### Description

The pressure applied to the pleural space using a 3-bottle suction system can be estimated based on several measurements of the components.

3 Bottle Suction System:

(1) Bottle 1 - connected to chest tube in patient and bottle 2 by tubing

(2) Bottle 2 - airseal, connected to bottles 1 and 3

(3) Bottle 3 - connected to suction and bottle 2, with tubing open to air

Bottle 1 has 2 ports close to the stopper, both of which are above the fluid in the container. This bottle collects the drainage fluid. While the tubing connecting the 3 bottles is relatively short since the bottles are close together, the tubing coming from the chest tube to the first bottle may be long and will often have a reverse J-shape.

Bottle 2 has 2 ports.

(1) The port connected to bottle 1 is connected to rigid tubing that is under water. This forms the water seal.

(2) The port connected to bottle 3 is above the fluid.

Bottle 3 has 3 ports:

(1) The port connected to bottle 2 is well above the fluid in the bottle.

(2) The port connected to suction source is well above the fluid in the bottle.

(3) The third port has one end open to the air and the other end under water. This determines the effective suction pressure.

Parameters:

(1) The distance in centimeters that the air port in bottle 3 is under water (vertical distance from water surface to level of tube opening).

(2) The distance in centimeters that the water seal tube in bottle 2 is under water (vertical distance from water surface to level of tube opening).

(3) The vertical distance in centimeters between the level of the chest tube and the lowest point of the tube leading to bottle 1.

(4) The vertical distance in centimeters between the lowest point of the tube leading to bottle 1 and the level of the outside of the tube forming the water seal in bottle 2.

pressure applied to the pleural space in cm H2O =

= (-1) * ((vertical distance in cm from chest tube to the lowest point) - (vertical distance from the lowest point to the entrance tube for bottle 1) - (vertical distance in cm of the water seal) + (vertical distance in cm of the air port below the water surface))

where:

• The pressure applied to the pleural space should be negative.