Objective: To study the relationship between changes in the cerebral blood flow (CBF) velocity with symptoms of acute mountain sickness (AMS) during simulated high altitude. Research Design and Methods: Mean middle arterial cerebral flow velocity (MCAv) was assessed by transcranial Doppler sonography in 8 healthy lowland male adults aged 20 - 24 yrs before and after 6 h and 48 h at simulated altitude corresponding to 4572 m. The same study was repeated three weeks later in the same subjects. End-tidal pCO2 (ETCO2) and arterial oxygen saturation (SaO2) were measured by standardized procedures. AMS symptoms were recorded using the modified environmental symptoms questionnaire after 6 h and 48 h exposure to calculate the mean score of cerebral (AMS-C) symptoms. Results: Mean MCAv significantly increased with high altitude (HA) by 4% at 6 h HA and 24% at 48 h HA (P < 0.05) compared to sea-level values. We observed a substantial inter-subject variance in MCAv changes, especially in the first hours upon altitude exposure. Within first 2 days, we found a moderate positive correlation between MCAv with decreased ETCO2 (mean ± SD 32 ± 4 mmHg; r = 0.47, P < 0.05), and a weak negative correlation of MCAv with a similar low SaO2 (77% ± 8%; r = - 0.43, P < 0.05). Five of the 10 original subjects developed symptoms of AMS; however, AMS-C scores decreased (P = 0.08) with increased duration of exposure (6 h HA 0.91 ± 1.09 vs 48 h HA 0.39 ± 0.40). No differences in AMS-C scores were observed when subjects with and without increased MCAv were compared at 6 h HA and 48 h HA. Furthermore, there was no correlation between changes in neither absolute nor relative MCAv and AMS-C scores. Severity of AMS symptoms coincided well with reduction in SaO2 (r = - 0.55, P < 0.05). Conclusion: Our results suggest that there is a lack of relationship between changes in CBF velocity with symptoms of AMS, and that a substantial inter-subject variance exists in the CBF response to high altitude exposure.
References
[1]
Ainslie, P. N., & Subudhi, A. W. (2014). Cerebral Blood Flow at High Altitude. High Altitude Medicine & Biology, 15, 133-140. https://doi.org/10.1089/ham.2013.1138
[2]
Atkinson, J. L., Anderson, R. E., & Sundt, T. J. (1990). The Effect of Carbon Dioxide on the Diameter of Brain Capillaries. Brain Research, 517, 333-340. https://doi.org/10.1016/0006-8993(90)91046-J
[3]
Baumgartner, R. W., Bartsch, P., Maggiorini, M., Waber, U., & Oelz, O. (1994). Enhanced Cerebral Blood Flow in Acute Mountain Sickness. Aviation, Space, and Environmental Medicine, 65, 726-729.
[4]
Baumgartner, R. W., Spyridopoulos, I., Bartsch, P., Maggiorini, M., & Oelz, O. (1999). Acute Mountain Sickness Is Not Related to Cerebral Blood Flow: A Decompression Chamber Study. Journal of Applied Physiology, 86, 1578-1582.
[5]
Bian, S.-Z., Jin, J., Li, Q.-N., Qin, J., Zhang, J.-H., Yu, S.-Y., Chen, J.-F., Tang, C.-F., Huang, L. (2014). Cerebral Hemodynamic Characteristics of Acute Mountain Sickness upon High-Altitude Exposure at 3,700 m in Young Chinese Men. European Journal of Applied Physiology, 114, 2193-2200. https://doi.org/10.1007/s00421-014-2934-6
[6]
Dyer, E. A., Hopkins, S. R., Perthen, J. E., Buxton, R. B., & Dubowitz, D. J. (2008). Regional Cerebral Blood Flow during Acute Hypoxia in Individuals Susceptible to Acute Mountain Sickness. Respiratory Physiology & Neurobiology, 160, 267-276. https://doi.org/10.1016/j.resp.2007.10.010
[7]
Huang, S. V., Moore, L. G., McCullough, R. E., Micco, A. J., Fulco, C., Cymerman, A., Manco-Johnson, M., Weil, J. V., & Reeves, J. T. (1987). Internal Carotid and Vertebral Arterial Flow Velocity in Men at High Altitude. Journal of Applied Physiology, 63, 395-400.
