Thermodilution-determined Internal Jugular Venous Flow

• Autores: Peter Rasmussen, MATTHIAS P. HILTY, MARIO WIDMER
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 49, Nº. 4, 2017, págs. 661-668
• Idioma: inglés
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• Resumen

  • Purpose: Cerebral blood flow (CBF) increases ~20% during whole body exercise although a Kety–Schmidt–determined CBF is reported to remain stable; a discrepancy that could reflect evaluation of arterial vs. internal jugular venous (IJV) flow and/or that CBF is influenced by posture. Here we test the hypothesis that IJV flow, as determined by retrograde thermodilution increases during exercise when body position is maintained.

    Methods: Introducing retrograde thermodilution, IJV flow was measured in eight healthy humans at supine and upright rest and during exercise in normoxia and hypoxia with results compared with changes in ultrasound-derived IJV flow and middle cerebral artery mean velocity (MCA Vmean).

    Results: Thermodilution determined IJV flow was in reasonable agreement with values established in a phantom (R2 = 0.59, P < 0.0001) and correlated to the ultrasound-derived IJV flow (n = 7; Kendall τ, 0.28; P = 0.036). When subjects stood up, IJV blood flow decreased by 9% ± 13% (mean ± SD) (219 ± 57 to 191 ± 73 mL·min−1; P < 0.0001) and the influence of body position was maintained during exercise (P < 0.0001). Exercise increased both IJV flow and MCA Vmean (P = 0.019 and P = 0.012, respectively) and the two responses were similar (P = 0.50). During hypoxia, however, only MCA Vmean responded with a further increase (P < 0.0001).

    Conclusions: As determined by retrograde thermodilution, IJV flow seems little sensitive to hypoxia, but does demonstrate the about 15% reduction in CBF when humans are upright and, provided that body position is maintained, also the increase in CBF during whole body exercise.