RESUMO
In this paper, the limitations of the conventional formula for the computation of peripheral blood flow from impedance plethysmograms are highlighted, and a correction to the formula is suggested. A conductivity cell experiment is described to show the dependence of the value of the blood flow index (BFI), obtained from the conventional formula, on the mean resistivity of the cell. It is also shown that the value of the corrected BFI is independent of the mean resistivity. Anomalies observed in the amplitude of systolic waves in impedance plethysmograms of patients with oedema are explained.
Assuntos
Perna (Membro)/irrigação sanguínea , Pletismografia de Impedância/métodos , Fluxo Sanguíneo Regional , Adulto , Edema/fisiopatologia , Reações Falso-Positivas , Humanos , Matemática , Pessoa de Meia-Idade , Valores de ReferênciaRESUMO
Impedance Plethysmography technique has been discussed with explanation of two compartment model and parallel conductor theory for the estimation of peripheral blood flow and stroke volume. Various methods for signal enhancement to facilitate computation of blood flow are briefly described. Source of error in the estimation of peripheral blood flow is identified and the correction has been suggested.
Assuntos
Pletismografia de Impedância , Humanos , Perna (Membro)/irrigação sanguínea , Modelos Cardiovasculares , Fluxo Sanguíneo Regional/fisiologia , Volume Sistólico/fisiologiaRESUMO
This paper describes the basic methods for measurement of body impedance, electrodes and their configuration, and the measuring instrument with its limitations. A microcomputer assisted impedance plethysmograph system, developed at BARC and different lead configurations for impedance plethysmographic investigation are also described. Typical impedance plethysmographic waveforms recorded from a normal subject and measurement of their amplitude and various time intervals are illustrated.
