High-frequency perfusion fluorometry (HFPF): preliminary results on a new technique for assessing bronchial mucosa...

A new method for estimating airway mucosa blood perfusion is proposed. It is based on the use of a high-sensitivity perfusion fluorometer, which allows us to detect the first intravascular passage of injected fluorochromes. Total measuring time can be sensibly reduced with respect to standard perfusion fluorometry, allowing us to make assessments during fiberoptic bronchoscopy. In vitro studies were performed to set up the optical arrangement of the instrument. The optimal measuring distance (2.2 mm) between the probe tip and the fluorescent mucosa was established using a fluorescent film surface to simulate fluorescent mucosa. The depth of tissue layers involved in the fluorescence emission was assessed by positioning tissue sections of different thickness between the probe tip and the fluorescent film. Tissue layers at depths not exceeding 1200 microns were found to contribute to the fluorescence signal recorded by the instrument. Mucosa blood perfusion was evaluated in rat trachea, as a model, under three different experimental conditions of vascularization: (a) basal condition (BC), (b) partial devascularization (PD), (c) full devascularization (FD). Sodium fluorescein (diffusible into the interstice) and fluorescein isothiocyanate-dextran (not diffusible into the interstice) were used as fluorescent tracers. Under the BC both substances allowed us to detect the first passage of fluorochrome through the mucosa capillary network with the same accuracy. In PD the first pass peak disappeared; total emitted fluorescence decreased as well. In FD a flat tracing was recorded. Consistent results were obtained with both substances.(ABSTRACT TRUNCATED AT 250 WORDS)