Cerebral Hemodynamics at Altitude: Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation

Matthew R. Sanborn; Mark E. Edsell; Meeri N. Kim; Rickson Mesquita; Mary E. Putt; Chris Imray; Heng Yow; Mark H. Wilson; Arjun G. Yodh; Mike Grocott; Daniel S. Martin

doi:10.1016/j.wem.2014.10.001

Cerebral Hemodynamics at Altitude: Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation

Matthew R. Sanborn^*, Mark E. Edsell, Meeri N. Kim, Rickson Mesquita, Mary E. Putt, Chris Imray, Heng Yow, Mark H. Wilson, Arjun G. Yodh, Mike Grocott, Daniel S. Martin

^*Corresponding author for this work

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Abstract

Objective Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy. Methods Peripheral (Spo₂) and cerebral (Scto₂) oxygenation, end-tidal carbon dioxide (ETCO₂), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO₂ by 50%, and a further set of measurements were obtained. Results Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto₂ from 68.8% to 63.5%; P <.001), increased after hyperventilation after 2 days at altitude (Scto₂ from 65.6% to 69.9%; P =.001), and did not change after hyperventilation after 7 days at altitude (Scto₂ from 62.2% to 63.3%; P =.35). Conclusions An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.

Original language	English
Article number	553
Pages (from-to)	133-141
Number of pages	9
Journal	Wilderness and Environmental Medicine
Volume	26
Issue number	2
DOIs	https://doi.org/10.1016/j.wem.2014.10.001
Publication status	Published - 1 Jun 2015

Bibliographical note

Funding Information:
Unrestricted grant support was provided by Deltex Medical and Smiths Medical. Mike Grocott leads the Xtreme-Everest oxygen research consortium which has received unrestricted grant funding from BOC Medical (Linde Group), Ely-Lilly Critical Care, Smiths Medical, Deltex Medical, London Clinic, and Rolex. All funds were paid directly to the home institutions of researchers within the consortium. Mike Grocott has also received honoraria for speaking (not related to this review) and/or travel expenses from Baxter, Fresenius-Kabi, BOC Medical (Linde Group), and Ely-Lilly Critical Care.

Funding Information:
Funding for this project came from The Wilderness Medical Society Hultgren Grant and American Alpine Club Research Grants to Dr Sanborn and for biostatistical support through NICHD P30 HD026979 .

Publisher Copyright:
© 2015 Wilderness Medical Society.

Keywords

altitude
cerebral oxygenation
Key words hypoxia

ASJC Scopus subject areas

Emergency Medicine
Public Health, Environmental and Occupational Health

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.wem.2014.10.001

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Sanborn, M. R., Edsell, M. E., Kim, M. N., Mesquita, R., Putt, M. E., Imray, C., Yow, H., Wilson, M. H., Yodh, A. G., Grocott, M., & Martin, D. S. (2015). Cerebral Hemodynamics at Altitude: Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation. Wilderness and Environmental Medicine, 26(2), 133-141. Article 553. https://doi.org/10.1016/j.wem.2014.10.001

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title = "Cerebral Hemodynamics at Altitude: Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation",

abstract = "Objective Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy. Methods Peripheral (Spo2) and cerebral (Scto2) oxygenation, end-tidal carbon dioxide (ETCO2), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO2 by 50%, and a further set of measurements were obtained. Results Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto2 from 68.8% to 63.5%; P <.001), increased after hyperventilation after 2 days at altitude (Scto2 from 65.6% to 69.9%; P =.001), and did not change after hyperventilation after 7 days at altitude (Scto2 from 62.2% to 63.3%; P =.35). Conclusions An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.",

keywords = "altitude, cerebral oxygenation, Key words hypoxia",

author = "Sanborn, {Matthew R.} and Edsell, {Mark E.} and Kim, {Meeri N.} and Rickson Mesquita and Putt, {Mary E.} and Chris Imray and Heng Yow and Wilson, {Mark H.} and Yodh, {Arjun G.} and Mike Grocott and Martin, {Daniel S.}",

note = "Funding Information: Unrestricted grant support was provided by Deltex Medical and Smiths Medical. Mike Grocott leads the Xtreme-Everest oxygen research consortium which has received unrestricted grant funding from BOC Medical (Linde Group), Ely-Lilly Critical Care, Smiths Medical, Deltex Medical, London Clinic, and Rolex. All funds were paid directly to the home institutions of researchers within the consortium. Mike Grocott has also received honoraria for speaking (not related to this review) and/or travel expenses from Baxter, Fresenius-Kabi, BOC Medical (Linde Group), and Ely-Lilly Critical Care. Funding Information: Funding for this project came from The Wilderness Medical Society Hultgren Grant and American Alpine Club Research Grants to Dr Sanborn and for biostatistical support through NICHD P30 HD026979 . Publisher Copyright: {\textcopyright} 2015 Wilderness Medical Society.",

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doi = "10.1016/j.wem.2014.10.001",

language = "English",

volume = "26",

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T1 - Cerebral Hemodynamics at Altitude

T2 - Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation

AU - Sanborn, Matthew R.

AU - Edsell, Mark E.

AU - Kim, Meeri N.

AU - Mesquita, Rickson

AU - Putt, Mary E.

AU - Imray, Chris

AU - Yow, Heng

AU - Wilson, Mark H.

AU - Yodh, Arjun G.

AU - Grocott, Mike

AU - Martin, Daniel S.

N1 - Funding Information: Unrestricted grant support was provided by Deltex Medical and Smiths Medical. Mike Grocott leads the Xtreme-Everest oxygen research consortium which has received unrestricted grant funding from BOC Medical (Linde Group), Ely-Lilly Critical Care, Smiths Medical, Deltex Medical, London Clinic, and Rolex. All funds were paid directly to the home institutions of researchers within the consortium. Mike Grocott has also received honoraria for speaking (not related to this review) and/or travel expenses from Baxter, Fresenius-Kabi, BOC Medical (Linde Group), and Ely-Lilly Critical Care. Funding Information: Funding for this project came from The Wilderness Medical Society Hultgren Grant and American Alpine Club Research Grants to Dr Sanborn and for biostatistical support through NICHD P30 HD026979 . Publisher Copyright: © 2015 Wilderness Medical Society.

PY - 2015/6/1

Y1 - 2015/6/1

N2 - Objective Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy. Methods Peripheral (Spo2) and cerebral (Scto2) oxygenation, end-tidal carbon dioxide (ETCO2), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO2 by 50%, and a further set of measurements were obtained. Results Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto2 from 68.8% to 63.5%; P <.001), increased after hyperventilation after 2 days at altitude (Scto2 from 65.6% to 69.9%; P =.001), and did not change after hyperventilation after 7 days at altitude (Scto2 from 62.2% to 63.3%; P =.35). Conclusions An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.

AB - Objective Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy. Methods Peripheral (Spo2) and cerebral (Scto2) oxygenation, end-tidal carbon dioxide (ETCO2), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO2 by 50%, and a further set of measurements were obtained. Results Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto2 from 68.8% to 63.5%; P <.001), increased after hyperventilation after 2 days at altitude (Scto2 from 65.6% to 69.9%; P =.001), and did not change after hyperventilation after 7 days at altitude (Scto2 from 62.2% to 63.3%; P =.35). Conclusions An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.

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KW - Key words hypoxia

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ER -

Cerebral Hemodynamics at Altitude: Effects of Hyperventilation and Acclimatization on Cerebral Blood Flow and Oxygenation

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

UN SDGs

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