title: Systematic review of spontaneous pneumomediastinum: a survey of 22 years' data.
abstract: OBJECTIVE
  To describe and clarify management protocols in relation to spontaneous pneumomediastinum, and try to integrate criteria on this subject.
  
  
  BACKGROUND
  Thoracic physicians are faced with patients who present with gas in the mediastinum, frequently without an obvious etiologic factor. Published material contains heterogeneous information from which different conclusions can be drawn.
  
  
  METHODS
  In a Medline search from 1990 to 2012, we collected data on mortality, morbidity, signs, symptoms, etiologic factors, and diagnostic methods. Standardized mean differences were calculated.
  
  
  RESULTS
  We identified 600 patients in 27 papers with series of >5 patients without precipitating or etiologic factors previous to the clinical presentation, but athletic activity, drug abuse, and history of asthma played an apparent role in the disease process. Most patients complained of thoracic pain and dyspnea, with subcutaneous emphysema and Hamman's sign. The most common complication was tension pneumothorax. Morbidity was seen in 2.8%; no mortality has been reported so far.
  
  
  CONCLUSIONS
  Spontaneous pneumomediastinum is a rare disease with a benign course, which should be treated conservatively unless a complication mandates an invasive procedure. An algorithm for diagnosis and treatment is offered, based on the available evidence.
authors.affiliation: Department of Cardiothoracic Surgery, General Hospital of Mexico "Dr. Eduardo Liceaga", Mexico City, Mexico wadafa@hotmail.com.
authors.forename: Walid L
authors.initials: WL
authors.lastname: Dajer-Fadel
authors.affiliation: Department of Cardiothoracic Surgery, General Hospital of Mexico "Dr. Eduardo Liceaga", Mexico City, Mexico.
authors.forename: Rubén
authors.initials: R
authors.lastname: Argüero-Sánchez
authors.affiliation: Department of Cardiothoracic Surgery, General Hospital of Mexico "Dr. Eduardo Liceaga", Mexico City, Mexico.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ibarra-Pérez
authors.affiliation: Department of Cardiothoracic Surgery, General Hospital of Mexico "Dr. Eduardo Liceaga", Mexico City, Mexico.
authors.forename: Francisco P
authors.initials: FP
authors.lastname: Navarro-Reynoso
mesh_terms: D000465:Algorithms; D019091:Critical Pathways; D006801:Humans; D008478:Mediastinal Emphysema / Q000175:diagnosis / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D011237:Predictive Value of Tests; D012307:Risk Factors; D016896:Treatment Outcome
keywords: Mediastinal emphysema; subcutaneous emphysema