το ιεθνές Πρωτόκολλο Αξιολόγησης για συσκευές µέτρησης της αρτηριακής πίεσης σε ενήλικες.

The Accoson Greenlight 300t, the first non-automated mercury-free blood pressure measurement device to pass the International Protocol for blood pressure measuring devices in adults Το Accoson Greenlight 300t αποτελεί την πρώτη ηλεκτρονική συσκευή για µη-αυτόµατη ακροαστική µέτρηση της αρτηριακής πίεσης που έχει περάσει µε επιτυχία το ιεθνές Πρωτόκολλο Αξιολόγησης για συσκευές µέτρησης της αρτηριακής πίεσης σε ενήλικες. John W. Gravesa, Mary Tibora, Blaithnead Murtaghb, Lois Kleina and Sheldon G. Shepsa Blood Pressure Monitoring 2004, 9:13 17 Εισαγωγή Η ακριβής µέτρηση της αρτηριακής πίεσης είναι ζωτικής σηµασίας για την αποτελεσµατική φροντίδα των υπερτασικών ασθενών. Το υδραργυρικό πιεσόµετρο αποσύρεται µε ταχείς ρυθµούς από την κλινική πρακτική λόγω επιφυλάξεων σχετικά µε την µόλυνση και επιβάρυνση του περιβάλλοντος. Το πιεσόµετρο Accoson Greenlight 300t αποτελεί την πρώτη συσκευή (χωρίς υδράργυρο) για µη-αυτόµατη ακροαστική µέτρηση της αρτηριακής πίεσης που έχει περάσει µε επιτυχία το ιεθνές Πρωτόκολλο Αξιολόγησης για συσκευές µέτρησης της αρτηριακής πίεσης σε ενήλικες. Μέθοδος Πενήντα-ένας συµµετέχοντες εγγραφήκαν για να γίνει η επιλογή των 33 που χρειάζονταν για την λήψη τριών ευρών συστολικής (SBP) (χαµηλή 90 129 mmhg, µεσαία 130 160 mmhg, υψηλή 161 180mmHg) και διαστολικής (DBP) (χαµηλή 40 79mmHg, µεσαία 80 100 mmhg, υψηλή 101 130 mmhg) αρτηριακής πίεσης. Πραγµατοποιήθηκαν εννέα συνεχόµενες µετρήσεις αρτηριακής πίεσης από δύο ερευνητές µε το υδραργυρικό µανόµετρο και από τον υπεύθυνο ερευνητή µε το Greenlight 300t. Οι πρώτες δύο µετρήσεις χρησιµοποιήθηκαν για τον προσδιορισµό των ευρών τη συστολικής και διαστολικής αρτηριακής πίεσης. Οι µετρήσεις κατόπιν αναλύθηκαν σε δύο φάσεις ώστε να προσδιορισθεί εάν η συσκευή πληρεί τις προϋποθέσεις του ιεθνούς πρωτοκόλλου. Αποτελέσµατα Η συσκευή «πέρασε» την Φάση 1 χρησιµοποιώντας 15 συµµετέχοντες. Στην Φάση 2.1 (n = 33) από τις 99 µετρήσεις οι 84 στις 99 κυµαίνονταν εντός 5 mmhg, οι 95 στις 99 εντός 10 mmhg και οι 98 στις 99 εντός 15 mmhg. Για τις 99 µετρήσεις της DBP ( ιαστολικής), 74 στις 99 ήταν εντός 5 mmhg, 90 στις 99 ήταν εντός 10 mmhg και 96 στις 99 ήταν εντός 15 mmhg. Στην Φάση Phase 2.2 (n = 33) για την SBP (Συστολική), 33 στους 33 είχαν 2 στις 3 µετρήσεις της SBP

εντός 5mmHg ενώ κανείς δεν είχε και τις τρεις µετρήσεις > 5 mmhg. Για την DBP, 27 στους 33 είχαν 2 στις 3 µετρήσεις της DBP εντός 5mmHg και µόνο τρεις είχαν και τις τρεις µετρήσεις > 5 mmhg. Συµπεράσµατα Η συσκευή Accoson Greenlight 300t αποτελεί την πρώτη ηλεκτρονική συσκευή για µη-αυτόµατη ακροαστική µέτρηση της αρτηριακής πίεσης που έχει περάσει µε επιτυχία το ιεθνές Πρωτόκολλο Αξιολόγησης για συσκευές µέτρησης της αρτηριακής πίεσης σε ενήλικες. Introduction The standard for blood pressure determination in clinical medicine for more than 100 years has been the Riva-Rocci mercury column blood pressure measurement device using the auscultatory technique as described by the American Heart Association (AHA) [1] and World Health Organization (WHO) [2] guidelines. Over the last 20 years, there has been an increasing concern about environmental mercury and human toxicity [3]. This has led many hospitals and clinics to remove the mercury sphygmomanometer from clinical practice [4]. There have been controversies [5,6] about its removal, but the mercury sphygmomanometer seems destined to follow the mercury thermometer out of clinical practice. Two options are present, aneroid manometers for auscultatory blood pressure measurement and automated blood pressure monitors using the oscillometric technique to measure blood pressure. The aneroid blood pressure device has had its detractors [7 9]; but more recently Canzanello et al. [10] have shown that aneroid devices can be reliable but at the expense of an ongoing validation, maintenance, and replacement program. The only aneroid device known to have passed an accepted validation protocol is the Maxi Stabil 3 [11]. More than 23 automated oscillometric devices have passed protocols [Association for the Advancement of Medical Instruments (AAMI) [12], British Hypertension Society (BHS) [13], and International Protocol [14]], showing that these devices meet minimum standards for accurate blood pressure measurement. These automated devices do not function well in patients with arrhythmias [15] and have not been well tested in important subpopulations of patients such as the elderly, dialysis patients, and patients with reduced vascular elasticity such as diabetics. For these reasons, many hypertension experts are looking for an accurate non-mercury auscultatory device to replace their mercury manometers in clinical practice. The objective of this study is to determine whether the Greenlight 300t is an accurate replacement for the mercury manometer in auscultatory blood pressure measurement using passage of the International Protocol as a valid test of device performance.

Methods Fifty-one subjects were evaluated to obtain the 33 subjects required to fill the 11 subjects in each of the three blood pressure ranges for systolic (90 129, 130 160, and 161 180mmHg) and diastolic (40 79, 80 100, 101 130mmHg) blood pressures defined by the International Protocol for validating blood pressure devices in adults [14]. Subjects were recruited from amongst the patients and staff of the Hypertension Division at the Mayo Clinic, Rochester, Minnesota, USA. Each subject was introduced to the three observers and verbal informed consent was obtained and recorded in the Mayo Clinic electronic medical record. After obtaining informed consent, arm circumference, gender, date of birth, and current date and time were noted. After 10 min of relaxation, nine sequential same arm blood pressures were performed in the following fashion. Blood pressure A (BPA) was the initial (entry) blood pressure taken by observers with the mercury manometer using a Y-piece connection for simultaneous readings. The third observer then took a confirmatory reading B (BPB) using the Greenlight device for study entry. The mean values of the first two observer blood pressures were used to characterize the subject into low, medium, and high range for systolic blood pressure (SBP) and diastolic blood pressure (DBP). The two observers then performed simultaneous blood pressure measurements with the mercury manometer, alternating with the supervisor performing blood pressure measurements with the Greenlight 300t device, until four paired observer and three supervisor readings for SBP and DBP had been obtained. Analysis For assessment of accuracy, only measurements BP1 to BP7 are used. The mean of each pair of observer measurements is calculated; this is denoted as observer measurement BP1, BP3, BP5, or BP7. Each device measurement is flanked by two of these observer measurements, and one of these must be selected as the comparative measurement. From these, further measurements are derived as follows: The differences BP2-BP1, BP2-BP3, BP4-BP3, BP4-BP5, BP6-BP5, BP6-BP7 are calculated. The absolute values of the differences are calculated (i.e, the signs are ignored). These are paired according to the device reading. If the values in a pair are unequal, the observer measurement corresponding to

the smaller difference is used. If the values in a pair are equal, the first of the two observer measurements is used. When this has been completed, there are three device readings for SBP and three for DBP for each subject. Each of these six readings has a single corresponding observer measurement, a difference between the two and a band for that difference as described above. Assessment of Phase 1 Once there are five subjects in each of the six blood pressure ranges (Table 1), recruitment should be stopped and assessment performed. Data from only the first five subjects in each range are used. (In filling these ranges, some ranges may be oversubscribed because of subjects having different SBP and DBP ranges.) This will yield 45 sets of measurements for both SBP and DBP. Passage of Phase 1 requires that at least one of the following three conditions are met: (1) at least 25 of the 45 Greenlight device readings in Phase 1 are within 5mmHg of the mercury standard, or (2) that 35 of 45 readings are within 10mm Hg or (3) that 40 of the 45 readings are within15mmhg of the mercury standard readings. Assessment of Phase 2 This phase determines how accurate the device will be for individual measurements (Phase 2.1). and for individual subjects (Phase 2.2) by determining the number of differences within 5, 10, and 15mmHg and then determining accuracy. For individual measurements for the Greenlight device to pass, there must be a minimum of 60, 75 and 90 measurements falling within 5, 10, and 15mmHg respectively. Furthermore, there must be a minimum of either 65 comparisons within 5mmHg and 80 within 10mmHg or 65 comparisons within 5mmHg and 95 comparisons within 15 mmhg. In Phase 2.2 (subjects comparisons), at least 22 of 33 subjects must have at least two of their three comparisons lying within 5mmHg. At most, three of the 33 subjects can have all three of their comparisons over 5mmHg apart. After all ranges have been filled, there will be 99 sets of measurements for both SBP and DBP, then: The number of differences in each zone as described above is calculated.

A pass/fail grade for Phase 2.1 is determined according to the criteria described above. For each of the 33 subjects, the number of measurements falling within 5mmHg is determined. A pass/fail recommendation for Phase 2.2 is determined according to the criteria outlined above. If the device passes both the Phase 2.1 and Phase 2.2, it passes the validation and can be recommended for clinical use. If it does not, it fails and is not recommended for clinical use. Results Fifty-one subjects were enrolled to obtain the 33 subjects to fill the 11 subjects needed for each of the categories of low, medium, and high for systolic and diastolic blood pressure. The demographic results for the 33 subjects are seen in Table 2. For subjects used to evaluate the accuracy of SBP measurement by the Greenlight 300t device, their mean age was 55.8 ± 16.1 (range: 34 80) years, arm circumference was 29.3 ± 4.8 (range: 18 42) cm, entry SBP was 142.4 ± 25.8 (range: 95 176) mmhg, and entry DBP was 82.3 ± 18.0 (range: 51 113) mmhg. For subjects used to evaluate the accuracy of the device for DBP at study entry, their mean age was 55.3 ± 16.3 (range: 34 90) years, mean arm circumference was 30.3 ± 5.1 (range: 18 42) cm, entry SBP was 149.4 ± 23.9 (range: 95 204) mmhg, and entry DBP was 88.0 ± 21.2 (range: 51 125) mmhg. Systolic BP subjects included 15 males and 18 females. Eight (24%) used the small cuff, 18 (55%) used the standard adult cuff, and seven (21%) used the large adult cuff. For DBP subjects, there were 19 males and 14 females. Six (18%) used the small cuff, 17 (52%) used the standard adult cuff, and 10 (30%) used the large adult cuff. Bland Altman plots for agreement of the two methods in determining SBP (Figure 1) and DBP (Figure 2) showed good agreement between the mercury manometer and the Greenlight 300t. The Greenlight 300t successfully fulfilled the International Protocol requirements in Phase 1 (Table 2) and in Phase 2.1 and 2.2 (Table 3). Discussion Accurate blood pressure measurement is critical to the diagnosis and treatment of hypertension. Auscultatory blood pressure measurement to standards described by the American Heart Association [1] and the WHO/International Society of Hypertension [2] using the Riva-Rocci mercury column device remains the preferred method of blood

pressure determination in clinical medicine. Mercury, however, is a very toxic substance [3] and due to increasing concern about environmental contamination, many are calling for the removal of the mercury manometer from clinical practice [4,5]. The American Heart Association has questioned the removal of the mercury manometer from practice [6] prior to having a satisfactory device to replace mercury for auscultatory blood pressure measurement. For auscultation blood pressure measurement, the only substitute for mercury is the aneroid sphygmomanometer. Its accuracy and reliability is felt to be far worse than the mercury manometer [7 9]. Canzanello et al. [10] has found the aneroid manometer accurate if subjected to rigorous protocol of surveillance and maintenance, which unfortunately is unlikely to be applicable to general practice circumstances. In addition, we know of only one aneroid measurement device, the Maxi Stabil 3, that has passed a recognized validation protocol [11].

The second option for replacement of the mercury sphygmomanometer is to withdraw from auscultatory blood pressure measurement and rely on automated blood pressure measurement using the oscillometric technique. There are many oscillometric devices that have passed the previously used validation studies from AAMI [12] and BHS [13]. These devices reduce observer-related errors such as inappropriately rapid deflation rate, digit bias, and the subjective difficulty in determination of phase 4 5 sounds for DBP [15]. Oscillometric devices have not been embraced by the hypertension community due to concerns about their reliability in arrhythmias and in certain patient subgroups with reduced arterial compliance such as the elderly, diabetic, and the dialysis patient where the oscillometric technique theoretically may be insufficiently accurate [16,17]. In this study, the Greenlight 300t has passed the International Protocol demonstrating that it provides accuracy comparable to the mercury manometer in auscultatory blood pressure measurement. Substitution of the Greenlight 300t for the standard mercury manometer in clinical practice offers many advantages. First, the use of auscultatory blood pressure measurements is preserved using an accurate mercury replacement, fulfilling the desire expressed by a consensus of experts representing the AHA [6]. The Greenlight 300t also offers the potential to improve auscultatory blood pressure measurement. It has a self-zeroing feature for the entire range of blood pressure, thus obviating the surveillance protocol required to ensure accuracy of the aneroid blood pressure measurement device [10]. As it has been demonstrated that many practitioners never validate or calibrate their office devices [18], this offers a significant quality improvement in blood pressure measurement. The Greenlight 300t represents each number from 0 300 with an LED diode. This reduces the impact of observer error inherent in the moving meniscus (mercury manometer) or needle swing (aneroid manometer) in auscultatory blood pressure measurement. Finally, the Greenlight 300t has a deflation rate vernier display. The vernier provides important feedback to the observer about following the correct rate of cuff deflation. King et al. [18] have shown that the Korotkoff sounds were less intense when the cuff is inflated and deflated too slowly and on some occasions they were completely inaudible. This was caused by venous congestion induced by blocking venous return, which attenuates the intensity of the Korotkoff sounds and increases the likelihood of an inaccurate blood pressure determination [18]. Thulin et al. [19] also described the finding that too rapid a deflation rate resulted in a falsely low systolic and falsely high diastolic blood pressure. Thus, the Greenlight 300t vernier

display of correct deflation rate, if used by the standard observer, should enhance the quality of blood pressure measurement over the usual mercury column or aneroid devices. Mercury is clearly a toxic substance and its presence in the environment needs to be minimized. The presence of the Greenlight 300t should allow the mercury sphygmomanometer to be removed from clinical practice as the mercury thermometer has been replaced with its electronic counterpart. The Greenlight 300t has passed the International Protocol for blood pressure device validation in adults. It is the first device to fulfill the AHA experts quest for a reliable replacement for the mercury manometer in auscultatory blood pressure measurement. References 1 Perloff D, Grim C, Flack J, Frohlich E, Hill M, McDonald M, et al. Special report: human blood pressure determination by sphygmomanometry. Circulation 1993; 88:2460 2470. 2 Guidelines Subcommittee. 1999 World Health Organization International Society of Hypertension guidelines for the management of hypertension. J Hypertens 1999; 17:151 183. 3 US Environmental Protection Agency. Mercury Study Report to Congress, Volume I Executive Summary. Washington, DC: Environmental Protection Agency; 1997. Publication EPA-452/R-97-003. 4 Hospitals for a Healthy Environment. Mercury. Available at: http://www.h2eonline. org/tools/mercury.htm. Accessibility verified January 10, 2003. 5 O Brien E, Waeber B, Parati G, Staessen G, Myers MG. Blood pressure measuring devices: recommendations of the European Society of Hypertension. BMJ 2001; 322:531 536. 6 Jones DW, Frohlich ED, Grim CM, Grim CE, Taubert KA. Mercury sphygmomanometers should not be abandoned: an advisory statement from the Council for High Blood Pressure Research, American Heart Association. Hypertension 2001; 37:185 186. 7 Bailey RH, Knaus VL, Bauer JH. Aneroid sphygmomanometers. An assessment of accuracy at a university hospital and clinics. Arch Intern Med 1991; 151:1409 1412.

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Influence of rate of cuff inflation and deflation on observed blood pressure by sphygmomanometry. Am Heart J 1963; 65: 303 306. 19 Thulin T, Schersten B, Andersson G. Measurement of blood pressure-a routine test in need of standardization. Postgrad Med J 1975; 51: 390 395.