Apparatus and method for non-invasive and minimally-invasive sensing of parameters relating to blood

Abstract

Medical diagnostic system, apparatus and methods are disclosed. Optical transmitters generate radiation-containing photons having a specific interaction with at least one target chromophore in a target structure, preferably a blood vessel such as the interior jugular vein. The optical transmitters transmit the radiation into at least a first area including a substantial portion of the target structure and into a second area not including a substantial portion of the target structure. Optical receivers detect a portion radiation scattered from at least the first area and the second area. A processor estimates oxygenation, pH or cardiac output based on the scattered radiation detected from the first area, and the scattered radiation from the second area.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is related to co-pending U.S. patent application Ser. No. 11 / 095,091, filed 30 Mar. 2005, in the name of John F. Black, Daniel Hwan Kim, and Butrus T. Khuri-Yakub, entitled “Apparatus and Method for Non-Invasive and Minimally-Invasive Sensing of Venous Oxygen Saturation and pH Levels”, which is hereby incorporated by reference as if fully set forth herein.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention is related to techniques for monitoring vital bodily functions, including cardiac output. It relates in particular to methods and apparatus for non-invasive and minimally-invasive real-time monitoring of parameters such as venous oxygenation saturation or pH in a vessel, an organ or tissue containing blood.[0004]2. Description of the Related Art[0005]Cardiac output is defined as the volume of blood circulated per minute. It is equal to the heart rate multiplied by the stroke volume (the amount...

AI Technical Summary

Benefits of technology

"The present invention provides a system and method for non-invasively measuring various parameters relating to blood, such as oxygen saturation levels and cardiac output, in the body. The system includes optical transmitters and receivers that are positioned on the skin of the patient and transmit and detect photons that interact with a target chromophore in a target structure, such as a blood vessel. The system can estimate these parameters based on the scattered radiation detected from the first and second areas, and does not require the use of ferromagnetic materials in construction. The method is quick and does not require extensive post-processing of the data. The invention can also be combined with ultrasound to enhance the accuracy of the monitoring. The system and method can provide accurate and early diagnostic and therapeutic decisions for physicians."

Problems solved by technology

Many new methods have attempted to replace the thermodilution technique, but none have so far gained acceptance.

It is generally considered the most accurate method currently available, although there are many possibilities of introducing errors, and considerable care is needed.

However when using the Fick method to trend cardiac output over a short time interval, i.e. during an operation or in an intensive care unit stay, many of these sources of errors are no longer pertinent.

Studies have been reported with mostly poor results, but in exceptional cases good correlations compared to a reference method.

The accuracy of this technique is increased when the electrodes are placed directly in the left ventricle, rather than on the chest, however this also increases its invasiveness.

However, in clinical settings, the lower precision of the continuous cardiac output techniques may be outweighed by their advantages of being automatic and continuous.

Unfortunately, measurements from such oxygen monitors cannot be reliably correlated to oxygenation in the patient's venous blood.

Imaging the speckle resulting from trajectory changes requires significant computation power and post-processing to yield an image.

The technique has limited resolution, and is not yet capable of yielding functional (oxygenation) information in a fast flowing vessel.

In addition, the frequency shift can be to both larger and smaller frequency of the initial carrier wave, and therefore some self-cancellation may result.

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