NON ELECTRICAL PHYSIOLOGICAL PARAMETER MEASUREMENT

NON ELECTRICAL PHYSIOLOGICAL PARAMETER MEASUREMENT

1. UNIT IV NON ELECTRICAL PHYSIOLOGICAL PARAMETER MEASUREMENT D.Jeraldin Auxillia

2. 9 Temperature, respiration rate and pulse rate measurements, Pulse oximetry, Blood Pressure: direct methods - - systolic, diastolic, mean detector circuit, indirect methods - auscultatory method, oscillometric method, ultrasonic method. Blood flow - Electromagnetic and ultrasound blood flow measurement. Cardiac output measurement- Indicator dilution, dye dilution and thermo dilution method

3. Respiratory system exchange of gases in any biological process is termed respiration - transporting oxygen to the cells, removing the carbon dioxide from the cells through lungs is known as pulmonary function. Re spiration measurement 1. measure the mechanics of breathing and the physical characteristics of the lungs(pulmonary test) 2. diffusion of gases in the lungs, the distribution of oxygen, and the collection of carbon dioxide.

4. Lung Volumes and Capacities -pulmonary tests are for the determination of lung volumes and capacities

5. Tidal volume TV The volume of air inhaled & exhaled at each breath during normal quiet breathing Inspiratory reserve volume IRV The volume of air that can be forcefully inspired following a normal quiet inspiration Expiratory reserve volume ERV The volume of air that can be forcefully expired after a normal or resting expiration Vital capacity VC The maximum amount of air that can be exhaled after the fullest inspiration possible (TV + ERV + IRV) Inspiratory capacity IC The maximum amount of air that can be inhaled after a normal exhalation (TV + IRV) Residual volume RV The volume of air remaining in the lungs after a forceful expiration Total lung capacity TLC The total volume of the lungs (VC + RV) TLC=IRV+ERV+RV Functional residual capacity FRC The amount of air remaining in the lungs after a normal quiet expiration (ERV + RV) Static lung volume and capacities

6. Apparatus used to measure static & dynamic lung volumes/capacities using a closed system Registers the amount and rate of air moved into or out of the lungs Measure 1. Volume: records the amount of air exhaled or inhaled within a certain time 2. Flow: measures how fast the air flows in or out as the volume of air inhaled or exhaled increases Types 1. water 2.Dry 3.Wedge Spirometer

7. Water spirometer

8. -consists of movable bell inverted over a chamber of wate r. Inside the bell, above the water line, is the breathed gas - height above the water is proportional to the amount of gas in the bell -A breathing tube connects the mouth of the patient with the gas under the bell - as the patient breathes into the tube , the bell moves up and do wn with each inspiration and expiration in proportion to the amount of air breathed in or out A pen attached to the bell writes on the adjacent drum recorder(kymograph) As the kymograph rotates, the pen traces the breathing pattern of the patient. -Bell volume-9 and 13.5 liters Paper speed (32,160,300,1920mm/min)

9. Wedge spirometer

10. The breathed air is held in a chamber enclosed by two parallel metal pans hinged to each other along one edge . One of the pans contains an inlet tube is fixed to a stand and the other swings freely with respect to it. The space between the two pans is enclosed by a flexible bellows ( Uke a fireplace bellows) to form the chamber. - As air is introduced into the chamber or withdrawn from it, the moving pan changes its position to compensate for the volume changes. - movement of pan is propositional to change in volume A well-designed wedge spirometer imposes an almost undetectable amount of air pressure on the patient's lungs.

11. Wet spirometer - the volume of the chamber is varied by means of a lightweight piston that moves freely in a cylinder as air is withdrawn and replaced in breathing -A Silastic rubber seal between the piston and the cylinder wall keeps the chamber airtight Broncho spirometer is a dual spirometer that measures the volumes and capacities of each lung individually

12. spirogram output of a spirometer is the spirogram -The recording is read from right to left. -inspiration moves the pen toward the bottom of the chart and expiration toward the top. maximal voluntary ventilation (MVV) record

13. Pulse measurements pulse is heart rate heart rate is the number of times heart beats in one minute. Blood volume change in any part of the body is the measure of Pulse rate Plethysmograph is the Instrument used to measure the volume change Plethysmography is methods for recording volume changes of an organ or a body part Principle of ‘true’ Plethysmograph - It consists of rigid cup or chamber placed over the limb in which volume change is measured -chamber filled with fluid or air -changes of volume in the limb due to heart beat(systole and diastole) create a pressure changes inside the chamber. -pressure or displacement transducer provide a signal in respond to pressure changes within the chamber for each heart beat

14. -If the cuff is not inflated , the output signal is a sequence of pulse proportional to the volume changes with each heartbeat -If the cuff is inflated to a pressure just above venous pressure, arterial blood can flow into the cuff, but venous blood cannot leave. -Due to this the volume increases for each heartbeat by the entering of blood during each beat. The output slope of a line along the peaks of these pulsations represents the overall rate at which blood enters the limb -after a few seconds the slope tends to level off due to the back pressure builds up in the limb from the accumulation of blood that cannot escape. Blood volume record from plethysmograph . ‘True’ Plethysmograph

15. capacitance plethysmograph - used on either the arm or leg - one plate of a capacitor is limb in which the volume is being measured, other plate is a fixed screen held at a small distance from the limb - Pulsations of the blood in the arm or leg cause variations in the capacitance, because the distance between the limb and the fixed screen varies with these pulsations -capacitance measuring device is then used to obtain a continuous measure of these variations -capacitance can be calibrated as volume variations

16. Mercury Strain Gage Plethysmography Strain gage is made of silicone rubber tubes, which are filled with conductive liquid (e.g. mercury) whose resistancechanges with volume. -For each pulse the volume of the limb increases, -So the strain gauge elongates and increases its resistance. since the mercury strain gage is extremely low impedance, this necessitates the use of a low-impedance bridge to measure small resistance variations -The resistance variation is converted into voltage changes that can be recorded

17. Photoelectric plethysmograph (Pulse oximetry) volume changes in a limb result in changes in the optical density It consists of a light source and light sensor light source illuminates a small area of the fingertip or other region to which the transducer is applied. Photocell which is shielded from all other light, pick up the light scattered and transmitted through the capillaries of the region As the capillaries fill with blood (with each pulse), the blood density increases, thereby reducing the amount of light reaching the photocell. This changes resistance of the photocell that can be measured on a Wheatstone bridge and recorded. Drawback-1.movement artifacts 2. light source produce heat that changes the circulation

18. Impedance Plethysmography Electrodes are attached to a segment of tissue, The resulting impedance is measured. As the volume of the tissue changes, in response to the pulsation of blood (as happens in a limb) or the resistivity changes in response to increased air in the tissue, the impedance of the tissue changes.

19. two-electrode or four-electrode system is used - The electrodes are either conductive bands wrapped around the limb or simple conductive strips of tape attached to the skin through electrolyte jelly -In a two-electrode system , a constant current is forced through the tissue between the two electrodes, and the resulting voltage changes are measured. -In the four-electrode system , the constant current is forced through two outer(current)electrodes, and the voltage between the two inner(measurement) electrodes is measured. - The driving current is ac, square wave, (10 kHz or higher) to reduce the effect of skin resistance. advantage of the four-electrode system smaller amount of current(few microampere) through the measuring electrodes, thus reducing the possibility of error due to changes in electrode resistance.

20. Measurement of blood flow - Measure the blood flow in vessels - measure the blood velocity -rate of flow of liquid in a pipe =volume of liquid pass through the pipe/unit time, unit- lit/min or mm/min Blood flow meter in clinical application based on the principle 1. Electromagnetic induction 2. ultrasound transmission 3.Thermal convention 4. Radiographic principles

21. I. Magnetic Blood Flow Meters - based on the principle of magnetic induction -When a conductor is moved through a magnetic field , a voltage is induced in the conductor proportional to the velocity of its motion . - A permanent magnet positioned around the blood vessel -it generates a magnetic field perpendicular to the direction of the blood flow. -The induced voltage is measured with electrodes located on opposite sides of the blood vessel and perpendicular to the direction of the magnetic field

22. BME 312-BMI II-L3-ALİ IŞIN 2015

23. magnetic blood flow probes 1. slip-on or C type-long time ( cronic )use - squeezing (press) blood vessel together and slipping it through the slot of the probe. - some probes , slots closed by plastic segment, Contact is provided by protruding platinum disks -touch the wall of the blood vessel. - diameter 2 to 20mm in increasing in steps of 0.5 or 1 mm 2. cannula type – - blood flows through a cannula ( thin tube inserted in to the vein) - around this magnet is placed. - The contacts penetrate the walls -requires the blood vessel be cut, its ends slipped over the cannula and secured with a suture - used in extracorporeal devices( eg . Dialyzers) for blood flow measurement 3. cathetertip - transducers design is catheter type-turned **inside out,'' -electromagnet located inside the catheter and electrodes outside.

