Cardiovascular autonomic modulation and activity of carotid baroreceptors at altitude

Bernardi, Luciano; Passino, Claudio; Spadacini, Giammario; Calciati, A; Robergs, Robert A.; Greene, Richard A.; Martignoni, E.; Anand, Inder; Appenzeller, Otto

doi:10.1042/cs0950565

Cited by 95 publications

(118 citation statements)

References 21 publications

(46 reference statements)

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“…Increased sympathetic activity is a part of the integrated physiological response to a hypoxic stimulus (10,31). In the present study, we observed, in association with acute hypobaric hypoxia, an increase in heart rate, a reduction in R-R variability, and a relative increase of LF RR NU in asymptomatic subjects, consistent with a sympathetic predominance in the neural inputs to the heart and in agreement with previous studies conducted at high altitude (2,12,13). Little is known about the effect of AMS on the autonomic cardiovascular regulation.…”

Section: Cardiovascular Variability and Amssupporting

confidence: 81%

“…The LF-to-HF ratio was also considered. The LF component of the SBP variability (LF SBP) was used to estimate the sympathetic influence on the vascular system (2,23). Cross-spectral analysis of R-R interval and respiratory signals allowed exclusion of those components of the R-R spectrum in the LF band coherent with the respiratory signal.…”

Section: Discussionmentioning

confidence: 99%

“…Although the HF rhythm primarily reflects the respirationdriven vagal modulation of sinus rhythm (32a), the nonrespiratory LF rhythm appears to have a widespread neural genesis (26) and, in normalized units (NU), apparently mainly reflects the sympathetic modulation of the heart (23, 26, 32a), as well as the baroreflex responsiveness to the beat-to-beat variations in arterial blood pressure (BP) (30). During exposure to high altitude, R-R variability is reduced with a relative increase in the LF component (2,12,13), suggesting an increased sympathetic modulation of the sinus node in response to hypobaric hypoxia. Little is known about whether this pattern is influenced and/or modified by AMS.…”

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confidence: 99%

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Autonomic cardiovascular regulation in subjects with acute mountain sickness

Lanfranchi¹,

Colombo²,

Cremona³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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The aims of this study were 1) to evaluate whether subjects suffering from acute mountain sickness (AMS) during exposure to high altitude have signs of autonomic dysfunction and 2) to verify whether autonomic variables at low altitude may identify subjects who are prone to develop AMS. Forty-one mountaineers were studied at 4,559-m altitude. AMS was diagnosed using the Lake Louise score, and autonomic cardiovascular function was explored using spectral analysis of R-R interval and blood pressure (BP) variability on 10-min resting recordings. Seventeen subjects (41%) had AMS. Subjects with AMS were older than those without AMS (P Ͻ 0.01). At high altitude, the lowfrequency (LF) component of systolic BP variability (LFSBP) was higher (P ϭ 0.02) and the LF component of R-R variability in normalized units (LFRRNU) was lower (P ϭ 0.001) in subjects with AMS. After 3 mo, 21 subjects (43% with AMS) repeated the evaluation at low altitude at rest and in response to a hypoxic gas mixture. LFRRNU was similar in the two groups at baseline and during hypoxia at low altitude but increased only in subjects without AMS at high altitude (P Ͻ 0.001) and did not change between low and high altitude in subjects with AMS. Conversely, LFSBP increased significantly during short-term hypoxia only in subjects with AMS, who also had higher resting BP (P Ͻ 0.05) than those without AMS. Autonomic cardiovascular dysfunction accompanies AMS. Marked LFSBP response to short-term hypoxia identifies AMS-prone subjects, supporting the potential role of an exaggerated individual chemoreflex vasoconstrictive response to hypoxia in the genesis of AMS.hypoxia; autonomic nervous system; heart rate; blood pressure ACUTE MOUNTAIN SICKNESS (AMS) is a complex syndrome characterized by headache, gastrointestinal symptoms, weakness, insomnia, and certain neurological signs, including ataxia and changes in mental status (1). It may occur in subjects ascending to Ͼ2,500 m and is reported in 53% of those at Ͼ4,000-m altitude (6,22).AMS is generally harmless and transient but may occasionally progress to the more serious life-threatening cerebral and pulmonary forms of mountain sickness, i.e., high-altitude cerebral and pulmonary edema (1, 6).The exact mechanism causing AMS is unknown, although the prevailing hypothesis points to a process within the central nervous system (1), possibly an altered adaptation to the neurohumoral and hemodynamic adjustments during hypoxia (8). A marked increase in peripheral sympathetic activity is a common feature of mountain sickness (4, 11) and has also been suggested to contribute to the genesis of high-altitude pulmonary edema (4). Whether autonomic hyperactivation may play a role in the genesis of AMS is not known.The autonomic nervous system plays a role in the modulation of the oscillatory behavior of the cardiovascular system (23, 32a). Spectral analysis of variability in the R-R interval is a recognized tool that allows quantification of the oscillatory components, which in short-term recordings appear mainly organized...

