Oscillometric Monitor Research Articles

Blood pressure in Warmblood horses before and after a euglycemic-hyperinsulinemic clamp

Insulin resistance (IR) in humans is related to hypertension and impaired vasodilation. Insulin administration has been shown to lower blood pressure both in insulin resistant as well as in insulin sensitive individuals. The aim of the study was to investigate the association between insulin sensitivity and alterations in blood pressure in healthy horses before and after a euglycemic-hyperinsulinemic clamp (EHC). A 3-h EHC was performed in 13 healthy horses (11 mares, 2 geldings). Blood samples for measurement of plasma glucose and insulin were collected before the start of the EHC, every 10 min during the EHC and immediately after the EHC. Mean, systolic- and diastolic blood pressure was measured before and during the final 10 min of the EHC using an indirect high-definition oscillometric monitor (HDO, horse model) applied to the middle of the coccygeal artery. Five consecutive measurements were made in each horse and on each occasion. Insulin and glucose data from the EHC were used to calculate the mean rate of glucose disposal per unit of insulin during steady state (M/I ratio). Insulin resistance was defined as a M/I ratio <5 mg/kg/min/mUL (Lindase et al. in Am J Vet Res 77:300–309, 2016). Insulin administration decreased systolic, diastolic and mean arterial pressure in all horses. The M/I ratio for all horses was negatively correlated with the decrease in systolic blood pressure (r2 = 0.55, P = 0.004) and mean arterial pressure (r2 = 0.31, P = 0.048) but not diastolic blood pressure (r2 = 0.12, P = 0.26). Eight horses were defined as insulin resistant (IR) and five horses had normal insulin sensitivity. The five horses with normal insulin sensitivity showed a greater decrease in systolic blood pressure (−17.0 ± 7.4 vs. −3.4 ± 4.6 mmHg, P = 0.001) and MAP (19.2 ± 14.7 vs. 6.9 ± 8.7 mmHg, P = 0.04) than IR horses. There was no difference in the decrease in diastolic blood pressure between groups (16 ± 12.8 vs. 8.9 ± 12.1 mmHg, P = 0.17). This study indicates that there is a relationship between insulin sensitivity and systolic and MAP in horses. However, studies on a larger number of horses are needed to confirm this association.

Acute effects of interval versus continuous endurance training on pulse wave reflection in healthy young men

Aim: Our aim was to investigate the acute and 24-hour (h) effects of high-intensity interval training (HIIT) and moderate continuous training (MCT) on arterial pulse wave reflection, an established marker of arterial stiffness and cardiovascular risk. Methods: In a randomized cross-over design, 21 young healthy male participants performed a HIIT or a MCT on separate visits. Before and 5 (t5), 20 (t20), 35 (t35), and 50 (t50) minutes after the acute exercise bouts, the crude augmentation index (AIx) and the AIx at a set heart rate (AIx@75) were analysed by applanation tonometry. Starting 1 h post-exercise, both indices were captured over 24-h with an oscillometric monitoring device. Results: AIx did not change significantly after MCT but declined progressively after HIIT, reaching significantly lower values compared to MCT at t35 (P = 0.045) and t50 (P = 0.008). AIx@75 increased after both acute exercise types but was higher after HIIT at t5 (P < 0.001), t20 (P < 0.001) and t35 (P = 0.009) compared to MCT. The 24-h follow-up revealed a significant decline in AIx@75 after HIIT (P = 0.007) but not after MCT (P = 0.813). Conclusions: Exercise intensity affects pulse wave reflection, with different time courses for AIx and AIx@75 post-exercise. Although initially higher after HIIT, AIx@75 declines in the 24-h recovery period indicating more favourable effects on pulse wave reflection compared to MCT. This may result in substantial positive chronic training effects on arterial stiffness in health and cardiovascular disease.

Abstract 20260: The Effect of Lifestyle Recommendations on Blood Pressure and Blood Pressure Control in Patients With Stage I Hypertension: The Prever Treatment Trial

Introduction: Lifestyle recommendations are recommended for patients with Stage I hypertension before starting blood pressure-lowering drugs in patients free of cardiovascular disease. The proportion of patients that have blood pressure (BP) controlled with these recommendations was scarcely reported in a clinical context. Hypothesis: To investigate the rate of response to a short-term lifestyle intervention (LsI) in the first phase of a randomized clinical trial. Methods: PREVER prevention is a double blind, multicenter, randomized clinical trial of effectiveness of drug treatment to control hypertension and target organ damage among individuals with hypertension. It was conducted in 22 centers distributed in 10 Brazilian states. Participants were enrolled in the study if they had hypertension (≥140 of systolic blood pressure or ≥90 mmHg of diastolic blood pressure), confirmed in two visits in the clinics of the study, or if they had normal BP but were using BP-lowering agents. BP measurements were carried out using an oscillometric monitor, and anthropometric measurements were taken in duplicate. All participants were submitted to a lifestyle intervention (LsI) phase, which included detailed recommendations to lose weight, to reduce salt, to adopt a DASH-type diet and to practice physical activities. Blood pressure and control of hypertension were verified after three months. In this analysis, we present the results of blood pressure control and variation in the subsample of participants who had BP higher or equal to 140/90 mmHg. Results: 4 867 volunteers were screened and 1 835 evaluated for enrollment. From these, 685 (37%) had BP within stage I hypertension. After three months of intensive LsI, 420 (61.3%) remained with uncontrolled BP, 249 (36.4%) had BP in the 120-139/80-89 mmHg range, and 16 (2.3%) had normal BP. Systolic and diastolic BP reduced from 143.8 ±7.1 to 138.7 ±12.2 mmHg and 90.4 ±5.9 to 87.7 ±8.7, respectively. Conclusion: Approximately 1/3 of patients with Stage I hypertension have blood pressure controlled after three months of lifestyle recommendations to lose weight, reduce salt intake, adopt a DASH diet and practice physical activities.

Feasibility of a continuous non-invasive arterial pressure (CNAP) device in a prehospital setting

Purpose of the study: Blood pressure (BP) is one of the most important parameters in several clinical settings. Prehospital monitoring of BP can be a vital factor. The continuous non-invasive arterial pressure (CNAP) device provides beat-to-beat pressure readings by using a finger cuff calibrated to a regular oscillometric BP monitor. This study was performed to examine if the CNAP is easy to use and provides accurate data in a prehospital setting. We wanted to investigate if the CNAP is a feasible alternative to the traditional oscillometric BP monitor during ambulance transfer.

Validation of the integration of technology that measures additional "vascular" indices into an ambulatory blood pressure monitoring system.

BackgroundThe objective of this study was to validate the novel integration of oscillometric (Vasotens®) technology into a BPLab® ambulatory blood pressure (BP) monitoring system to measure central BP, the aortic augmentation index, and pulse wave velocity (PWV) compared with the recommended and widely accepted tonometric method.MethodsThe ARTERY Society guidelines for comparison of PWV measurement techniques were used as the basis for recruitment of 99 individuals (mean age 44±19 years, 52 males). The standard for comparison was the conventional “classic” SphygmoCor device.ResultsAccordance of the two methods was satisfactory (r=0.98, mean difference of 2.9±3.5 mmHg for central systolic BP; r=0.98, mean difference of −1.1±2.3 mmHg for central diastolic BP; r=0.83, mean difference of −2.6%±13% for aortic augmentation index; r=0.85, mean difference of 0.69±1.4 for PWV).ConclusionThe performance of Vasotens algorithms using an oscillometric ambulatory BP monitoring system is feasible for accurate diagnosis, risk assessment, and evaluation of the effects of antihypertensive drugs.

An armband wearable device for overnight and cuff-less blood pressure measurement.

24-h blood pressure (BP) has significant prognostic value for cardiovascular risk screening, but the present BP devices are mainly cuff-based, which are unsuitable for long-term BP measurement, especially during nighttime. In this paper, we developed an armband wearable pulse transit time (PTT) system for 24-h cuff-less BP measurement and evaluated it in an unattended out-of-laboratory setting. Ten healthy young subjects participated in this ambulatory study, where PTT was measured at 30-min interval by this wearable system and the reference BP was measured by a standard oscillometric ambulatory BP monitor. Due to the misalignment of BP and PTT on their recording time caused by the different measurement principles of the two BP devices, a new estimation method has been proposed: transients in PTT were removed from the raw data by defined criteria, and then evenly interpolated, low-pass filtered, and resampled to synchronize at the time when BP was recorded. The results show that with the proposed method, the correlation between PTT and systolic BP (SBP) during nighttime with dynamic range of 21.8 ± 14.2mmHg has improved from -0.50 ± 0.24 to -0.62 ± 0.20 , and the difference between the estimated and reference SBP has improved from 0.7 ± 10.7 to 2.8 ± 8.2mmHg with root mean square error reduced from 10.7 to 8.7mmHg. In addition, the correlation between a very low frequency component of SBP and PTT obtained from the proposed method during nighttime is -0.80 ± 0.10 and the difference is 2.4 ± 5.7mmHg for a dynamic BP range of 13.5 ± 8.0mmHg. It is therefore concluded from this study that the proposed wearable system has great potential to be used for overnight SBP monitoring, especially to measure the averaged SBP over a long period.

Logistic ordinal regression for the calibration of oscillometric blood pressure monitors

Oscillometric blood pressure (BP) monitors are omnipresent and used on a daily basis for personalized healthcare. Nevertheless, physicians generally approach these devices cautiously since the mercury Korotkoff sphygmomanometer remains the golden standard. Various reasons explain the hesitating attitude of the medical world towards automated BP monitors: (i) its principle is based on the pressure pulsations arriving at the cuff by the cardiac cycle instead of an audio wave used by physicians triggered by the turbulences in the artery, (ii) the actual computation of the systolic and diastolic BP from the measured oscillometry is manufacturer dependent and not based on general scientific principles, (iii) the quality of the oscillometric monitors is labeled by a trial such that the devices correspond well to the Korotkoff method for the average healthy patient but deviates for patients suffering from hypo- or hypertension. In this paper, we develop a statistical learning technique to calibrate and correct an oscillometric monitor such that the device better corresponds to the Korotkoff method regardless of the health status of the patient. The technique is based on logistic regression which allows correcting and eliminating systematic errors caused by patients suffering from hyper -or hypotension. No user interaction is required since the technique is able to train and validate the calibration procedure in an unsupervised way. In our case study, the systematic error is reduced by nearly 50% corresponding to the performance specifications of the device.

Interarm blood pressure difference and target organ damage in the general population

The objective of the study was to investigate interarm differences of blood pressure (BP) and its determinants, and to clarify whether both arms are equally good in assessing BP and target organ damage in the general population. We studied a representative sample of Finnish adult population with 484 study participants, ages 25-74 years. BP was measured twice by an oscillometric monitor simultaneously on both arms. Study participants underwent a clinical examination including measurements of serum lipids, glucose and indicators of target organ damage. BP was 2.3/0.2 mmHg higher on right than on left arm (P < 0.001/P = 0.15 for SBP/DBP differences). SBP and DBP measured on right and left arms correlated equally with left ventricular mass index (LVMI), interventricular septal thickness (IVST), posterior wall thickness (PWT), pulse wave velocity (PWV) and albuminuria. Higher SBP level was an independent determinant of both greater systolic and diastolic interarm BP difference. Exaggerated absolute diastolic interarm BP difference (>5 mmHg) was associated with higher BMI, arm circumference, LVMI, IVST and PWT, whereas exaggerated absolute systolic interarm BP difference (>10 mmHg) was not associated with any clinical variables. There was only a small difference in BP between arms in a healthy general population. Both arms are equally good determinants of target organ damage. BP should be measured at least once on both arms and prefer the arm with higher BP readings in the future BP measurements.

