Quantification of the effects of vasomotion on mass transport to tissue from axisymmetric blood vessels

Abstract

International audienceThe process known as vasomotion, rhythmic oscillations in vessel diameter, has been proposed to act as a protective mechanism for tissue under conditions of reduced perfusion, since it is frequently only observed experimentally when perfusion levels are reduced. This could be due to a resultant increase in oxygen transport from the vasculature to the surrounding tissue, either directly or indirectly. It is thus potentially of significant clinical interest as a warning signal for ischemia. However, there has been little analysis performed to quantify the effects of vessel wall movement on time-averaged mass transport. We thus present a detailed analysis of such mass transport for an axisymmetric vessel with a periodically oscillating wall, by solving the non-linear mass transport equation, and quantify the differences between the time-averaged mass transport under conditions of no oscillation (i.e. the steady-state) and varying wall oscillation amplitude. The results show that if the vessel wall alone is oscillated, with an invariant wall concentration, the time-averaged mass transport is reduced relative to the steady-state, but if the vessel wall concentration is also oscillated, then mass transport is increased, although this is generally only true when these oscillate in phase with each other. The influence of Péclet number and the non-dimensional rate of consumption of oxygen in tissue, as well as the amplitude of oscillations, are fully characterised. We conclude by considering the likely implications of these results in the context of oxygen transport to tissue

Vasomotion – what is currently thought?

“…Mathematical modelling supports the importance of vasomotion for oxygen delivery (Ohta et al. 1988, Tsai & Intaglietta 1993, Goldman & Popel 2001, Pradhan & Chakravarthy 2007, Hapuarachchi et al. 2010) and suggests that its activity can change oxygen delivery to tissues by up to eightfold (Kislukhin 2010) although more recent analysis indicates a more complex role of vasomotion.…”

“…In one study (Goldman & Popel 2001), vasomotion only enhanced oxygen delivery in the skeletal muscle bed when myoglobin was low. In another modelling approach, where the physical movement of the arteriolar wall was included in the model, less oxygen delivery by the arterioles exhibiting vasomotion was found and it was suggested that this might lead to high oxygen tension and possibly enhanced delivery by the capillaries (Hapuarachchi et al. 2010).…”

Skin microvascular vasomotion is synchronous at acupoints of beagle dogs

“…The blood perfusion has been demonstrated to be higher at acupoints and on certain parts of meridians [5,23]. Although the physiological role of microvascular vasomotion remains unclear, it has been shown to enhance blood ow and nutrient delivery [9,24]. The synchronous vasomotion suggested that the majority of skin microvessels at acupoints worked as a whole, which would release more energy than an irregular one.…”

Synchronous vasomotion of skin microvessels at acupoints on the twelve main meridians of beagle dogs

“…5,20 Although the physiological role of microvascular vasomotion remains unclear, it has been shown to enhance blood flow and nutrient delivery. 6,21 The synchronous vasomotion suggested that the majority of skin microvessels at acupoints worked as a whole, which would release more energy than an irregular one. More energy and higher blood perfusion should be able to meet the needs of Qi and blood infusion.…”