| 摘要 |
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 ballon. 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 blood velocity. 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 is determined from the two measured velocities and from the predetermined cross-sectional 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. |
