CA2074826A1 - Intravascular pressure posture detector - Google Patents
Intravascular pressure posture detectorInfo
- Publication number
- CA2074826A1 CA2074826A1 CA002074826A CA2074826A CA2074826A1 CA 2074826 A1 CA2074826 A1 CA 2074826A1 CA 002074826 A CA002074826 A CA 002074826A CA 2074826 A CA2074826 A CA 2074826A CA 2074826 A1 CA2074826 A1 CA 2074826A1
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- patient
- pressure sensors
- posture
- changes
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000000747 cardiac effect Effects 0.000 claims abstract description 14
- 210000000748 cardiovascular system Anatomy 0.000 claims abstract description 9
- 210000001631 vena cava inferior Anatomy 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims abstract description 6
- 230000003247 decreasing effect Effects 0.000 claims abstract description 5
- 102100026827 Protein associated with UVRAG as autophagy enhancer Human genes 0.000 claims description 8
- 101710102978 Protein associated with UVRAG as autophagy enhancer Proteins 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 5
- 230000001225 therapeutic effect Effects 0.000 claims description 3
- 239000003814 drug Substances 0.000 abstract description 2
- 229940079593 drug Drugs 0.000 abstract description 2
- 238000012377 drug delivery Methods 0.000 abstract description 2
- 230000003284 homeostatic effect Effects 0.000 abstract 2
- 230000001684 chronic effect Effects 0.000 abstract 1
- 230000002526 effect on cardiovascular system Effects 0.000 abstract 1
- 238000002513 implantation Methods 0.000 abstract 1
- 230000008859 change Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- 238000009530 blood pressure measurement Methods 0.000 description 5
- 230000001052 transient effect Effects 0.000 description 4
- 230000002792 vascular Effects 0.000 description 3
- 206010011224 Cough Diseases 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 239000007943 implant Substances 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 210000005245 right atrium Anatomy 0.000 description 2
- 230000000638 stimulation Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 230000036772 blood pressure Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000001144 postural effect Effects 0.000 description 1
- 206010041232 sneezing Diseases 0.000 description 1
- 210000001321 subclavian vein Anatomy 0.000 description 1
- 210000002620 vena cava superior Anatomy 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/021—Measuring pressure in heart or blood vessels
- A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
- A61N1/365—Heart stimulators controlled by a physiological parameter, e.g. heart potential
- A61N1/36514—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure
- A61N1/36542—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by body motion, e.g. acceleration
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
- A61N1/365—Heart stimulators controlled by a physiological parameter, e.g. heart potential
- A61N1/36514—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure
- A61N1/36564—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by blood pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
- A61B2560/02—Operational features
- A61B2560/0242—Operational features adapted to measure environmental factors, e.g. temperature, pollution
- A61B2560/0247—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value
- A61B2560/0261—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value using hydrostatic pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
- A61B5/6867—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive specially adapted to be attached or implanted in a specific body part
- A61B5/6869—Heart
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
- A61B5/6867—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive specially adapted to be attached or implanted in a specific body part
- A61B5/6876—Blood vessel
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
- A61N1/365—Heart stimulators controlled by a physiological parameter, e.g. heart potential
- A61N1/36514—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure
- A61N1/36535—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by body position or posture
Abstract
Apparatus and method for detecting changes in the posture of a patient. Two pressure sensors (32, 36) are chronically implanted at different places (12, 14) in the cardiovascular system. One may be positioned in the right heart (12), for example, and the other placed in the inferior vena cava (14). The positioning is selected for ease of chronic implantation. However, the positions chosen must be such that the differences in pressure with changes in posture are differentially measurable. The differences in pressure changes (90, 92, 94) sensed at the two positions enable electronic circuitry (106) to determine changes in posture of the patient. These changes in posture may be used to indicate associated physiological changes such as increased or decreased demand on the cardiovascular system or changes in other homeostatic functions.
Compensation for this changing cardiovascular or other homeostatic functions may be partially met through increasing or decreasing the escape interval (108) of a demand cardiac pacemaker (22) or by altering the drug delivery regimen of an implantable drug dispenser.
Compensation for this changing cardiovascular or other homeostatic functions may be partially met through increasing or decreasing the escape interval (108) of a demand cardiac pacemaker (22) or by altering the drug delivery regimen of an implantable drug dispenser.
