Short-term cardiovascular measures for driver support: Increasing sensitivity for detecting changes in mental workload

Background: The effects of empagliflozin in addition to standard care, on day-to-day variability of self-measured home blood pressure (BP) and heart rate (HR) at home in patients with type 2 diabetes (T2DM) at high cardiovascular risk are not known. Method: We followed twenty-three consecutive T2DM patients (mean age: 69 years old, 12 men) to add 10 mg of empagliflozin once daily for three months. Home BP and HR were measured once every morning at home, using an oscillometric device. The variability of BP and HR were defined as the standard deviations (SD) of measurements which were performed on seven consecutive days. Results: For home blood pressure, empagliflozin significantly reduced systolic blood pressure (SBP) from 130±11 mmHg at baseline to 126±11 mmHg at the first week(1W) of the administration (P<0.05). SBP achieved the target home BP goal (125±11 mmHg) at the second week(2W) and was maintained during the study (P<0.01). As regards day-to-day variability of SBP, SD decreased from 7.3±3.5 mmHg at baseline to 6.7±2.5 mmHg at 1W (4W: 6.4±2.8 mmHg, 8W: 5.2±2.3 mmHg, P<0.05). In diastolic blood pressure (DBP), there was a significant reduction of SD compared with that at baseline (4.9±1.6 mmHg at baseline, 4W: 4.3±1.6 mmHg, 8W: 3.9±1.8 mmHg, 12W: 4.4±1.6 mmHg, P<0.05); however, there was no change of DPB (71±10 mmHg at baseline, 12W: 71±8 mmHg). Similarly, there was a decreasing trend in SD of HR (3.9±1.0 beats per minute (bpm) at baseline, 4W: 3.3±1.3 bpm, 12W: 3.1±1.3 bpm, P<0.1), although there was no significant change in HR (62±13 bpm at baseline, 12W: 61 ± 12 bpm). Conclusion: Empagliflozin tended to reduce the day-to-day variability of self-measured morning home BP and HR.

Lane changing poses a great threat to traffic safety in the work zone areas. This study aims to conduct an in-depth investigation of drivers' lane-changing behavior and to propose and verify the efficacy of an intelligent in-vehicle audio prompt through a driving simulator experiment. Forty-two participants, comprising 22 males (12 professional drivers and 10 normal drivers) and 20 females (10 professional drivers and 10 normal drivers), took part in the study. Three traffic density levels (20pcu/km, 40pcu/km, and 60pcu/km) and five locations (baseline, 250m, 500m, 750m, and 1000m) to release the audio prompt information were set to collect eye movement and driving behavior data. A multistage lane-changing process including the perception stage, preparation stage, and action stage was developed, and three types of variables, namely experiment variable, behavioral variable, and risk assessment variable, were defined. The results indicated that the audio prompt set at 500m, 750m, and 1000m could noticeably improve lane-changing behavior (i.e., triggering lane changes more in advance and providing drivers with more preparation time). However, the audio prompt set at 250m upstream of the work zone showed limited efficacy, which is not recommended in practical application. Male drivers and professional drivers performed better during lane changing, and they had a more active observation of the surrounding environment and tended to adopt safer vehicle operations than their counterparts. A high traffic density could increase the collision risks even if drivers had made sufficient preparations, while in low traffic density conditions, drivers who failed to change lanes tended to apply hard braking when they approached the work zone.

Heart rate (HR) variability and arterial blood pressure (BP) variability were analysed as functions of foetal breathing movements (FBMs) by means of power spectral analysis in seven foetal lambs during the third trimester of gestation. No evidence of FBM-related changes, either in mean HR, mean systolic or diastolic arterial pressures, were found. Mean arterial pulse pressure, HR variability, and BP variability increased during FBMs. The increase in BP variability occurred at frequencies higher than 0.35 Hz, i.e. those of FBMs. The increase in HR variability occurred at 0.07-1.0 Hz, i.e. at every frequency band except the lowest one. Thus, the increase in HR variability was not frequency-specifically related to FBMs. During FBMs the periodic variability of HR at frequencies > 0.35 Hz was only 10% of total HR variability. We suggest that the FBM-related changes of BP variability may be mediated by direct peripheral, hydraulic mechanisms. HR changes involve autonomic control systems: the vagal component of baroreflex seems to be relatively insensitive, whereas the very slow vasomotor component of HR variability is dominant.

Ambulatory blood pressure pattern in elderly athletes.