24. - output voltage of a magnetic blood flow transducer is very small(few microvolts ) - magnets are driven by alternating currents to overcome electrode polarization and amplifier drift . -change of magnetic field causes the transducer act like a transformer and induces error voltages that exceed the signal levels - amplifiers with large dynamic range and phase-sensitive detectors are used. -To minimize the problem, several different waveforms for the magnet current is used

25. induced sinusoidal voltage is 90° out of phase with the flow signal. the induced voltage is partially balanced out using a suitable circuit, similar to a bridge Square wave-spikes with extremely high amplitude Trapezoidal-spikes with less amplitude

26. Block diagram of Magnetic blood flow meter - osc - oscillator drives the magnet and provides a control signal for gate (60 - 400 Hz) - Gate-reverse the polarity of output signal when the flow direction reverses - Frequency response of the system is high to allow the recording of flow pulse Low pass Filter-drive the mean or average flow

27. II. Ultrasonic Blood Flow Meters - ultrasonic energy is used to measure the velocity of flowing blood two different ways transit time ultrasonic flow meter- pulsed beam is directed through a blood vessel at a shallow angle - its transit time is measured . - transit time increases if blood flow and energy transmission are in opposite direction, and decreases when they are in same direction. t - transit time D - Distance between the transducers c - Sound velocity u - blood flow velocity

28. 2.Doppler type ultrasonic flow meter - based on Doppler principle - oscillator (several megahertz) excites a piezoelectric transducer (barium titanate ) - transducer is coupled to the wall of blood vessel and sends ultrasonic beam (frequency F) into the flowing blood -small part of the transmitted energy is scattered back due to moving blood cells -and received by a second transducer opposite to the first one with frequency F + F D or F - F D , depending on the direction of blood flow due to Doppler effect

29. - F D (Doppler shift) is propositional to velocity of blood flow - fraction of the transmitted energy reaches the second transducer with the same frequency F. -composite signal is amplified and Doppler frequency is obtained at the output of the detector -Doppler frequency(low Audio frequency range) is the difference between direct and scattered frequency com ponents

30. Blood Flow Measurement by Thermal Convection -hot object in a colder- flowing medium is cooled by thermal convection The rate of cooling is proportional to the rate of the flow of the medium. 2 methods thermistor in the bloodstream is kept at a constant temperature by a servo system. -The electrical energy required to maintain constant temperature is a measure of the flow rate. 2. Thermostromuhr ( heat current clock) electric heater is placed between two thermocouples or thermistors along the axis of the vessel. -The temperature difference between the upstream and downstream sensor is a measure of the blood velocity .

31. Blood Flow Determination by Radiographic Methods Blood is not visible on an X-ray image because it has same radio density as the surrounding tissue Method By the injection of a contrast medium ( iodated organic compound) into a blood vessel , the circulation pattern can be made visible . Obstructions can be detected. The blood flow in certain blood vessels can be estimated – angiography Injection of a radioactive isotope into the blood circulation allows the detection of vascular obstructions (lung) with an imaging device (scanner or camera)

32. Cardiac output Cardiac output : The amount of blood pumped by the heart through the circulatory system(pulmonary artery and aorta) in a minute -Flow rate at (pulmonary artery and aorta), normal adult-3.5 to 5 lit/min stroke volume(amount of blood ejected during each heart beat)=total volume of blood in circulation/cardiac output

33. Cardiac output measurement Methods 1. Indicator Dilution 2. Thermo Dilution 3. Fick’s Method

34. 1.Indicator or Dye dilution Method -It is a method of blood flow measurement, not blood velocity Indicator -Any substance that mix with blood and its concentration in blood is measured after mixing -Concentration is measured by light absorbance with calorimeter or radioactive isotopes Requirements of indicator 1. substance is stable and should not be retained in the body 2. No toxic side effect Cardio green or Indocyannine green in isotonic solution is used as dye Principle consider two cases case 1- indicator is injected in to the blood flow continuously beginning at time ‘t‘ at a constant injection(infusion )rate ‘ I’ (temperature lower than the body) Assume the blood is circulated not recirculated

35. - Detector connected to the recorder measure the concentration from the injection point -after the injection the concentration increases and finally reaches a constant value C (unit-liter/min) -When recirculated , indicator concentration increases in steps Case 2 Indicator is injected as bolus(single dose) for open system(Circulation alone) -Concentration increases and reaches a peak P, then decays exponentially (velocity of blood spread the bolus) Flow F =Amount of injected indicator(B)/ Area under the concentration curve(A) A =

