title: Breathing-phase selective filtering of respiratory data improves analysis of dynamic respiratory mechanics.
abstract: BACKGROUND
  The analysis of non-linear respiratory system mechanics under the dynamic conditions of controlled mechanical ventilation is affected by systemic disturbances of the respiratory signals. Cardio-pulmonary coupling induces cardiogenic oscillations to the respiratory signals, which appear prominently in the second half of expiration.
  
  
  OBJECTIVE
  We hypothesized that breathing phase-selective filtering of expiratory data improves the analysis of respiratory system mechanics.
  
  
  METHODS
  We retrospectively analyzed data from a multicenter-study (28 patients with injured lungs, under volume-controlled ventilation) and from two additional studies (3 lung healthy patients and 3 with injured lungs, under pressure-controlled ventilation). Data streams were recorded at different levels of positive end-expiratory pressure. Using the gliding-SLICE method, intratidal dynamic respiratory mechanics were analyzed with and without low-pass filtering of expiratory or inspiratory data separately. The quality of data analysis was derived from the coefficient of determination R^2.
  
  
  RESULTS
  Without filtering, R^2 lay below 0.995 for 87 of 280 investigated data streams. In 68 cases expiration-selective low-pass filtering improved the quality of analysis to R^2 ⩾ 0.995. In contrast, inspiration-selective filtering did not improve R^2.
  
  
  CONCLUSIONS
  The selective filtering of expiration data eliminates negative side-effects of cardiogenic oscillations thus leading to a significant improvement of the analysis of dynamic respiratory system mechanics.
authors: Department of Anesthesiology and Intensive Care Medicine, Division of Experimental Anesthesiology, University Medical Center Freiburg, Freiburg, Germany.
authors: Sara
authors: S
authors: Lozano-Zahonero
authors: Department of Anesthesiology and Intensive Care Medicine, Division of Experimental Anesthesiology, University Medical Center Freiburg, Freiburg, Germany.
authors: Sarah
authors: S
authors: Buehler
authors: Department of Anesthesiology and Intensive Care Medicine, Division of Experimental Anesthesiology, University Medical Center Freiburg, Freiburg, Germany.
authors: Stefan
authors: S
authors: Schumann
authors: Department of Anesthesiology and Intensive Care Medicine, Division of Experimental Anesthesiology, University Medical Center Freiburg, Freiburg, Germany.
authors: Josef
authors: J
authors: Guttmann
mesh_terms: D004867:Equipment Design; D006801:Humans; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000295:instrumentation*; D015656:Respiratory Mechanics / Q000502:physiology*; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*
keywords: Controlled mechanical ventilation; cardiogenic oscillations; dynamic respiratory mechanics