Patent ID: 7131957

Claim:
A device for an extracorporeal blood treatment machine of the type that includes an exchange unit divided into first and second chambers by a semipermiable membrane, the device comprising: a safety device comprising: a measuring device for measuring a transmembrane pressure TMP m of the exchange unit; an establishing device for establishing at least one of an upper limit transmembrane pressure L 1 and a lower limit transmembrane pressure L 2 , the establishing device including a computer unit configured to continuously calculate a transmembrane pressure TMP c at a preset ultrafiltration rate UFR and to continuously calculate the at least one of the upper limit transmembrane pressure L 1 and the lower limit transmembrane pressure L 2 on the basis of the calculated transmembrane pressure TMP c , wherein the computer unit is configured to calculate the transmembrane pressure TMP c at the preset ultrafiltration rate UFR from the quotient of the preset ultrafiltration rate UFR and an ultrafiltration coefficient UFK; and a means for comparing the measured transmembrane pressure TMP m with the at least one of the upper limit transmembrane pressure L 1 and lower limit transmembrane pressure L 2 ; and an ultrafiltration device configured to remove ultrafiltrate from the exchange unit at an ultrafiltration rate, the ultrafiltration device including a means for varying the ultrafiltration rate during a blood treatment.