Harness Induced Pathologyby the National Outdoor Leadership School
Original video produced by: Federation Francaise de Speleologie.
This translation by Christian Bisson
©1996 NOLS. Used with Permission.
In the past few years, a new type of accident has appeared in the caving world: Death due to exhaustion by hypothermia. Such cases have also occurred on-rope when the "frog" method of rope ascent was used. 15 cases have been noted and each time the reason for death was attributed to the same phenomenon of exhaustion. A 1983 study of these deaths has led France's medical commission to consider the possibility of an additional factor potentially responsible for the cause of death: suspension in a sit-harness.
In 1984, the first indoor experiments took place. The first two volunteers fainted and experienced serious difficulties, one after only 6 minutes of hanging. These tests, thought to be too dangerous in this experimental context, were stopped immediately. However, the hypothesis is well confirmed. In a particular context surrounding total inertia, which means without any voluntary muscular action for adaptation, a healthy caver could die very quickly due to his/her suspension.
This particularity of total inertia is evidently found in situations involving an unconscious victim such as after a cranial trauma.
This phenomenon is highly suspected in cases of death without understandable causes, which have previously said to be due to exhaustion. In all other cases of rope ascension, the problem could never be explained.
The seriousness of this phenomenon and the hope to find an efficient solution led us to organize new experiments in a hospital setting.
Organized in the physiology labs of Besanon Hospital, the new set of experiments allowed us to set up new parameters. The main controlled parameters were:
Despite the availability of resuscitation equipment, the safety of each subject was assured by the use of a quick-release (5 seconds) which would be used before any serious difficulties developed.
In the hope to find a preventive solution, 3 different experiments were attempted:
In all 3 cases, the subjects experienced considerable difficulties after 12 to 30 minutes of hanging. One of them actually fainted in spite of the medical controls and monitoring.
The observed phenomena are similar to the 1984 conclusions when both volunteers had experienced serious difficulties to the point of fainting due to the lack of experience of the research team.
Pulse control excludes the phenomenon of blood garrot. Abnormal feelings described by the volunteers clearly reveal a nervous compression, but this is not significant.
Discomfort due to blood return after garrot, quite low in the feet, is higher in the hands and neck, where venous dilatation is obvious. The physical mechanism of faintness is complex but can be described as follows: perturbation of the cardiovascular system balance, leading to a failure of the blood circulation with cerebral ischemia quickly followed by death.
For all 3 experiments, similar changes took place concerning heart rate and blood pressure. These changes illustrate well the efforts of the blood system to adapt itself to a stress situation.
With all data in a diagram, we can better understand the process. In the first case, the subject feels faint after 10 minutes. At the beginning, the pulse is normal at 80. Progressively, it will increase until faintness. Concurrently, the blood pressure normal at first with 12/8, will increase abnormally to reach 18/12.
Faintness with hot flushes, paleness, abundant sweat and breathlessness take place during a more intense pulse and blood pressure acceleration. Without a quick unhooking, faintness can be very serious. Unhooking before faintness provokes a brutal return to the heart of blood which was in the legs. The signs of faintness persist for a few minutes. The hyperextension of the head is very painful and leads to a quicker faintness. A manual correction of head hyperextension lessens the troubles, but pulse and blood pressure accelerate again within 5 minutes. In order to avoid a serious second faintness, the subject is unhooked.
In the second case, thanks to the brace, we can say with certainty that the origin of the faintness is not entirely cervical. In that case the unhooking took place after 20 minutes.
In the third case, unfortunately, we could not avoid faintness, although the legs were in a high position. We point out that active leg movements are a good thing, but only for a short time, after which difficulties worsen rapidly. It is almost certain that this is what had happened in all death cases due to exhaustion.
Faintness is a complex medical matter, but we can come to the following conclusions: Whatever the type of harness, motionless suspension is not physiologically safe and will eventually lead to very serious blood circulation problems. It seems useless to try to invent a preventative harness.
The experiments led to the following advice:
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