In vivo observation of tracheal microcirculation in dogs.

Tracheal microcirculation was studied in six healthy anesthetized adult mongrel dogs. A transparent balloon was used to apply pressure to the tracheal mucosa during observation of the microcirculation. Pressures of microvascular occlusion were measured using an electrically callibrated silicone, envelope placed on the observation balloon. The different vessel sizes were measured and classified using the operating microscope. Capillary occlusion pressures ranged from 10 to 40 msurements of tracheal diameter were performed. Progressive local and generalized dilatation occurred. Capillary occlusion pressure was lower in the more dilated specimens. The lower than expected occlusion pressures are thought to be a result of the tracheal dilatation and may be related to the administration of drugs or other factors.