Peripheral arterial vascular function at altitude:... : Journal of Hypertension (original) (raw)

Original papers: Blood vessels

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

Schneider, Annetteb; Greene, Richard E.c; Keyl, Corneliusb; Bandinelli, Gabrieled; Passino, Claudioa; Spadacini, Giammarioa; Bonfichi, Maurizioa; Arcaini, Lucaa; Malcovati, Lucaa; Boiardi, Amerigoe; Feil, Paulc; Bernardi, Lucianoa

aDepartment of Internal Medicine and Institute of Hematology, University of Pavia and Istituto di Ricovero e Cura a Carattere Scientifico S. Matteo, Pavia, Italy, bDepartment of Anesthesiology, University Medical Centre Regensburg, University of Regensburg, Germany, cDepartment of Bioengineering, New Mexico Highlands University, Las Vegas, New Mexico, dOspedale Santa Maria Nuova, Florence, Italy and eIstituto di Ricovero e Cura a Carattere Scientifico Besta, Milan, Italy.

Received 14 January 2000

Revised 22 September 2000

Accepted 6 October 2000

Sponsorship: The study was performed during an expedition to the Pyramid Laboratory in Nepal which was supported by CNR, CONI, IRCCS Policlinica San Matteo, Università di Pavia.

Correspondence and requests for reprints to Annette Schneider, Department of Anesthesiology, University Medical Centre Regensburg, University of Regensburg, 93042 Regensburg, Germany. Fax: +49 941944 7802

Abstract

Objectives

Regulation of the vascular system may limit physical performance and contribute to adaptation to high altitude. We evaluated vascular function in 10 Himalayan high-altitude natives and 10 recently acclimatized sea-level natives at an altitude of 5050 m.

Methods

We registered electrocardiogram, blood flow velocity in the common femoral artery, and blood pressure in the radial artery using non-invasive methods under baseline conditions, and during maximal vasodilation after 2 min leg occlusion. Vascular mechanics were characterized by estimating pulse wave velocity and input impedance.

Results

Pulse wave velocity and parameters of input impedance did not differ between groups under baseline conditions. In the post-ischemic period, the ratio between maximal hyperemic and baseline blood flow velocity was significantly higher in the high-altitude than in the sea-level natives (5.7 ± 2.5 versus 3.8 ± 1.2, P < 0.05). The leg vascular resistance decreased in the post-occlusive period without differences between groups. Characteristic impedance decreased in the post-ischemic period by about one third of the baseline level without differences between groups. The post-ischemic decrease of input impedance modulus was more marked in the high-altitude than in the sea-level natives at low frequencies (28 ± 12 versus 6.4 ± 20% at 2 Hz, P < 0.01).

Conclusions

Our results demonstrate a superior ability to increase blood flow velocity as a response to muscular ischemia in high-altitude natives compared to sea-level natives. This phenomenon may be associated with a more effective coupling between blood pressure and blood flow which is probably caused by differences in conduit vessel function.