Unsupervised self-testing of airway obstruction by forced oscillation at the patient's home

As active patient cooperation is not required, the forced oscillation technique (FOT) could be suitable for measuring airway obstruction in routine home applications. Nevertheless, FOT has never been used at the patient's home to date. The aim of this study was to assess the feasibility of FOT and the reproducibility of measured respiratory resistance (Rrs) in routine patient self-testing at home. Altogether, nine asthmatic patients self-measured their Rrs with a portable FOT device and spirometry for 10-14 days, in the morning and evening, and before and after bronchodilator inhalation. During each measurement session, the patients carried out four consecutive FOT measurements. Grubbs' discordancy test for detecting outliers was used to evaluate intermeasure reliability. Only 4.9% of Rrs data reported by patients were rejected as artefacts. The coefficient of variation of Rrs was 7.9 +/- 6.3% (mean +/- SD). When compared with spirometry, the per cent change in Rrs for detecting a positive bronchodilator response showed an 83% sensitivity and 72% specificity. Unsupervised self-measurement of respiratory resistance at the patient's home provided results similar to those obtained by a technician in a lung function lab. Forced oscillation technique could be a useful tool for the routine follow-up of asthmatic patients at home.