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BP measurement technique and the newer methods

BP measurement technique and the newer methods



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Bp measurement seminar navin Presentation Transcript

  • 2. Rev. Stephen Hales (1677-1761) BP= 8 feet 3 inches of water
  • 3. Italian physician, is credited with developing the first conventional mercury sphygmomanometer in 1896.
  • 4. MILESTONES….. • Hales first measured blood pressure in 1733 by inserting tubes directly into the arteries of animals. • Sphygmograph was invented by Karl Vierordt in 1855. • Samuel Siegfried Karl Ritter von Basch developed the rubber ball filled with water /mercury to occlude the artery in 1880.Invented the sphygmomanometer in 1881.(water filled) • 1896 Scipione Riva-Rocci introduced the Mercury sphygmomanometer. • 1901 Harvey Cushing modernized the device and applied routine blood pressure measurement in operating rooms. • Nikolai Koroktoff 1905applied the cuff with the stethoscope (developed by Renne Lannec-French Physician) to measure systolic and diastolic blood pressures.
  • 6. TYPES OF MANOMETER • The word comes from the Greek sphygmós (pulse), plus the scientific term manometer (pressure meter). • Saline manometer – long tubing, damping & inertia • Mercury manometer- high inertia • Aneroid manometer • Electro manometer
  • 7. ARM SPHYGMOMANOMETER MERCURYCUFF BASED DEVICES • The air in the cuff acts on a liquid forcing it up a manometer. • Mercury is used as it has 13.6 times the density of water and is liquid at room temp. (A systolic pressure of 120 mm of mercury equates to 1.62 m of water ) • Unlike water, the meniscus created by a level of mercury is convex upwards. Measurement is taken from the top of the meniscus. • A sphygmomanometer uses an open manometer and measures gauge pressure, e.g. pressure over atmospheric pressure. • Closed manometers are used in mercury barometers and measure absolute pressure hence require a large column of mercury as the measurement would include atmospheric
  • 8. • In closed manometers,A meniscus forms below a Torricellian vacuum. (has a pressure equal to that of the saturated vapour pressure of mercury). • Height of a column of mercury is only proportional to the force exerted upon that column. • Therefore, the width and shape of the manometer has no bearing on the height of the column or on measurement
  • 9. Palpatory Method (Riva-Rocci Method) Pressure required to occlude the brachial artery can be used to estimate BP without sphygmomanometer ADVANTAGES +) The blood pressure can be measured in noisy environment too +) Technique does not require much equipment DISADVANTAGES -) Only the systolic pressure can be measured (not DP) -)Can underestimate systolic pressure by upto 25% -) The technique does not give accurate results for infants and hypotensive patients and patients in arrhythmias -)Several measurements should be done as the respiration and vasomotor waves modulate the blood pressure levels Pickering TG et al Circulation 1954;10(4): 481–90 Magee P etal Oxford University Press, 2005; 68–79
  • 10. Auscultation over the brachial artery while using a Riva Rocci cuff was first described in 1905 by Nicolai Korotkoff, a Russian army sergeant. AUSCULTATORY METHOD • The cause of the sounds is uncertain but may be due to :– formation of bubbles within the blood (cavitation theory) – sudden stretching of the vessel wall (arterial wall theory) – turbulence within the vessel (turbulence theory) – or a most likely a combination of factors. • The frequency range is 20300 Hz
  • 11. KOROTKOFF`S SOUNDS • Phase I – sudden appearance of tapping sounds- sys. BP Phase II – 5 to 10 mm Hg lower than first point – soft /swishing sounds – palpable pulse appears Auscultatory gap Phase III - rise in intensity of sounds Phase IV – muffled/blowing sounds. :-AR , Children Phase V - disappearance of sounds ( 5 to 10 mmHg lower than phase IV ):-normal diastolic pressure also in pregnancy(BHS)
  • 12. PREPARATION • Patient should abstain from eating, drinking, smoking and taking drugs that affect the blood pressure one hour before measurement. • Pt should avoid coffee, smoking or any other unprescribed drug with sympathomimetic activity on the day of the measurement • If the sleeves are too tight or bulky they act as a tourniquet • Because a full bladder affects the blood pressure it should have been emptied.
  • 13. PREPARATION • Painful procedures and exercise should not have occurred within one hour.(usually after 5 minutes BP levels usually recover after mild exercise) • Patient should have been sitting quietly for about 5 minutes. • Assess to see if the patient is anxious ,uneasy , upset or in pain. • BP should be recorded in quiet room and comfortable temperature, must record room temperature and time of day • Try to measure BP at the same time of day where practically possible.
