Direct Illumination Method To Visualize Pulmonary Vessels

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Abstract
A direct illumination method is described that permits observation of the pulmonary vessels on the external surface of the lung. The preparation requires general anesthesia, endotracheal intubation and open thorax. Artificial ventilation of the lung is recommended to prevent CO2 accumulation and alterations of the pulmonary pressure. CO2 accumulation and rise in the pulmonary pressure are seen in dogs submitted to "still lung" preparations for observation of the pulmonary vessels. Our method utilizes local immobilization of the lung with a round cover glass held in situ with a plastic disc. Illumination is obtained with an incident light illuminator as commercially made for metallurgic microscopes. When photography or cinematographic records are taken, the illuminator is replaced with a larger reflection box, and carbon arc light is used as a source of light. Two groups of guinea pigs have been studied with this method, one maintained at sea level and the other exposed to simulated high altitude. The capillaries lining the air spaces of animals kept at high altitude are longer and wider.