More accurate systolic blood pressure measurement is required for improved hypertension management: a perspective

Evaluation of a novel cuffless photoplethysmography-based wristband for measuring blood pressure according to the regulatory standards

Aims

Elevated blood pressure (BP) is a key risk factor in cardiovascular diseases. However, obtaining reliable and reproducible BP remains a challenge. This study, therefore, aimed to evaluate a novel cuffless wristband, based on photoplethysmography (PPG), for continuous BP monitoring.

Methods and results

Predictions by a PPG-guided algorithm were compared to arterial BP measurements (in the sub-clavian artery), obtained during cardiac catheterization. Eligible patients were included and screened based on AAMI/European Society of Hypertension (ESH)/ISO Universal Standard requirements. The machine learning-based BP algorithm required three cuff-based initialization measurements in combination with ∼100 features (signal-derived and patient demographic-based). Ninety-seven patients and 420 samples were included. Mean age, weight, and height were 67.1 years (SD 11.1), 83.4 kg (SD 16.1), and 174 cm (SD 10), respectively. Systolic BP was ≤100 mmHg in 48 samples (11%) and ≥160 mmHg in 106 samples (25%). Diastolic BP was ≤70 mmHg in 222 samples (53%) and ≥85 mmHg in 99 samples (24%). The algorithm showed mean errors of ±3.7 mmHg (SD 4.4 mmHg) and ±2.5 mmHg (SD 3.7 mmHg) for systolic and diastolic BP, respectively. Similar results were observed across all genders and skin colours (Fitzpatrick I-VI).

Conclusion

This study provides initial evidence for the accuracy of a PPG-based BP algorithm in combination with a cuffless wristband across a range of BP distributions. This research complies with the AAMI/ESH/ISO Universal Standard, however, further research is required to evaluate the algorithms performance in light of the remaining European Society of Hypertension recommendations.

Clinical trial registration

www.clinicaltrials.gov, NCT05566886.

Feasibility of Precision Medicine in Hypertension Management-Scope and Technological Aspects

Personalized management of diseases by considering relevant patient features enables optimal treatment, instead of management according to an average patient. Precision management of hypertension is important, because both susceptibility to complications and response to treatment vary between individuals. While the use of genomic and proteomic personal features for widespread precision hypertension management is not practical, other features, such as age, ethnicity, and cardiovascular diseases, have been utilized in guidelines for hypertension management. In precision medicine, more blood-pressure-related clinical and physiological characteristics in the patient's profile can be utilized for the determination of the threshold of hypertension and optimal treatment. Several non-invasive and simple-to-use techniques for the measurement of hypertension-related physiological features are suggested for use in precision management of hypertension. In order to provide precise management of hypertension, accurate measurement of blood pressure is required, but the available non-invasive blood pressure measurement techniques, auscultatory sphygmomanometry and oscillometry, have inherent significant inaccuracy-either functional or technological-limiting the precision of personalized management of hypertension. A novel photoplethysmography-based technique for the measurement of systolic blood pressure that was recently found to be more accurate than the two available techniques can be utilized for more precise and personalized hypertension management.

Validation of Omron HBP-1100-E Professional Blood Pressure Measuring Device According to the American Association for the Advancement of Medical Instrumentation Protocol: The PERSIAN Guilan Cohort Study (PGCS)

BACKGROUND

Blood pressure (BP) measurement accuracy is critical to the diagnosis and management of hypertension. The aim of the present study was to validate the Omron HBP-1100-E professional blood pressure measuring device in accordance with the American Association for the Advancement of Medical Instrumentation in Iranian adults.

MATERIALS AND METHODS

Simultaneous blood pressure auscultator measurements were obtained by two observers using mercury sphygmomanometers as a reference, sequentially with a measurement by using the Omron HBP-1100-E device. Absolute device-reference blood pressure differences were categorized into three error categories (within 5, 10, and 15 mmHg), and mean device-reference blood pressure difference (standard deviation) was calculated and evaluated using the American Association for the Advancement of Medical Instrumentation criteria.

RESULTS

A total of 85 participants (250 paired readings) were enrolled to the study. 26.8%, 55.6%, and 79.6% of the device-reference blood pressure differences agreed to within 5, 10 and 15 mmHg, respectively, for systolic blood pressure, and 39.6%, 69.2%, and 81.6% of measurements for diastolic blood pressure, respectively, and failed to pass the protocol criteria. The mean device-reference blood pressure difference was 8.0 ± 13.1 mmHg for systolic BP and 2.2 ± 11.3 mmHg for diastolic BP, and was >5.0 ± 8.0 mmHg (required criteria).

