Q: 64 year old male, admitted to ICU for unrelated reason, found to have about 10%  of pneumothorax (PTX) after subclavian central venous line placement. Patient is hemodynamically stable, alert, oriented and saturation is 98% on room air. You decided to observe the patient. What amount of oxygen should be applied at least via nasal canula to increase the absorption of pneumothorax?

Answer: 3 L/min

By applying oxygen, you may be able to treat stable, low volume, PTX by process called "Nitrogen washout". On room air, most of the air volume trapped in the pleural space is Nitrogen. By breathing higher amount of oxygen, you lower the level of Nitrogen within the alveoli and, thus, the nitrogen in the pleural space will diffuse across (down the gradient).

Though it would not harm to apply 100% non-rebreather mask (NRM) in a patient who has no contraindication, oxygen administration at 3 L/min nasal canula or higher flow is associated with a 4-fold increase in the rate of pleural air absorption compared with room air alone.




Moore FO, Goslar PW, Coimbra R, et al. Blunt Traumatic Occult Pneumothorax: Is Observation Safe?-Results of a Prospective, AAST Multicenter Study. J Trauma. May 2011;70(5):1019-1025