[8]
Hussain, M. M., Aslam, M., & Khan, Z. (2001). Acute Mountain Sickness Score and Hypoxemia. Journal of the Pakistan Medical Association, 51, 173-179.
[9]
Imray, C., Chan, C., Stubbings, A., Rhodes, H., Patey, S., Wilson, M. H., Bailey, D. M., & Wright, A. D. (2014). Time Course Variations in the Mechanisms by Which Cerebral Oxygen Delivery Is Maintained on Exposure to Hypoxia/Altitude. High Altitude Medicine & Biology, 15, 21-27. https://doi.org/10.1089/ham.2013.1079
[10]
Imray, C., Wright, A., Subudhi, A., & Roach, R. (2010). Acute Mountain Sickness: Pathophysiology, Prevention, and Treatment. Progress in Cardiovascular Diseases, 52, 467-484. https://doi.org/10.1016/j.pcad.2010.02.003
[11]
Jensen, J. B., Wright, A. D., Lassen, N. A., Harvey, T. C., Winterborn, M. H., Raichle, M. E., & Bradwell, A. R. (1990). Cerebral Blood Flow in Acute Mountain Sickness. Journal of Applied Physiology, 69, 430-433.
[12]
Lassen, N. A. (1992). Increase of Blood Flow at High Altitude: Its Possible Relation to AMS. International Journal of Sports Medicine, 13, S47-S48. https://doi.org/10.1055/s-2007-1024591
[13]
Lucas, S. J. E., Burgess, K. R., Thomas, K. N., Donnelly, J., Peebles, K. C., Lucas, R. A. I., Fan, J.-L., Cotter, J. D., Basnyat, R., & Ainslie, P. N. (2011). Alterations in Cerebral Blood Flow and Cerebrovascular Reactivity during 14 Days at 5050 m. Journal of Physiology, 589, 741-753. https://doi.org/10.1113/jphysiol.2010.192534
[14]
Mórocz, I. A., Zientara, G. P., Gudbjartsson, H., Muza, S., Lyons, T., Rock, P. B., Kikinis, R., & Jólesz, F. A. (2001). Volumetric Quantification of Brain Swelling after Hypobaric Hypoxia Exposure. Experimental Neurology, 168, 96-104. https://doi.org/10.1006/exnr.2000.7596
[15]
Poulin, M. J., Fatemian, M., Tansley, J. G., O’connor, D. F., & Robbins, P. A. (2002). Changes in Cerebral Blood Flow during and after 48 h of Both Isocapnic and Poikilocapnic Hypoxia in Humans. Experimental Physiology, 87, 633-642. https://doi.org/10.1113/eph8702437
[16]
Sampson, J. B., Cymerman, A., Burse, R. J., Maher, J. T., & Rock, P. N. (1983). Procedures for the Measurement of Acute Mountain Sickness. Aviation, Space, and Environmental Medicine, 54, 1063-1073.
[17]
Subudhi, A. W., Fan, J.-L., Evero, O., Bourdillon, N., Kayser, B., Julian, C. G., Lovering, A. T., & Roach, R. C. (2014). Altitude Omics: Effect of Ascent and Acclimatization to 5260 m on Regional Cerebral Oxygen Delivery. Experimental Physiology, 99, 772-781. https://doi.org/10.1113/expphysiol.2013.075184
[18]
Van Osta, A., Moraine, J. J., Mélot, C., Mairbaurl, H., Maggiorini, M., & Nacije, R. (2005). Effects of High Altitude Exposure on Cerebral Hemodynamics in Normal Subjects. Stroke, 36, 557-560. https://doi.org/10.1161/01.STR.0000155735.85888.13
[19]
West, J. B., Schoene, R. B., Luks, A. M., & Milledge, J. S. (2012). High Altitude Medicine and Physiology (5th ed.). Boca Raton, FL: CRC Press. https://doi.org/10.1201/b13633
[20]
Wilson, M. H., Edsell, M. E., Davagnanam, I., Hirani, S. P., Martin, D. S., Levett, D. Z. H., Thornton, J. S. et al. (2011). Cerebral Artery Dilatation Maintains Cerebral Oxygenation at Extreme Altitude and in Acute Hypoxia—An Ultrasound and MRI Study. Journal of Cerebral Blood Flow & Metabolism, 31, 2019-2029. https://doi.org/10.1038/jcbfm.2011.81
