Patent ID: 7722557

Claim:
A blood purification apparatus comprising: a blood purifier and a blood circuit connected to the blood purifier and having an arterial-side blood circuit on an upstream side of the blood purifier and a venous-side blood circuit on a downstream side of the blood purifier, a blood pump provided in the blood circuit, a priming liquid feed line connected to the, blood circuit, a venous-side air trap provided in the venous-side blood circuit, an opening-closing valve provided in the venous-side blood circuit on the downstream side of the venous-side air trap, a dialysate circuit connected to the blood purifier, a dialysate pump and filtering pump provided in the dialysate circuit, and a pressure gauge provided in the dialysate circuit and arranged between the dialysate pump and the filtering pump, configured such that a strain sensor is provided on an outer wall of a body portion of the venous-side air trap, the strain sensor comprising a load sensor and a load transmitter with the load transmitter being in hermetical contact with the outer wall of the body portion of the venous-side air trap so that the strain of an outer wall of a body portion of the venous-side air trap resulting from a force exerted onto the internal surface of the venous-side air trap is sensed by the load transmitter and is transmitted to the load sensor via the load transmitter and measured, thereby measuring the pressure in the venous-side blood circuit, configuration such that the strain sensor is calibrated by using the head between the pressure gauge and the strain sensor, and by using a pressure measured by the pressure gauge.