IN-VIVO VALIDATION OF A TRANSIT-TIME ULTRASONIC VOLUME FLOW METER

The objective of this investigation was to validate a transit-time ult rasound blood flow metering system in vivo. Implanted chronically and acutely on the ascending aorta of the dog, the transit-time flow probe determined varying flow rates simultaneously with measurements made b y the electromagnetic flow metering method The transit-time technique was also compared to two methods in which blood was collected volumetr ically by either graduated cylinder (ascending aorta/dog) or pump with drawal (abdominal aorta/cat). Statistical analysis of the results prov ided evidence that the transit-time ultrasound method measured in vivo blood flow rate no differently than the electromagnetic or pump withd rawal techniques, however, transit-time determinations of blood volume were 10% below that indicated by graduated cylinder collection. With transit time represented on the y-axis, three linear regressions of al l paired blood flow measurements were calculated yielding the followin g slopes (Delta y/Delta x) and regression coefficients (r), respective ly: electromagnetic (1.00, 0.98), graduated cylinder (0.85, 0.93), and pump withdrawal (0.93, 1.00). The results validate the transit-time u ltrasound system used in the present investigation as an accurate meth od capable of measuring blood flow in both acutely and chronically ins trumented animal preparations.