Oximeter Sensor Assembly With Integral Cable and Method of Forming the Same

The invention arose during development efforts directed to providing a low cost oximeter sensor assembly with integral cable.

Oximeters are known in the art, and are used by anesthesiologists for continuous intraoperative noninvasive monitoring of arterial oxygen saturation of the patient under anesthesia, Anesthesiology News, Volume 13, Number 7, July 1987, pages 1, 66, 68 and 69, and also for neo-natal monitoring, and for various other uses. The oximeter provides a prewarning of hypoxia. A sensor having light emitting diodes and a light receiving element is placed around a finger tip, a toe, an ear lobe, the nose, etc. The effect of the patient's blood and its oxygen content on the intensity of light at a particular wavelength of light received by the light receiving element from the light emitting diodes gives a measure of the oxygen content in the blood, U.S. Pat. Nos. 4,621,643, 4,653,498, 4,685,464, 4,700,708, incorporated herein by reference.

The present invention provides an oximeter sensor assembly with integral cable. The assembly is characterized by low material cost, low assembly cost, suitability for high volume automated manufacturing as well as variable quantity manufacturing. The assembly provides a high degree of mechanical flexibility, and also offers full electromagnetic interference shielding if desired.

The invention offers a significant commercial advantage in that it reduces cost by a factor of 7. This 7:1 cost advantage makes the sensor assembly disposable, which is deemed highly desirable.

FIG. 1 is a perspective view of an oximeter sensor assembly known in the prior art.

FIG. 2 is a perspective view showing the inner construction of the assembly of FIG. 1.

FIG. 3 is a perspective view of an oximeter sensor assembly in accordance with the invention.

FIG. 4 is an end view showing an end of the assembly of FIGS. 1, 2 or 3 wrapped around a finger.

FIG. 5 is a sectional view taken along line 5--5 of FIG. 3.

FIG. 6 is a perspective view of one longitudinal end of the assembly of FIG. 3.

FIG. 7 is a perspective view showing connector structure for the assembly of FIG. 3.

FIG. 8 is a sectional view taken along line 8--8 of FIG. 7.

FIG. 9 is a sectional view like FIG. 5 and shows an alternate embodiment.

FIG. 10 is a sectional view like FIG. 5 and shows an alternate embodiment.

FIG. 11 is a sectional view like FIG. 5 and shows an alternate embodiment.

FIG. 1 shows an oximeter sensor assembly 12 having a cable 14 with an electrically insulating sheath 16 and a plurality of electrical conductors 18. The left end of the cable is connected by modular plug 20 to a patient adaptor plug 22 which is connected to an oximeter, for which further reference may be had to the above incorporated patents. The right end of the cable has a cover strap 24 which is flexibly wrapped at least partially around a finger tip 26 or other human body part. Electrical conductors 18 are connected to light emitting diodes 28 and to a light receiving electrical component 30. Light from LED's 28 passes upwardly through the finger to receiver 30. Blood oxygen content affects the light received at receiver 30, which is interpreted by the oximeter.

FIG. 2 shows the internal construction of the oximeter sensor assembly of FIG. 1. Conductors 18 are soldered at 32 to conductors 34 on electrically insulating substrate strip 36, to make connections to LED's 28 and light receiver 30. The electrical components and conductors on the substrate are covered by a thin transparent electrically insulating film 38 and then by cover strap 24. An electrically conductive shield 40 is around conductors 18 and has a shield contact connector 42 for grounding or the like connection to the oximeter, for shielding conductors 18 against electromagnetic interference, which can be a particular problem in the operating room.

The assembly of FIGS. 1 and 2 is expensive, both in material cost and in assembly cost. The assembly requires numerous manual operations.

FIG. 3 shows an oximeter sensor assembly 40 with integral cable 42 in accordance with the invention. Cable 42 is a thin elongated flexible sheet-like multi-layer strip having an integral end portion 44 flexibly wrapping at least partially around a human body part, such as finger 26. The cable includes a plurality of electrical conductors 46, 47, 48, 49, 50. Light emitting diodes 28a and light receiving electrical component 30a are mounted on the cable and soldered or glued with electrically conductive adhesive to respective conductors to make electrical contact thereto. At least two of the conductors, and preferably three as shown at conductors 48, 49, 50, extend along end portion 44 to a first given area 52. In one embodiment, there are two LED's connected in series emitting in the red spectrum, and another LED connected in parallel therewith and emitting in the infrared spectrum, which is currently preferred in pulse oximeters, though other configurations are of course possible. Two of the conductors 46 and 47 extend along end portion 44 to a second given area 54 where light receiving electrical component 30a is mounted.

Areas 52 and 54 are spaced along end portion 44 and have an intermediate section 56 therebetween. The conductors and the electrical components are covered by a thin transparent electrically insulating film 58. Intermediate section 56 flexibly wraps at least partially around finger 26, FIG. 4, and is held thereon by tape, such that finger 26 is between areas 52 and 54 of end portion 44 of the cable and between light emitting electrical components 28a and light receiving electrical component 30a, such that light emitted from light emitting electrical components 28a travels through finger 26 and is received by light receiving electrical component 30a. Conductors 46-50 extend longitudinally along cable 42 and its integral end portion 44, and areas 52 and 54 are longitudinally spaced along end portion 44 such that end portion 44 is wrapped at least partially around finger 26 along a direction parallel to the longitudinal extension of the conductors. Cable end 44 may of course be wrapped around other body parts.

FIG. 5 shows in cross section the preferred construction of the assembly of FIG. 3. The thickness of the assembly in FIGS. 3 and 5 is about five mils. The elevations in FIG. 5 are exaggerated for clarity of illustration. A first layer 61 is provided by a thin elongated flexible sheet-like electrically insulating strip. A second layer 62 is provided on the first layer by a thin elongated flexible sheet-like electrically conductive strip. A third layer 63 is provided on the second layer by a thin elongated flexible sheet-like electrically insulating strip. A fourth layer 64 is provided on the third layer by a plurality of electrical conductors. A fifth layer 65 is provided on the fourth layer by a thin elongated flexible sheet-like electrically insulating strip. A sixth layer 66 is provided on the fifth layer by a thin elongated flexible sheet-like electrically conductive strip. A seventh layer 67 is provided on the sixth layer by a thin elongated flexible sheet-like electrically insulating strip.

In making the structure of FIG. 5, an insulating substrate 61 is provided, followed by formation of conductive layer 62 by vacuum deposition, sputtering, printing, or by etching away metal on a previously metallized insulating substrate 61 to leave the lateral ends 70 and 72 of insulating substrate 61 exposed and the remainder of the substrate covered by metallization 62. Another electrically insulating layer 63 is then provided to cover layer 62, but leaving the lateral ends 74 and 76 of layer 62 exposed. Layer 63 is formed by left and right portions 63a and 63b having a longitudinal central gap 78 therebetween. Conductors 46-50 are then formed by vacuum deposition, sputtering, printing, or by etching away metallization on insulating strips 63a and 63b. Conductors 46-50 provide fourth layer 64. Conductors 46 and 47 are to the left lateral side of gap 78, and conductors 48, 49, 50 are to the right lateral side of gap 78. Insulating layer 65 is then provided to cover conductors 46-50. Layer 65 is formed by left and right portions 65a and 65b having longitudinal central gap 78 therebetween. Layers 65a and 65b extend to the edges of layers 63a and 63b. Conductive layer 66 is then formed over layer 65 and the exposed regions of layer 62 at the central gap 78, and extends to the edges of layer 62. Insulating layer 67 is then formed over layer 66 and extends to the edges of layer 61.

Layers 61 and 67 have lateral widths greater than layers 62 and 66 and extend laterally beyond layers 62 and 66. Layers 61 and 67 engage each other along their laterally outward edges at interfaces 80 and 82 and provide electrical insulation between the patient and the conductive layers 62 and 66. Layers 62 and 66 have lateral widths greater than layers 63 and 65 and extend laterally beyond layers 63 and 65. Layers 62 and 66 engage each other along their laterally outward edges at interfaces 84 and 86 and provide electromagnetic shielding of conductors 46-50. Layers 63 and 65 extend laterally beyond the lateral extent of the conductors and engage each other along their laterally outward edges at interfaces 88 and 90 and also engage each other in central gap 78. Gap 78 in layers 63 and 65 enables shield layers 62 and 66 to engage each other at such gap 78. The shield is thus around all the conductors, and a conductive shield is also provided around those conductors 46 and 47 to the left of gap 78, and a conductive shield is also provided around those conductors 48-50 to the right of gap 78.

The assembly has a longitudinal end 44, FIG. 3, with layers 61, 62, 63, 64 extending longitudinally beyond layers 65, 66, 67. Electrical components 28a and 30a are connected to this longitudinal end, and the components and the conductors are covered by the noted thin transparent electrically insulating film 58. This longitudinal end wraps around the patient's finger or other appendage. The other longitudinal end 92 of the assembly, FIGS. 3 and 6, has layers 61, 62, 63, 64 extending longitudinally beyond layers 65, 66, 67. Gap 78 in layer 63 extends longitudinally along the cable including along longitudinal end 92, but not along longitudinal end 44.

