Clinical evaluation of the oscillometric blood pressure monitor in adults and children based on the 1992 AAMI SP-10 standards

Objective and Methods. A noninvasive blood pressure monitor (model BP8800MS, Colin Medical Instruments Corp., San Antonio, TX) that uses the oscillometric principle was evaluated against the manual auscultatory method in 85 adults and 85 children following the requirements of the 1992 AAMI SP-10 standard. This was the first evaluation study of the electronic sphygmomanometers according to the new AAMI standards.Results. In adult subjects, the mean difference and standard deviation of the differences between the oscillometric and auscultatory methods were 2.81 ± 5.35 mm Hg (mean ± SD) for systolic and 0.04 ± 4.90 mm Hg for diastolic; in children, they were 3.18 ± 5.96 mm Hg for systolic and –0.82 ± 5.24 mm Hg for diastolic. Excellent correlation between the oscillometric and auscultatory methods, particularly the diastolic pressure, is due to usage of the Phase V Korotkoff's sounds for auscultatory detection of the diastolic pressure, increased accuracy of the two observers' measurements, and proper selection of cuff sizes depending on the mid-arm circumference. Five different-sized cuffs were used in this study. The cuff-width-to-midarm circumference ratio was adjusted to be 0.4 or larger to minimize the measurement error associated with mismatch of cuff-size/arm-size relationship. The distribution of errors associated with each cuff was nearly the same.Conclusions. The 1992 AAMI SP-10 standards offer a thorough evaluation of the oscillometric sphygmomanometer by enforcing more stringent criteria on (1) agreement between two observers, (2) wide spectrum of blood pressure from hypertensive (above 180 mm Hg) to hypotensive, and (3) data analysis. The oscillometric blood pressure monitor evaluated in this study meets the specifications of the new AAMI SP-10 standards and can offer an accurate, automatic, and noninvasive measure of both systolic and diastolic blood pressure in adults and children. It can safely replace the manual or automatic auscultatory system in various clinical settings.This study was supported in part by a grant in aide from Nippon Colin (Komaki, Japan) and Colin Medical Instruments (San Antonio, TX). The authors acknowledge Dr. James Pool and Ms. Charlyne Allston-Wright of the Department of Medicine, Baylor College of Medicine, for providing hypertensive subjects. Technical assistance by Ms. Julie Glueck of the Department of Surgery, Baylor College of Medicine, is also acknowledged.     

Biases in the measurement of arterial pressure

We compared cuff to simultaneous direct intra-arterial pressure in 26 seriously ill patients, in order to: test the accuracy of oscillometric and auscultatory estimates of direct systolic pressure; test muffling and disappearance of sound as indices of direct diastolic pressure; gain insight into the timing of the different phases of Korotkoff sounds; and assess the local and general effects of cuff inflation on blood pressure. We found that conventional estimation of systolic blood pressure by auscultation of the first Korotkoff sound (K1) underestimates direct systolic pressure by an average of 16 to 17 mm Hg. Oscillometric pressure measurement provides a significantly better estimate than K1 but still underestimates by 7 to 8 mm Hg. These systolic cuff measurements are biased downward from direct values because of local cuff effect and cuff error. Diastolic cuff measurements deviate from direct values primarily because of a local cuff effect which produces an upward bias of 5 mm Hg at the point of sound muffling (K4), and 3 mm Hg at the point where sounds disappear (K5). We recommend oscillometric measurement of systolic pressure and K5 measurement of diastolic pressure as the best indirect estimates of blood pressure in critically ill patients.     

The effect of cuff pressure deflation rate on accuracy in indirect measurement of blood pressure with the auscultatory method

The importance of cuff deflation rate in the auscultatory method of measuring blood pressure was investigated using a computer-based model. To determine the relationship between the cuff deflation rate and the measurement error, two cuff deflation protocols were used, one based on heart rate (mm Hg per heartbeat), the other on a constant rate (mm Hg per second). The different deflation protocols and rates were tested using a constant blood pressure of 120/80 mm Hg and heart rates ranging from 40 to 120 beats/min. It was confirmed that a cuff deflation rate that is time based will introduce larger errors at low heart rates. Using heart rate as a basis for cuff deflation rate yields a constant error that is independent of heart rate. The currently used standard of 3 mm Hg/s could result in a maximum error of 2.5 mm Hg in both systolic and diastolic pressures at a heart rate of 72 beats/min. The maximum systolic and diastolic errors increase to more than 4 mm Hg at 40 beats/min. A deflation rate of 2 mm Hg/beat, however, yields a maximum error of 2 mm Hg for both systolic and diastolic pressures, independent of heart rate. A cuff deflation rate based on heart rate is recommended to help minimize changes in measurement error when measuring blood pressure if a wide range of heart rates will be encountered.Supported by grants from IVAC, San Diego, CA, and Physio Control, Redmond, WA.     

Factors affecting the validity of the standard blood pressure cuff,

Summary. Fifty-eight patients, 31 women and 27 men, with a wide range of upper arm circumferences (20.43 cm), ages (16.82 years) and body mass indices (16.55 kg m^?2) were studied. The direct blood pressure was measured in the brachial artery in one arm and simultaneously the indirect pressure was measured in the other arm using a large standard cuff (rubber bag 12 times 35 cm). The mean intra-arterial blood pressure was (systolic/diastolic) 13725 mmHg (SD)/7610 mmHg. With the cuff the mean blood pressure was 13423 mmHg/85ll mmHg. The cuff significantly underestimated the systolic blood pressure (3.2ll.4 mmHg, range -25–30 mmHg) while the diastolic pressure was overestimated significantly (8.88.5 mmHg, range -32.14 mmHg). The direct/indirect blood pressure difference correlated significantly to the intraarterial systolic and diastolic pressures (systolic/diastolic; r=0.44, P= 0.0006/r=0.36, P= 0.0062), but only to the auscultatory diastolic pressure (r=-0.02, P= 0.9/r= -0.45, P= 0.0004). The direct/indirect difference correlated significantly to the arm circumference (r= -0.33, P= 0.01/r= -0.30, P= 0.02) as did the diastolic direct/indirect difference to pulse rate (r= 0.34, P= 0.009). Age did not correlate significantly to the direct/indirect blood pressure difference in this study (r= -0.02, P= 0.9/r=-0.10, P= 0.5). It can be concluded that in addition to the ratio between the arm circumference and the width of the cuff (rubber bag), there are other sources of systematic errors of indirect blood pressure measurement, in particular pulse rate and the level of indirect blood pressure. If corrections could be made with regard to these variables, it is obvious that the reliability of the indirect method, especially when used in epidemiological contexts, would increase.     

Use of A Neonatal Blood Pressure Cuff to Monitor Blood Pressure In The Adult Finger – Comparison With A Standard Adult Arm Cuff

Background. There are few suitable methods for monitoring blood pressure continously (or intermittently) for research in adult stroke patients, who are ill but do not justify invasive intensive care monitoring. Method. We tested a neonatal arm blood pressure in adults by placing it on the forefinger (finger cuff). We compared the repeatability of the finger cuff with blood pressure measured by a standard adult arm cuff using the oscillometric technique in 168 ambulatory outpatients attending a cerebrovascular disease clinic. Results. The mean difference between sequential mean blood pressure readings with the finger cuff was 0.55 mm Hg (95% confidence interval (CI) –14.36 to 15.47 mm Hg), and for the arm cuff was 3.31 mm Hg (95% CI –23.33 to 16.71 mm Hg). Measurements made with the arm cuff were shown to affect subsequent arm cuff readings made within a few minutes of the first. The mean difference between the finger cuff and arm cuff mean blood pressure readings was 0.03 mm Hg (95% CI –26.07 to 26.14 mm Hg) and agreement was better when the blood pressure was measured with the finger cuff first rather than the arm cuff. However, although there was no difference in the mean blood pressure recordings both systolic and diastolic blood pressure measurements differed systematically between arm and finger cuff. Conclusion. The reproducibility of sequential blood pressure measurements made with the finger cuff was better than with the arm cuff. The performance of the finger cuff compared with that of the arm cuff was sufficiently good to encourage use of the finger cuff in research involving automatic intermittent monitoring to observe sequential blood pressures over time in stroke patients. However, measurements of systolic and diastolic pressure were not the same with the two cuffs and further work on calibration of the finger cuff would be useful.     

Noninvasive blood pressure monitoring from the supraorbital artery using an artificial neural network oscillometric algorithm

Objective. Our objective was to overcome the limitations of linear models of oscillometric blood pressure determination by using a nonlinear technique to model the relationship between the oscillometric envelope and systolic and diastolic blood pressures, and then to use that technique for near-continuous arterial pressure monitoring at the supraorbital artery.Methods. An adhesive pressure pad and transducer were used to collect oscillometric data from the supraorbital artery of 85 subjects. These data were then used to train an artificial neural network (ANN) to report diastolic or systolic pressure. Arterial pressure measurements defined by brachial artery auscultation were used as a reference. ANN results were compared with those obtained using a standard oscillometric algorithm that determined pressures based on fixed percentages of the maximum oscillometric amplitude.Results. The ANN produced better estimates of reference blood pressures than the standard oscillometric algorithm. Mean difference between target and actual output for the ANN was 0.50±5.73 mm Hg for systolic pressures, compared to the mean difference of the standard algorithm of 2.78±19.38 mm Hg. For diastolic pressures, the ANN had a mean difference of 0.04±4.70 mm Hg, while the mean difference of the standard algorithm was –0.34±9.75 mm Hg.Conclusions. The ANN produced a better model of the relationship between the oscillometric envelope and reference systolic and diastolic pressures than did the standard oscillometric algorithm. Noninvasive blood pressure measured from the supraorbital artery agreed with pressure measured by auscultation in the brachial artery, and may sometimes be more clinically useful than an arm cuff device.This research was supported, in part, by a grant from Baxter Healthcare Corporation (Santa Ana, CA), and Innerspace Medical (Irvine, CA). A grant of computer time from the Utah Supercomputer Institute, which is funded by the State of Utah and the IBM Corporation, is gratefully acknowledged.     

Comparison of intraarterial with continuous noninvasive blood pressure measurement in postoperative pediatric patients

Objective. The purpose of this study was to estimate the accuracy, bias, and frequency response of continuous blood pressure monitoring using finger photoplethysmography in children.Methods. To compare arterial blood pressure measured using the Finapres device with simultaneously measured intraarterial blood pressure we studied 27 randomly selected postoperative pediatric patients who were receiving a variety of inotropic and vasoactive agents at a cardiac intensive care unit in university-affiliated pediatric hospital.Results. Sixty-two of 66 attempts (94%) to obtain a noninvasive blood pressure measurement were successful. A total of 37,351 paired blood pressure measurements from 53 records were compared, revealing a measurement bias of –18.6 mm Hg for systolic blood pressure and –13.4 mm Hg for diastolic blood pressure. The measurement bias increased proportionately to blood pressure, with systolic and diastolic gains between the noninvasive and intraarterial techniques of 0.86 and 0.75 mm Hg/mm Hg, respectively. The variation bias during each recording epoch, as measured by standard deviation of bias, was low (mean _systolic=2.9 mm Hg; mean _diastolic=2.0 mm Hg). The frequency response between the intraarterial and noninvasive pressure waveforms was flat to 10 Hz and approximately equal to 1.Conclusions. Substantial measurement bias exists between this noninvasive blood pressure measurement technique and intraarterial blood pressure. Measurements of the intrapatient variability and frequency response analysis suggest that the noninvasive technique accurately tracks intraarterial blood pressure over the short term. This technique may have useful applications in settings where intraarterial monitoring is undesirable or unobtainable.Dr Triedman is supported in part by an NIH Training Grant and a Physician-Investigator Fellowship from the Massachusetts Affiliate of the American Heart Association. Dr Saul is supported by a grant from the Whitaker Foundation.     

Intraosseous Pressure Monitoring in Healthy Volunteers

Study Objective: Invasively monitoring blood pressure through the IO device has not been thoroughly demonstrated. This study attempted to establish baseline values of IO pressure in a healthy human population. Methods: This was a prospective, healthy volunteer, observational study. Participants had two IO devices placed (humerus and tibia), and participant IO pressures, vital signs, and pain scores were monitored for up to 60 minutes. Participants were contacted at 24-hours and 7 days post-testing to assess for adverse events. Summary statistics were calculated for systolic, diastolic, and mean humeral and tibial IO pressure. The ratio of IO to non-invasive blood pressure was calculated, and Bland Altman plots were created. The slope (linear) of the mean humeral and the tibial IO pressures were also calculated. Results: Fifteen subjects were enrolled between April and July 2015. Fourteen of 15 humeral IOs were placed successfully (93.3%) and all 15 of the tibial IOs were placed successfully. Mean tibial systolic, diastolic, and mean IO pressure were 55.8 ± 27.9, 49.3 ± 27.1, and 48.4 ± 29.4 mm Hg, respectively. Humeral systolic, diastolic, and mean IO pressure were 32.9 ± 16.0, 27.4 ± 15.2, and 24.5 ± 14.3 mm Hg. The mean tibial IO pressure was 52.5% ± 32.0% of external cuff pressure ratio. The mean humeral IO pressure was 26.5% ± 15.2% of the external mean blood pressure. The Bland Altman plots showed an inconsistent relationship between the systolic and diastolic cuff pressure and the IO pressures. We observed a 1% per minute decrease in IO pressure from the initial placement until the final reading. Conclusions: Intraosseous pressure readings can be obtained in healthy human volunteers. However, absolute IOP values were not consistent between subjects. Future research may determine how IO pressure can be used to guide therapy in ill and injured patients.     

Pitfalls in the diagnosis and management of systolic hypertension

BACKGROUND: Systolic blood pressure (SBP) is even more important than diastolic blood pressure (DBP) with regard to the risk of cardiovascular complications. METHODS AND RESULTS: Pitfalls in the diagnosis of systolic hypertension include the auscultatory gap, use of the proper size cuff (obese adult size for mid-arm circumference >33 cm and child's cuff for mid-arm circumference <23 cm), a "white coat" effect of about 17 mm Hg, regression toward the mean, and a tendency to focus only on hypertension rather than all of the cardiovascular risk factors. Pitfalls in the pharmacologic management of systolic hypertension include being too aggressive with "acute" therapy, too fast in up-titration, too complacent about adverse effects, too unaware of important drug or food interactions, and too content with the achieved level of SBP. CONCLUSION: In treated hypertensives, SBP is typically less well controlled than DBP. Clinicians must not generally be content with partial control of SBP.     

Clinical evaluation of continuous noninvasive blood pressure monitoring: Accuracy and tracking capabilities

A continuous, noninvasive device for blood pressure measurement using pulse transit time has been recently introduced. We compared blood pressure measurements determined using this device with simultaneous invasive blood pressure measurements in 35 patients undergoing general endotracheal anesthesia. Data were analyzed for accuracy and tracking ability of the noninvasive technique, and for frequency of unavailable pressure measurements by each method. A total of 25, 133 measurements of systolic pressure, diastolic pressure, and mean arterial pressure (MAP) by each method were collected for comparison from 35 patients. Accuracy was expressed by reporting mean bias (invasive pressure minus noninvasive pressure) and limits of agreement between the two measurements. After correction for the offset found when measuring invasive and oscillometric methods of arterial pressure measurement, the mean biases for systolic, diastolic, and mean pressures by the pulse wave method were ?0.37 mm Hg, ?0.01 mm Hg, and ?0.05 mm Hg, respectively (p<0.001). The limits of agreement were: ?29.0 to 28.2 mm Hg, ?14.9 to 14.8 mm Hg, and ?19.1 to 19.0 mm Hg, respectively (95% confidence intervals). When blood pressure measured invasively changed over time by more than 10 mm Hg, the noninvasive technique accurately tracked the direction of change 67% of the time. During the entire study, 3.2% of the invasive measurements were unavailable and 12.9% of the noninvasive measurements were unavailable. The continuous noninvasive monitoring technique is not of sufficient accuracy to replace direct invasive measurement of arterial blood pressure, owing to relatively wide limits of agreement between the two methods. The continuous noninvasive method may serve as an intermediate technology between intermittent noninvasive and continuous invasive measurement of blood pressure if tracking capabilities can be improved; but, further refinement is needed before it can be recommended for routine intraoperative use.     

Accuracy of four indirect methods of blood pressure measurement,with hemodynamic correlations

In 38 adults undergoing cardiac surgery, 4 indirect blood pressure techniques were compared with brachial arterial blood pressure at predetermined intervals before and after cardiopulmonary bypass. Indirect blood pressure measurement techniques included automated oscillometry, manual auscultation, visual onset of oscillation (flicker) and return-to-flow methods. Hemodynamic measurements or calculations included heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect and intraarterial blood pressure values were compared by simple linear regression by patient and measurement period. Measurement errors (arterial minus indirect blood pressure) were calculated, and stepwise regression assessed the relationship between measurement error and heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect to intraarterial blood pressure correlation coefficients varied over time, with the strongest correlations often occurring at the first and last measurement periods (preinduction and 60 minutes after cardiopulmonary bypass), particularly for systolic blood pressure. Within-patient correlations between indirect and arterial blood pressure varied widely—they were consistently high or low in some patients. In other patients, correlations were especially weak with a particular indirect blood pressure method for systolic, mean, or diastolic blood pressure; in some cases indirect blood pressure was inadequate for clinical diagnosis of acute blood pressure changes or trends. The mean correlations between indirect and direct blood pressure values were, for systolic blood pressure: 0.69 for oscillometry, 0.77 for auscultation, 0.73 for flicker, and 0.74 for return-to-flow; for mean blood pressure: 0.70 for oscillometry and 0.73 for auscultation; and for diastolic blood pressure: 0.73 for oscillometry and 0.69 for auscultation. The mean measurement errors (arterial minus indirect values) for the individual indirect blood pressure methods were, for systolic: 0 mm Hg for oscillometry, 9 mm Hg for auscultation, -5 mm Hg for flicker, 7 mm Hg for return-to-flow; for mean: -6 mm Hg for oscillometry, and -3 mm Hg for auscultation; and for diastolic: -9 mm Hg for oscillometry and -8 mm Hg for auscultation. Mean measurement error for systolic blood pressure was thus least with automated oscillometry and greatest with manual auscultation, while standard deviations ranging from 9 to 15 mm Hg confirmed the highly variable nature of single indirect blood pressure measurements. Except for oscillometric diastolic blood pressure, a combination of systemic hemodynamics (heart rate, stroke volume index, systemic vascular resistance index, and cardiac index) correlated with each indirect blood pressure measurement error, which suggests that particular numeric ranges of these variables minimize measurement error. This study demonstrates that striking variability occurs in the relationship between indirect and arterial blood pressure measurements, and that the systemic hemodynamic state influences accuracy of indirect blood pressure measurements. When the reproducibility of repeated indirect blood pressure measurements appears unsatisfactory or inconsistent with other clinical observations, clinicians may find that an alternative indirect blood pressure method is a better choice. Of the methods tested, no single indirect blood pressure technique showed precision superior to the others, but two methods yielded data only for systolic pressure. These findings lend support to intraarterial blood pressure measurement in conditions of hemodynamic variability, and suggest the theoretical benefits of continuous indirect blood pressure measurements. Annual meeting of the American Society of Anesthesiologists, New Orleans, LA, Oct 1984.     

Association of Hypertension with Knee Pain Severity Among People with Knee Osteoarthritis

PurposeTo examine the association of hypertension with knee pain severity in individuals with knee osteoarthritis (OA).DesignCross-sectional study of baseline data collected by the Osteoarthritis Initiative.MethodsParticipants with knee OA (N=1,363) were categorized into four groups based on blood pressure (BP): 1) systolic < 120 mm HG and diastolic < 80 mm Hg; 2) 120 ≤ systolic < 130 mm Hg and diastolic < 80 mm Hg; 3) 130 ≤ systolic < 140 mm Hg or 80 ≤ diastolic < 90 mm Hg; 4) systolic ≥ 140 mm Hg or diastolic ≥ 90 mm Hg. OA knee pain severity was measured by Pain subscale of Western Ontario and McMaster Universities Osteoarthritis Index in the past 48 hours, Pain subscale of Knee Injury and Osteoarthritis Outcome Score (KOOS) in the past 7 days, and numeric rating scale (NRS) in the past 30 days. Linear regression was used to examine the relationship between hypertension and knee pain severity.ResultsCompared with the normal BP group, individuals with stage 2 hypertension reported significantly higher OA knee pain severity by KOOS in the past 7 days (β=-2.05 [95% CI -4.09, -0.01], p=0.049) and by NRS in the past 30 days (β=0.31 [95% CI 0.01, 0.62], p=0.045) after adjustments for demographic and medical factors.ConclusionsHypertension was associated with higher OA knee pain severity in individuals with knee OA.Clinical ImplicationsNurses can recommend adjunctive non-pharmacological treatments and adherence strategies to help control hypertension, which may help decrease OA knee pain.     

