A 65 y.o. woman with a hx of lung cancer with a large L hilar mass, is transferred from an outside hospital

She had a chest tube placed for “pneumothorax” at the OSH. Why does she still have a collapsed lung?

hint: it has something to do with the hilar mass

Our patient had an “ex vacuo” pneumothorax.  This is a complication of lobar collapse . Bronchogenic carcinoma, mucous plugs , foreign bodies or a malpositioned endotracheal tube can cause lobar collapse.   There is a marked increase in negative intrapleural pressure around the collapsed lobe that draws nitrogen from the blood into the pleural space.  The differences between this and a standard pneumothorax are two:  it is treated by relieving the obstruction, not a chest tube and the gas in the pleural space is nitrogen; not air. This is because oxygen in the bloodstream is dealt with more efficiently than nitrogen.

The Eads bridge built in St.Louis in 1874 was one of the first times nitrogen gas was implicated in disease. Multiple workers on the bridge were in caissons working at increased pressure below the surface of the water because .compressed air was forced into the caissons They developed nitrogen bubbles in the blood as the climbed out into the lower pressures above. (Think of it as opening a bottle of soda with dissolved CO 2. When the cap is removed the pressure drops and bubbles come to the surface.)

Our  patient’s course  was complicated for other reasons.   Her lactate was elevated and she had euglycemic DKA. This is well described with a sodium-glucose cotransporter 2 inhibitor. (SGLT2). It can prevent like starvation ketosis but the  serum bicarb is usually > 18 in starvation ketosis. Common names are jardiance, farxiga and invokana. Our patients CO2 was 5, lactate 3.7 and glucose 164.. The mechanism of euglycemic DKA is shown below.

Our patient’s cancer was widely metastatic and not responding to chemo so the obstruction was persistent . She was seen at an OSH and a chest tube was placed which did not improve the gas collection and she was sent here.   For us the question was; is it just an ex vacuo pneumothorax or did the chest tube insertion cause a real pneumothorax? Multiple chest tubes were placed first in the ED and then by thoracic surgery.  There was no airleak ruling out a bronchopleural fistula.  Multiple chest tubes failed to relieve the gas collection.  She was made comfort care and expired.

Berdon W, Dee G, Abranson S et al. Localized pneumothorax adjacent to a collapsed lobe;a sign of bronchial obstruction. Radiolog 1984:150 (3):691-4.

Ponrartana S, Laberge J, Kerlan R. Management of patients with “ex vacuo” pneumothorax after thoracentesis 2005 Academic radiology. 12(8):980-6.

https://www.renalfellow.org/2020/09/08/sglt2-inhibitor-induced-euglycemic-diabetic-ketoacidosis/

Chamber divers by Rachel Lance