Evaluation of a new spirometer based on a fluidistor technique.

Abstract

Using a mechanical model and human subjects a new spirometer based on fluidistor principles was evaluated. At normal minute volumes the fluidistor was accurate to within +/-5% when compared with a Bernstein spirometer. It underread at low volumes and overread at high. Prolonged expiratory time constant as well as the use of gas with low density increased the error. The instrument was somewhat sensitive to variation in breathing frequency and gas flow pattern but insensitive to moisture. The resistance to gas flow of the instrument itself was fairly high. The fluidistor is based on a sound and simple principle (no movable parts). It proved to be stable and easy to handle and accurate enough for clinical use in anaesthesia and intensive care. The tendency of the spirometer to underread at low flow and to overread at high flow could possibly be substantially reduced if the instrument was provided with several flow heads so that the oscillation volume could be individually adapted to the gas flow rate to be studied.