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--============_-1272276420==_ma============ Content-Type: text/plain; charset="us-ascii" Someone asked about narcosis studies, here is a quick list from Medline, I hope this isn't too long. I'll let the refs speak for themselves, anyone still up for deep air.... Mike : Undersea Hyperb Med 1995 Mar;22(1):41-9 Dissociation of the behavioral and subjective components of nitrogen narcosis and diver adaptation. Hamilton K, Laliberte MF, Fowler B Defence and Civil Institute of Environmental Medicine, North York, Ontario, Canada. Study of adaption to narcosis, conclusions "We investigated adaptation to nitrogen narcosis by compressing 11 highly experienced divers in a hyperbaric chamber to the equivalent of 54.6 meters of seawater once a day for 5 consecutive days. The behavioral component of narcosis was assessed with a serial choice-reaction time (RT) task, and the subjective component with a global magnitude estimate. Supplementary magnitude estimates were obtained with adjectives describing work effectiveness and body sensations. The results showed that there was no adaptation on the RT task, although learning was evident.... These results lead to the conclusion that the anecdotal reports of adaptation by divers can probably be attributed to the subjective rather than the behavioral component of narcosis. " PMID: 7742709, UI: 95261249 : Aviat Space Environ Med 1992 Oct;63(10):865-9 Subjective and behavioral effects associated with repeated exposure to narcosis. Hamilton K, Laliberte MF, Heslegrave R Human Factors Division, Defence and Civil Institute of Environmental Medicine, North York, Ont., Canada. "...[narcosis] decrease[s] during repeated exposure to hyperbaric air without parallel improvement on task performance. To examine this possibility, symptoms and performance were examined over the course of 5 days of repeated exposure to 30% nitrous oxide at 1 ATA. While the results revealed no clear cut changes in global perceptions of narcosis across days, several symptoms from an adjective checklist showed unequivocal signs of adaptation. With respect to performance effects, reaction time yielded no indications of improvement over days relative to the control. These findings suggest that subjective adaptation can occur without parallel performance improvement, an effect which could compromise safety and which may be of concern in other operational settings that involve repeated exposure to stimulus conditions which impact on performance and symptoms. Undersea Biomed Res 1991 Jan;18(1):1-19 Effects of CO2 and N2 partial pressures on cognitive and psychomotor performance. Fothergill DM, Hedges D, Morrison JB School of Kinesiology, Simon Fraser University, Burnaby B.C., Canada. This study examined N2 and CO2 components of narcosis by comparing the effects of three levels of PETCO2 at 1 and 6 atm abs in 12 male volunteers. Cognitive and psychomotor performances were examined using a variety of tasks, including a modified Stroop test, an arithmetic test, number comparison, a figure copying test, and the Purdue pegboard test. Performance on all tasks demonstrated significant (P less than 0.05) decrements at 6 atm abs. High CO2 tensions significantly impaired cognitive and psychomotor performance at 1 atm abs and caused further decrements at 6 atm abs (P less than 0.05). However, no significant N2-CO2 interaction (P greater than 0.05) or global threshold for the onset of CO2 narcosis was indicated by the test scores. The pattern of intratest results were different for N2 and CO2. At high PETCO2, performance deficits were due to a slowing of performance rather than a disruption of the accuracy of processing. Nitrogen narcosis, conversely, produced significant impairment through both decreases in the speed and accuracy of processing on the majority of performance tests. It was concluded that within the PETCO2 ranges studied: a) PETCO2 and PIN2 are additive in their effects on impaired cognitive and psychomotor performance at depth; b) high PETCO2 and PIN2 induce distinctly different strategic responses on the speed accuracy trade-off function of the performance tests; c) decrements in cognitive and psychomotor performance under high PETCO2 do not conform to the predicted narcotic potency of CO2 according to the lipid solubility theory of narcosis. PMID: 1902340, UI: 91213341 Sci China [B] 1989 Dec;32(12):1436-48 The influence of N2-O2 and He-O2 saturation diving on