CONDITIONS OF STRESS IN UNDERSEA WARFARE 



421 



an extreme example (53), two subjects were 

 able to maintain EEG stability and good 

 mental contact for two minutes despite a 

 very low O2 supply (2%) in the presence of 

 5% COo. Furthermore, the intermediate 

 stages of increased voltage and decreased 

 frequency in the EEG were greatly reduced. 



Whether one regards changes in blood or 

 in brain as primary in these reactions, it 

 should be remembered that peripheral neuro- 

 physiological events are also taldng place as 

 part of the total organismic response. There 

 is increased sympathetic activity in anoxia 

 with release of adrenaline to play its support- 

 ing role in circulatory changes. Chemore- 

 ceptors in carotid and aortic glomi serve to 

 feed back and affect the nervous system, and 

 pressure receptors in these areas reflexly as- 

 sist in maintenance of heart rate and blood 

 pressure. The effectiveness of the adjust- 

 ments may be furthered by a sitting or re- 

 cHning posture, reduced physical exertion 

 and maintenance of adequate blood sugar 

 (29, 51, 67). This latter has received ex- 

 tensive study, but it is merely mentioned 

 here, since sugar per se is unlikely to be a 

 critical factor in submarine life where food 

 supplies may usually be depended upon to 

 outlast O2 supplies. Suffice it to say that 

 glucose and O2 play mutually supportive 

 roles in brain metabolism and that normal 

 and even supra-normal blood sugar values 

 (130 mg%) may serve to compensate some- 

 what for reduced O2 supply (16, 29, 51, 63). 



In view of the variety of skilled motor 

 tasks, sensory-motor adjustments, and de- 

 cisions involving multiple operations affect- 

 ing the entire submarine, it may be of interest 

 to examine data secured by McFarland (85) 

 with regard to the effects of anoxia on certain 

 psychological tests. It was found that, on 

 the average, there was significant deteriora- 

 tion at 14,000 feet (12% O2) with respect to 

 handwriting, choice reaction time, and ocular 

 muscle balance. More complex tasks such 

 as color naming, a transhteration code test, 

 and a paired associates memory test showed 

 impairment at 10,000 feet (14% O2). There 



was considerable individual variability in all 

 these tests with some individuals showing 

 effects at higher O2 values (cf. 70). Rate 

 of ascent and oxygen deprivation was an 

 important factor, the effect being greater for 

 anoxia of rapid onset. Under extreme con- 

 ditions, of course, the danger of incurring 

 the "bends," as in explosive decompression 

 (67), introduces still another factor. 



The psychological changes that parallel 

 the physiological alterations due to hypoxia 

 are equally important, although somewhat 

 more difficult to detect in the earher stages. 

 With slowly developing anoxemia the 

 changes are characteristically insidious of 

 onset and not readily recognized by the in- 

 dividual. There is usually an initial feehng 

 of well-being, perhaps similar to the effects of 

 mild alcoholic intoxication, with feelings of 

 power and self-satisfaction and decreased 

 critical capacity (3, 16, 48, 85). With pro- 

 gressively greater anoxia there is impair- 

 ment of judgment and emotional instabihty 

 coupled with complaints of frontal headache 

 and shortness of breath (58). Loss of critical 

 capacity combined with muscular incoor- 

 dination and general irritability may result 

 in rough handling of equipment or an in- 

 ability to carry out procedures necessary for 

 safety and survival of the crew. There may 

 be a fixity of ideas and perseveration of 

 (sometimes erroneous) responses. There is 

 both sensory and motor loss, particularly of 

 visual functions, and impairment of memory. 

 With severe or prolonged anoxia there may 

 be nausea and vomiting, extreme Aveakness 

 and eventually convulsions and cardiac syn- 

 cope. In the terminal stages of anoxic anox- 

 emia, blood pressure, heart rate and cir- 

 culatory responses are extremely variable. 

 Relationships between susceptibility to low 

 O2 and the presence of various "psycho- 

 neurotic" traits provides some basis for the 

 use of low oxygen in various screening pro- 

 cedures to be mentioned later (30). 



Some of the anoxic effects on sensory sys- 

 tems may be of particular interest to the 

 submariner because of the importance of 



