WO2001003598A1 - Naso-gastric reflectance spectroscopy probe - Google Patents

Abstract

A naso-gastric reflectance spectroscopy probe. The probe includes an elongated flexible tube for insertion into a tubular body structure. The tube has a distal end with a lumen and suction apertures. One or more send and receive optical fibers extend through the lumen and have distal ends which terminate on the side of the tube near the distal end. Proximal ends of the optical fibers are adapted to be connected to a spectroscopy instrument. When positioned in a patient's stomach through the esophagus, a vacuum can be drawn through the tube to cause the optical fibers to be positioned in measurement contact with the tissue.

Description

NASO-GASTRIC REFLECTANCE SPECTROSCOPY PROBE

FIELD OF THE INVENTION

The present invention is a spectroscopy probe In particular, the present invention is a reflectance spectroscopy probe which can be used to monitor tissue in a patient's esophagus and stomach

BACKGROUND OF THE INVENTION

Reflectance spectroscopy and other spectrophotometπc-type medical instruments are known and used in a variety of applications An instrument of this type is, for example, disclosed in the Anderson et al U S Patent 5,879,294 Briefly, the instrument shown in the Anderson et al patent includes an optical probe which is releasably connected to an electronics package In operation, the probe is positioned on the tissue to be measured or analyzed The probe is interfaced to the instrument electromcs through optical fibers and a probe connector Light emitting diodes (LEDs) or other light sources in the instrument generate light at a number of different wavelengths The light used to measure the characteristics of the tissue is coupled to the probe by one or more send optical fibers After being transmitted from the tissue-engaging surface of the probe into the tissue being measured, the light will travel through the tissue before being collected at the end of the receive optical fiber This collected light is then transmitted to the instrument through the probe connector and electronics package connector The instrument also produces and transmits directly to the electronics package a reference light signal corresponding to each of the measurement light signals (1 e , the reference light signals are not transmitted through the tissue)

Other embodiments of spectrophotometπc instruments (not shown) include LEDs, broadband or other light sources mounted within the electronics package or monitor Probes used in connection with monitors of this type have optical connectors on the ends of the fibers opposite the tissue-engaging surface The optical connectors mate with associated connectors on the monitor to couple the light between the monitor and probe tip In other instruments of this type, the LEDs or other light sources are mounted withm the optical connector portion of the probe

The collected measurement light signals and reference light signals received by the electronics package are transmitted to a detector which produces electrical signals representative of these light signals at each wavelength of interest A processor/controller then processes these signals to generate data representative of the measured tissue parameter The measurement can be visually displayed on a display Algorithms used to compute the tissue parameter data are generally known and described m the Anderson et al patent

The use of reflectance spectroscopy techniques to analyze tissue in a patient's stomach or other internal body portions would be efficacious Probes of the type described above, however, are not suitable for applications of this type There is, therefore, a continuing need for improved reflectance spectroscopy probes

SUMMARY OF THE INVENTION

The present invention is an improved probe for use with a spectrophotometπc instrument One embodiment of the probe includes an elongated flexible tube for insertion into a tubular body structure The tube has a distal end and one or more send and receive optical fibers which extend through the tube The send and receive fibers have ends which terminate on the side of the tube near the distal end In one particularly efficacious embodiment of the invention, the tube is a naso-gastπc tube adapted to be inserted into a patient's stomach and esophagus, and includes suction apertures on the distal end When positioned in the patient's stomach, a vacuum can be drawn through the tube to cause the send and receive optical fibers to be positioned in measurement contact with the tissue BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an illustration of a naso-gastπc reflectance spectroscopy probe in accordance with the present invention

Figure 2 is a detailed cross sectional view of a portion of the tip of the probe shown in Figure 1

Figures 3-6 are detailed views of the fiber tip shown in Figure 2

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A naso-gastπc reflectance spectroscopy probe 20 in accordance with the present invention which can be used to analyze tissues in the stomach and esophagus of a patient is illustrated generally in Figures 1 and 2 As shown, the probe 20 includes a flexible tube 22 having a tip 24 on its distal end 26 The tip 24 includes a plurality of suction apertures 28 which extend through the tip 24 into a suction lumen 30 within the tip 24 and tube 22 At the proximal end 32 of the tube 22 the suction lumen 30 is connected to a vacuum source connector 34 A fiber tip 36 is mounted in one of the suction apertures 28 Alternatively, the fiber tip 36 can be mounted in a hole added to the probe 20 and adapted specifically for receiving the fiber tip 36

One or more send optical fibers 38 and receive optical fibers 40 (one of each are shown in the illustrated embodiment) extend through the tube 22 and tip 24 of the probe 20 At the proximal end 32 of the tube 22 the send and receive fibers 38 and 40 extend from the tube 22 and can be coupled by connectors (not shown) to the monitor of a spectroscopy system (also not shown) At the distal end 26 of the tube 22, the ends of the send and receive fibers 38 and 40 are mounted in the fiber tip 36 with their end faces 42 and 44, respectively, generally flush with the outer surface 46 of the probe tip 24 Alternatively, side-firing optical fibers or mirrors (not shown) can be incorporated into the probe 20 to couple light between the end faces 42 and 44 of fibers 38 and 40, respectively, and the tissue being analyzed Commercially available naso-gastπc tubes can be used for the tube 22 and tip 24 of the probe 20 A 14 French naso-gastπc tube from Davol (model no 0042140) was used for one embodiment of the invention The send and receive fibers 38 and 40 extend from the fiber tip 36 through a fiber lumen 48 The fiber tip 36 is positioned in a suction aperture 28 near the distal end 26 of the probe tip 24 so the remaining suction apertures 28 remain fluidly connected to the vacuum source connector 34 Figures 3-6 are detailed illustrations of the fiber tip 36

