The descending experiments without oxygen show that the limit for a safe escape with an open parachute lies approximately at a jumping altitude of 13 km. [42,700 ft.], since in a jump from 13 km. [42,700 ft.] recovery of consciousness occurred only at an altitude of 1.6 km. [5,250 ft.], and so one must already consider the possibilities of landing in an unconscious condition with all the attendant dangers. This still does not take into account the heavy demands made on the body by the cold and the consequent risk. The great effect of the body position during the experiment makes it obvious how severe is the effect of every additional demand. While, for example, in the 13 km. [42,700 ft.], experiment upon a seated subject, recovery of consciousness took place after 8 minutes 12 seconds at an altitude of 7.2 km. [23,620 ft.], the suspended subjects recovered consciousness only after 19 minutes at 1.6 km. [5,250 ft.] altitude. Correspondingly also, unconsciousness occurred in the suspended subjects much more rapidly than in those who were seated. The same observation was made in the 15 km. [49,200 ft.] experiments, and indeed those who went through the experiment lying down could already state name and birth date immediately upon reaching ground level although they were paralyzed, while those who had been suspended did not respond at all to speech within this time. Except for one mentally very sluggish subject, the return of normal condition occurred much earlier to those who were lying down, namely within 15 minutes. The descending experiments extended to 18 km. [59,100 ft.] altitude with oxygen breathing showed that, except for the danger of cold, escape with an open parachute is possible from these altitudes even though, practically, no need exists for it.
Before we go into a discussion on the falling experiments it seems essential for us to cite the work of Lutz and Wendt on “Animal Experiments on Parachute Jumping from High-Pressure Cabins.” Unfortunately this work was not available to us during these experiments so that we could not build upon the valuable results contained in it and derived from numerous animal experiments, or upon the experience of the authors. Although both authors approach with necessary scepticism the problem of “reaching decisions through animal experimentation upon questions in
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which, in the final analysis, the behavior of the human being in identical situations is of exclusive interest,” they could, and had to depend upon the previously proved experience that no fundamental qualitative differences in the manner of reaction to oxygen lack is to be expected between animals and human beings although there are considerable quantitative differences which, in this case, mean temporal differences. However, the results of our experiments show that to some extent quantitative as well as qualitative differences are present to the extent that the above animal experiments must lead to great fallacies which are significant to future developments. This appears especially in a comparison of results obtained with animals with the collective results of human experimentation upon escape from high altitudes through free fall without oxygen. On the basis of animal experiments, Lutz and Wendt were forced to the conclusion that if oxygen is breathed before the pressure drop “jumps from 14 km. [45,900 ft.] altitude can theoretically be survived—at any rate, that is the maximum altitude * * *,” whereas we were able to carry out human experiments up to 21 km. [68,900 ft.] altitude without any harm whatever. In all experiments at 20 km. [65,600 ft.] the subjects recovered clear consciousness with spontaneous control above 3 km. [9,800 ft.], and so within a sufficient altitude for actual parachute jumping. As instructed before the experiment, the subject rang a cowbell hung up in the chamber by pulling a handle (the equivalent of pulling the rip cord) without a new order to do so, so that under actual conditions they would certainly have also pulled the rip cord at the right time.
Experiments with a pressure drop from 4 km. [13,100 ft.] without previous breathing in of oxygen were not carried out by us because we proceeded from the viewpoint that when contact with the enemy is possible, pressure cabin machines fly with a pressure corresponding to 8 km. [26,200 ft.] altitude and, therefore, the crews would already be breathing oxygen in case of a possible pressure drop as a result of damage to the cabin.
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Since the falling experiments without oxygen had already given such good results, falling experiments were begun only at 20 km. [65,600 ft.] altitude, and, because of the limitations described above, could be carried out only to 21 km. [68,900 ft.]. In these the results obtained by Lutz and Wendt were fully corroborated in this respect, that jumps from above 21 km. [68,900 ft.] can probably be made without danger, and that ebullition of the blood does not yet take place up to 21 km. [68,900 ft.] altitude. On the other hand in a falling experiment with human beings, neither a post-hypoxemic pseudo-death nor a post-hypoxemic twilight sleep were ever observed (Lutz).
In conclusion, we must make it particularly clear that, in view of the extreme experimental conditions in this whole experimental series, no fatality and no lasting injury due to oxygen lack occurred.
V. Conclusions from the Results
For practical rescues by parachute jump from the highest and higher altitudes the experiments yielded the following: