Harness Induced Pathology Produced by: Federation Francaise de Speleologie.
Printed with permission of Hank Moon Technical Information Manager, Petzl America
As published in the 1997 Petzl Work/Rescue Catalog 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 cause,
which have previously said to be due to exhaustion. In all other cases of rope ascension, no similar problem could ever 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, these new sets of experiments allowed us to set up new parameters.
The main controlled parameters were:
- Pulse
- Blood pressure
- Electrocardiogram
- Electroencephalogram
- Diverse blood controls.
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. The first subject was in a real situation, with his head in hyperextension and his legs dangling below heart level. The second subject wore a brace in
order to eliminate the hyperextension of the head,his legs still dangling. Finally, the third subject had his head in hyperextension but with his feet in foot-loops, keeping his legs in a horizontal position. In all
three 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 garrote.
Abnormal feelings described by the volunteers clearly reveal a nervous compression, but this is not significant. Discomfort due to blood return after garrote, 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 three experiments, similar changes took place concerning heart rate and blood pressure. These changes illustrate well the efforts of the blood system to adept
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 reach18/12. 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 origen 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:
- A caver in difficulty on a rope, due to exhaustion or to technical problems, must be helped very quickly.
- A caver hanging completely inert must be unhooked with all speed by other team members.
- A team shall never let one of its members begin a rope ascent alone, even if he is in very good shape.
- A tired caver should refuse to begin a long and difficult ascent, especially in a wet pit, without recovering first. He/she must carry and use properly his/her survival food and emergency shelter.
By following these recommendations, one should be able to avoid all danger due to motionless suspension. Today, this is the cause of many deaths, but should not occur in the future. |
