A Micro‐Delivery Approach for Studying Microvascular Responses to Localized Oxygen Delivery

Please cite this paper as: Ghonaim, Lau, Goldman, Ellis, and Yang (2011). A Micro‐delivery Approach for Studying Microvascular Responses to Localized Oxygen Delivery. Microcirculation 18 (8), 646–654. Abstract Background:  In vivo video microscopy has been used to study blood flow regulation as a function of varying oxygen concentration in microcirculatory networks. However, previous studies have measured the collective response of stimulating large areas of the microvascular network at the tissue surface. Objective:  We aimed to limit the area being stimulated by controlling oxygen availability to highly localized regions of the microvascular bed within intact muscle. Design and Method:  Gas of varying O 2 levels was delivered to specific locations on the surface of the Extensor Digitorum Longus muscle of rat through a set of micro‐outlets (100  μ m diameter) patterned in ultrathin glass using state‐of‐the‐art microfabrication techniques. O 2 levels were oscillated and digitized video sequences were processed for changes in capillary hemodynamics and erythrocyte O 2 saturation. Results and Conclusions:  Oxygen saturations in capillaries positioned directly above the micro‐outlets were closely associated with the controlled local O 2 oscillations. Radial diffusion from the micro‐outlet is limited to ∼75  μ m from the center as predicted by computational modeling and as measured in vivo . These results delineate a key step in the design of a novel micro‐delivery device for controlled oxygen delivery to the microvasculature to understand the fundamental mechanisms of microvascular regulation of O 2 supply.