Principles for inhalation exposure systems using concurrent flow spirometry

Abstract

Principles are given for the design and operation of a new class of inhalation exposure systems using concurrent flow spirometry (CFS), a simple method for providing realtime measurement of respiratory volumes and rates during inhalation exposure by mouth or nose of individual experimental animals or man to known concentrations of aerosols or gases. No reciprocating valves are required because the rate of flow of gas or aerosol that is offered to the animal exceeds its maximum exhalation flow rate by a sufficient margin. This technique is especially useful for inhalation exposure of larger experimental animals, such as horses, where whole body plethysmography is usually impractical. Difficulties encountered with conventional exposure systems in maintenance of uniform aerosol or gas concentrations and in prevention of large pressure excursions in the exposure chamber during breathing of subject are obviated by systems using CFS. Deposition of inhaled material in the animal must be determined by in vivo measurements of radioactive labels rather than by comparing inhaled and exhaled concentrations. Two exposure units with CFS are described: one for Beagle dogs and one for ponies.