Peripheral arterial vascular function at altitude: sea-level natives versus Himalayan high-altitude natives

1.To assess the effects of acute exposure to high altitude on baroreceptor function in man we evaluated the effects of baroreceptor activation on R–R interval and blood pressure control at high altitude. We measured the low-frequency (LF) and high-frequency (HF) components in R–R, non-invasive blood pressure and skin blood flow, and the effect of baroreceptor modulation by 0.1-Hz sinusoidal neck suction. Ten healthy sea-level natives and three high-altitude native, long-term sea-level residents were evaluated at sea level, upon arrival at 4970 ;m and 1 week later. 2.Compared with sea level, acute high altitude decreased R–R and increased blood pressure in all subjects [sea-level natives: R–R from 1002±45 to 775±57 ;ms, systolic blood pressure from 130±3 to 150±8 ;mmHg; high-altitude natives: R–R from 809±116 to 749±47 ;ms, systolic blood pressure from 110±12 to 125±11 ;mmHg (P< 0.05 for all)]. One week later systolic blood pressure was similar to values at sea level in all subjects, whereas R–R remained elevated in sea-level natives. The low-frequency power in R–R and systolic blood pressure increased in sea-level natives [R–R-LF from 47±8 to 65±10% (P< 0.05), systolic blood pressure-LF from 1.7±0.3 to 2.6±0.4 ln-mmHg2 (P< 0.05)], but not in high-altitude natives (R–R-LF from 32±13 to 38±19%, systolic blood pressure-LF from 1.9±0.5 to 1.7±0.8 ln-mmHg2). The R–R-HF decreased in sea-level natives but not in high-altitude natives, and no changes occurred in systolic blood pressure-HF. These changes remained evident 1 week later. Skin blood flow variability and its spectral components decreased markedly at high altitude in sea-level natives but showed no changes in high-altitude natives. Neck suction significantly increased the R–R- and systolic blood pressure-LF in all subjects at both sea level and high altitude. 3.High altitude induces sympathetic activation in sea-level natives which is partially counteracted by active baroreflex. Despite long-term acclimatization at sea level, high-altitude natives also maintain active baroreflex at high altitude but with lower sympathetic activation, indicating a persisting high-altitude adaptation which may be genetic or due to baroreflex activity not completely lost by at least 1 year's sea-level residence.

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Training in hypoxia vs. training in normoxia in high-altitude natives

Journal of Applied Physiology ◽

10.1152/jappl.1995.78.6.2286 ◽

1995 ◽

Vol 78 (6) ◽

pp. 2286-2293 ◽

Cited By ~ 22

Author(s):

R. Favier ◽

H. Spielvogel ◽

D. Desplanches ◽

G. Ferretti ◽

B. Kayser ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Maximal Exercise ◽

Work Intensity ◽

Maximal Aerobic Capacity ◽

Trained Subjects ◽

Arterial Ph ◽

High Altitude Natives ◽

Blood Lactate Accumulation ◽

O2 Delivery

To determine the interactions between endurance training and hypoxia on maximal exercise performance, we performed a study on sedentary high-altitude natives who were trained in normoxia at the same relative (n = 10) or at the same absolute (n = 10) intensity of work as hypoxia-trained subjects (n = 10). The training-induced improvement of maximal oxygen uptake (VO2max) in hypoxia-trained subjects was similar to that obtained in normoxia-trained sea-level natives submitted to the same training protocol (H. Hoppeler, H. Howald, K. Conley, S. L. Lindstedt, H. Claassen, P. Vock, and E. W. Weibel. J. Appl. Physiol. 59: 320–327, 1985). Training at the same absolute work intensity in the presence of increased oxygen delivery failed to provide a further increase in VO2max. VO2max was not improved to a greater extent by simultaneously increasing absolute work intensity and O2 delivery during the training sessions. In addition, training in normoxia is accompanied by an increased blood lactate accumulation during maximal exercise, leading to greater drops in arterial pH, bicarbonate concentration, and base excess. We conclude that, in high-altitude natives, 1) training at altitude does not provide any advantage over training at sea level for maximal aerobic capacity, whether assessed in chronic hypoxia or in acute normoxia; 2) VO2max improvement with training cannot be further enhanced by increasing O2 availability alone or in combination with an increased work intensity during the exercising sessions; and 3) training in normoxia in these subjects results in a reduced buffer capacity.