Diagnostic Performance of a Stand-Alone Central Blood Pressure Monitor: Application of Central Blood Pressure in the Diagnosis of High Blood Pressure

Oscillometric central blood pressure (CBP) monitors have emerged as a new technology for blood pressure (BP) measurements. With a newly proposed diagnostic threshold for CBP, we investigated the diagnostic performance of a novel CBP monitor. We recruited a consecutive series of 138 subjects (aged 30-93 years) without previous use of antihypertensive agents for simultaneous invasive and noninvasive measurements of BP in a catheterization laboratory. With the cutoff (CBP ≥130/90 mm Hg) for high blood pressure (HBP), the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the novel CBP monitor were calculated with reference to the measured CBP. In comparison, the diagnostic performance of the conventional cuff BP was also evaluated. The noninvasive CBP for detecting HBP in a sample with a prevalence of 52% showed a sensitivity of 93% (95% confidence interval (CI) = 91-95), specificity of 95% (95% CI = 94-97), PPV of 96% (95% CI = 94-97), and NPV of 93% (95% CI = 90-95). In contrast, with cuff BP and the traditional HBP criterion (cuff BP ≥140/90 mm Hg), the sensitivity, specificity, PPV, and NPV were 49% (95% CI = 44-53), 94% (95% CI = 92-96), 90% (95% CI = 86-93), and 63% (95% CI 59-66), respectively. A stand-alone oscillometric CBP monitor may provide CBP values with acceptable diagnostic accuracy. However, with reference to invasively measured CBP, cuff BP had low sensitivity and NPV, which could render possible management inaccessible to a considerable proportion of HBP patients, who may be identifiable through noninvasive CBP measurements from the CBP monitor.

Validation of Oscillometric Pulse Wave Analysis Measurements in Children

Pulse wave analysis (PWA) has emerged as a noninvasive, valid, reliable, and widely used technique to investigate central blood pressures and systemic arterial wave reflection (augmentation index). The gold-standard technique is tonometry, but this technique can be challenging, especially when used on children. The purpose of this study was to validate oscillometric PWA for use in children. Fifty-seven healthy children were recruited for participation. Central blood pressures and peripheral augmentation index (pAIx) were measured objectively using oscillometric (Pulsecor R7) and tonometric (SphygmaCor) devices. All measurements were made during the same visit under standardized conditions between the hours of 8 am and 10 am in the fasted state. Tonometric measurements were unsuccessful on 1 child. Comparisons were made on 56 children (mean age = 9.8±1.0 y; 57% male). A very strong relationship was found between devices for central systolic (r = 0.94; P < 0.001), diastolic (r = 0.99; P < 0.001) and mean (r = 0.96; P < 0.001) blood pressures. However, Bland-Altman analysis indicated a bias toward greater systolic blood pressures with the oscillometric monitor (mean difference = 4.5mm Hg; 95% confidence interval (CI) = -5.16 to -3.89). A good relationship was found for pAIx (r = 0.71; P < 0.001); the mean difference between devices was -1.70% (95% CI = -4.47% to 1.08%), which is not significantly different from zero. Findings from this study suggest that oscillometric PWA provides valid measures of central blood pressure and arterial wave reflection in children aged 8-10 years.