A connection adaptor 94, FIG. 7, is provided for making electrical contact to conductors 46-50 and the conductive shield at longitudinal end 92 of the assembly. In FIG. 7, assembly end 92 is turned upside down from the view in FIG. 6 and makes contact with an elastomeric interconnect structure 96 formed by a plurality of thin electrically conductive sheets 98, FIG. 8, interleaved with a plurality of thin electrically insulating sheets 100. An electrically insulating strip 102 rests on base 104 of the connection adaptor and has a plurality of electrical conductors 106, 107, 108, 109, 110 thereon. Conductor/insulator interleaved interconnect structure 96 is on strip 102. Longitudinal end 92 of assembly 40 is on interconnect structure 96, and a lid or hinged cover 112 is closed to press pad 114 against longitudinal end 92 to clamp conductors 46-50 into electrical contact with interconnect structure 96, and in turn clamp interleaved structure 96 into electrical contact with conductors 106-110, with a clamping force applied perpendicularly to strips 92 and 102.

As shown in FIG. 8, each of sheets 98 and 100 extends generally vertically and longitudinally parallel to the longitudinal extension of the conductors 46-50 and 106-110. The lateral width of each conductor sheet 98 and the lateral width of each insulator sheet 100 is less than the lateral width of each conductor 46-50 and 106-110 and is less than the lateral gap between such conductors. This permits some misalignment between the upper and lower sets of conductors 46-50 and 106-110 and ensures for example that conductor 46 will make contact to conductor 106 through at least one conductor sheet 98, and that at least one insulator sheet 100 will be laterally between conductor 46 and 47 to prevent shorting therebetween, and likewise to prevent shorting between conductors 106 and 107. Conductor 111 on strip 102 makes electrical contact through connector structure 96 to layer 62 at gap 78 to thus provide electrical contact to the shield. As noted above, the elevations and heights shown in the drawings are exaggerated for illustration purposes.

FIG. 9 shows an alternate embodiment with first through seventh layers 121, 122, 123, 124, 125, 126, 127, corresponding respectively to layers 61, 62, 63, 64, 65, 66, 67 of FIG. 5. Fourth layer 124 is provided by conductors 136, 137, 138, 139, 140, corresponding respectively to conductors 66, 67, 68, 69, 70 of FIG. 5. Third layer 123 is laterally continuous along its width, unlike third layer 63 in FIG. 5. A sixth central conductor 141 is formed during the same step when conductors 136-140 are formed. Fifth layer 125 is longitudinally split at gap 142 to form left lateral portion 125a to the left of gap 142, and to form right lateral portion 125b to the right of gap 142. Sixth layer 126 electrically contacts conductor 141 in gap 142. The balance of the structure of FIG. 9 is comparable to that of FIG. 5. Conductor 111 makes electrical contact through interconnect structure 96 to conductor 141 to provide electrical contact to the shield provided by layers 122 and 126.

FIG. 10 shows an alternate embodiment using five layers 153, 154, 155, 156, 157, corresponding respectively to layers 123, 124, 125, 126, 127 of FIG. 9. Layer 154 is provided by conductors 166, 167, 168, 169, 170, 171, corresponding respectively to conductors 136, 137, 138, 139, 140, 141 of FIG. 9. Insulating layer 153 extends laterally continuously across and beneath conductors 166-171, comparably to insulator 123 in FIG. 9. Insulating layer 155 has a central longitudinal gap 172, forming a left lateral portion 155a to the left of gap 172, and a right lateral portion 155b to the right of gap 172, comparably to insulating layer 125 and gap 142 in FIG. 9. Conductor layer 156 covers insulating layer 155 and electrically contacts conductor 171 in gap 172. Insulator layer 157 covers conductor layer 156. Layer 156 provides a ground plane for use in those applications where full shielding is not necessary. Contact to the ground plane is provided through conductor 171, comparably to electrical contact to conductor 141 in FIG. 9.

FIG. 11 shows an alternate embodiment using three layers 183, 184, 185, corresponding respectively to layers 63, 64, 65 of FIG. 5. Layers 183 and 185 are electrically insulating strips. Layer 184 is provided by electrical conductors 186, 187, 188, 189, 190, corresponding respectively to conductors 46, 47, 48, 49, 50 of FIG. 5. The structure of FIG. 11 is used in those applications not requiring a shield or a ground plane.

It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.