CONCLUSION

Omron HBP-1100-E professional blood pressure monitor is not desirable for measuring the BP for Iranian adults as it overestimates blood pressure in this population.

Quantification of effects of mean blood pressure and left ventricular mass on noninvasive fast fractional flow reserve

While brachial mean blood pressure (MBP) and left ventricular mass (LVM) measured from CTCA are the two CFD simulation input parameters, their effects on noninvasive fractional flow reserve (FFRB) have not been systematically investigated. We demonstrate that inaccurate MBP and LVM inputs differing from patient-specific values could result in misclassification of borderline ischemic lesions. This is important in the clinical application of noninvasive FFR in coronary artery disease diagnosis.

Predictors of clinically relevant differences between noninvasive versus arterial blood pressure

OBJECTIVE

Blood pressure (BP) measurements are important for managing patients with hypertensive emergencies (HE). Previous studies showed that there was significant difference between IABP and NIBP but no information whether these differences changed management. Our study investigated the factors associated with the differences affecting BP management of patients with HE.

METHODS

This was a retrospective study involving adult patients admitted to a resuscitation unit. We screened all patients who received IABP upon admission between 06/01/2017 and 12/31/2017 as sample size calculation recommended 64 patients. Primary outcome was the clinical relevance of the difference of IABP vs. NIBP, which was defined as having both: a) difference of 10 mm of mercury (mmHg), and b) resulting in possible change of blood pressure managements according to treatment guidelines. We performed backward stepwise multivariable logistic regression to measure associations.

RESULTS

We analyzed 147 patients whose mean age was 69 (±16) years and included 69 (47%) patients with spontaneous intracerebral hemorrhage (sICH). Mean difference between IABP and NIBP was 21 (±16) mmHg while 41 (28%) patients who had difference affecting managements. In multivariable regression, sICH (Odd Ratios 13.5, 95%CI 2.3-79.5, p-value < 0.001) was significantly associated with clinically relevant difference between the two modalities of BP monitoring.

CONCLUSIONS

There was a large difference between IABP and NIBP among patients with hypertensive emergencies. Up to 30% of patients had clinically relevant differences. Patients with sICH were more likely to have differences affecting BP management. Further studies are needed to confirm our observation.

Nonlinear and time-dependent effects of sparsely measured continuous time-varying covariates in time-to-event analysis

Many flexible extensions of the Cox proportional hazards model incorporate time-dependent (TD) and/or nonlinear (NL) effects of time-invariant covariates. In contrast, little attention has been given to the assessment of such effects for continuous time-varying covariates (TVCs). We propose a flexible regression B-spline-based model for TD and NL effects of a TVC. To account for sparse TVC measurements, we added to this model the effect of time elapsed since last observation (TEL), which acts as an effect modifier. TD, NL, and TEL effects are estimated with the iterative alternative conditional estimation algorithm. Furthermore, a simulation extrapolation (SIMEX)-like procedure was adapted to correct the estimated effects for random measurement errors in the observed TVC values. In simulations, TD and NL estimates were unbiased if the TVC was measured with a high frequency. With sparse measurements, the strength of the effects was underestimated but the TEL estimate helped reduce the bias, whereas SIMEX helped further to correct for bias toward the null due to "white noise" measurement errors. We reassessed the effects of systolic blood pressure (SBP) and total cholesterol, measured at two-year intervals, on cardiovascular risks in women participating in the Framingham Heart Study. Accounting for TD effects of SBP, cholesterol and age, the NL effect of cholesterol, and the TEL effect of SBP improved substantially the model's fit to data. Flexible estimates yielded clinically important insights regarding the role of these risk factors. These results illustrate the advantages of flexible modeling of TVC effects.

Reflection on modern methods: five myths about measurement error in epidemiological research

Epidemiologists are often confronted with datasets to analyse which contain measurement error due to, for instance, mistaken data entries, inaccurate recordings and measurement instrument or procedural errors. If the effect of measurement error is misjudged, the data analyses are hampered and the validity of the study's inferences may be affected. In this paper, we describe five myths that contribute to misjudgments about measurement error, regarding expected structure, impact and solutions to mitigate the problems resulting from mismeasurements. The aim is to clarify these measurement error misconceptions. We show that the influence of measurement error in an epidemiological data analysis can play out in ways that go beyond simple heuristics, such as heuristics about whether or not to expect attenuation of the effect estimates. Whereas we encourage epidemiologists to deliberate about the structure and potential impact of measurement error in their analyses, we also recommend exercising restraint when making claims about the magnitude or even direction of effect of measurement error if not accompanied by statistical measurement error corrections or quantitative bias analysis. Suggestions for alleviating the problems or investigating the structure and magnitude of measurement error are given.

Blood pressure variability in the management of hypertensive emergency: A narrative review

Hypertensive emergencies (HTNe) primarily focus on decreasing the blood pressure to specific targets. However, there are emerging data surrounding the potential clinical effects of blood pressure variability (BPV) in patients with HTNe. This narrative review highlights the various definitions of BPV, the emerging role of BPV, and the clinical data surrounding BPV in the HTNe setting. Clinical studies were obtained from a PubMed search through October 2018 utilizing PICO methodology. Original research articles, systematic reviews, and meta-analyses were considered for inclusion. Articles were selected for inclusion based on the relevancy of the article investigating BPV in the HTNe setting. There is currently no accepted standard to express BPV in the acute care setting of HTNe, and various parameters have been reported. There are very limited data regarding BPV outside of the neurologic HTNe setting. In the acute treatment phase of neurologic HTNe, BPV is consistently associated with increased risk of unfavorable outcomes. In the HTNe setting, continuous infusion of calcium channel blockers may optimize BPV compared to other agents. Based on current data, BPV should be investigated in a prospective systemic fashion. Efforts should be taken to ensure that BPV is minimized in the acute phase of HTNe, especially for those patients with intracranial hemorrhage. This reduced BPV is associated with improved favorable outcomes, but further study investigating specific pharmacologic agents is needed.

Can Photoplethysmography Replace Arterial Blood Pressure in the Assessment of Blood Pressure?

Arterial Blood Pressure (ABP) and photoplethysmography (PPG) are both useful techniques to monitor cardiovascular status. Though ABP monitoring is more widely employed, this procedure of signal acquisition whether done invasively or non-invasively may cause inconvenience and discomfort to the patients. PPG, however, is simple, noninvasive, and can be used for continuous measurement. This paper focuses on analyzing the similarities in time and frequency domains between ABP and PPG signals for normotensive, prehypertensive and hypertensive subjects and the feasibility of the classification of subjects considering the results of the analysis performed. From a database with 120 records of ABP and PPG, each 120 s in length, the records where separated into epochs taking into account 10 heartbeats, and the following statistical measures were performed: Correlation (r), Coherence (COH), Partial Coherence (pCOH), Partial Directed Coherence (PDC), Directed Transfer Function (DTF), Full Frequency Directed Transfer Function (ffDTF) and Direct Directed Transfer Function (dDTF). The correlation coefficient was r > 0.9 on average for all groups, indicating a strong morphology similarity. For COH and pCOH, coherence (linear correlation in frequency domain) was found with significance (p < 0.01) in differentiating between normotensive and hypertensive subjects using PPG signals. For the dataset at hand, only two synchrony measures are able to convincingly distinguish hypertensive subjects from normotensive control subjects, i.e., ffDTF and dDTF. From PDC, DTF, ffDTF, and dDTF, a consistent, a strong significant causality from ABP→PPG was found. When all synchrony measures were combined, an 87.5 % accuracy was achieved to detect hypertension using a Neural Network classifier, suggesting that PPG holds most informative features that exist in ABP.

Random measurement error: Why worry? An example of cardiovascular risk factors

With the increased use of data not originally recorded for research, such as routine care data (or ‘big data’), measurement error is bound to become an increasingly relevant problem in medical research. A common view among medical researchers on the influence of random measurement error (i.e. classical measurement error) is that its presence leads to some degree of systematic underestimation of studied exposure-outcome relations (i.e. attenuation of the effect estimate). For the common situation where the analysis involves at least one exposure and one confounder, we demonstrate that the direction of effect of random measurement error on the estimated exposure-outcome relations can be difficult to anticipate. Using three example studies on cardiovascular risk factors, we illustrate that random measurement error in the exposure and/or confounder can lead to underestimation as well as overestimation of exposure-outcome relations. We therefore advise medical researchers to refrain from making claims about the direction of effect of measurement error in their manuscripts, unless the appropriate inferential tools are used to study or alleviate the impact of measurement error from the analysis.