mystery of yawning
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal

mise à jour du
1 janvier 2011
Psychosomatic Medicine
Disorders of mental functioning produced by varying the oxygen tension of the atmosphere
Effects of low oxygen atmospheres on normal individuals
and patients with psychoneurotic disease
Barach AL, Kagan J


0n Claude Bernard's statement that "the fixity of the internal environment is the condition of a free life," Barcroft (ri) suggested that the organism in gaining constancy of temperature, hydrogen-ion concentration, water, sugar and oxygen ultimately reached a stage of development so that man's higher faculties could develop. It is evident that profound biochemical alterations in the body seriously impair mental functioning. Conversely, mental and emotional reactions have been shown by Cannon (17, 18), Pavlov (36), and others to initiate changes in the organic state of the organism. The relation between psychic and somatic processes has been the subject of considerable contemporary investigation, as shown by the reviews of Dunbar (20) and Fetterman (22). In clinical disease, so-called functional and organic manifestations have often been separately classified but it is doubtful whether this division is as valid as it appears; it may well be that apprehension and hyperchlorhydria in a patient with gastric ulcer proceeds from a basic stem that has branched out into manifestations of both a psychic and physical character, rather than that the psychic factor produced the physical change or the reverse. Whether this be true or not, our understanding of psycho-pathology must ultimately be aided by controlled studies of the effects on mental functioning of altering basic physiologic processes as well as the study of physiological reactions initiated by altering emotional influences.
Interference with a steady supply of oxygen to the organism has long been known to impair the functioning of the central nervous sytem. Paul Bert (14) showed that the effects of high altitude were principally due to the lowered partial pressure of oxygen in the inspired air. Since that time the consequences of anoxia on bodily and mental functioning have been studied, at first on high mountains, later in chambers in which the concentration or pressure of oxygen was reduced. The growth of aviation has stimulated additional research on oxygen deprivation in order to determine at what altitude flying is attended with harmful effects. These studies have been extensively reviewed by McFarland (31,32), and our in tention is to refer only to those that form a background for this paper.
The symptoms of moderate oxygen deficiency, which begins after exposure for two or three hours to an altitude of 10,000 to 2000 feet, may be listed as: headache, dizziness, fullness in the head, parasthesias, impairment in memory and judgment. The occurrence of these symptoms, as well as others about to be referred to, led to the proposal that compulsory oxygen inhalation be adopted for commercial pilots flying at altitudes of 50, 000 to 12,000 feet and over, based on the opinion that "pilot error" may be in part due to oxygen-want. (Barach 6). The studies of McFarland and Armstrong (1,2,3) contribute support to this point of view, which hss been also upheld by Boothby, Lovelaee and Mayo (zd). More prolonged exposure leads to nausea, vomiting, tachycardia, slight fever, malaise, and the symptoms originally known as mountain-sickness. From 12,000 to 15,000 feet, these symptoms are more marked, and above 15,000 feet, serious effects are produced in the majority of individuals, in both mental and bodily functioning. A few reports will be briefly referred to. Table I gives the relation between oxygen percentage and the corresponding altitude.
Birley (z) found that pilots after an hour at 15,000 feet took twice as long to sight a target, and that firing time was increased and accuracy diminished. Wilmer and Berens (41) studied the effect of altitude on ocular functions and found slight changes between 10,000 and 15,000 feet, and marked changea above 15,000 feet. McComas (30) reported that subjects with latent esophoria saw double between 10,000 and 15,000 feet. Standard psychological tests (including sensory perception) at 14,000 feet showed deviations from the normal after short exposure (Tanaka, 39), (Lowason, 29), (Dunlop, 21), (Watson, to). In experiments by Barach, McFarland and Seitz (9), exposure to an altitude corresponding to 12,000 feet for three hours resulted in a marked increase in errors in slide rule exercises in three out of four university students. Effort on the part of the subjects was motivated by payment of a small sum for each correct answer. Lack of emotional control was also manifested in two of the subjects. McFarland and Baraeh compared the reaction of normal individuals to psychoneurotic patients after inhalation of 10 per cent and 12 per cent oxygen. Of a group of 40 patients and an equal number of controls, approximately 70 per cent of the patients collapsed in 90 per cent oxygen (corresponding to 20,000 feet), whereas only 94 per cent of the controls were so markedly affected. Psychological rears revealed a more marked impairment in the psychoneurotic group. The rapidity of exposure to low oxygen atmospheres was shown to exercise a marked influence by Schwartz (38) who made observations on the effect of a rapid ascent to 16,000 feet as compared to a slow ascent. In the former the subjects recorded an average figure of 905 complaints; in the slow ascent only 59 complaints.
