| 摘要 |
<p>VOLUMETRIC FLOW RATE DETERMINATION IN CONDUITS NOT DIRECTLY ACCESSIBLE A catheter, particularly adapted for cardiac output determination, comprises an elongated tube of flexible material, the tube having a substantially rigid distal portion on which is disposed an ultrasonic transducer and a proximate; inflatable balloon. The ultrasonic transducer is arranged so as to direct a beam of ultrasound toward a transverse plane that bisects the balloon, and is connected by appropriate leads to a conventional Doppler circuit. With the balloon deflated, the signal from the Doppler circuit is sensed to measure bloodvelocity. Thereafter, the balloon is inflated so that it has a predetermined cross-sectional area in the transverse plane. The signal from the Doppler circuit is again sensed to measure blood velocity. Using a simple mathematical relationship, the effective internal cross-sectional area of the blood vessel isdetermined from the two measured velocities and from the predetermined crosssectional area of the balloon when inflated. The volumetric flow rate is then determined by multiplying the first measured velocity by the effective internal cross-sectional area.</p> |