In this issue of The Journal of Clinical Hypertension, Grillo and colleagues1 demonstrated that blood pressure (BP) variability (BPV) as determined by ambulatory BP monitoring (ABPM) was greater for patients with primary aldosteronism and those with essential hypertension in comparison to patients with no hypertension. The clinical implications of their findings are significant as they demonstrate another important subgroup of patients who are at increased risk for target organ damage from BPV. In addition, these investigators provide more evidence of the clinical utility of ABPM in diagnosing BPV in at-risk patient populations. There is growing evidence from both short-term (24-hour) and long-term assessments that BPV is associated with a higher risk for stroke, myocardial infarction, and kidney disease in patients with essential hypertension.2, 3 A study of 169 hypertensive patients showed that short-term BPV was associated with increased risk for left ventricular hypertrophy, increased carotid artery intimal-media thickness, and albuminuria, and prognosis was related to the number of sites of target organ damage.4 Similarly, Tatasciore and colleagues5 demonstrated increased carotid intima-media thickness and left ventricular mass in patients with greater BPV. These findings were specific for systolic BPV while awake and were independent of mean awake BP levels.5 Long-term BPV with measurements spanning weeks, months, or years is typically assessed by patient home BP monitoring or clinic BP measurements.2 As with short-term BPV, long-term BPV has also been associated with an increased risk of target organ damage in patients with essential hypertension.2 In multiple studies, patients with greater long-term variability in their home BP measurements had a higher prevalence of cardiovascular and kidney damage2, 6 and a higher risk of cardiovascular events and mortality.2, 7-10 Significantly compounding the cardiovascular risk of BPV, hypertensive patients with primary aldosteronism appear to be even more vulnerable to target organ damage compared with patients with only essential hypertension. A study of cardiovascular outcomes compared patients with primary aldosteronism from solitary adenomas or bilateral adrenal hyperplasia with patients who had essential hypertension.11 These cardiovascular events included stroke, myocardial infarction, atrial fibrillation, and echocardiographic and electrocardiographic evidence of left ventricular hypertrophy.11 The investigators found that patients with primary aldosteronism experienced more cardiovascular events than patients with essential hypertension.11 Importantly, the excess cardiovascular event burden in the primary aldosteronism patient group was independent of BP control.11 In a subsequent study, Catena and colleagues12 showed that the prevalence of cardiovascular events was significantly greater in a group of patients with primary aldosteronism (35%) than in patients with essential hypertension (11%). This excess cardiovascular complication burden was also independent and out of proportion to the patient's BP.12 Although both of these studies did not specifically evaluate BPV, it is certainly possible that the findings of Grillo and colleagues, which implicated BPV and target organ damage, is a causative factor for the increased cardiovascular events found in patients with primary aldosteronism. Given the increased risk of target organ damage associated with BPV, it may become critical that clinicians now consider another metric to assess whether their hypertensive patients are receiving optimal antihypertensive treatment; it is now not enough to just achieve a BP below a recommended threshold. A substantial body of clinical research has demonstrated that BPV is a significant causative factor in target organ damage even when BP is adequately controlled with medical therapies. For patients with primary aldosteronism who are already more vulnerable to target organ damage than patients with essential hypertension, BPV may be an even more important factor to measure. As Grillo and colleagues demonstrated in this study, ABPM is a well-suited and useful tool to assess BPV in patients with primary aldosteronism. Currently, the use of ABPM is limited and typically confined to the diagnosis of white-coat hypertension, episodic hypertension, resistant hypertension, and hypotensive symptoms while taking antihypertensive medications and autonomic dysfunction.13-15 However, we suggest that ABPM also be considered as a tool to evaluate the extent of BPV in patients with primary aldosteronism and to determine the effectiveness of an antihypertensive regimen. Finally, the authors discuss potential mechanisms for BPV. We are left concluding that there is much more to learn, including whether the fluctuations in BP are incurring injury or simply reflecting an aspect of target organ changes. Does the fact that one finds BPV in patients with primary aldosteronism offer any clues? Certainly volume expansion is a mediator of the increase in BP in primary aldosteronism and it would seem unlikely that volume per se would vary enough to account for the BPV. A volume-expanded state, however, could sensitize BP to changes in, for example, sympathetic tone. It would be interesting to know how much BPV might decrease following removal of an adrenal tumor that produced aldosterone. An underlying role for aldosterone in the development of hypertensive states as well as hypertensive complications seem to continually widen.