Blood pressure among rural Montenegrin children in relation to poverty and gender

Health inequalities may begin during childhood. The aim of this study was to investigate the main effect of poverty and its interactive effect with gender on children's blood pressure. The study was performed in two elementary schools from a rural region near Podgorica, the capital of Montenegro. A questionnaire including questions on family monthly income, children's physical activity and the consumption of junk food was self-administered by parents of 434 children (223 boys and 211 girls) aged 6-13 years. Children's poverty level was assessed using the recommendations from the National Study on Poverty in Montenegro. Children's body weight and height were measured and body mass index-for-gender-and-age percentile was calculated. An oscillometric monitor was used for measurement of children's resting blood pressure in school. A two-factorial analysis of variance with body mass index percentile, physical activity and junk food as covariates showed an interaction of gender and poverty on children's blood pressure, pointing to synergy between poverty and female gender, with statistical significance for raised diastolic pressure (F = 5.462; P = 0.021). Neither physical activity nor the consumption of junk food explained the interactive effect of poverty and gender on blood pressure. We show that poverty is linked to elevated blood pressure for girls but not boys, and this effect is statistically significant for diastolic pressure. The results are discussed in the light of gender differences in stress and coping that are endemic to poverty.

Evaluation of an oscillometric blood pressure monitor for use in anesthetized sheep

ObjectiveTo determine the accuracy of an oscillometric blood pressure monitor in anesthetized sheep. Study designProspective study. AnimalsTwenty healthy adult sheep, 11 males and nine females, weighing 63.6 ± 8.6 kg. MethodsAfter premedication with buprenorphine or transdermal fentanyl, anesthesia was induced with ketamine‐midazolam and maintained with isoflurane and ketamine, 1.2 mg kg−1 hour−1, ± lidocaine, 3 mg kg−1 hour−1. Invasive blood pressure measurements were obtained from an auricular arterial catheter and noninvasive measurements were from a cuff on the metatarsus or antebrachium. Simultaneous invasive and noninvasive measurements were recorded over a range (55–111 mmHg) of mean arterial pressures (MAP). Isoflurane concentration was increased to decrease MAP and decreasing the isoflurane concentration and infusing dobutamine achieved higher pressures. Invasive and noninvasive measurements were compared. ResultsCorrelation (R2) was good between the two methods of measurement (average of three consecutive readings) for systolic (SAP) (0.87), diastolic (DAP) (0.86), and mean (0.90) arterial pressures (p < 0.001). Bias ± SD between noninvasive and invasive measurements for SAP was 3 ± 8 mmHg, for DAP was −10 ± 7 mmHg, and MAP was −7 ± 6 mmHg. There was no significant difference between the average of three measurements and use of the first measurement. Correlations using the first measurement were SAP (0.82), DAP (0.84), and MAP (0.89). Bias ± SD for SAP was 3 ±10 mmHg, for DAP was −11 ± 7 mmHg, and MAP was −7 ± 6 mmHg. The oscillometric monitor slightly overestimated SAP and underestimated DAP and MAP for both average values and the first reading. Conclusions and clinical relevanceThis oscillometric model provided MAP measurements that were acceptable by ACVIM standards. MAP measurements with this monitor were lower than those found with the invasive technique so a clinical diagnosis of hypotension may be made in sheep that are not hypotensive.

Increased heart rate variability but no effect on blood pressure from 8 weeks of hatha yoga – a pilot study

BackgroundYoga exercises are known to decrease stress and restore autonomic balance. Yet knowledge about the physiological effects of inversion postures is limited. This study aimed to investigate the effects of inversion postures (head below the heart) on blood pressure (BP) and heart rate variability (HRV).MethodsTwelve healthy women and men took part in an 8-week yoga program (60 min once a week). BP was measured with an automatic Omron mx3 oscillometric monitoring device and HRV with a Holter 24-hour ECG at baseline and 8 weeks after the intervention.ResultsThere was no significant effect of inversion postures on BP. Nine out of 12 participants showed a significant increase in HRV (p < 0.05) at night (2 hours) on pNN50% (12.7 ± 12.5 to 18.2 ± 13.3). There were no significant changes in other HRV measures such as NN50, LF, HF, LF/HF ratio, LF normalized units (n.u.), HF n.u. and RMSSD.ConclusionEight weeks of hatha yoga improved HRV significantly which suggests an increased vagal tone and reduced sympathetic activity.