Description
WO 91/11138 PCI'/US91/00416 f ~``
.. .. .
.. .. .
2~74826 INTR~V~SCUI.P.R PRES8URE POSTURE: DETECTOR
CROSS REFERENCE TO CO-PE~NDING APPLICATIONS
None Bl~CRGE~OUND OF $~IE INVENTION
1. ~ield of the Invention - The present invention generally relates to implantable medical devices, and more specifically, relates to chronically implantable devices for determination of the posture of a patient.
2. Des~riPtion of the Prior Art - Posture detection devices have been known in the art for some time. Often these are implanted and used for control of the pacing rate of an artificial cardiac pacer. The typical method is through the use of gravity using a mercury---switch, for- example. The gravity switch method, of course, provides only a binary or two state output. Either the switch is open or it is closed.
Intravascular pressure sensors are also known in the art.
U.S. Patent No. 4,407,296 issued to Anderson teaches a chronically implantable pressure transducer suitable for use in the cardiovascular system. A pressure transducer with an improved electronic circuit is taught in U.S. Patent No.
4,432,372, issued to Monroe. A further improved pressure transducer is taught in U.S. Patent No. 4,485,813, issued to Anderson, et al. These pressure sensors have been directed to the control of artificial cardiac pacers using algorithms which convert measurements of pressure or change of pressure into pacing rate.
U.S. Reissue Patent No. 30,372, issued to Mirowski, et aI. teaches control of an implantable defibrillator using an intravascular pressure sensor. None of these references teaches the use of differential pressure measurement to determine,the posture of the patient.
SUl~M~RY' OF T~IE I~VENTION
The present invention uses at least two pressure sensors which are chronically implanted in the vascular system. These sensors are positioned such that changes in pressure are ~
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, . .
. i. . .
,',, ~' ' ' ' ' , ~, , , WOgl/11138 PCT/US91/00416 ~.
207~82~
sensed in response to changes in posture of the patient. To determir.e the posture of the patient, the sensors are placed to sense differential changes in pressure with changes in posture.
This differential pressure change results from gravitational effects upon different points within the vascular system. For example, with pressure sensors in the ri~ht heart and the inferior vena cava of a supine patient, the pressure measurements are approximately the same.
However, when the patient is erect, the sensor in the inferior vena cava will measure a greater pressure than the sensor in the right heart. ~t is this pressure differential which -identifies the patient~as-erect.~
Because the sensors measure the actual pressure, the differential pressure changes continuously from completely supine to completely erect. Therefore, a patient's differential pressure measurement when sitting up can be distinguished from measurements taken when either supine or erect. Other posture variations can be detected as well.
A further advantage of determining posture with differential pressure is that factors which result in equal pressure changes to all of the sensors are cancelled out and thereby eliminated. Typical of these factors are differences in altitude and atmospheric pressure. Also eliminated in this way are transients such as e~perienced in coughing or sneezing.
The posture measurement may be used in a number of ways.
A typical application is in cardiac pacing. By assuming that an upright patient has a higher cardiac demand than a supine patient, the posture determination is readily used to increase pacing rate for patients in the upright posture.
Alternatively, the posture determination may be used to vary the drug delivery regimen of an implanted drug dispenser, for example, by increasing or initiating the dispensing of a cardiac or other druy. Generally, the invention may be useful ;: '~ ~: ' ' ' : ~
:.... . . . .
.:: , , :
,j. . .
, :,' ' ' ` ' ,~. ,, ~ `207~826 in conjunction with any implantable device which provides a therapeutic treatment to the body, for varying the treatment in response to postural changes.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects and features of the present invention will be more apparent as the same becomes further understood from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings and in which like reference numerals refer to like parts and wherein:
FIG. l is a schematic diagram showing placement of two pressure sensors in a patient in a supine position;
FIG. 2 is a schematic diagram showing placement of two .
pressure sensors in a patient in a partially seated position;
FIG. 3 is a schematic diagram showing preferred placement of two pressure sensors in the vascular system of a patient;
FIG. 4 is a block diagram of an implantable pulse generator incorporating circuitry to vary artificial pacing rate with posture changes determined by differential pressure measurement;
FIG. 5 is a graphic representation of the pressure measured by a single sensor in a patient changing posture;
and, FIG. 6 is a graphical representation of the pressure measurements taken from two sensors and the resulting differential.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention utilizes at least two chronically implantable pressure sensors positioned within the cardiovascular system. In the preferred mode, two pressure sensors are used, however, additional sensors may be employed in accordance with the teaching of the present invention. The pressure sensor taught in U.S. Patent No. 4,485,813 issued to Anderson, et al. and incorporated herein by reference is the sensor preferred for this application. Other suitable sensors .
, . . ':
:' . ' : , ' ':
.
WO91/lll3X Pcr/uss1/oo4l6 207~82~ ~' ~`
are taught in U.S. Patent No. 4,432,372 issued to Monroe and U.S. Patent No. 4,407,296 issued to Anderson, both of which are herein incorporated by reference.
FIG. 1 is a schematic view of a patient lo in a supine position. The patient 10 has two pressure sensors such as discussed above chronically implanted in the cardiovascular system. The first of these sensors is implanted in the right side of heart 12 using normal implant techniques. The second pressure sensor is implanted in the inferior vena cava at position 14. A linear distance 16 of L units separates the two pressure sensors. If the patient 10 is lying horizontally, the pressure sensed within heart 12 and in the ; inferior vena cava by the pressure sensor at position 14 will ` be approximately the same.
~ IG. 2 is a schematic view of patient 10 having the same chronically implanted pressure sensors. In this view, however, patient 10 is in a partially seated position. As can be seen in the drawing, the torso of patient 10 is inclined at an angle 18 from the horizontal. This causes the pressure sensor in heart 12 to be higher than the pressure sensor at ~ position 14. The distance in elevation may be computed from il the distance L between the sensor (see also Fig. 1) and the angle 1 of inclination of the torso. The difference in elevation 20 is L times the sine of angle 18.
i Using standard hydraulic principles, one can readily see that the pressure sensed within heart 12 will be less than that measured by the pressure sensor at position 14 by an amount proportional to elevation ~0. By measuring this pressure differential, the angle 18 can thus be estimated. In this way the degree to which the torso of patient 10 is erect can be estimated.
Notice that in this embodiment the pressure di~ferential of a fully seated patient 10 and a standing patient 10 cannot be distinguished. If it were necessary to make such a determination, the pressure sensor at position 14 must be ,, :
) i,:.:, ; . :. .
:"'. ' ' ' ' ' ' ' .
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WO91/1l~3X PCT/US91/00416 ..
207~826 moved below the torso into one of the legs. To do so, however, complicates the implant procedure, and so should be done only if that degree of precision is required for the application.
FIG. 3 is a schematic diagram of the two pressure sensors as implanted in the cardiovascular system. Heart 12 has pressure sensor 36 implanted within the right atrium as shown.
It is coupled via electrical lead 24 through the venous system to implantable pulse generator 22 in the same fashion as with transvenous cardiac pacing applications.
Similarly pressure sensor 32 is positioned in the inferior vena cava (see also Figs. 1 and 2). Pressure sensor - ~- 32 is electrically coupled to implantable pulse generator 22 via transvenous lead 30. Both leads 24 and 30 proceed through the subclavian vein 26 from implantable pulse generator 22 after entry at point 34. Entry to the right atrium of heart 12 is via superior vena cava 28.
In the preferred embodiment, implantable pulse generator 1 22 functions as an artificial cardiac pacer. The necessary i pacing lead is not shown for clarity. However, this application is to be understood as typical and not limiting of the scope of the present invention.
In the illustrated embodiment, the pressure sensors are located on two separate leads. However, in some cases, it may be desirable to locate both pressure sensors on the same lead.
Differential pressure sensing using a single pressure transd~icer as illustrated in the above cited U.S. Patent No.
4,407,296 rather than two separate pressure sensors may also be desirable in some circumstances.
¦ FIG. 4 is a block diagram of implantable pulse generator 22. Leads 24 and 30 are shown as transferring the signals from pressure sensors 36 and 32, respectively. Signal processors 102 and 104 amplify and integrate these signalsO
`~ The difference i pressure experienced by the two pressure sensors is determined by computed pressure differential .
