Mapping of oxygen saturation in murine lung during intravital microscopy

Abstract

To investigate the distribution of oxygen in the pulmonary microcirculation in vivo, we developed a murine model of pulmonary intravital microscopy combined with multispectral imaging of hemoglobin saturation (SO2). A circular window(D 7‐10μm) was surgically excised from the right thoracic wall for microscopic access to the surface of the upper right lobe of the lung. Removal of intrathoracic air via a transdiaphragmal intrapleural catheter coupled the lung surface to the window membrane. An intravital microscope was modified for epiillumination by a light guide from a monochromatizing device (Till Photonics). Mice were ventilated at 60 breath/min and images were acquired during the expiratory plateau phases. Stacks of images at preselected wavelength ranges and exposure times were analyzed with a dedicated software (SO2 Analysis Program, SOAP) to obtain 2D SO2 images of the observed area. On SO2 images, arterioles, venules and capillaries could be distinguished clearly. Results show an increase in oxygen saturation from 70% to 100% during the passage from arterioles to capillaries over a vessel length of about 200μm.