Armstrong (4) exposed young aviators to a lowered oxygen pressure in a chamber, corresponding to 12,000 feet, for hours daily for 6 weeks, and observed the development of symptoms which were similar to those found in "aeto-neurotic" aviators, namely, apprehension, irritability, gastric complaints and a diminished sense of well-being. Kroetz (28) has reported in neurotic patients showing vasomotor instability (in the absence of cardiorespiratory disease) a lowering of the arterial oxygen saturation to 88 per cent when a painless arterial puncture brought about pallor and sweating. Hicks (26) found a diminished arterial oxygen saturation in psychoneurotic subjects at rest, in the absence of vasomotor reactions. The findings of Kroetz and Hicks have not been confirmed but they also suggest a relation as yet unclear between anoxia and apprehensive states. Haldane (24, 25) during the War pointed out that soldiers who exhibited the symptoms of "neurasthenia," fatigue and "shock" were apt also to show shallow breathing, fatigue of the respiratory center (shortness of breath on exertion) and exaggeration of circulatory reflexes, suggesting to him the possibility that sriilitary neurasthenia was a more lasting form of ordinary fatigue due to oxygen-want. Bareroft, Hunt and Dufton (12) reported that patients with chronic gas poisoning were greatly improved, both physically and in respect to their psychoneurotic tendencies, after one week in a chamber with go per cent oxygen.
In studies by Barach and Richards (7,10,37) of the effects of inhalation of 50 per cent oxygen on patients with chronic cardiac and pulmonary disease, striking alterations in the mental state of the patients have been observed. Coincident with the relief of acute dyspnea, there is a diminution in restlessness and apprehension, with an increased tendency to sleep. However, in patients in whom pre-existing anoxemia has been severe and prolonged, the administration of 50 per cent oxygen has at times provoked irrational states, delirium and coma beginning with several hours of treatment. In one case of pulmonary emphysema, relief of dyspnea and cyanosis was followed by the patient lapsing into a coma which persisted for six days. The patient was completely irrational when aroused. At the end of the sixth day he awoke cheerful, rational, and alert. Prior to treatment he had been apprehensive and depressed; following oxygen treatment he was optimistic and unworried, as long as the oxygen concentration in the atmosphere was not prematurely reduced. It is characteristic of patients with severe long-standing anoxemia that a cheerful mental state ensues following the deep sleep or coma which oxygen treatment sometimes provokes. When an active delirium develops soon after oxygen treatment is begun, the patient may be difficult to control but in these instances also continuation of oxygen treatment is followed by resumption of a normal mental state.
In summary, it may be stated that variations in the oxygen tension of the blood both above and below what the organism has been accustomed to may be attended with profound alterations in mental functioning. The purpose of the study to be reported was to observe the effects of inhalation of 53 per cent oxygen for a three-hour period in normal individuals and in psychoneurotic patients, not only in respect to efficiency of intellectual function, such as memory and judgment, but also from the point of view of affective response, mood and emotional control.
Method of investigation
There were no differences in efficiency of response to the retention and recall test at the end of the three hour test, between those subjected to abrupt and those subjected to gradual exposure to oxygen want, either in the student or patient group. However, the subjects almost uniformly noted that the gradual onset of anoxemia was accompanied by a sense of well-being, with at times a prolonged feeling of elation and a diminished frequency of somatic complaints. These findings are in agreement with those of Schwartz. Three students described their reaction to gradual reduction of the oxygen percentage, which was the second exposure, as follows:
Mr. B.: "1 feel different from the last time, you must be giving me an excess of oxygen. T feel slight elation, my legs are not twitching like the last time. Last time it seemed like coming into a different world."
