Harness-induced Pathology

In the past few years, a new type of accident has appeared in the caving world: death due to hypothermic exhaustion by hypothermia. Such cases have also cured on rope when the "frog" method of rope ascent was used. 15 cases have been noted and each time the reason for death was the same phenomenon of hypothermic exhaustion. A 1983 study of these deaths has led the Medical Commission to consider the possibility of a new factor: 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 were thought to be to dangerous, and were stopped immediately. They did, however, led to the assumption that even a healthy caver could die very quickly if left hanging "total inert" (without muscular movements) in a sit harness. Total inertia evidently occurs each time a caver is unconscious, after a cranial traumatism, for example.

It 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 progression, no serious difficulties have been noted. The seriousness of this phenomenon and the hope to find an efficient solution led us to organize new experiments, but this time in a hospital. These new experiments took place in the Besancon Hospital where medical equipment was available. The main controlled parameters were:

• Pulse
• Blood pressure
• Electrocardiogram
• Electroencephalogram - several blood controls

Despite the availability of resuscitation equipment, the SOP for the experiments ordered a "quick release", for each volunteer before any serious difficulties developed. To try and find a solution, 3 different experiments took place at the same time. The first volunteer was in a "real" situation with his head in hyperextension and his legs dangling under heart level. The second volunteer wore a neck brace in order to exclude the head hyper-extension factor (legs dangling as before), and the third volunteer had his head in hyper-extension, but left his feet in the foot loops, keeping his legs in a horizontal position.

In all three cases, the volunteers experienced considerable difficulties after 12-13 minutes of hanging, one of them actually fainted in spite of the medical controls and monitoring. The observed phenomena are similar to the 1983 conclusions when both volunteers fainted due to lack of experience. 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 dilation is obvious. The physical mechanism of faintness is complex, but can be described as follows: perturbation of the cardiovascular system, leading to head blood failure, quickly followed by death.

For all three experiments, similar changes took place concerning heart rate and blood pressure. These changes illustrate the efforts of the blood system to adapt itself to a stress situation.

In the first case, the volunteer feels faint after 10 minutes. At the beginning, the pulse is normal 80. Progressively, it will increase until faintness. Concurrently, the blood pressure, normal at first with 120/80, will increase abnormally to reach 180/120. Faintness with hot flushes, paleness, abundant sweat, and breathlessness take place during more intense blood pressure acceleration. Without a quick unhooking, faintness can be very serious. Unhooking before faintness provokes a brutal return to the heart of blood that 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 accelerates within 5 minutes. In order to avoid a serious second faintness, the person is unhooked.

In the second case, thanks to the brace, we can say with certainty that the origin of faintness is not entirely cervical. In that case the unhooking took place after 20 minutes.

In the third case, unfortunately, we couldn't 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 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 leads to very serious blood problems. It seems useless to try and invent a preventative harness.

The experiments led to the following advice:

• a caver in difficulty on 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 must carry and use properly his survival food and 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 be nonexistent in the future.

Produced by the Federation Francaise de Speleolgie and published in the Toronto Caver, May, 1994, and various other places.