Estimation of respiratory impedance and source pressure using a Thévenin equivalent circuit model

• Published in: Journal of biomechanics Vol. 16; no. 8; pp. 635 - 641
• Main Authors: Cha, E.J., Park, K.S., Lee, C.W., Kim, K.Y., Min, B.G.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1983; Elsevier Science
• Subjects: Airway Resistance; Biological and medical sciences; Biomechanics. Biorheology; Fundamental and applied biological sciences. Psychology; Humans; Lung Compliance; Male; Models, Biological; Pressure; Pulmonary Ventilation; Respiration; Tissues, organs and organisms biophysics; Biomechanics; Resistance; Impedance plethysmograph; Mechanic of breathing; Impedance; Mathematical model; Respiration; Pressure; Biomedical engineering
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/0021-9290(83)90113-6

The objective of this paper is to present a new technique which can provide both active respiration source pressure and lung impedance in a single noninvasive test. The method is based upon a Thévenin equivalent circuit model of respiratory mechanics. Using this model, the equivalent source pressure and source impedance can be computed from the measured changes of respiratory pressures and flows in two consecutive cycles before and after addition of purely resistive loads to the mouth. In maximal breathing the source parameters were reproducible in six normal human subjects. The total respiratory resistance during maximal breathing had an average value of 3.46 cmH 2O 1 −1 s −1, and the total dynamic compliance had an average value of 0.078 1 cmH 2O −1. The airway resistances measured using a plethysmographic method were within the range of 45–65% of the estimated total respiratory resistances. These two resistances were related with a correlation coefficient of 0.98. An average value of the magnitudes of the fundamental components of the source pressure was 6.73 cmH 2O during maximal breathing and 2.09 cmH 2O during spontaneous breathing.