US20020072681A1 - Pressure applicator devices particularly useful for non-invasive detection of medical conditions - Google Patents

Abstract

A probe for application to a body part particularly a finger of a patient to detect a change in the physical condition of the patient includes a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the patient's finger and means consituted of a medium wholly self-contained within the probe for applying a static pressure field substantially uniformly around the distal end of the patient's finger, of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow, and retrognade shockwave propagation into the distal end, and to partially unload the wall tension of, but not to occlude, the arteries in the distal end when at heart level or below. A sensor senses changes in the distal end of the patient's finger related to changes in arterial blood volume therein.

Description

FIELD AND BACKGROUND OF THE INVENTION
• The present invention relates to pressure applicator devices for applying a predetermined static pressure to a body part of a patient. The invention is particularly useful as a probe for application to a digit (i.e., a finger or toe) of a patient for the non-invasive detection of certain medical conditions in accordance with the method described in our PCT Application PCT/IL97/00249; and the invention is therefore described below especially with respect to such applications.[0001]
• Our Application PCT/IL97/00249 (WO98/04182, published Feb. 5, 1998) discloses methods and apparatus for the non-invasive detection of a change in a physiological condition of a patient by monitoring changes in the peripheral arterial tone as manifested by changes in the arterial blood volume in a terminal extremity of a body part, preferably a digit (finger or toe) of the patient. The method and apparatus are described in that application particularly for detecting mycardial ischemia and sleep apnea, and also for the continuous monitoring of blood pressure. The described apparatus includes a probe for application to the patient's body part (e.g., finger) which probe includes a housing for receiving the distal end of the patient's body part, and pressurizing means for applying a static pressure field substantially uniformly around the distal end of the patient's body part when received in the compartment, including its terminal-most extremity. The static pressure field is of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow, and retrograde shockwave propagation into the distal end of the body part, and to partially unload the wall tension of, but not to occlude, the arteries in the distal end of the body part when at heart level or below. The probe further includes a sensor within the housing for sensing changes in-the distal end of the patient's body part related to changes in volume therein due to changes in instantaneous blood volume related to arterial tone.[0002]
• That application described a number of probe constructions in which the static pressure field was applied via a remotely located pressure source connected by tubing to a fluid chamber within the probe. However, utilizing such remotely-located pressure sources complicates the construction of the apparatus and also restricts the mobility of the patient.[0003]
OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION
• An object of the present invention is to provide a device particularly useful as a probe in the method and apparatus of the above-cited PCT Application but of a simplified or improved construction as compared to the devices described therein. Another object is to provide a probe which does not restrict the mobility of the patient.[0004]
• According to broad aspect of the present invention, there is provided a device for application to a digit of a patient to detect a change in the physical condition of the patient; the device comprising a probe including: a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the patient's body part; pressurizing means for applying a static pressure field substantially uniformly around the distal end of the patient's body part, when received in the compartment, including the extreme distal tip of the patient's body part, which static pressure field is of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow, and retrograde venous shockwave propagation into the distal end, and to partially unload the wall tension of, but not to occlude, the arteries in the distal end when at heart level or below; and a sensor for sensing changes in the distal end of the patient's body part related to changes in volume thereof due to changes in instantaneous blood volume related to arterial blood volume therein; characterized in that the pressurizing means for applying the static pressure substantially uniformly around the distal end of the patient's body part, including its terminal-most extremity, is constituted of a medium wholly self-contained within the probe.[0005]
• A number of embodiments are described below for purposes of example.[0006]
• According to further features in one class of embodiments described below, the pressurizing means includes an inner resilient membrane within the housing and defining therewith an inner chamber to be filled with a fluid for applying the static pressure via the membrane substantially uniformly around the distal end of the patient's body part, including its terminal-most extremity.[0007]
• According to further features in the latter described embodiments, the pressurizing means further includes an outer resilient membrane attached to the housing externally thereof and defining therewith an outer chamber communicating with the inner chamber via openings in the housing for enlarging the effective volume of the inner chamber such as to cause the inner membrane to apply substantially the same static pressure around the distal end of the patient's body part despite changes in volume therein.[0008]
• A further embodiment is described below for purposes of example, wherein the pressure means includes a body of resilient sponge material formed with a recess defining the compartment for receiving the patient's body part when inserted therein.[0009]
• The sensor within the housing is described below, for purposes of example, as being either an optical sensor for optically detecting, or a Hall Effect sensor for magnetically detecting, volume changes in the subject's finger which attend pulse-related blood volume changes and corresponding finger girth changes.[0010]
• As will be described more particularly below, the present invention enables probes to be constructed with the static pressurizing means wholly self-contained within the probe housing, thereby greatly simplifying the construction of the probe as well as reducing restrictions on the mobility of the patient using such a probe. However, the invention may also be implemented in a two-section probe wherein one section includes a first housing attached to the body part and defining a part of the static pressurizing means, and the second section includes a second housing having another part of the static pressurizing means in fluid connection to the first section, the sensor being located within the second section.[0011]
