Abstract: A method for determining a cardiac function, comprising (i) determining base anatomical characteristics associated with the subject, (ii) determining pulse delay to a first body site (PD01) and a second body site (PD02) as a function of the anatomical characteristics, wherein the distance via the arterial tree from the aortic valve to the first body site (PD01) is different than the arterial tree distance from the aortic valve to the second body site (PD02), (iii) determining pulse wave velocity between the first body site and the second body site (PWV12), (iv) determining pulse wave velocity between the aortic valve and the first body site (PWV01) as a function of PWV12, and the anatomical characteristics; and (v) determining the pre-ejection period (PEP) as a function of PD01 and PWV01.

Abstract: A method for determining a physiologic characteristic associated with cardiac function in a subject comprising the steps of providing at least one electromagnetic radiation absorption measurement, providing demographic information reflecting the subject's physical condition, determining a temporal plethysmographic value from the electromagnetic radiation absorption measurement, and determining at least one physiologic characteristic from the temporal plethysmographic value and demographic information by using a predetermined phenomenological model that is adapted to provide an estimate of a blood volume-time relationship proximate the heart and compute at least one physiologic characteristic associated with cardiac function based on the estimated blood volume-time relationship.

Abstract: Improved methods and apparatus for non-invasively assessing one or more parameters associated with fluidic systems such as the circulatory system of a living organism, when such parameters are potentially affected by other concurrent events. In one exemplary embodiment, apparatus and methods for compensating for occlusive events (e.g., pressure cuff inflation) occurring ipsilateral to the location of parameter measurement are disclosed. Upon passive detection of signal degradation resulting from the event, the apparatus selectively enters a “wait state” wherein further processing of the hemodynamic data is suspended until the degrading event subsides. This behavior mitigates any adverse effects the event might have on the accuracy of the representation of the measured hemodynamic parameter generated by the system. In another exemplary embodiment, the measured data is analyzed in order to classify the type of event (e.g.

Abstract: Improved methods and apparatus for non-invasively assessing one or more parameters associated with fluidic systems such as the circulatory system of a living organism. In a first aspect, an improved method of continuously measuring pressure from a compressible vessel is disclosed, wherein a substantially optimal level of compression for the vessel is achieved and maintained using perturbations (e.g., modulation) of the compression level of the vessel. In one exemplary embodiment, the modulation is conducted according to a pseudo-random binary sequence (PBRS). In a second aspect, an improved apparatus for determining the blood pressure of a living subject is disclosed, the apparatus generally comprising a pressure sensor and associated processor with a computer program defining a plurality of operating states related to the sensed pressure data. Methods for pressure waveform correction and reacquisition, as well as treatment using the present invention, are also disclosed.

Abstract: An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter (e.g., arterial blood pressure) by applanating or compressing portions of tissue proximate to the blood vessel of concern until a desired condition is achieved, and then measuring the hemodynamic parameter. Such applanation effectively mitigates transfer and other losses created by the tissue proximate to the blood vessel, thereby facilitating accurate and robust tonometric measurement. An algorithm adapted to maintain optimal levels of applanation is also described. Methods and apparatus for scaling such hemodynamic parameter measurements based on subject physiology, and providing treatment to the subject based on the measured parameters, are also disclosed.

Abstract: Improved apparatus and methods for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises apparatus adapted to accurately place and maintain a sensor (e.g., tonometric pressure sensor) with respect to the anatomy of the subject, including an alignment apparatus which is separable from an adjustable fixture. The alignment apparatus moveably captures the sensor to, inter alia, facilitate coupling thereof to an actuator used to position the sensor during measurements. The alignment apparatus also advantageously allows the sensor position to be maintained when the fixture is removed from the subject, such as during patient transport. Methods for positioning the alignment apparatus and sensor, correcting for hydrostatic pressure effects, and providing treatment to the subject are also disclosed.

Abstract: Improved methods and apparatus for non-invasively assessing one or more parameters associated with fluidic systems such as the circulatory system of a living organism, when such parameters are potentially affected by other concurrent events. In one exemplary embodiment, apparatus and methods for compensating for occlusive events (e.g., pressure cuff inflation) occurring ipsilateral to the location of parameter measurement are disclosed. Upon passive detection of signal degradation resulting from the event, the apparatus selectively enters a “wait state” wherein further processing of the hemodynamic data is suspended until the degrading event subsides. This behavior mitigates any adverse effects the event might have on the accuracy of the representation of the measured hemodynamic parameter generated by the system. In another exemplary embodiment, the measured data is analyzed in order to classify the type of event (e.g.

