blood pressure.pptx invasive blood pressure

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1. PHYSICAL PRINCIPLES A wave is a disturbance that travels through a medium, transferring energy but not matter. One of the simplest waveforms is the sine wave 01-05-2024 1 Dr. Vikram Naidu

2. Fourier Analysis The arterial waveform is clearly not a simple sine wave, but it can be broken down into a series of many component sine waves The process of analysing a complex waveform in terms of its constituent sine waves is called Fourier Analysis . 01-05-2024 2 Dr. Vikram Naidu

3. Properties Natural frequency Damping coefficient 01-05-2024 3 Dr. Vikram Naidu

4. The natural frequency of a system determines how rapidly the system oscillates after a stimulus T he damping coefficient reflects frictional forces acting on the system and determines how rapidly it returns to rest after a stimulus 01-05-2024 4 Dr. Vikram Naidu

5. Natural Frequency It is important that the IBP system has a very high natural frequency – at least eight times the fundamental frequency of the arterial waveform (the pulse rate ). Therefore , for a system to remain accurate at heart rates of up to 180bpm, its natural frequency must be at least: (180bpm x 8) / 60secs = 24Hz. 01-05-2024 5 Dr. Vikram Naidu

6. Natural Frequency The natural frequency of a system may be increased by : Reducing the length of the cannula or tubing Reducing the compliance of the cannula or diaphragm Reducing the density of the fluid used in the tubing Increasing the diameter of the cannula or tubing Commercially available systems -200Hz 01-05-2024 6 Dr. Vikram Naidu

7. Damping Anything that reduces energy in an oscillating system will reduce the amplitude of the oscillations. This is termed damping. Some degree of damping is required in all systems ( critical damping ), but if excessive ( overdamping ) or insufficient ( underdamping ) the output will be adversely effected . 01-05-2024 7 Dr. Vikram Naidu

8. Underdamped arterial pressure waveform Overdamped arterial pressure waveform 01-05-2024 8 Dr. Vikram Naidu

9. Factors that cause overdamping include : Friction in the fluid pathway Three way taps Bubbles and clots Vasospasm Narrow, long or compliant tubing Kinks in the cannula or tubing 01-05-2024 9 Dr. Vikram Naidu

10. FAST-FLUSH TEST Provides a convenient bedside method for determining dynamic response of the system Natural frequency is inversely proportional to the time between adjacent oscillation peaks The damping coefficient can be calculated mathematically, but it is usually determined graphically from the amplitude ratio 01-05-2024 10 Dr. Vikram Naidu

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12. COMPONENTS OF AN IBP MEASURING SYSTEM 01-05-2024 12 Dr. Vikram Naidu

13. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula 01-05-2024 13 Dr. Vikram Naidu

14. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing 01-05-2024 14 Dr. Vikram Naidu

15. COMPONENTS OF AN IABP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer 01-05-2024 15 Dr. Vikram Naidu

16. COMPONENTS OF AN IBP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer Infusion/flushing system 01-05-2024 16 Dr. Vikram Naidu

17. COMPONENTS OF AN IBP MEASURING SYSTEM Intra-arterial cannula Fluid filled tubing Transducer Infusion/flushing system Signal processor, amplifier and display 01-05-2024 17 Dr. Vikram Naidu

18. Levelling and zeroing Zeroing : For a pressure transducer to read accurately, atmospheric pressure must be discounted from the pressure measurement. This is done by exposing the transducer to atmospheric pressure and calibrating the pressure reading to zero. T he level of the transducer is not important . 01-05-2024 18 Dr. Vikram Naidu

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20. Levelling : The pressure transducer must be set at the appropriate level in relation to the patient in order to measure blood pressure correctly. This is usually taken to be level with the patient’s heart, at the 4th intercostal space, in the mid-axillary line . A transducer too low over reads, a transducer too high under reads. 01-05-2024 20 Dr. Vikram Naidu

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22. Normal Arterial Pressure Waveforms The systolic waveform components consist of a steep pressure upstroke, peak, and ensuing decline, and immediately follow the ECG R wave. The downslope of the arterial pressure waveform is interrupted by the dicrotic notch , continues its decline during diastole after the ECG T wave, and reaches its nadir at end-diastole 01-05-2024 22 Dr. Vikram Naidu

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24. As the pressure wave travels from the central aorta to the periphery , the arterial upstroke becomes steeper, the systolic peak increases, the dicrotic notch appears later, the diastolic wave becomes more prominent, and end-diastolic pressure decreases . 01-05-2024 24 Dr. Vikram Naidu

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26. Arterial Blood Pressure Gradients The nature of the operative procedure is important when choosing the appropriate site Ex: Coarctation of aorta Thoracic and abdominal aortic surgeries Cardiopulmonary bypass 01-05-2024 26 Dr. Vikram Naidu

27. Cardiopulmonary bypass : The mean radial artery pressure decreases on initiation of bypass and remains less than mean femoral artery pressure throughout the bypass period. P ersists in the first few minutes following separation from bypass , often by more than 20 mm Hg. 01-05-2024 27 Dr. Vikram Naidu

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29. Abnormal Arterial Pressure Waveforms Morphologic features of individual arterial pressure waveforms can provide important diagnostic information 01-05-2024 29 Dr. Vikram Naidu

30. 01-05-2024 30 Condition Characteristics Aortic stenosis Pulsus parvus (narrow pulse pressure) Pulsus tardus (delayed upstroke) Aortic regurgitation Bisferiens pulse (double peak) Wide pulse pressure Hypertrophic cardiomyopathy Spike and dome (mid-systolic obstruction) Systolic left ventricular failure Pulsus alternans (alternating pulse pressure amplitude) Cardiac tamponade Pulsus paradoxus (exaggerated decrease in systolic blood pressure during spontaneous inspiration) Dr. Vikram Naidu

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32. Waveform analysis for prediction of intravascular volume responsiveness Variations in arterial blood pressure observed during positive pressure ventilation, as well as a variety of derived indices, are the most widely studied of these dynamic indicators . They result from changes in intrathoracic pressure and lung volume that occur during the respiratory cycle. 01-05-2024 32 Dr. Vikram Naidu

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34. REFERENCES Miller's 8th edition Physical principles of intra-arterial blood pressure measurement anaesthesia Kaplan's cardiac anesthesia the echo era 6edition 01-05-2024 34 Dr. Vikram Naidu

35. Thank you