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W09l/lll38 PCT/US91tO0416 207~826 circuitry 106. This circuitry controls the escape interval timer 108 using standard voltage control oscillator circuitry.
The greater the pressure differential, the shorter the ~ -interval produced by escape interval tim~r 108.
Fig. 4 is intended to be exemplary of the general type of circuitry to be employed in the present invention. However, alternate circuitry may also be employed. For example, signal processors 102, 104 may function as low pass filters, or integration/filtering may be performed after computation of the pressure differential, as in an embodiment employing a ~
single, differential pressure transducer. ~-Sense a~plifier 110, inhibit logic 112, and stimulation pulse amplifier--114 operate as in a normal demand pacemakerO
Sensing and stimulation is provided using a standard transvenous pacing lead 100. The pacing output of implantable pulse generator 22 differs from the normal demand pacer only that the underlying artificial pacing rate is decreased as the pressures sensed by the two pressure senso~s (i.e. pressure sensors 32 and 36) are more nearly the same and increased as ~
the pressure differential is increased. ~`
FI~. 5 is a graphisal representation 40 of the idealized output of pressure sensor 32 with changes in patient posture.
~he projection along axis 4~ is the pressure sensed (and hence voltage output of the pressure sensor). The projection along axis 44 is the time over which a number of posture changes take place. The level at 52 shows the measurement when the patient is supine. The patient sits up at 46 resulting in level 48. The patient lies down again at 50 resulting in supine level 52. Notice with this idealized data that posture chan~es could be monitored with a single pressure sensor.
FIG. 6 is a graphical representation of the outputs of both pressure sensors and the computed pressure differential along the same time axis showing some typical transient conditions.
The upper chart shows the pressure level 60 measured by .~ , .. .
.
.. . , . :
W~91t11138 PCT/~S91/0~16 ~,~3 2074~26 pressure sensor 36 while patient l0 is supine. As the patient rises, the pressure measured by pressure sensor 36 actually decreases to level 62. The pressure increases at 64 and 66 are not related to posture changes. The increase at 64 is a short term transient such as a sneeze or cough. The change beginning at 66 and resulting in level 68 is of longer duration. It may be of physiological causes such as elevated central venous blood pressure or external causes such as a change in altitude (e.g. as in an airplane or elevator). In either situation, the non-posture change is detected as a pressure change by pressure sensor 36.
The middle graph shows the output of pressure sensor 32 over the same-time--period. Notice that the supine level is 70. As the patient l0 rises, it is detected as pressure increase 74 resulting in level 76. Transient pressure rise 78 and non-posture change pressure rise 80 resulting in new pressure level B2 are detected as with pressure sensor 36.
The bottom graph shows the pressure differential of the two pressure sensors. It corresponds to the output of computed pressure differential 106 (see also Fig. 4). Level 90 shows essentially no pressure differential. It corresponds to the time when patient l0 is in the supine position. In the preferred em~odiment this results in the longest escape interval (or the lowest underlying pacing rate). As the patient rises, the pressure differential is increased at 92 resulting in new level 94. This corresponds to a shorter escape interval.
Notice that the pressure differential curve does not contain transient 64/78 nor non-posture pressure change 66/80.
j This is because the different:ial remains the same when both sensors are subjected to the same non-posture pressure changes.
Other applications of the present invention are readily apparent to thos~ in the art without deviation from the scope of the claims hereto attached.
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CROSS REFERENCE TO CO-PE~NDING APPLICATIONS
None Bl~CRGE~OUND OF $~IE INVENTION
1. ~ield of the Invention - The present invention generally relates to implantable medical devices, and more specifically, relates to chronically implantable devices for determination of the posture of a patient.
2. Des~riPtion of the Prior Art - Posture detection devices have been known in the art for some time. Often these are implanted and used for control of the pacing rate of an artificial cardiac pacer. The typical method is through the use of gravity using a mercury---switch, for- example. The gravity switch method, of course, provides only a binary or two state output. Either the switch is open or it is closed.
Intravascular pressure sensors are also known in the art.
U.S. Patent No. 4,407,296 issued to Anderson teaches a chronically implantable pressure transducer suitable for use in the cardiovascular system. A pressure transducer with an improved electronic circuit is taught in U.S. Patent No.
