EVALUATION OF A TRANSIT-TIME SYSTEM FOR THE CHRONIC MEASUREMENT OF BLOOD-FLOW IN CONSCIOUS SHEEP

Abstract

The accuracy of transit-time ultrasonic flow probes for measurement of regional blood flow and cardiac output was evaluated after long-term implantation in sheep. Transit-time flow probes (3, 4, 6, and 20 mm) accurately measured flow in vitro. Recalibration in vivo demonstrated that this accuracy was maintained after 1-9 mo of implantation on the left circumflex coronary (3-mm probe), cranial mesenteric (6-mm probe), left renal (4-mm probe), and left external iliac (6-mm probe) arteries of sheep. The flow probes also showed good zero stability. However, a transit-time flow probe (20 mm) chronically implanted on the pulmonary trunk significantly underestimated cardiac output compared with the..