title: [Monitoring of breathing pattern at rest by electrical impedance tomography].
abstract: OBJECTIVE
  Electrical impedance tomography (EIT) involves the application of a small alternating current to produce a series of chest images that can be used to monitor breathing pattern. The relation between chest images and tidal volume has not been sufficiently validated. The aim of the present study was to analyze the correlation between EIT images and the volume-time signal measured with a pneumotachometer in 13 healthy volunteers.
  
  
  METHODS
  The following measurement devices were used: a) MedGraphics preVent Pneumotach, with special software for recording the volume-time signal (reference test), and b) EIT-4, a fourth-generation prototype unit designed by the Department of Electronic Engineering at the Universidad Politécnica de Cataluña, Spain that records the volume-time signal and produces a graphic depiction of a cross section of the thorax at the sixth intercostal space.
  
  
  RESULTS
  The mean (SD) tidal volume measured by the pneumotachometer and the EIT-4 was 0.523 (0.102) L and 0.527 (0.106) L, respectively (P value not significant). The linear correlation coefficient between the 2 measurements was 0.923 (P=.001), and the mean of the differences between the 2 procedures was -0.003 L (95% confidence interval, -0.045 to 0.038). The greatest differences were associated with female gender, body mass index, and chest circumference. In view of these differences, a different equation based on these variables was needed for calibration of the EIT-4.
  
  
  CONCLUSIONS
  The EIT-4 provides an alternative means of monitoring breathing pattern, although a number of issues related to the circumference of the rib cage need to be resolved.
authors.affiliation: Unitat de Funció Pulmonar, Departament de Pneumologia, Hospital de la Santa Creu i de Sant Pau, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain. jballeza@santpau.es
authors.forename: Marco
authors.initials: M
authors.lastname: Balleza
authors.forename: Jaume
authors.initials: J
authors.lastname: Fornos
authors.forename: Núria
authors.initials: N
authors.lastname: Calaf
authors.forename: Teresa
authors.initials: T
authors.lastname: Feixas
authors.forename: Mercedes
authors.initials: M
authors.lastname: González
authors.forename: Daniel
authors.initials: D
authors.lastname: Antón
authors.forename: Pere
authors.initials: P
authors.lastname: Riu
authors.forename: Pere
authors.initials: P
authors.lastname: Casan
mesh_terms: D000328:Adult; D017097:Electric Impedance; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012119:Respiration; D012129:Respiratory Function Tests / Q000295:instrumentation / Q000379:methods; D012146:Rest / Q000502:physiology*