Assessment of a new transtelephonic portable spirometer

Background - 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. Methods - 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. Results - 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 (FEV,) were within 5% of each other in nine out of 10 healthy subjects. Conclusion - 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.