TY - JOUR

T1 - Global REACH 2018: Andean highlanders, chronic mountain sickness and the integrative regulation of resting blood pressure

AU - Simpson, Lydia

AU - Meah, Victoria

AU - Steele, Andrew

AU - Gasho, Christopher

AU - Howe, Connor

AU - Dawkins, Tony

AU - Busch, Stephen

AU - Oliver, Sam

AU - Moralez, Gilberto

AU - Lawley, Justin

AU - Tymko, MIchael

AU - Vizcardo-Galindo, Gustavo Andres

AU - Figueroa-Mujíca , Rómulo Joseph

AU - Villafuerte, Francisco

AU - Ainslie, Philip

AU - Stembridge, Mike

AU - Steinback, Craig

AU - Moore, Jonathan

N1 - Article has been published OnlineOpen (approved by BU LAS staff). This is not currently reflected in the published version. "This article is protected by copyright. All rights reserved" (Checked 29/04/20). Repository Manager has decided to release the accepted version open as it has been published online, is available on the Publisher's website and it will be Online Open (but at some indeterminate future point and it is too much work to continually to check this manually until the Publisher's website is amended).

PY - 2021/1/1

Y1 - 2021/1/1

N2 - High‐altitude maladaptation syndrome chronic mountain sickness (CMS) is characterised by excessive erythrocytosis and frequently accompanied by accentuated arterial hypoxaemia. Whether altered autonomic cardiovascular regulation is apparent in CMS is unclear. Therefore, we assessed integrative control of blood pressure (BP) and determined basal sympathetic vasomotor outflow and arterial baroreflex function in 8 Andean natives with CMS ([Hb] 22.6 ± 0.9 g/dL) and 7 healthy highlanders ([Hb] 19.3 ± 0.8 g/dL) at their resident altitude (Cerro de Pasco, Peru; 4383 m). R‐R interval (RRI, electrocardiogram), beat‐by‐beat BP (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded at rest and during pharmacologically‐induced changes in BP (modified Oxford test). Although [Hb] and blood viscosity (7.8 ± 0.7 vs 6.6 ± 0.7cP; d = 1.7, P = 0.01) were elevated in CMS compared to healthy highlanders, cardiac output, total peripheral resistance and mean BP were similar between groups. The vascular sympathetic baroreflex MSNA set‐point (i.e. MSNA burst incidence) and reflex gain (i.e. responsiveness) were also similar between groups (MSNA set‐point; d = 0.75, P = 0.16, gain; d = 0.2, P = 0.69). In contrast, in CMS the cardiovagal baroreflex operated around a longer RRI (960 ± 159 vs 817 ± 50msec; d = 1.4, P = 0.04) with a greater reflex gain (17.2 ± 6.8 vs 8.8 ± 2.6msec·mmHg−1; d = 1.8, P = 0.01) versus healthy highlanders. Basal sympathetic vasomotor activity was also lower compared to healthy highlanders (33 ± 11 vs 45 ± 13bursts·min−1; d = 1.0, P = 0.08). In conclusion, our findings indicate adaptive differences in basal sympathetic vasomotor activity and heart rate compensate for the haemodynamic consequences of excessive erythrocyte volume and contribute to integrative blood pressure regulation in Andean highlanders with mild CMS.

AB - High‐altitude maladaptation syndrome chronic mountain sickness (CMS) is characterised by excessive erythrocytosis and frequently accompanied by accentuated arterial hypoxaemia. Whether altered autonomic cardiovascular regulation is apparent in CMS is unclear. Therefore, we assessed integrative control of blood pressure (BP) and determined basal sympathetic vasomotor outflow and arterial baroreflex function in 8 Andean natives with CMS ([Hb] 22.6 ± 0.9 g/dL) and 7 healthy highlanders ([Hb] 19.3 ± 0.8 g/dL) at their resident altitude (Cerro de Pasco, Peru; 4383 m). R‐R interval (RRI, electrocardiogram), beat‐by‐beat BP (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded at rest and during pharmacologically‐induced changes in BP (modified Oxford test). Although [Hb] and blood viscosity (7.8 ± 0.7 vs 6.6 ± 0.7cP; d = 1.7, P = 0.01) were elevated in CMS compared to healthy highlanders, cardiac output, total peripheral resistance and mean BP were similar between groups. The vascular sympathetic baroreflex MSNA set‐point (i.e. MSNA burst incidence) and reflex gain (i.e. responsiveness) were also similar between groups (MSNA set‐point; d = 0.75, P = 0.16, gain; d = 0.2, P = 0.69). In contrast, in CMS the cardiovagal baroreflex operated around a longer RRI (960 ± 159 vs 817 ± 50msec; d = 1.4, P = 0.04) with a greater reflex gain (17.2 ± 6.8 vs 8.8 ± 2.6msec·mmHg−1; d = 1.8, P = 0.01) versus healthy highlanders. Basal sympathetic vasomotor activity was also lower compared to healthy highlanders (33 ± 11 vs 45 ± 13bursts·min−1; d = 1.0, P = 0.08). In conclusion, our findings indicate adaptive differences in basal sympathetic vasomotor activity and heart rate compensate for the haemodynamic consequences of excessive erythrocyte volume and contribute to integrative blood pressure regulation in Andean highlanders with mild CMS.

KW - arterial baroreflex

KW - blood pressure control

KW - chronic mountain sickness

KW - excessive erythrocytosis

KW - muscle sympathetic nerve activity

U2 - 10.1113/EP088473

DO - 10.1113/EP088473

M3 - Article

VL - 106

SP - 104

EP - 116

JO - Experimental Physiology

JF - Experimental Physiology

SN - 0958-0670

IS - 1

ER -