Mr. K.: "I don't have a real headache this time."
Miss S.: "Last time J felt more dull."
In the 17 medical students exposed to inhalation'of 13 per cent oxygen for 3 hours, characteristic complaints were: a mild or severe frontal headache, slight dizziness, yawning, sense of oppression, pain in the joints and epigastrium, tingling sensation in fingers and toes, jitteriness. Changed perception of color was observed in some of the subjects.
Ten of the 57 students (59 per cent) showed shorter or longer periods of elation during which facial expression changed; increased motor activity took place in the form of tapping, singing, whistling and pressure of speech; increased productivity, flightiness, facetiousness, heightened sense of well being were also observed, all of these symptoms resembling the hypomanic state. 1'he period of elation was followed by dullness, drowsiness, and deep sleep, from which the subject could be awakened only after repeated attempts. Awareness of having been asleep was generally absent, and the ability to distinguish between dream experiences and reality showed some impairment. For example, one subject was convinced of having had several convulsive seizures and remembered having been surrounded by relatives and physicians. It was impossible to assure him of the imaginary nature of this experience. Lowering the oxygen content precipitated a short period of elation followed by a pronounced drowsiness and sleep, as illustrated in the subjects' own description:
Mr. A.: "It's as if I was drunk. Now it's worn off. I want to sleep. Then all of a sudden J catch myself as if I was afraid for some reason. I feel funny, full in the chest. At the beginning J felt like in the beginning of drinking, I felt like being facetious."
Mr. S.: "Either I am getting superabundance of energy or what, but I am getting restless."
Mr. P.: "I feel much more clear than when I came. I have had an emotional disturbance for a few weeks. I am happier than when I came. J have not been bothered by any thoughts. I don't seem to think about it at all." 'Ihe same subject states later: "J feel dizzy, I have a headache, my thinking is dull. I have to read one sentence over l don't know how many times. J want to study, but my mind seems to be wandering off. I have no thoughts. Don't bother me, I am sleepy."
In the remaining 7 of the students (41 per cent) the period of elation was not observed. Irritability, dullness resulting in marked listlessness and especially poor performances on psychological tests were noted, together with a changed perception of their own body, such as: 'My ears seem to pull up," "My head feels big and light." Vague, undefined fears, feeling of strangeness and detachment from the world were frequent. It is best illustrated by the subjects' own description.
Mr. R.: "I feel pretty good, when look at it all. I feel ton good. My voice is notably bad. I should not subject you to hearing me." Then later: "I am restless, my head feels big and light. The light in the room has different color. You look pretty icteric. Things look different. I have not much desire to concentrate much. I sort of feel a little silly, the way one feels when one is hysterical. Subjectively, one feels nothing, semi-detachment, as if you were not completely responsible."
Mr. 7.: "1 feel like coming out of hypnotic sleep. The hours pass awfully quickly. The world looked strange when I came out, it passed away very quickly." Inability to concentrate was observed in all cases and was especially marked after two hours exposure to the lowered oxygen concentration.
Mr. S.: "I read the last sentence ten times and I don't know what's all about. I stopped thinking long ago."
Mr. K.: "I have difficulty in reading, my head feels heavy." Mispronunciations were observed several times. They consisted in omission of letters, as such as "obsinate" instead of obstinate, "olneraly" instead of alternately. Objectively, we observed dullness, lethargy, and listlessness. Complaints of blankness, apathy and extreme fatigue were especially pronounced after the experiment. Subjects described these sensations as follows:
Mr. N.: "I am awfully darned tired, as if I should climb back and go to sleep, I don't feel like doing anything."
Mr. M.: "My mind is not absolutely clear, I am confused for one thing, I feel a bit dizzy, I can't think as well as I should, I feel dull right now."
Mr. B.: "My mind is in a jumble, I can't think of anything, I got a headache."
