equipment used to measure blood pressure manually

equipment used to measure blood pressure manually

Manual meters are best used by trained practitioners, and, while it is possible to obtain a basic reading through palpation alone, this yields only the systolic pressure.Aneroids mounted on walls or stands are not susceptible to this particular problem. They may use manual or automatic inflation, but both types are electronic, easy to operate without training, and can be used in noisy environments.Other sites of placement depend on species and may include the flipper or tail. It is essential that the correct size of cuff is selected for the patient. Too small a cuff results in too high a pressure, while too large a cuff results in too low a pressure. For clinical measurements it is usual to measure and record both arms in the initial consultation to determine if the pressure is significantly higher in one arm than the other. A difference of 10 mm Hg may be a sign of coarctation of the aorta.The pressure at which this sound began is noted and recorded as the systolic blood pressure. The cuff pressure is further released until the sound can no longer be heard. This is recorded as the diastolic blood pressure. In noisy environments where auscultation is impossible (such as the scenes often encountered in emergency medicine ), systolic blood pressure alone may be read by releasing the pressure until a radial pulse is palpated (felt). In veterinary medicine, auscultation is rarely of use, and palpation or visualization of pulse distal to the sphygmomanometer is used to detect systolic pressure.The peak pressure in the arteries during the cardiac cycle is the systolic pressure, and the lowest pressure (at the resting phase of the cardiac cycle) is the diastolic pressure. A stethoscope is used in the auscultatory method. Systolic pressure (first phase) is identified with the first of the continuous Korotkoff sounds. Diastolic pressure is identified at the moment the Korotkoff sounds disappear (fifth phase).In 1901, pioneering neurosurgeon Dr.http://eltechma.com/zdjecia/fck/ds27930-sanyo-manual.xml

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Harvey Cushing brought an example of Riva-Rocci's device to the US, modernized it and popularized it within the medical community.American Journal of Hypertension. 21 (8), p. 845. Australian Family Physician. October 2007; 36 (10):834-838. By using this site, you agree to the Terms of Use and Privacy Policy. In recent testing by Consumer Reports, 29 models were tested with trained medical personnel conducting 6,000 readings on men and women. The upper arm cuff devices were found to be more accurate than wrist devices. The AHA recommends an automatic, cuff-style, upper-arm monitor. The Omron brand (Figure 1) continues to be rated high by Consumer Reports.The size of the patient determines the size of the cuff selected. There are several cuff sizes. The cuff width should be 20% greater than the diameter of the arm. When a cuff is too narrow, the blood pressure reading is too high; when the cuff is too large, the reading is too low. Dental professionals should invest in quality stethoscopes that detect sound easily. Providers should not have to strain to hear sounds. Replace parts to existing stethoscopes or replace entire stethoscope if necessary. Do you want to continue logged in? Please click CONTINUE below to return to your previous page to complete the process. Failure to complete ALL the steps will result in a loss of this test score, and you will not receive credit for this course. Abstract Although the mercury sphygmomanometer is widely regarded as the “gold standard” for office blood pressure measurement, the ban on use of mercury devices continues to diminish their role in office and hospital settings. To date, mercury devices have largely been phased out in US hospitals. This has led to the proliferation of non-mercury devices and has changed (probably for ever) the preferable modality of blood pressure measurement in clinic and hospital settings.http://www.gd-juli.com/userfiles/ds27880-manual.xml

In this article, the basic techniques of blood pressure measurement and the technical issues associated with measurements in clinical practice are discussed. The devices currently available for hospital and clinic measurements and their important sources of error are presented. Practical advice is given on how the different devices and measurement techniques should be used. Blood pressure measurements in different circumstances and in special populations such as infants, children, pregnant women, elderly persons, and obese subjects are discussed. Keywords: blood pressure measurement, self-monitoring, ambulatory blood pressure monitoring Basic techniques of blood pressure measurement Location of measurement The standard location for blood pressure measurement is the brachial artery. Monitors that measure pressure at the wrist and fingers have become popular, but it is important to realize that systolic and diastolic pressures vary substantially in different parts of the arterial tree with systolic pressure increasing in more distal arteries, and diastolic pressure decreasing. Basically, these devices combine the features of both electronic and auscultatory devices such that the mercury column is replaced by an electronic pressure gauge, similar to oscillometric devices, but the blood pressure is taken in the same manner as a mercury or aneroid device, by an observer using a stethoscope and listening for the Korotkoff sounds. 72 The oscillometric technique This was first demonstrated by Marey in 1876, 38 and it was subsequently shown that when the oscillations of pressure in a sphygmomanometer cuff are recorded during gradual deflation, the point of maximal oscillation corresponds to the mean intra-arterial pressure. 32, 39, 97 The oscillations begin at approximately systolic pressure and continue below diastolic ( Fig. 1 ), so that systolic and diastolic pressure can only be estimated indirectly according to some empirically derived algorithm.

This method is advantageous in that no transducer need be placed over the brachial artery, and it is less susceptible to external noise (but not to low frequency mechanical vibration), and that the cuff can be removed and replaced by the patient during ambulatory monitoring, for example, to take a shower. The main disadvantage is that such recorders do not work well during physical activity when there may be considerable movement artifact. The oscillometric technique has been used successfully in ambulatory blood pressure monitors and home monitors. It should be pointed out that different brands of oscillometric recorders use different algorithms, and there is no generic oscillometric technique. Comparisons of several different commercial models with intra-arterial and Korotkoff sound measurements, however, have shown generally good agreement. 6, 79 Open in a separate window Fig. 1 Changes occurring distal to a sphygmomanometer cuff during deflation. Upper trace: Korotkoff sounds. Second trace: cuff pressure. Third trace: oscillations in cuff pressure. The maximal oscillation occurs at a pressure of 108 mm Hg, the mean arterial pressure. Bottom trace: radial pulse. From Pickering TG. Blood pressure variability and ambulatory monitoring. Curr Opin Nephrol Hypertens 1993a;2:380; with permission Ultrasound techniques Devices incorporating this technique use an ultrasound transmitter and receiver placed over the brachial artery under a sphygmomanometer cuff. As the cuff is deflated, the movement of the arterial wall at systolic pressure causes a Doppler phase shift in the reflected ultrasound, and diastolic pressure is recorded as the point at which diminution of arterial motion occurs. Another variation of this method detects the onset of blood flow at systolic pressure, which has been found to be of particular value for measuring pressure in infants and children.

18 In patients with very faint Korotkoff sounds (for example those with muscular atrophy) placing a Doppler probe over the brachial artery may help to detect the systolic pressure, and the same technique can be used for measuring the ankle-brachial index, in which the systolic pressures in the brachial artery and the posterior tibial artery are compared, to obtain an index of peripheral arterial disease. The finger cuff method of Penaz This interesting method was first developed by Penaz 63 and works on the principle of the “unloaded arterial wall.” Arterial pulsation in a finger is detected by a photo-plethysmograph under a pressure cuff. The output of the plethysmograph is used to drive a servo-loop, which rapidly changes the cuff pressure to keep the output constant, so that the artery is held in a partially opened state. The oscillations of pressure in the cuff are measured and have been found to resemble the intra-arterial pressure wave in most subjects ( Fig. 2 ). This method gives an accurate estimate of the changes of systolic and diastolic pressure when compared to brachial artery pressures; 63 the cuff can be kept inflated for up to 2 hours. It is now commercially available as the Finometer and Portapres recorders and has been validated in several studies against intra-arterial pressures. 61, 84 The Portapres enables readings to be taken over 24 hours while the subjects are ambulatory, although it is somewhat cumbersome. 27 Open in a separate window Fig. 2 Recording of systolic pressure during laboratory stress testing, made simultaneously with a continuous beat-to-beat monitor (Finapres) and an intermittent oscillometric device (Colin). Technical issues with measurement from the arm There are important potential sources of error with measurements from the upper arm, which are discussed in the following sections.

