title: A study of artifacts and their removal during forced oscillation of the respiratory system.
abstract: Respiratory impedance measured by the forced oscillation technique (FOT) can be contaminated by artifacts such as coughing, vocalization, swallowing or leaks at the mouthpiece. We present a novel technique to detect these artifacts using multilevel discrete wavelet transforms. FOT was performed with artifacts introduced during separate 60 s recordings at known times in 10 healthy subjects. Brief glottal closures were generated phonetically and confirmed by nasopharyngoscopic imaging of the glottis. Artifacts were detected using Daubechies wavelets by applying a threshold to squared detail coefficients from the wavelet transforms of both pressure and flow signals. Sensitivity and specificity were compared over a range of thresholds for different level squared detail coefficients. Coughs could be identified using 1st level detail (cd1) coefficients of pressure achieving 96% sensitivity and 100% specificity while swallowing could be identified using cd2 thresholds of pressure with 95% sensitivity and 97% specificity. Male vocalizations could be identified using cd1 coefficients with 88% sensitivity and 100% specificity. For leaks at the mouthpiece, cd3 thresholds of flow could identify these events with 98% sensitivity and 99% specificity. Thus, this method provided an accurate, easy, and automated technique for detecting and removing artifacts from measurements of respiratory impedance using FOT.
authors.affiliation: School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada. swatib@dal.ca
authors.forename: Swati A
authors.initials: SA
authors.lastname: Bhatawadekar
authors.forename: Del
authors.initials: D
authors.lastname: Leary
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: J
authors.initials: J
authors.lastname: Ohishi
authors.forename: P
authors.initials: P
authors.lastname: Hernandez
authors.forename: T
authors.initials: T
authors.lastname: Brown
authors.forename: C
authors.initials: C
authors.lastname: McParland
authors.forename: Geoff N
authors.initials: GN
authors.lastname: Maksym
mesh_terms: D000328:Adult; D016477:Artifacts; D003371:Cough; D003679:Deglutition; D001330:Electronic Data Processing; D005260:Female; D006801:Humans; D008297:Male; D010699:Phonation; D012123:Pulmonary Ventilation; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D012727:Sex Characteristics