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European Journal of Applied Physiology

, Volume 112, Issue 10, pp 3619–3627 | Cite as

G tolerance vis-à-vis pressure-distension and pressure-flow relationships of leg arteries

  • Ola EikenEmail author
  • Igor Mekjavic
  • Patrik Sundblad
  • Roger Kölegård
Original Article

Abstract

During increased gravitoinertial (G) load in the head-to-foot direction, pressures in dependent vascular beds are commonly raised to levels capable of distending precapillary vessels, which, in turn, may reduce arterial pressure, and hence compromise the capacity to withstand G load (G tolerance). We hypothesized that distensibility in precapillary leg vessels would be lower in a group of subjects possessing high G tolerance (H; n = 7; relaxed G tolerance = 6.6 ± 0.8 G) than in a group with low G tolerance (L; n = 8; G tolerance = 3.9 ± 0.3 G). The groups were matched with regard to gender, age, weight, height, and resting arterial pressure. Arterial pressure-distension and pressure-flow experiments were performed with the subject supine in a pressure chamber with a lower leg protruding to the outside. Increased intravascular pressure in the blood vessels of the outside leg was accomplished by stepwise increasing chamber pressure to 240 mmHg. Diameter and flow in the posterior tibial artery were measured by ultrasonographic/Doppler techniques. Pressure-induced increments in arterial diameter and flow were more pronounced (p < 0.03) in the L (14.1 ± 4.2% and 32 ± 21 ml/min respectively) than in the H (1.7 ± 5.0% and 1.6 ± 25 ml/min) group, and the pressure thresholds at which these increments commenced were lower (by 52 and 48 mmHg, respectively) in the L than in the H group (p < 0.04). Negative correlations were observed between G tolerance and the increments in diameter and flow (p < 0.02). Thus, the wall stiffness of precapillary leg vessels is greater in individuals with high relaxed G tolerance; whether a causal relationship exists remains to be established.

Keywords

Acceleration Arterial stiffness Distensibility G-level tolerance Precapillary vessels Total peripheral resistance 

Notes

Acknowledgments

This study was supported by grants from the Swedish Armed Forces and the Gösta Fraenekel Foundation.

Conflict of interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Ola Eiken
    • 1
    Email author
  • Igor Mekjavic
    • 2
  • Patrik Sundblad
    • 1
  • Roger Kölegård
    • 1
  1. 1.Department of Environmental Physiology, School of Technology and HealthRoyal Institute of TechnologyStockholmSweden
  2. 2.Department of Automation Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia

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