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Ventilatory Response to Acute Hypoxia in Sea Level Natives and in High Altitude Natives*

Acta Physiologica Scandinavica ◽

10.1111/j.1365-201x.1971.tb10952.x ◽

1971 ◽

Vol 81 (S361) ◽

pp. 26-32

Keyword(s):

High Altitude ◽

Sea Level ◽

Ventilatory Response ◽

Acute Hypoxia ◽

High Altitude Natives

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Selected Contribution: Acute and sustained ventilatory responses to hypoxia in high-altitude natives living at sea level

Journal of Applied Physiology ◽

10.1152/japplphysiol.00856.2002 ◽

2003 ◽

Vol 94 (3) ◽

pp. 1255-1262 ◽

Cited By ~ 26

Author(s):

Alfredo Gamboa ◽

Fabiola León-Velarde ◽

Maria Rivera-Ch ◽

Jose-Antonio Palacios ◽

Timothy R. Pragnell ◽

...

Keyword(s):

Confidence Interval ◽

High Altitude ◽

Sea Level ◽

Hypoxic Exposure ◽

Ventilatory Responses ◽

High Altitude Natives ◽

Ventilatory Depression ◽

End Tidal ◽

Sustained Hypoxia

High-altitude (HA) natives have blunted ventilatory responses to hypoxia (HVR), but studies differ as to whether this blunting is lost when HA natives migrate to live at sea level (SL), possibly because HVR has been assessed with different durations of hypoxic exposure (acute vs. sustained). To investigate this, 50 HA natives (>3,500 m, for >20 yr) now resident at SL were compared with 50 SL natives as controls. Isocapnic HVR was assessed by using two protocols: protocol 1, progressive stepwise induction of hypoxia over 5–6 min; and protocol 2, sustained (20-min) hypoxia (end-tidal Po 2 = 50 Torr). Acute HVR was assessed from both protocols, and sustained HVR from protocol 2. For HA natives, acute HVR was 79% [95% confidence interval (CI): 52–106%, P = not significant] of SL controls for protocol 1 and 74% (95% CI: 52–96%, P < 0.05) for protocol 2. By contrast, sustained HVR after 20-min hypoxia was only 30% (95% CI: −7–67%, P < 0.001) of SL control values. The persistent blunting of HVR of HA natives resident at SL is substantially less to acute than to sustained hypoxia, when hypoxic ventilatory depression can develop.

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Alveolar P CO 2 and P O 2 of high-altitude natives living at sea level

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.4.1605 ◽

1996 ◽

Vol 81 (4) ◽

pp. 1605-1609 ◽

Cited By ~ 11

Author(s):

Fabiola León-Velarde ◽

Manuel Vargas ◽

Carlos Monge-C. ◽

Robert W. Torrance ◽

Peter A. Robbins

Keyword(s):

Confidence Interval ◽

High Altitude ◽

Sea Level ◽

Average Difference ◽

Control Subjects ◽

High Altitude Natives ◽

End Tidal

León-Velarde, Fabiola, Manuel Vargas, Carlos Monge-C., Robert W. Torrance, and Peter A. Robbins. Alveolar[Formula: see text] and[Formula: see text] of high-altitude natives living at sea level. J. Appl. Physiol. 81(4): 1605–1609, 1996.—This study was designed to determine whether subjects born at high altitude (HA; 2,000 m or above) who subsequently move to near sea level (SL) develop end-tidal [Formula: see text]([Formula: see text]) and[Formula: see text]([Formula: see text]) values that equal those of SL natives living near SL. A total of 108 male HA natives living near SL were identified by survey of a district in Lima, Peru, and a further 108 male SL natives from the same district were identified as control subjects. Of these subjects, satisfactory data for inclusion in the study were obtained from 93 HA and 82 SL subjects. Mean [Formula: see text] and[Formula: see text] values were 37.7 ± 2.5 (SD) and 104.7 ± 3.2 Torr, respectively, in HA subjects and 37.7 ± 2.2 and 104.8 ± 3.0 Torr, respectively, in SL subjects. The average difference between SL natives and HA natives for[Formula: see text] was 0.07 Torr (−0.64 to 0.78; 95% confidence interval) and for[Formula: see text] was 0.05 Torr (−0.89 to 0.99, 95% confidence interval). The average age and weight of the SL and HA subjects did not differ, but the HA subjects were shorter and tended to have larger vital capacities, consistent with their origin at HA. We conclude that the[Formula: see text] and[Formula: see text] near SL of SL natives and HA natives do not differ.

