BIME-MEDE302- Lecture Note 1- BP Measurement- SP 24-25.pptx

Biomedical engineering

1. BIME302 PHYSOLOGICAL SIGNALS & INSTRUMENTATION LECTURER: ASST. PROF. DR. ALİ IŞIN Lecture Note 1 : Blood Pressure Measurement FACULTY OF ENGINEERING DEPARTMENT OF BIOMEDICAL ENGINEERING BIME302 Lecture Note 1-2025

2. Blood Pressure An Individuals blood pressure is a standard clinical measurement Is considered a good indicator of the status of the cardiovascular system. Blood pressure values in the various chambers of the heart and in the peripheral vascular system help the physician determine the functional integrity of the cardio vascular system. BIME302 Lecture Note 1-2025

3. Blood Pressure inside the heart chambers BIME302 Lecture Note 1-2025

4. Major Arteries & Veins of the Body BIME302 Lecture Note 1-2025

5. Cardiovascular system-typical values BIME302 Lecture Note 1-2025

6. Blood Pressure Measurement Direct (invasive) Extravascular Method The vascular pressure is coupled to an external sensor element via a liquid filled catheter. [Catheter – is a long tube introduced into the heart or a major vessel by way of a superficial vein or artery.] 2. Intravascular A sensor is placed into the tip of a catheter that is placed in the vascular system. Indirect (non invasive) Sphygmomanometer Consists of an inflatable pressure cuff and a manometer to measure the pressure in the cuff. BIME302 Lecture Note 1-2025

7. Direct Measurement (Extravascular) BIME302 Lecture Note 1-2025

8. Disposable blood-pressure sensor with integral flush device BIME302 Lecture Note 1-2025

9. Direct Measurement Extra Vascular The extra vascular sensor system is made up of a catheter. The catheter is connected to a three way stopcock and then to a pressure sensor It is filled with a saline-heparin solution. It must be flushed with solution every few minutes to prevent blood clotting at the tip. BIME302 Lecture Note 1-2025

10. Physician inserts the catheter Either by means of a surgical cut-down , which exposes the artery or vein. or by means of percutaneous insertion which involves the use of a special needle or guide-wire technique. Blood pressure is transmitted via the catheter column to the sensor and finally to the diaphragm which is deflected. The displacement of the diaphragm is sensed electronically. Direct Measurement Extra Vascular contd … BIME302 Lecture Note 1-2025

11. Disadvantages The frequency response of the catheter-sensor system is limited by the hydraulic properties of the system. Creates time delay in detection of pressures when a pressure pulse is transmitted. Direct Measurement Extra Vascular contd … BIME302 Lecture Note 1-2025

12. The sensor is placed at the tip of the catheter. Enables the physician to obtain a high frequency response in detection of pressures at the tip of the catheter. Types of sensors Strain-gage systems bonded onto a flexible diaphragm at the catheter tip. Fibre -optic device Measures the displacement of the diaphragm optically by varying reflection of light from the back of the deflecting diaphragm. Direct Measurement Intravascular BIME302 Lecture Note 1-2025

13. Bonded Strain Gage pressure transducer Consists of strain-sensitive gages which are firmly bonded with an adhesive to the membrane or diaphragm whose movement is to be recorded. Made by taking a length of a very thin wire or foil which is formed into a grid pattern and bonded to a backing material. Is then attached to the diaphragm. Deflection of the diaphragm causes corresponding strain in the wire gage. Causes a corresponding change in the resistance which is proportional to the pressure. BIME302 Lecture Note 1-2025

14. Fiber optic type pressure transducer Measures the displacement of the diaphragm optically by the varying reflection of light from the back of the deflecting diaphragm. Inherently safer electrically BIME302 Lecture Note 1-2025

15. Blood Pressure Waveforms BIME302 Lecture Note 1-2025

16. Testing technique for measuring the transient response of the catheter-sensor system BIME302 Lecture Note 1-2025

17. Transient response of the catheter-sensor system BIME302 Lecture Note 1-2025

18. For determining the function of Capillary bed Right side of the heart The central venous pressure is measured in the central vein or in the right atrium. It fluctuates above and below atmospheric pressure as the subject breathes. The reference level for venous pressure is at the right atrium. Central venous pressure is an important indicator of myocardial performance Venous pressure BIME302 Lecture Note 1-2025

19. Monitored for assessing proper therapy for heart dysfunction Shock Hypovolemic ( Of or relating to a decrease in the volume of circulating blood) or hypervolemic States Circulatory failure Central venous pressure BIME302 Lecture Note 1-2025

