [9]. In all sessions we asked the participant to start with the thumbs above the manikin’s chest to ensure a baseline measure of 0 mm. Statistics Based on pilot data we calculated that 19 subjects were required to have a 80% chance of detecting, as significant at the 5% level, a HR difference from 1-min to 5-min of 29 in the 3:1 ratio compared to 43 during CCaV-120. As this was a small number, we decided to do a convenient sampling due to no ethical limitations. Pilot data are not included in the final analyses. Data are presented as means with 95% confidence interval (CI) and frequencies with percentages. We analyzed changes over time in the dependent variables HR, respiratory rate, the number of CCs performed and CC rate, each consecutive 1-min segment; CC depth and leaning for each consecutive 15-s segment, and MAP as a pre- and post-test measurement. Baseline was defined as the measured HR at start, and baseline for CC depth as the average depth generated in the first 15 s of CCs. Decay in CC depth was defined as a statistical significant decay from the respective baseline. Participant HR, MAP and respiratory rate for each ratio-group before each CPR session were compared using a paired t-test with 95% CI. The number of delivered CCs per minute was compared to the methods respective target; 90 CCs per minute in 3:1 C:V ratio and 120 CCs per minute in CCaV-120, using a one-sample Student’s t-test. A random intercept model, random for individuals, was estimated to assess the trend in HR from baseline to the end of the session. The fixed independent variables were time as a categorical variable, a dummy distinguishing between the ratio-groups, sequence-of-period to control for possible
Fatigue in infant CPR
DOI: 10.3109/14767058.2015.1119115
Downloaded by [University of Exeter] at 21:10 01 April 2016
fatigue/carry-over effects, and an interaction-term between time and ratio-group. Weekly physical activity and BMI were excluded from the model, as they did not change the estimates. As a secondary analysis, joint-test and pairwise comparisons between each 1-min segment and baseline were performed with the estimated contrast from the model. Similarly, secondary outcomes were fitted using the same model building and contrast testing. For analysis of outcome variables with 15-s segments, time and where necessary a quadratic term for time (time2), were included as continuous variables. An interaction-term between time2 and ratio-group was considered and included if significant. If the global timeeffect was significant, pairwise comparisons between ratiogroups at each time-point were performed with the estimated contrast. A p value50.05 was considered significant. All analyses were calculated with Stata software, version 13.1 (StataCorp, Lakeway, TX).
Results We enrolled 34 subjects, mean (95% CI) age was 40.6 (36.8; 44.3) years, 31 (91.2%) of the subjects were female; and 23 (64.6%) had completed a CPR training course within the last three months, 7 (20.6%) within the last 12 months and 4 (11.8%) had never completed a CPR course. The number of CPR episodes with CCs plus assisted ventilations that the subjects had participated in during their career was: no episodes 19 (55.9%); 1–5 episodes 11 (32.3%); 5–10 episodes 3 (8.8%); and more than 10 episodes 1 (2.9%). Subjects’ weekly physical activity was: zero 6 (17.6%), 1–3 times 26 (76.5%) and 4–6 times 2 (5.9%).
3
Average subjective exhaustion was ‘‘somewhat hard’’ for 3:1 C:V CPR and ‘‘hard’’ for CCaV-120 on the Likert scale, p50.001. When using the 3:1 C:V ratio, 30 (88.2%) subjects estimated being able to continue CPR for at least two more minutes, compared to only 19 (56%) when using CCaV-120. Thirty (80%) of the participants preferred the 3:1 CPR method. CPR quality We excluded three CC recordings for each of the 3:1 C:V ratio and CCaV-120 due to technical problems. There were significant differences between CCs in CCaV-120 versus 3:1 C:V CPR (Table 2). The proportion of CCs with adequate depth (36 mm) was 90.5% for 3:1 C:V ratio and 60.1% in CCaV-120. There was a difference between CC groups for absolute depth (p50.001), relative depth (p ¼ 0.016) and leaning (p ¼ 0.039). The difference in absolute and relative depth between 3:1 C:V CPR and CCaV-120 increased from the first 15 s to the last 15 s: from 2.4 to 3.3 mm for absolute depth, and from 0.9 to 2.5 mm for relative depth (Figure 2). Compared with baseline, absolute depth in CCaV120 decreased significantly 90 s after commencement of CCs (p ¼ 0.03). Absolute CC depth was reduced by 3% (1.2 mm) after three minutes, and by 7.8% (3.1 mm) after five minutes. Analyses adjusting for the amount of weekly physical activity; Likert score; and BMI confirmed the original findings.
