Chapter 5 Part Two

1. Chapter 5Part Two Blood Pressure and flow by IbrhimAlMohimeed BMTS 353

2. Blood Pressure • Originates from the left ventricle of the heart. • One of the oldest physiological measurements. • Observation of blood pressure allows dynamic tracking of pathology and physiology affecting to the cardiovascular system. BMTS 353

3. Blood Pressure Reading • Systolic: the top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts). • Diastolic: the bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the left ventricle muscle is resting between beats and refilling with blood). BMTS 353

4. Blood Pressure Reading BMTS 353

5. Blood Pressure Reading • Mean arterial pressure (MAP) is a term used in medicine to describe an average blood pressure in an individual. • It is defined as the average arterial pressure during a single cardiac cycle and given by: BMTS 353

6. Blood Pressure Risks • High blood pressure (hypertension) increases the risk of: • Chest pain (angina). • Heart attack. • Heart failure. • Kidney failure. • Stroke. • Blocked arteries in the legs or arms (peripheral arterial disease. • Eye damage . • Aneurysms (permanent cardiac or arterial dilatation). BMTS 353

7. Cont. Blood Pressure Risks BMTS 353

8. Cont. Blood Pressure Risks • Low blood pressure (hypotension) increases the risk of: • Reduces the blood flow to the brain and other vital organs. • Dizziness or fainting. • Lack of concentration. • Blurred vision. • Fatigue. • Cold and clammy skin. • Rapid shallow breathing. BMTS 353

9. Blood Pressure Value Generally, the blood pressure value depends on two main factors: Cardiac output (Blood Volume): The more blood present in the body, the higher the rate of blood return to the heart and the resulting cardiac output, potentially resulting in higher arterial pressure. BMTS 353

10. Cont. Blood Pressure Value • Resestance of blood flow: The higher the resistance, the higher the arterial pressure. Resistance is related to vessel radius, blood viscosity, and the smoothness of the blood vessel walls. BMTS 353

11. Invasive & Non-invasive • In general, there are two main categories which describe the invasiveness of a medical measurement: • Invasive:requiring the entry of a needle, catheter, or other instrument into a part of the body. • Non-invasive:not requiring entering or penetrating the body or disturbing body tissue. BMTS 353

12. Blood Pressure Measurement Blood Pressure Palpatory Method (Riva-Rocci Method) Auscultatory Method Non-Invasive Oscillometric Method Automatic Method Ultrasonic Method Extravascular Sensor Invasive Intravascular Sensor BMTS 353

13. Blood Pressure Measurement Blood Pressure 1 Non-invasive (Indirect) Method of Blood Measurement BMTS 353

14. Measurement Site Blood Pressure • Brachial artery is the most common measurement site: • Close to heart • Convenient for measuring • Other sites are radial artery and wrist. BMTS 353

15. Palpatory Method Blood Pressure • aka Riva-Rocci Method. When the cuff pressure is higher than SBP, artery is closed, no pulse can be sensed. When the cuff pressure drops below SBP, blood can pass through the artery and the pulse will be felt. BMTS 353

16. Cont. PalpatoryMethod Blood Pressure The pulse will continue to be felt as the pressure in the cuff falls down to zero. The pressure indicated on the gauge when the pulse reappears is noted. This is the systolic pressure. BMTS 353

17. Cont. PalpatoryMethod • The blood pressure can be measured in noisy environment. • It is a simple technique. • Only the systolic blood pressure (SBP) can be measured (not DBP). • The technique does not give accurate results for infants and hypotensive patients. Blood Pressure BMTS 353

18. Auscultatory Method Blood Pressure • Auscultation: the act of listening, either directly or through a stethoscope or other instrument, to sounds within the body. • This method is based on the fact that pulse waves when first propagate through the brachial artery, generate Korotkoff sounds. • Video BMTS 353

19. Korotkoffsounds • If a stethoscope is placed over the brachial artery in a normal person (without arterial disease), no sound should be audible. • As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries, and no sound is produced. • Similarly, if the cuff of a sphygmomanometer is placed around a patient's upper arm and inflated to a pressure above the patient's systolic blood pressure, there will be no sound audible because the pressure in the cuff is high enough such that it completely blocks the blood flow. Blood Pressure BMTS 353

20. Cont. Korotkoffsounds • If the pressure is dropped to a level equal to that of the patient's systolic blood pressure, the first Korotkoff sound will be heard. • As the pressure in the artery rises above the pressure in the cuff and then drops back down (because of beating), resulting in turbulence that produces an audible sound. • As the pressure in the cuff is allowed to fall further, thumping sounds continue to be heard as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and dropping back below the pressure in the cuff. Blood Pressure BMTS 353

21. Cont. Korotkoffsounds • Eventually, as the pressure in the cuff drops further, the sounds change in quality, then become muted, and finally disappear altogether. • This occurs because, as the pressure in the cuff drops below the diastolic blood pressure, the cuff no longer provides any restriction to blood flow allowing the blood flow to become smooth again with no turbulence and thus produce no further audible sound. Blood Pressure BMTS 353

22. AuscultatoryMethod Procedure Blood Pressure BMTS 353

23. AuscultatoryMethod Procedure Blood Pressure The cuff pressure is inflated quickly to a pressure higher than the systolic pressure. Then the air is let out of the cuff at a small rate. When the cuff pressure equal to that of the patient's systolic blood, a korotkoff sound will be heard with each heartbeat. This point marks the systolic pressure. BMTS 353

