Author: Ho, Sau Tat
Title: Effect of rescuer's body position and cardiorespiratory fitness on the performance of simulated external chest compression
Degree: DHSc
Year: 2014
Subject: First aid in illness and injury.
Medical emergencies.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Health and Social Sciences
Pages: xix, 112 leaves : color illustrations ; 30 cm
Language: English
Abstract: Background: External chest compression (ECC) is a process that assists in slowing the rate of reduction of myocardial adenosine triphosphate (ATP) during cardiac arrests until the medical team arrives, it is thus a crucial component of cardiopulmonary resuscitation (CPR). Rescuers who provide high quality and effective external chest compression significantly improve the outcome of CPR. Previous studies have shown that the effectiveness of ECC varies between male and female rescuers during ECC and the outcome also varied with ECC delivery positions; the impact of cardiorespiratory fitness of rescuers on the performance of ECC rescuers remains undetermined. Objectives: The primary aim of this project is to determine the time duration that male and female rescuers can perform simulated external chest compression (ECC) to a recommended depth and rate of compressions in accordance to American Heart Association (AHA) Guidelines 2005, performed by a group of local healthcare professionals in bed-mount kneeling and standing positions. Secondly, this project intends to determine the relationship between compression rate and depth, and oxygen consumption by rescuers during simulated ECC in both bed-mount kneeling and standing positions. Lastly, this project intends to address the relationship between cardiorespiratory fitness level of rescuers and the quality of ECC performed by male and female healthcare professionals, and to compare if performance is affected by the gender of the rescuers. Methods: A prospective and exploratory study design was adopted. Nurses of both genders with clinical CPR experience and regular refresher training were invited to participate in the study. Each subject attended the laboratory three times, each visit a week apart. During the first two visits, each subject was asked to perform simulated external chest compressions on an adult manikin torso (Skillreporter ResusciAnne(R)) for 5 minutes in either bed-mount kneeling or standing position. If bed-mount kneeling position was used at the first visit, simulated ECC would be delivered in standing position at the second visit, and vice versa. The order of the rescuer's position was randomized. On the third visit to the laboratory, the subject's cardiorespiratory fitness level (predicted peak oxygen consumption VO2max) was assessed using the Chester step test method. The rate and depth of chest wall compressions were measured by a SkillReporter ResusciAnne(R) and the compression force was measured by a force platform. Signals from the SkillReporter and the force platform were fed into the ADInstruments PowerLab(R) Systems for data collection and analysis. Oxygen consumption and heart rate during the ECC performance were recorded by a portable metabolic cart (the Fitmate Pro System). The subjective level of exertion (Rate of Perceived Exertion, RPE) during the ECC performance was evaluated by the Borg Scale. The subjective level of discomfort during the ECC was assessed by a 10-cm Visual Analog Scale (VAS). Data recorded during the 5-minute performance was analyzed using repeated measures of ANOVA with Bonferroni adjustment. Data between male and female subjects were compared using independent t-tests. Pearson correlation analysis and linear regression were performed to determine the relationship between various key elements during ECC and cardiorespiratory fitness of subjects in this study. Results: The study was conducted over the calendar years, 2010 to 2012. Forty nurses (20 male and 20 female) completed the study. The mean compression rate for all 40 subjects during the 5-minute ECC in bed-mount kneeling and standing positions were 119 (11) /min [mean (SD)] and 116 (15) /min respectively, meeting the international recommended rate (about 100 /min) (AHA 2005) for effective ECC. However, the mean compression depth for all 40 subjects during the 5-minute ECC in bed-mount kneeling and standing positions were 38.1 (6.5) mm and 34.2 (7.7) mm respectively, which fell far short of the international recommended depth (about 38 - 51 mm) (AHA, 2005) for effective ECC. When data for all subjects were included for analysis, the mean time for which the required depth of 38 mm was maintained was 2.5 min in the bed-mount kneeling position but only 1 min in standing. Sub-analysis showed that male subjects were able to maintain the required depth for 5 min in bed-mount kneeling and 3 min in standing; however, female subjects were only able to maintain the required depth for 1 min 15 sec in bed-mount kneeling but failed to reach the required compression depth at all in the standing position. Over the 5 min recording time, the results illustrated a significant reduction of 5.4% and 26.9% in compression depth after the 1st minute and 5th minute of ECC delivered in the bed-mount kneeling position. In the standing position, the decline was 5.6% and 27% after the 1st and 5th minute respectively. Furthermore, the depth of compression delivered by male subjects was significantly deeper than that delivered by the female subjects in both positions (p < 0.05).
The mean compression force reported during the 5-minute ECC in bed-mount kneeling and standing positions were 155 (25) N and 144 (26) N respectively, which were much less than that reported in previous studies. Moreover, the compression force delivered by male subjects appeared to be significantly higher than that delivered by female subjects in both positions. Lastly, correlation analysis showed that there was a positive and significant correlation between cardiorespiratory fitness and the mean compression depth in both bed-mount kneeling and standing positions (r = 0.60 and 0.62 respectively, p < 0.05); and between cardiorespiratory fitness and mean compression force in the bed-mount kneeling (r = 0.62, p < 0.05); however the correlation between fitness and compression force was only weak though significant in the standing position (r= 0.38, p< 0.05). Conclusion: This study showed that the quality of simulated ECC provided by rescuers commenced to decline at one minute into the procedure, and the decline was faster and more significant when ECC was delivered in the standing position compared to a bed-mount kneeling position; suggesting a bed-mount kneeling position should be adopted whenever possible during an in-hospital CPR procedure. Findings from this study also suggest that, to align with the international standard required, the local nurses should adopt a protocol that the ECC procedure be alternated between male rescuers every 2 minutes but every 1 minute for female rescuers, and if possible in a bed-mount kneeling rather than a standing position. This study confirms that the quality of compression is directly related to the cardiorespiratory fitness of the rescuer. Linear regression analysis of the data suggests that the minimum predicted maximal oxygen consumption required to deliver a required standard compression depth of 38 mm is 38 ml/kg/min. These data suggest that regular physical training protocols perhaps should be incorporated into CPR maintenance training, especially for female healthcare professionals, to ensure adequate ECC during a CPR procedure.
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