Objective and subjective rescuer fatigue All the included participants completed all four 5-min CPR sessions. There were no significant differences between CC methods in baseline HR, MAP and respiratory rate. One outlier-measure of HR was excluded from statistics. Calculated BMI and maximum HR (SD) were 23.9 (3.4) kg/m2 and 180 (8) bpm, respectively. At the end of the session, 3:1 C:V CPR resulted in 60% and CCaV-120 65% of calculated maximum HR, p ¼ 0.03. The average of the participants’ objective and subjective measures of fatigue are presented in Table 1. HR from baseline until 5-min, increased with 40 and 49 bpm for 3:1 C:V CPR and CCaV-120, respectively (Figure 1). Analyses adjusting for the amount of physical activity and BMI confirmed the original findings.
Figure 1. Average for each 1-min segment (raw data). Random intercept model (random: id), controlled for sequence of period. Significant difference between 3:1 and CCaV-120 at 5th minute, p¼0.029. There was a significant change from baseline for both groups when comparing each 1-min sequence with baseline. CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations, HR: heart rate.
Table 1. Average measures of participants’ physiological measures and subjective perception of fatigue (Likert-scale rating) in chest compression to ventilation ratio 3:1 and CCaV-120. Variable Max HR (bpm) DHR DMAP (mmHg) DRF Likert-score compressions
3:1 118 39 2.8 15 12.6
(109; 126) (33; 46) (6.5; 0.8) (12; 18) (11.6; 13.5)
CCaV-120 122 49 1.7 14 14.9
(114; 131) (43; 55) (1.9; 5.3) (11; 16) (14.0; 15.8)
p value
ICC
0.05 0.005 0.013 0.273 50.001
0.85 0.58 0.43 0.3 0.72
Values are mean (95% confidence interval). Random intercept model (random effect: subject id), controlled for sequence of period. Baseline group 3:1 ratio. D ¼ variable end minus variable start. CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations; HR: heart rate; ICC: intra cluster correlation coefficient; RF: respiratory frequency.
4
A. M. Boldingh et al.
J Matern Fetal Neonatal Med, Early Online: 1–6
Discussion In this study, we used an infant manikin to study rescuer fatigue during simulated CPR. In a population of healthcare workers with daily neonatal responsibilities, CCaV-120 resulted in a greater increase in rescuer HR and MAP and perceived fatigue, compared to the recommended 3:1 C:V ratio. In CCaV-120 CC depth decreased significantly during Table 2. Chest compression parameters in chest compression to ventilation ratio 3:1 and CCaV-120. Explanatory variable
Downloaded by [University of Exeter] at 21:10 01 April 2016
Number of CC/min CC rate CC depth (absolute) (mm) CC depths (relative) (mm) Leaning (mm) Adequate depth (41/3 AP diameter) (%)
3:1 89 129 40.2 37.6 2.6 89.9
(87; 91) (127; 131) (39.5; 40.9) (36.5; 38.7) (1.8; 3.3) (81.8; 97.9)
CCaV-120 113 125 38.3 34.5 3.8 58.0
(106; 120) (123; 126)** (36.9; 39.6)** (33.1; 35.8)** (3.0; 4.6)* (44.9; 71.1)**
Values are mean (95% confidence interval). The number of CC/min was compared to the respective target in each C:V group; 90 CC/min in 3:1 and 120 CC/min in CCaV-120. Random intercept model (random effect: subject id), controlled for sequence of period, baseline group 3:1 ratio. AP: anterior posterior; CC: chest compression; CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations. *Significant at p5(0).05. **Significant at p50.001.