4,432,372, issued to Monroe. A further improved pressure transducer is taught in U.S. Patent No. 4,485,813, issued to Anderson, et al. These pressure sensors have been directed to the control of artificial cardiac pacers using algorithms which convert measurements of pressure or change of pressure into pacing rate.
U.S. Reissue Patent No. 30,372, issued to Mirowski, et aI. teaches control of an implantable defibrillator using an intravascular pressure sensor. None of these references teaches the use of differential pressure measurement to determine,the posture of the patient.
SUl~M~RY' OF T~IE I~VENTION
The present invention uses at least two pressure sensors which are chronically implanted in the vascular system. These sensors are positioned such that changes in pressure are ~
" . :
" , . ., ' .
, . .
. i. . .
,',, ~' ' ' ' ' , ~, , , WOgl/11138 PCT/US91/00416 ~.
207~82~
sensed in response to changes in posture of the patient. To determir.e the posture of the patient, the sensors are placed to sense differential changes in pressure with changes in posture.
This differential pressure change results from gravitational effects upon different points within the vascular system. For example, with pressure sensors in the ri~ht heart and the inferior vena cava of a supine patient, the pressure measurements are approximately the same.
However, when the patient is erect, the sensor in the inferior vena cava will measure a greater pressure than the sensor in the right heart. ~t is this pressure differential which -identifies the patient~as-erect.~
Because the sensors measure the actual pressure, the differential pressure changes continuously from completely supine to completely erect. Therefore, a patient's differential pressure measurement when sitting up can be distinguished from measurements taken when either supine or erect. Other posture variations can be detected as well.
A further advantage of determining posture with differential pressure is that factors which result in equal pressure changes to all of the sensors are cancelled out and thereby eliminated. Typical of these factors are differences in altitude and atmospheric pressure. Also eliminated in this way are transients such as e~perienced in coughing or sneezing.
The posture measurement may be used in a number of ways.
A typical application is in cardiac pacing. By assuming that an upright patient has a higher cardiac demand than a supine patient, the posture determination is readily used to increase pacing rate for patients in the upright posture.
Alternatively, the posture determination may be used to vary the drug delivery regimen of an implanted drug dispenser, for example, by increasing or initiating the dispensing of a cardiac or other druy. Generally, the invention may be useful ;: '~ ~: ' ' ' : ~
:.... . . . .
.:: , , :
,j. . .
, :,' ' ' ` ' ,~. ,, ~ `207~826 in conjunction with any implantable device which provides a therapeutic treatment to the body, for varying the treatment in response to postural changes.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects and features of the present invention will be more apparent as the same becomes further understood from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings and in which like reference numerals refer to like parts and wherein:
FIG. l is a schematic diagram showing placement of two pressure sensors in a patient in a supine position;
FIG. 2 is a schematic diagram showing placement of two .
pressure sensors in a patient in a partially seated position;
FIG. 3 is a schematic diagram showing preferred placement of two pressure sensors in the vascular system of a patient;
FIG. 4 is a block diagram of an implantable pulse generator incorporating circuitry to vary artificial pacing rate with posture changes determined by differential pressure measurement;
FIG. 5 is a graphic representation of the pressure measured by a single sensor in a patient changing posture;
and, FIG. 6 is a graphical representation of the pressure measurements taken from two sensors and the resulting differential.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention utilizes at least two chronically implantable pressure sensors positioned within the cardiovascular system. In the preferred mode, two pressure sensors are used, however, additional sensors may be employed in accordance with the teaching of the present invention. The pressure sensor taught in U.S. Patent No. 4,485,813 issued to Anderson, et al. and incorporated herein by reference is the sensor preferred for this application. Other suitable sensors .
, . . ':
:' . ' : , ' ':
.
WO91/lll3X Pcr/uss1/oo4l6 207~82~ ~' ~`
are taught in U.S. Patent No. 4,432,372 issued to Monroe and U.S. Patent No. 4,407,296 issued to Anderson, both of which are herein incorporated by reference.