• While the invention is particularly useful in the methods and apparatus of the above-cited PCT Application, the invention, or various features thereof, can be used in other applications as will also be described below.[0012]
• Further features and advantages of the invention will be apparent from the description below.[0013]
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:[0014]
• FIG. 1 is a longitudinal sectional view, and[0015]
• FIG. 1[0016]ais a corresponding view but rotated 90° with respect to FIG. 1, illustrating one form of finger probe constructed in accordance with the present invention;
• FIG. 2 is a graph of volume versus pressure, and FIG. 3 is a graph of pressure versus time, both helpful in explaining the operation of the finger probe of FIG. 1;[0017]
• FIG. 4 is a view similar to that of FIG. 1, but omitting the sensor and illustrating a modification in the construction of-the finger probe;[0018]
• FIG. 5 is a view similar to that of FIG. 1, but illustrating another finger probe constructed in accordance with the present invention;[0019]
• FIGS. 6[0020]a-6cdiagrammatically illustrate one manner of applying the probe of FIG. 5 to a patient's finger;
• FIGS. 7[0021]a-7cillustrate a modification in the construction of the probe of FIG. 5, and the manner of applying it to the patient's finger;
• FIGS. 8[0022]a-8cdiagrammatically illustrate another probe constructed in accordance with the present invention;
• FIG. 9 is a side elevational view diagrammatically illustrating a probe similar to that of FIGS. 8[0023]a-8cbut including another fastening arrangement for fastening the two half-sections together;
• FIGS. 10[0024]a-10care views corresponding to FIGS. 8a-8cbut illustrating another probe constructed in accordance with the present invention;
• FIGS. 11[0025]a-11cillustrate another probe construction similar to that of FIGS. 10a-10c;
• FIG. 12 illustrates one manner of applying to a patient the probe of FIGS. 11[0026]a-11cand a read-out to an electrical circuit;
• FIGS. 13[0027]a-13cdiagrammatically illustrate another probe construction in accordance with the invention and showing particularly the elements of the sensor and the manner of making electrical connections to them;
• FIG. 14 illustrates a probe similar to that of FIG. 1 or[0028]4 but including a pressure cuff contiguous to the inner (proximal) end of the probe for extending the pressure field with respect to the sensor elements;
• FIG. 15 illustrates another construction of a probe in accordance with another aspect of the invention;[0029]
• FIG. 15[0030]aillustrates an overall apparatus including the probe of FIG. 15;
• FIGS. 16 and 16[0031]adiagrammatically illustrate another probe construction in accordance with the present invention;
• FIG. 17 illustrates an overall apparatus including any of the other described probes;[0032]
• and FIGS. 18[0033]a-18ddiagrammatically illustrate a further probe construction in accordance with the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
• FIGS. 1 and 1[0034]aillustrate one form of probe constructed in accordance with the present invention particularly for use in the method and apparatus of the above-cited PCT Application for monitoring the peripheral arterial tone of a patient's body part (e.g., digit) in order to indicate, in a non-invasive manner, the physiological state or medical condition of the patient. As briefly described above, and as more fully described in the above-cited PCT Application, such a probe includes pressurizing means for applying a static pressure field substantially uniformly around the distal end of the patient's digit, including its terminal-most extremity (extreme distal tip), and a sensor for sensing changes in the distal end of the patient's digit related to changes in volume thereof due to changes in instantaneous blood volume related to arterial blood volume therein. The probe illustrated in FIG. 1, however, is of a simplified construction as compared to the probes illustrated in the above-cited PCT Application, since the static pressure means in the probe of FIG. 1 is constituted of a medium wholly contained within the probe.
• The probe illustrated in FIGS. 1 and 1[0035]aincludes ahousing2 of rigid plastic material, closed at one end, and open at the opposite end, and defining a compartment for receiving the patient'sfinger3. Aninner membrane4 withinhousing2 defines therewith achamber5 for receiving a fluid, such as air, which applies a static pressure field substantially uniformly around the distal end of thefinger3 including its extreme distal tip. The probe illustrated in FIGS. 1 and 1afurther includes a sensor constituted of onepart6aon one side of the finger, and anotherpart6bon the opposite side, for measuring changes in volume of the patient's finger caused by arterial blood flow. The illustrated probe further includes aU-shaped restraining bar7 fixed by anannular ring8 within the housing to cause theinner membrane4 to more firmly grip the patient'sfinger3 when inserted into the probe.
• The above-cited PCT Application is hereby incorporated by reference for further details of the construction of the probe and the manner of its use for monitoring a physiological state or medical condition of the patient.[0036]
• The probe illustrated in FIGS. 1 and 1[0037]a, however, differs from those described in the above-cited PCT Patent Application in the manner of providing the substantially uniform static pressure applied around the digital end of the patient's finger. Whereas in the examples illustrated in the above-cited PCT Application, such a static pressure is provided by a remotely-located pressure source coupled by tubing to the probe, the probe illustrated in FIGS. 1 and 1aincludes a static pressurizing means which is wholly self-contained within the probe housing.
• For this purpose, the probe illustrated in FIGS. 1 and 1[0038]aincludes an outerresilient membrane10 attached to thehousing2 externally thereof and defining with the housing anouter chamber11. Theouter membrane10 is of annular configuration and is applied around an annular portion of the housing spaced from its tip such that theouter chamber11 is of annular configuration. The outerannular chamber11 communicates with theinner chamber5 by means of a plurality ofopenings12 formed throughhousing2.
