Suspension Tolerance in a Full-Body Safety Harness, and a Prototype Harness Accessory

Abstract

Workers wearing full-body safety harnesses are at risk for suspension trauma if they are not rescued in 5 to 30 min after a successfully arrested fall. Suspension trauma, which may be fatal, occurs when a person's legs are immobile in a vertical posture, leading to the pooling of blood in the legs, pelvis, and abdomen, and the reduction of return blood flow to the heart and brain. To measure suspension tolerance time, 22 men and 18 women with construction experience were suspended from the chest D-ring (CHEST) and back D-ring (BACK) of full-body, fall-arrest harnesses. Fifteen men and 13 women from the original group of subjects were then suspended using a newly developed National Institute for Occupational Safety and Health harness accessory (ACCESS), which supports the upper legs. Midthigh circumference changes were 1.4 and 1.9 cm, changes in minute ventilation were 1.2 and 1.5 L/min, changes in heart rate (HR) were 15.1 and 21.6 bpm, and changes in mean arterial pressure were 5.1 and -2.6 mmHg (p < or = 0.05) for all subjects during CHEST and BACK, respectively. Kaplan-Meier median suspension time for all subjects for the CHEST condition was 29 min (range 4-60 min) and 31 min (range 5-56 min) for the BACK condition. The 95th percentile for suspension time was 7 min for CHEST and 11 min for BACK. Cox regression revealed that body weight had a statistically significant effect on the time until experiencing a medical end point (p < or = 0.05) during the BACK condition. Mean (+/- SD) suspension time was 58 +/- 6 min (range 39-60 min) for all subjects for the ACCESS condition. There were no terminations due to medical symptoms during the ACCESS suspension, changes in physiological variables were small, and 85% of ACCESS subjects completed 60-min suspensions. These data provide information on motionless suspension tolerance time to standards-setting organizations and demonstrate the potential of a prototype harness accessory to delay or prevent suspension trauma.

Impact of Harness Fit on Suspension Tolerance

“…Literature has reported that body weight (Turner et al, 2008) and stature (Seddon, 2002) were predictors for suspension tolerance. This study contributes additional information to the literature on the impact of harness fit on suspension tolerance.…”

Harness suspension and first aid management: development of an evidence-based guideline

“…Since the completion of this literature review, work has been published by Turner et al that examined the use of a passively deploying mechanism to elevate the legs during harness suspension 19. Using this mechanism, suspension was tolerated for a mean of 58 min without any subjects experiencing presyncope, all withdrawals were due to discomfort.…”

Development of sizing structure for fall arrest harness design

“…In study I, the harness was tested for fit while participants were both standing and suspended. A pass or fail rating was assigned based on four criteria that are in use in the harness manufacturing industry to minimise any potential biomechanical stress and suspension trauma (Brinkley 1988, Turner et al 2008. The pass criteria were that: (1) the harness back D-ring was positioned between the inferior and superior borders of the scapula while the participant was standing; (2) the suspension angle had to be equal to or less than 358 during the suspension condition; (3) the chest strap should not make contact with the neck while the participant was suspended; (4) the centre of gravity (COG) of the body had to be behind the hip rings during the suspension condition.…”