FIG. 1 is a schematic view of a patient lo in a supine position. The patient 10 has two pressure sensors such as discussed above chronically implanted in the cardiovascular system. The first of these sensors is implanted in the right side of heart 12 using normal implant techniques. The second pressure sensor is implanted in the inferior vena cava at position 14. A linear distance 16 of L units separates the two pressure sensors. If the patient 10 is lying horizontally, the pressure sensed within heart 12 and in the ; inferior vena cava by the pressure sensor at position 14 will ` be approximately the same.
~ IG. 2 is a schematic view of patient 10 having the same chronically implanted pressure sensors. In this view, however, patient 10 is in a partially seated position. As can be seen in the drawing, the torso of patient 10 is inclined at an angle 18 from the horizontal. This causes the pressure sensor in heart 12 to be higher than the pressure sensor at ~ position 14. The distance in elevation may be computed from il the distance L between the sensor (see also Fig. 1) and the angle 1 of inclination of the torso. The difference in elevation 20 is L times the sine of angle 18.
i Using standard hydraulic principles, one can readily see that the pressure sensed within heart 12 will be less than that measured by the pressure sensor at position 14 by an amount proportional to elevation ~0. By measuring this pressure differential, the angle 18 can thus be estimated. In this way the degree to which the torso of patient 10 is erect can be estimated.
Notice that in this embodiment the pressure di~ferential of a fully seated patient 10 and a standing patient 10 cannot be distinguished. If it were necessary to make such a determination, the pressure sensor at position 14 must be ,, :
) i,:.:, ; . :. .
:"'. ' ' ' ' ' ' ' .
. ~ ", .. , , ' ' ' , .
.; .
,," , ' :.
WO91/1l~3X PCT/US91/00416 ..
207~826 moved below the torso into one of the legs. To do so, however, complicates the implant procedure, and so should be done only if that degree of precision is required for the application.
FIG. 3 is a schematic diagram of the two pressure sensors as implanted in the cardiovascular system. Heart 12 has pressure sensor 36 implanted within the right atrium as shown.
It is coupled via electrical lead 24 through the venous system to implantable pulse generator 22 in the same fashion as with transvenous cardiac pacing applications.
Similarly pressure sensor 32 is positioned in the inferior vena cava (see also Figs. 1 and 2). Pressure sensor - ~- 32 is electrically coupled to implantable pulse generator 22 via transvenous lead 30. Both leads 24 and 30 proceed through the subclavian vein 26 from implantable pulse generator 22 after entry at point 34. Entry to the right atrium of heart 12 is via superior vena cava 28.
In the preferred embodiment, implantable pulse generator 1 22 functions as an artificial cardiac pacer. The necessary i pacing lead is not shown for clarity. However, this application is to be understood as typical and not limiting of the scope of the present invention.
In the illustrated embodiment, the pressure sensors are located on two separate leads. However, in some cases, it may be desirable to locate both pressure sensors on the same lead.
Differential pressure sensing using a single pressure transd~icer as illustrated in the above cited U.S. Patent No.
4,407,296 rather than two separate pressure sensors may also be desirable in some circumstances.
¦ FIG. 4 is a block diagram of implantable pulse generator 22. Leads 24 and 30 are shown as transferring the signals from pressure sensors 36 and 32, respectively. Signal processors 102 and 104 amplify and integrate these signalsO
`~ The difference i pressure experienced by the two pressure sensors is determined by computed pressure differential .
:
' ~ , , : :
:' , .
:.. ; , : ,, , ~ . ' . .
W09l/lll38 PCT/US91tO0416 207~826 circuitry 106. This circuitry controls the escape interval timer 108 using standard voltage control oscillator circuitry.
The greater the pressure differential, the shorter the ~ -interval produced by escape interval tim~r 108.
Fig. 4 is intended to be exemplary of the general type of circuitry to be employed in the present invention. However, alternate circuitry may also be employed. For example, signal processors 102, 104 may function as low pass filters, or integration/filtering may be performed after computation of the pressure differential, as in an embodiment employing a ~
single, differential pressure transducer. ~-Sense a~plifier 110, inhibit logic 112, and stimulation pulse amplifier--114 operate as in a normal demand pacemakerO
Sensing and stimulation is provided using a standard transvenous pacing lead 100. The pacing output of implantable pulse generator 22 differs from the normal demand pacer only that the underlying artificial pacing rate is decreased as the pressures sensed by the two pressure senso~s (i.e. pressure sensors 32 and 36) are more nearly the same and increased as ~
the pressure differential is increased. ~`
FI~. 5 is a graphisal representation 40 of the idealized output of pressure sensor 32 with changes in patient posture.