To investigate whether Type 2 diabetic patients exhibit characteristic patterns of circadian variation in plasma levels of catecholamines, blood pressure (BP) and heart rate variability (HRV). Ten Type 2 diabetic and eight control in-patients were studied. Blood for catecholamine measurement was collected every 4 h, and non-invasive ambulatory BP and heart rate were monitored throughout the day. HRV was determined using frequency domain methods. Diabetic patients showed a different pattern of circadian variation in BP and HRV from that of controls, the diurnal-nocturnal differences (D-N) being significantly smaller. The mean 24-h HRV levels were reduced in diabetic subjects. The mean 24-h plasma noradrenaline level of 1.36 +/- 0.12 nmol/l in diabetic patients was significantly lower than the 2.03 +/- 0.20 nmol/l in controls (P < 0.01). In contrast, no significant difference in adrenaline levels was observed. The mean 24-h plasma noradrenaline level demonstrated a significant positive correlation with D-N in systolic BP (r = 0.49, P = 0.0153). The present study demonstrated distinctive patterns of circadian variation in plasma noradrenaline level, BP and HRV in Type 2 diabetic patients, associated with an abnormal circadian pattern of sympathovagal modulation.

Objective: Seasonal blood pressure (BP) changes has been described in clinic BP. Few studies have examined the seasonal variation in BP and BP variability, assessed by 24-hour ambulatory blood pressure monitoring (ABPM) and it remains uncertain whether the seasonal trend differs between young and elderly hypertensive patients. Design and Method: A total of 1028 untreated essential hypertensive patients (mean age 52 ± 14 years) who underwent 24-hour ABPM between January 2009 and April 2013 were enrolled. Patients were divided into young (age ≤ 70 years, n = 927) and elderly (age > 70 years, n = 101) groups. Results: Compared to elderly group, young age group had higher clinic, 24-hour, daytime and night-time diastolic BP (DBP), higher clinic, 24-hour and daytime heart rate (HR), higher 24-hour and daytime HR variability (HRV), lower night-time systolic BP (SBP) and daytime SBP variability. In young age group, significant seasonal variation of clinic DBP and daytime SBP variability with a peak in autumn, and nighttime DBP and HR with a peak in spring and the increased prevalence of non-dippers in summer were observed. On the other hand, elderly group demonstrated seasonal variation of clinic, 24-hour, daytime and nighttime HR with a peak in autumn, daytime DBP with a peak in winter and night-time SBP variability with a peak in summer. Conclusions: There was an apparent seasonal variation of DBP, HR and SBP variability in both young and elderly hypertensive patients. However, elderly patients showed more pronounced seasonal change in HR compared to younger patients.

sponsorship: The European Union (HEALTH-F7-2011-278249 EU-MASCARA, HEALTH-F7-305507 HOMAGE and the European Research Council Advanced Researcher Grant 294713 EPLORE) and the Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium (G.0881.13 and G.0880.13) currently support the Studies Coordinating Centre (Leuven, Belgium). (European Union|HEALTH-F7-2011-278249 EU-MASCARA, European Union|HEALTH-F7-305507 HOMAGE, European Union (European Research Council)|294713 EPLORE, Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium|G.0881.13, Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium|G.0880.13)

Contribution of the renin-angiotensin and kallikrein-kinin systems to short-term variability of blood pressure in two-kidney, one-clip hypertensive rats

BackgroundBlood pressure (BP) variability can be evaluated by 24-hour ambulatory BP monitoring (24h-ABPM), but its concordance with results from finger BP measurement (FBPM) has not been established yet.ObjectiveThe aim of this study was to compare parameters of short-term (24h-ABPM) with very short-term BP variability (FBPM) in healthy (C) and diabetic-hypertensive (DH) subjects.MethodsCross-sectional study with 51 DH subjects and 12 C subjects who underwent 24h-ABPM [extracting time-rate, standard deviation (SD), coefficient of variation (CV)] and short-term beat-to-beat recording at rest and after standing-up maneuvers [FBPM, extracting BP and heart rate (HR) variability parameters in the frequency domain, autoregressive spectral analysis]. Spearman correlation coefficient was used to correlate BP and HR variability parameters obtained from both FBPM and 24h-ABPM (divided into daytime, nighttime, and total). Statistical significance was set at p < 0.05.ResultsThere was a circadian variation of BP levels in C and DH groups; systolic BP and time-rate were higher in DH subjects in all periods evaluated. In C subjects, high positive correlations were shown between time-rate index (24h-ABPM) and LF component of short-term variability (FBPM, total, R = 0.591, p = 0.043); standard deviation (24h-ABPM) with LF component BPV (FBPM, total, R = 0.608, p = 0.036), coefficient of variation (24h-ABPM) with total BPV (FBPM, daytime, -0.585, p = 0.046) and alpha index (FBPM, daytime, -0.592, p = 0.043), time rate (24h-ABPM) and delta LF/HF (FBPM, total, R = 0.636, p = 0.026; daytime R = 0,857, p < 0.001). Records obtained from DH showed weak positive correlations.Conclusions Indices obtained from 24h-ABPM (total, daytime) reflect BP and HR variability evaluated by FBPM in healthy individuals. This does not apply for DH subjects.

Strategic Highway Research Program 2 (SHRP 2) Reliability Project L07, Identification and Evaluation of the Cost-Effectiveness of Highway Design Features to Reduce Nonrecurrent Congestion, provided (1) general guidance on the range of design elements that could be used by transportation agencies to improve travel time reliability and reduce nonrecurrent congestion on urban freeways and (2) the Analysis Tool for measuring operational and safety effectiveness and calculating a life-cycle benefit–cost value. This value can be used to support decision making about the possible use of individual treatments to address actual nonrecurrent traffic conditions. The tool is a Visual Basic for Applications (VBA) interface overlaying a Microsoft-based Excel 2007 spreadsheet. Analysts can input data about a highway such as geometrics, volumes, and crash totals, and the tool computes delay and reliability indicators resulting from various design treatments and translates those results into life-cycle costs and benefits. For the safety-effectiveness analysis, a new relationship between safety and congestion was explored, and a mathematical model was developed to quantify crash frequency at various levels of traffic density. This supplemental report presents the research findings on the effort to further develop and refine the original safety and congestion relationship model using two additional independent freeway data sets. The results of this additional research confirmed the graphical relationship between crash frequency and traffic density developed in the original research. The crash rate on urban freeways varies with traffic density in a U-shaped curve. The lowest crash rates occurred at medium traffic densities, with slightly higher crash rates (single-vehicle- dominant) recorded at lower traffic densities and much higher crash rates recorded at higher traffic densities (multiple-vehicle-dominant). Therefore, if a design treatment is effective in reducing nonrecurrent congestion conditions at higher levels of service, it should also be effective in reducing crashes, resulting in a safety benefit.

The increasing use of ambulatory blood pressure monitoring (ABPM) devices in the investigation of hypertension has allowed detailed study of the circadian rhythm of blood pressure variability, the assessment of resistant hypertension, and the syndrome of “white coat” hypertension. The relevance of ABPM to target-organ damage and the complications of hypertension, such as heart attacks and strokes, has only recently gained prominence. There are more than 30 cross-sectional studies that have linked ABPM to hypertensive target-organ damage, including left ventricular hypertrophy (LVH),1 2 microalbuminuria,3 hypertensive retinal changes, and cerebrovascular disease.4 The majority of these studies have consistently reported that patients with an absent or reduced fall in blood pressure at night (referred to as “nondippers”) have more severe target-organ damage, including LVH5 and cerebrovascular disease,4 6 when compared with patients who demonstrate a normal nocturnal fall in blood pressure. For example, Verdecchia et al,7 in a prospective cohort of over 1100 hypertensive patients, reported higher mortality rates both in nondippers and “reverse dippers” and higher cardiovascular morbidity rates in female nondippers compared with dippers.8 In addition, Yamamoto et al9 recently reported that progressive cerebrovascular disease, including silent ischemic lesions and symptomatic stroke, was associated with a reduced nocturnal blood pressure fall in patients with a history of lacunar infarction. In a cross-sectional study of patients admitted with acute stroke (ictus <12 hours), Lip at al10 reported that such patients could generally be classed as nondippers, with higher blood pressures recorded using ABPM (but not using casual manual measurements) in black/Afro-Caribbean patients and also in patients with hemorrhagic stroke. These studies therefore suggest the potential usefulness of ABPM in epidemiological, cohort, or cross-sectional studies and the assessment of ethnic differences, stroke subtypes, and prognosis. A nondipper status …

Objectives: Anemia increases preload, reduces afterload resulting in increase in cardiac output. Viscosity of blood is determined by the amount of hemoglobin (Hb) that affects blood pressure (BP) and causes arterial stiffness. Anemia can lead to drastic changes in BP, including, short- and long-term variability in BP which have been recognized recently as important risk factors for development and progression of vascular events. Continuous beat-to-beat BP variability (BPV) captures the intricacies of BP dynamics which are not otherwise collected by intermittent BP monitoring. Blood Pressure Variability is however defined as a progression of variation with time, and hence, the variability is measured over 5 min and can be associated with other markers such as Hb and anemia status. Materials and Methods: Autonomic function testing including assessment of beat-to-beat BPV, heart rate variability, and galvanic skin response (GSR) was performed using the human non-invasive BP nano system and lab chart software. Results: Significant variability in beat-to-beat BP specially in systolic pressure ( P = 0.00001), heart rate variability ( P = 0.0014), and GSR ( P = 0.003) were observed. Conclusion: Beat-to-beat BP monitoring can be used as a reliable indicator of altered autonomic activity in anemia.

Dissociation between ACE activity and autonomic response to ACE inhibition in patients with heart failure

Characterisation of cardiac autonomic function in multiple sclerosis based on spontaneous changes of heart rate and blood pressure