the 5-min CPR session and more CCs with inadequate depth were delivered compared to the 3:1 C:V ratio. These findings indicate that CCaV-120 is more exhausting than 3:1 C:V CPR. This is the first study to measure resuscitators’ physiological responses while performing CPR with different CC methods in an infant manikin. Previous infant manikin studies have investigated different C:V ratios with respect to CC and ventilation parameters [5,10,11]. One of these investigated fatigue, using the amount of pressure in a saline-bag inside the manikin’s chest as a fatigue surrogate. During a 10-min session, the peak pressure decreased more in CCaV-120 and CCaV-90 than in 3:1 C:V CPR [5]. In the current study, CCaV-120 compared with a 3:1 C:V ratio, resulted in a HR closer to an estimated age-adjusted maximum and a significantly greater change in HR and MAP. Although the measured changes were small, our combined results indicate that CCaV-120 is more exhausting than a 3:1 C:V ratio. A possible explanation may be the brief pauses in CCs in 3:1 C:V CPR. Also, the degree of physical fitness may impact physiological differences and some studies have suggested that a smaller stature and limited physical fitness can adversely affect CPR performance [12–14]. We did not test the physical fitness of the participants, but adjusting for weekly physical activity and BMI did not significantly change our conclusions. Furthermore, the subjects operated as their own controls in a crossover study design. However, as the
Figure 2. Average mean for each 15-s segment (raw data). Random intercept models (random: id), controlled for sequence of period, baseline group: 3:1 ratio; post-estimation pairwise contrast testing for differences between groups from baseline. Absolute depth: Difference between groups over time, p50.001, difference between groups from baseline, p50.001 at all time points. Relative depth: Difference between groups over time, p ¼ 0.016, difference between groups from baseline, p50.001 at all time points. Leaning: Difference between groups over time, p ¼ 0.039, difference between groups from baseline, 15–270 s: p50.001; 275–300 s: p ¼ 0.012. C: chest compression; CCaV-120: continuous chest compressions at a rate of 120 min1 with asynchronous ventilations, HR: heart rate.
Fatigue in infant CPR
Downloaded by [University of Exeter] at 21:10 01 April 2016
DOI: 10.3109/14767058.2015.1119115
majority of our participants were female, with potentially smaller stature than their male counterparts, we do not know if the fatiguing effect of the two CC methods would have been the same had we included more male participants. But as the gender distribution in our study closely reflects the gender distribution at the ward, we believe our results are generalizable to clinical practice. Fatigue can have physical or mental causes. Physical fatigue is the transient inability of a muscle to maintain optimal physical performance and is made more severe by intense physical exercise [15]. Mental fatigue is a temporary inability to maintain optimal cognitive performance and has also been shown to decrease physical performance [16]. A person’s intrinsic motivation is important for optimizing physical performance [17]. We aimed to explore physical fatigue and thus we motivated the participants with verbal feedback during the sessions to optimize performance. We argue that the physiological difference we observed is a consequence of physical, not mental fatigue. Rating of perceived fatigue was higher in CCaV-120 compared to the 3:1 C:V ratio. This finding is supported by the differences in the physiologic measures of fatigue, the smaller proportion of adequate CCs, and more leaning in CCaV-120 compared to the 3:1 C:V ratio. By self-assessment more subjects estimated being able to continue CPR for at least two additional minutes when using the 3:1 C:V ratio compared to CCaV-120. These results are in agreement with other studies [5,10]. Rescuer fatigue can affect CC depth [6] and thus the coronary perfusion pressure [18]. We demonstrated that CCaV-120 resulted in a significant decline in CC depth 90 s after commencement of CCs and a 7.8% reduction in CC depth after 5 min. Li et al. [5] found a reduction in peak pressure in CCaV-120 of 50% using the same size manikin, but different setup, which may explain the difference in effect size. In agreement with Li et al. [5], if using CCaV-120, we recommend CC operator to switch every 90 s to avoid suboptimal CPR quality. Importantly, this should not compromise CC quality by increasing interruptions in CC and hands-off-time. Until now, no studies have compared different techniques in manikins to real-life situations [5,10,19,20], which makes it difficult to extrapolate the results to real-life situations. This represents a limitation to our study, however, the objective physiologic measures strengthen the indirect CC findings of fatigue measured in the manikin. The CPR duration in our experiments was five minutes although current resuscitation guidelines advise to continue CPR if HR remains undetectable for up to 10 min [1]. The rationale for conducting 5-min trials was twofold: A pilot study showed fatigue already after two minutes, and in real-life it is not common for the same rescuer to perform CCs for 10 min or more. The rest time between CC methods could potentially have been longer. However, the baseline measurements of HR and MAP were similar and none of the subjects reported to be fatigued when starting their second CC session. Finally, we enrolled subjects with limited CPR experience and who had not participated in a CPR course the last 12 months. This might have affected the results. However, all subjects were given a standardized briefing and they were given time before the session to
5
practice CPR techniques and make themself comfortable with the equipment used. In conclusion, this study indicates that performing CCs is more exhausting with CCaV-120 than a 3:1 C:V ratio as measured by a higher rescuer HR and MAP, greater perceived fatigue and decay in CC depth.
