Method for minimally invasive calibration of implanted pressure transducers

• US 20040106874A1
• Filed: 05/13/2003
• Published: 06/03/2004
• Est. Priority Date: 05/14/2002
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Whiting, James, Eigler, Neal, Mann, Brian
• Granted Patent: US 7,195,594 B2
• Time in Patent Office: Days
• US Class Current: 600/486
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 2560/0257 using atmospheric pressure
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/418 lymph vessels, ducts or nodes
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/4884 inducing physiological or psychological stress, e.g. applications for stress testing

Abstract

This invention relates generally to apparatus and methods for the calibration of implanted pressure transducers. It is an object of several embodiments of the present invention to provide apparatus and methods for the calibration of one or more implanted pressure transducers implanted in the body of medical patients. Various embodiments of the present invention are particularly advantageous because they offer a calibration system that is less invasive than the systems currently available.

Claims

1. A method of calibrating a pressure measurement system at least partially in pressure communication with a site within a medical patient, comprising:

measuring a first pressure at a first location at least partially within the medical patient;

measuring a second pressure at a second location;

inducing one or more perturbations, wherein said one or more perturbations causes the first pressure to have a calculable relationship with the second pressure;

determining one or more adjustment factors based on said calculable relationship; and

adjusting said pressure measurement system based at least in part on said one or more adjustment factors.

2. The method of claim 1, wherein the step of adjusting said pressure measurement system occurs if said adjustment factor falls outside of a predetermined tolerance range.

3. The method of claim 2, wherein said tolerance range corresponds to medically insignificant pressure change.

4. The method of claim 1, wherein the step of adjusting said pressure measurement system comprises adjusting a processor.

5. The method of claim 4, wherein the step of adjusting said processor comprises storing a value based on said adjustment factor in a memory of said processor.

6. The method of claim 4, wherein the step of adjusting said processor comprises altering one or more algorithms in said processor based upon said adjustment factor.

7. The method of claim 4, wherein the step of adjusting said processor comprises adjusting one or more parameters, wherein said one or more parameters relates a raw pressure transducer signal to a measured pressure based upon said adjustment factor.

8. The method of claim 4, wherein the step of adjusting said processor comprises adjusting a processor located within the patient.

9. The method of claim 4, wherein the step of adjusting said processor comprises adjusting a processor located external to the patient.

10. The method of claim 1, wherein the first pressure is indicative of a left atrial pressure.

11. The method of claim 1, wherein the first pressure is indicative of a pulmonary venous pressure.

12. The method of claim 1, wherein the first pressure is indicative of a pulmonary capillary wedge pressure.

13. The method of claim 1, wherein the first pressure is indicative of a pulmonary artery pressure.

14. The method of claim 1, wherein the first pressure is indicative of a left ventricular pressure.

15. The method of claim 1, wherein the first pressure is indicative of a right atrial pressure.

16. The method of claim 1, wherein the first pressure is indicative of a right ventricular pressure.

17. The method of claim 1, wherein the first pressure is indicative of a central venous pressure.

18. The method of claim 1, wherein the first pressure is indicative of a systemic venous pressure.

19. The method of claim 1, wherein the first pressure is indicative of an arterial pressure.

20. The method of claim 1, wherein the first location is in the thoracic cavity.

21. The method of claim 1, wherein the first location is within any structure contained within the thoracic cavity.

22. The method of claim 1, wherein the first location is within any structure of the heart.

23. The method of claim 1, wherein the first location is within any cavity of the heart.

24. The method of claim 1, wherein the first location is the left atrium.

25. The method of claim 1, wherein the first location is the right atrium.

26. The method of claim 1, wherein the first location is the left ventricle.

27. The method of claim 1, wherein the first location is the night ventricle.

28. The method of claim 1, wherein the first location is a pulmonary vein.

29. The method of claim 1, wherein the first location is a pulmonary artery.

30. The method of claim 1, wherein the first location is the coronary sinus.

31. The method of claim 1, wherein the first location is the superior vena cava.

32. The method of claim 1, wherein the first location is the thoracic portion of a subclavian vein.

33. The method of claim 1, wherein the first location is the jugular vein.

34. The method of claim 1, wherein the first location is the intrathoracic portion of the inferior vena cava.

35. The method of claim 1, wherein the first location is the intrathoracic portion of any vein.

36. The method of claim 1, wherein the first location is the aorta.

37. The method of claim 1, wherein the first location is an intrathoracic portion of a system artery.

38. The method of claim 1, wherein the first location is an intrathoracic portion of a blood vessel.

39. The method of claim 1, wherein the first location is the pleural space.

40. The method of claim 1, wherein the first location is the pericardial space.

41. The method of claim 1, wherein the first location is the esophagus.

42. The method of claim 1, wherein the first location is the pulmonary parenchyma.

43. The method of claim 1, wherein the first location is the pulmonary airspaces.

44. The method of claim 1, wherein the first location is the upper airway of the nasopharynx.

45. The method of claim 1, wherein the first location is the intrathoracic portion of a lymphatic duct.

46. The method of claim 1, wherein the first location is selected from the group consisting of one or more sites within one or more of the following regions:

cranial cavity, ocular cavity, abdominal cavity, sinus cavity, subcutaneous tissue, hollow viscus or duct, parenchyma, pancreatic duct, bile duct, gallbladder, urinary system, and joint spaces.

47. The method of claim 1, wherein the first location is a site within the medical patient that can be modulated by a pressure perturbation.

48. The method of claim 47, wherein said site is selected from the group consisting of one or more of the following:

a body structure, an organ and a compartment.

49. The method of claim 1, wherein the second location is inside the mouth.

50. The method of claim 1, wherein the second location is inside a body orifice.

51. The method of claim 1, wherein the second location is inside a mouthpiece.

52. The method of claim 1, wherein the second location is external to the medical patient.

53. The method of claim 1, wherein the second location is the air passageway of the upper respiratory system.

54. The method of claim 1, wherein the second location is the air passageway of the lower respiratory system.

55. The method of claim 1, wherein the second location is in the thoracic cavity.

56. The method of claim 1, wherein the second location is within any structure contained within the thoracic cavity.

57. The method of claim 1, wherein the second location is within any structure of the heart.

58. The method of claim 1, wherein the second location is within any cavity of the heart.

59. The method of claim 1, wherein the second location is the left atrium.

60. The method of claim 1, wherein the second location is the right atrium.

61. The method of claim 1, wherein the second location is the left ventricle.

62. The method of claim 1, wherein the second location is the right ventricle.

63. The method of claim 1, wherein the second location is a pulmonary vein.

64. The method of claim 1, wherein the second location is a pulmonary artery.

65. The method of claim 1, wherein the second location is the coronary sinus.

66. The method of claim 1, wherein the second location is the superior vena cava.

67. The method of claim 1, wherein the second location is the thoracic portion of a subclavian vein.

68. The method of claim 1, wherein the second location is the thoracic portion of a jugular vein.

69. The method of claim 1, wherein the second location is the intrathoracic portion of the inferior vena cava.

70. The method of claim 1, wherein the second location is the intrathoracic portion of any vein.

71. The method of claim 1, wherein the second location is the aorta.

72. The method of claim 1, wherein the second location is an intrathoracic portion of a system artery.

73. The method of claim 1, wherein the second location is an intrathoracic portion of a blood vessel.

74. The method of claim 1, wherein the second location is the pleural space.

75. The method of claim 1, wherein the second location is the pericardial space.

76. The method of claim 1, wherein the second location is the esophagus.

77. The method of claim 1, wherein the second location is the pulmonary parenchyma.

78. The method of claim 1, wherein the second location is the pulmonary airspaces.

79. The method of claim 1, wherein the second location is the upper airway of the nasopharynx.

80. The method of claim 1, wherein the second location is the trachea.

81. The method of claim 1, wherein the second location is the major bronchus.

82. The method of claim 1, wherein said measuring the first pressure comprises using at least one pressure transducer to measure a gauge pressure.

83. The method of claim 1, wherein said measuring the first pressure comprises using at least one pressure transducer to measure an absolute pressure.

84. The method of claim 1, wherein said measuring the first pressure comprises using at least one pressure transducer to measure a pressure relative to an arbitrary reference pressure.

85. The method of claim 1, wherein the perturbation is a Valsalva maneuver.

86. The method of claim 1, wherein the step of calibrating said pressure measurement system comprises calibrating at least one pressure transducer.

87. The method of claim 1, wherein said calibrating is performed at different levels of perturbation.

88. The method of claim 1, wherein said calibrating is performed at different ambient pressures.

89. The method of claim 1, wherein said calibrating is performed at different external pressures.

90. The method of claim 1, further comprising providing instructions to the patient.

91. The method of claim 90, wherein the instructions to the patient are altered based on an ambient pressure range over which a calibration has been performed.

92. The method of claim 1, further comprising providing instructions to a practitioner.

93. The method of claim 1, further comprising signaling the patient with a signaling device.

94. The method of claim 92, wherein said signaling device comprises a signal selected from the group consisting of one or more of the following:

an instruction, a beep, a buzzer, a shock, a vibration, a flash, and a stimulus indicative of an instruction.

95. The method of claim 92, wherein said signaling device comprises a personal digital assistant.

96. The method of claim 92, wherein said signaling device comprises a graphical user interface.

97. The method of claim 92, wherein the signaling results in alteration of a therapy.

98. The method of claim 92, wherein the signaling advises the patient that calibration is required.

99. The method of claim 92, further comprising:

retaining information pertaining to a valid calibration range; and

requesting the patient to recalibrate the pressure measurement system when a current ambient pressure is outside a valid range.

100. The method of claim 99, wherein said requesting is performed only if a change in therapy is indicated, and said change in therapy is based at least in part on the second pressure.

101. The method of claim 92, wherein said signaling occurs when a temperature falls outside of a range.

102. The method of claim 1, wherein at least part of the measurement system is implanted in a patient with congestive heart failure.

103. The method of claim 1, further comprising providing a therapy to the patient.

104. The method of claim 102, wherein said therapy comprises a drug delivery system.

105. The method of claim 102, wherein said therapy comprises a pacing system.

106. The method of claim 102, wherein said therapy comprises a defibrillator.

107. The method of claim 1, wherein said inducing causes the first pressure to equal the second pressure at one or more identifiable points in time during the perturbation.

108. The method of claim 1, wherein said inducing comprises active performance by the patient.

109. The method of claim 1, wherein said inducing comprises application to a passive patient.

110. The method of claim 1, wherein said inducing further comprises an external application combined with active cooperation by the patient.

111. The method of claim 1, wherein the step of inducing a perturbation is selected from the group consisting of one or more of the following:

performing at least one Valsalva maneuver, performing a Mueller maneuver, applying positive pressure artificial ventilation, performing unassisted normal ventilation, applying assisted positive pressure artificial ventilation, performing forced rhythmic breathing, sneezing, humming, coughing, abdominal straining, applying insufflations of a body cavity, applying external mechanical pressure, applying external hydraulic pressure, applying external pneumatic pressure, applying an acceleration, applying a deceleration, applying a change in ambient air pressure, applying a change in ambient temperature, applying a change in body temperature, applying an internal mechanical pressure, applying an internal hydraulic pressure, and applying an internal pneumatic pressure.

112. The method of claim 111, wherein the forced rhythmic breathing is performed through a restricting orifice.

113. The method of claim 111, wherein the at least one Valsalva maneuver is further selected from the group consisting of one or more of the following:

performing multiple Valsalva maneuvers producing a plurality of distinct values of airway pressure during a plateau phase, performing phase I of a Valsalva maneuver, and performing phase II of a Valsalva maneuver.

114. The method of claim 111, wherein the step of performing unassisted normal ventilation is further selected from the group consisting of one or more of the following:

performing unassisted normal ventilation with a normal tidal volume, performing unassisted normal ventilation with an exaggerated respiratory volume, and performing unassisted normal ventilation with a maximal respiratory volume.

115. The method of claim 111, wherein the step of applying assisted positive pressure artificial ventilation is further selected from the group consisting of one or more of the following:

applying positive pressure artificial ventilation in held inspiration, applying assisted positive pressure artificial ventilation with a normal tidal volume, applying assisted positive pressure artificial ventilation with an exaggerated tidal volume, applying assisted positive pressure artificial ventilation with controlled stepping of the airway pressure, and applying assisted positive pressure artificial ventilation with concurrent application of abdominal pressure.

116. The method of claim 111, wherein the step of applying insufflations of a body cavity is further selected from the group consisting of one or more of the following:

applying insufflations of a body cavity with a gas, and applying insufflations of a body cavity with a liquid.

117. The method of claim 1, wherein the calculable relationship is an equality.

118. The method of claim 1, wherein the calculable relationship is the pressures at the first and second locations are equal at a specific interval of time.

119. The method of claim 1, wherein the calculable relationship is the pressures at the first and second locations are offset by a constant at a specific interval of time.

120. The method of claim 1, wherein the calculable relationship comprises at least one predicted pressure at the first location, wherein said at least one predicted pressure is modeled by a mathematical function.

121. The method of claim 1, wherein the calculable relationship is an experimentally verified relationship.

122. The method of claim 1, wherein the calculable relationship is the individual patient is their own control.

123. The method of claim 1, wherein the calculable relationship is a heuristic algorithm.

124. The method of claim 1, wherein the calculable relationship is a transfer function.

125. The method of claim 1, wherein the calculable relationship is a statistical model.

126. The method of claim 1, wherein the calculable relationship is a deterministic model.

127. The method of claim 1, wherein the calculable relationship is a relationship of sufficient accuracy for clinical diagnosis.

128. The method of claim 1, wherein the calculable relationship is a relationship within 5 mm Hg of a true pressure.

129. The method of claim 1, wherein the calculable relationship is a relationship that differs according to a physiologic state.

130. The method of claim 1, wherein the calculable relationship is a relationship that differs according to whether the patient is in compensated or decompensated heart failure.

131. The method of claim 1, wherein the calculable relationship is a relationship that differs according to whether the patient has received at least one medication.

132. The method of claim 131, wherein the at least one medication is a vasodilating drug.

133. The method of claim 132, wherein the vasodilating drug is nitroglycerin.

134. The method of claim 131, wherein the at least one medication is a drug that lowers cardiac filling pressures.

135. The method of claim 131, wherein the at least one medication is a drug whose action results in a more predictable calculable relationship.

136. The method of claim 1, wherein the calculable relationship is a relationship that comprises making measurements at substantially the same moment in time in the cardiac cycle.

137. The method of claim 1, wherein the calculable relationship is a relationship that comprises making measurements at substantially the same moment in time in the respiratory cycle.

138. The method of claim 1, further comprising:

generating a signal based upon said first pressure; and

transmitting said signal to a receiver.

139. The method of claim 138, wherein said transmitting comprises radio frequency inductive coupling.

140. The method of claim 138, wherein said transmitting comprises radio frequency communication.

141. The method of claim 138, wherein said transmitting comprises digital communication.

142. The method of claim 138, wherein said transmitting comprises analog communication.

143. The method of claim 138, wherein said receiver is a hand-held digital communication device.

144. The method of claim 138, wherein said receiver comprises a computer.

145. The method of claim 138, wherein said receiver comprises a telephone.

146. The method of claim 138, wherein said receiver comprises a personal digital assistant.

147. The method of claim 138, wherein said receiver comprises a monitor.

148. The method of claim 138, wherein said receiver comprises instructions for altering a therapy based upon said signal.

149. The method of claim 138, further comprising generating an instruction for altering a therapy based upon said signal.

150. The method of claim 1, wherein said pressure measurement system comprises a pacemaker.

151. The method of claim 1, wherein said pressure measurement system comprises a defibrillator.

172. The method of claim 1, wherein said second pressure is indicative of an upper airway pressure.

152. A method for calibrating a pressure measurement system in pressure communication with a site inside a medical patient comprising:

measuring a first pressure in a first location, said first location at least partially within the medical patient;

measuring at least one second pressure in at least one second location within or on said medical patient with a calibrated pressure measurement system;

inducing a perturbation of pressure substantially simultaneously at the first and at least one second locations such that the pressure measured at the at least one second location is predictive of a true pressure at the first location by a calculable relationship; and

comparing the first pressure and a prediction of the true pressure at the first location to establish at least one calibration parameter of the pressure measuring system.

153. The method of claim 152, wherein the first pressure is indicative of a left atrial pressure.

154. The method of claim 152, wherein the first location is in the thoracic cavity.

155. The method of claim 152, wherein the first location is the left atrium.

156. The method of claim 152, wherein the second location is inside the mouth.

157. The method of claim 152, wherein the second location is in pressure communication with the upper airway.

158. The method of claim 152, wherein the second location is in the thoracic cavity.

159. The method of claim 152, wherein the second location is in the mouth.

160. The method of claim 152, wherein said inducing causes the first pressure to equal the second pressure at one or more identifiable points in time during the perturbation.

161. The method of claim 152, wherein the perturbation is a Valsalva maneuver.

162. The method of claim 152, wherein said calibration is performed at different levels of perturbation.

163. The method of claim 152, wherein the pressure measurement system comprises a first pressure transducer, wherein said first pressure transducer is implanted in the patient, and said medical patient has congestive heart failure.

164. The method of claim 152, wherein the calculable relationship is an equality.

165. The method of claim 152, wherein the calculable relationship is the pressures at the first and at least one second locations are equal at a specific interval of time.

166. The method of claim 152, further comprising:

generating a signal based upon said first pressure; and

transmitting said signal to a receiver.

167. The method of claim 166, wherein said transmitting comprises radio frequency inductive coupling.

168. The method of claim 166, wherein said receiver is a hand-held digital communication device.

169. The method of claim 166, wherein said receiver comprises a computer.

170. The method of claim 166, wherein said receiver comprises a telephone.

171. The method of claim 166, wherein said receiver comprises a personal digital assistant.

173. A method of calibrating a pressure measurement system located inside of a medical patient, comprising:

measuring a first pressure at a first location, said first location located anywhere within the thoracic cavity;

measuring a second pressure at a second location that communicates with the thoracic cavity;

inducing a perturbation, wherein said perturbation causes the first pressure to have a calculable relationship with the second pressure; and

calibrating said first pressure based at least in part on said calculable relationship.

174. The method of claim 173, wherein said first location communicates with an organ situated within the thoracic cavity.

175. The method of claim 173, wherein said first location communicates with an structure situated within the thoracic cavity.

176. The method of claim 173, wherein said second location communicates with an organ situated within the thoracic cavity.

177. The method of claim 173, wherein said second location communicates with an structure situated within the thoracic cavity.

178. A method for calibrating a pressure measurement system located inside of a medical patient comprising:

measuring a first pressure in a first location, said first location located anywhere within the thoracic cavity;

measuring at least one second pressure in at least one second location that communicates with the thoracic cavity;

inducing a perturbation of pressure substantially simultaneously at the first and at least one second locations such that the pressure measured at the at least one second location is predictive of a true pressure at the first location by a calculable relationship; and

using a difference between the first pressure and a prediction of true pressure at the first location to establish at least one calibration parameter of the pressure measuring system.

179. The method of claim 178, wherein said first location communicates with an organ situated within the thoracic cavity.

180. The method of claim 178, wherein said first location communicates with a structure situated within the thoracic cavity.

181. The method of claim 178, wherein said second location communicates with an organ situated within the thoracic cavity.

182. The method of claim 178, wherein said second location communicates with a structure situated within the thoracic cavity.

183. A method of calibrating a pressure measurement system located at least partially inside of a medical patient, comprising:

measuring a first pressure at a first location, said first location located at least partially inside the medical patient;

measuring a second pressure at a second location;

inducing a perturbation, wherein said perturbation causes the first pressure to have a calculable relationship with the second pressure; and

calibrating said first pressure to said second pressure based at least in part on said calculable relationship.

184. The method of claim 183, wherein said first and second pressures are calibrated to an absolute pressure.

185. A method of calibrating a pressure measurement system located inside of a medical patient comprising:

measuring a first pressure in a first location, said first location located within the thoracic cavity;

measuring at least one second pressure in at least one second location, wherein said second location is in pressure communication with the thoracic cavity;

inducing a perturbation of pressure substantially simultaneously at the first and at least one second locations, wherein said at least one second pressure indicates a true pressure at the first location by a calculable relationship;

determining a calibration difference between the first pressure and the at least one second pressure; and

adjusting said pressure measurement system based at least in part on said calibration difference.

186. A method of monitoring the calibration of a pressure measurement system located at least partially inside of a medical patient, comprising:

recording a first atmospheric pressure at a first time;

recording a second atmospheric pressure after a sampling period;

calculating the difference between the first atmospheric pressure and the second atmospheric pressure; and

providing an instruction to said medical patient based upon said difference.

187. The method of claim 186, wherein said instruction is to recalibrate said pressure measurement system.

188. The method of claim 186, wherein said instruction is to contact a medical care provider.

189. A method of calibrating a pressure measurement system at least partially in pressure communication with a site within a medical patient, comprising:

measuring a first pressure at a first location, said first location at least partially within the medical patient;

measuring a second pressure at a second location;

inducing a perturbation;

comparing said first pressure to said second pressure;

determining an adjustment factor based on the comparison; and

adjusting said pressure measurement system based at least in part on said adjustment factor.

190. The method of claim 189, wherein the step of adjusting said pressure measurement system occurs if said adjustment factor falls outside of a predetermined range.

191. A method of calibrating a pressure measurement system at least partially in pressure communication with a site within a medical patient, comprising:

measuring a first pressure at a first location, said first location within the medical patient;

measuring a second pressure at a second location;

inducing a first perturbation at a first level, wherein said first perturbation causes the first pressure to have a calculable relationship with the second pressure;

inducing at least one second perturbation at at least one second level, wherein said at least one second perturbation causes the first pressure to have said calculable relationship with the second pressure, and wherein said at least one second level is not equal to said first level;

determining one or more adjustment factors based on said calculable relationship; and

adjusting said pressure measurement system based at least in part on said one or more adjustment factors.

192. The method of claim 191, wherein the step of adjusting said pressure measurement system occurs if said one or more adjustment factors fall outside of a predetermined tolerance range.