What is the term "safety factor" in regards to when dealing with pulmonary edema?
The primary cause of PE is elevated pulmonary capillary pressure (from cardiac failure).
For edema to occur, capillary bp must rise 2-3 mmHg above colloid osmotic pressure.
Because normally capillary P is 8 mmHg while colloid osmostic is 28 mmHg, there existst a 23 mmHg buffer before edema will occur.
This buffer region not only means capillary P has to climb a long way, but because it would take longer to rise above the buffer, the lymphatic system has more to compensate (by inc flow)