Measuring the Effect of Off-Balancing Vectors on the Delivery of High-Quality CPR during Ambulance Transport: A Proof of Concept Study

Abstract

Aim

This study aims to demonstrate the feasibility of quantifying the off-balancing vectors experienced during ambulance transport and comparing them to high-quality cardiopulmonary resuscitation (HQ-CPR) metrics.

Methods

Ten participants completed a total of 20 evolutions of compression-only HQ-CPR in an ambulance driven in a manner that minimized or increased linear and angular off-balancing vectors. Linear and angular velocity, linear and angular acceleration, and linear jerk were recorded. HQ-CPR variables measured were compression fraction and proportion of compressions with depth >5 cm (depth%), rate 100–120 (rate%), full chest recoil (recoil%), and hand position (hand%). A composite score was calculated: [(depth% + rate% + recoil% + hand%)/4) * compression fraction]. Difficulty of HQ-CPR performance was measured with the Borg rating of perceived exertion (RPE) Scale. A series of mixed effects models were fitted regressing each HQ-CPR metric on each off-balancing vector.

Results

HQ-CPR data and vector quantity data were successfully recorded in all evolutions. Rate% was negatively associated with increasing linear velocity (slope = −3.82, standard error [SE] 1.12, p = 0.005), linear acceleration (slope = −5.52, SE 1.93, p = 0.013), linear jerk (slope = −17.60, SE 5.78, p = 0.007), angular velocity (slope = −75.74, SE 22.72, p = 0.004), and angular acceleration (slope = −152.53, SE 59.60, p = 0.022). Compression fraction was negatively associated with increasing linear velocity (slope = −1.35, SE 0.37, p = 0.004), linear acceleration (slope = −1.67, SE 0.48, p = 0.003), linear jerk (slope = −4.90, SE 1.86, p = 0.018), angular velocity (slope = −25.66, SE 6.49, p = 0.001), and angular acceleration (slope = −45.35, SE 18.91, p = 0.031). Recoil% was negatively associated with increasing linear velocity (slope = −5.80, SE 2.21, p = 0.023) and angular velocity (slope = −116.96, SE 44.24, p = 0.019)). Composite score was negatively associated with increasing linear velocity (slope = −4.49, SE 1.45, p = 0.009) and angular velocity (slope = −86.13, SE 31.24, p = 0.014) and approached a negative association with increasing magnitudes of linear acceleration (slope −5.54, SE 2.93, p = 0.075), linear jerk (slope = −17.43, SE 8.80, p = 0.064), and angular acceleration (slope = −170.43, SE 80.73, p = 0.051). Borg RPE scale was positively associated with all off-balancing vectors. Depth%, hand%, mean compression depth, and mean compression rate were not correlated with any off-balancing vector.

Conclusion

Off-balancing vector data can be successfully quantified during ambulance transport and compared with HQ-CPR performance parameters. Increasing off-balancing vectors experienced during ambulance transport are associated with worse HQ-CPR metrics and increased perceived physical exertion. These data may help guide future drive styles, ambulance design, or use of mechanical CPR devices to improve HQ-CPR delivery during selected patient transport scenarios.

Acknowledgments

The authors thank Luis Martinez for facilitating the use of a Resusci-Anne QCPR Manikin and associated software, Jared Gunter and American Medical Response for their support, and Dr. Daniel Tancredi for his input on statistical analysis.

Disclosure Statement

The authors have no potential conflicts of interest to report.