electroencephalogram of human bodies. Shi ZY, Zhao DM, Mei XH, Liu ZR, Shen TM Chinese Underwater Technology Institute, Shanghai, PRC. various EEG changes under pressure, exaggerated with N2 compared with He.... Sci China [B] 1989 Dec;32(12):1436-48 The influence of N2-O2 and He-O2 saturation diving on electroencephalogram of human bodies. Shi ZY, Zhao DM, Mei XH, Liu ZR, Shen TM Chinese Underwater Technology Institute, Shanghai, PRC. This paper reports the changes of the EEG of human bodies during saturation exposure at different depths to different mixed gases. The results of the research show that the most obvious on EEG was the appearance of diffused slow waves, usually theta waves of 4-7 times/s, and delta waves of 2-3 times/s within individual subjects. The EEG changes at 50 m were more obvious than those at 36.5 m. With the prolonging of time under high pressure, the EEG had some improvements, for instance, the slow waves decreased and the alpha waves increased. There was a certain relationship between these changes and the symptoms which appeared in the human body. The chief factor of the EEG changes is due to the effect of nitrogen narcosis during the oxygen-nitrogen diving experiment. In addition, carbon dioxide retention under the high pressure is also a factor of the EEG changes, because repeated inhaling of CO2-dense mixtures could aggravate the EEG changes and the reduction of carbon dioxide in humans by hyperventilation could improve abnormal EEGs. 1 : Neurochem Res 1998 Jul;23(7):997-1003 Neurochemical studies of narcosis: a comparison between the effects of nitrous oxide and hyperbaric nitrogen on the dopaminergic nigro-striatal pathway. Turle N, Saget A, Zouani B, Risso JJ Department of Neurochemistry, I. M. N. S. S. A., Toulon Naval, France. Inert gas narcosis is a neurological syndrome inducing several psychomotor disorders. Nitrogen narcosis represents the major cause of performances decrease concerning divers, in the depth range of 30 to 90 meters (0.3 to 0.9 MegaPascal). ...[motor region in rat brains]....The first emergence of Dopamine and metabolites variations occurs around 40% of N2O. Dopamine decreases by 45% and is accompanied by a DOPAC diminution of 7% while HVA concentrations remain constant. Under 60% N2O, these decrease have a greater amplitude. The Dopamine variations obtained under 0.9 Mpa of Nitrox are close to alterations induced by 60% of N2O (DA decreases by 70%). : J Appl Physiol 1995 Jun;78(6):2241-4 Nitrogen narcosis attenuates shivering thermogenesis. Mekjavic IB, Savic SA, Eiken O School of Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada. Thermoregulatory responses of eight healthy subjects (six men and two women) were compared when they were head-out immersed in 15 degrees C water at both 1 and 6 ATA. Both trials were conducted in a hyperbaric chamber. During the immersions, esophageal temperature (T(es)) and skin temperature at two sites (chest and calf) were recorded at minute intervals. Oxygen uptake was determined at 5-min intervals with the Douglas bag method. The order of the two trials was alternated. The rate of T(es) cooling was greater during the 6-ATA trial [2.1 +/- 0.5 degrees C/h (SE)] than during the 1-ATA trial (1.3 +/- 0.5 degrees C/h; P < 0.01). Despite the greater rate of core cooling, and presumably a greater thermal drive for shivering, the oxygen uptake response for a similar decrement in T(es) was lower during exposure to 6 than to 1 ATA (P < 0.05). Also, for similar displacement in T(es), the subjects perceived the immersions at 6 ATA to be less cold than those at 1 ATA (P < 0.05). It is concluded that the development of hypothermia in compressed-air divers may be due, in large part, to the attenuation of heat production and cold perception. Most likely, the observed effects on the autonomic responses and thermal perception are due to an inhibitory action of hyperbaric nitrogen on central neural structures involved in temperature regulation. PMID: 7665424, UI: 95394735 1 : Undersea Biomed Res 1985 Dec;12(4):369-402 Effects of inert gas narcosis on behavior--a critical review. Fowler B, Ackles KN, Porlier G : Undersea Biomed Res 1980 Mar;7(1):35-46 Narcotic effects of nitrous oxide and compressed air on memory and auditory perception. Fowler B, White PL, Wright GR, Ackles KN Michael Maibaum mike@ma*.or* 20 Hanover Court Uxbridge Rd London W12 9EP 020 8 743 3668 --============_-1272276420==_ma============ Content-Type: text/enriched; charset="us-ascii" Someone