~he projection along axis 4~ is the pressure sensed (and hence voltage output of the pressure sensor). The projection along axis 44 is the time over which a number of posture changes take place. The level at 52 shows the measurement when the patient is supine. The patient sits up at 46 resulting in level 48. The patient lies down again at 50 resulting in supine level 52. Notice with this idealized data that posture chan~es could be monitored with a single pressure sensor.
FIG. 6 is a graphical representation of the outputs of both pressure sensors and the computed pressure differential along the same time axis showing some typical transient conditions.
The upper chart shows the pressure level 60 measured by .~ , .. .
.
.. . , . :
W~91t11138 PCT/~S91/0~16 ~,~3 2074~26 pressure sensor 36 while patient l0 is supine. As the patient rises, the pressure measured by pressure sensor 36 actually decreases to level 62. The pressure increases at 64 and 66 are not related to posture changes. The increase at 64 is a short term transient such as a sneeze or cough. The change beginning at 66 and resulting in level 68 is of longer duration. It may be of physiological causes such as elevated central venous blood pressure or external causes such as a change in altitude (e.g. as in an airplane or elevator). In either situation, the non-posture change is detected as a pressure change by pressure sensor 36.
The middle graph shows the output of pressure sensor 32 over the same-time--period. Notice that the supine level is 70. As the patient l0 rises, it is detected as pressure increase 74 resulting in level 76. Transient pressure rise 78 and non-posture change pressure rise 80 resulting in new pressure level B2 are detected as with pressure sensor 36.
The bottom graph shows the pressure differential of the two pressure sensors. It corresponds to the output of computed pressure differential 106 (see also Fig. 4). Level 90 shows essentially no pressure differential. It corresponds to the time when patient l0 is in the supine position. In the preferred em~odiment this results in the longest escape interval (or the lowest underlying pacing rate). As the patient rises, the pressure differential is increased at 92 resulting in new level 94. This corresponds to a shorter escape interval.
Notice that the pressure differential curve does not contain transient 64/78 nor non-posture pressure change 66/80.
j This is because the different:ial remains the same when both sensors are subjected to the same non-posture pressure changes.
Other applications of the present invention are readily apparent to thos~ in the art without deviation from the scope of the claims hereto attached.
::
~ .-- - . .. . - ...... - . .. . . .,,: .. : .. . . .
.
,;
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Claims (11)
1. An apparatus comprising:
a. a plurality of pressure sensors positioned in the cardiovascular system; and b. means responsively coupled to said plurality of pressure sensors for computing the difference in pressure measured by at least two of said pressure sensors.
a. a plurality of pressure sensors positioned in the cardiovascular system; and b. means responsively coupled to said plurality of pressure sensors for computing the difference in pressure measured by at least two of said pressure sensors.
2. An apparatus according to claim 1 further comprising means responsively coupled to said computing means for determining the posture of a patient based upon the difference in pressure computed by said computing means.
3. An apparatus according to claim 2 wherein said plurality of pressure sensors is two pressure sensors.
4. An apparatus according to claim 3 wherein a first one of said two pressure sensors is positioned within the heart of said patient.
5. An apparatus according to claim 4 wherein a second one of said two pressure sensors is positioned within the inferior vena cava.
6. An apparatus according to claims 2, 3, 4, and 5 further comprising a cardiac pacer responsively coupled to said determining means wherein the pacing rate of said cardiac pacer is decreased whenever said determining means determines that said patient is supine.
7. An apparatus according to claim 6 wherein said cardiac pacer is a demand type cardiac pacer and wherein said pacing rate is decreased by increasing the escape interval of said cardiac pacer.
8. A method of determining the posture of a patient comprising:
a. implanting a plurality of pressure sensors in the cardiovascular system of said patient;
b. measuring the pressure at each of said plurality of pressure sensors;
c. determining the difference in pressure measured by at least two of said plurality of pressure sensors; and d. estimating to the posture of said patient as a result of the difference determined at said determining step.
a. implanting a plurality of pressure sensors in the cardiovascular system of said patient;
b. measuring the pressure at each of said plurality of pressure sensors;
c. determining the difference in pressure measured by at least two of said plurality of pressure sensors; and d. estimating to the posture of said patient as a result of the difference determined at said determining step.