• The[0039]outer membrane10 enlarges the effective volume of theinner chamber5 such as to cause, according to the Laplace Law, theinner membrane4 to apply substantially the same static pressure around the distal end of the patient'sfinger3 despite changes in volume inchamber5. Thus, the Laplace Law broadly states that the distending pressure (P) within a distensible hollow object is equal at equalibrium to the tension in the wall (T) divided by the two principal radii of curvature of the object (R1, R2); that is P=T (1/R1+1/R2). In a sphere, R1=R2; therefore P=2T/R. When the wall tension and the radius vary in direction proportion to each other (i.e., T/R is constant), as is substantially the case for rubber balloons for most of the range above the minimum distention and below the maximum distention, the balloon distending pressure remains substantially constant irrespective of changes in volume.
• FIG. 2 illustrates the relationship of pressure with respect to volume and particularly shows the relatively large operating zone in which the pressure remains substantially constant with the changes in volume. The actual pressure value is a function of the thickness and mechanical characteristics of the distensible material.[0040]
• The probe illustrated in FIGS. 1 and 1[0041]aeffectively enlarges the volume of theinner chamber5 by the volume of theouter chamber11 communicating with the inner chamber viaopenings12 in thehousing2 such that the static pressure applied by the fluid withinchamber5 remains substantially constant irrespective of changes in volume ofchamber5 caused by arterial blood flow within the patient'sfinger3 received within the probe. If the finger is partially removed from within the probe, the remaining portion will still be subject to the same external pressure because of the Laplace Effect.
• The application of near diastolic counterpressures (40-70 mmHg), over the entire surface of the distal phalanges of the finger, was found not to adversely affect tissue perfusion despite the knowledge that localized pressure applied to tissues can cause collapse of microcirculation. This is due to the fact that while arterial pressure exceeds the counterpressure permitting inflow of arterial blood, for blood to return via the veins venous pressure must overcome the applied external pressure. The induced elevation of venous pressure causes the upstream microcirculation to be pressurized to a pressure level intermediate between the outgoing venous blood and the incoming arterial blood; hence the transmural pressure of the microcirculation within the applied pressure field is greater than zero and collapse of the microcirculation is prevented.[0042]
• The maintenance of fingertip surface temperature within a narrow range around 36° C., and the lack of a tendency for surface temperature to fall after 2 hours of 70 mmHg pressure application, supports the above described model of the preservation of microcirculatory patency and consequently adequate tissue perfusion, as does the fact that overnight application of the pressurized probed on over 120 fingers in 60 subjects was well tolerated with no deleterious effects.[0043]
• In the probe illustrated in FIGS. 1 and 1[0044]a, theinner chamber5 is initially filled with the fluid via aport13 having a one-way valve14 permitting the fluid (e.g., air) to flow into the chamber, but not out of the chamber. FIG. 3 illustrates how the pressure varies with time, and shows that after a fixed quantity of air has been added, the pressure within the device remains relatively constant over a 24-hour period.
• FIG. 4 illustrates a probe of the same construction as described above with respect to FIGS. 1 and 1[0045]a, except that the sensor elements have been omitted for simplification puproses. Also, theport13 and the one-way valve14 have been omitted, and instead a fixed volume of fluid is permanently confined within the space defined by theinternal membrane4 and theexternal membrane10.
• FIG. 5 illustrates a probe of similar construction as FIG. 4, except that the[0046]outer membrane20 is of tubular configuration to define anouter chamber21 with the distal tip ofhousing2. Theouter chamber21 communicates with theinner chamber5 viaopenings22 formed in the housing tip, so as to effectively enlarge the volume of theinner chamber5 to produce the relatively constant static pressure applied to the subject'sfinger3 irrespective of changes in volume, as described above. Although FIG. 5 does not include the refill port or one-way valve, corresponding toelements13 and14 in FIGS. 1 and 1a, these elements could be included in which case they would be provided in the portion ofhousing3 not covered by theouter membrane21.
• FIGS. 6[0047]a-6cillustrate one manner in which the probe constructed as in FIG. 5 may be manipulated to allow the patient'sfinger3 to be inserted into the probe. For this purpose,housing2 of the probe is provided with anannular ring23 on the rigid portion of the housing spaced inwardly (proximally) from theouter membrane20. A syringe including acylinder24 and aplunger25 is used for shifting the fluid from theinner chamber5 to theouter chamber21 in order to permit the patient to insert the finger into the probe. FIG. 6ashows the open end ofcylinder24 applied to ring23; FIG. 6b, shows theplunger25 being retracted within itscylinder24, to thereby draw the fluid within theinner chamber5 into theouter chamber21, permitting the subject to insert the finger into the probe, whereupon theplunger25 may be returned to its normal position within itscylinder24; and FIG. 6cshows the syringe being removed.
• FIGS. 7[0048]a-7cillustrate another manner of manipulating the probe of FIG. 5 to permit insertion of the subject's finger. This is done by providing theouter membrane20 with a finger piece including aknob26 externally of the membrane and fixed to abacking member28 engageing the inner surface of the membrane. Thus,knob26 may be grasped by the user and pulled outwardly (FIG. 7b) to expand theouter chamber21, thereby to draw into it the fluid from the inner chamber and to permit the patient to insert thefinger3 into the probe. After the patient's finger has thus been inserted,knob26 may be released, whereupon the probe will assume the operative position illustrated in FIG. 7c.
• The function of the[0049]outer membrane20 in the construction of FIGS. 7a-7cis to facilitate the Laplace behavior as in the previously described designs.
• FIGS. 8[0050]a-8cdiagrammatically illustrate a probe made of two sections hinged together to enable the probe to be opened (FIG. 8b) and closed around the patient's finger (FIG. 8c). Thus, as shown in FIG. 8a, the housing, generally designated32, is also of tubular configuration closed at one end and open at the opposite end for the insertion of thefinger33. In this case, however,housing32 is split into two half-sections32a,32bjoined together along their length by anintegral hinge32c. Eachhousing section32a,32bincludes aninner membrane strip34a,34bjoined along the sides and end wall of the respective tubular section to define twointernal chambers35a,35b. The probe further includes anouter membrane36a,36bfor eachhousing section32a,32battached to the outer surface of the respective housing section to define the twoouter chambers37a,37bcommunicating with the twoinner chambers35a,35bviaopenings38 in the housing sections. The non-hinged sides of the two housing sections carry “Velcro” (T.M.) loop and hook fastener strips39a,39b, to enable the two sections to be tightly closed around the patient'sfinger33 to apply the desired pressure thereto.