Determination of blood pressure level and changes in physiological situations: comparison of the standard cuff method with direct intra-arterial recording

Summary. Blood pressure changes during a test series (sitting, supine, standing, bicycle ergometer test, recovery) were determined in a group of normotensive and borderline hypertensive subjects simultaneously with the continuous intra-arterial registration (Oxford method) and the indirect cuff methods. The mean method difference between the direct and indirect method varied considerably in tests, from –2·3 to 12·9 mmHg in systolic pressure and from –4·3 to 18·2 mmHg in diastolic pressure. There was also a large scatter in the method difference between subjects. Analysis of the blood pressure responses to the other tests using values measured in the sitting position as the reference also revealed considerable variation between the methods. The accuracy of the indirect method was also tested by classifying the population in two subgroups along the median (high/low group) in all tests by each method. The classification discrepancy between the methods varied from 9 to 33% in systolic pressure and from 0 to 25% in diastolic pressure. The results indicate that the data gathered using the indirect measuring method from the arterial blood pressure level and changes in varying physiological conditions may differ considerably from direct intra-arterial readings. On the other hand, the repeatability of the indirect method in stabile conditions was found to be acceptable indicating that the indirect method is useful in blood pressure follow-up.     

Clinical Assessment of the Neonatal Dinamap 847 During Anesthesia in Neonates and Infants

Direct measurements of systolic, diastolic, and mean arterial blood pressure and electrocardiogram-derived heart rates were compared with indirect arterial blood pressure measurements using the Dinamap 847XT noninvasive monitor. A total of 260 paired comparisons from 16 patients were analyzed. A regression analysis of paired data over a wide range of blood pressure values gave the following results: for heart rate r = 0.97, for systolic arterial pressure r = 0.84, for mean arterial pressure r = 0.73, and for diastolic arterial pressure r = 0.52. The 95% confidence limits for systolic, mean, and diastolic arterial pressure were ±16 mm Hg, ±18 mm Hg, and ±21 mm Hg, respectively. The Dinamap monitor was found to be an accurate trend recorder of heart rate and blood pressure during anesthesia in neonates and small infants.     

Peripheral vascular effects on auscultatory blood pressure measurement

Experiments were conducted to examine the accuracy of the conventional auscultatory method of blood pressure measurement. The influence of the physiologic state of the vascular system in the forearm distal to the site of Korotkoff sound recording and its impact on the precision of the measured blood pressure is discussed. The peripheral resistance in the arm distal to the cuff was changed noninvasively by heating and cooling effects and by induction of reactive hyperemia. All interventions were preceded by an investigation of their effect on central blood pressure to distinguish local effects from changes in central blood pressure. These interventions were sufficiently moderate to make their effect on central blood pressure, recorded in the other arm, statistically insignificant (i.e., changes in systolic [p<0.3] and diastolic [p<0.02]). Nevertheless, such alterations were found to modify the amplitude of the Korotkoff sound, which can manifest itself as an apparent change in arterial blood pressure that is readily discerned by the human ear. The increase in diastolic pressure for the cooling experiments was statistically significant (p<0.001). Moreover, both measured systolic (p<0.004) and diastolic (p<0.001) pressure decreases during the reactive hyperemia experiments were statistically significant. The findings demonstrate that alteration in vascular state generates perplexing changes in blood pressure, hence confirming experimental observations by earlier investigators as well as predictions by our model studies.Supported in part by NIH grants no. HL 10,330, HL 22,223, and HL 31,480.     

The effect of deep-tissue massage therapy on blood pressure and heart rate

AIM: In the present study, we describe the effects of deep tissue massage on systolic, diastolic, and mean arterial blood pressure. MATERIALS AND METHODS: The study involved 263 volunteers (12% males and 88% females), with an average age of 48.5. Overall muscle spasm/muscle strain was described as either moderate or severe for each patient. Baseline blood pressure and heart rate were measured via an automatic blood pressure cuff. Twenty-one (21) different soothing CDs played in the background as the deep tissue massage was performed over the course of the study. The massages were between 45 and 60 minutes in duration. The data were analyzed using analysis of variance with post-hoc Scheffe's F-test. RESULTS: Results of the present study demonstrated an average systolic pressure reduction of 10.4 mm Hg (p<0.06), a diastolic pressure reduction of 5.3 mm Hg (p<0.04), a mean arterial pressure reduction of 7.0 mm Hg (p<0.47), and an average heart rate reduction of 10.8 beats per minute (p<0.0003), respectively. CONCLUSIONS: Additional scientific research in this area is warranted.     

