Lung sound analysis correlates to injury and recruitment as identified by computed tomography: an experimental study



The aim of this study is to assess how analysis of the spectral characteristics of lung sounds can help in detecting lung injury and subsequent recruitment as verified by computed tomography (CT).


Lung sounds were recorded at four locations (ventral and dorsal on right and left side) in six ventilated pigs before and after unilateral oleic acid-induced lung injury during sequential increase of positive end-expiratory pressure (PEEP) from 0 to 20 cmH2O. CT scans of the chest were used for comparison with lung aeration. Sound characteristics were compared by computer-aided analysis in the time and frequency domain as well as by clinicians.


The presence of lung injury and its location were detected by substantial acoustic spectral components above 500 Hz (frequency) and −70 dB (amplitude). Application of increasing PEEP gradually reduced the pathological components as CT analysis verified recruitment. At 20 cmH2O PEEP there was no further tidal recruitment of injured lung and the pathological sounds had disappeared, rendering the lung sounds of the injured lung similar to those of the control lung. This was mirrored by the clinicians’ characterization of the sounds.


Computer-aided analysis of lung sounds is suitable for detection of pathological lung sounds and may guide in detection and recruitment of poorly/nonaerated lung.

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This study was supported by grants from The Swedish Medical Research Council (5315); The School of Anesthesiology and Intensive Care Medicine, Bari University, Italy; and The Center of Innovative Technologies for Signal Detection and Processing (TIRES), Bari University, Italy. The authors thank Agneta Roneus, Karin Fagerbrink, Eva-Maria Hedin (Hedenstierna Laboratory, Department of Medical Sciences, Uppsala University, Sweden), and Monica Segelsjö (Department of Radiology, Uppsala University, Sweden) for their valuable assistance during the experiments.

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Correspondence to Christian Rylander.

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This article is discussed in the editorial available at: doi:10.1007/s00134-011-2292-3.

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Vena, A., Rylander, C., Perchiazzi, G. et al. Lung sound analysis correlates to injury and recruitment as identified by computed tomography: an experimental study. Intensive Care Med 37, 1378–1383 (2011).

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  • Acute lung injury
  • Lung sounds
  • Crackles
  • Frequency analysis
  • Positive end-expiratory pressure