Background
Routinely mentioned risk factors for re-expansion pulmonary oedema (RPO) are: young age, large volume drainage and duration of collapsed lung. Of these, the 2010 British Thoracic Society (BTS) guidelines particularly focus on volumetric recommendations, advising that a maximum of 1.5L should be drained on first occasion. 

Objectives
Assess RPO incidence at a high throughput tertiary centre, validity of current BTS volumetric recommendations, and review other potential RPO risk factors.

Methods
Generated a retrospective database of 405 therapeutic drainage episodes over 2.5 years, in 312 patients. Several factors were reviewed, including: procedural factors (volume drained, drainage limited by pain), clinical factors (age, collapsed lung >7 days, heart failure, liver cirrhosis, chronic kidney disease) and biochemical factors (serum albumin, aspirate albumin and protein, CRP).

Results
2 cases (0.5% of n=405) of clinical RPO were identified out of 18 identified radiological cases, both of which had >1.5L drained, characterised by: tachypnoea, oxygen desaturation and requiring changes to the management plan. Regression analysis did not show any association between volume drained, age, collapsed lung >7 days, and radiological or clinical RPO. Patients who had >1.5L drained were more likely to have liver cirrhosis (17 vs 26, p=0.001).

Conclusion
Despite therapeutic pleural effusion drainage at Cambridge University Hospital being guided solely by symptom onset, clinical RPO is a very rare complication with 0.5% incidence and no associated mortality. We did not detect a relationship between volume drained and clinical RPO, so our practice remains safe.