Abstract: Apparatus is disclosed for non-invasively monitoring a subject's blood pressure, in which a pressure sensor assembly that includes a pressure transducer is compressed against tissue overlying an artery, with sufficient force to compress the artery. A motor first servo control system optimizes the amount of artery compression, which occurs at a mean transmural pressure of about zero, by modulating one side of a lever arm compressing the assembly against the tissue, creating a pressure signal indicative of transmural pressure. Since different pressure effects are realized according to the amount of artery compression, an appropriate control signal can be produced that provides for a second motor to adjust the other side of the lever arm to provide the optimum compression of the assembly into the tissue overlying the artery. The apparatus is optimally positioned over an artery by including an ultrasonic blood flow sensor configured to sense the flow of blood under the pressure transducer.

Abstract: Apparatus is disclosed for non-invasively monitoring a subject's blood pressure, in which a pressure sensor assembly that includes a pressure transducer is compressed against tissue overlying an artery, with sufficient force to compress the artery. A motor first servo control system optimizes the amount of artery compression, which occurs at a mean transmural pressure of about zero, by modulating one side of a lever arm compressing the assembly against the tissue, creating a pressure signal indicative of transmural pressure. Since different pressure effects are realized according to the amount of artery compression, an appropriate control signal can be produced that provides for a second motor to adjust the other side of the lever arm to provide the optimum compression of the assembly into the tissue overlying the artery. The apparatus is optimally positioned over an artery by including an ultrasonic blood flow sensor configured to sense the flow of blood under the pressure transducer.

Abstract: Apparatus is disclosed for non-invasively monitoring a subject's blood pressure, in which a flexible diaphragm that encloses a fluid-filled chamber is compressed against tissue overlying an artery, with sufficient force to compress the artery. A first, relatively slow servo control system optimizes the amount of artery compression, which occurs at a mean transmural pressure of about zero, by modulating the volume of fluid within the chamber and noting the resulting effect on the pressure within the chamber. Since different pressure effects are realized according to the amount of artery compression, an appropriate control signal can be produced that provides the optimum mean diaphragm pressure. In addition, a second, relatively fast servo control system supplies the fluid to and from the chamber, so as to compensate for pressure variations within artery.

Abstract: Apparatus is disclosed for non-invasively monitoring a subject's blood pressure, in which a flexible diaphragm that encloses a fluid-filled chamber is compressed against tissue overlying an artery, with sufficient force to compress the artery. A first, relatively slow servo control system optimizes the amount of artery compression, which occurs at a mean transmural pressure of about zero, by modulating the volume of fluid within the chamber and noting the resulting effect on the pressure within the chamber. Since different pressure effects are realized according to the amount of artery compression, an appropriate control signal can be produced that provides the optimum mean diaphragm pressure. In addition, a second, relatively fast servo control system supplies the fluid to and from the chamber, so as to compensate for pressure variations within artery.

Abstract: A pumping mechanism moving in movement increments is controlled to space those movement increments in direct proportion to the volume resulting from each movement increment. In a further aspect, movement increments are grouped to result in approximately equal volumes per group. The mechanism moves continuously through the movement increments in each group. Groups are spaced to result in approximately equal flow volumes per group. The number of groups decreases as the flow rate increases. The number of movement increments in each group and the volume of each group increase as the flow rate increases.

Abstract: Impedance to fluid flow in a fluid delivery line is measured. Two techniques are used depending on the flow rate selected. For high flow rates, the pump is controlled to vary the flow rate and the change in pressure is divided by the change in flow to directly determine the resistance. For low flow rates, a processor controls the pump to pump flow quantities in accordance with a pseudo-random binary code. The resulting pressure signal sensed at the conduit is decoded in accordance with that code. Pressures received during code periods of no flow are subtracted from pressures received during code periods of flow. Pressure offset is also removed and a least squares estimation approach is used with a linear prediction model to determine impedance. The coefficients determined in the model are used to calculate the resistance to fluid flow of the system. A quality supervisor monitors the resistance determination process and controls the display of resistance depending on the quality determined.