title: Bedside tracer gas technique accurately predicts outcome in aspiration of spontaneous pneumothorax.
abstract: BACKGROUND
  There is no technique in general use that reliably predicts the outcome of manual aspiration of spontaneous pneumothorax. We have hypothesised that the absence of a pleural leak at the time of aspiration will identify a group of patients in whom immediate discharge is unlikely to be complicated by early lung re-collapse and have tested this hypothesis by using a simple bedside tracer gas technique.
  
  
  METHODS
  Eighty four episodes of primary spontaneous pneumothorax and 35 episodes of secondary spontaneous pneumothorax were studied prospectively. Patients breathed air containing a tracer (propellant gas from a pressurised metered dose inhaler) while the pneumothorax was aspirated percutaneously. Tracer gas in the aspirate was detected at the bedside using a portable flame ioniser and episodes were categorised as tracer gas positive (>1 part per million of tracer gas) or negative. The presence of tracer gas was taken to imply a persistent pleural leak. Failure of manual aspiration and the need for a further intervention was based on chest radiographic appearances showing either failure of the lung to re-expand or re-collapse following initial re-expansion.
  
  
  RESULTS
  A negative tracer gas test alone implied that manual aspiration would be successful in the treatment of 93% of episodes of primary spontaneous pneumothorax (p<0.001) and in 86% of episodes of secondary spontaneous pneumothorax (p=0.01). A positive test implied that manual aspiration would either fail to re-expand the lung or that early re-collapse would occur despite initial re-expansion in 66% of episodes of primary spontaneous pneumothorax and 71% of episodes of secondary spontaneous pneumothorax. Lung re-inflation on the chest radiograph taken immediately after aspiration was a poor predictor of successful aspiration, with lung re-collapse occurring in 34% of episodes by the following day such that a further intervention was required.
  
  
  CONCLUSIONS
  National guidelines currently recommend immediate discharge of patients with primary spontaneous pneumothorax based primarily on the outcome of the post-aspiration chest radiograph which we have shown to be a poor predictor of early lung re-collapse. Using a simple bedside test in combination with the post-aspiration chest radiograph, we can predict with high accuracy the success of aspiration in achieving sustained lung re-inflation, thereby identifying patients with primary spontaneous pneumothorax who can be safely and immediately discharged home and those who should be observed overnight because of a significant risk of re-collapse, with an estimated re-admission rate of 1%.
authors.affiliation: Department of Respiratory Medicine, The Ipswich Hospital NHS Trust, Ipswich IP4 5PD, UK.
authors.forename: D G
authors.initials: DG
authors.lastname: Kiely
authors.forename: S
authors.initials: S
authors.lastname: Ansari
authors.forename: W A
authors.initials: WA
authors.lastname: Davey
authors.forename: V
authors.initials: V
authors.lastname: Mahadevan
authors.forename: G J
authors.initials: GJ
authors.lastname: Taylor
authors.forename: D
authors.initials: D
authors.lastname: Seaton
mesh_terms: D000328:Adult; D000335:Aerosol Propellants / Q000032:analysis*; D002985:Clinical Protocols; D004322:Drainage / Q000379:methods; D005260:Female; D006801:Humans; D006838:Hydrocarbons / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge; D011030:Pneumothorax / Q000175:diagnosis* / Q000628:therapy; D019095:Point-of-Care Systems / Q000592:standards*; D011446:Prospective Studies; D012008:Recurrence; D012680:Sensitivity and Specificity
chemical_list: D000335:Aerosol Propellants; D006838:Hydrocarbons