The feasibility of home monitoring of impedance with the forced oscillation technique in chronic obstructive pulmonary disease subjects

Abstract

Respiratory system resistance (Rrs) and reactance (Xrs) measured by forced oscillation technique (FOT) can be potentially used for home monitoring in COPD. Our aims were to determine the technical acceptability, adherence and variability of unsupervised, home FOT measurements over ten consecutive days. Supervised spirometry and FOT measurements were made on ten clinically stable COPD subjects at their homes at the study initiation. Subjects then self-recorded FOT twice daily for ten consecutive days with data transmitted to the laboratory server via a 3G mobile network. Subjects had a mean (SD) age of 68(8) years, smoking history 38.4(8.7) pack/years, post-bronchodilator FEV1 42.4(12.0)% predicted, FEV1/FVC ratio 0.45(0.10), mean Rrs 121.7(26.1)% predicted and mean Xrs 746.8(330.3)% predicted. The supervised measurements of mean Rrs and mean Xrs were similar to the unsupervised measurements (p = 0.34 and p = 0.92, respectively). 197 of 200 possible measurements were transmitted, all of which were deemed to be technically acceptable. The within-subject standard deviation, Sw, of Rrs-total and Xrs-total were 0.47 and 1.0 cmH2O L s–1, respectively. Subjects who have COPD make reliable, unsupervised FOT measurements at home with a high degree of adherence. The day-to-day variability of FOT measurements was similar to that of supervised laboratory recordings. These results support the conduct of larger, longer-term studies of FOT monitoring in COPD.