title: Retrospective computed tomography mapping of intrapleural air may demonstrate optimal window for ultrasound diagnosis of pneumothorax.
abstract: BACKGROUND
  When a pneumothorax exists, free air should rise to the most nondependent region within the chest. Current ultrasound (US) examination methodologies may exclude visualization of these areas that may limit the sensitivity of the examination. This retrospective study uses computed tomography (CT) scans to precisely evaluate where free air within the thorax occurs and correlates this location with a presumably optimal US interrogation window.
  
  
  METHODS
  A total of 94 CT scans of patients with a pneumothorax in a single institution from December 2006 to January 2010 were examined. The borders and volumes of each pneumothorax were precisely measured by a radiologist. Logistic regression was used to determine the relationship between volume and location of intrapleural air at specified areas of the hemithorax. Sensitivities relating location of intrapleural air at a specific landmark and side of thorax were calculated.
  
  
  RESULTS
  All but 3 of the pneumothoraces extended to the sternum. In all, 83 patients demonstrated a pneumothorax between rib interspaces 3 and 6 (mean pneumothorax volume 300.4 mL, 95% confidence interval [CI] 217.4-383.3), and 11 patients did not (mean pneumothorax volume 4.5 mL, 95% CI 1.7-7.3; P < .0001). The cumulative sensitivity for the presence of intrapleural air at rib interspaces 3 to 6 along the sternal border was 88%. This was consistent regardless of the side of hemithorax (right 91% and left 86%).
  
  
  CONCLUSIONS
  The CT scans demonstrate that intrapleural air most often collects along the mediastinum between ribs 3 and 6 on either side of the chest. Although no USs were performed in this retrospective study, one may infer that a parasternal approach along rib interspaces 3 to 6 is an easy and sensitive window to diagnose pneumothorax with US.
authors.affiliation: Department of Anesthesiology, University of Florida, College of Medicine, JHMHC, Gainesville, FL, USA skiley@anest.ufl.edu.
authors.forename: Sean
authors.initials: S
authors.lastname: Kiley
authors.affiliation: Department of Anesthesiology, University of Florida, College of Medicine, JHMHC, Gainesville, FL, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tighe
authors.affiliation: Department of Radiology and Nuclear Medicine, Ireland Army Community Hospital, 277 Brentford Drive, Louisville, KY, USA.
authors.forename: Omar
authors.initials: O
authors.lastname: Hajibrahim
authors.affiliation: Department of Radiology, University of Florida, College of Medicine, Gainesville, FL.
authors.forename: Lori
authors.initials: L
authors.lastname: Deitte
authors.affiliation: Department of Anesthesiology, University of Florida, College of Medicine, JHMHC, Gainesville, FL, USA.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Gravenstein
authors.affiliation: Department of Anesthesiology, University of Florida, College of Medicine, JHMHC, Gainesville, FL, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Robinson
mesh_terms: D000328:Adult; D000368:Aged; D000388:Air; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D035422:Pleural Cavity / Q000000981:diagnostic imaging* / Q000473:pathology; D011030:Pneumothorax / Q000000981:diagnostic imaging*; D013902:Radiography, Thoracic; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012272:Ribs / Q000000981:diagnostic imaging* / Q000473:pathology; D012680:Sensitivity and Specificity; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
keywords: chest CT scan; landmarks; pneumothorax; ultrasound