Method and device for measuring parameters of cardiac function

Abstract

A device for non-invasively measuring parameters of a cardiac blood vessel in a patient is provided. The device comprises at least one light source that emits light in the 400 nm to 1000 nm wavelength range and at least one photodetector adapted to receive light emitted by the light source, which light is reflected from or transmitted through tissue of the patient, the output of said photodetector correlating with a parameter of the blood vessel. The device also includes a probe which permits delivery of light from the light source to an external tissue site on the patient in the proximity of a cardiac blood vessel and permits the photodetector to receive light originating from the light source which has been reflected from or transmitted through tissue at the patient site.

Description

FIELD OF THE INVENTION[0001]The present invention is related to techniques for monitoring vital functions of the human body, including cardiac functions such as cardiac output and central venous blood oxygenation. It relates, in particular, to an optical method and device for the non-invasive and continuous monitoring of cardiac parameters such as blood flow, blood volume and blood oxygen saturation.BACKGROUND OF THE INVENTION[0002]The evaluation of jugular venous pulse has been an integral part of cardiovascular examination and has important clinical diagnostic values [1-2]. Jugular venous pulse is produced by the changes in blood flow and pressure in central veins caused by right atrial and ventricular filling and contraction. The two main objectives of the bedside examination of jugular vein pulse include the estimation of central venous pressure and the inspection of the waveform. Because of its more direct route to the right atrium, the right internal jugular vein is superior f...

AI Technical Summary

Benefits of technology

[0015]The present invention provides a device and method by which cardiac output can be continuously monitored

Problems solved by technology

It may also result from vena caval obstruction and, at times, an increase blood volume.

The venous pressure is measured by a ruler as the vertical distance from the top of the oscillating venous column, to the level of the sternal angle plus vertical distance to the right atrium Due to the fact that the venous pulse is in generally very small, and due to complications with patients, this method is challenging for physicians to use and provides approximate values only.

As this technology is highly invasive, complicated, and expensive, many new methods have been developed in an attempt to replace it, but none have so far gained acceptance.

This method shows a lack of agreement between thermodilution and CO2-rebreathing cardiac output as described in Nielsson et al [12], due to unknown ventilation / perfusion inequality in patients.

Studies have been reported with mostly poor results, but in some exceptional cases, there was good correlation with a reference method.

Because of the highly scattering nature of tissue to the visible and near infrared light (400 nm-1000 nm), it is difficult to apply diffuse optical spectroscopy non-invasively to select blood vessels within a tissue to calculate blood oxygenation.

None of the above-mentioned techniques of measuring cardiac output combines all of the eight “Jansen” criteria mentioned above and, thus, none can displace the conventional thermodilution technique as described by Jansen et al [18].

Although highly invasive, complicated and expensive, the conventional thermodilution method remains the method of choice for measuring cardiac output.

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