Effects of posture There is no consensus as to whether blood pressure should be routinely measured while seated or supine, although most guidelines recommend sitting. 67, 72 In a survey of 245 subjects of different ages, Netea et al found that systolic pressures were the same in both positions, but there was a systematic age-related discrepancy for diastolic pressure such that at the age of 30 the sitting diastolic was about 10 mm Hg higher than the supine reading, whereas at the age of 70 the difference was only 2 mm Hg. 49 Body position Blood pressure measurements are also influenced by the position of the arm. 45, 47, 48, 94 As shown in Fig. 3, there is a progressive increase in the pressure of about 5 to 6 mm Hg as the arm is moved down from the horizontal to vertical position. These changes are exactly what would be expected from the changes of hydrostatic pressure. It is also important that the patient’s back be supported during the measurement; if the patient is sitting bolt upright the diastolic pressure may be up to 6.5 mm Hg higher than if sitting back. 14 Open in a separate window Fig. 3 The effects of varying arm position on blood pressure recorded from the brachial artery. Curr Opin Nephrol Hypertens 1993a;2:380; with permission. Cuff-inflation hypertension Although in most patients the act of inflating a sphygmomanometer cuff does not itself change the blood pressure, as shown by intra-arterial 62 and Finapres 87 recordings, in occasional patients there may be a transient but substantial increase of up to 40 mm Hg coinciding with cuff inflation. 42 This condition appears to be distinct from white coat hypertension, in which the increase in pressure both precedes the act of inflation and outlasts it. It should also be differentiated from the transient increase of blood pressure that occurs during self-measurement, due to the muscular act of inflating the cuff. Cuff size The size of the cuff relative to the diameter of the arm is critical.

The most common mistake is to use a cuff that is too small, which will result in an overestimation of the pressure. 33, 40, 86 In general, this error can be reduced by using a large adult sized cuff for all except the skinniest arms. The British Hypertension Society (BHS) recommends that if the arm circumference exceeds 33 cm, a large adult cuff should be used (width 12.5 to 13 cm, length 35 cm). 67 In the United States, the most widely advocated protocol for the selection of the appropriate cuff size is the one recommended by the American Heart Association, 64 shown in Table 1. The two most widely used have been developed by the BHS 52 and Association for the Advancement of Medical Instrumentation (AAMI) in the United States. 2 Both require the taking of three blood pressure readings in 85 subjects (chosen to have a variety of ages and blood pressures) by trained observers and the device being tested. The BHS protocol requires that a device must give at least 50% of readings within 5 mm Hg and 75% within 10 mm Hg with the two methods (grade B), and the AAMI requires that the average difference between the two methods not exceed 5 mm Hg with a standard deviation of less than 8 mm Hg. One of the limitations of the validation procedures is that they analyze the data on a population basis and pay no attention to individual factors. Thus, it is possible that a monitor will pass the validation criteria and still be consistently in error in a substantial number of individuals. 23 Devices for clinic and hospital measurement Mercury sphygmomanometers The design of mercury sphygmomanometers has changed little over the past 50 years, except that modern versions are less likely to spill mercury if dropped. To date, mercury devices have largely being phased out in US hospitals. 43 The reason is not because any more accurate device has been developed but because of concerns about the safety of mercury.