Inaccuracy in Determining Mean Arterial Pressure With Oscillometric Blood Pressure Techniques

Accurate determination of MAP is important in the calibration of pressure waveforms for calculating central blood pressure (BP). Currently, a precise, individualized measurement of mean arterial pressure (MAP) can be obtained only with intra-arterial measurements of BP or with applanation tonometry. We conducted a study of whether easy-to-use oscillometric devices, validated for systolic and diastolic BP measurements (BHS protocol), give accurate determinations of MAP. We compared measurements of MAP made with the WatchBP Office oscillometric monitor in 102 subjects with values of MAP assessed by pulse-wave analysis (PWA) (SphygmoCor). The mean (± SD) oscillometric MAP assessed with the WatchBP Office monitor was 97 ± 12.5 mm Hg, which was equivalent to 23.6 ± 9.1% of the pulse pressure (PP) above diastolic blood pressure (DBP). The MAP as assessed through PWA was 106 ± 14.6 mm Hg (P < 0.01), or 37.7 ± 3.9% of the PP above DBP. In simultaneous measurements made on both arms with the WatchBP Office monitor we observed individual differences in pressure in the left vs. the right arm. The MAP displayed by the WatchBP Office monitor is too imprecise to be used for calibrations. We suggest that devices for measuring BP not display MAP unless their accuracy is tested.

Invasive blood pressure monitoring systems in the ICU

Invasive blood pressure monitoring is the most reliable method in critically ill patients. Noninvasive oscillometric pressure monitoring is also widely used in the ICU, and discrepancies between the methods are common. Inclusion of a blood-conserving device may influence the fidelity of the system and reliability of the invasive pressure values. We examined the dynamic response characteristics of the monitoring systems with and without the blood-conserving device, and assessed agreement between invasive and noninvasive blood pressures. Fifty-three invasive arterial blood pressure monitoring systems were evaluated over an 8-week period. A standard fast flush test was performed. The natural frequency (Fn) and the amplitude ratio of the invasive monitoring systems were calculated. Simultaneous invasive and noninvasive blood pressures were recorded, and the agreement between two methods was evaluated. The Fn was significantly higher (15.7 ± 5.1 Hz) in the systems without the blood-conserving device than in the systems containing the device (9.1 ± 2.6 Hz). There was no significant difference in the amplitude ratio. Significant differences were observed between invasive and noninvasive pressures, with systolic pressure showing more variability than the mean arterial pressure. Inclusion of a blood-conserving device in the existing monitoring circuit may affect its dynamic response characteristics. Discrepancies between invasive and noninvasive pressures are common, with systolic pressure showing more variability than the mean arterial pressure. The low Fn of the invasive monitoring system could be a contributing factor to the discrepancy between two methods.

Traffic noise and blood pressure in low-socioeconomic status, African-American urban schoolchildren

The primary aim of this field study was to investigate the relationships among residential noise exposure at home and at school and blood pressure in low-socioeconomic status African-American children. Children were recruited from Boys and Girls Clubs in a mid-sized, Northeastern city. The sample consisted of 250 schoolchildren (128 boys and 122 girls) aged 6-14 years. Each child was interviewed prior to anthropometric and blood pressure measurement. An oscillometric monitor was used for measurement of resting blood pressure. Correlation analysis in the overall sample showed no significant relationship between noise exposure and children's blood pressure. No interactions were found between noise at home and at schools as well as orientation of bedroom and/or living room and noise at home with blood pressure. A sub-sample of children was also examined by adding the orientation of bedroom and living room as inclusion criteria (n = 128), and there was an interaction between noise exposure and age on systolic blood pressure. In younger children aged 6-10 years, a significant positive relation was found between noise levels at homes and systolic blood pressure, controlling for body mass index (B = 0.48, 95% C.I. = 0.07 -0.88, p = 0.02).