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Section: Cardiovascular Variability and Amssupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Autonomic cardiovascular regulation in subjects with acute mountain sickness

Lanfranchi¹,

Colombo²,

Cremona³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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“…Characteristic changes elicited by altitude, as a consequence of the lower arterial pO 2 , are hyperventilation, resulting in respiratory alkalosis, 6 and increases in heart rate and arterial blood pressure. 7 One of the changes observed in relation to hypoxia is an increase in oxidative stress damage. 8 It has been suggested that this phenomenon is due, at least in part, to recurrent conditions of ischemia-reperfusion, which could cause cell damage and induce signaling for apoptotic pathways.…”

Section: Introductionmentioning

confidence: 99%

Cardiorespiratory parameters during submaximal exercise under acute exposure to normobaric and hypobaric hypoxia

Basualto-Alarcón

Rodas

Galilea

et al. 2012

Apunts. Medicina de l'Esport

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Seven healthy young men were submitted twice to a hypoxia tolerance test at a simulated altitude (3000 m). Their first acute exposure was in a hypobaric chamber; and the second, in a hypoxic tent. Cardiorespiratory parameters and heart rate variability measurements were obtained under each hypoxic condition. A significant decrease of 6% to 8% compared to normal oxygen conditions was observed in arterial oxygen saturation (SpO 2 ) in both hypoxic conditions at rest; whereas exercise led to decreases of 10% in SpO 2 despite an increase of 27% in respiratory minute volume. The low frequency (LF) and high frequency (HF) components of heart rate variability significantly changed from normoxia (LF: 37.1, HF: 62.9, LF/HF: 1.27) to hypobaric hypoxia (HH) (LF: 49.1, HF: 50.6, LF/HF: 1.96). However, these changes were not observed under normobaric hypoxia. Thus, heart rate variability behaved differently in the two hypoxic conditions, supporting the hypothesis that normobaric hypoxia and hypobaric hypoxia are not equal stimuli to the cardiovascular and respiratory systems. A correlation was found between sympathetic and vagal modulations in normoxia and SpO 2 at exercise under hypobaric hypoxia (HH). Individuals with higher sympathetic modulation (LF%) in normoxia had higher SpO 2 at exercise under HH (r = 0.808, P < 0.05) and individuals with higher vagal modulation (HF%) in normoxia showed a trend to lower SpO 2 in exercise under HH (r = −0.636, P = 0.125). This opens up the possibility of using this correlation as a tool for predicting the individual capacity to altitude acclimatization. © 2011 Consell Català de l'Esport. Generalitat de Catalunya. Published by Elsevier España, S.L. All rights reserved. * Corresponding author. E-mail address: gviscor@ub.edu (G. Viscor). PALABRAS CLAVEVariabilidad de la frecuencia cardiaca; Prueba de tolerancia a hipoxia; Tienda hipóxica; Cámara hipobárica; Saturación arterial de oxígeno Parámetros cardiorrespiratorios durante ejercicio submáximo en hipoxia aguda hipobárica y normobáricaResumen Siete jóvenes sanos y en buena condición física realizaron dos pruebas de tolerancia a hipoxia a una altitud simulada de 3.000 m. La primera fue en cámara hipobárica, mientras que la segunda se efectuó en una tienda hipóxica. Se registraron varios parámetros cardiorrespiratorios y la variabilidad de la frecuencia cardiaca. En comparación con las condiciones de normoxia, se observó un decremento significativo del 6% al 8% en la saturación de oxígeno arterial (SpO 2 ) en reposo en ambas condiciones de hipoxia. El ejercicio desencadenó descensos de un 10% en SpO 2 pese a un incremento del 27% del volumen minuto ventilatorio. Tanto los componentes de baja (LF) como alta frecuencia (HF) de la variabilidad del ritmo cardiaco cambiaron significativamente en hipoxia hipobárica (LF: 49,1, HF: 50,6, LF/HF: 1,96) respecto a normoxia (LF: 37,1, HF: 62,9, LF/HF: 1,27). Estos cambios no se apreciaron en condiciones de hipoxia normobárica, lo cual apoya la hipótesis de que la hipoxia hipobárica y norm...

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“…Some investigators have found an increase in BP [1][2][3][4][5] , others a slight reduction [6][7] , and others no change at all 8,9 . The tendency observed in most of the studies, however, is an increase in blood pressure levels on the first day of exposure to a significant altitude and, later, a decline of the values to those found at sea level, mainly in regard to the systolic blood pressure (SBP) 3,5 .…”

Section: Acute Responses To Hypobaric Hypoxia Cardiopulmonary Effectsmentioning

confidence: 99%

Physical activity at moderate and high altitudes. Cardiovascular and respiratory morbidit

Campos¹,

Costa²

1999

Arq. Bras. Cardiol.

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Cardiovascular autonomic modulation and activity of carotid baroreceptors at altitude

Cited by 95 publications

References 21 publications

Autonomic cardiovascular regulation in subjects with acute mountain sickness

Autonomic cardiovascular regulation in subjects with acute mountain sickness

Cardiorespiratory parameters during submaximal exercise under acute exposure to normobaric and hypobaric hypoxia

Physical activity at moderate and high altitudes. Cardiovascular and respiratory morbidit

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