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Signa Vitae

Journal of Intensive Care and Emergency Medicine

Influence of rescuer strength and shift cycle time on chest compression quality


Introduction. Previous studies have suggested that differences in rescuer strength and compression shift cycle are strongly associated with the quality of chest compression. We hypothesised that changing the shift cycle from two minutes to one would have a positive effect on the quality of chest compression in two-rescuer cardiopulmonary resuscitation (CPR), regardless of rescuer strength.

Methods.Thirty-nine senior medical students participated in this prospective, simulation-based, crossover study. After evaluation of muscle strength using a handgrip dynamometer, each participant was required to perform two sets of compressions separated by a 15-minute rest. Participants started with either four cycles of chest compressions for one minute followed by a one-minute rest (1-MCS), or with two cycles of chest compressions for two minutes followed by a two-minute rest (2-MCS). After a 15-minute break, participants switched groups and performed the other set of compressions. Mean compression depth (MCD), mean adequate compression (MAC), and adequate compression ratio (ACR) per minute were measured for each group. Subjective fatigue was reported after the completion of each set of compression cycles. Results. Rescuer strength was strongly correlated with MCD (p <0.01), MAC ratio (p <0.01), and ACR (p <0.01), and cycle group was correlated with MCD (p <0.01) and ACR (p =0.03). Subjective fatigue with 1-MCS was lower than with 2-MCS, regardless of rescuer strength.

Conclusion. We found that the quality of chest compressions could be improved by changing the shift cycle from two minutes to one, regardless of rescuer strength. Therefore, reducing the existing shift cycle recommended in guidelines for two rescuers could be beneficial.

Key words: CPR, fatigue, hand strength

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The effect of posture modification during continuous one-handed chest compression: A pilot study using in-hospital pediatric cardiac arrest simulation


Background. We modified the posture of the one-handed chest compression (MOHCC) as follows: first, the axis of the rescuer’s compression hand was adjusted to the lower half of the patient’s sternum; second, the opposite hand was wrapped around the elbow joint of the rescuer’s compression arm. This study evaluated the effect of the MOHCC on the mean chest compression depth (MCD) over time.

Methods. Thirty medical doctors conducted 2 min of continuous MOHCC without ventilation using the in-hospital pediatric arrest model (70-cm-high bed, 25-cm-high stepstool, a pediatric manikin and a cardiopulmonary resuscitation (CPR) meter). The MCD and mean chest compression rate (MCR) were measured at 30 s intervals using the Q-CPR review software.

Results. The MCD changed significantly over time (0–30 s, 41.9–44.7 mm; 30–60 s, 40.4–43.6 mm; 60–90 s, 39.2–42.8 mm; 90–120 s, 38.6–42.3 mm; [95% CI], P=0.002). However, it did not decrease significantly between 60–90 s and 90–120 s (P=0.173). The total decrease in MCD was 2.9 mm over a 2 min period. The MCR did not change significantly over time (0–30 s, 108.6–118.9 /min; 30–60 s, 107.9–119.1 /min; 60–90 s, 107.7–119.3 /min; 90–120 s, 107.4–119.0 /min; P=0.800).

Conclusions. Although the MCD changed significantly over a 2 min period, it did not decrease significantly after 90 s during performance of MOHCC. The MOHCC might be considered when the one-handed chest compression (OHCC) is selected as a chest compression method for cardiac arrest in small children.

Key words: cardiopulmonary resuscitation, cardiac arrest, child, fatigue

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The impact of changing work schedules on American firefighters’ sleep patterns and well-being


Across the nation, fire departments are adopting the 48/96 work schedule, in which firefighters work 48 consecutive hours with the following 96 hours off. Our study objective was to explain and quantify the impact of switching from the Kelly schedule to the 48/96 schedule by measuring changes in sleep, feelings of daytime function, as well as perceptions of professional and personal well-being for American firefighters. Sleep diaries and self-reported surveys were administered to firefighters at an urban fire department. Sleep diaries measuring the number of hours slept and feelings of refreshment were compared one month before and four months after implementation of the 48/96 schedule. The self-reported surveys measured sleepiness levels via the Epworth Sleepiness Scale. Secondary study objectives included changes in professional and personal well-being time for personal schedules, satisfaction, and health habits before and after the 48/96 schedule was implemented. The 59 firefighters included in the study reported an increase in sleep on-shift after the new schedule implementation (5.8 to 6.6 hours/night, p < 0.001). Participants also reported increased feelings of refreshment on days off (p < 0.001) and decreased daytime sleepiness (p < 0.001). We also found a general trend of improved perceptions of satisfaction, less shift interference with personal schedules and decreased feelings of burnout. American firefighters appeared to benefit from a 48/96 schedule, with short-term improvements in sleep patterns, feelings of burnout, and time for personal schedules.

Key words: firefighters, shift-work sleep disorder, emergency medical technicians, workplace, sleep, fatigue, burnout, professional, organizational culture

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