36. After Recirculation -Concentration does not monotonically decreased , a hump R occurs. -Finding the area under the recirculation curve is difficult by considering the recirculation (hump)

37. 2.Thermal dilution method Measure the cardiac output using the temperature difference Cold saline(10ml) indicator is used to avoid hump problem in dye dilution method Cool saline rewarm the blood rapidly Injection of cool saline and measurement of blood temperature are performed by special type of catheter( Swan- Ganz catheter ) The catheter contains four separate lumens First lumen -terminates about 30 cm from the tip -used to inject the cooled saline 2 nd lumen-contain 2 thin wires -temperature sensor(thermistor) is connected 3 rd lumen-at catheter tip -pressure measurement 4 th lumen-inflate small rubber ballon at the tip the catheter

38. -Once the catheter has been inserted into a vein, the ballon is inflated and the returning venous blood carries the catheter until its tip is positioned in the pulmonary artery. -The position of the catheter can be checked by measuring the pressure at its tip -The thermistor measure the blood temperature during injection = change of temperature Analog computer-gives the cardiac output directly

39. . In the thermodilution method, cold saline is injected into the right atrium and temperature is measured in the pulmonary artery

40. 3.Fick’s Method

41. Fick’s method- - Indicator used for the measurement of cardiac output is oxygen(O 2 ) of the inhaled air that is injected into blood in the lungs Flow Infusion rate I = consumption of O 2 = difference between O 2 content of the inhaled room air and O 2 content of the exhaled air -This is measured by a spirometer - part of the oxygen is consumed in the systemic circulation and the returning venous blood still contains some oxygen - oxygen concentration in the returning venous blood( C V )is determined and is subtracted from the oxygen concentration in the arterial blood leaving the lungs( C A .) C =C A -C V The arterial-venous concentration difference is measured by drawing samples through catheters placed in an artery and in the pulmonary artery -The measurements are averaged over several minutes to reduce the influence of short-term fluctuations. F= I /( C A -C V )

42. Blood pressure Blood pressure is pressure variation from systole to diastole -It is an indicator of the status of the cardiovascular system When the heart contracts blood is forced through the arteries blood pressure is maximum  systolic pressure typical value: 120 mmHg( millimetre of mercury) When the heart muscle relaxes blood pressure is minimum  diastolic pressure typical value: 80 mmHg Systolic/diastolic 120/80 mmH g Typically the blood pressure is quoted as 120 / 80 mmHg High blood pressure(hypertension) : either of these pressures is higher than this value

43. Blood pressure measurement method 1.Direct –invasive method -direct pressure measurement by inserting a catheter/needle into the artery/vein - This is used when high degree of accuracy and dynamics response is needed 2. Indirect-non invasive method -pressure is measured by a cuff over the limb using korotkoff sound

44. Indirect method ( auscultatory method) -This method uses a sphygmomanometer and a stethoscope - sphygmomanometer has pressure cuff, cuff consists of rubber bladder inside an inelastic fabric -cuff is inflated with a rubber bulb and deflated slowly through a needle valve

45. Principle - cuff placed in upper arm and inflated - the arterial blood flow into the cuff when arterial pressure exceeds pressure in the cuff - when the cuff is inflated, turbulence is generated in the blood during each systole. The sounds generated by this turbulence is known as Korotkoff sounds , can be heard through a stethoscope

46. -When the pressure in the cuff is above systolic pressure , no sounds can be heard through the stethoscope -The pressure in the cuff is gradually reduced and falls below systolic pressure, first Korotkoff sounds begins -The pressure at this point indicated in the manometer is recorded as the systolic blood pressure . -As the pressure of cuff continues to drop , the Korotkoff sounds disappears at a point . This is recorded as diastolic pressure -Since this method uses Korotkoff sounds for locating the systolic and diastolic pressure , this is called the as auscultatory method

47. OSCILLOMETRIC METHOD –BLOOD PRESSURE MEASUREMENT Automated method of non invasive BP measurement It has some distinct advantages over the auscultatory method Sound is not used during measurement This technique does not require a microphone or transducer in the cuff.

48. Principle: as an occluding cuff deflates from a level above the systolic pressure, the artery walls begin to vibrate or oscillate as the blood flows turbulently through the partially occluded artery these vibrations will be sensed in the transducer system monitoring cuff pressure. As the pressure in the cuff further decreases, the oscillations increase to a maximum amplitude and then decrease until the cuff fully deflates and blood flow returns to normal.