Acknowledgements We wish to thank Helge Myklebust, Øystein Gomo and Mette Stavland, Laerdal Medical for technical support, the participating neonatal healthcare professionals who contributed to this study and Jonas Christoffer Lindstrøm, HØKH, Akershus University Hospital, Norway, for statistical guidance.
Declaration of interest A.M.B. has received financial support from the Laerdal Foundation for Acute Medicine. Laerdal Medical (Stavanger, Norway) provided the manikin for the study. The other authors report no declarations of interest.
References 1. Kattwinkel J, Perlman JM, Aziz K, et al. Part 15: neonatal resuscitation: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S909–19. 2. Babbs CF, Meyer A, Nadkarni V. Neonatal CPR: room at the top – a mathematical study of optimal chest compression frequency versus body size. Resuscitation 2009;80:1280–4. 3. Schmolzer GM, O’Reilly M, Labossiere J, et al. 31 Compression to ventilation ratio versus continuous chest compression with asynchronous ventilation in a porcine model of neonatal resuscitation. Resuscitation 2014;85:270–5. 4. Schmolzer GM, O’Reilly M, Labossiere J, et al. Cardiopulmonary resuscitation with chest compressions during sustained inflations: a new technique of neonatal resuscitation that improves recovery and survival in a neonatal porcine model. Circulation 2013;128: 2495–503. 5. Li ES, Cheung PY, O’Reilly M, et al. Rescuer fatigue during simulated neonatal cardiopulmonary resuscitation. J Perinatol 2015; 35:142–5. 6. Vaillancourt C, Midzic I, Taljaard M, Chisamore B. Performer fatigue and CPR quality comparing 30:2 to 15:2 compression to ventilation ratios in older bystanders: a randomized crossover trial. Resuscitation 2011;82:51–6. 7. Laerdal Medical AS. ResusciÕ Baby with QCPR. Laerdal Medical AS; 2014 March 25 – cited 2014 March 25. Available from: http:// www.laerdal.com/no/ResusciBaby. 8. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37:153–6. 9. Kramer-Johansen J, Edelson DP, Losert H, et al. Uniform reporting of measured quality of cardiopulmonary resuscitation (CPR). Resuscitation 2007;74:406–17. 10. Hemway RJ, Christman C, Perlman J. The 3:1 is superior to a 15:2 ratio in a newborn manikin model in terms of quality of chest compressions and number of ventilations. Arch Dis Child Fetal Neonatal Ed 2013;98:F42–5. 11. Solevag AL, Madland JM, Gjaerum E, Nakstad B. Minute ventilation at different compression to ventilation ratios, different ventilation rates, and continuous chest compressions with asynchronous ventilation in a newborn manikin. Scand J Trauma Resusc Emerg Med 2012;20:73. 12. Pierce EF, Eastman NW, McGowan RW, Legnola ML. Metabolic demands and perceived exertion during cardiopulmonary resuscitation. Percept Motor Skills 1992;74:323–8. 13. Ashton A, McCluskey A, Gwinnutt CL, Keenan AM. Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min. Resuscitation 2002;55:151–5.
6
A. M. Boldingh et al.
Downloaded by [University of Exeter] at 21:10 01 April 2016
14. Baubin M, Schirmer M, Nogler M, et al. Rescuer’s work capacity and duration of cardiopulmonary resuscitation. Resuscitation 1996; 33:135–9. 15. Hawley JA, Reilly T. Fatigue revisited. J Sports Sci 1997;15:245–6. 16. Marcora SM, Staiano W, Manning V. Mental fatigue impairs physical performance in humans. J Appl Physiol 2009;106: 857–64. 17. Teixeira PJ, Carraca EV, Markland D, et al. Exercise, physical activity, and self-determination theory: a systematic review. Int J Behav Nutr Phys Act 2012;9:78.
J Matern Fetal Neonatal Med, Early Online: 1–6
18. Wyckoff MH, Berg RA. Optimizing chest compressions during delivery-room resuscitation. Semin Fetal Neonatal Med 2008;13: 410–15. 19. Christman C, Hemway RJ, Wyckoff MH, Perlman JM. The twothumb is superior to the two-finger method for administering chest compressions in a manikin model of neonatal resuscitation. Arch Dis Childhood Fetal Neonat Ed 2011;96:F99–101. 20. Dorfsman ML, Menegazzi JJ, Wadas RJ, Auble TE. Two-thumb vs. two-finger chest compression in an infant model of prolonged cardiopulmonary resuscitation. Acad Emerg Med 2000;7:1077–82.
