Method and apparatus for indicating pressure in chest drainage devices

An apparatus for indicating intra-pleural pressure, said apparatus comprising:

• a chamber having an interior region configured to be coupled for fluid flow communication with the pleural cavity of a patient such that the pressure in the interior region of the chamber corresponds substantially to the pressure in the pleural cavity of the patient;
• a bladder positioned within the interior region of said chamber, said bladder having an interior in fluid flow communication with atmosphere such that the pressure in the interior of the bladder corresponds substantially to atmospheric pressure, said bladder also having a concavity formed therein and configured to contract or expand in response to pressure in the pleural cavity;
• and
• surfaces associated with said bladder are configured to move with respect to one another upon contraction or expansion of said concavity of said bladder, thereby indicating intra-pleural pressure in the pleural cavity of the patient.