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Carbonic anhydrase activity in the red blood cells of sea level and high altitude natives

Biological Research ◽

10.4067/s0716-97602000000300006 ◽

2000 ◽

Vol 33 (3-4) ◽

Cited By ~ 3

Author(s):

JORGE GAMBOA ◽

RICARDO CACEDA ◽

ALFREDO GAMBOA ◽

CARLOS MONGE-C

Keyword(s):

Carbonic Anhydrase ◽

Red Blood Cells ◽

High Altitude ◽

Sea Level ◽

Blood Cells ◽

Carbonic Anhydrase Activity ◽

High Altitude Natives

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Prediction of High-Altitude Cardiorespiratory Fitness Impairment Using a Combination of Physiological Parameters During Exercise at Sea Level and Genetic Information in an Integrated Risk Model

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.719776 ◽

2022 ◽

Vol 8 ◽

Author(s):

Jie Yang ◽

Hu Tan ◽

Mengjia Sun ◽

Renzheng Chen ◽

Jihang Zhang ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Cardiorespiratory Fitness ◽

Genetic Information ◽

Vascular Function ◽

Cardiovascular Events ◽

Risk Model ◽

Submaximal Exercise ◽

Physiological Parameters ◽

Combination Model

Insufficient cardiorespiratory compensation is closely associated with acute hypoxic symptoms and high-altitude (HA) cardiovascular events. To avoid such adverse events, predicting HA cardiorespiratory fitness impairment (HA-CRFi) is clinically important. However, to date, there is insufficient information regarding the prediction of HA-CRFi. In this study, we aimed to formulate a protocol to predict individuals at risk of HA-CRFi. We recruited 246 volunteers who were transported to Lhasa (HA, 3,700 m) from Chengdu (the sea level [SL], <500 m) through an airplane. Physiological parameters at rest and during post-submaximal exercise, as well as cardiorespiratory fitness at HA and SL, were measured. Logistic regression and receiver operating characteristic (ROC) curve analyses were employed to predict HA-CRFi. We analyzed 66 pulmonary vascular function and hypoxia-inducible factor- (HIF-) related polymorphisms associated with HA-CRFi. To increase the prediction accuracy, we used a combination model including physiological parameters and genetic information to predict HA-CRFi. The oxygen saturation (SpO2) of post-submaximal exercise at SL and EPAS1 rs13419896-A and EGLN1 rs508618-G variants were associated with HA-CRFi (SpO2, area under the curve (AUC) = 0.736, cutoff = 95.5%, p < 0.001; EPAS1 A and EGLN1 G, odds ratio [OR] = 12.02, 95% CI = 4.84–29.85, p < 0.001). A combination model including the two risk factors—post-submaximal exercise SpO2 at SL of <95.5% and the presence of EPAS1 rs13419896-A and EGLN1 rs508618-G variants—was significantly more effective and accurate in predicting HA-CRFi (OR = 19.62, 95% CI = 6.42–59.94, p < 0.001). Our study employed a combination of genetic information and the physiological parameters of post-submaximal exercise at SL to predict HA-CRFi. Based on the optimized prediction model, our findings could identify individuals at a high risk of HA-CRFi in an early stage and reduce cardiovascular events.

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Tolerance to acute anoxia in high altitude natives

Journal of Applied Physiology ◽

10.1152/jappl.1959.14.3.357 ◽

1959 ◽

Vol 14 (3) ◽

pp. 357-362 ◽

Cited By ~ 9

Author(s):

Tulio Velásquez

Keyword(s):

High Altitude ◽

Sea Level ◽

Technical Assistance ◽

Acute Hypoxia ◽

Low Pressure ◽

Pressure Chamber ◽

Relative Influence ◽

Acute Anoxia ◽

High Altitude Natives

Native residents living at an altitude of 14,900 feet were suddenly exposed to simulated higher altitudes, ranging from 30 to 40,000 feet, in a low pressure chamber. The ‘time of consciousness’ and the ceiling breathing air were determined. In addition, observations were made on the respiratory characteristics at these altitudes. Comparing the results with those given by previous investigators using sea level residents, they indicate that a man born and living at an altitude of 14,900 feet has a definitely greater tolerance to acute hypoxia than a man born and residing at sea level. The relative influence of hypoxia and hypocapnia on the symptoms which developed during this test is discussed. Note: (With the Technical Assistance of Edgard Florentini and Melquiades Huayna-Vera) Submitted on June 2, 1958

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