Effects of vehicle type, time and concentration on the distribution of nebulized fluorescein throughout the respiratory tract in healthy racing pigeons (Columbia livia domestica)

Abstract

Fungal infections are commonly seen in birds. Most research has been performed on nebulization of water soluble vehicles, while anti-mycotics are usually not water soluble. In this study the distribution of fluorescein labeled propylene glycol or saline in 3 different concentrations (5, 20 or 80 mg/mL) across the respiratory tract (nasal cavity, trachea, caudal air sacs, lungs and cranial air sacs) was compared in 60 healthy racing pigeons. In addition, these solvents were either nebulized for either 0.5 or 4 h. Directly following nebulization, birds were euthanized followed by post mortem examination during which the distribution of the fluorescent particles throughout the different parts of the respiratory tract was visualized using UV-light and subsequently photographed. Distribution and staining intensity were subsequently scored by two independent examiners blinded for the treatment using the latter photographs. Fluorescein dissolved in saline was found to result in a more intense coloring (2.2 ± 0.8) compared to propylene glycol (1.7 ± 0.9). This study has shown that nebulization with either saline or propylene glycol will result in delivery of particles throughout the entire respiratory tract of healthy racing pigeons. Further studies are needed to establish therapeutic concentrations of medications which can be delivered through nebulization.