  • 14. POSITION OF THE PATIENT • Sitting position preferred • Arm and back are supported. • Muscle contraction in an unsupported arm can raise diastolic BP by as much as 10 per cent • Not supporting back of patient increases diastolic BP by 5-6 mm hg(do not use stool) • Feet should be resting firmly on the floor/not dangling • Feet should not be crossed(2-8 mm hg) • If patient cannot be made to sit then in supine position arm should be supported by a pillow
  • 15. POSITION OF THE ARM • Patient arm should be resting on the desk and raised to the level of mid RA(by using a pillow) • Level of arm should be at mid heart level k/as phlebostatic axis( 4th intercostal space, halfway between the anterior and posterior diameter of the chest) • If the arm is held too high, the reading will be artifactually lowered and vice versa(0.7 mm Hg /cm) • Palm facing up. • The arm should remain somewhat bent(not grossly flexed) and completely relaxed American association of critical care nurses revised april 2010.B.Martin/Jules Constant
  • 16. ADULT CUFF SIZE – Cuff Width: 40% of limb's circumference or 20% more than upper arm diameter(1.2 x diameter) – Cuff Length: Bladder should be 80% of limb's circumference – If it is too small, the readings will be artificially elevated and vice versa – Indications for large cuff or thigh cuff • Upper arm circumference >34 cm – Indications for forearm cuff (with radial palpation) • Upper arm circumference >50 cm
  • 17. • Cuff should be tied snugly • Slightly larger cuff is better than slightly smaller cuff.(Jules constant) • In fat patients if we are using a small cuff – Tie over forearm to measure radial artery pressure. – Use correction factor 32-(1.05xarm circumference in cm). – If number is positive add to the measured systolic value else subtract it.
  • 18. PEDIATRIC CUFF SIZE • Pediatric Cuff size – Minimum Cuff Width: 2/3 length of upper arm – Minimum Cuff length: Bladder nearly encircles arm
  • 19. CUFF POSITION • Patient's arm slightly flexed at elbow • Cuff applied directly over skin:else overestimation of BP • Avoid rolling up a sleeve. Creates torniquet effect. • Position lower cuff border 2.5 cm above antecubital fossa • Center inflatable bladder over brachial artery
  • 20. • BP cuffs should not be applied over a peripherally inserted central catheter (PICC) or midline catheter site but may be placed distally to the insertion site. Int J Clin Monit Comput. 1996;13:167-171. • BP measurements should not be taken in extremities with peripheral IV cannula if there is infusion is running or any trauma/incision. Non invasive Monitoring, 2nd ed. Sudbury, MA: 2005:83-97. • For patients who have had a mastectomy or lumpectomy, do not use the arm on the same side if there is lymphedema. J Clin Monit Comput. 2000;16:557-62 • BP cuffs should not be used on an extremity with a deep vein thrombosis, grafts, ischemic changes, arterio venous fistula, or arterio venous graft J Inf Nurs. 2006;29:S46-7.
  • 21. KEEP IN MIND…!! • The manometer scale should be at eye level, and the column vertical. • The patient should not be able to see the column of the manometer • With your left hand place the stethoscope head directly over the artery. • The stethoscope should be held snugly with no air but pressing can underestimate diastolic BP. Launde,klitzner,Moss 1983
  • 22. • Diaphragm (Better air seal)>Bell(low pitched sound) of stethoscope. In shock Bell>Diaphragm.(Jules constant). • Avoid moving your hands or the head of the stethoscope as this may produce noise artifact • Patient and physician should remain quiet during BP measurement. • The stethoscope should be held by the stem and not by holding/pressing the bell or diaphragm of stethoscope.
  • 23. • The stethoscope should not be in contact with the cuff or the clothing. • Putting Stetho under cuff increases artifacts but increases intensity of Korotkoff sound (Jules constant). • Auscultation in pregnant women underestimates systolic and overestimates diastolic BP and phase V represents diastole more accurately Am J Obstet Gynecol. 1994 Sep;171(3):661-7.
  • 24. CUFF INFLATION AND DEFLATION…!! • Inflate the cuff until you can no longer feel the pulse to level above suspected SBP . The sphygmomanometer's cuff inflation rate should normally be no greater than 80mmHg/second to minimise patient reaction. • Inflate to 140 mm Hg,If you immediately hear sound, pump up an additional 10/20 mmHg and repeat .Inflation to very high levels causes pain and may increase BP. Jules constant • Deflate cuff slowly at a rate of <3 mmHg per second(beat) Deflation rates >2/3 mm per second can lead to a significant underestimation of systolic and overestimation of diastolic blood pressure. British HTN soceity
  • 25. REPEAT MEASUREMENT…!! • To repeat the BP measurement allow the cuff to completely deflate, permit any venous congestion in the arm to resolve and then repeat a minute or so later. • At least two measurements (1-2 mins apart) should be taken at each occasion. • If there are large (greater than 10mmHg) differences between initial readings ,the initial assessment should be discarded and further measurements made. • If the BP is surprisingly high or low, repeat the measurement towards the end of examination
  • 27. OTHER SITE MEASUREMENT • The two arm readings should be within 10-15 mm Hg. Differences greater then 10-15 imply differential blood flow. • Forearm:- position the cuff midway between the elbow and the wrist. • Calf:- position the lower edge of the cuff approximately 2.5cm above the malleoli. • Thigh:- position the cuff over the lower third of the thigh so that the lower edge of the cuff is approximately 2 to 3cm above the popliteal fossa.