asked about narcosis studies, here is a quick list from Medline, I hope this isn't too long. I'll let the refs speak for themselves, anyone still up for deep air.... Mike <fontfamily><param>Palatino</param><bigger>: Undersea Hyperb Med 1995 Mar;22(1):41-9 Dissociation of the behavioral and subjective components of nitrogen narcosis and diver adaptation. Hamilton K, Laliberte MF, Fowler B Defence and Civil Institute of Environmental Medicine, North York, Ontario, Canada. Study of adaption to narcosis, conclusions "We investigated adaptation to nitrogen narcosis by compressing 11 highly experienced divers in a hyperbaric chamber to the equivalent of 54.6 meters of seawater once a day for 5 consecutive days. The behavioral component of narcosis was assessed with a serial choice-reaction time (RT) task, and the subjective component with a global magnitude estimate. Supplementary magnitude estimates were obtained with adjectives describing work effectiveness and body sensations. The results showed that there was no adaptation on the RT task, although learning was evident.... These results lead to the conclusion that the anecdotal reports of adaptation by divers can probably be attributed to the subjective rather than the behavioral component of narcosis. " PMID: 7742709, UI: 95261249 : Aviat Space Environ Med 1992 Oct;63(10):865-9 Subjective and behavioral effects associated with repeated exposure to narcosis. Hamilton K, Laliberte MF, Heslegrave R Human Factors Division, Defence and Civil Institute of Environmental Medicine, North York, Ont., Canada. "...[narcosis] decrease[s] during repeated exposure to hyperbaric air without parallel improvement on task performance. To examine this possibility, symptoms and performance were examined over the course of 5 days of repeated exposure to 30% nitrous oxide at 1 ATA. While the results revealed no clear cut changes in global perceptions of narcosis across days, several symptoms from an adjective checklist showed unequivocal signs of adaptation. With respect to performance effects, reaction time yielded no indications of improvement over days relative to the control. These findings suggest that subjective adaptation can occur without parallel performance improvement, an effect which could compromise safety and which may be of concern in other operational settings that involve repeated exposure to stimulus conditions which impact on performance and symptoms. Undersea Biomed Res 1991 Jan;18(1):1-19 Effects of CO2 and N2 partial pressures on cognitive and psychomotor performance. Fothergill DM, Hedges D, Morrison JB School of Kinesiology, Simon Fraser University, Burnaby B.C., Canada. This study examined N2 and CO2 components of narcosis by comparing the effects of three levels of PETCO2 at 1 and 6 atm abs in 12 male volunteers. Cognitive and psychomotor performances were examined using a variety of tasks, including a modified Stroop test, an arithmetic test, number comparison, a figure copying test, and the Purdue pegboard test. Performance on all tasks demonstrated significant (P less than 0.05) decrements at 6 atm abs. High CO2 tensions significantly impaired cognitive and psychomotor performance at 1 atm abs and caused further decrements at 6 atm abs (P less than 0.05). However, no significant N2-CO2 interaction (P greater than 0.05) or global threshold for the onset of CO2 narcosis was indicated by the test scores. The pattern of intratest results were different for N2 and CO2. At high PETCO2, performance deficits were due to a slowing of performance rather than a disruption of the accuracy of processing. Nitrogen narcosis, conversely, produced significant impairment through both decreases in the speed and accuracy of processing on the majority of performance tests. It was concluded that within the PETCO2 ranges studied: a) PETCO2 and PIN2 are additive in their effects on impaired cognitive and psychomotor performance at depth; b) high PETCO2 and PIN2 induce distinctly different strategic responses on the speed accuracy trade-off function of the performance tests; c) decrements in cognitive and psychomotor performance under high PETCO2 do not conform to the predicted narcotic potency of CO2 according to the lipid solubility theory of narcosis. PMID: 1902340, UI: 91213341 Sci China [B] 1989 Dec;32(12):1436-48 The influence of N2-O2 and He-O2 saturation diving on electroencephalogram of human bodies. Shi ZY, Zhao DM, Mei XH, Liu ZR, Shen TM Chinese Underwater