A virtual instrument for measurement of expiratory parameters

Measurement of expiratory parameters provide useful information about overall respiratory system that can be fundamental in categorizing and staging pulmonary diseases. In contrast to the conventional stand-alone instrument, a PC based virtual instrument for the measurement of expiratory parameters has been proposed in this paper. A flow sensor based on the principle of constant temperature hot-wire anemometry has been developed to measure the airflow through the mouth of the subject during expiration. Output signal of the anemometer is connected to a PC through an analog to digital interface card, PCI 6025E from National Instruments. A virtual instrument with all controls, indicators and display required for the measurement and interpretation of expiratory parameters has been developed using the software package LabVIEW.