20. Continuous dynamic measurements is made by connecting a high sensitive pressure sensor to the venous catheter. Normal venous pressure values range widely from 0 to 1.2 kPa with a mean pressure of 0.5 kPa . Central venous pressure BIME302 Lecture Note 1-2025

21. Heart Sounds Heart sounds are vibrations or sounds due to the acceleration or deceleration of blood. Murmurs are vibrations or sounds due to blood turbulence. The technique of listening to sounds produced by the organs and vessels of the body is called auscultation. BIME302 Lecture Note 1-2025

22. Heart Sounds … BIME302 Lecture Note 1-2025

23. Heart Sounds … BIME302 Lecture Note 1-2025

24. Heart Sounds … With each heartbeat, the normal heart produces two distinct sounds that are audible in the stethoscope – often described as “ lub -dub ” The “ lub ” is caused by the closure of atrioventricular valves and is called the first heart sound occurs approximately at the time of QRS complex of the ECG and just before ventricular systole. The “dub” part of the heart sounds is called the second heart sound and is caused by the closing of the semilunar valves Which closes at the end of the systole, just before the atrioventricular valve opens. Occurs at the time of the end of the T wave of the ECG The third heart sound attributed to the sudden termination of the rapid filling phase of the ventricles from the atria and the associated vibration of the ventricular muscle walls., which are relaxed. BIME302 Lecture Note 1-2025

25. Auscultation Techniques There are optimal recording sites for the various heart sounds. BIME302 Lecture Note 1-2025

26. Auscultation Techniques… Heart sounds and murmurs have extremely small amplitudes with frequencies from 0.1 to 2000 Hz. Thus the recording device must be carefully selected for wide band frequency response characteristics. Specially designed acoustically quiet environment is needed for noise free recording of heart sounds. BIME302 Lecture Note 1-2025

27. Stethoscope Mechanical stethoscopes amplifies sound because of Standing wave phenomenon that occur at quarter-wavelengths of the sound. Uneven frequency response with many resonance peaks. Firm application of the chest piece makes the diaphragm taut with pressure thereby causing an attenuation of low frequencies. Loose-fitting earpiece cause leakage which reduces the coupling between the chest wall and the ear. Electronics stethoscopes has selectable frequency response characteristics ranging from “ideal” flat-response to selectable band-pass response. BIME302 Lecture Note 1-2025

28. Stethoscope Frequency response BIME302 Lecture Note 1-2025

29. Phonocardiogram A Phonocardiogram is a recording of the heart sounds and murmurs. Eliminates subjective interpretation of the heart sounds Enables evaluation of the heart sounds and murmurs with respect to the electric and mechanical events in the cardiac cycle. Evaluation of the result is based on the basis of changes in the wave shape and various timing parameters. BIME302 Lecture Note 1-2025

30. Phonocardiogram BIME302 Lecture Note 1-2025

31. Frequency spectrum of a typical Phonocardiogram BIME302 Lecture Note 1-2025

32. Cardiac Catheterization The process of introducing a catheter into the heart for diagnosis. Used to asses hemodynamic (circulation of the blood and the forces involved) function and cardiovascular structure. Performed during most of the heart surgeries. Performed in specialized laboratories outfitted with x-ray equipment for visualizing heart structures and the position of various pressure catheters. BIME302 Lecture Note 1-2025

33. Cardiac Catheterization … A radiopaque die is injected into the ventricles or aorta through the catheter for assessing the ventricular or aortic function Pressures in all four chambers of the heart and in the great vessels can be measured by positioning the catheters in such a way to recognize the characteristics pressure waveforms. BIME302 Lecture Note 1-2025

34. Cardiac Catheterization … BIME302 Lecture Note 1-2025

35. Angiography Roentgenographic examination of blood vessels after injection of a radiopaque contrast medium; Angiographic visualization is an essential tool used to evaluate cardiac structure. Specially designed catheters and power injectors are used in order that a bolus of contrast material can be delivered rapidly into the appropriate vessel or heart chamber. BIME302 Lecture Note 1-2025

36. Cardiac Catheterization & Angiogram BIME302 Lecture Note 1-2025

37. Angiogram BIME302 Lecture Note 1-2025

38. Angioplasty Surgical procedure to repair a damaged blood vessel or unblock a coronary artery BIME302 Lecture Note 1-2025