  • 28. • Measurement of leg BP should be done using large thigh cuff and auscultation of popliteal artery with large arm cuff and auscultation of the posterior tibial artery with bell(jules constant) • Place the patient in the prone position for thigh BP measurements. If the patient cannot be placed in the prone position, position the patient supine with knee slightly bent • Systolic pressure increases and diastolic pressure decreases when pressure in measured in distal arteries eg at wrist(mean pressure does not change)
  • 29. AUSCULTATORY GAP • The common auscultatory gap occurs in the second or murmur phase. • Although recognized clinically a year after Korotkoff introduced the auditory method (1906), the clinical importance of the auscultatory gap was not recognized until 1917, when Cook and Taussig emphasized the need for preliminary palpation of the pulse. • An underestimation of systolic blood pressure and/or an overestimation of diastolic blood pressure.
  • 30. • TYPES: • 3 types of auscultatory gaps, have been identified by using wideband external pulse recording. – G1: occurs with cuff pressure just below systolic and is characterized by the presence of K1 and K2 with intermittent disappearance of K2. G1 gaps are related to a phasic decrease of arterial (systolic) pressure. – G2: are related to a phasic increase of arterial (diastolic) pressure, occur when cuff pressure is just above diastolic, and are characterized by the presence of K1, K2, and K3 with intermittent disappearance of K2. – G3: occurs with cuff pressure between systolic and diastolic and are characterized by an underdeveloped or blunted K2 signal. Seymour G. Blank, James E. West et al Hypertension 1991;17:225-233
  • 31. MECHANISM/HYPOTHESIS – The mechanism of origin of auscultatory gap has not been understood clearly. – Cavallani showed that the early loss of audible sound during cuff deflation is associated with blunted high frequency K2 signals associated with korotkoff sound (detected by wideband external pulse recording) likely related to the altered physical properties of a stiffer arterial wall. – Auscultatory gaps are related to carotid atherosclerosis and to increased arterial stiffness in hypertensive patients, independent of age
  • 32. – Venous engorgement of the upper extremity with poor antegrade flow – The auscultatory gap is most likely to appear in the obese arm, especially if the physician pumps up the cuff slowly and traps a great deal of blood in the arm’s venous compartment. – Trapping of blood by pumping the cuff 2nd time immediately after 1st determination, without allowing 12 minutes for the trapped blood to escape
  • 33. PRECAUTIONS TO AVOID THE GAP • Elevating systolic pressure to high levels before deflation • Inflating cuff quickly can decrease venous congestion (Jules constant) • Determining systolic blood pressure by palpatory method before recording the blood pressure with auscultatory method • Inflating the blood pressure cuff to 20-40 mmHg higher than the pressure required to occlude the brachial pulse. • Can be eliminated by clenching the fist several times before measurement • Elevate subject’s arm overhead for 30 seconds then bring arm to usual supported position to remeasure
  • 34. AUSCULTATORY METHOD ADVANTAGES +) Auscultatory technique is simple and does not require much equipment DISADVANTAGES -) Auscultatory tecnique cannot be used in noisy environment -) The observations differ from observer to another -) A mechanical error might be introduced into the system e.g. mercury leakage, air leakage, obstruction in the cuff etc. -) The observations do not always correspond with intra-arterial pressure.Lower systolic and higher diastolic pressures are recorded than intra arterial recording. -) The technique does not give accurate results for infants and hypotensive patients
  • 35. ERRORS– AN OVERVIEW CAUSE SYSTOLIC BP CORRECTIVE ACTION Sit without back support + 6 to 10 Support back (sit in chair) Full bladder + 15 Empty bladder before BP taken Tobacco/caffeine use + 6 to 11 Don’t use before clinic appointment BP taken when arm is: Parallel to body Unsupported Elbow too high Elbow too low + 9 to 13 + 1 to 7 +5 False low While seated in chair, patient’s arm must be straight out and supported, with elbow at heart level “White coat” reaction + 11 to 28 Have someone else take the BP Talking or hand gestures +7 No talking or use of hands during BP Cuff too narrow/small + 8 to 10 Cuff too wide/large False low Cuff not centered +4 Cuff over clothing + 5 to 50 Right-sized cuff properly placed over bare upper arm (Pickering et al., 2005; Perry & Potter, 2006)
  • 36. MERCURY:-SHOULD IT BE USED?... Exposure to mercury can occur three ways: inhalation, ingestion and absorption. The most likely route of inorganic mercury is through inhalation after a spill.  The elemental mercury used in thermometers and Manometers is converted by microorganisms in the environment to methyl mercury, the most toxic form.
  • 37.  Methyl mercury is a neurotoxin and especially dangerous to fetus and young children. A 2001 CDC study found that 10% of women have mercury levels high enough to cause neurological damage to their children.  Hospitals contribute 4-5% of the total waste water mercury load. There is up to 50 times more mercury in medical waste that in general municipal waste. Mercury from thermometers contribute about 17 tons of mercury in landfills annually.
