Blood vol. absolute measurement - using extracorporeal plasma filter to abstract predetermined wt. of plasma only while consequent change in concn. of haemoglobin is measured

摘要

Blood is pumped (2) from an artery into the extracorporeal circuit (1) where haemoglobin concn. is measured (3) and plasma is filtered (4) via a reversing valve (6) and another pump (7) into a flask (9) hanging from a spring balance (10). At a predetermined filling (e.g. 300 ml) a signal is sent (11) to an electric control circuit (12) and computer (13). An absolute vol. is deduced from the quotient of the plasma vol. and the measured percentage variation in haemoglobin concn.. ADVANTAGE - Measurements can be made at relatively short intervals with min. errors by inexpensive device using no radioactive substances.