• FIG. 9 illustrates a two-section construction similar to that of FIGS. 8[0051]a-8c, except that, instead of using “Velcro” (T.M.) fastener strips39a,39bto fasten the two sections together, the fastening elements in the construction illustrated in FIG. 9 includetongues40areceived withinslots40bintegrally formed in the contacting edges of the twohousing sections32a,32b.
• FIGS. 10[0052]a-10cillustrate another two-section probe construction, but in this case the two half-sections42a,42bare hinged together at the adjacent edges of the twoend walls43a,43bof each housing section. In addition, instead of using an integral hinge, the hinge is in the form of a flexiblenon-extensible strip44 bonded to the twoend walls43a,43b. The two half sections are secured in their closed conditions by two “Velcro” (T.M.) strips45a,45bfixed to one of thehousing sections42aat the open end of the housing and engageable withstrips46 fixed to theother housing section42b. In all other respects, the construction of the probe illustarted in FIGS. 10a-10cis substantially the same as described above and includes the outer membrane defining the outer chamber communicating with the inner chamber to provide the above-described Laplace behavior.
• FIGS. 11[0053]a-11cand12 illustrate aprobe50 mounted on the finger of a hand51 (FIG. 12).Probe50 is of the two-section construction as in FIGS. 10a-10c, and as more particularly illustrated in FIGS. 11a-11c. The latter figures also illustrate the two-sectioninner membrane53a,53bdefining the two-sectioninner chamber54a,54b, and the two-sectionouter membrane55a,55bdefining the two-sectionouter chamber56a,56bcommunicating with the inner chambers viaopenings57.
• FIG. 11[0054]afurther illustrates the twosensor elements5,8a,58bfixed to the twoinner membranes53a,53b, so as to be located at the opposite sides of the finger when received within the compartment defined by the probe, as shown in FIG. 11b. The twosensor elements58a,58bare connected byelectrical conductors59 to an electrical circuit60 (FIG. 12) fixed to aband61, either directly connected, or-by way of a glove.Electrical circuit60, for example, could include the power supply and other circuitry for driving thesensor elements58a,58b, for receiving the outputs of those elements, and for storing the outputs, e.g., in a storage device, so as to eliminate the need for external electrical connections when the device is being used.
• FIG. 11[0055]afurther illustrates the provision of a pressure-sensitive switch P, or other pressure sensing device such as a strain gage, oninner membrane53b, to ensure that leakage has not occurred, and that the appropriate pressure has been reached, when the probe is applied to the subject's finger. The pressure sensing device could be connected in series with the optical sensor, or in parallel to the control device.
• While many of the drawings, such as FIGS. 4, 7[0056]a-7c,8a-8c,9 and10a-10c, do not include the sensor elements corresponding tosensor elements6a,6bof FIGS. 1 and 1aandsensor elements58a,58bof FIGS. 11a-11c, it will be appreciated that these are omitted merely for purposes of simplifying the illustration and the description of these probes, and that such probes, when used for the particular applications described above, would also include such sensor elements. As indicated earlier, the sensor elements in all the described examples could be optical sensors, e.g., a light source (LED) and a light receiver for optically sensing the changes in the finger received within the probe; magnetic sensors, e.g., a permanent magnet and a magnetic field detector for sensing the changes in the finger girth by the Hall Effect; or other types of sensors, such as described in the above-cited PCT Patent Application.
• FIGS. 13[0057]a-13cillustrate one manner of mounting thesensor elements58a,58bin the finger probe, and making the external electrical connections to the sensor elements. Thus, eachsensor element58a,58bis connected at one end to anelectrical conductor59a,59b, having arubber plug62a,62b, at the opposite end, to provide airtight seals in order to preserve the above described Laplace behavior.Plugs62 a,62bare receivable withinopenings63a,63bin the walls of the twohousing sections52a,52bhinged together by thestrip44 of flexible non-strechable material. The twosensor elements58a,58bare fixed to the twodiaphragms53a,53bwithin the compartment defined by the twohousing sections52a,52b, such that when the sensor elements are assembled, and the two housing sections are in their closed condition as illustrated in FIG. 13c, the two sensor elements engage the opposite sides of the finger received within the housing compartment. The sensor elements output signals, via theelectrical conductors59a,59bwhich pass through the housing wall, to the electrical processing and/or storage system, such as the electrical circuit60 (FIG. 12) on theband61 of the patient.
• One of the plugs, e.g., plug[0058]62a, could be provided with the pressure sensing device P to ensure leakage does not occur, and that the appropriate level of pressure has been reached, when the probe is applied, as described above with respect to FIG. 11a.
• FIG. 14 illustrates a finger probe having a[0059]thimble section72 for receiving the end of the patient'sfinger73 and anannular pressure cuff74 contiguous to the open end of thethimble section72 on the side nearer the heart of the patient when the probe is applied to the patient's finger. Such a pressure cuff extends the static pressure field past thesensor elements58a,58btowards the heart side of the patient as described in the above-cited PCT Application. In this case, aninner diaphragm75 is attached around its periphery to the inner surface of thethimble section72 to define therewith aninner chamber76; and similarly, anotherinner diaphragm77 is attached around its periphery to the inner surface of theannular cuff section74 to define therewith an innerannular chamber78. In addition, anouter diaphragm79 is attached along one side of its periphery to the outer surface of thethimble section72 and along the other side of its periphery to the outer surface of theannular section74, to define with both sections a commonouter chamber80. Theouter chamber80 communicates withinner chamber76 viaopenings81 in thethimble section72, and withinner chamber78 viaopenings82 in theannular cuff section74.
• The[0060]sensor elements58a,58bare located within thethimble section72. This section applies the static pressure field described earlier substantially uniformly around the distal end of the subject'sfinger73. This static pressure field is extended past the sensor elements towards the heart side of the patient by theinner chamber78 defined bymembrane77 of theannular cuff section74 as described in the above-cited PCT Application. In this case, however, the commonouter chamber80 defined by theouter membrane79 maintains substantially the same static pressure field in both thethimble section72 and theannular section74 despite changes in volumes therein, according to the Laplace Law as described above.