With very few exceptions the perception of time seemed to be affected. Three hours were estimated by the majority as two, or less. In the patient group the somatic complaints were essentially the same as in the student group with the exception that they were not as frequent and less pronounced. A great majority of the patients expressed suspicion that some stimulating drug, or ether had been added to the gas mixture. All expressed a fear of death by suffocation during the 3 hour period. Five of nine patients had a prolonged period of moderate or marked excitement, motor restlessness and overactivity with threatening behavior. Extreme ovsrproduetivity, lack of inhibitions, and extremely forward and frank sexual advances were made. Sensations of well being, exaggerated self-esteem, and thorough enjoyment of the situation were the most prominent features. Some of the subjective observations were:
Mr. S.: "I am afraid. It's like falling asleep in ether. My breathing puts me to sleep. I see it relieves tension by breathing. Every time you breathe you relax. I will smother in a little while. I feel dizzy. I feel a little sick. I feel cramps right here in my stomach. I feel helpless. I am not master of myself. I shall rip it off. I know I am better than the average. The other patients would raise Dickens. 1 know how to stop it. Don't you think 1 have been analyzed pretty well, I know the ropes. I am getting there. I mean I am beginning to understand the tricks of subconscious. I am feeling better. I am enjoying it. I like it here ... With you it would be a double pleasure 11 make a good psychoanalyst. I know as much as you do. I feel a little smothered. I have the feeling to rip it open. I bet fellows like me make better psychoanalysts than you or Dr. S."
Mr. W.. "The air seems slightly chloroformed. It's like an incubator the generator of loosening of thought. I have the feeling that something. This machine is stopping, I think you have to go into it. You and I should be here, we could...
Mr. B.: "I am not bashful in the tent. I feel a little happy. I feel like I had a lot of whiskey. I have a headache, the same sort of headache I get when I am drunk. My breathing comes in jerks." (Is told the hour of day.) "Jesus Christ, I thought one hour passed, how quick. I'll miss the tank."
Mr. B. (after the tent): "Oh boy, Oh boy, I heard a sound in my head. It seems like a sound going from one side to another. It's like a lot of thin fiat lines, pencil lines rising to the sky. It's hard to describe. It's passing very quickly. It's like a cavern when it is quiet. The great silence is worse or almost like a noise. That's the beat way I can describe it. I don't fear you, I fear this room less. I feel a lot relieved of the tension. My headache is practically gone."
Four patients did not show any period of excitement. They were irritable, dull and drowsy by the end of the first hour and remained so throughout the experiment.
Mr. S.: "Everything seems so distant, so far away. Whatever I try to think about seems immaterial. I try to think about it, if air were not coming I would not do anything about it."
It must be remarked that no deviation from usual behavior in the above mentioned patients was noted when the experiments were conducted in normal air. After the three hour exposure to low oxygen was over, the behavior of the patients did not differ noticeably from that of the medical students. They were all dull, lethargic and fatigued. The "repetition and recall" test described above has proven to be not only an indicator of purely retentive capacity, but allowed us some insight into the functioning of the individual as a whole, since not only the number of errors but the type of errors and general behavior during the test were significant.
The results of these tests on each subject in the student group is listed in Table II. For the entire group of medical students the average number of errors in the control test prior to the experiment was j6.s while the average after the experiment was 52.5; that is, for the entire group there was 45.. per cent more errors as a result of the anoxia induced. In 2 of rj students there was no demonstrable impairment in mental functioning. Our subjects reacted to the retention and recall testa as did those of Curran and Schilder (19), who state:
"We come to the conclusion that we deal in our experiments not only with changes in the recall, but also with changes in the organization of traces. Our experiments show clearly that a change in the trace from repetition to repetition does not consist merely of a fading of a trace and the lessening of the efficiency. It occurs in our protocols again and again that words and sentences which were not available at a previous recall become available at a later recall."
Not only was this true in the teat under normal conditions, but also after the exposure to 53 per cent oxygen in all groups. We found the first three stories exhibited the largest number of omitted words, these latter reappearing in the later repetitions of the story until a certain pattern was established. This pattern was subsequently maintained with some variation during the remainder of the test.
Our experimental findings are further in accord with those of Curran and Sehilder (19) in that our student group exhibited a tendency to replace more complex words with simpler ones before, as well as after, exposure to 13 per cent oxygen. In the patient group, however, we noted a definite tendency to replace simpler words with stilted, formal, and rarely used ones.
