AltitudeOmics: effect of ascent and acclimatization to 5260 m on regional cerebral oxygen delivery

Subudhi, Andrew W.; Fan, Jui‐Lin; Evero, Oghenero; Bourdillon, Nicolas; Kayser, Bengt; Julian, Colleen G.; Lovering, Andrew T.; Roach, Robert C.

doi:10.1113/expphysiol.2013.075184

Cited by 53 publications

(80 citation statements)

References 47 publications

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“…In particular, the NIRS data are very difficult to interpret due to the few measurements available but might indicate increased blood flow and reduced cerebral tissue saturation when acutely exposed to high altitude and reduced cerebral blood volume (flow) with preserved cerebral tissue oxygenation after acclimatization. These conjectures are at least partly in line with study findings from Subudhi et al (2014) and Sanborn et al (2014). Subudhi and colleagues demonstrated that cerebral blood flow increased when acutely exposed to high altitude and decreased after 16 days at altitudes between 3800 and 5260 m (Chacaltaya Research Station, Bolivia).…”

Section: Resultssupporting

confidence: 81%

Effects of Pre-acclimatization Applying the ‘‘Climb High and Sleep Low’’ Maxim: An Example of Rapid but Safe Ascent to Extreme Altitude

Burtscher¹,

Koch²

2016

Journal of Human Performance in Extreme Environments

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Pre-acclimatization at a convenient high-altitude location may represent an appropriate method before climbing a more hostile target mountain. The aim of the present field report was to demonstrate the effectiveness of such pre-acclimatizing applying the ''climb high sleep low'' maxim for a subsequent rapid ascent to almost 7000 m. After some pre-acclimatization in the Alps the authors flew to Chile for further pre-acclimatization in the Aymara village of Putre (3650 m). From there they undertook sojourns up to altitudes of 5700 m within 3 days. Subsequently they went back to Arica (sea level) and climbed Ojos del Salado (6893 m) within 5 days without any health problems. Measurements of heart rate and arterial oxygen saturation and of cerebral oxygenation by near infrared spectroscopy at rest and during exercise indicated adequate acclimatization status. This field report demonstrates highly effective pre-acclimatization by the ''climb high and sleep low'' strategy supporting anecdotal reports. The up and down strategy may likely have induced hypoxia (pre)conditioning and subsequently allowed rapid ascent to extreme altitudes without any complications. The duration of the carry-over effect after pre-acclimatization has to be evaluated and proposed physiological mechanisms have to be proved by controlled studies in larger samples.

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Section: Resultssupporting

confidence: 81%

Effects of Pre-acclimatization Applying the ‘‘Climb High and Sleep Low’’ Maxim: An Example of Rapid but Safe Ascent to Extreme Altitude

Burtscher¹,

Koch²

2016

Journal of Human Performance in Extreme Environments

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“…During clamp the identical duration and changes in arterial blood gases were replicated while the subjects breathed. 5,260 m. 10,11,27 Conversely, sea level sensitivity to isocapnic or poikilocapnic hypoxia is greater in the VA. 7,12 Euoxic hypocapnia also elicits greater decreases in VA flow through a broad range of PaCO 2 (~15 to 40 mm Hg); 7 however, this is not a universal finding through smaller changes in PCO 2 . 28 It thus seems that during simultaneous changes in PaO 2 and PaCO 2 , ICA and VA reactivities are similar, as was the case in the present study where ICA and VA showed similar profiles during clamp and apnea.…”

Section: Regulation Of Cerebral Blood Flow During Apneamentioning

confidence: 97%

Regulation of Brain Blood Flow and Oxygen Delivery in Elite Breath-Hold Divers

Willie

Ainslie

Drviš

et al. 2014

J Cereb Blood Flow Metab

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The roles of involuntary breathing movements (IBMs) and cerebral oxygen delivery in the tolerance to extreme hypoxemia displayed by elite breath-hold divers are unknown. Cerebral blood flow (CBF), arterial blood gases (ABGs), and cardiorespiratory metrics were measured during maximum dry apneas in elite breath-hold divers (n = 17). To isolate the effects of apnea and IBM from the concurrent changes on ABG, end-tidal forcing ('clamp') was then used to replicate an identical temporal pattern of decreasing arterial PO 2 (PaO 2 ) and increasing arterial PCO 2 (PaCO 2 ) while breathing. End-apnea PaO 2 ranged from 23 to 37 mm Hg (30 ± 7 mm Hg). Elevation in mean arterial pressure was greater during apnea than during clamp reaching +54 ± 24% versus 34 ± 26%, respectively; however, CBF increased similarly between apnea and clamp (93.6 ± 28% and 83.4 ± 38%, respectively). This latter observation indicates that during the overall apnea period IBM per se do not augment CBF and that the brain remains sufficiently protected against hypertension. Termination of apnea was not determined by reduced cerebral oxygen delivery; despite 40% to 50% reductions in arterial oxygen content, oxygen delivery was maintained by commensurately increased CBF.

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“…altitude chamber studies revealed that the CBF velocity measured in the middle cerebral artery is substantially unchanged compared to sea-level value, and, moreover, with no clear relationship to symptoms of AMS, at least in the first few hours of simulated altitude (Baumgartner et al, 1999;Subudhi et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…The general consensus is that upon acute exposure to altitude CBF initially rises and returns to near baseline values within the first few days or 1 -2 weeks of acclimatization (Huang et al, 1987;Jensen et al, 1990;Baumgartner et al, 1994;Lucas et al, 2011;Subudhi et al, 2014). The magnitude in the changes in CBF after altitude exposure depend upon two stimuli with opposing influences on the cerebral circulation: arterial hypoxia and arterial hypocapnia.…”

Section: Discussionmentioning

confidence: 99%

Relationship between Changes in Cerebral Blood Flow with Symptoms of Acute Mountain Sickness in Men Repeatedly Exposed to Simulated High Altitude

Ondrus¹,

Alberty²,

Lyons³

et al. 2017

APE

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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 pCO 2 (ETCO 2 ) and arterial oxygen saturation (SaO 2 ) 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 ETCO 2 (mean ± SD 32 ± 4 mmHg; r = 0.47, P < 0.05), and a weak negative correlation of MCAv with a similar low SaO 2 (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 sympHow to cite this paper: Ondruš, P., Alberty, R., Lyons, T., Muza, S., Echavé, V. 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.

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AltitudeOmics: effect of ascent and acclimatization to 5260 m on regional cerebral oxygen delivery

Cited by 53 publications

References 47 publications

Effects of Pre-acclimatization Applying the ‘‘Climb High and Sleep Low’’ Maxim: An Example of Rapid but Safe Ascent to Extreme Altitude

Effects of Pre-acclimatization Applying the ‘‘Climb High and Sleep Low’’ Maxim: An Example of Rapid but Safe Ascent to Extreme Altitude

Regulation of Brain Blood Flow and Oxygen Delivery in Elite Breath-Hold Divers

Relationship between Changes in Cerebral Blood Flow with Symptoms of Acute Mountain Sickness in Men Repeatedly Exposed to Simulated High Altitude

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