6生物醫(yī)學(xué)測量與儀器第四章1

1、Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University2014.4School of Life Science and TechnologyXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityCh 4 Physiological Measurement and Device4.1 Blood pressure measu

2、rement and device4.2 Blood flow measurement and device4.3 Temperature measurement and deviceXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversitynManometer 壓力計壓力計nSphygmomanometer 血壓計血壓計nSphygmometer 血壓計血壓計nBlood pressure meter血壓計血壓計nAuscultatory method 聽診法

3、聽診法 （柯氏音法）（柯氏音法）nOscillometric method 示波法示波法nSystolic 收縮的收縮的nDiastolic 舒張的舒張的nTonometry 張力測量法張力測量法nLaminar flow 層流層流nTurbulent flow 湍流湍流nHypertension 高血壓高血壓nHypotension 低血壓低血壓Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityHistory 1733 Stephen Hales gl

4、ass tube 1828 Poiseuill mercury manometer 1856 Faivre artery pressure 1896 Riva-Rocci mercury cuff manometer 1905 N.S.Korotkoff Auscultatory Method 1970 Oscillometric Method4.1 Blood Pressure Measurement and DeviceXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong

5、UniversityHistory of Sphygmomanometer (sphygmometer, blood pressure meter)l1733 Stephen Hales manometera hollow pipe connected to a 12-foot glass tube into an artery in the neck of a horse; the blood rose 9 feet into the glass tube, indicating the blood pressure Xian Jiaotong UniversityXian Jiaotong

6、 UniversityXian Jiaotong UniversityXian Jiaotong UniversityHistory of Sphygmomanometer (sphygmometer,blood pressure meter)l1828 Poiseuill: mercury manometerl1856 Faivre: artery pressurel1896 Riva-Rocci & Leonard Hill: introduced a cuff Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaoton

7、g UniversityXian Jiaotong Universityl1905 N.S.Korotkoff l1970 Yon RecklinghausenXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian

8、 Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityCommonly refers to arterial blood pressureBlood Pressure: Originates from the heartXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityValue depends on 3 factors:cardiac outputdiameter of

9、arteriesthe quantity of bloodPeripheral resistancedynamic tracking of pathology and physiology affecting to the cardiovascular systemBlood Pressure: systolic pressure (SP) / diastolic pressure (DP)Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityPulse p

10、ressure (PP) = SP-DPMean pressure (MP)average pressure during one cardiac cycledriving force of the peripheral perfusion.an estimate can be done by using an empiricalMP = DP+PP/3SP and DP may vary significantly throughout the arterial system but MP is quite uniform (in normal situations)Heart contra

11、ctionXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University1. Auscultatory Method2. Ultrasonic Method3. Oscillometric Method4. TonometryNon-Invasive Methodsin Blo

12、od Pressure MeasurementsXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityLaminar and Turbulent FlownLaminar flowqStreamlinedqOutermost layer moving slowest and center moving fastestnTurbulent flowqInterruptedqRate of flow exceeds critical velocityqFluid

13、 passes a constriction, sharp turn, rough surfaceXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong Universitycommon measurement site: brachial artery The most common indirect methods are auscultation and oscillometryIndirect measurement = non-invasive measurementB

14、ranchia 肱的； Radial 橈骨的；Ulnar 尺骨的；Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityAuscultatory MethodXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityAuscultatory MethodThere are 5 distinct phases in the Ko

15、rotkoff sounds, which define SP and DP The frequency range is 20-300 Hz and the accuracy is: +/- 2mmHg (SP) and +/- 4mmHg (DP)Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityAuscultatory Method -) The observations differ from observer to another-) A me

16、chanical error e.g. mercury leakage, air leakage,etc.-) Do not always correspond with intra-arterial pressure-) Can not be used in noisy environment+) Simple and does not require much equipmentADVANTAGESDISADVANTAGES-) Not accurate for infants and hypotensive patientsXian Jiaotong UniversityXian Jia

17、otong UniversityXian Jiaotong UniversityXian Jiaotong UniversityUltrasonic MethodA transcutaneous (through the skin) Doppler sensor is applied.The frequency difference between transmitted (8 MHz) and received signal is 40-500 Hz and it is proportional to velocities of the wall motion and the blood.T

18、he vessel opens and closes with each heartbeat when DP P SPcuffXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityUltrasonic Method +) Can be also used in noisy environment ADVANTAGES & DISADVANTAGES+) Can be used with infants and hypotensive individu

19、als-) Subjects movements change the path from sensor to vesselAs the cuff pressure is increased, the time between opening and closing decreases until they coincide As the cuff pressure is decreased, the time between opening and closing increases until they coincide Systolic pressureDiastolic pressur

