Previously submitted to: JMIR mHealth and uHealth (no longer under consideration since Jul 06, 2021)
Date Submitted: Apr 2, 2021
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
A Novel Cardiac Force Index Measured by Digital Devices and Applied to the G Tolerance Test among Military Aircrew: An Observational Study
ABSTRACT
Background:
Military aircrew are occupationally exposed to a high-G environment. G force causes blood to flow to the lower body region and challenges their cardiac function and anti-G straining maneuver effectiveness. A tolerance test is necessary for every military aircrew member before undergoing flight training. A novel cardiac force index (CFI) has been developed and used to assess long-distance running by mobile health (mHealth) technology. There is still no study to monitor the CFI by wearable devices during the G tolerance test.
Objective:
We added the cardiac function parameter CFI to the G tolerance test and elucidated the relationship between cardiac function and G tolerance among military aircrew.
Methods:
A noninvasive device, BioHarness 3.0, was used to measure heart rate (HR) and activity while resting and walking on the ground. The mathematical formula for cardiac function calculation is CFI = weight × activity/HR. The cardiac force ratio (CFR) is calculated by walking CFI (WCFI)/resting CFI (RCFI). G tolerance includes relaxed G tolerance (RGT) and straining G tolerance (SGT) tested by a human centrifuge under the gradual-onset-rate profile.
Results:
In total, 92 male participants voluntarily completed this study. The average values of RCFI, WCFI, and CFR were 0.02 [SD 0.04], 0.15 [SD 0.04], and 10.77 [SD 4.11], respectively. The mean RGT and SGT were 5.1G [SD 0.9] and 7.8G [SD 1.1], respectively, in the centrifuge. The percentages of participants with RGT greater than 5G or SGT greater than 8G were equally noted as 54.3%. Each 100-unit increase in WCFI increased RGT by 0.14G [SE 0.02, 95% CI 0.09 to 0.19] and by 0.17G [SE 0.03, 95% CI 0.11 to 0.22], corresponding to SGT. In addition, there was an increased chance of RGT values higher than 5G and SGT values higher than 8G according to the increase in WCFI.
Conclusions:
Our results suggested that WCFI is positively correlated with G tolerance in the centrifuge and has the potential to be used for military aircrew selection.
Citation
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