Chest drainage unit with controlled automatic excess negativity relief

Abstract

The present invention provides for an improved air-flow sensitive float valve interposed between the collection chamber and one arm of the water seal chamber for allowing the patient to draw as much vacuum pressure as is required during deep inspiration. The float valve also functions to provide for an automatic controlled release of excess negative pressure in the collection chamber during either continuous autotransfusion or when there is a low air flow rate condition present. By tailoring a specific amount of water to a given size chamber, the water column inside the water seal chamber is allowed to momentarily engage the floating mechanism before the water seal chamber is emptied of water and a column of air is subsequently forced through the water column towards the momentarily sealed valve. Once the air column reaches the valve, the water supporting the valve is displaced and the valve is released until the air column is replaced by another rising water column. This displacement of air through the water column causes the valve to 'shuttle' between open and closed positions as the alternating rising water and air pocket engages the valve so that sub-atmospheric pressure in the collection chamber is maintained and excess negative pressure is relieved.