Technology Institute, Shanghai, PRC. various EEG changes under pressure, exaggerated with N2 compared with He.... Sci China [B] 1989 Dec;32(12):1436-48 The influence of N2-O2 and He-O2 saturation diving on electroencephalogram of human bodies. Shi ZY, Zhao DM, Mei XH, Liu ZR, Shen TM Chinese Underwater Technology Institute, Shanghai, PRC. This paper reports the changes of the EEG of human bodies during saturation exposure at different depths to different mixed gases. The results of the research show that the most obvious on EEG was the appearance of diffused slow waves, usually theta waves of 4-7 times/s, and delta waves of 2-3 times/s within individual subjects. The EEG changes at 50 m were more obvious than those at 36.5 m. With the prolonging of time under high pressure, the EEG had some improvements, for instance, the slow waves decreased and the alpha waves increased. There was a certain relationship between these changes and the symptoms which appeared in the human body. The chief factor of the EEG changes is due to the effect of nitrogen narcosis during the oxygen-nitrogen diving experiment. In addition, carbon dioxide retention under the high pressure is also a factor of the EEG changes, because repeated inhaling of CO2-dense mixtures could aggravate the EEG changes and the reduction of carbon dioxide in humans by hyperventilation could improve abnormal EEGs. 1 : Neurochem Res 1998 Jul;23(7):997-1003 Neurochemical studies of narcosis: a comparison between the effects of nitrous oxide and hyperbaric nitrogen on the dopaminergic nigro-striatal pathway. Turle N, Saget A, Zouani B, Risso JJ Department of Neurochemistry, I. M. N. S. S. A., Toulon Naval, France. Inert gas narcosis is a neurological syndrome inducing several psychomotor disorders. Nitrogen narcosis represents the major cause of performances decrease concerning divers, in the depth range of 30 to 90 meters (0.3 to 0.9 MegaPascal). ...[motor region in rat brains]....The first emergence of Dopamine and metabolites variations occurs around 40% of N2O. Dopamine decreases by 45% and is accompanied by a DOPAC diminution of 7% while HVA concentrations remain constant. Under 60% N2O, these decrease have a greater amplitude. The Dopamine variations obtained under 0.9 Mpa of Nitrox are close to alterations induced by 60% of N2O (DA decreases by 70%). : J Appl Physiol 1995 Jun;78(6):2241-4 Nitrogen narcosis attenuates shivering thermogenesis. Mekjavic IB, Savic SA, Eiken O School of Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada. Thermoregulatory responses of eight healthy subjects (six men and two women) were compared when they were head-out immersed in 15 degrees C water at both 1 and 6 ATA. Both trials were conducted in a hyperbaric chamber. During the immersions, esophageal temperature (T(es)) and skin temperature at two sites (chest and calf) were recorded at minute intervals. Oxygen uptake was determined at 5-min intervals with the Douglas bag method. The order of the two trials was alternated. The rate of T(es) cooling was greater during the 6-ATA trial [2.1 +/- 0.5 degrees C/h (SE)] than during the 1-ATA trial (1.3 +/- 0.5 degrees C/h; P << 0.01). Despite the greater rate of core cooling, and presumably a greater thermal drive for shivering, the oxygen uptake response for a similar decrement in T(es) was lower during exposure to 6 than to 1 ATA (P << 0.05). Also, for similar displacement in T(es), the subjects perceived the immersions at 6 ATA to be less cold than those at 1 ATA (P << 0.05). It is concluded that the development of hypothermia in compressed-air divers may be due, in large part, to the attenuation of heat production and cold perception. Most likely, the observed effects on the autonomic responses and thermal perception are due to an inhibitory action of hyperbaric nitrogen on central neural structures involved in temperature regulation. PMID: 7665424, UI: 95394735 1 : Undersea Biomed Res 1985 Dec;12(4):369-402 Effects of inert gas narcosis on behavior--a critical review. Fowler B, Ackles KN, Porlier G : Undersea Biomed Res 1980 Mar;7(1):35-46 Narcotic effects of nitrous oxide and compressed air on memory and auditory perception. Fowler B, White PL, Wright GR, Ackles KN </bigger></fontfamily> Michael Maibaum mike@ma*.or* 20 Hanover Court Uxbridge Rd London W12 9EP 020 8 743 3668 --============_-1272276420==_ma============-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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