The positive pressure valve provides a small positive push with disconnection.  It does not provide continual positive pressure.  The air eliminating valve on an inline filter is just that.  It comes into play primarily during priming.  As the filter is filled with solution air vents out through the air eliminating valve.  Also if a small amount of air enters the filter after priming it eliminates this.  If for some reason the filter becomes filled with air, the air acts as a lock preventing flow.  It is the fluid that helps push the air out of the filter.  The filter has NO impact on the connector.  No matter whether you use a filter or not the positive push from the connector is a momentary event.   In addition to develop this push at the end a similar volume of blood is refluxed into the connector with connection.  This occurs because for every action there must be an equal opposite reaction.  Positive push at the end requires a negative event at the beginning. 
 
Denise Macklin

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