title: Using thoracic ultrasonography to accurately assess pneumothorax progression during positive pressure ventilation: a comparison with CT scanning.
abstract: BACKGROUND
  Although thoracic ultrasonography accurately determines the size and extent of occult pneumothoraces (PTXs) in spontaneously breathing patients, there is uncertainty about patients receiving positive pressure ventilation. We compared the lung point (ie, the area where the collapsed lung still adheres to the inside of the chest wall) using the two modalities ultrasonography and CT scanning to determine whether ultrasonography can be used reliably to assess PTX progression in a positive-pressure-ventilated porcine model.
  
  
  METHODS
  Air was introduced in incremental steps into fi ve hemithoraces in three intubated porcine models. The lung point was identified on ultrasound imaging and referenced against the lateral limit of the intrapleural air space identified on the CT scans. The distance from the sternum to the lung point (S-LP) was measured on the CT scans and correlated to the insufflated air volume.
  
  
  RESULTS
  The mean total difference between the 131 ultrasound and CT scan lung points was 6.8 mm (SD, 7.1 mm; range, 0.0-29.3 mm). A mixed-model regression analysis showed a linear relationship between the S-LP distances and the PTX volume ( P , .001).
  
  
  CONCLUSIONS
  In an experimental porcine model, we found a linear relation between the PTX size and the lateral position of the lung point. The accuracy of thoracic ultrasonography for identifying the lung point (and, thus, the PTX extent) was comparable to that of CT imaging. These clinically relevant results suggest that ultrasonography may be safe and accurate in monitoring PTX progression during positive pressure ventilation.
authors.affiliation: Department of Research and Development, Norwegian Air Ambulance Foundation, Droebak, Norway; Department of Anesthesiology and Intensive Care, Stavanger University Hospital, Stavanger, Norway. Electronic address: nils.petter.oveland@norskluftambulanse.no.
authors.forename: Nils Petter
authors.initials: NP
authors.lastname: Oveland
authors.affiliation: Department of Research and Development, Norwegian Air Ambulance Foundation, Droebak, Norway; Department of Surgical Sciences, University of Bergen, Bergen, Norway.
authors.forename: Hans Morten
authors.initials: HM
authors.lastname: Lossius
authors.affiliation: Faculty of Health Sciences, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Wemmelund
authors.affiliation: Department of Radiology, Stavanger University Hospital, Stavanger, Norway.
authors.forename: Paal Johan
authors.initials: PJ
authors.lastname: Stokkeland
authors.affiliation: Department of Anesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Knudsen
authors.affiliation: Faculty of Health Sciences, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Anesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Erik
authors.initials: E
authors.lastname: Sloth
mesh_terms: D000818:Animals; D018450:Disease Progression; D005260:Female; D008168:Lung / Q000000981:diagnostic imaging; D023421:Models, Animal; D011030:Pneumothorax / Q000000981:diagnostic imaging*; D011175:Positive-Pressure Respiration; D012044:Regression Analysis; D015203:Reproducibility of Results; D013552:Swine; D035441:Thoracic Wall / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*