Lung sound analysis to detect recruitment processes during mechanical ventilation
© BioMed Central Ltd 2008
Published: 13 March 2008
The optimal setting of positive end-expiratory pressure (PEEP) during mechanical ventilation in the ICU is still an open problem . Recruitment processes are important influence factors that are difficult to measure in patients [2, 3]. It is proposed to use lung sound analysis to identify recruitment during mechanical ventilation.
Crackle sounds (Figure 1, right) could be identified and analysed in the recorded sound data offline using Matlab (Mathworks, Natick, MA, USA) for the analysis and visualization. With a window technique, the power of the sound signal in a specific frequency range for crackles (700–900 Hz) was determined. At the beginning of the low-flow manoeuvre, trains of crackles were found that increased in intensity with pressure. At higher pressure levels the crackle intensity decreased, especially in the second and third manoeuvres.
Sound analysis in isolated lungs can reliably detect increasing crackle activities that seem to correlate with visually observable opening of atelectasis.
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