The heart activity showed a constant change independent of all other individual variations, which was noticeable in all subjects. Upon introduction into the water with narcotized subjects as well as nonnarcotized subjects, the heart rate went suddenly to about 120 per minute. At a rectal body temperature of about 34° C. [93° F.] it then began to become increasingly slower and to sink continuously to about 50 per minute.
The bradycardia at a body temperature of about 29° to 30° C. [84° to 86° F.] changed suddenly to an arrythmia perpetua or, as the case may be, to a total irregularity and this began with a slow form of about 50 beats per minute; this slow form of irregularity could be transformed into a faster one. The transformation to the faster form was not an unfavorable sign regarding life.
When an electrocardiographic control after the experiment was possible, it regularly showed a Vorhof flutter. Let it be anticipated that this irregularity could continue to exist after the cessation of the cooling and a recovery of the body temperature to 33° or 34° C. [91° or 93° F.] 1½ to 2 hours after removal from the water, but then customarily changed of itself and without therapeutic aids into a coordinated heart activity. In the same way let it be anticipated that in all cases with a lethal termination, a sudden cessation of the heartbeat ensued upon an irregularity of the slow type.
A check of the blood pressure was attempted, but was in no case satisfactory since an exact measurement was not possible in the decisive stage of the experiment because of the severe rigor and muscle fibrillation.
Reference has already been made to individual differences in the behavior of the rectal temperatures. Figure 4 gives an example which includes four experiments, in which four different experimental subjects were cooled at identical water temperatures and with identical clothing. It was shown that in water at 4.5° C. [40° F.] temperature the time required for reaching a rectal temperature of about 29.5° C. [85° F.] varies between 70 and 90 minutes. But nevertheless the diagram shows that in spite of these individual differences, it is observable that the progress of the rectal temperature proceeds according to rule. The body temperature begins to sink rapidly from about 35° C. [95°-97° F.].
It is of very great practical significance at this point that the body temperature continues to sink virtually lineally for a considerable time after removal from the water. This continued drop can last 20 minutes or more. During this drop an after-drop of 4° C. [7° F.] could be observed, and indeed not only at temperatures under 30° C. [86° F.]. In one case it was observed that an interruption of the experiment at 35° C. [95° F.] after a further lapse of 20 minutes the rectal temperature had fallen 4° to 5° C. [8° F.] more. We will later discuss the “arresting” of this after-drop by physical measures.
In our experimental series, the lowest rectal temperatures which could be survived varied individually just as did the progress of the temperature drop. In general (in six cases) death occurred with a drop in temperature to values between 24.2° and 25.7° C. [75.6° and 77.6° F.]. In one case, however, a drop to 25.2° C. was survived. This experiment fell outside the typical picture insofar as after 90 minutes at 26.6° C. [79.9° F.] a virtually stationary condition of the rectal temperature had become established for 85 minutes. We will come back again to this special experiment.
The skin temperature sinks or drops much more rapidly than the rectal temperature. Within a minute there occurs a thorough saturation of the articles of clothing. Correspondingly the skin temperature falls already within 5 minutes to values between 24° and 19° C. [75° and 66° F.]. After 10 minutes it may have already dropped to 12° C. [54° F.]. Within 10 to 20 minutes more after the beginning of the experiment the steepness of the drop changes considerably. The curve of the skin temperature runs for some time, that is, for 15 to 30 minutes virtually horizontal. After this time there follows a further but now slower drop to the lowest figures, which may lie below 15° C. [59° F.] at the close of the experiment.
Parallel experiments which compare the course of the rectal temperatures and the cooling of the body with and without submersion of neck and back of head showed great difference in temperature drop. The curves pertain to the same experimental subject. The one with the deep fall to 26° C. [79° F.] in 70 minutes was obtained with a water temperature of 12° C. [54° F.] the other with a drop to 32.5° C. [90.4° F.] in the same time resulted from a water temperature of 5.5° C. [41.9° F.]. The very marked difference cannot be explained by a variation in resistance of the particular person, but is to be attributed to the position of the subject in the water and his head covering. In the experiment with the water at 12° C. [54° F.] the subject, in a kapok life preserver, lay flat in the water so that his neck and the back of his head were well submerged; beyond this he did not wear a flier’s helmet. In the other experiment with water at 5.5° C. [41.9° F.] the head was covered with an aviator’s summer helmet without headphones. The subject wore a rubber life preserver open at the back; with this, the head is somewhat out of the water.
In order to follow up the effect of isolated cooling of the neck and the back of the head on consciousness, body temperature, and circulation, this was undertaken in three special experiments. The experimental subject lay horizontal; the back of the head and the neck were dipped into a receptacle through which water of corresponding temperature was continuously run. In an experiment of 3 hours duration there occurred small temperature drops of not more than 0.8° C. [1.4° F.]. The water temperature was 1° to 2° C. [34° to 35° F.]. In one case after 50 minutes a marked sleepiness occurred which changed over into a deep narcosis. The heart activity was variable, and obvious bradycardia could not be observed. Irregularity never developed. Changes were not seen in the electrocardiograph. On the other hand in all three subjects the spinal fluid pressure was markedly increased after the ending of the experiment to maximal values of 300 mm. After the experiment, ataxia and definite Romberg phenomena were observed, as well as exaggeration of the normal reflexes; pathological reflexes were absent.