On-line cardiac output by digital computer

Area of Science:

• Cardiovascular Physiology
• Medical Instrumentation
• Computational Biology

Background:

• Conventional cardiac output devices often deviate from the Stewart-Hamilton method, leading to significant errors.
• Accurate measurement of cardiac output is crucial for diagnosing and managing various cardiovascular conditions.

Purpose of the Study:

• To develop and validate an on-line computer system for precise cardiac output calculation using the classical Stewart-Hamilton method.
• To address and mitigate errors introduced by common assumptions in existing cardiac output measurement devices.

Main Methods:

• Implemented a digital filter to smooth dye-dilution curves and eliminate heartbeat noise.
• Utilized the exponential property of recirculation for accurate removal.
• Developed quality control metrics including baseline length, exponential fit, and a figure of merit based on the five tanks-in-series model.

Main Results:

• The on-line system demonstrated high accuracy, with a mean difference of only 150 ml compared to hand calculations.
• For simulated dye curves, the computer system achieved a standard deviation of 10 ml, significantly outperforming hand calculations (SD = 200 ml).
• Visual checks via CRT display of curves and parameters ensured data integrity.

Conclusions:

• The developed on-line system provides a reliable and accurate method for cardiac output determination via dye-dilution.
• This system offers a significant improvement in precision and error reduction compared to traditional methods and manual calculations.