• In the above-described probes, the sensor elements (e.g.,[0061]6a,6bin FIGS. 1a,1b) are contained within the finger probe so as to be located on opposite sides of the patient's finger when inserted into the probe. In such arrangements, the sensor elements generate electrical signals which are outputted via electrical conductors to processing and/or storage circuitry, e.g.,electrical conductor59 andstorage circuitry60 in FIG. 12.
• FIGS. 15 and 16 illustrate two arrangements wherein the sensor elements are not located in the housing of the finger probe, but rather in another housing separate from the finger probe and connected thereto by fluid tubes.[0062]
• The probe illustrated in FIG. 15 is of the type illustrated in FIG. 14, including a[0063]thimble section72 and anannular cuff section74. Theinner chamber76 of thethimble section72 is connected by afluid tube90 to achamber92 disposed within a second,rigid housing93, which is preferably mounted close to the finger probe, e.g., on the subjects wrist.Chamber92 is defined by acylinder94 closed at one end by anend wall95, and at the opposite end by amembrane96.
• [0064]Annular chamber78 of thecuff section74 is connected via anothertube97 to anotherchamber98 within thesecond housing93.Chamber98 is defined by acylinder99 closed at oneend100 and at the opposite end by anothermembrane101.
• It will be seen that the two[0065]chambers92 and98 within thesecond housing93 will be subject to the same pressures aschamber76 in theprobe thimble section72 andchamber78 in thecuff section74, respectively. These pressures will be opposed by the pressure within thesecond housing93. The latter pressure may be preset by asyringe102 including acylinder103 coupled to the interior ofhousing93, and aplunger104 which is movable in order to change the volume, and thereby the pressure, withinhousing93.
• [0066]Chamber92, connected viatube90 to thethimble section72 of the probe, includes the sensor for sensing the volume changes withinchamber76 of thethimble section72, and thereby the physical condition of the patient wearing the thimble. Thus, onesensor element105ais fixed tomembrane96 so as to be displaced with that membrane, whereas theother sensor element105bis fixed to thebottom wall95 ofchamber92, such thatsensor element105awill measure the volume changes withinchamber94.
• Although, the FIG. 15 arrangement does not provide the advantage of the previously-described arrangements in having the pressurizing means, for applying the static pressure substantially uniformly around the distal end of the patient's digit, to be constituted of a medium wholly self-contained within the finger probe, it does provide a number of other advantages: Thus, the[0067]thimble section72 of the probe in FIG. 15 does not require an external chamber, as for example described with respect to FIGS. 1 and 1a, sincechamber94 within thesecond housing93, if vented to the atmosphere, would act as the external chamber to provide the probe with the above-described Laplacian P/V characteristics. Also, if the housing is not vented to the atmosphere, this arrangement enables convenient presetting of the pressures in both thethimble section72 of the probe, as well as in theannular cuff section74.
• This arrangement also simplifies the construction of the probe attached to the patient's finger since it locates the sensor elements in the[0068]separate housing93 rather than in the probe itself. Thus, the thimble section of the probe could include two pliable plastic tubular elements each closed at one end and open at the opposite end, and located in the thimble section so as to engage the opposite sides of the patient's finger when inserted therein, such that each such element defines one-half of the pressurizing-chamber. Also, thecuff section74 could be omitted.
• Another possible advantage in the FIG. 15 arrangement is that it tends to avoid local bias towards smaller superficial blood vessels. Also[0069]housing93 containing thesensor elements105a,105b, can be located very close to the finger-applied probe, such as on a wrist band (FIG. 12) to minimize the restrictions in the mobility of the patient and also the length of thefluid tubes90,97.
• FIG. 15[0070]aillustrates a variation in the construction of the apparatus of FIG. 15, in that theseparate housing93 includes apressure sensor105 which senses the pressure within that housing and feeds this information to aCPU106 theCPU106 also receives information from the pressure source107 (e.g., thesyringe102 in FIG. 15) which presets the pressure withinhousing93. The output signals from thesensor elements105a,105bwithinhousing93, are also received byCPU106 after these outputs have been amplified, filtered, and otherwise processed incircuit108. TheCPU106 processes the foregoing inputs, e.g., as described in the above-cited PCT Application, and produces an output which is displayed indisplay109.
• In all other respects, the apparatus illustrated in FIG. 15 is constructed and operates in the same manner as described above with respect to FIG. 15, and therefore includes the same reference numerals identifying the corresponding parts.[0071]
• FIGS. 16 and 16[0072]aillustrate a finger probe of the same construction as described above, particularly as illustrated in FIGS. 15 and 15a, but including an adhesive layer to be contacted by the patient's finger received within the finger probe. The adhesive layer is provided by a double-sidedadhesive strip107, including an inneradhesive layer107aand an outeradhesive layer107b. The inneradhesive layer107ais covered by aprotective layer108 which is stripped away, after the finger has been inserted within the probe, to enable the inneradhesive layer107ato contact and firmly adhere to the subject's finger when received within the probe.
• In all other respects, the probe illustrated in FIGS. 16 and 16[0073]amay be of the same construction as described above, particularly with respect to FIGS. 15 and 15a.
• FIG. 17 illustrates apparatus including the novel finger probe used in apparatus, similar to that described in FIG. 23 of the above-cited PCT Application, for effecting continuous non-invasive blood pressure measurements. For purposes of example, the finger probe illustrated in FIG. 17 is shown as being of the construction described above with respect to FIGS. 11[0074]a-11c, although it will be appreciated that it could be of any of the other described constructions.
• Thus, the finger probe illustrated in FIG. 17 includes an electrical heater winding[0075]110 applied around the outer surface of theprobe housing52a,52bfor heating the patient's finger within theinternal chamber54a,54bof the probe to any predetermined temperature, preferably 35-40°C. A thermister111 or the like controls the electrical heater in order to maintain that temperature so as to dilate the blood vessels in the finger.