During use, the naso-gastπc probe 20 is inserted into the patient's stomach through his or her nose The vacuum source connector is coupled to a vacuum source in a conventional manner, while the send and receive fibers 38 and 40 are connected to the instrument monitor When suction is applied to the probe 20, the probe tip 24, including the exposed end faces 42 and 44 of the send and receive fibers 38 and 40, will be drawn into engagement with the interior stomach wall Light from the send fiber 38 can then be effectively coupled into the stomach wall tissue Similarly, light that has been transmitted through the tissue can be effectively collected by the receive fiber 40 Insertion of the fibers 38 and 40 and fiber tip 36 into the tube 22 has minimal impact on the tube 22 itself and is considerably more efficacious than a larger tube having a blunt tip on its end

The naso-gastπc probe 20 can be manufactured by bonding (e g , with epoxy) the send and receive fibers 38 and 40 to the fiber tip 36 The end faces 42 and 44 of the send and receive fibers 38 and 40, respectively, can then be cleaved and polished on the side of the fiber tip 36 The fiber tip 36 is then installed and bonded (e g , with epoxy) in the tip 24 of the naso-gastπc tube 22 The fibers 38 and 40 are threaded through the lumen 48 of the tube 22 After connectors are mounted to the proximal ends 32 of the send and receive optical fibers 38 and 40, the fiber end faces 42 and 44 are polished

As noted above, the naso-gastπc reflectance spectroscopy probe 20 can be used to effectively illuminate and capture subsequent stomach tissue spectra Insertion of naso-gastπc tubes 22 through the nose and into the stomach of a patient is a medically accepted procedure With the invention, a clinician can monitor characteristics such as oxygen saturation levels in stomach tissue at the same time as the functions of the naso-gastπc tube 22 are being provided Due to their small diameter, the optical fibers 38 and 40 are readily incorporated into a lumen 48 of the tube 22 with minimal impact to its overall flexibility and primary functionality The ability to add fibers into a conventional naso-gastπc tube reduces the need for a second mechanism for deploying the send and receive fibers into the stomach

By polishing the send and receive fibers 38 and 40 flat along the side of the tube 22, the need to "bottom out" the tube tip 24 in the stomach cavity to force the end faces 42 and 44 of the fibers 38 and 40 into contact with the tissue is reduced Instead, the probe tip 24 need only reside along an mside surface of the stomach wall When the vacuum is initiated, the stomach wall will be drawn toward the tube 22, thereby providing the target site for tissue illumination and spectra capture The optical fibers 38 and 40 can be made from plastic for maximum flexibility (e g , 400μm in diameter) and coated with an opaque material to minimize cross-talk between send and receive channels

The invention can be effectively implemented in forms which differ from that described above For example, in other embodiments (not shown) of the invention the send and receive fibers are not bonded to a common tip The end faces of the send and receive fibers can then be spaced from one another by greater distances without the presence of a stiff holder extending between the fibers The number of send and receive fibers need not be limited to one each The effective upper limit on the number of fibers is a function of the diameter of the tube lumen through which the fibers extend and the concurrent reduction in the available suction or irrigation capability Multiple send and receive locations are possible, thereby enabling the monitoring of tissue oxygenation or other characteristics at multiple sites using the same probe Furthermore, depending on the spacing between the send and receive fibers, similar or different depths of the tissue can be monitored at the multiple sites The fiber tip can be located at the very distal end of the tube Glass fibers can be substituted for the plastic fibers Different size diameter fibers can be used at the expense of decreasing flexibility of the tube or a reduction in the strength of the send and receive signals The fibers and fiber tip can also be incorporated into intra-venous and intra-arterial catheters (e g , with smaller diameter fibers)

Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention

Claims

WHAT IS CLAIMED IS:

1 A probe for use with a photospectrometπc instrument, including an elongated flexible tube having a distal end, for insertion into a body structure, and one or more optical send and receive fibers extending through the tube and having ends terminating on the side of the tube

2 The probe of claim 1 wherein the tube is a naso-gastπc tube adapted to be inserted into a patient's stomach through the esophagus and including suction apertures on the distal end

3 The probe of claim 2 and further including a fiber fixture mounted in the distal end of thje tube for positioning the send and receive fibers at a suction aperture

4 The probe of claim 1 and further including a fiber fixture mounted in the distal end of the tube for positioning the send and receive fibers

5 A method for using reflectance spectroscopy to monitor tissue within a body cavity, including positioning a flexible tube having send and receive optical fibers on its side surface in the body cavity adjacent to the tissue to be monitored, and drawing a vacuum through the flexible tube to cause the send and receive optical fibers to be positioned in measurement contact with the tissue

6. A probe for use with a spectroscopy instrument, comprising: a flexible tube having a distal end for insertion into a tubular body structure, including: a suction lumen; and one or more suction apertures extending through the tube into communication with the suction lumen; and one or more optical send and receive fibers extending through the tube and having ends terminating on the side of the tube near a suction aperture.