Affiliations: Department of Anesthesiology and Intensive Care Medicine, Division of Experimental Anesthesiology, University Medical Center Freiburg, Freiburg, Germany
Correspondence:
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Corresponding author: Sara Lozano-Zahonero, Department of Anesthesiology and Intensive Care Medicine Division of Experimental Anesthesiology University Medical Center Freiburg Hugstetter Strasse 55, D-79106 Freiburg, Germany. Tel.: +49 761 270 230 80; Fax: +49 761 270 232 80; E-mail: sara.lozano@uniklinik-freiburg.de.
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 (R2). Results:Without filtering, R2 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 R2 ⩾ 0.995. In contrast, inspiration-selective filtering did not improve R2. 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.