• The probe illustrated in FIG. 17 further includes a[0076]vertical position sensor112 for sensing the vertical position of the finger probe with respect to a reference point.Sensor112 may be of the same construction as described in the above-cited PCT Application, including a housing filled with a liquid (preferably water) closed at one end by aflexible membrane112aand connected at its opposite end via a water filledtube113 to apressure transducer114.Transducer114 produces an electrical output corresponding to the vertical position ofsensor112, and thereby of the finger probe, with respect to the subject's heart level.
• The previously-described[0077]sensor elements58a,58bof the finger probe are connected viaelectrical conductors115 to acircuit115afor amplifying and processing the output signals, and via an A/D converter116, to theCPU117. The electrical heater winding110 is supplied with power viaconductors118 connected to anelectrical power supply119, also supplying power to theCPU117.Thermister111 is connected viaconductors120 to acontrol circuit121, which also produces an output to theCPU117 via the A/D converter116.CPU117 produces an output to display122.
• The manner in which the apparatus illustrated in FIG. 17 is calibrated, and then used, for the continuous non-invasive blood pressure measurements is described in the above-cited PCT Application.[0078]
• FIGS. 18[0079]a-18dillustrate a further finger probe device including a self-contained pressurizing source eliminating the need for fluid connections from the probe to an external source of pressurized fluid. In the probe illustrated in FIGS. 18a-18d, however, the pressurizing source for applying the static pressure to the patient's finger is not provided by a fluid chamber within the finger probe as in the previously-described embodiments, but rather is provided by a body of resilient sponge material within the finger probe.
• Thus, the finger probe illustrated in FIGS. 18[0080]a-18dincludes ahousing202 split into two half-sections202a,202b, hinged together along one side by a flexible,non-extensible strip203 and containing “Veldro” (T.M.) strips204 at the opposite side for tightly clamping the probe to the patient'sfinger205 according to the static pressure to be applied. In this case, however, the means for applying the static pressure around the patient's finger is in the form of a body ofresilient sponge material206a,206b, carried by each half-section of the probe. A layer of agel material207a,207b, covers the inner surface of each of thesponge bodies206a,206bso as to be exposed for direct contact with the patient's finger when inserted into the housing and the housing sections are in their closed condition as illustrated in FIGS. 18cand18d. Thesensor elements208a,208b, which may be any of the devices described above, are carried on the inner surfaces of each of thesponge bodies206a,206b, or theirrespective gel layers207a,207b.
• It will be seen that any desired fixed pressure may be applied to the patient's finger within the probe by applying the Velcro strips with the appropriate tightness to the two housing sections around the patient's finger. The gel layers[0081]207a,207bmore securely fix the sponge bodies and their sensor elements to the finger end, and more evenly dissipate the applied force.
• While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations may be made. For example, other sensors could be used than the optical and Hall-Effect sensors referred to above, e.g., as described in the above-cited PCT Application. Other fasteners than the “Velcro” or other types described above could be used. Also, the probe may be incorporated in a glove to be worn by the subject as also described in the PCT Application.[0082]
• Further, the finger probe could be used to house a pulse oximeter for measuring the oxygen saturation of blood. In such an application, conventional pulse-oximeter sensors could be included in the probe housing and would produce a better measurement of the oxygen saturation of the blood (SaO[0083]₂) because of the stable environment provided by the static pressure field.
• It will be appreciated that all the embodiments described with respect to FIGS.[0084]1-17 could be designed to provide the above-described Laplace operation, wherein the distending pressure remains substantially constant irrespective of changes in volume. While the probe construction of FIGS. 18a-18d, including the sponge cushion material, would not operate according to the Laplace law., it will be appreciated that a hybrid construction could be provided, wherein the sponge cushion is included to occupy only a part of the chamber containing the sensors and thereby to provide substantially the Laplace operation.
• In addition, the invention could be used in applications other than finger probes, e.g., as a supplement to a wound dressing for a body part, as a means for producing venous distention in a body part in prepartion for venapuncture, as a means for supporting, decompressing and/or immobilizing soft tissue injuries like sprains in a wrist or ankle, as a pressure applicatior for edematous regions in a body part, and the like.[0085]
• Another possible application of the invention is as a disposable sensor, based on a preinflated surface mounted membrane or membranes, capable of being applied to a finger by being wrapped around the finger and having a free end adhesively closed to impart uniform pressure to the enclosed mass of the finger. The membrane(s) may be mounted on an airtight bendable, but nonstrechable, material such as plastic sheeting, rubberized cloth, or the like. A tube or tubes would communicate between the finger probe and a sensing consol which may be located at the wrist, for example. A unidirectional pressure release valve located at the remote site would ensure that excess pressure is vented from the finger probe upon its initial application.[0086]
• A further possible application of the invention is in a vertical displacement sensor consisting of a single fluid filled tube connected to an atmospheric pressure referenced pressure transducer at one end, and a compliant tip at the opposite end. The pressure transducer and the compliant tip would be respectively situated at heart level and the measurement site, or vice-versa.[0087]
• A still further variation would be to provide the probe with the combination of an optical sensor and a volumetric sensor within the same probe. The optical sensing elements need not be located on opposite sides of the finger as described, but could be at other locations. One particularly useful arrangement is that in which optical sensor ancL light source are respectively placed over the digital arteries, thus being oriented at about 140 degrees with respect to each other.[0088]
• Many other variations, modifications and applications of the invention will be apparent.[0089]

