APPARATUS AND METHODS FOR THE NONINVASIVE MEASUREMENT OF CARDIOVASCULAR SYSTEM PARAMETERS
 Inventors: Steven P. Petrucelli, Cranbury; Walter Welkowitz, Metuchen; Lisa K. Liss, Dunellen; Alan M. Smith, East Brunswick; Stephen A. Orbine, HI,
Bernardsville, all of N.J.
 Assignee: Rutgers University, New Brunswick, N.J.
 Appl. No.: 317,927
 Filed: Oct. 4,1994
 Int. CI.6 A61B 5/00
 U.S. CI 128/672; 128/671; 128/713;
 Field of Search 128/668, 670,
128/672, 687, 690-694, 702, 661.08
 References Cited
U.S. PATENT DOCUMENTS
4,899,758 2/1990 Finkelstein et al 128/672
4,993,420 2/1991 Welkowitz et al. .
5,054,493 10/1991 Cohn et al 128/672
5,101,828 4/1992 Welkowitz et al. .
5,211,177 5/1993 Chesney et al. .
5,316,004 5/1994 Chesney et al 128/668
5,400,793 3/1995 Wesseling 128/691
M. Yelderman, "Continuous Measurement of Cardiac Output with the Use of Stochastic System Identification Techniques", J. Clin. Monit 6:322-332, 1990.
Apparatus and methods for noninvasively measuring cardiovascular system parameters. According to a first preferred embodiment, the apparatus generates a time varying electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject, the parameters being modelled by a lumped element electric circuit model analogous to the living subject's cardiovascular system, said circuit model including a systolic capacitor analogous to arterial compliance during systole, said apparatus comprising means for computing the value of said systolic capacitor from a measurement of an elapsed time between two voltage levels within a portion of said voltage waveform corresponding to systole, according to a predetermined criteria; and means for computing at least one said cardiovascular system parameter from said capacitor value. According to a second embodiment, a time-varying systolic arterial compliance is measured by measuring an arterial pulse pressure waveform. A third embodiment discloses a method of measuring cardiac output noninvasively from a cuff measurement of a patient's systolic minus diastolic blood pressure and a heart rate measurement. Cardiac output equations are derived from an unmodified Windkessel circuit model which models arterial compliance as a single lumped capacitance. General formulas for the value of the lumped capacitance are provided which are used to more accurately compute cardiac output from this circuit model.
15 Claims, 10 Drawing Sheets