We found a considerable difference in rapidity of pattern formation as well as in the type of errors not only between the student and patient groupa, but within each group, depending upon whether the teat was taken before or after the exposure to 13 per cent oxygen.
The results of the retention and recall test on each subject in the potient group is listed in Table III. For the entire group the average number of errors prior to the experiment was 75,45, while the average number after the experiment was 60.96, that is, 19.2 per cent decrease in errors after the exposure to 13 per cent oxygen. On the other hand, in our student group we find an increase of 45.4 per cent in the number of errors after the exposure to 53 per cent oxygen.
Analyzing the errors in the student group, we find that the number of omitted words increased after exposure to lowered oxygen. The chief reason for this increase was the number of words added to the original story. The added words are not the result of increased productivity as they express extreme hesitation, uncertainty, perseveration, and confabulation. This latter state is closely related to organic confusion. The retold stories as a whole were hazy, or nonsensical at times. Preoccupation with insignificant details, and elaboration were frequent. A pattern is not established until very late and even then showed a greater variability. Similar results have been observed in serial drawings of a man (Goodenough test) after insulin coma, and Metrazol seizures, where it seemed to be the expression of organic confusion (23).
Analyzing the errors in the patient group we find that the number of words omitted before the experiment was somewhat greater than after exposure to 13 per cent oxygen; furthermore, many more words were added beforethe experiment than after exposure to lowered oxygen. This is an opposite tendency to that shown in the student group. The words added by the patients reflect their usual preoccupations with a resultant inability to concentrate, After exposure to 53 per cent oxygen some degree of relaxation was obvious despite the dullness and fatigue which were objectively and subjectively perceived. It will be remembered that in the more severe anoxia produced by inhaling io per cent to sa per cent oxygen, McFarland and Baraeh (jg) found more severe deterioration in psychoneurotic patients than in the control group, with mort marked physiological impairment as well. Apparently, the milder degree of oxygenwant used in this study was not sufficient to produce marked physiological changes. In 4 patients, the effect of 13 per cent oxygen was none or only a slight decrease in efficiency; in patients there was an improved response, apparently related to freedom from their usual preoccupations.
The actual results of the "retention and recall" testa upon which we base our conclusions can best be illustrated by recording the following representative series of observations: For these studies we used the following two stories for both groups. When one story was used before the experiment, the other was used after.
1) Weakened by rain, the front of a three story brick house collapsed today. The wall dropped like a curtain revealing Mr. Lester dressing and Mr. Reed in bed. They were the only occupants. "Is it time to get up?" Mr. Reed just asked. The crash came, and Mr. Lester shouted "yes." They were stranded when the stairway gave way, and were rescued by firemen with ladders.
2) Olaf Nelson died here today of burns suffered when a match ignited his grass skirt in a hula dance comedy during the American Legion Convention. District Attorney Moore lighted a cigarette and tossed the match. Brown interviewed fifteen witnesses who said Moore deliberately tossed the match to Nelson's costume.
Student Group
Mr. L. Story before the experiment: Weakened by rain the front of a brick house collapsed today. There were two occupants, two occupants were revealed. Mr. Lester standing up, and Mr. Reed in bed. "Is it time to get up?" Mr. Reed asked and Mr .... Wall... then the wall collapsed and Mr. Lester said "yes." The stairway ... they could out escape by the stairway because that was blocked. The firemen rescued them with ladders.
Mr. L. Story after 3 hours exposure to 13 per cent oxygen: Nelson suffered from injuries ... I think you said ... well, caused by burning skirt made of grass. I think you said the accident or incident happened on the ou said you did not say an Island, you were niore specific about it, you said the Island. It happened on the Jslaod of Honolulu. I don't remember if you said at the beach or no the beach ... the beach ... or whether the beach came in when the District Attorney charged Morgan. District Attorney charged Morgan .. . . ou, District Attorney charged that Morgan was smoking on the beach near by. I know you did not say Nelson . . . you said him. Now next sentence is Mr. Brown questioned ss witnesses, who said he was smoking who saw him smoke a cigarette, who saw the cigarette tossed at him.
