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BME 311: BIOMEDICAL INSTRUMENTATION I Lecturer: Ali Işın

FACULTY OF ENGINEERING DEPARTMENT OF BIOMEDICAL ENGINEERING. BME 311: BIOMEDICAL INSTRUMENTATION I Lecturer: Ali Işın. Lecture Note 3: Blood Pressure Measurement. An Individuals blood pressure is a standard clinical measurement

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BME 311: BIOMEDICAL INSTRUMENTATION I Lecturer: Ali Işın

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  1. FACULTY OF ENGINEERING DEPARTMENT OF BIOMEDICAL ENGINEERING BME 311: BIOMEDICAL INSTRUMENTATION ILecturer: Ali Işın Lecture Note 3: Blood Pressure Measurement BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  2. 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. Blood Pressure BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  3. Blood Pressure inside the heart chambers BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  4. Major Arteries & Veins of the Body BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  5. Cardiovascular system-typical values BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  6. 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. Blood Pressure Measurement BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  7. Direct Measurement(Extravascular) BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  8. Disposable blood-pressure sensor with integral flush device BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  9. 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. Direct MeasurementExtra Vascular BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  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 MeasurementExtra Vascular contd… BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  11. Direct MeasurementExtra Vascular contd… • 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. BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  12. Direct MeasurementIntravascular • 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. BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  13. 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. Bonded Strain Gage pressure transducer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  14. Measures the displacement of the diaphragm optically by the varying reflection of light from the back of the deflecting diaphragm. • Inherently safer electrically Fiber optic type pressure transducer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  15. Blood Pressure Waveforms BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  16. Harmonic Analysis of Blood Pressure Waveforms BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  17. Using Fourier Analysis techniques in the quantification of pressure and flow. • Blood pressure pulse can be divided into its fundamental component (of the same frequency as the blood pressure wave) and its significant harmonics. • Analysis of the frequency components of the pulse yield more information on arterial properties. Harmonic Analysis of Blood Pressure Waveforms BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  18. Electrical Model of Catheter-Sensor system BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  19. Testing technique for measuring the transient response of the catheter-sensor system BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  20. Transient response of the catheter-sensor system BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  21. Pressure-waveform distortion BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  22. Distortion during the recording of arterial pressure BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  23. 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 BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  24. 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 BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  25. 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 BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  26. 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. Heart Sounds BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  27. Heart Sounds … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  28. Heart Sounds … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  29. 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. Heart Sounds … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  30. There are optimal recording sites for the various heart sounds. Auscultation Techniques BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  31. 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. Auscultation Techniques… BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  32. 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. Stethoscope BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  33. Stethoscope Frequency response BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  34. 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. Phonocardiogram BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  35. Phonocardiogram BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  36. Frequency spectrum of a typical Phonocardiogram BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  37. 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. Cardiac Catheterization BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  38. 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. Cardiac Catheterization … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  39. Cardiac Catheterization … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  40. 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. Angiography BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  41. Cardiac Catheterization & Angiogram BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  42. Angiogram BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  43. Surgical procedure to repair a damaged blood vessel or unblock a coronary artery Angioplasty BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  44. Indirect Blood Pressure Measurement - Sphygmomanometer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  45. Indirect Blood Pressure Measurement - Sphygmomanometer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  46. Indirect Blood Pressure Measurement - Sphygmomanometer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  47. 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. Indirect Blood Pressure Measurement - Sphygmomanometer BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  48. 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. Sphygmomanometery… BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  49. 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. Sphygmomanometery … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

  50. 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. Sphygmomanometery … BME 311 LECTURE NOTE 3 - ALİ IŞIN, 2014

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