Microcomputer-Based System for Administering Metered Dose Aerosol Formulations to Dogs

Abstract

A microcomputer-based system has been developed for administering metered dose aerosol formulations to dogs during toxicology studies. The apparatus comprises a thermistor bead mounted at the outlet of a dosing chamber that in turn is connected to an oropharyngeal tube. Attached to the inlet of the chamber is an actuator unit containing the aerosol. The actuator unit incorporates an operating plunger, a microswitch counting mechanism, a one-way valve, and an extract line connected to a vacuum pump. The signals from the thermistor bead and counting mechanism pass via a preamplifier control box to a computer. Also connected to the computer are a balance, a printer, and a monitor.

The computer software was specially written for the system. Before starting a study the computer is programmed with details specific to the study. The system selects a dog to be dosed and weighs the aerosol pack. The dosing session commences when the oropharyngeal tube is placed into the dog's mouth. On completion of dosing, the aerosol pack is reweighed and the dose calculated. Throughout dosing, the computer screen displays the respiratory pattern, aerosol dosing information, and warnings of errors. Data records produced by the system satisfy the standards of Good Laboratory Practice. The system has been evaluated and assessed in a preliminary study that compared the old and new methods. The new dosing system has many advantages, providing more accurate dosing and recording. It is easy to use and facilitates estimation of drug deposited in the apparatus. In addition, the dog is more tolerant of the procedure, as inspiratory resistance is significantly reduced.