Mr. B. Story before the experiment: Weakened by rain the wall of a three story brick house fell down and revealed Mr. Reed in bed and Mr. Lester getting dressed. Mr. Reed asked, "Is it time to get up?" Then a loud crash revealed that the stairway gave way and they were left stranded. That's all.
Mr. B. Story after the experiment: I did not get too much of the story. I don't know much. Some one by the name of Nelson committed a murder, or something. There is something of hula dance .... I don't know how it came in ... and then District Attorney Brown had something to do with the ease. He questioned somebody that's all I can make out.
Patient Group
Mr. F. Story before the experiment: After the front wall of building or the front part was weakened by rain it collapsed ... those are not the words. I am rephrasing ... revealed.... T make two sentences of it ... Mr. Lester. I don't want to say Mr. just Lester, dressing and Reed in bed. Just before it happened Reed asked, I don't know whether asked Lester, or just asked. Whether it's time to get up. I asn beginning to think whether they were in the same room or different parts of the building. I don't recall now. Costing back to the story of course if they were in different parts of the building. well ... story ... of course would fall namely before Lester had a chance to answer the crash occurred ... but I'll stick to central idea. I'll have to say they were in the same room . . . greater probability in my miud .. . . They were stranded either when the stairway was blockaded or had collapsed.
Mr. F. Story after the experiment:
Olaf Nelson died today of burns suffered when the grass skirt which he was wearing during a hula dance which he was doing during an American Legion comedy ignited. Mr. Moore tossed the match after lighting a cigarette. District Attorney Brown after interviewing 40 witnesses, I think ... I know. all right I think I am making up his skirt was ignited wUe he was doing orne of this . . . said he will hold Brown because he felt that Moore deibcrately held the match to Nelson's kirt.
Mr. S. Before the experiment: I am orry, it's hard for me to start. It's a wall that collapsed of a building It's about a wall .... I don't recall the details .... The last sentence you said one person asked, the other answered 'yes" and the wall collapsed.
Mr. S. After the experiment: Nelson DIaf died today of burns suffered while his skirt was ignited while he was doing o dance. District Attorney Brown said that he will press charges of manslaughter against Moore, which supposedly ignited a cigarette and tossed the match at Nelson Olaf. There are a witnesses that claim that Moore deliberately ignited Nelson's skirt.
In comparing the average results of both experimental groups we find the poorest performance of the student group exhibited fewer errors than did the patient group in their best performance. However, a comparison of performance within each group shows that 15 of 57 in the student group exhibited an increase of errors after exposure to 13 per cent oxygen while ç of in the patient group showed a decrease.
We have already mentioned that in the student group we supplemented our "retention and recall" test with observations using the Rorschach test. Since the interpretation and scoring of this teat is not yet standardized, and considerable controversy still exists about many pointa, we followed the original method of Rorschach. It must be remarked that a number of the students showed a marked deviation from what is generally considered the normal. The results of the Rorschach teat given immediately after production of anoxia as compared with the results obtained 4 to 8 weeks later, merely show a swing in mood, where each individual follows his inherent pattern.
The suggestion has been made that the mechanism of oxygen utilization may be impaired in patients with psychoneurosis (34). The disturbance in affective behavior produced by inhalation of low oxygen mixtures indicates clearly that an accustomed oxygen supply is essential for a controlled emotional existence. Although efficiency of memory appeared superficially improved in of the 9 patients with psychoneurosis, this must be considered in the light of a very poor control; their nervous preoccupations prevented them from attention to the story and interfered with their ability to concentrate. However, the impairment of those inhibitions which are responsible for emotional control was far more marked in the patient group than in the students. Since the investigator who recorded the actual testing was a young woman, the release of the sexually inhibiting agency was especially apparent. In a previous study (9), release of sexual inhibition was observed by a male investigator working with undergraduate students, although to a much smaller degree. The results of this investigation are in harmony with the previously reported findings of McFarland and Barach (34), the patients with psychoneurosis are more adversely affected by acute anoxia than normal individuals.
