Hidden danger of tree landing

[administrator]

Thanks to Jaan Taagepera for this info.

I hadn't really thought about a tree landing and extended rescue as being particularly troublesome. But putting two and two together between work and pg I'm starting to wonder... At work we consider a worker hanging in his fall arrest harness to be in serious danger. Can't say I've ever heard of a pg related issue though.

from http://www.cdc.gov/elcosh/docs/d0500/d000568/d000568.pdf

Wide ranges of situations require safety harnesses of various types. Workers requiring fall protection, workers entering many confined spaces, mountain climbers, deer hunters in elevated stands, and cave explorers all try to protect themselves through the use of safety harnesses, belts, and seats. What is little known however, is that these harnesses can also kill.Harnesses can become deadly whenever a worker is suspended for durations over five minutes in an upright posture, with the legs relaxed straight beneath the body...

... In a harness, however, the worker can’t fall into a horizontal posture, so the reduced heart rate causes the brain’s blood supply to fall below the critical level. Orthostatic incompetence doesn’t occur to us very often because it requires that the legs remain relaxed, straight, and below heart level. If the leg muscles are contracting in order to maintain balance and support the body, the muscles press against the leg veins. This compression, together with well-placed one-way valves, helps pump blood back to the heart. If the upper-legs are horizontal, as when we sit quietly, the vertical pumping distance is greatly reduced, so there are no problems.In suspension trauma, several unfortunate things occur that aggravate the problem. First, the worker is suspended in an upright posture with legs dangling. Second, the safety harness straps exert pressure on leg veins, compressing them and reducing blood flow back to the heart. Third, the harness keeps the worker in an upright position, regardless of loss of consciousness, which is what kills workers.


See also: http://www.osha.gov/dts/shib/shib032404.html