  • 38. • ACUTE EFFECTS:Headaches, chills, fever chest tightness, coughs , pneumonitis , bronchitis hand tremors nausea, vomiting, abdominal cramps, diarrhea • CHRONIC EFFECTS:Personality changes Decreased vision or hearing Peripheral nerve damage Elevated blood pressure Memory loss ,stupor , coma
  • 39. Minamata disease is a neurological syndrome include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In extreme cases, insanity, paralysis, coma, and death follow within weeks. Children are especially sensitive to mercury and at risk of developing a condition known as acrodynia or “Pinks Disease” The symptoms of this condition include:  reddening of the palms and soles of the feet  itching with peeling skin  increased heart rate and blood pressure  behavioral changes  muscle weakness  sweating and hair loss
  • 40. IN CASE OF SPILLAGE…!! • Do not touch the mercury with your bare hands. • Do not use broom or paintbrush. • Never attempt to vacuum up the mercury it will blow vapors into the area and also contaminate the cleaner • If possible, close off the room and the heat or air conditioning in that room. Keep the incident room under 70 degrees F to minimize mercury evaporation. • NEVER use household cleaning products, especially those containing chlorine or ammonia, because they may react violently with the mercury and release toxic gases.
  • 41. • NEVER allow people whose shoes or clothing may be contaminated with mercury to walk around your house. • NEVER put mercury in the trash/burn barrel/ drain. • If the mercury spill is in the manometer case, close the case of the blood pressure manometer, put the case in a plastic trash bag and secure tightly with a twist tie. • Use the mercury (Hg* Absorb) sponge(powder coated),rubber, plastic.
  • 42. ANAEROID SPHYGMOMANOMETER • An increase in pressure expands the bellows, which then moves a pointer along a scale to indicate pressure. • They depend upon the linkage b/n the diaphragm and the display needle. • They are susceptible to loss of accuracy over time and hence require regular calibration using mercury mano at different BP levels. • Mercury manometer is better in elderly, children, pregnant women, patients with aortic insufficiency and anaemia.British HTN Society Guidelines
  • 43. HYBRID SPHYGMOMANOMETERS • Mercury column is replaced by an electronic gauge • Manual hybrid devices have to be used by observer with stethoscope. A microphone or a strain gauge is placed over the brachial artery under the cuff with analyzes and interprets the Korotkoff`s sounds(automated auscultatory devices) • The cuff pressure can be displayed as a simulated mercury column, as a digital readout, or as a simulated aneroid display. • This has the potential of minimizing terminal digit preference
  • 44. OSCILLOMETRIC NIBP • Pneumatic cuff inflated to occlude arterial blood flowThe intra-arterial pulsation is transmitted via cuff to transducer (e.g. piezo-electric) • They do not measure systolic and diastolic pressures directly, but calculate them from the mean pressure and empirical oscillometric parameters. • SBP = rapidly increasing oscillations • MAP = maximal point of oscillations • DBP = rapidly decreasing oscillations
  • 45. • ADVANTAGE – No transducer need be placed over the brachial artery, so that placement of the cuff is not critical. – Potential advantages for ambulatory monitoring are that it is less susceptible to external noise – The cuff can be removed and replaced by the patient, for example, to take a shower. – Even when the korotkoff sounds are hardly detected due to hypotension, the oscillometric method is capable of determining bp because the cuff oscillates as long as the artery pulsation exists. Crit Care Med. 2000;28:371-6 Crit Care Med. 2003;31:793-9.
  • 46. DISADVANTAGE – Amplitude of the oscillations depends on several factors like the stiffness of the arteries causing the mean arterial pressure to be significantly underestimated – Do not work well during physical activity, when there may be considerable movement artifact. – Does not dirctly measure systolic or diastolic pressures – Many devices use fixed algorithms leading to large variance in blood pressure
  • 47. – The bladders deflate at a manufacturer-specific “bleed rate,” which assumes a regular pulse between bleed steps as part of the algorithms – Automated oscillometric devices, as compared to mercury sphygmomanometer, slightly overestimate systolic blood pressure(2.12 mm Hg) and underestimate diastolic blood pressure (2.36 mm Hg) Crit CareMed. 2000;28:371-6, Crit Care Med. 2003;31:793-9
  • 48. VON RECKLINGHAUSEN OSCILLOTONOMETER • Improvement upon aneroid gauge needle • Provides check upon trends of SBP • Uses a double cuff • Proximal cuff measures pressure via bellows M (Occluder cuff) • Distal cuff detects pulsations – bellows D(sensor cuff) • Inflate the cuff above SBP , release tap ‘T’ to allow slow leak of air & to bring bellows D into operation • At the onset of oscillations , tap ‘T’ is released , needle settles down & indicates SBP
  • 49. • Point of maximum oscillation is mean pressure • Systolic pressure is recognized as the point where the rate of increase in the size of oscillation is maximal; diastolic pressure being that of maximal rate of decrease in size of oscillation. • The original DINAMAP is basically an automated oscillotonometer utilizing two cuffs • Accuracy was increased by minimizing the compressible component of the system
  • 50. AUTOMATED OSCILLO METRIC TECHNIQUE • Single cuff is used unlike in oscillotonometer • Transducer measures both pressure & oscillations • Processing unit analyses signal & displays SBP, DBP& MAP • Provided with automatic cuff inflation at set time intervals • Fails to record pressures <50 mm Hg • Inaccurate during dysrhythmias
  • 51. Their use still requires careful patient evaluation for caffeine or nicotine use, selection of the correct cuff size, and proper patient positioning if accurate blood pressures are to be obtained.
