title: Prevalence of large and occult pneumothoraces in patients with severe blunt trauma upon hospital admission: experience of 526 cases in a French level 1 trauma center.
abstract: BACKGROUND
  Occult pneumothoraces (PTXs), which are not visible on chest x-ray, may progress to tension PTX. The aim of study was to establish the prevalence of large occult PTXs upon admission of patients with severe blunt trauma, according to prehospital mechanical ventilation.
  
  
  METHODS
  Patients with severe trauma consecutively admitted to our institution for 5 years were retrospectively analyzed. All patients with blunt thoracic trauma who had undergone computed tomographic (CT) within the first hour of hospitalization were included. Mechanical ventilation was considered as early if it was introduced in the prehospital period or on arrival at the hospital. Occult PTXs were defined as PTXs not visible on chest x-ray. All PTXs were measured on CT scan (largest thickness and vertical dimension). Large occult PTXs were defined by a largest thickness of 30 mm or more.
  
  
  RESULTS
  Of the 526 patients studied, 395 (75%) were male, mean age was 37.9 years, mean Injury Severity Score was 22.2, and 247 (47%) received early mechanical ventilation. Of 429 diagnosed PTXs, 296 (69%) were occult. The proportion of occult PTXs classified as large was 11% (95% confidence interval, 8%-15%). The overall prevalence of large occult PTXs was 6% (95% confidence interval, 4%-8%). Both CT measurements and proportion of large occult PTXs were found statistically comparable in patients with or without mechanical ventilation.
  
  
  CONCLUSIONS
  Six percent of studied patients with severe trauma had a large and occult PTX as soon as admission despite a normal chest x-ray result. The observed sizes and rates of occult PTX were comparable regardless of the initiation of early mechanical ventilation.
authors.affiliation: Trauma Intensive Care Unit, Lapeyronie University Hospital, Montpellier, France; Montpellier I University, Montpellier, France. Electronic address: j-charbit@chu-montpellier.fr.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Charbit
authors.affiliation: Montpellier I University, Montpellier, France; Department of Radiology, Lapeyronie University Hospital, Montpellier, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Millet
authors.affiliation: Trauma Intensive Care Unit, Lapeyronie University Hospital, Montpellier, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Maury
authors.affiliation: Trauma Intensive Care Unit, Lapeyronie University Hospital, Montpellier, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Conte
authors.affiliation: Trauma Intensive Care Unit, Lapeyronie University Hospital, Montpellier, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Roustan
authors.affiliation: Montpellier I University, Montpellier, France; Department of Radiology, Lapeyronie University Hospital, Montpellier, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Taourel
authors.affiliation: Trauma Intensive Care Unit, Lapeyronie University Hospital, Montpellier, France; Montpellier I University, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, Equipe soutenue par la Région et l'Inserm U1046 (X.C.), Montpellier, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Capdevila
mesh_terms: D000328:Adult; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D015601:Injury Severity Score; D008297:Male; D011030:Pneumothorax / Q000000981:diagnostic imaging / Q000453:epidemiology*; D015995:Prevalence; D012121:Respiration, Artificial; D012189:Retrospective Studies; D013898:Thoracic Injuries / Q000000981:diagnostic imaging / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed; D014193:Trauma Centers; D014949:Wounds, Nonpenetrating / Q000000981:diagnostic imaging / Q000453:epidemiology*