title: Response of acoustic transmission to positive airway pressure therapy in experimental lung injury.
abstract: OBJECTIVE
  To evaluate the effect of positive end-expiratory pressure on the sound filtering characteristics of injured lungs.
  
  
  METHODS
  Prospective experimental study in the animal laboratory in an academic medical center.
  
  
  METHODS
  Six 35- to 45-kg anesthetized, intubated pigs.
  
  
  METHODS
  Acute lung injury with intravenous oleic acid.
  
  
  RESULTS
  We injected a multifrequency broad-band sound signal into the airway while recording transmitted sound at three locations bilaterally on the chest wall. Oleic acid injections effected a severe pulmonary edema predominantly in the dependent lung regions, with an average increase in venous admixture from 16+/-14% to 57+/-13% and a reduction in static respiratory system compliance from 31+/-6 to 16+/-3 ml/cm H(2)O. A significant concomitant increase in sound transfer function amplitude was seen in the dependent and lateral lung regions; little change occurred in the nondependent areas. The application of PEEP resulted in a decrease in venous admixture, increase in respiratory system compliance, and return of the sound transmission to preinjury levels.
  
  
  CONCLUSIONS
  Acute lung injury causes regional acoustic transmission abnormalities that are reversed during alveolar recruitment with PEEP.
authors.affiliation: Department of Anesthesiology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA. rasanen.jukka@mayo.edu
authors.forename: Jukka
authors.initials: J
authors.lastname: Räsänen
authors.forename: Noam
authors.initials: N
authors.lastname: Gavriely
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000162:Acoustics / Q000295:instrumentation; D000818:Animals; D006439:Hemodynamics; D019301:Oleic Acid / Q000633:toxicity; D011175:Positive-Pressure Respiration; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000628:therapy*; D013552:Swine
chemical_list: D019301:Oleic Acid