9. In an implantable device for delivery of a therapeutic treatment to the body, the improvement comprising:
means for sensing a pressure differential between two differing points within the cardiovascular system, such that one of said points is above the other of said points when said patient is in an upright posture; and means responsive to the measurement of said pressure differential for varying said therapeutic treatment.
means for sensing a pressure differential between two differing points within the cardiovascular system, such that one of said points is above the other of said points when said patient is in an upright posture; and means responsive to the measurement of said pressure differential for varying said therapeutic treatment.
10. An implantable device according to claim 9 wherein said device is a cardiac pacemaker including means for generating stimulus pulses at a pacing rate, and wherein said varying means comprises means for varying said pacing rate.
11. A device according to claim 9 wherein said means for sensing said pressure differential comprises first and second pressure sensors located adjacent said first and second points.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US473,265 | 1990-01-31 | ||
| US07/473,265 US5040536A (en) | 1990-01-31 | 1990-01-31 | Intravascular pressure posture detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2074826A1 true CA2074826A1 (en) | 1991-08-01 |
Family
ID=23878846
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002074826A Abandoned CA2074826A1 (en) | 1990-01-31 | 1991-01-18 | Intravascular pressure posture detector |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5040536A (en) |
| EP (1) | EP0513182B1 (en) |
| JP (1) | JPH05505322A (en) |
| AU (1) | AU646841B2 (en) |
| CA (1) | CA2074826A1 (en) |
| DE (1) | DE69101547T2 (en) |
| WO (1) | WO1991011138A1 (en) |
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| US4802481A (en) * | 1984-07-19 | 1989-02-07 | Cordis Leads, Inc. | Apparatus for controlling pacing of a heart in response to changes in stroke volume |
| US4566456A (en) * | 1984-10-18 | 1986-01-28 | Cordis Corporation | Apparatus and method for adjusting heart/pacer rate relative to right ventricular systolic pressure to obtain a required cardiac output |
| DE3650261D1 (en) * | 1985-09-17 | 1995-04-13 | Biotronik Mess & Therapieg | Pacemaker. |
| EP0216725B1 (en) * | 1985-09-17 | 1993-12-01 | BIOTRONIK Mess- und Therapiegeräte GmbH & Co Ingenieurbüro Berlin | Pacemaker |
| US4691709A (en) * | 1986-07-01 | 1987-09-08 | Cordis Corporation | Apparatus for measuring velocity of blood flow in a blood vessel |
| US4777951A (en) * | 1986-09-19 | 1988-10-18 | Mansfield Scientific, Inc. | Procedure and catheter instrument for treating patients for aortic stenosis |
| US4886064A (en) * | 1987-11-25 | 1989-12-12 | Siemens Aktiengesellschaft | Body activity controlled heart pacer |
-
1990
- 1990-01-31 US US07/473,265 patent/US5040536A/en not_active Expired - Lifetime
-
1991
- 1991-01-18 DE DE69101547T patent/DE69101547T2/en not_active Expired - Fee Related
- 1991-01-18 EP EP91904200A patent/EP0513182B1/en not_active Expired - Lifetime
- 1991-01-18 AU AU72539/91A patent/AU646841B2/en not_active Ceased
- 1991-01-18 WO PCT/US1991/000416 patent/WO1991011138A1/en active IP Right Grant
- 1991-01-18 CA CA002074826A patent/CA2074826A1/en not_active Abandoned
- 1991-01-18 JP JP91504418A patent/JPH05505322A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0513182A1 (en) | 1992-11-19 |
| AU646841B2 (en) | 1994-03-10 |
| DE69101547T2 (en) | 1994-09-01 |
| JPH05505322A (en) | 1993-08-12 |
| DE69101547D1 (en) | 1994-05-05 |
| AU7253991A (en) | 1991-08-21 |
| US5040536A (en) | 1991-08-20 |
| EP0513182B1 (en) | 1994-03-30 |
| WO1991011138A1 (en) | 1991-08-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |