Method and apparatus for vascular testing

• US 5,050,613 A
• Filed: 09/15/1989
• Issued: 09/24/1991
• Est. Priority Date: 09/15/1989
• Status: Expired due to Fees

• Current Assignee: Imex Corporation
• Original Assignee: Imex Corporation
• Inventors: Jones, David C., Newman, Dennis, Steffenson, Gary G., Schmitz, Alan R., Self, George E., Wing, Scott N., Willenbring, Angela G.
• Primary Examiner(s): Jaworski, Francis
• Assistant Examiner(s): MANUEL, GEORGE C
• Application Number:
  US07/408,060
• Time in Patent Office: 739 Days
• Field of Search: 128/670, 128/677, 128/691, 128/694, 128/679
• US Class Current: 600/483
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/7435 Displaying user selection data, e.g. icons in a graphical user interface

Abstract

An automated vascular testing apparatus includes capillary blood flow sensors and blood pressure detection sensors to detect data regarding the blood flow of a patient. Error detection apparatus insures that the blood data sensors are properly connected and that the output signals therefrom are reliable and provide an adequate basis for measurement. A controller monitors the output signals from the sensors and manages the overall operation of the automated testing procedures. The controller memory temporarily stores the output signals from the blood data sensors, along with other miscellaneous data. A video display presents instructions, data, and conclusions based on accepted medical theories to the operator, while a printer optionally reproduces these data in hard copy form.

Claims

1. Vascular testing apparatus for determining the vascular condition of a patient, comprising:

capillary blood flow detection means for detecting changes in the capillary blood flow of the patient and for generating capillary blood flow signals indicative of changes in the capillary blood flow of the patient;

blood pressure detection means for detecting changes in the blood pressure of the patient and for generating blood pressure signals indicative of changes in the blood pressure of the patient;

error detection means connected to said capillary blood flow detection means and to said blood pressure detection means for detecting whether said capillary blood flow detection means and said blood pressure detection means are functioning properly and that said capillary blood flow detection means and said blood pressure detection means are properly connected to the patient;

display means having a scale for selectively displaying the capillary blood flow signals and the blood pressure signals;

memory means for storing the capillary blood flow signals and the blood pressure signals;

reproducing means for reproducing the capillary blood flow signals and the blood pressure signals in hard copy form; and

,

control means connected to said error detection means, said display means, said memory means, and said reproducing means for controlling and coordinating the operation thereof.

2. The vascular testing apparatus of claim 1 further comprising query means connected to said control means for querying an operator for a plurality of input data items.

3. The vascular testing apparatus of claim 2 further comprising instruction means connected to said control means and to said display means for displaying step-by-step instructions on the set-up and operation of said vascular testing apparatus.

4. The vascular testing apparatus of claim 3 further comprising hardware calibration means connected to said control means for automatically calibrating said blood flow detection means and said blood pressure detection means.

5. The vascular testing apparatus of claim 4 further comprising heart rate detection means connected to said control means for detecting the heart rate of the patient and for generating heart rate signals indicative of the heart rate of the patient.

6. The vascular testing apparatus of claim 5 wherein said capillary blood flow detection means further comprises photoplethysmography (PPG) transducer means for optically detecting changes in the capillary blood flow of the patient and for generating the capillary blood flow signals.

7. The vascular testing apparatus of claim 6 wherein said blood pressure detecting means further comprises pneumoplethysmography (PCR) transducer means for pneumatically detecting the blood pressure of the patient and for generating the blood pressure signals.

8. The vascular testing apparatus of claim 7 wherein said pneumoplethysmography (PCR) transducer means comprises:

a pressure cuff;

pump means pneumatically connected to said pressure cuff and connected to said control means for inflating said pressure cuff;

valve means pneumatically connected to said pressure cuff and connected to said control means for deflating said pressure cuff; and

,

pressure transducer means pneumatically connected to said pressure cuff and to said control means for generating said blood pressure signals for said control means that are proportional to the pressure in said pressure cuff.

9. The vascular testing apparatus of claim 8, wherein said error detection means includes means to determine whether the patient is properly physically prepared for the testing procedure.

10. The vascular testing apparatus of claim 9, wherein said control means further comprises:

resizing means for automatically resizing the scale of said display means;

caliper placing means for automatically placing calipers at predetermined locations on said display means;

signal plateau detection means for detecting, according to a predetermined set of conditions, a plateau in the capillary blood flow signals and in the blood pressure signals.

11. The heart rate detection means of claim 5 further comprising:

slope detection means for determining the presence of signal peaks in the capillary blood flow signals; and

time calculation means for calculating an elapsed time between the signal peaks.

12. A method of determining the Ankle-Brachial Index Ratio (ABI ratio) of a patient with the aid of a computer including a brachial photoplethysmography (PPG) transducer for generating brachial blood flow signals having a plurality of signal peaks indicative of the brachial capillary blood flow and an ankle photoplethysmography (PPG) transducer for generating ankle blood flow signals having a plurality of signal peaks indicative of the changing ankle capillary blood flow of the patient, comprising the steps of:

determining the heart rate of the patient;

simultaneously inflating a brachial pressure cuff and an ankle pressure cuff, said brachial pressure cuff generating brachial blood pressure signals indicative of the brachial blood pressure of the patient and said ankle pressure cuff generating ankle blood pressure signals indicative of the ankle blood pressure of the patient;

continuously monitoring and displaying the brachial blood pressure signals and the ankle blood pressure signals;

determining when the brachial arteries and the ankle arteries of the patient have been occluded;

stopping the inflation of the brachial pressure cuff and the ankle pressure cuff when the respective brachial or ankle arteries have been occluded;

deflating the brachial pressure cuff and the ankle pressure cuff at a predetermined rate;

detecting when the brachial and the ankle arteries of the patient have re-opened;

storing and displaying the brachial blood pressure signals and the ankle blood pressure signals at the instant each respective brachial and ankle artery has re-opened;

deflating the brachial pressure cuff and the ankle pressure cuff;

calculating an ABI ratio; and

,

displaying said ABI ratio.

13. The method of determining the Ankle-Brachial Index ratio of a patient of claim 12, wherein the step of displaying the brachial blood pressure signals and the ankle blood pressure signals further includes the step of continually updating the display of the brachial blood pressure signals and the ankle blood pressure signals.

14. The method of determining the Ankle-Brachial Index ratio of a patient of claim 13, wherein the step of determining when the brachial arteries and the ankle arteries are occluded is defined further to include the steps of:

determining a brachial maximum peak amplitude from the plurality of signal peaks, each of which has a brachial signal peak amplitude, from said brachial blood flow signals, and determining an ankle maximum peak amplitude from the plurality of signal peaks, each of which has an ankle signal peak amplitude, from said ankle blood flow signals;

calculating a brachial occlusion cut-off value and an ankle occlusion cut-off value based on the brachial maximum peak amplitude and on the ankle maximum peak amplitude, respectively;

comparing the brachial signal peak amplitude of the signal peaks from the brachial blood flow signals with the ankle signal peak amplitude of the signal peaks from the ankle blood flow signals as the brachial and ankle pressure cuffs are inflated and comparing the amplitude of each respective brachial and ankle signal peak to the previously determined corresponding brachial and ankle occlusion cut-off value; and

finding arterial occlusion when the amplitude of each respective brachial and ankle signal peak is less than or equal to the corresponding brachial and ankle occlusion cut-off value.

15. The method of claim 14, wherein the brachial occlusion cut-off value is about 75% of the brachial maximum peak amplitude and the ankle occlusion cut-off value is about 75% of the ankle maximum peak amplitude.

16. The method of determining the Ankle-Brachial Index ratio of a patient of claim 15 wherein the step of determining when the brachial arteries and the ankle arteries have re-opened is defined further to include the steps of:

continuously monitoring the brachial blood flow signals and the ankle blood flow signals after arterial occlusion has been found for both the brachial and ankle arteries for signal peaks that have a positive slope for a predetermined period of time; and

determining whether a predetermined number of sequential signal peaks also have positive slopes for the predetermined period of time and also occur within a certain predetermined time frame of the previously calculated heart rate.

17. The method of claim 16, wherein the predetermined period of time is greater than or equal to about 48 milliseconds and less than about 180 milliseconds.

18. The method of claim 16, wherein the predetermined time frame of the previously calculated heart beat rate is defined to be about +/- 25% of the time around an expected time of an occurrence of a signal peak based on the previously calculated heart beat rate.

19. The method of determining the Ankle-Brachial Index ratio of claim 12, further comprising the step of continuously monitoring and storing the ankle blood pressure signals for a predetermined time before fully deflating the ankle pressure cuff.

20. The method of determining the Ankle-Brachial Index of a patient of claim 12 further comprising the step of:

printing the test data and results in hard copy form.

21. A method of determining the competency of the valves in the leg veins in the leg of a patient, with the aid of a computer, comprising the steps of:

determining, in response to blood pressure signals from an occlusive cuff pressure value occurring when an occlusive cuff is inflated, that the leg veins in the leg of the patient are fully filled with blood;

continuously monitoring the blood pressure signals and displaying the blood pressure signals on a continuous scaled display;

curing the patient to flex his leg at predetermined flex intervals, including a first and last flex interval, and for a predetermined number of times;

rescaling the continuous scaled display of the blood pressure signals if necessary;

determining, in response to the blood pressure signals, when the veins in the leg of the patient have refilled with blood;

calculating an elapsed time between the last of said predetermined number of flex intervals and when the leg veins have refilled with blood; and

,

displaying the elapsed time.

22. The method of determining the competency of the leg veins of a patient of claim 21 wherein, both the right leg and the left leg of the patient are tested simultaneously.

23. The method of determining the competency of the leg veins of a patient of claim 21, further comprising the steps of:

comparing, in relation to established medical elapsed time ranges indicating a normal refill time, said elapsed time for the leg veins to refill and determining whether said elapsed time is normal; and

,

displaying a recommendation for further testing if said elapsed time is not normal.

24. The method of determining the competency of the valves in the leg veins of a patient of claim 21, wherein the step of determining, in response to the blood pressure signals, when the veins in the leg of the patient have refilled with blood is further defined to include the steps of:

determining, in response to the blood pressure signals from the occlusive cuff pressure value occurring when the occlusive cuff is inflated, a baseline level of the amount of blood in the leg veins of the patient before cuing the patient to flex his leg;

continuously monitoring the blood pressure signals after the last of said leg flex intervals and determining a rate of change with time in the amount of blood in the leg veins of the patient;

determining when the rate of change is below a predetermined amount; and

,

determining when the amount of blood in the leg veins of the patient has returned within a predetermined amount of the baseline level.

25. The method of determining the competency of the valves in the leg veins of a patient of claim 24, further comprising the step of placing first and second calipers on said continuous scaled display, said first caliper being placed on the continuous scaled display of the blood pressure signals to indicate the time of the last of said leg flex intervals, and said second caliper being placed on the continuous scaled display to indicate when the amount of blood in the leg veins of the patient has returned within the predetermined amount of the baseline level.

26. The method of determining the competency of the valves in the leg veins of a patient of claim 25, further comprising the step of printing out the continuous display of the amount of blood in the leg veins of the patient and printing out the refill time.

27. A method of determining the sufficiency of the venous outflow in the leg veins of a patient, the leg having a venous system and an arterial system, comprising the steps of:

determining, in response to calf blood pressure signals from an occlusive calf cuff pressure value occurring when an occlusive calf cuff is inflated, a baseline blood capacity level;

displaying said calf blood pressure signals on a display for a predetermined time, then pausing said display;

inflating a thigh pressure cuff to a pressure sufficient to occlude the venous system of the leg, but not the arterial system;

detecting, in response to said calf blood pressure signals, a venous capacitance level;

restarting said display indicating said calf blood pressure signals;

rapidly deflating said thigh pressure cuff;

continuously monitoring and displaying said calf blood pressure signals of the patient'"'"'s leg;

determining, from said calf blood pressure signals, a final blood capacitance value indicating the amount of blood remaining in the leg venous system after a predetermined amount of time and subtracting the value indicating the amount of blood remaining in the leg venous system from the venous capacitance level to yield a maximum venous outflow value;

calculating a maximum venous outflow ratio by dividing the maximum venous outflow value by the venous capacitance level; and

,

displaying the maximum venous outflow ratio on said display.

28. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 27, further comprising the step of printing said display of the calf blood pressure signals and the maximum venous outflow ratio in hard copy form.

29. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 28, further comprising the step of preparing the leg veins of the patient for the test by pre-stretching the leg veins of the patient.

30. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 27, wherein the step of determining the venous capacitance further comprises the steps of:

monitoring the rate of change of the calf blood pressure signals; and

,

determining the venous capacitance level when said rate of change falls below a predetermined amount.

31. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 30, further comprising the step of placing calipers on the display of the calf blood pressure signals to indicate the baseline blood capacity level, the venous capacitance level, a time when the thigh pressure cuff was deflated, and the final blood capacitance level.

32. Vascular testing apparatus for determining the vascular condition of a patient, comprising:

photoplethysmography (PPG) transducer means for optically detecting changes in the capillary blood flow of the patient and for generating capillary blood flow signals indicative of the changes in the capillary blood flow of the patient;

blood pressure detection means for detecting changes in the blood pressure of the patient and for generating blood pressure signals indicative of the changes in the blood pressure of the patient;

error detection means connected to said photoplethysmography transducer means and to said blood pressure detection means for detecting whether said photoplethysmography transducer means and said blood pressure detection means are functioning properly and that said photoplethysmography transducer means and said blood pressure detection means are properly connected to the patient;

display means having a scale for selectively displaying the capillary blood flow signals and the blood pressure signals;

memory means for storing the capillary blood flow signals and the blood pressure signals;

reproducing means for reproducing the capillary blood flow signals and the blood pressure signals in hard copy form;

control means connected to said error detection means, said display means, said memory means, and said reproducing means for controlling and coordinating the operation thereof;

query means connected to said control means for querying an operator for a plurality of input data items;

instruction means connected to said control means and to said display means for displaying step-by-step instructions on the set-up and operation of said vascular testing apparatus;

hardware calibration means connected to said control means for automatically calibrating said blood flow detection means and said blood pressure detection means; and

heart rate detection means connected to said control means for detecting the heart rate of the patient and for generating heart rate signals indicative of the heart rate of the patient.

33. The vascular testing apparatus of claim 32 wherein said blood pressure detecting means further comprises pneumoplethysmography (PCR) transducer means for pneumatically detecting the blood pressure of the patient and for generating the blood pressure signals.

34. The vascular testing apparatus of claim 33 wherein said pneumoplethysmography (PCR) transducer means comprises:

a pressure cuff;

pump means pneumatically connected to said pressure cuff and connected to said control means for inflating said pressure cuff;

valve means pneumatically connected to said pressure cuff and connected to said control means for deflating said pressure cuff; and

pressure transducer means pneumatically connected to said pressure cuff and to said control means for generating said blood pressure signals for said control means that are proportional to the pressure in said pressure cuff.

35. The vascular testing apparatus of claim 34, wherein said control means further comprises:

resizing means for automatically resizing the scale of said display means;

caliper placing means for automatically placing calipers at predetermined locations on said display means;

signal plateau detection means for detecting, according to a predetermined set of conditions, a plateau in the capillary blood flow signals and in the blood pressure signals.

36. The heart rate detection means of claim 32 further comprising:

slope detection means for determining the presence of signal peaks in the capillary blood flow signals; and

time calculation means for calculating an elapsed time between the signal peaks.

37. A method of determining the Ankle-Brachial Index Ratio (ABI ratio) of a patient with the aid of a computer including a brachial photoplethysmography (PPG) transducer for generating brachial blood flow signals having a plurality of signal peaks indicative of the brachial capillary blood flow and an ankle photoplethysmography (PPG) transducer for generating ankle blood flow signals having a plurality of signal peaks indicative of the changing ankle capillary blood flow of the patient, comprising the steps of:

determining the heart rate of the patient;

simultaneously inflating a brachial pressure cuff and an ankle pressure cuff, said brachial pressure cuff generating brachial blood pressure signals indicative of the brachial blood pressure of the patient and said ankle pressure cuff generating ankle blood pressure signals indicative of the ankle blood pressure of the patient;

continuously monitoring and displaying the brachial blood pressure signals and the ankle blood pressure signals and continually updating the display of the brachial blood pressure signals and the ankle blood pressure signals;

determining when the brachial arteries and the ankle arteries of the patient have been occluded by determining a brachial maximum peak amplitude from the plurality of signal peaks, each of which has a brachial signal peak amplitude, from said brachial blood flow signals, and determining an ankle maximum peak amplitude from the plurality of signal peaks, each of which has an ankle signal peak amplitude, from said ankle blood flow signals;

calculating a brachial occlusion cut-off value and an ankle occlusion cut-off value based on the brachial maximum peak amplitude and on the ankle maximum peak amplitude, respectively, wherein the brachial occlusion cut-off value is about 75% of the brachial maximum peak amplitude and the ankle occlusion cut-off value is about 75% of the ankle maximum peak amplitude;

comparing the brachial signal peak amplitude of the signal peaks from the brachial blood flow signals with the ankle signal peak amplitude of the signal peaks from the ankle blood flow signals as the brachial and ankle pressure cuffs are inflated and comparing the amplitude of each respective brachial and ankle signal peak to the previously determined corresponding brachial and ankle occlusion cut-off value; and

finding arterial occlusion when the amplitude of each respective brachial and ankle signal peak is less than or equal to the corresponding brachial and ankle occlusion cut-off value;

stopping the inflation of the brachial pressure cuff and the ankle pressure cuff when the respective brachial or ankle arteries have been occluded;

deflating the brachial pressure cuff and the ankle pressure cuff at a predetermined rate;

detecting when the brachial and the ankle arteries of the patient have re-opened by continuously monitoring the brachial blood flow signals and the ankle blood flow signals after arterial occlusion has been found for both the brachial and ankle arteries for signal peaks that have a positive slope for a predetermined period of time that is greater than or equal to about 48 milliseconds and less than about 180 milliseconds;

determining whether a predetermined number of sequential signal peaks also have positive slopes for the predetermined period of time and also occur within a certain predetermined time frame of the previously calculated heart rate;

storing and displaying the brachial blood pressure signals and the ankle blood pressure signals at the instant each respective brachial and ankle artery has reopened;

deflating the brachial pressure cuff and the ankle pressure cuff;

calculating an ABI ratio; and

displaying said ratio.

38. The method of claim 37 wherein the predetermined time frame of the previously calculated heart rate is defined to be about +/- 25% of the time around an expected time of an occurrence of a signal peak based on the previously calculated heart rate.

39. A method of determining the competency of the valves in leg veins in a leg of a patient with the aid of a computer, comprising the steps of:

determining, in response to blood pressure signals from an occlusive cuff pressure value occurring when an occlusive cuff is inflated, that the leg veins in the leg of the patient are fully filled with blood by determining, in response to the blood pressure signals from the occlusive cuff pressure value occurring when the occlusive cuff is inflated, a baseline level of the amount of blood in the leg veins of the patient before cuing the patient to flex his leg;

continuously monitoring the blood pressure signals after the last of said leg flex intervals and determining a rate of change with time in the amount of blood in the leg veins of the patient;

determining when the rate of change is below a predetermined amount; and

determining when the amount of blood in the leg veins of the patient has returned within a predetermined amount of the baseline level;

continuously monitoring the blood pressure signals and displaying the blood pressure signals on a continuous scaled display;

cuing the patient to flex his leg at predetermined flex intervals, including a first and last flex interval, and for a predetermined number of times;

rescaling the continuous scaled display of the blood pressure signals, if necessary;

determining, in response to the blood pressure signals, when the veins in the leg of the patient have refilled with blood;

calculating an elapsed time between the last of said predetermined number of flex intervals and when the leg veins have refilled with blood;

displaying the elapsed time; and

placing first and second calipers on said continuous scaled display, said first caliper being placed on the continuous scaled display of the blood pressure signals to indicate the time of the last of said leg flex intervals, and said second caliper being placed on the continuous scaled display to indicate when the amount of blood in the leg veins of the patient has returned within the predetermined amount of the baseline level.

40. The method of determining the competency of the valves in the leg veins of a patient of claim 39, further comprising the step of printing out the continuous display of the amount of blood in the leg veins of the patient and printing out the refill time.

41. A method of determining the sufficiency of the venous outflow in the leg veins of a patient, the leg having a venous system and an arterial system, with the aid of a computer, comprising the steps of:

preparing the leg veins of the patient for the test by pre-stretching the leg veins of the patient;

determining, in response to calf blood pressure signals from an occlusive calf cuff pressure value occurring when an occlusive calf cuff is inflated, a baseline blood capacity level;

displaying said calf blood pressure signals on a display for a predetermined time, then pausing said display;

inflating a thigh pressure cuff to a pressure sufficient to occlude the venous system of the leg, but not the arterial system;

detecting, in response to said calf blood pressure signals, a venous capacitance level;

restarting said display indicating said calf blood pressure signals;

rapidly deflating said thigh pressure cuff;

continuously monitoring and displaying said calf blood pressure signals of the patient'"'"'s leg;

determining, from said calf blood pressure signals, a final blood capacitance value indicating the amount of blood remaining in the leg venous system after a predetermined amount of time and subtracting the value indicating the amount of blood remaining in the leg venous system from the venous capacitance level to yield a maximum venous outflow value;

calculating a maximum venous outflow ratio by dividing the maximum venous outflow value by the venous capacitance level;

displaying the maximum venous outflow ratio on said display; and

printing said display of the calf blood pressure signals and the maximum venous outflow ratio in hard copy form.

42. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 41, wherein the step of determining the venous capacitance further comprises the steps of:

monitoring the rate of change of the calf blood pressure signals; and

determining the venous capacitance level when said rate of change falls below a predetermined amount.

43. The method of determining the sufficiency of the venous outflow in the leg veins of a patient of claim 42, further comprising the step of placing calipers on the display of the calf blood pressure signals to indicate the baseline blood capacity level, the venous capacitance level, a time when the thigh pressure cuff was deflated, and the final blood capacitance level.