20、eXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University Measures the amplitude of oscillations that appear in the cuff pressure signal which are created by expansion of the arterial wall each time blood is forced through the artery. Oscillometric MethodUniqu

21、enessSpecific characteristics of the compression cuffs entrained air volume are used to identify and sense blood-pressure value.Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityOscillometric MethodXian Jiaotong UniversityXian Jiaotong UniversityXian Jia

22、otong UniversityXian Jiaotong University Process: A compression cuff is inflated above systolic pressure and slowly deflated. Systolic pressure is detected where there is a transition from small amplitude oscillations (above systolic pressure) to increasing cuff-pressure amplitude. The cuff-pressure

23、 oscillations increase to a maximum at the mean arterial pressure.Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityOscillometric MethodThe cuff pressure is deflated either linearly or stepwiseThe arterial pressure oscillations are superimposed on the cu

24、ff pressureXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityAs/Am=C1; Ad/Am=C2Oscillometric MethodXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityOscillometric Method DISADVANTAGE-) Many devices use fixed

25、algorithms leading to large variance in blood pressuresADVANTAGES+) MP can be measured reliably even in the case of hypotensionXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityContinuous noninvasive arterial pressure Current technologies 1. Vascular unl

26、oadingPrinciple to unload the arterial wall in order to linearize this phenomenon with a counter pressure as high as the pressure inside the artery. Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University Principle: when a pressurized vessel is partly collaps

27、ed by an external object, the circumferential (圓周) stresses in the vessel wall are removed and the internal and external pressures are equal.2. TonometryXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University3. Pulse transit timePrinciple: When the heart ejec

28、ts stroke volume to the arteries, it takes a certain transit time until the blood volume arrives in the periphery. The pulse transit time (PTT) indirectly depends on blood pressure The pitfall of all noninvasive technologies ischange in vascular toneXian Jiaotong UniversityXian Jiaotong UniversityXi

29、an Jiaotong UniversityXian Jiaotong UniversityDirect Methodsin Blood Pressure Measurements1. Extravascular Sensor2. Intravascular SensorXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityGeneral FactsDirect measurement = Invasive measurementUsed only when

30、 essential to determine the blood pressure continuously and accurately in dynamic circumstancesA vessel is punctured and a catheter is guided in. A division is made into extravascular and intravascular sensor systemsXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaoton

31、g UniversityExtravascular SensorThe sensor is located behind the catheter and the vascular pressure is transmitted via this liquid-filled catheter.Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDynamic Properties 振動膜振動膜Xian Jiaotong UniversityXian Jia

32、otong UniversityXian Jiaotong UniversityXian Jiaotong UniversityL: catheter length; r: radius;:liquid viscosity (粘性);:liquid density:volume modulus of elasticity (彈性模量)P: pressure difference across the segment; Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong Uni

33、versityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityTypical Pressure-waveform DistortionXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong Uni

34、versityXian Jiaotong UniversityWith a bubbleXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityA 5 mm-long air bubble has formed in the rigid-walled catheter connected to a Statham P23Dd sensor. The catheter is 1 m long, 6 French diameter, and filled with

35、 water at 20 8C. (The isothermal compression of air DV=DP is 1 ml/cm of water pressure per liter of volume.) Plot the frequency-response curve of the system with and without the bubble. (Internal radius of the catheter is 0.46 mm; volume modulus of elasticity of the diaphragm is 0:49 1015 N/m5.)Xian

36、 Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDistortion during the recording of arterial pressureXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityThe hydraulic （液壓） link is the major source of errors. The s

37、ystems natural frequency may be damped and degraded due to:too narrow cathetertoo long tubingvarious narrow connectionsair bubbles in the catheterXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityGeneral on System ParametersEven minute air bubbles in cat

38、heter have a dramatic effect on frequency responseThe natural frequency and the length of the catheter have a following relationship:The catheter diameter has a linear relationship to natural frequencyStiffer catheters have a higher frequency response TeflonPolyethyleneSilicon rubberBETTERWORSEXian

39、Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityPressure causes deflection in a thin metal membrane that modulates the coupling between the source and detector fibers.Intravascular Sensor The sensor is located in the tip of the catheter.Xian Jiaotong Univer

40、sityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityCharacteristic curve for the fiber-optic pressure sensorXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityIntravascular Sensor +) The frequency response is not limited by the hyd

41、raulic properties of the system. No time delay.-) Breaks easily-) More expensive+) Electrical safety and isolation when using fiber opticsADVANTAGESDISADVANTAGESXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversitySummaryBLOOD PRESSURE Describes the physiol