Currently the two alternatives for replacement of mercury are aneroid sphygmomanometer and electronic (oscillometric) devices. Aneroid devices The ban on mercury sphygmomanometer has placed new interest in alternative methods, of which aneroid devices are the leading contenders. The error rates reported with regards to accuracy of aneroid devices in older hospital surveys range from 1% in one survey, 8 to 44% in another. 44 Validation studies conducted a decade ago indicated that they could be accurate. 4, 96 A most recent study, which compared the use of mercury versus aneroid device in the setting of a large clinical trial across over 20 clinical sites, also found it to be accurate. 36 This is the best evidence yet attesting to the accuracy of aneroid devices. Sources of error with the auscultatory method Some of the major causes of a discrepancy between the conventional clinical measurement of blood pressure and the true blood pressure are listed in Table 2. The measurement of blood pressure typically involves an interaction between the patient and the physician (or whoever is taking the reading), and factors related to both may lead to a tendency to either overestimate or underestimate the true blood pressure or to act as a source of bi-directional error. As shown in Table 2, there may be activities that precede or accompany the measurement that make it unrepresentative of the patient’s “true” pressure. These include exercise and smoking before the measurement as well as talking during it. Recent studies indicate that the mechanisms underlying the white coat effect may include anxiety, a hyperactive alerting response, or a conditioned response 29, 55 In one of these studies, we assessed office blood pressure, ambulatory blood pressure, and anxiety scores on three separate occasions one month apart in 238 patients.

We found the largest white coat effect occurred in the physician’s presence, and the noted white coat effect was a conditioned response to the medical environment and the physician’s presence rather than a function of the patients’ trait anxiety level (See Figure 4 ). The white coat effect is seen to a greater or lesser extent in most if not all hypertensive patients but is much smaller or absent in normotensive individuals. It usually has been defined as the difference between the clinic and daytime ambulatory pressure. 91 A closely linked but discrete entity is white coat hypertension, which refers to a subset of patients who are hypertensive according to their clinic blood pressures but normotensive at other times. Thus, white coat hypertension is a measure of blood pressure levels, whereas the white coat effect is a measure of blood pressure change. Open in a separate window Fig. 4 Self-rated anxiety score before (pre) and after (post) BP (BP) measurement in different conditions. On day 1, the research assistant (RA) measured BP outside the medical environment using a mercury sphygmomanometer (SPH). On day 2, the RA measured BP in the absence of a physician (MD) by manually triggering a device for ambulatory BP measurement (MTD) first in the waiting room and next in the examination before and after the MD measured BP using SPH. Anxiety scores were obtained in normotensive subjects (NT) and in patients with white coat hypertension (WC-HT), masked hypertension (M-HT), and sustained hypertension (S-HT). Reproduced with permission from Ogedegbe G, Pickering TG, Clemow L, et al. The misdiagnosis of hypertension: the role of patient anxiety. What distinguishes patients with white coat hypertension from those with true or sustained hypertension is not that they have an exaggerated white coat effect but that their blood pressure is within the normal range when they are outside the clinic setting.

White coat hypertension is important clinically because it appears to be a relatively low-risk condition compared to sustained hypertension (defined by an elevated blood pressure in both the clinic and ambulatory settings). 19 It can only be diagnosed reliably by ambulatory monitoring and home self-monitoring as described later. Observer error and observer bias are important sources of error when sphygmomanometers are used. Differences of auditory acuity between observers may lead to consistent errors, and digit preference is very common, with most observers recording a disproportionate number of readings ending in 5 or 0. 60 An example is shown in Fig. 5 of readings taken by hypertension specialists, who are clearly not immune to this error. The average values of blood pressure recorded by trained individual observers have been found to vary by as much as 5 to l0 mm Hg. 17 The level of pressure that is recorded may also be profoundly influenced by behavioral factors related to the effects of the observer on the subject, the best known of which is the presence of a physician. It has been known for more than 40 years that blood pressures recorded by a physician can be as much as 30 mm Hg higher than pressures taken by the patient at home, using the same technique and in the same posture. 3 Physicians also record higher pressures than nurses or technicians. 37, 73 Other factors that influence the pressure that is recorded may include both the race and sex of the observer. 12, 41 Open in a separate window Fig. 5 The percentage of terminal digits chosen by four physicians in a Hypertension Clinic during routine blood pressure measurement. Auscultatory gap This can be defined as the loss and reappearance of Korotkoff sounds that occur between systolic and diastolic pressures during cuff deflation in the absence of cardiac arrhythmias. Thus, if its presence is not recognized, it may lead to the registration of spuriously high diastolic or low systolic pressures.