Assessment of central haemomodynamics from a brachial cuff in a community setting.

BackgroundLarge artery stiffening and wave reflections are independent predictors of adverse events. To date, their assessment has been limited to specialised techniques and settings. A new, more practical method allowing assessment of central blood pressure from waveforms recorded using a conventional automated oscillometric monitor has recently been validated in laboratory settings. However, the feasibility of this method in a community based setting has not been assessed.MethodsOne-off peripheral and central haemodynamic (systolic and diastolic blood pressure (BP) and pulse pressure) and wave reflection parameters (augmentation pressure (AP) and index, AIx) were obtained from 1,903 volunteers in an Austrian community setting using a transfer-function like method (ARCSolver algorithm) and from waveforms recorded with a regular oscillometric cuff. We assessed these parameters for known differences and associations according to gender and age deciles from <30 years to >80 years in the whole population and a subset with a systolic BP < 140 mmHg.ResultsWe obtained 1,793 measures of peripheral and central BP, PP and augmentation parameters. Age and gender associations with central haemodynamic and augmentation parameters reflected those previously established from reference standard non-invasive techniques under specialised settings. Findings were the same for patients with a systolic BP below 140 mmHg (i.e. normotensive). Lower values for AIx in the current study are possibly due to differences in sampling rates, detection frequency and/or averaging procedures and to lower numbers of volunteers in younger age groups.ConclusionA novel transfer-function like algorithm, using brachial cuff-based waveform recordings, provides robust and feasible estimates of central systolic pressure and augmentation in community-based settings.

Electrocardiogram-Assisted Blood Pressure Estimation

Accurate automatic noninvasive assessment of blood pressure (BP) presents a challenge due to conditions like arrhythmias, obesity, and postural changes that tend to obfuscate arterial amplitude pulsations sensed by the cuff. Researchers tried to overcome this challenge by analyzing oscillometric pulses with the aid of a higher fidelity signal-the electrocardiogram (ECG). Moreover, pulse transit time (PTT) was employed to provide an additional method for BP estimation. However, these methods were not fully developed, suitably integrated, or tested. To address these issues, we present a novel method whereby ECG-assisted oscillometric and PTT (measured between ECG R-peaks and maximum slope of arterial pulse peaks) analyses are seamlessly integrated into the oscillometric BP measurement paradigm. The method bolsters oscillometric analysis (amplitude modulation) with more reliable ECG R-peaks provides a complementary measure with PTT analysis (temporal modulation) and fuses this information for robust BP estimation. We have integrated this technology into a prototype that comprises a BP cuff with an embedded conductive fabric ECG electrode, associated hardware, and algorithms. A pilot study has been undertaken on ten healthy subjects (150 recordings) to validate the performance of our prototype against United States Food and Drug Administration approved Omron oscillometric monitor (HEM-790IT). Our prototype achieves mean absolute difference of less than 5 mmHg and grade A as per the British Hypertension Society protocol for estimating BP, with the reference Omron monitor.

Abstract NS 4: Non-Invasive Oscillometric Blood Pressure Monitoring in tPA Treated Patients: Is Mean Arterial Pressure Associated with Patient Outcomes?

