title: Global tidal variations, regional distribution of ventilation, and the regional onset of filling determined by electrical impedance tomography: reproducibility.
abstract: The reproducibility of the regional distribution of ventilation and the timing of onset of regional filling as measured by electrical impedance tomography lacks evidence. This study investigated whether electrical impedance tomography measurements in healthy males were reproducible when electrodes were replaced between measurements. Part 1: Recordings of five volunteers lying supine were made using electrical impedance tomography and a pneumotachometer. Measurements were repeated at least three hours later. Skin marking ensured accurate replacement of electrodes. No stabilisation period was allowed. Part 2: Electrical impedance tomography recordings of ten volunteers; a 15 minute stabilisation period, extra skin markings, and time-averaging were incorporated to improve the reproducibility. Reproducibility was determined using the Bland-Altman method. To judge the transferability of the limits of agreement, a Pearson correlation was used for electrical impedance tomography tidal variation and tidal volume. Tidal variation was judged to be reproducible due to the significant correlation between tidal variation and tidal volume (r2= 0.93). The ventilation distribution was not reproducible. A stabilisation period, extra skin markings and time-averaging did not improve the outcome. The timing of regional onset of filling was reproducible and could prove clinically valuable. The reproducibility of the tidal variation indicates that non-reproducibility of the ventilation distribution was probably a biological difference and not measurement error. Other causes of variability such as electrode placement variability or lack of stabilisation when accounted for did not improve the reproducibility of the ventilation distribution.
authors.affiliation: Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, The University of Queensland School of Medicine, Brisbane, Queensland.
authors.forename: L R
authors.initials: LR
authors.lastname: Caruana
authors.affiliation: Associate Professor, The Critical Care Research Group, The Prince Charles Hospital, School of Public Health & Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland.
authors.forename: A G
authors.initials: AG
authors.lastname: Barnett
authors.affiliation: Clinical Lead Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland.
authors.forename: O
authors.initials: O
authors.lastname: Tronstad
authors.affiliation: Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, Burns, Trauma and Critical Research Centre, School of Medicine, University of Queensland, Brisbane, Griffith University, Southport, Queensland.
authors.forename: J D
authors.initials: JD
authors.lastname: Paratz
authors.affiliation: Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland.
authors.forename: A T
authors.initials: AT
authors.lastname: Chang
authors.affiliation: Director, The Critical Care Research Group, The Prince Charles Hospital, Professor, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland.
authors.forename: J F
authors.initials: JF
authors.lastname: Fraser
mesh_terms: D000328:Adult; D017097:Electric Impedance; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology*; D014054:Tomography / Q000379:methods*
keywords: Electrical impedance tomography, regional distribution of ventilation, reproducibility, repeatability, tidal variation