An evaluation of two indirect methods of blood pressure measurement in ill patients

Direct (intraarterial) and two indirect (using a mercury sphygmomanometer [MS] and an automatic [auscultatory] device) methods of blood pressure measurement were compared in intensive care patients (N = 32). One trained observer blind to both automatic and direct measurements obtained all indirect MS measurements. All direct and indirect measurements were made on the same arm. Direct measurements were obtained from 10-second strip chart recordings. In normotensive patients both indirect measurements of systolic blood pressure (SBP) underestimated the direct SBP; however, only the SBP value obtained with the automatic device (106 mm Hg) was significantly different, p less than .05, from the direct SBP value (120 mm Hg). No significant difference was noted between methods in measurement of normotensive diastolic blood pressure. In hypertensive patients direct SBP was significantly greater, p less than .05, from both values obtained by indirect measurement. In patients without hypotension the automatic device may be substituted for the MS and direct blood pressure methods. The automatic device may offer the advantage of decreasing observer bias and variability in blood pressure measurement.     

Accurate blood pressure measurement

The most critical requirement for obtaining accurate blood pressure measurements is that the Korotkoff sounds be loud. Loudness can be enhanced by various techniques of cuff inflation and chest piece placement. The type of manometer, cuff size, and cuff placement are also important factors in obtaining accurate blood pressure readings. Correct systolic pressure measurement depends on proper inflation and deflation of the cuff. True diastolic pressure is usually closer to the disappearance point of Korotkoff sounds than to the muffling phase. Blood pressure should be recorded to the nearest 5 mm Hg because measurement to the nearest 2 mm Hg is not meaningful and is too difficult and time-consuming.     

Comparison of Blood Pressure Measured by Oscillometry from the Supraorbital Artery and Invasively from the Radial Artery

In previous studies, oscillometric blood pressure measured from the supraorbital artery has been shown to agree quite well with pressure measured from the brachial artery in normal subjects. In this study, surgical patients whose conditions warranted the use of invasive blood pressure monitoring during the surgery were chosen. We compared systolic and diastolic blood pressure measured oscillometrically from the supraorbital artery with intraarterial blood pressures, measured invasively from the radial artery. A pressure bladder was attached to the forehead of each patient. The bladder was connected to a forehead blood pressure monitor. A catheter was inserted in a radial artery, and connected to a pressure monitor. Forehead blood pressure was measured every 5 min. Radial arterial pressure was averaged over the same period during which the forehead measurement was made. Blood pressures measured with the two methods were compared. For the systolic pressure, the difference between the two methods was –9.9 ± 17.9 mm Hg (mean ± SD). For diastolic pressure, the difference was –8.0 ± 10.9 mm Hg. There was a significant difference between the two methods in the patient population chosen in this study.     

Noninvasive Estimation of the Blood Pressure Waveform in the Carotid Artery Using Continuous Finger Blood Pressure Monitoring

To noninvasively estimate the blood pressure continuously in the common carotid artery (CCA), we obtained the distension waveform of the CCA from seven healthy volunteers and 20 hypertensive patients using radio-frequency ultrasound. Consequently, it was calibrated by the mean and diastolic pressure measured in the finger artery and compared with applanation tonometry, calibrated using the systolic and diastolic pressure in the brachial artery. The mean difference in estimating the mean blood pressure was 0.3 mm Hg (limits of agreement: –11.7 to 12.3 mm Hg). In estimating the systolic blood pressure, the mean difference was 8.0 mm Hg (limits of agreement: –29.8 to 45.8 mm Hg) and showed increasing variation with blood pressure. The systolic blood pressure values can be expected between 0.83 and 1.35 times the control method. In this study, we obtained proof-of-principle for noninvasively measuring blood pressure in the CCA using continuous finger blood pressure monitoring. This opens the way to estimating location specific arterial stiffness and intra-plaque elasticity.