Dear All, Some references follow regarding mild hypoxia and performance. Some light winter time reading. Aviat Space Environ Med 1985 Oct;56(10):1004-8 The effects of mild hypoxia on a logical reasoning task. Green RG, Morgan DR. In an attempt to replicate the findings of Crow and Kelman (1969) and Denison et al. (1966), which suggest that the performance of novel tasks can be impaired at altitudes below 3,050 m, 150 subjects were divided into five independent groups and their performance tested on a logical reasoning task. One group was tested at ground level in a lecture room; the remaining groups were tested in a decompression chamber, one at 305 m, one at 2,440 m, one at 3,050 m and one at 3,660 m. Significant differences were identified between the 'lecture room' and 'chamber' groups in both speed of work and error rate (p less than 0.05); this finding is interpreted as the effect of apprehension on the naive subjects. A significant difference was found between the group tested at 3660 m and the remaining groups for error rate (p less than 0.05); this finding is interpreted as the effect of apprehension on the naive subjects. A significant difference was found between the group tested at 3660 m and the remaining groups for error rate (p less than 0.05) but not for speed of work. However, no effect of altitude on the way in which the task was learned could be demonstrated. Aviat Space Environ Med 1994 Oct;65(10 Pt 1):891-9 Performance during mild acute hypoxia. Paul MA, Fraser WD. Civil Institute of Environmental Medicine, North York, Ont., Canada. The controversy regarding the effects of mild hypoxia on learning performance needs to be resolved, since this may be affecting flight operations and safety. This study examined the ability to learn new tasks at low altitudes. Naive subjects (n = 144) performed spatial orientation (Manikin), serial choice reaction time (SCRT) and logical reasoning (Baddeley) tasks at ground level and at altitudes of 1,524 m (5,000 ft), 2,438 m (8,000 ft), 3,048 m (10,000 ft), and 3,658 m (12,000 ft), at rest or during exercise (VO2 = 600 ml O2.min-1) in a hypobaric chamber. Each task was performed over four serial repetitions (blocks) and presented at ground level or one of the four test altitudes in a first session, and in the reverse order in a second session. Performance for the Manikin and SCRT tasks improved significantly (p < 0.0001) over the 4 blocks. No significant difference was found between the corresponding 4 blocks of the first session in resting and exercising subjects tested at ground level before altitude compared to altitude before ground level. In general, RT for the 3 tasks were faster in resting than in exercising subjects. These results indicate that the ability to learn new tasks is not impaired by mild hypoxia at altitudes of up to 3,658 m. We detected a biphasic response to altitude in LRT and SCRT performance, but not for Manikin performance. Aviat Space Environ Med 1984 May;55(5):407-10 Mild hypoxia and the use of oxygen in flight. Ernsting J. Hypoxia in aviation remains a major hazard. It may be caused by ascent while breathing air, failure of oxygen supply or loss of cabin pressurisation. Malfunction of equipment or its improper use accounted for the majority of hypoxic incidents in one 10-year military study. Symptoms of hypoxia depend on rate of ascent, temperature, and individual variation, as well as altitude. Dyspnoea, lack of coordination and reduction in capacity for skilled performance precede the gross changes which occur at altitudes of over 4572 m (15,000 ft) and lead ultimately to unconsciousness. Studies have shown a significant decrease in psychomotor task ability at altitudes as low as 2438 m (8000 ft). Developments in aircraft oxygen systems are discussed and the importance of adequate crew instruction on hypoxia and their aircraft oxygen equipment is stressed. Aviat Space Environ Med 1982 Dec;53(12):1207-10 Arterial oxygen saturation at altitude using a nasal cannula. Dixon JP. Oxygen saturation in six subjects wearing a nasal cannula at altitudes of 14,000 ft (4267 m), 20,000 ft (6096 m), 22,500 ft, (6858 m) and 25,000 ft (7620 m) was measured using an ear oximeter (Hewlett-Packard 47201A). Saturation was measured during four activities: at rest breathing through the mouth, at rest breathing through the nose, performing biceps-curls, and talking. Oxygen flow rates of 1.5-2.5 LPM NTPD were used. There was no difference in the saturation levels whether the subject breathed through the nose or through the mouth, and cannula position in the nose was critical to good oxygen saturation. During talking and while exercising, subjects' saturations varied more than during rest conditions, sometimes falling to unacceptable levels. Based upon the lack of hypoxia symptoms and the high levels of oxygen saturation up to 20,000 ft (6096 m), it is concluded that at flow rates of 1.5-2.0 LPM NTPD the nasal cannula can be safely used to maintain adequate oxygenation in healthy individuals in hypobaric chamber operations, aircraft flight, and other operations at altitude. Above 20,000 ft (6096 m), the cannula does not provide sufficient oxygenation for persons to perform these physical activities. Aviat Space Environ Med 1984 Oct;55(10):921-6 Central nervous reactions to a 6.5-hour altitude exposure at 3048 meters. Vaernes RJ, Owe JO, Myking O. In this study of CNS reactions to mild hypoxia, 7 subjects were decompressed to the equivalence of 3048 m altitude breathing air, for 6.5 h. On reaching 3048 m, and for every second h thereafter, a battery of neuropsychological tests were administered. In addition, blood and performance measures were sampled and a symptom check list was administered. The performance tests indicated significant effects of hypoxia. In contrast to earlier studies on grade of hypoxia and performance, no relationship between impaired performance and duration of exposure to hypoxia was found. Repeated testing throughout exposure indicated stable individual reactions. Endocrine variables did not support the hypothesis that activation or 'stress' caused the impairment observed. In addition to impaired neuropsychological test performance and impaired task performance, the subjects reported headache, weakness and some dizziness. Comparisons between different tests confirmed previous results showing that mild hypoxia yields varying degrees of impairment on different cognitive functions. Aviat Space Environ Med 1997 Sep;68(9 Pt 1):807-11 Comparisons of altitude tolerance and hypoxia symptoms between nonsmokers and habitual smokers. Yoneda I, Watanabe Y. Aeromedical Laboratory, Japan Air Self-Defense Force, Tachikawa, Tokyo, Japan. BACKGROUND: Increased levels of carboxyhemoglobin (COHb) in smokers are blamed for inducing pre-hypoxic tendency classified as anemic hypoxia. If COHb can be simply converted to altitude, there should be significant differences between smokers and nonsmokers with respect to hypoxia tolerance. However, the studies of the effects of carbon monoxide and/or smoking habit on the physiological functions at altitude do not have consistent conclusions, and many pilots still have smoking habits. This study was designed to assess whether there is a definite significant difference for time of useful consciousness (TUC), subjective symptoms, or performance degradation between nonsmokers and smokers. METHODS: During the hypoxia experience of routine physiological training, TUC and 12 typical subjective symptoms were examined at the chamber altitude of 25,000 ft (7620 m) in 589 nonsmokers and 582 smokers in Study 1. The time until the deterioration of handwriting was assessed by 6 physiological training observers in 51 nonsmokers and 70 smokers in Study 2. The results were compared between the groups. RESULTS: Smokers revealed significantly fewer subjective symptoms in 5 out of 12 symptoms. There were no significant differences in TUC and the rate of handwriting deterioration between the groups. CONCLUSIONS: Paradoxically, smokers are slightly resistant to hypoxia with respect to emerging subjective symptoms. However, bluntness to hypoxia could postpone the detection of the possible hypoxic occurrence in pilots. -- * You are subscribed to the aus-soaring mailing list. * To Unsubscribe: send email to [EMAIL PROTECTED] * with "unsubscribe aus-soaring" in the body of the message * or with "help" in the body of the message for more information.
