Size estimation:
Common clinical surgical rule: pneumothorax greater than 25% requires chest tube drainage
Drainage actually depends on physiologic status of patient

Small pneumothorax may be devastating in COPD patient with little reserve and conversely a tension pneumothorax may be well tolerated in young athlete

Air slowly resorbs from the pleural space at a rate of approximately 1.5% / day. This rate will increase with use of supplemental oxygen. (Nitrogen is the largest component of the atmosphere and is not metabolized. Thus the partial pressure gradient between the air in the pleural space and capillary blood is small. If nitrogen is decreased by increasing the inspired oxygen concentration, the rate of resorption will increase.)