title: Effect of positive end-expiratory pressure on acoustic wave propagation in experimental porcine lung injury.
abstract: To evaluate the effect of positive end-expiratory pressure (PEEP) on sound propagation through injured lungs, we injected a multifrequency broad-band sound signal into the airway of eight anesthetized, intubated and mechanically ventilated pigs, while recording transmitted sound at three locations bilaterally on the chest wall. Oleic acid injections effected a severe pulmonary oedema predominately in the dependent lung regions, with an average increase in venous admixture from 19 ± 15 to 59 ± 14% (P < 0.001), and a reduction in dynamic respiratory system compliance from 34 ± 7 to 14 ± 4 ml cmH2 O(-1) (P < 0.001). A concomitant decrease in sound transit time was seen in the dependent lung regions (P < 0.05); no statistically significant change occurred in the lateral or non-dependent areas. The application of PEEP resulted in a decrease in venous admixture, increase in respiratory system compliance and return of the sound transit time to pre-injury levels in the dependent lung regions. Our results indicate that sound transmission velocity increases in lung tissue affected by permeability-type pulmonary oedema in a manner reversible during alveolar recruitment with PEEP.
authors: Department of Anesthesiology, H. Lee Moffitt Cancer Center, Tampa, FL, USA.
authors: Jukka
authors: J
authors: Räsänen
authors: Michael E
authors: ME
authors: Nemergut
authors: Noam
authors: N
authors: Gavriely
mesh_terms: D000818:Animals; D055370:Lung Injury / Q000175:diagnosis / Q000503:physiopathology*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011650:Pulmonary Alveoli / Q000503:physiopathology*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013016:Sound; D013018:Sound Spectrography / Q000379:methods*; D013552:Swine
keywords: acoustics; acute lung injury; pulmonary oedema; respiratory sounds; transit time