Abstract
IntroductionAutomated mapping of lung sound distribution is a novel area of interest currently investigated in mechanically ventilated, critically ill patients. The objective of the present study was to assess changes in thoracic sound distribution resulting from changes in positive end-expiratory pressure (PEEP). Repeatability of automated lung sound measurements was also evaluated.MethodsRegional lung sound distribution was assessed in 35 mechanically ventilated patients in the intensive care unit (ICU). A total of 201 vibration response imaging (VRI) measurements were collected at different levels of PEEP between 0 and 15 cmH2O. Findings were correlated with tidal volume, oxygen saturation, airway resistance, and dynamic compliance. Eighty-two duplicated readings were performed to evaluate the repeatability of the measurement.ResultsA significant shift in sound distribution from the apical to the diaphragmatic lung areas was recorded when increasing PEEP (paired t-tests, P < 0.05). In patients with unilateral lung pathology, this shift was significant in the diseased lung, but not as pronounced in the other lung. No significant difference in lung sound distribution was encountered based on level of ventilator support needed. Decreased lung sound distribution in the base was correlated with lower dynamic compliance. No significant difference was encountered between repeated measurements.ConclusionsLung sounds shift towards the diaphragmatic lung areas when PEEP increases. Lung sound measurements are highly repeatable in mechanically ventilated patients with various lung pathologies. Further studies are needed in order to fully appreciate the contribution of PEEP increase to diaphragmatic sound redistribution.
Highlights
Automated mapping of lung sound distribution is a novel area of interest currently investigated in mechanically ventilated, critically ill patients
Further studies are needed in order to fully appreciate the contribution of positive end-expiratory pressure (PEEP) increase to diaphragmatic sound redistribution
Changes in lung sound distribution map during recruitment maneuver and PEEP increase were reported in four abstracts [29,30,31,32]. These findings suggest that breath sound information can be used to evaluate lung condition during mechanical ventilation; information regarding lung sound monitoring to adjusted PEEP levels is lacking
Summary
Automated mapping of lung sound distribution is a novel area of interest currently investigated in mechanically ventilated, critically ill patients. The objective of the present study was to assess changes in thoracic sound distribution resulting from changes in positive end-expiratory pressure (PEEP). Several studies assessed the effect of changes of mechanical ventilation on lung sound distribution in animal models [1317]. Räsenen and colleagues reported that the acoustic changes associated with oleic acid-induced lung injury allow monitoring of its severity and distribution [13] and that acute lung injury (ALI) causes regional acoustic transmission abnormalities that are reversed during alveolar recruitment with positive end-expiratory pressure (PEEP) [14]. Vena and colleagues reported a reduction of amplitude and a change in spectral characteristics of normal lung sounds when increas-
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