Author(s): Charles E. Forbes, Robert E. Coifman and Stephen Monfre
As a device for measuring lung function in pulmonary medicine, we have developed a probe containing a strain gauge housed in a plastic form with two wires that connect to an audio jack, for communication with electronic equipment. This device is proposed as an alternative to sensors currently employed in instruments, such as spirometers and forced oscillation technique devices (FOT). The ruggedness and low cost of the probe make it suitable for personal monitoring devices. The physical properties of our sensor appears to be responsible for two classes of anomaly, in its ability to measure airflow. The first is polymer creep, for which we have developed a correction algorithm yielding a square wave voltage output to a square wave airflow input. The second anomaly is a “hump” in the voltage airflow curve that slightly lowers the accuracy at low flow rates. Other tests show minimal airflow resistance, promise for conformity to American Thoracic Society spirometry waveform standards, utility as a device for measuring bidirectional airflow, and promise for FOT applications. The probes have a simple form factor and are easily manufactured.