  • 52. ULTRASOUND/DOPPLER METHOD • The motion of blood-vessel walls in various states of occlusion is measured. • As the cuff pressure is increased, the time between opening and closing decreases until they coincide  Systolic pressure • Again as the cuff pressure is decreased, the time between opening and closing increases until they coincide  Diastolic pressure • 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.
  • 53. ULTRASOUND/DOPPLER METHOD ADVANTAGE:- Noisy Environment Infants  Hypotensive Individuals/Low Output State Arterial Occlusive State/Coarctation Can Be Used During Cardiopulmonary Resuscitation To Assess Blood Flow Effectiveness DISADVANTAGE: Subject’s movements change the path of the ultrasound beam from sensor to vessel  positioning of detector exactly over artery  Inaccurate during dysrhythmias Only systolic pressure can be obtained accurately
  • 54. CUFF BASED NIBP - COMPLICATIONS • Too frequent inflations – extremity edema – nerve paresthesias – compartment syndrome • Skin irritation • Mercury hazards
  • 55. NON NON INVASIVE MONITORING CONTINOUS ARM CUFF BASED DEVICES PENAZ TECHNIQUE • A small cuff is placed around a finger. • A light emitting diode within the cuff shines infra red light through the finger and is detected on the other side. • The amount of light absorbed by the tissues is proportional to the volume of tissue through which it passes. • The applied pressure waveform correlates to the pressure waveform of the arterial supply to the finger. The information can be displayed as a realtime waveform and as a trend. Ben P.M. Imholz et al Cardiovascular Research 38 1998. 605–616
  • 56. • The system requires calibration using an arm cuff. • Should be used on 3rd or 4th finger /not thumb • The Portapres enables readings to be taken over 24 hours while the subjects are ambulatory, although it is somewhat cumbersome • While highly accurate in vasodilated patients and those with normal circulation, it is less accurate in hypotensive patients or those with vascular insufficiency. Ben P.M. Imholz et al Cardiovascular Research 38 1998. 605–616
  • 57. • Small changes in positioning and tightness of the finger cuff on the same patient can lead to wide variation in readings. • Both systolic and diastolic may be underestimated when compared with brachial artery pressures • Its greatest value is for research studies assessing short-term changes of blood pressure and its variability.
  • 58. TONOMETRY Linear array of pressure sensors is pressed against a superficial artery, which is supported from below by a bone (radial artery). A sensor array is used here, because at least one of the pressure sensors must lay directly above the artery When the blood vessel is partly collapsed, the surrounding pressure equals the artery pressure. The pressure is increased continuously and the measurements are made when the artery is half collapsed
  • 59. TONOMETRY (CONT.) ADVANTAGES +) Can be used for non-invasive, painless, continuous measurement DISADVANTAGES -) Relatively high cost -) The wrist movement and tendons result in measurement inaccuracies -)The hold-down pressure varies between individuals and therefore a ’calibration’ must be done
  • 60. CENTRAL AORTIC PRESSURE • The current "gold-standard“ is direct measurement with a pressure transducer in the aorta at the time of cardiac catheterization • Strong heart study, CAFÉ(ASCOT sub study),REASON • The AtCor Medical device (SphygmoCor®) is the standard radial tonometric device for sitting measurements
  • 61. BP PRO WATCH • Has a high fidelity tonometer incorporated in watch like strap • Watch is worn with tonometer placed over radial artery • The radial waveform is first calibrated to brachial BP measured by an electronic device • Allows ambulatory recording of BP and central aortic pressure • After 24 hrs watch is taken off and waveform analysed • FDA approved
  • 62. BLOOD PRESSURE SENSORS With the new sensor, no cuff is required Device takes advantage of the method called pulse wave velocity which allows blood pressure to be calculated by measuring the pulse at 2 points along an artery Accuracy is more than similar wrist measurement devices using other principle This was developed at MIT's d'Arbeloff Laboratory
  • 63. RING SENSOR  Rationale:-Other personal ornaments and portable instruments, such as ear rings and wrist watches,are not continually worn in daily living.  The ring is packed with LEDs and photo detectors  This sensor is equipped with optoelectric components that allow for long-term monitoring of the patient’s arterial blood volume waveforms and blood oxygen saturation non-invasively and continuously  These signals are transmitted to a home computer and can detect pulse,BP,temperature,saturation
  • 64. NORMAL BP MEASUREMENTS AGE Normal BP Newborn to 6 weeks * Infant (6 weeks to 6 months) * Toddler ( 1 to 3 years) * Young Children ( 3 to 6 years) Older Children (10 to 14 years) Adults Systolic 50 - 70 Systolic 70 - 95 Systolic 80 - 100 Systolic 80 - 110 Systolic 90 - 120 Systolic 90 - 120 Diastolic 80 or less Systolic pressure in children 90+ (age x 5) /3 Diastolic pressure is 60+-10 mm hg in infants and children of all ages Mosby’s Critical Care Nursing , 2002; Perry & Potter, 2006 (bottom line) Jules Constant