It may occur either because of phasic changes of arterial pressure or in patients who have faint Korotkoff sounds ( Fig. 6 ). The auscultatory gap may pose a problem for automatic recorders, which operate by the Korotkoff sound technique, and result in gross errors in the measurement of diastolic pressure. 26 Oscillometric devices are less susceptible to this problem. 26 Its presence is of clinical significance, because it is associated with an increased prevalence of target organ damage. 9 Open in a separate window Fig. 6 The phenomenon of the auscultatory gap during cuff deflation. Upper trace: ECG. Second trace: low frequency recording of sounds under the sphygmomanometer cuff. Third trace: Korotkoff sounds. Fourth trace: auscultatory marker pressed when systolic and diastolic sounds were heard. Fifth trace: cuff pressure. Sixth trace: Finapres recording of arterial pressure; note oscillations of pressure corresponding to silent period of K sounds. Technical sources of error There are also technical sources of error with the auscultatory method, although these are usually fewer when a mercury column is used than when many of the semiautomatic methods are in use (see later). These error sources include the position of the column, which should be at approximately the level of the heart. The mercury should read zero when no pressure is applied, and it should fall freely when the pressure is reduced (this may not occur if the mercury is not clean or if the pin-hole connecting the mercury column to the atmosphere is blocked). With aneroid meters, it is essential that they be checked against a mercury column both at zero pressure and when pressure is applied to the cuff. Surveys of such devices used in clinical practice frequently have shown them to be inaccurate. 7 Electronic monitors for self-monitoring of blood pressure When home monitoring was first used, most studies used aneroid sphygmomanometers.

34 More recently however, automatic electronic devices have become more popular. A Gallup poll conducted in 2005 indicated an increase in the number of patients monitoring their blood pressure at home from 38% in 2000 to 55% in 2005. Similarly the proportion of patients owning a monitor increased from 49% in 2000 to 64% in 2005. 74 The standard type of monitor for home use is now an oscillometric device that records pressure from the brachial artery. These have the advantage of being easy to use, because cuff placement is not as critical as with devices that use a Korotkoff sound microphone, and the oscillometric method has in practice been found to be as reliable as the Korotkoff sound method. The early versions were mostly inaccurate 85 but the currently available ones are often satisfactory. 22, 53 The advantages of electronic monitors have begun to be appreciated by epidemiologists, 13 who have always been greatly concerned about the accuracy of clinical blood pressure measurement and have paid much attention to the problems of observer error, digit preference, and the other aforementioned causes of inaccuracy. Cooper et al have made the case that the ease of use of the electronic devices and the relative insensitivity to whom is actually taking the reading can outweigh any inherent inaccuracy compared to the traditional sphygmomanometer method. 13 Patients should be advised to use only monitors that have been validated for accuracy and reliability according to standard international testing protocols. Unfortunately, only a few of the devices that are currently on the market has been subjected to proper validation tests, such as the AAMI and BHS. An up-to-date list of validated monitors is available on the Dabl Educational Web site ( ) and the British Hypertension Society Web site ( ). Wrist monitors These monitors have the advantages of being smaller than the arm devices and can be used in obese people, as the wrist diameter is little affected by obesity.