24. AuscultatoryMethod Procedure Blood Pressure As the pressure is lowered further, the character of the Korotkoff sounds change. At some point, the sounds will disappear. The pressure reading at this point gives the diastolic pressure. BMTS 353

25. Using Auscultatory Method Blood Pressure • Auscultatory technique is considerd simple. • It may be difficult to be done in a noisy environment. • The effect of human error is large. • It could be difficult to be used with infant. BMTS 353

26. Oscillometric Method • the observation of oscillations of blood flow during the pulsation. • It uses a sphygmomanometer cuff, like the auscultatory method, but with pressure sensor (transducer) to observe cuff pressure oscillations • The pressure sensor (within the inflated cuff) detects the pulsation of the artery wall as a pressure vibration. The interpretation of these small vibrations amplitude provide the blood pressure value. Blood Pressure BMTS 353

27. Cont. OscillometricMethod Blood Pressure BMTS 353

28. Cont. OscillometricMethod Blood Pressure • In the recent years, oscillometric methods have become popular for their simplicity of use and reliability. • It can be used with case of hypotension and infant. • It use algorithms that may leads to large variance in blood pressures measurement. • Motion artifact is considered a major drawback of this method. BMTS 353

29. Automatic Method • Many limitations of manual intermittent blood pressure measurement have been overcome by automated non-invasive blood pressure (NIBP) devices. • There are now used widely in medical care. • NIBP devices provide consistent, reliable values for systolic, diastolic, and mean arterial pressure (MAP). • Automated NIBP devices provide alarm systems to draw attention to extreme blood pressure value. Blood Pressure BMTS 353

30. Cont. Automatic Method • The greatest advantage of automated NIBP devices compared with manual methods of blood pressure measurement is that they don’t require an operator to perform the measurement. • It can easily provide a repetitive blood pressure measurements. • Most automated NIBP devices are based on the oscillometry method. Blood Pressure BMTS 353

31. The Device Diagram Blood Pressure Micro- processor Display Pressure sensor Air pump Bleed valve BMTS 353

32. Automatic Method Errors • Sources of error for the automatic method: • Cuff size: Oscillations are direct result of BP cuff application - Cuff too small = overestimation of BP - Cuff too large = underestimation of BP • Cuff position:Bladder needs to be placed over brachial artery. Blood Pressure BMTS 353

33. Cont. Automatic Method Errors • Movement: Blood Pressure BMTS 353

34. Cont. Automatic Method Errors • Beat to beat variation: Oscillometric method requires reasonably stable BP during cuff deflation. If BP varies due to arrhythmia, difficult to estimate BP accurately. Blood Pressure BMTS 353

35. Ultrasonic Method Blood Pressure • The ultrasonic Doppler technique is applied by this method. • The motion of blood-vessel walls of occlusion (opining and closing) is measured by Doppler technique. • The vessel opens and closes with each heartbeat when • DP < Pcuff< SP BMTS 353

36. Doppler Effect Blood Pressure • It is the change in frequency of the returned sound wave (echo) from a moving object. BMTS 353

37. Cont. Doppler Effect Blood Pressure • Video BMTS 353

38. Principle of Ultrasonic Method Blood Pressure BMTS 353

39. Cont. Ultrasonic Method Blood Pressure • Can be also used in noisy environment. • The device is considiered contatin compicated part. • Highly affect by motion. BMTS 353

40. Blood Pressure Measurement Blood Pressure 2 Invasive (direct) Method of Blood Measurement BMTS 353

41. The first invasive blood pressure measurement Blood Pressure • The first invasive attempt to measure blood pressure was made by Stephen Hales in 1733. • He inserted tubes directly into the arteries of animals. BMTS 353

42. Invasive Method Blood Pressure • This technique involves direct measurement of arterial pressure by inserting a catheter (thin, hollow, and flexible tube). • Invasive (intra-arterial) blood pressure (IBP) monitoring is a commonly used technique in the Intensive Care Unit (ICU) and in the operating theatre. BMTS 353

43. Con.t Invasive Method Blood Pressure • IBP technique also allows accurate blood pressure readings specially the very low pressures, for example in shocked patients. • it allows continuous ‘beat-to-beat’ blood pressure monitoring. • It complex procedure involving many risks. BMTS 353

44. Invasive Method Types Blood Pressure • Generally, the Invasive technique can be divided into two division: • Extravascular Sensor System • Intravascular Sensor System BMTS 353

45. Extravascular Sensor System Blood Pressure • The sensor is located behind the catheter and the vascular pressure is transmitted by hydraulic connection. BMTS 353

46. Cont. Extravascular Sensor System Blood Pressure • The actual pressure sensor can be: • strain gage • variable inductance • variable capacitance • optoelectronic • piezoelectric • etc… BMTS 353

47. Intravascular Sensor System Blood Pressure • The sensor is located in the tip of the catheter (inside the body). • The sensor connected by an electrical or optical connection. • The frequency response is not limited by the hydraulic properties of the system. No time delay. • Breaks easily. • More expensive. BMTS 353

48. End of the Chapter BMTS 353