  • 65. FREQUENCY OF OFFICE MEASUREMENT BHS GUIDELINE FOR SCREENING • Measure every 5 years all adults up to 80 years • Measure annually those high normal (130-139 or 85-89) and anyone noted to have high readings at any time AFTER CONFIRMATION OF HYPERTENSION • If BP high –repeat monthly over 4-6 months. (Unless BP very high, then measure more frequently) • Do not treat on the basis of an isolated reading NICE GUIDELINE:-BP confirmation If Initial BP > 140/90 repeat monthly for 2 months
  • 66. WHITE COAT HYPERTENSION  Definition  Blood pressure >140/90 mmHg when measured in office  Normal daytime ambulatory pressure <135/85 mmHg  Prevalence of white coat hypertension  10-30% of general population  Common in elderly people and pregnant women Guidelines from British Hypertension soceity
  • 67. Risks  < sustained hypertension/> normotensives  Possibly a precursor to hypertension Clinical Implications      No clinical characteristics assist in diagnosis Must be considered in people newly diagnosed with hypertension Should be considered before drug treatment is prescribed Must be placed in context of the overall risk profile Should reassure patients, employers and insurers that risk from white coat hypertension is low or absent  Patients need follow up re-monitoring
  • 68. MASKED HYPERTENSION REVERSE WC HTN /WC NORMOTENSION • Less frequent than White coat HTN • Lifestyle can contribute to this, eg, alcohol, tobacco, caffeine consumption, and physical activity away from the clinic/office. • M>F.Elderly>Young • Prevalence almost equal to WCH(9%-23% in various studies) • Risk of TOD >WCH. • Evaluated in Ohasama Study, Pamela study • Diagnosed by Ambulatory BP monitoring • Should be t/t as hypertensives.
  • 69. PSEUDOHYPERTENSION • Sphygmomanometric pressure is greater than intra arterial pressure • Seen in pts with stiff calcified, incompressible arteries. • Suspected in patients with BP readings disproportionate to other evidence of TOD • It was present in 7.2% of 3387 persons older than 59 years screened for the Systolic Hypertension in the Elderly Program (SHEP) study—more common in men, and with a history of stroke SHEP J Hum Hypertens. 1997;11:285–289. • Modified Osler maneuver:-Radial pulse is still palpable even after occlusion of proximal brachial artery.(Not reliable) • Non specific sign positive in 1/3rd of unselected elderly patients. Only reliable in pts off anti HTN drugs (Jules constant) • Augmentation index can be calculated by tonometry
  • 70. HOME Ambulatory BP
  • 71. INDICATIONS… European Society of Hypertension guidelines for blood pressure monitoring at home J Hypertens 26:1505–1530 Q 2008
  • 72. European Society of Hypertension guidelines for blood pressure monitoring at home J Hypertens 26:1505–1530 Q 2008
  • 73. European Society of Hypertension guidelines for blood pressure monitoring at home J Hypertens 26:1505–1530 Q 2008
  • 74. European Society of Hypertension guidelines for blood pressure monitoring at home J Hypertens 26:1505–1530 Q 2008
  • 75. NICE GUIDELINES 2011 FOR HBPM  For each blood pressure measurement, two consecutive measurements are taken, at least 1 minute apart and with the person seated  Blood pressure measurements are taken twice daily, ideally in the morning and evening.  Blood pressure measurement continues for at least 4 days, ideally for 7 days.  Discard the measurements taken on the first day and use the average value of all the remaining measurements to confirm a diagnosis of hypertension. Hypertension: NICE guideline DRAFT (February 2011)
  • 76. NICE GUIDELINES 2011 FOR ABPM  Blood pressure is measured for a total of 24 hours  At least two measurements per hour are taken during the day (08:00 to 22:00)  At least one measurement per hour is taken during the night (22:00 to 08:00).  Use the average daytime blood pressure measurement, calculated using a minimum of 14 daytime measurements, to confirm a diagnosis of hypertension. Hypertension: NICE guideline DRAFT (February 2011)
  • 77. Threshold levels of BP for the diagnosis of Hypertension according to measurement method SBP (mmHg) DBP (mmHg) Office >140 >90 Self/home BP Monitoring >135 >85 Ambulatory BP Monitoring Day >135 >85 Ambulatory BP Monitoring Night >120 >75 Ambulatory 24 hr BP Monitoring >130 >80 1 These figures do not necessarily equate with the need for antihypertensive drug treatment to be started and therapy must be based on overall CV risk as well as absolute BP levels. Antihypertensive treatment should however, be initiated in people with sustained office SBP >160mmHg or sustained DBP >100mmHg irrespective of other risk factors. 2 Lower levels of BP to initiate drug therapy may be considered in some instances eg post-stroke, diabetes 3 The highest value of SBP or DBP should be used for classification, whichever method measurement method is used
  • 78. INVASIVE BLOOD PRESSURE Indications – Major surgery/trauma involving large fluid shifts /CPB/Aortic surgery – Patients with pulmonary disease req. freq. Labs – Disturbed myocardial function – dysrhythmias, MI, open heart surgery – Patients with significant valvular or LV dysfunction/ in shock – Procedures using deliberate hypotension or hypothermia – Patients requiring inotropes/balloon counterpulsation/Patients on rapidly acting vasodilators
  • 79. – Inability to measure BP by NIBP (morbid obesity/peripheral edema/burns) – Rapid & extreme changes of pressure/blood volume are likely (phaeochromocytoma & uncontrolled hypotension) – Shape of the waveform can provide some information (Assessment of cardiac contractility or aortic valve disease) – Intravascular volume status can be estimated from the shape of the arterial pressure trace by waveform analysis by pulse contour analysis system. – Patients likely to require continous BP monitoring for prolonged intervals decreases the risk of neurapraxis and tissue injury
  • 80. Contraindications: – Local infection – Coagulopathy (relative) – Proximal obstruction (thoracic outlet synd.) – Vaso-occlusive disorders (Raynaud’s)
  • 81. COMPONENTS • The simplest device to measure pressure was that described by Landois in 1872. • Intravascular Catheters – Short, narrow catheters (20 ga) – 22G, and 25G are available for children and neonates. – Preferably,a non-end artery, such as radial or dorsalis pedis is cannulated. – If thrombosis of the artery occurs, arterial sufficiency is maintained via a collateral supply hence radial artery is preffered • Teflon - soft, less thrombogenic – Clot will overdamp the tracings Critical Care Anesthesiology 1981; 54:227-236. 1997;839-845. J Clin Monit 1989; 5:137-147. (3rd Ed)Lippincott-Raven.
  • 82. COUPLING SYSTEM • Pressure tubing, stopcocks, contain flush device • Major source of distortion of tracings • Most systems underdamped leading to overestimation of SBP • The cannula is connected to a disposable tubing system, which delivers a constant infusion of plain or heparinized 0.9% saline, delivered at a rate of 2–4 ml/h to prevent occlusion of the cannula by thrombus. • The infusion fluid is kept pressurized to ensure a constant flow into the arterial system. Critical Care Anesthesiology 1981; 54:227-236. 1997;839-845. J Clin Monit 1989; 5:137-147. (3rd Ed)Lippincott-Raven.
  • 83. TRANSDUCERS  Convert mechanical energy to electrical energy  The liquid within the infusion tubing is in contact with a diaphragm that moves in response to the transmitted pressure waveform.  The diaphragm of the transducer moves a small plate that is connected to four strain gauges.  All four strain gauges form part of a Wheatstone bridge thus increasing the sensitivity four-fold  The transducer needs to be kept horizontally level with the patient; traditionally, the right atrium(Hydrostatic pressure 0.7 mm/cm change) Anesthesiology 1981; 54:227-236. Critical Care (3rd Ed)Lippincott-Raven. 1997;839-845. J Clin Monit 1989; 5:137-147.
  • 84. ANALYSIS AND DISPLAY SYSTEMS – Computerized – Acquire and display pressure signals – Derive SBP, DBP, MAP – Alarm functions, data storage, trend displays – Most average hemodynamic parameters over several cardiac cycles to minimize respiratory variability – Newer devices use fiberoptic or electrical transducers with lesser artifacts but are expensive and fragile Critical Care Anesthesiology 1981; 54:227-236. 1997;839-845. J Clin Monit 1989; 5:137-147. (3rd Ed)Lippincott-Raven.
  • 85. DAMPING • Optimally damped: The system responds rapidly to a change in signal by allowing a small amount of overshoot (Damping factor= 0.7). • Critically damped:-Critical damping is therefore defined as the minimal amount of damping required to prevent any overshoot. System is relatively slow to respond. (Damping factor 1.0). • Under-damped: Resonance occurs causing the signal to oscillate and overshoot (Damping factor<0.7). • Over-damped: The signal takes a long time to reach equilibrium but will not overshoot. This system will not oscillate freely and detail such as the dicrotic notch will be lost. (Damping factor>1.0). Anesthesiology 1981; 54:227-236. Critical Care (3rd Ed)Lippincott-Raven. 1997;839-845. J Clin Monit 1989; 5:137-147.
  • 86. DAMPING COEFFICIENT • Can be measured clinically using the fast flush test. • Following a system flush, the amplitude ratio of two consecutive resonant waves are calculated by dividing the smaller ratio by the larger. • The respective damping coefficient is then taken from the chart.
  • 87. •Disconnect/loose tubing •Underinflated pressure bag •Catheter tip against wall
  • 88. •Too many stopcocks •Not fully opened stopcock •Defective transducer •Overtly stiff non compliant tubings •reverberations in tubing causing harmonics that distort the trace
  • 89. ARTIFACTS IN PRESSURE RECORDING • Catheter whip artifact – Motion of the tip of the catheter within the heart and vessels accelerates the fluid contained within the catheter. – It may produce superimposed waves of +/- 10mmHg. • End-pressure artifact – Flowing blood has a kinetic energy by virtue of its motion, and when this flow suddenly comes to a halt, the kinetic energy is converted in part into pressure. – An end-hole catheter pointing upstream (Eg - radial or femoral arterial pressure monitoring line) records a pressure that is artifactually elevated by the converted kinetic energy, which may range from 2-10mmHg.
  • 90. ARTIFACTS IN PRESSURE RECORDING • Catheter tip obstruction  in a small vessel. • Catheter impact artifact – When a fluid filled catheter is hit (eg by valves/walls), a pressure transient is created . – Any frequency component of this transient that coincides with the natural frequency of the catheter–manometer system causes a superimposed oscillation of the recorded pressure waves.
  • 91. TROUBLESHOOTING • Keep things simple:-Monitoring systems with multiple stopcocks, multiple injection ports, or long lengths of pressure tubing are subject to degraded dynamic performance as well as an increased risk of infection and contamination. • Remove all air:-Air, by virtue of being more compressible than fluid, tends to act as a “shock absorber” within a pressure monitoring system leading to a overdamped waveform.
  • 92. “Fast Flush Test” • A “fast-flush” or “square wave test” is performed by opening the valve of the continuous flush device such that flow through the catheter-tubing system is acutely increased to 30 mL/hr from the usual 1-3 mL/hr • This generates an acute rise in pressure within the system such that a square wave is generated on the bedside monitor. • With closure of the valve, a sinusoidal pressure wave of a given frequency and progressively decreasing amplitude is generated. • A system with appropriate dynamic response characteristics will return to the baseline pressure waveform within one to two oscillations else check
  • 93. ZEROING THE TRANSDUCER • Atmospheric pressure must be discounted from the pressure measurement • Principle:-exposing the transducer to atmospheric pressure and calibrating the pressure reading to zero. • Opening a stopcock to atmospheric pressure and aligning the resulting air-fluid interface with the level of the right atrium.
  • 94. • A pressure monitoring system should be zeroed at least once each day and whenever the data is suspected to be artifactual. • Appropriately zeroing a patient’s pressure monitoring system is the single most important step in obtaining accurate and meaningful data
  • 95. MICROMANOMETER CATHETERS • Higher natural frequencies and more optimal damping characteristics, because the interposing fluid column is eliminated. • The pressure wave form is less distorted and is without the 30-40 ms delay seen in the fluid filled catheter transducer system. • Commercially available catheters have both an end hole and side hole or 2 transducers at a distance to measure gradients • They have several disadvantages including cost, fragility, and added procedural time.
  • 96. COMPLICATIONS • • • • • • • - Infection Hemorrhage Thrombosis/distal ischemia Skin necrosis Embolization Neurologic injury Pseudoaneurysms loss of digits
  • 97. DISAVANTAGES/CAVEATS • Any drug inadvertently administered into the arterial line may form crystals and cause ischaemia of the limb. Eg. thiopentone and antibiotics. • All arterial lines should be clearly labelled and the tubing colour coded (usually with a red stripe) to avoid confusion and drugs should never be administered via the arterial line. • Time consuming especially in shock patients to put cannula • Expensive
  • 98. LONG-TERM IMPLANTABLE BLOOD PRESSURE MONITORING SYSTEM  The system employs an instrumented elastic cuff, wound around a blood vessel(surgically implanted)  Operates in a linear “diameter v.s. pressure” region of the vessel for real time blood pressure monitoring  The elastic cuff is made of soft bio-compatible rubber, filled with bio-compatible insulating fluid with an immersed MEMS pressure sensor  The MEMS sensor detects the vessel blood pressure wave form with a constant scaling factor, independent of the cuff bias pressure exerting on the vessel.
  • 99. IMPLANTABLE BLOOD PRESSURE MONITORING SYSTEM MEMS sensor Insulating Liquid vessel Cuff
  • 100. WIRELESS -BATTERY LESS MICRO SYSTEM • Wireless powering and data telemetry are also incorporated in the micro system • The device gets charged from external radiofrequency sorurce and tranmits back its recordings similarly • Eliminates the need of external wire connections and any bulky battery • Can be used to obtain reliable measurements without suffering from stress induced distortion
  • 103. ADVANTAGES OF WIRELESS AND BATTERY-LESS DEVICES – No need of connections – Reduced device size – Substantially minimizes vessel movement restriction due to the soft cuff elasticity – Attractive for minimizing long-term adverse biological effects
  • 104. DISADAVANTAGES OF IMPLANTABLE SENSORS:- Invasive technique Not truly biocompatible Difficult to extract No definitive indication as yet Human data lacking Need for suitable coating not affecting performance Cannot be used in small blood vessel/risk of occlusion Need of sufficient bandwidth to measure the entire pressure waveform
  • 105. TAKE HOME MESSAGE  Accurate BP measurement is not as simple as we presume  Small mistakes can lead to unnecessary confusion and prescriptions  Newer technique are advantageous in terms of simplicity , comfort and Mercury avoidance  Invasive BP monitoring is useful if performed accurately for appropriately selected hospitalized patients  The future has lot more to offer than is presently imaginable!!!