A potential problem with wrist monitors is the systematic error introduced by the hydrostatic effect of differences in the position of the wrist relative to the heart, 45 as shown in Fig. 7. This can be avoided if the wrist is always at heart level when the readings are taken, but there is no way of knowing retrospectively whether this was complied with when a series of readings are reviewed. Wrist monitors have potential but need to be evaluated further. 16, 95 Open in a separate window Fig. 7 The effects of changes in the position of the forearm on the blood pressure recorded by a wrist monitor. Ten readings were taken in each of three positions: vertically down, horizontal, and vertically up. The average values are shown at the top of each bar. Finger monitors Although these monitors are convenient, they have so far been found to be inaccurate and therefore should not be used. 74 Ambulatory monitors First developed almost 40 years ago, ambulatory blood pressure monitoring is only now beginning to find acceptance as a clinically useful technique. Recent technologic advances have led to the introduction of monitors that are small and relatively quiet and that can take up to 100 readings of blood pressure over 24 hours while patients go about their normal activities. They are reasonably accurate while the patient is at rest but less so during physical activity. When last systematically surveyed (in 2001), only 24 had been validated according to the AAMI or BHS criteria, of which only 16 satisfied the criteria for accuracy 53 Now many more monitors have been validated and an updated list can be found on the Dabl Educational Web site ( ). They can in theory provide information about the three main measures of blood pressure: the average level, the diurnal variation, and short-term variability.

Recordings in hypertensive patients show that in most patients the average ambulatory pressure is lower than the clinic pressure, and in some cases it may be within the normal range, leading to a diagnosis of white coat hypertension, described later. Given that there is a discrepancy between the clinic and ambulatory pressure, it is reasonable to suppose that the prediction of risk will be different. There are now more than 30 cross-sectional studies relating the extent of cardiovascular damage to both clinic and ambulatory pressures. 68 Almost all have shown that the correlation coefficients are higher for ambulatory pressure, although in many instances the differences were small. The superiority of ambulatory pressure in this respect may be attributed at least in part to the greater number of readings and to their more representative nature. Measurement in different situations Clinic measurement The recent interest in alternative methods of measuring blood pressure has served to emphasize some of the potentially correctable deficiencies of the routine clinic measurement of blood pressure. By increasing the number of readings taken per visit and the number of visits as well as by attempting to eliminate sources of error such as digit preference, the reliability of clinic pressure for estimating the true blood pressure and its consequences can be greatly increased. Despite this, it must be remembered that there are a substantial number of subjects with white coat hypertension in whom clinic readings will continue to give unrepresentative values, no matter how many measurements are taken. Surveys of the techniques used by physicians and nurses in actual practice make depressing reading. One performed in a teaching hospital found that not one out of 172 workers followed the American Heart Association guidelines for measuring blood pressure in the clinic setting.

Although 68% considered the mercury sphygmomanometer to be the most accurate, only 38% chose to use it when given a choice, and 60% were judged to be taking blood pressure inaccurately. 93 Self-measurement The potential advantages of having patients take their own blood pressure are twofold: the distortion produced by the white coat effect is eliminated, and multiple readings can be taken over prolonged periods. Self-measurement of blood pressure at home has been shown to be useful in predicting target organ damage, cardiovascular events and mortality. 74 Five prospective studies have compared the prediction of morbid events with the use of both conventional office and home blood pressure. Three were based on population samples, and 2 recruited hypertensive patients. Four studies found that home BP was the stronger predictor of risk. The concern about the potential for observer error than with physician readings can often be mitigated by use of automated devices with memory chips. These allow the physician to recall the blood pressure readings taken by their patients. Whereas exclusive reliance on self-monitored readings is not recommended, they can provide a useful adjunct to clinic readings, both for the initial evaluation of newly diagnosed patients and for monitoring their response to treatment. Ambulatory blood pressure monitoring There are six prospective studies to date showing that ambulatory blood pressure is a better predictor of risk than clinic pressure and more are on the way. The first, published by Perloff et al., 65, 66 used noninvasive monitoring performed during the day only and reported that those whose ambulatory pressure was low in relation to their clinic pressure were at lower risk of morbidity. The second, by Verdecchia et al., 90 followed a group of 1187 normotensive and hypertensive individuals for 3 years; hypertensive subjects were classified as having white coat or sustained hypertension. The morbid event rate was 0.