title: Characteristics of trapped lung: pleural fluid analysis, manometry, and air-contrast chest CT.
abstract: OBJECTIVE
  To review the pleural fluid characteristics, pleural manometry, and radiographic data of patients who received a diagnosis of trapped lung in our pleural diseases service.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  The procedure records of 247 consecutive patients who underwent pleural manometry at the Medical University of South Carolina between October 2002 and November 2005 were reviewed. Eleven patients in whom a diagnostic pneumothorax was introduced were identified. Manometry data, radiographic findings, pleural fluid analysis, final clinical diagnosis, and information regarding the initial pleural insult were retrieved from the medical record.
  
  
  RESULTS
  All 11 patients had a clinical diagnosis of trapped lung. The causes of trapped lung were attributed to coronary artery bypass graft surgery, uremia, thoracic radiation, pericardiotomy, spontaneous bacterial pleuritis and repeated thoracentesis, and complicated parapneumonic effusion. Mean pleural fluid pH was 7.30, pleural fluid lactate dehydrogenase (LDH) was 124 IU/L, and pleural fluid total protein was 2.9 g/dL. Pleural fluid was paucicellular with mononuclear cell predominance. Pleural space elastance was increased in all cases and ranged from 19 to 149 cm H(2)O/L of pleural fluid removed. All demonstrated abnormal visceral pleural thickness on air-contrast chest CT.
  
  
  CONCLUSIONS
  Trapped lung is a clinical entity characterized by the presence of a restrictive visceral pleural peel that was first described in 1967. The pleural fluid is paucicellular, LDH is low, and protein may be in the exudative range. The elevated total pleural fluid protein may be related to factors other than active pleural inflammation or malignancy and does not exclude the diagnosis.
authors.affiliation: Division of Pulmonary, Critical Care,, Allergy and Sleep Medicine, Medical University of South Carolina, PO Box 250625, Charleston, SC 29425, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Huggins
authors.forename: Steven A
authors.initials: SA
authors.lastname: Sahn
authors.forename: Jay
authors.initials: J
authors.lastname: Heidecker
authors.forename: James G
authors.initials: JG
authors.lastname: Ravenel
authors.forename: Peter
authors.initials: P
authors.lastname: Doelken
mesh_terms: D002985:Clinical Protocols; D005122:Exudates and Transudates / Q000737:chemistry; D005260:Female; D006801:Humans; D008171:Lung Diseases / Q000150:complications*; D008297:Male; D008365:Manometry; D019152:Paracentesis; D010996:Pleural Effusion / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy; D013902:Radiography, Thoracic; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed