Reliability of orthostatic beat-to-beat blood pressure tests: implications for population and clinical studies

Objective: To assess the test–retest reliability of orthostatic beat-to-beat blood pressure responses to active standing and related clinical definitions of orthostatic hypotension. Methods: A random sample of community-dwelling older adults from the pan-European Survey of Health, Ageing and Retirement in Europe, Ireland underwent a health assessment that mimicked that of the Irish Longitudinal Study on Ageing. An active stand test was performed using continuous blood pressure measurements. Participants attended a repeat assessment 4–12 weeks after the initial measurement. A mixed-effects regression model estimated the reliability and minimum detectable change while controlling for fixed observer and time of day effects. Results: A total of 125 individuals underwent repeat assessment (mean age 66.2 ± 7.5 years; 55.6% female). Mean time between visits was 84.3 ± 23.3 days. There was no significant mean difference in heart rate or blood pressure recovery variables between the first and repeat assessments. Minimum detectable change was noted for changes from resting values in systolic blood pressure (26.4 mmHg) and diastolic blood pressure (13.7 mmHg) at 110 s and for changes in heart rate (10.9 bpm) from resting values at 30 s after standing. Intra-class correlation values ranged from 0.47 for nadir values to 0.80 for heart rate and systolic blood pressure values measured 110 s after standing. Conclusion: Continuous orthostatic beat-to-beat blood pressure and related clinical definitions show low to moderate reliability and substantial natural variation over a 4–12-week period. Understanding variation in measures is essential for study design or estimating the effects of orthostatic hypotension, while clinically it can be used when evaluating longer term treatment effects

Measures of frailty in population-based studies: An overview

Although research productivity in the field of frailty has risen exponentially in recent years, there remains a lack of consensus regarding the measurement of this syndrome. This overview offers three services: first, we provide a comprehensive catalogue of current frailty measures; second, we evaluate their reliability and validity; third, we report on their popularity of use

Efficient rendering of regions of response in list-mode reconstruction for PET

We have developed a new algorithm for fast region of response rendering in Positron Emission Tomography (PET). The algorithm can be applied efficiently to Expectation Maximization (EM) techniques that include per-event probability distributions with shapes more complex than symmetric tubes of response. The algorithm is generic for any system geometry and draws the scalar field associated to a generic input kernel with a constant cut-off threshold independent from the actual kernel shape. In the current version it has been tested for reconstructing List-Mode (LM) data simulated with GATE on the rPET small animal scanner and used with a 2D Gaussian kernel specifically designed for the rPET. EM parallelization has been achieved at per-event level on a 8 core dual CPU. Results show that the new algorithm allows for LM reconstruction in low times with complex kernel functions of the relative position of the voxel with respect to the line of response

Phenotypes of orthostatic blood pressure behaviour and association with visual acuity

BACKGROUND: Manifestations of neurocardiovascular instability (NCVI), including orthostatic hypotension (OH) orthostatic hypertension (OHTN) and impaired blood pressure variability (BPV), have been associated with cardiovascular (CV) events. The eye is highly vascular and we propose an ideal target end organ to investigate pathological implications of NCVI.OBJECTIVE: To identify and define clinically applicable phenotypes of orthostatic blood pressure (BP) behaviour, analogous to OH, OHTN, and orthostatic BPV and to investigate their relationship to vision.METHODS: Wave one data from the Irish Longitudinal Study on Ageing (TILDA) were used. Orthostatic BP (OBP) phenotypes were identified and defined from beat-to-beat BP data, measured by digital photoplethysmography during an active stand (AS) lasting 110 s (s). Visual acuity (VA) was assessed using the Early Treatment Diabetic Retinopathy Study (EDTRS) LogMAR chart. The relationship between OBP phenotypes and VA in 4355 adults aged ≥50 years was investigated through multivariate linear regression models.RESULTS: There was a wide fluctuation in the prevalence of OH and OHTN up to 20 s after standing. After 30 s, four distinct OBP phenotypes were identified: in 70 % BP stabilised to within 20/10 mmHg of baseline BP, 4 % had persistent OH, 2 % had persistent OHTN and 25 % had exaggerated orthostatic blood pressure variability BPV. Systolic BPV was associated with worse VA (P = 0.02) as was diastolic BPV (P = 0.03), following adjustment for demographics, health behaviours, self-report eye diseases and diabetes, uncorrected refractive error, objective hypertension and antihypertensives.CONCLUSIONS: The hypothesis that NCVI may independently modulate CV risk is supported the independent association of exaggerated BPV and worse VA.</p