Claims (47)

What is claimed is:

1. A device for application to a body part of a patient to detect a change in the physical condition of the patient; said device comprising a probe including:

a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the patient's body part including its terminal-most extremity;

pressurizing means for applying a static pressure field substantially uniformly around the distal end of the patient's body part, when received in said compartment, including its terminal-most extremity, which static pressure field is of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow, and retrognade shockwave propogation into said distal end, and to partially unload the wall tension of, but not to occlude, the arteries in said distal end when at heart level or below;

and a sensor for sensing changes in said distal end of the patient's body part related to changes in volume thereof due to changes in instantaneous blood volume related to arterial blood volume therein;

characterized in that said pressurizing means for applying said static pressure substantially uniformly around the distal end of the patient's body part, including its terminal-most extremity, is constituted of a medium wholly self-contained within said probe.

2. The device according toclaim 1, wherein said pressurizing means includes an inner resilient membrane within said housing and defining therewith an inner chamber to be filled with a fluid for applying said static pressure via said membrane substantially uniformly around the distal end of the patient's body part including its terminal-most extremity.

3. The device according toclaim 2, wherein said pressurizing means further includes an outer resilient membrane attached to said housing externally thereof and defining therewith an outer chamber communicating with said inner chamber via openings in said housing for enlarging the effective volume of said inner chamber such as to cause said inner membrane to apply substantially the same static pressure around the distal end of the patient's body part despite changes in volume thereof.

4. A device to be applied around a body part of a patient, comprising a probe including:

a housing for application to the body part; and

pressurizing means for applying a static pressure field substantially uniformly around the body part; said pressurizing means including:

an inner resilient membrane within said housing and defining therewith an inner chamber to be filled with a fluid for applying said static pressure via said membrane substantially uniformly around the distal end of the patient's digit including its distal tip;

and an outer resilient membrane attached to said housing externally thereof and defining therewith an outer chamber communicating with said inner chamber via openings in said housing for enlarging the effective volume of said inner chamber such as to cause said inner membrane to apply substantially the same static pressure around the body part despite changes in volume thereof.

5. The device according toclaim 3, wherein said housing includes a port having a one-way valve for filling said inner chamber to the desired predetermined pressure.

6. The device according toclaim 3, wherein said outer resilient membrane is of annular configuration and is applied around an annular portion of the housing formed with said openings providing communication between said inner and outer chambers.

7. The device according toclaim 3, wherein said outer resilient membrane is of tubular configuration and is attached around the outer tip of the housing, which tip is formed with said openings providing communication between said inner and outer chambers.

8. The device according toclaim 7, wherein said housing includes an annular ring spaced from the outer resilient membrane attached to the housing for receiving the open end of a syringe to be used for enlarging said outer chamber by shifting the fluid from said inner chamber to said outer chamber to facilitate insertion of the patient's body part into said compartment.

9. The device according toclaim 7, wherein said outer resilient membrane includes a finger piece graspable by a user for enlarging said outer chamber by shifting the fluid from said inner chamber to said outer chamber to facilitate insertion of the patient's body part into said compartment.

10. The device according toclaim 9, wherein said finger piece includes a knob extending externally of the outer membrane for grasping by the user and fixed to a backing member engageable with the inner surface of the outer membrane.

11. The device according toclaim 3, wherein said housing is made of two sections hinged together to assume open and closed conditions, and including fastening elements for fastening the two sections in their closed condition.

12. The device according toclaim 11, wherein said fastening elements are “Velcro” (T.M.) hook and loop fastener strips carried by the two housing sections.

13. The device according toclaim 11, wherein said fastening elements are tongue and recess formations integrally formed in the two housing sections.

14. The device according toclaim 11, wherein said housing includes a tubular side wall closed at one end by an end wall and open at the opposite end, said tubular housing being split into two half-sections and hinged together at said end wall.

15. The device according toclaim 11, wherein said housing includes a tubular side wall closed at one end by an end wall and open at the opposite end, said housing being split into two half sections and hinged together along said tubular side wall.

16. The device according toclaim 14, wherein said hinge is an integral hinge integrally formed with said two half sections of the housing.

17. The device according toclaim 14, wherein said hinge is a strip of flexible strechable material attached to the two housing half-sections.

18. The device according toclaim 14, wherein:

said inner membrane includes a membrane strip joined to the side wall and end wall of each housing section;

and said outer membrane includes another membrane strip attached to the outer surface of each housing section.

19. The device according toclaim 1, wherein said pressurizing means includes an adhesive layer within said compartment to be contacted by the patient's body part received within the device.

