Research

Changes in regional distribution of lung sounds as a function of positive end-expiratory pressure

Shaul Lev¹ , Yael A Glickman² , Ilya Kagan¹ , David Dahan¹ , Jonathan Cohen¹ , Milana Grinev¹ , Maury Shapiro¹ and Pierre Singer¹

¹Department of General Intensive Care, Rabin Medical Center, Beilinson Campus, 39 Jabotinski Street., Petach Tikva, 49100, Israel

²Deep Breeze, Ltd., 2 Hailan St., P.O. Box 140, North Industrial Park, Or-Akiva, 30600, Israel

author email corresponding author email

Critical Care 2009, 13:R66doi:10.1186/cc7871

Published:	10 May 2009

See related commentary by Marini, http://ccforum.com/content/13/4/162

Abstract

Introduction

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). Repeatability of automated lung sound measurements was also evaluated.

Methods

Regional 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.

Results

A 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.

Conclusions

Lung 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.