Assessment of a new transtelephonic portable spirometer

A new portable spirometer, the Spirophone, has been developed that records a subject's blow and can then transmit all the data by telephone to a receiving centre for analysis and comment. Tests of this device were undertaken to determine its accuracy and reliability.

The performance of the Spirophone was tested using computer generated wave forms, by delivering blows from calibrated syringes at different flows, and by comparing subjects' blows with those recorded with a commercial spirometer.

Using computer generated wave forms all lung function indices were accurate to within 1% and blows delivered from calibrating syringes were accurate to within 5%. When subjects performed repeated forced vital capacity (FVC) manoeuvres there were no significant differences between lung function indices recorded with the Spirophone and with a commercial spirometer. With the Spirophone and commercial spirometer in series the FVC and forced expiratory volume in one second (FEV1) were within 5% of each other in nine out of 10 healthy subjects.

The Spirophone recorded maximal forced expiratory manoeuvres with acceptable accuracy, reliability, and reproducibility, and this system offers the ability to monitor a patient's lung function at a centre remote from the patient.