The question still remains: is an organic unfitness of the central nervous system in respect to its utilization of oxygen a primary factor in the production of psychoneurosis, or does a disturbed psychoneurotic attitude adversely affect the response to acute anoxia? We mentioned earlier in this paper that a third possibility exists in the interpretation of psychosomatic disease, namely, that the psychoneurotic pattern and an impaired mechanism for handling anoxia may be branches from a primary etiological stem, the exact nature of which is still obscure. We are able at this time merely to state that an accustomed oxygen supply is a requirement for undisturbed mental functioning.
The fact that apparently sane, wellbalanced patients with chronic cardiac and respiratory disease may temporarily show profound disturbance in mental functioning as a result of inhalation of 50 per cent oxygen has only been briefly referred to in previous studies (7,10,37), It is of interest that headache, which is uniformly present as a result of acute anoxia, is a frequent accompaniment of oxygen treatment in patients with pulmonary emphysema. When arterial anoxia has existed for a long period and is of marked degree, irrationality and delirium may occur within a period of several hours; in other cases, a slowly deepening stupor or coma may take place, with periods of irrationality when awakened. In some patients, lassitude and mental depression occur without increased sleep. After a period of several days to a week, the mentality clears and the patient generally manifests a cheerful and optimistic attitude. It seems definite that it is the disturbance in the oxygen supply to which the human subject has become accustomed that upsets mental functioning.
In human subjects intoxicated by alcohol, Palthe (35) found that inhalation of 100 per cent oxygen overcame to a considerable extent the effects of alcohol. These results have been partially confirmed (5, 8), suggesting that alcohol is at least to some extent an agent that results in tissue anoxemia. In this instance, as in adaptation to low and high oxygen atmospheres, the individual may become accustomed to a certain level of anoxia.
In an experiment on the treatment of dementia precox, a psychiatric ward was kept at an oxygen concentration of 50 per cent for two and a half months (27). No effect on patients with demen ti a precox was observed as a result of this long-continued exposure to a high oxygen atmosphere; the arterial oxygen saturation in this study was within the range of normal. The male attendants were unfortunately not studied systematically from a psychological point of view but no change in their behavior or attitude was observed. 1h the clinical experience of the senior author over a period of many years, no mental changes have been observed in patients treated with oxygen when previously existing anoxemia was absent.
The reactions of two groups of subjects, one consisting of 17 medical students, the other of patients from the mental hygiene clinic of Bellevue Hospital, were studied prior to, during, and after exposure to 13 per cent oxygen for three hours. The basis for reaction evaluation was the "retention and recall" test, and in the student group, the Rorschach test as well. In addition, alterations in behavior, mood, speech and subjective complaints were recorded.
In executing the experimental procedure, the oxygen content of the atmosphere was gradually lowered in one instance while in the other the concentration was lowered abruptly to a 13 per cent oxygen concentration. In the former experiment a more prolonged period of elation and a diminished frequency of somatic complaints were observed. Aside from the aforementioned differences, no other alterations were found to exist as a result of the difference in the technique of applying the reduced oxygen concentration.
In the student group, during the 3 hour inhalation of 53 per cent oxygen, all 57 complained of a frontal headache; mild dizziness, yawning, sense of oppression, pain in the joints and epigastrium, and tingling sensation in the fingers and toes were frequent. Changed perception of color and of their own body and vague, undefined fears were observed. Inability to concentrate occurred in all cases. This was especially pronounced by the end of the second hour. The perception of time was slower in that the time intervals were evaluated as shorter than actual. Mispronunciations were noted several times. Fifty-nine per cent showed shorter or longer periods of elation resembling the hypomanic mood, followed by dullness, drowsiness, and deep sleep. The ability to distinguish between sleep and reality showed some impairment. Forty per cent of the group did not show any period of elation. Irritability and dullness, resulting in listlessness and especially poor performances on the psychological tests, were noted. After the three hour residence in 53 per cent oxygen, lethargy, complaints of blankness, apathy, extreme fatigue, sense of estrangement and detachment from the world were observed in a great majority of the subjects.
