Non-invasive uterine activity sensor

Details Non-invasive uterine activity sensor Non-invasive uterine activity sensor

1999-02-26

2001-01-02

Lateef, Marvin M. (Department: 3737)

Surgery

Diagnostic testing

Measuring or detecting nonradioactive constituent of body...

C600S476000

Utility Patent

active

06169913

ABSTRACT:

CROSS REFERENCE TO RELATED PROVISIONAL APPLICATION
This application claims the benefit under 35 USC §119(e) of U.S. Provisional Application No. 60/002,674, filed Jun. 20, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the non-invasive sensing, detecting, and/or monitoring of uterine activity, including uterine contractions.
2. Description of the Prior Art
Tocodynamometers have been and are being used to non-invasively monitor uterine contractions. Such devices mechanically sense the hardness of the abdominal wall. These devices suffer from a number of problems, the primary one of which is that they provide relative data which in many cases does not reflect the actual intensity of uterine contractions. Also, the devices are large, require belts for attachment to the patient. and are sensitive to movement of the device relative to the patient's abdomen.
SUMMARY OF THE INVENTION
In view of the foregoing it is an object of the present invention to provide improved methods and apparatus for sensing uterine activity.
To achieve this and other goals, the invention provides an optical method for sensing uterine activity and apparatus for practicing that method. In accordance with the invention, light of one or more wavelengths is applied to the patient's abdomen from a suitable source or sources and light modulated by the tissues and blood of the patient (referred to hereinafter collectively as the “tissues”) is detected by one or more sensors. As described below, it has been found that uterine activity modulates the applied light such that time variations in the detected light correspond to uterine activity and thus can serve to monitor such activity.
In certain preferred embodiments of the invention, light of a single wavelength is used. The wavelength can be selected from any part of the spectrum. Preferably, the wavelength is in a range where the absorptions of at least some of the hemoglobin fractions of the blood are similar. In particular, a wavelength in the range where the absorptions of the major hemoglobin fractions are similar is preferred, e.g., a wavelength in the range where the absorptions of oxyhemoglobin and deoxyhemoglobin are similar. For example, a light source having a wavelength of about 500-600 nm or about 800 nm can be used.
In other preferred embodiments of the invention, light of two wavelengths is used, and the output signal for monitoring uterine activity is based on a comparison between the detected light at the two wavelengths. The two wavelengths can be selected from any part of the spectrum. As in the one wavelength embodiments, one or both of the two wavelengths can be from a region of the spectrum where the absorptions of the various hemoglobin fractions of the blood, in particular, the oxyhemoglobin and deoxyhemoglobin fractions, are similar.
The one wavelength embodiments allow for detection of uterine activity. The two wavelength embodiments can be used for the same purpose and can improve the reliability of the system by eliminating unwanted artifacts such as baseline drift. More than two wavelengths can be used if desired to even further refine the analysis.


REFERENCES:
patent: 4281645 (1981-08-01), Jobsis
patent: 4967761 (1990-11-01), Nathanielsz
patent: 5277181 (1994-01-01), Mendelson et al.
patent: 5494032 (1996-02-01), Robinson et al.

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