42、ogy and pathology of cardiocvascular systemAll direct methods require skin punctuation and a use of catheter. Methods are used only when continuous and accurate measurements are needed.Extravascular Sensor; Intravascular SensorAlmost all indirect methods rely on an occlusive cuff which is placed on

43、the bracial artery. The actual measurement is done when the cuff is deflated.Auscultatory Method; Ultrasonic MethodOscillometric Method; TonometryXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong University4.2 Blood flow measurement and deviceaphyXian Jiaotong Uni

44、versityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityIndirect Methodsin Blood Flow MeasurementsXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityBlood FlowO and other nutrition concentration in the cells are one of the primary m

45、easurements. 2Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body.It also helps to understand many pathological conditions,since many diseases alter the blood flow. Also the blood clots in the arterial system can be detected.? ? ?&Xia

46、n Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityBlood Flow Normal blood flow velocity 0,5 m/s 1 m/s (Systolic, large vessel)Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDoppler Measurements-Ultrasound Dop

47、plerTransducer: Piazoeletric material eletric acousticNear and far fields for various transducer diameters and frequencies.Beams are drawn to scale, passing through a 10 mm-diameter vessel.Transducer diameters are 5, 2, and 1 mm. Solid lines are for 1.5 MHz, dashed lines for 7.5 MHz.D-transducer dia

48、meter -wavelength.Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong Universityemits a fixed-areapulse each time the audio signal crosses the zero axisproduce an output proportional to the velocity of the blood cellsfrequency-to-voltage converterf = 2 10 MHzcc = 15

49、00 - 1600 m/s (1540 m/s)f = 1,3 13 kHzdu=1.5m/sXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversitynReceived Signal: A large-amplitude signal at the carrier frequency plus the very low (approximately 0.1%) amplitude Doppler-shifted signal (not at a single

50、frequency) RF amplifierlow-amplitude Doppler-frequency componentscarrierGainBandwidthsmuch wider than requiredDetector can be a simple square-law device such as a diode.it cannot detect the direction of flow.Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong Univer

51、sityDirectional Doppler block diagramp351,352Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDirectional Doppler signal waveformsXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityThe transmitter is excited

52、with a brief burst of signal. Pulsed DopplerThe delay between transmission and reception is a direct indication of distance. Doppler shift at various delays a velocity profile (分布圖） across the vesselThe usual compromise is an 8 MHz pulse of 1 us duration,which produces a traveling packet 1.5 mm long

53、Xian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDoppler Measurements (2) Ultrasound DopplerThe flow velocity is obtained from the spectral estimation of the received Doppler signalIn order to know where along the beam the blood flow data is collected,

54、a pulsed Doppler must be usedXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityDoppler Measurements GENERAL PARAMETERSthe power decays exponentially because of the heating of the tissue. The absorption coefficient proportional to frequencythe far field o

55、peration should be avoided due to beam divergence.D = Transducer diameter (e.g. 1 5 mm) the backscattered power is proportional to f4the resolution and SNR are related to the pulse duration. Improving either one of the parameters always affects inversely to the other Xian Jiaotong UniversityXian Jia

56、otong UniversityXian Jiaotong UniversityXian Jiaotong UniversityLaser Doppler FlowmetryThe laser parameter may have the following properties: 5 mW He-Ne-laser 632,8 nm wavelengthThe method is used for capillary (microvascular) blood flow measurementsXian Jiaotong UniversityXian Jiaotong UniversityXi

57、an Jiaotong UniversityXian Jiaotong UniversityPlethysmographyin Blood Flow MeasurementsXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityPlethysmography -Strain Gage MethodPlethysmography : record volume changes of an organ or a body part (e.g. a leg)Str

58、ain gage is made of silicone rubber tubes, which are filled with conductive liquid (e.g. mercury) whose impedance changes with volume.Venous occlusion cuff is inflated to 40 50 mmHg. By timing these volume changes, F=dV/dtXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityXian J

59、iaotong UniversityPlethysmography-Chamber MethodThe venous-occlusion cuff is inflated to stop venous return. Arterial flow causes an increase in volume of the leg segment, which the chamber measures.The chamber has a rigid cylindrical outer container and is placed around the leg.Xian Jiaotong Univer

60、sityXian Jiaotong UniversityXian Jiaotong UniversityXian Jiaotong UniversityAfter venous-occlusion cuff pressure is turned on, the initial volume-versus-time slope is caused by arterial inflow. After the cuff is released, segment volume rapidly returns to normal (A). If a venous thrombosis blocks the vein, ret