In the patient group, somatic complaints were essentially the same as in the student group except that they were less pronounced and less frequent. A great majority of patients expressed the suspicion that come stimulating drug was added to the gas mixture, and they expressed a fear of death by suffocation during residence in the hood. Fifty-three per cent of the patients exhibited a prolonged period of excitenient, extreme productivity, lack of inhibitions, frank sexual advances, sensations of well being, exaggerated self esteem, overactivity, restlessness and threatening behavior. i'he remaining forty-seven per cent of the patients did not show any period of excitement. They were irritable, dull and drowsy from the eisd of the first hour, and reniained so throughout the experiment.
The students made 45.4 per cent more errors in the "retention and recall" test after inhalation of 53 per cent oxygen as compared with their nonxial test. Errors in the test occurred in 15 of the 17 students. 'fisc number of added words accounted for the poor performance. The added words expressed hesitation, perseveration, uncertainty, confabulation, and elaboration-a state closely related to organic confusion.
The patient group showed 19.2 per cent less errors as conspared with their normal test. The number of added words, reflecting their usual preoccupations, was the chief reason for this high percentage of errors in the normal test. In ç of 9 patients, the efficiency of response was better after inhalation of 13 per cent oxygen. Some degree of emotional relaxation was observed after the exposure to lowered oxygen.
Comparing the performances of both groups we find that the patients made 10 per cent more errors in the normal test as compared to the normal test of the students. Furtherissore, the best performance of the patients, i.e., after the exposure to low oxygen, still showed 68 per cent more errors than the best perfonsiance of nsedical students in their normal test. 'fhe results with the Rorschach test (13) after the exposure to low oxygen as compared with the test done to 8 weeks later showed only a superficial change. The differences observed indicated a swing in mood. Eleven of seventeen students manifested a hypomanic state without any actual dilatation of personality, that is merely a state of elation. The remaining six students exhibited a tendency toward depression. Reduced ability to form new and original associations was noted. The Rorschach test has sobstantiaced the results obtained by objective observation and by the "retention and recall" test in that every individual follows his inherent pattern. Anoxia nsereiy exposes and aggravates the pre-existing tendency.
Variations in the oxygen concentration of the inspired air, beyond that to which the individual is accustomed, result in marked changes in mental functioning. This disturbance in mental functioning takes place in normal and psychoneurotic subjects exposed to inhalation of low oxygen atmospheres, and also in patients with previously existing anoxia exposed to high oxygen atmospheres. In the present study, observation of 17 medical students who breathed an atmosphere of 13 per cent oxygen (corresponding to an altitude of 12,400 feet) for three hours revealed marked changes in affective behavior, with impairment of emotional control, in 59 per cent elation and flightiness, terminating in lethargy, and in 41 per cent mental dullness from the beginning. The "retention and recall" test in 15 of the 17 students showed a larger incidence of errors and impaired memory after exposure to 13 per cent oxygen for 3 hours.
The patients after inhalation of the low oxygen mixture revealed an even more marked lack of emotional restraint, with feelings of exaggerated self-esteem and sexual pre-occupations. Their mood ultimately changed from that resembling a hypomanic state to dullness and lethargy. Those patients (4 of 9) who did not show elation at the start were dull and lethargic from the beginning. The number of errors in the "retention and recall" test showed considerable variation before and after exposure to inhalation of 13 per cent oxygen, in of 9 patients being better in the low oxygen atmosphere. The greater degree of relaxation which the low oxygen atmosphere induced appeared to free thens from their usual preoccupations, and make for a superficially better intellectual performance. However, in respect to insight, judgment and control of emotions, more marked impairment was uniformly present than in the studeist group.
The results of inhalation of 13 per cent oxygen (corresponding to an altitude of 12,400 feet) reveal especially that an emotional release, with diminished reason, memory and judgment, follows exposure to moderate oxygen deficiency for a three hour period, both in psychoneurotic patients and in normal individuals.
The inhalation of high oxygen atmospheres to patients with previously existing chronic anoxia may also produce a profound disturbance in mental functioning. Irrationality, stupor and delirium may take place within three hours exposure to 50 per cent oxygen. When these patients become acclimatized to their increased oxygen tension, the mental disturbance disappears, frequently with the appearance of a cheerful and optimistic mental state.