2022-07-012022-07-011957195713695820https://hdl.handle.net/10657/10298Plethysmography, or volume recording, plays an important part in the evaluation of circulation in human patients. There are several techniques used: indirect mechanical methods involving fluid displacement; indirect photoelectric methods involving transmission and/or reflection of light; indirect electrical methods Involving the correlation of impedance changes with blood volume changes. The impedance plethysmograph is evaluated in this paper with respect to carrier frequency and electrode characteristics. A comparison is made between measured results and values predicted on the basis of physical analyses of tissue impedance. It is shown that volume variations may be reproduced by direct air volume displacement measurements and by impedance measurements at frequencies of 100, and 175 kilo-cycles per second. Special techniques and calculations are demonstrated whereby the impedance plethysmograph may be used for quantitative measurement of blood flow rates, pulse volumes, elasticity of vessels and circulation times.application/pdfenThis item is protected by copyright but is made available here under a claim of fair use (17 U.S.C. Section 107) for non-profit research and educational purposes. Users of this work assume the responsibility for determining copyright status prior to reusing, publishing, or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions requires express permission of the copyright holder.Thesisreformatted digital