20. The device according toclaim 19, wherein said adhesive layer is on an inner surface of a plastic strip having an other adhesive layer on its outer surface, said plastic strip further including a protective layer covering said adhesive layer on its inner surface and strippable therefrom to enable said inner surface to contact and firmly adhere to the patient's body part when received within the device.

21. The device according toclaim 1, further including an annular pressure cuff applied around the patient's body part contiguous to said housing on the heart side of the patient to extend the static pressure field past the sensor on the heart side of the patient.

22. A device for application to a body part of a patient to detect a change in the physical condition of the patient; said device comprising:

a first housing defining a first compartment closed at one end and open at the opposite end for receiving the distal end of the patient's body part including its terminal-most extremity;

pressurizing means for applying a static pressure field substantially uniformly around the distal end of the patient's body part, when received in said compartment, including its terminal-most extremity, which static pressure field is of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow, and retrognade shockwave propogation into said distal end, and to partially unload the wall tension of, but not to occlude, the arteries in said distal end when at heart level or below;

a sensor for sensing changes in said distal end of the patient's body part related to changes in volume thereof due to changes in instantaneous blood volume related to arterial blood volume therein;

and a second housing separate and apart from said first housing and defining a second compartment having a fluid connection to said first compartment; said sensor being located within said second housing in operative position with respect to said second compartment.

23. The device according toclaim 22, wherein said second housing includes a presettable pressure source for presetting a predetermined pressure in the interior of said second housing.

24. The device according toclaim 22, wherein said second housing is vented to the atmosphere.

25. The device according toclaim 1, wherein said pressurizing means includes a body of resilient sponge material formed with a recess defining said compartment for receiving the patient's digit when inserted therein.

26. The device according toclaim 25, wherein:

said housing is made of two sections hinged together to assume open and closed conditions;

said body of resilient sponge material is also made of two sections, one carried on each section of the housing;

and said housing sections further include fastening elements for fastening the two housing sections in their closed condition.

27. The device according toclaim 26, wherein each of said sections of the body of resilient sponge material includes a layer of a gel material exposed for contact with the patient's body part when inserted into the housing and the housing sections are in their closed condition.

28. The device according toclaim 1, wherein a pressure sensing device is located within said housing to sense the pressure applied to the patient's body part by said pressurizing means.

29. The device according toclaim 1, wherein said sensor is an optical sensor and includes a light source carried within said housing on one side of the patient's body part when inserted therein, and a light detector carried within said housing on the opposite side of the patient's body part.

30. The device according toclaim 1, wherein said sensor is a Hall effect sensor and includes a permanent magnet carried within said housing on one side of the patient's body part when inserted therein, and a magnetic field detector carried within said housing on the opposite side of the patient's body part.

31. The device according toclaim 1, wherein said sensor includes the combination of an optical sensor device and a volumetric sensing device.

32. The device according toclaim 1, wherein said sensor is a pulse oximeter sensor for sensing the oxygen saturation of blood.

33. The device according toclaim 1, further including electrical conductors leading from said sensor to an electrical circuit carried by a band applied to another body part of the patient.

34. The device according toclaim 33, wherein said electrical circuit includes a storage device for storing the output of said sensor.

35. A device to be applied to a body part of a patient, comprising:

a housing made of two sections hinged together to assume open and closed conditions;

a body of a resilient sponge material divided into two sections, each carried by one of said housing sections, and defining, in the closed condition of the two housing sections, a compartment for receiving the patient's body part;

and fastening elements for fastening the two housing sections in their closed condition.

36. The device according toclaim 35, wherein each of said sections of the body of resilient sponge material includes a layer of a gel material exposed for contact with the patient's body part when inserted into the housing and the housing sections are in their closed condition.

37. The device according toclaim 35, wherein said fastening elements are “Velcro” (T.M.) hook and loop fastener strips carried by the two housing sections.

38. A device for application to a body part of a patient to detect a change in the physical condition of the patient, said device comprising:

a housing defining a compartment closed at one end and opend at the opposite end for receiving the distal end of the patient's body part;

a first membrane defining a first chamber containing a pressurized fluid to apply a static pressure field to the patient's body part when received within the housing;

a second membrane defining a second chamber communicating with said first chamber and of a volume such that the combined volumes of the two chambers maintain a relatively constant pressure despite changes in volume according to the Laplace Law;

and sensor elements in at least one of said chambers for sensing changes in said distal end of the patient's body part related to changes in volume therein.

39. The device according toclaim 38, wherein said second membrane encloses at least a portion of said housing to define said second chamber with the outer surface of the enclosed portion of the housing, said second chamber communicating with said first chamber via openings through said housing.

40. The device according toclaim 39, wherein said sensor elements are carried by said first membrane in said first chamber.

41. The device according toclaim 39, wherein said second membrane is of annular configuration and is applied around an annular portion of the housing formed with said openings providing communication between said inner and outer chambers.

42. The device according to claim391 wherein said second membrane is of tubular ocnfiguration and is attached around the outer tip of the housing, which tip is formed with said openings providing communication between said first and second chambers.

43. The device according toclaim 38, wherein said second chamber defined by said second membrane is located in a second housing and is connected to said first chamber by a fluid tube.

44. The device according toclaim 43, wherein said sensor is Located in said remote housing in operative position with respect to said second chamber.

45. The device according toclaim 44, wherein said second membrane is subject to the differential pressure with respect to the pressure in said second chamber and the ambient pressure in said second housing.

46. The device according toclaim 45, wherein said second housing includes a pressure presetting device for presetting the pressure within said second housing acting on said second membrane.

47. The device according toclaim 46, wherein said remote housing includes a pressure sensor for sensing the ambient pressure within said second housing.

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