Background: Blood pressure (BP) parameters for management of tPA treated patients are well known among experienced stroke clinicians, and violation of systolic and diastolic BP limits have previously been shown to be associated with symptomatic intracerebral hemorrhage (sICH) in tPA treated patients. Non-invasive oscillometric BP monitoring measures a “true” mean arterial pressure (MAP), and then algorithmically defines what systolic and diastolic pressure "might" be. Because this form of BP monitoring has become the national standard, we examined the occurrence of MAP BP elevations to determine their association with sICH and treatment outcome in acute ischemic stroke patients that received systemic tPA. Methods: Two-years of consecutive systemic tPA cases were retrieved from our Stroke Center database and arterial blood pressures for the first 24 hours from time of bolus were entered from auto-recordings in our electronic medical records. Protocol violations in MAP were defined as greater than 120 mm Hg at any point in the first 24 hours from time of bolus. Off-label treatment with intravenous tPA beyond 4.5 hours from symptom onset was identified a priori as a potential counfounder to stroke outcome. Symptomatic intracerebral hemorrhage was defined as an increase in the NIHSS of ≥ 4 points. Spearman’s correlation was used to assess the relationship between MAP and post-tPA NIHSS score. Results: 191 tPA cases were identified for inclusion in the analysis with 150 (79%) receiving their tPA at our Comprehensive Stroke Center and another 41 (21%) administered as a telephone-consult supported drip and ship. Patients were 65.5±16 years of age with median admission NIHSS scores of 12 (IQR=7-17). All patients had normal CT scans or minor changes consistent with acute stroke without hypo-attenuation. A total of 77 (40%) patients experienced a MAP violation overall. There were 11 isolated systolic BP violations, 4 isolated diastolic BP violations, and 21 isolated MAP violations that were otherwise not detectable by a violation in systolic or diastolic parameters, averaging 123.3±2 mm Hg. A total of 2 (1%) sICHs occurred in the sample, and of these 1 was associated with on-label peri-treatment BP protocol violations affecting systolic, diastolic and MAP parameters. An increased reduction in post-tPA NIHSS points was significantly associated with higher MAPs (r=.92; p=.008). Conclusions: Evidence-based guidelines are silent on MAP limits, and MAP is rarely monitored clinically in tPA treated patients despite dependence on the MAP for assignment of systolic and diastolic pressures in oscillometric BP monitoring. Our findings suggest that an improved understanding of the contribution of MAP-dependent oscillometric methods to BP monitoring in acute stroke patients is warranted.

Automated determination of the ankle-brachial index using an oscillometric blood pressure monitor: validation vs. Doppler measurement and cardiovascular risk factor profile

The ankle-brachial index (ABI) is a method used widely for peripheral arterial disease (PAD) diagnosis and cardiovascular risk prediction. This study validated automated ABI measurements taken using an oscillometric blood pressure (BP) monitor allowing simultaneous arm-leg BP measurements. A total of 93 patients (hypertension 83%; dyslipidemia 72%; diabetes 45%; cardiovascular disease 23%; smoking 15%) were submitted to Doppler and automated ABI measurements, performed using a professional oscillometric BP monitor (Microlife WatchBP Office; triplicate simultaneous arm-leg BP measurements), in a randomized order. The mean difference between the Doppler reading (1.08 ± 0.17) and (1) the first oscillometric ABI reading was 0.03 ± 0.11, (2) the average of two oscillometric readings was 0.02 ± 0.10 and (3) the average of three oscillometric readings was 0.02 ± 0.09 (P < 0.01 for all). Strong correlations were found between oscillometric and Doppler ABI (r 0.80, 0.85 and 0.86 for single and average of two and three oscillometric readings, respectively; P < 0.001 for all). Agreement between oscillometric and Doppler ABI in diagnosing PAD (Doppler ABI < 0.9) was found in 95% of cases (κ 0.79; agreement in diabetics: 94%, κ 0.79). A receiver operating characteristic (ROC) curve revealed area under the curve at 0.98, with a 0.97 oscillometric ABI cutoff for optimal sensitivity (92%) and specificity (92%) in diagnosing PAD. Average time for automated ABI measurement was 5.8 vs. 9.3 min for Doppler (P < 0.001). Doppler and oscillometric ABI were associated and predicted (multivariate regression analysis) by the same cardiovascular risk factors (pulse pressure, smoking and cardiovascular disease history). Automated ABI measurement using a professional BP monitor allowing simultaneous arm-leg BP measurements appears to be a reliable and faster alternative to Doppler measurement.