Morphological features of the photoplethysmographic signal: a new approach to characterize the microcirculatory response to photobiomodulation.

Advanced analysis of the morphological features of the photoplethysmographic (PPG) waveform may provide greater understanding of mechanisms of action of photobiomodulation (PBM). Photobiomodulation is a non-ionizing, red to near-infrared irradiation shown to induce peripheral vasodilatation, promote wound healing, and reduce pain. Using laser Doppler flowmetry combined with thermal imaging we found previously in a clinical study that PBM stimulates microcirculatory blood flow and that baseline palm skin temperature determines, at least in part, why some individuals respond favorably to PBM while others do not.

Predictive power of 24-h ambulatory pulse pressure and its components for mortality and cardiovascular outcomes in 11 848 participants recruited from 13 populations.

Background: The role of pulse pressure (PP) 'widening' at older and younger age as a cardiovascular risk factor is still controversial. Mean PP, as determined from repeated blood pressure (BP) readings, can be expressed as a sum of two components: 'elastic PP' (elPP) and 'stiffening PP' (stPP) associated, respectively, with stiffness at the diastole and its relative change during the systole. We investigated the association of 24-h ambulatory PP, elPP, and stPP ('PP variables') with mortality and composite cardiovascular events in different age classes.

Relative and Absolute Risk to Guide the Management of Pulse Pressure, an Age-Related Cardiovascular Risk Factor.

Background: Pulse pressure (PP) reflects the age-related stiffening of the central arteries, but no study addressed the management of the PP-related risk over the human lifespan.

Methods: In 4,663 young (18-49 years) and 7,185 older adults (≥50 years), brachial PP was recorded over 24 hours. Total mortality and all major cardiovascular events (MACEs) combined were coprimary endpoints.

Microcirculatory Response to Photobiomodulation-Why Some Respond and Others Do Not: A Randomized Controlled Study.

Background And Objectives: Photobiomodulation (PBM), a non-ionizing, non-thermal irradiation, used clinically to accelerate wound healing and inhibit pain, was previously shown to increase blood flow. However, some individuals respond to PBM, but others do not. The purpose of this study was to investigate factors affecting this patient-specific response using advanced, noninvasive methods for monitoring microcirculatory activity.

Do estimated 24-h pulse pressure components affect outcome? The Ohasama study.

Objective: Twenty-four-hour ambulatory pulse pressure (PP) is a powerful predictor of outcome. We attempted to apply the recently described PP components, an elastic (elPP), and systolic stiffening (stPP) components from 24-h ambulatory blood pressure (BP) monitoring (AMBP), and examine their influence on outcome in the Ohasama study population.

Design And Methods: Included were participants of the Ohasama study without history of cardiovascular disease (CVD), who were followed-up for total and CVD mortality, and for stroke morbidity.

Ambulatory pulse pressure components: concept, determination and clinical relevance.

Background: Ambulatory pulse pressure (PP) a well known predictor of mortality, is widely believed to be a marker for arterial stiffness. However stiffness itself is pressure-dependent.

Objectives: Developing a model-based method for splitting PP into two components expressing the contribution of a pressure-independent stiffness ('elastic', elPP) and the pressure-dependence of stiffness ('stiffening', stPP), and investigating their predictive power for all-cause mortality.

The response of peripheral microcirculation to gravity-induced changes.

Background: The peripheral microcirculation supplies fresh blood to the small blood vessels, providing oxygen and nutrients to the tissues, removing waste, and maintaining normal homeostatic conditions. The goal of this study was to characterize the response of the peripheral microcirculation, in terms of blood flow and tissue oxygenation variables, to gravity-induced changes.

Methods: The study included 20 healthy volunteers and the experiment involved monitoring central and peripheral variables with the right hand positioned at different heights.

Association of Blood Pressure Variability Ratio With Glomerular Filtration Rate Independent of Blood Pressure and Pulse Wave Velocity.

Background: Blood pressure variability ratio (BPVR)(derived from within-subject SD of 24-hour ambulatory blood pressure [BP]) predicts all-cause mortality independent of BP and has a similar prognostic ability to ambulatory arterial stiffness (AASI). Whether BPVR, and AASI, offer prognostic information beyond measurements of arterial stiffness at a given pressure, as indexed by pulse wave velocity (PWV), is not known.

Methods: We assessed whether BPVR and AASI were associated with indices of subclinical organ damage (TOD) [estimated glomerular filtration rate (eGFR), left ventricular mass index, early-to-late transmitral velocity (E/A), carotid intima-media thickness (IMT)] independent of BP, and whether BPVR-TOD and AASI-TOD relations were independent of PWV (applanation tonometry) in 772 randomly selected participants from an urban, developing community.

The coupling between peripheral microcirculation and slow breathing.

Vasomotion (rhythmic changes in arteriolar diameter) is believed to enhance tissue perfusion at low oxygenation levels. We hypothesized that slow breathing and vasomotion may correlate temporally ("coupling"), especially at low oxygenation levels. We paced down spontaneous breathing to about 5 or 6breaths/min in 14 healthy subjects using device-guided breathing (DGB), and continuously monitored respiration, transcutaneous oxygen pressure ("oxygenation"), and skin capillary blood flow ("microflow") using a laser Doppler flowmeter.

Arterial Stiffness: Going a Step Beyond.

Interest in arterial stiffness has been fueled by the scientific and clinical implications of its "vicious cycle" relationship with aging and systolic blood pressure. In physical terms, stiffness is the slope of the relationship between an artery's distending pressure and its cross-sectional area or volume. Pulse wave velocity (PWV, in m/s), the most common arterial stiffness indicator, is usually measured by the foot-to-foot time and distance method and is proportional to [stiffness × area (or volume)]1/2 at a given pressure.

Effects of gravity-induced upper-limb blood pressure changes on wave transmission and arterial radial waveform.

Background: Local blood pressure (BP) changes induced by arm tilting may influence pressure wave transmission and reflection. We investigated the effects of upper-limb tilting on radial augmentation index (rAIx) and related central measures [aortic augmentation index (aAIx)].

Methods: In 45 volunteers (age 49 ± 19 years), supine brachial BP and radial artery waveforms were obtained by applanation tonometry with the dominant arm stretched and gently supported in three different positions: at the heart level, with the BP cuff 15 cm above heart level (approximately +30°), and 15 cm below heart level (-30°).

Blood pressure and heart period variability ratios derived from 24-h ambulatory measurements are predictors of all-cause mortality.

Objective: The linear relationship between blood pressure (BP) and heart rate (or period) over 24 h has been suggested to be a marker for neural regulation of the circadian variations in BP and heart rate. We investigated the predictive power of indices defined by the ratio between BP and heart period variability that is a known expression for such a relationship.

Methods: We analysed BP and heart rate data obtained by standard 24-h BP monitoring in 1246 hypertensive patients, 76 of whom died from all causes during 5-year follow-up.

Simple determination of the systolic-diastolic pressure relationship from blood pressure readings taken at different arm heights.

Objectives: The slope of the linear relationship between systolic blood pressure (SBP) and diastolic blood pressure (DBP) determined from 24-h ambulatory measurements incorporates clinical and prognostic information and is believed to reflect arterial properties. We evaluated the feasibility of determining a similar relationship using the gravity-induced brachial blood pressure (BP) variation in response to vertical cuff displacement with reference to the heart.

Methods: Nine consecutive BP readings were taken in the sitting position with arm postures stabilized by a mechanical support and with the cuff positioned at four different measured heights.

Blood pressure variation in response to changing arm cuff height cannot be explained solely by the hydrostatic effect.

Objective: To challenge the widely accepted explanation of hydrostatic effect for blood pressure (BP) variation in response to arm elevation by testing the hypothesis that SBP and DBP measurements in the same individual vary differently with cuff height, and to evaluate the potential deviation of these measurements from the value predicted by the hydrostatic theory.

Methods: Arm BP was measured in 37 individuals from the general population in the sitting position using a digital BP monitor. Measurements included nine consecutive BP readings at four cuff heights.

Effect of non-drug interventions on arterial properties determined from 24-h ambulatory blood pressure measurements.

Measures derived from the slope of the linear relationship between systolic and diastolic pressures obtained by 24-h ambulatory blood pressure (ABP) measurements incorporate clinical and prognostic information, and are believed to be vascular markers. Using post hoc analysis, we investigated potential changes of these 'slope-related measures' in three different studies conducted in hypertensive patients with before and after 24-h ABP measurements, and also evaluated the sensitivity of the results to the analysis method. Two interventional studies included 8-week device-guided breathing (DGB) exercised by 13 patients with uncontrolled blood pressure (BP), and a 6-month mineral potassium chloride-enriched diet administered to 20 elderly patients.