39. Indirect Blood Pressure Measurement - Sphygmomanometer BIME302 Lecture Note 1-2025

40. Indirect Blood Pressure Measurement - Sphygmomanometer BIME302 Lecture Note 1-2025

41. Indirect Blood Pressure Measurement - Sphygmomanometer BIME302 Lecture Note 1-2025

42. Indirect Blood Pressure Measurement - Sphygmomanometer The pressure cuff on the upper arm is first inflated to a pressure well above the systolic pressure. At this point no sound can be heard through the stethoscope, which is placed over the brachial artery, for that artery has been collapsed by the pressure of the cuff. The pressure in the cuff is then gradually reduced. BIME302 Lecture Note 1-2025

43. Sphygmomanometery… When the systolic peaks are higher than the occlusive pressure, the blood spurts under that cuff and causes a palpable pulse in the wrist (Riva- Rocci Method) Audible sounds ( Korotkoff (named after Dr. Nikolai Korotkoff ) sounds) generated by the flow of blood and vibrations of the vessel under the cuff are heard through the stethoscope. BIME302 Lecture Note 1-2025

44. Sphygmomanometery … The pressure of the cuff that is indicated on the manometer when the first Korotkoff sound is heard is recorded as the systolic blood pressure. As the pressure in the cuff is continues to drop, the Korotkoff sounds continue until the cuff pressure is no longer sufficient to occlude the vessel during any part of the cycle. Below this pressure the Korotkoff sounds disappear , marking the value of the diastolic pressure. BIME302 Lecture Note 1-2025

45. Sphygmomanometery … Auscultatory (based on the Korotkoff sounds) technique is simpler and requires a minimum of equipment. Cannot be used in noisy environments. Palpation (based on pulse on the blood vessel) technique doesn’t require a noise free environment. Normal respiration and vasomotor waves modulate the normal blood-pressure levels. BIME302 Lecture Note 1-2025

46. Automated Indirect Blood Pressure measurement techniques Involves an automatic sphygmomanometer that inflates and deflates an occlusive cuff at a predetermined rate. A sensitive detector is used to measure the distal pulse or cuff pressure. BIME302 Lecture Note 1-2025

47. Automated Auscultatory device Microphone replaces the stethoscope for sensing the Korotkoff sounds. The process begins with a rapid (20-30mm Hg/s) inflation of the occlusive cuff to a preset pressure about 30mm Hg higher tha n the suspected systolic pressure. The flow of blood beneath the cuff is stopped by the collapse of the vessel. BIME302 Lecture Note 1-2025

48. Automated Auscultatory device Cuff pressure is then reduced slowly (2-3 mm Hg/s). The first Korotkoff sound is detected by the microphone, at which time the level of the cuff pressure is stored. BIME302 Lecture Note 1-2025

49. Automated Auscultatory device The muffling and silent period of the Korotkoff sound is detected, and the value of the diastolic pressure is also stored. After a few minutes the instrument displays the systolic and diastolic pressure and recycles the operation BIME302 Lecture Note 1-2025

50. Ultrasonic Based Blood Pressure Measurement Employs a transcutaneous Doppler sensor that detects the motion of the blood-vessel walls in the various states of occlusion. The Doppler ultrasonic transducer is focused on the vessel wall and the blood. The reflected signal (shifted in frequency) is detected by the receiving crystal and decoded. BIME302 Lecture Note 1-2025

51. Ultrasonic Based Blood Pressure Measurement… BIME302 Lecture Note 1-2025

52. Ultrasonic Based Blood Pressure Measurement… The difference in frequency, in the range of 40 to 500 Hz, between the transmitted and received signals is proportional to the velocity of the wall motion and the blood velocity. As the cuff pressure is increased above diastolic but below systolic, the vessels opens and closes with each heartbeat, because the pressure in the artery oscillates above and below the applied external pressure in the cuff. BIME302 Lecture Note 1-2025

53. Ultrasonic Based Blood Pressure Measurement… BIME302 Lecture Note 1-2025

54. Ultrasonic Based Blood Pressure Measurement… As the applied pressure is further increased, the time between the opening and closing decreases until they coincide. The reading at this point is the systolic pressure. When the pressure is cuff is reduced, the time between the opening and closing increases until the closing signal from one pulse coincides with opening signal from the next. The reading at this point is the diastolic pressure. BIME302 Lecture Note 1-2025

55. Ultrasonic Based Blood Pressure Measurement… Advantages: Doesn’t require a noise free environment. Disadvantage: Movement of the subject‘s body cause changes in ultrasonic path between the sensor and the blood vessel. BIME302 Lecture Note 1-2025

56. END OF LECTURE NOTE 1 Thank you for your attention Your Questions? BIME302 Lecture Note 1-2025