49. The cuff pressure at the point of maximum oscillations usually corresponds to the mean arterial pressure. The point above the mean pressure at which the oscillations begin to rapidly decease in amplitude correlates with the diastolic pressure.

50. OSCILLOMETRIC METHOD

51. The oscillometric method is based on oscillometric pulses (pressure pulses) generated in the cuff during inflation or deflation. Blood pressure values are determined from the locus or envelope formed by plotting oscillometric pulses against the baseline cuff pressure -oscillometric pulse index The baseline cuff pressure at which the envelope peaks (maximum height) is generally regarded as the MAP (mean arterial pressure). Height-based and slope-based criteria have been used to determine systolic and diastolic pressures.

52. Ultrasonic Doppler Shift Method of blood pressure measurement designed based on the ultrasonic detection of arterial wall motion. The control logic in the instrument analyzes the wall motion signals to detect the systolic and diastolic pressures and displays the corresponding values. A cuff is placed on the arm , with an ultrasonic transducer on the arm over the brachial artery. The cuff is inflated first to above systolic pressure and then deflated A low energy ultrasonic beam (less than 50 mw/cm2 ) at a frequency of 2 MHz is transmitted into the arm.

53. The portion of the ultrasound that is reflected by the arterial wall shifts in frequency when the wall of the artery moves. Above systolic, the vessel remains closed due to the pressure of the occluding cuff, and the monitor signals are not received. As the cuff pressure falls to the point where it is just overcome by the brachial artery pressure, the artery wall snaps open. This opening wall movement, corresponding to the occurrence of the first Korotkoff sound, produces a Doppler-shift which is interpreted by logic in the instrument as systolic and displayed accordingly.

54. With each subsequent pulse wave, a similar frequency shift is produced until at the diastolic pressure the artery is no longer occluded. Its rapid motion suddenly disappears and the Doppler-shift becomes relatively small. The instrument notes the sudden diminution in the amplitude of the Doppler shift and cuff pressure at this point is displayed as diastolic pressure. Special electronic circuits used in the instrument help to discriminate against extraneous motion artefacts

55. palpatory method - similar to auscultatory method except that the physician identifies the flow of blood in the artery by feeling the pulse of the patient downstream from the cuff instead of listening for the Korotkoff sounds. -Although systolic pressure can easily be measured by the palpatory method, diastolic pressure is much more difficult to identify.

56. Direct measurement -inserting a catheter(glass tube) into the artery Two types of catheter 1.sensor mounted on the tip of the catheter . Pressure exerted is converted to propositional electrical signal 2. Fluid filled catheter - the pressure exerted to a fluid filled column is transmitted to an external transducer - Pressure transducer convert the pressure signal into electrical signal .this electrical signal can be amplified and displayed or recorded The tubes can be inserted by the following procedure 1. Percutaneous insertion. 2. Catheterization (vessel cutdown ). 3. Implantation of a transducer in a vessel or in the heart.

57. Fluid filled catheter Fluid filled catheter

58. -circuit is used for processing the electrical signal from the pressure transducer - transducer is excited with 5V dc from an amplitude controlled bridge oscillator through an isolating transformer -An operational amplifier amplifies the electrical signal corresponding to arterial pressure -the input stage of the operational amplifier is an differential circuit which amplifies the pressure variation -The gain of the amplifier is adjusted depending on the sensitivity of the transducer Measurement of systolic pressure For systolic pressure measurement , conventional peak reading type voltmeter is used. -when a positive going pressure pulse appears at A , the diode D 3 conducts and charged C 3 to the peak value of the input signa l which corresponds to the systolic pressure - time constant R 3 C 3 is chosen to give a steady output to the indicating meter M 1

59. Measurement of diastolic pressure A clamping circuit consisting of C 1 and D 1 is used to develop a voltage equal to the peak to peak value of pressure pulse -This voltage appears across R 1 - Diode D 2 would then conduct and charge capacitor C 2 to the peak value of the peak signal - The diastolic pressure is indicated by a second meter M 2 which shows the difference between peak systolic and the peak to peak pulse pressure signal -The mean arterial pressure is read by a smoothing circuit if needed

60. 1. If systolic and diastolic blood pressures are given as 110 mm Hg and 82 mm Hg. Calculate mean arterial pressure. Mean Arterial Pressure = [(2 x diastolic)+systolic] /3 =[(2x110)+82]/3 =91.3mm Hg 2. Calculate the stroke volume in millilitres if the cardiac output is 5.2 liters/minute and heart rate is 76 beats/minute. Stroke volume=cardiac output/Number of heart beats per minute Stroke volume=5.2x1000/76=68.42 ml.