Heart Rate Variation Research Articles

Effect of spine frame on the changes in respiratory dynamics in prone patients under general anaesthesia- a prospective, observational study.

The prone position is one of the common surgical positions used in clinical practice. Manoeuvring patients from supine to a prone position can impact respiratory dynamics and result in haemodynamic variations. This study included 64 patients and was conducted after obtaining approval from the ethics committee and registration of the trial. The primary objective was to evaluate the changes in peak inspiratory pressure (PIP), plateau pressure (Pplat) and mean airway pressure (MAP) in patients undergoing surgery under general anaesthesia in the prone position with (Group S) and without (Group P) spine frame. The secondary objective was to evaluate and compare the variations in heart rate and blood pressure. On turning the patient prone, there was statistically significant increase in median PIP (Group S 4 cmH2O vs. Group P 0.5 cmH2O, P < 0.001), Pplat (Group S 3.5 cmH2O vs. Group P 1 cmH2O, P = 0.004) and dynamic compliance (Group S -5.513 vs. Group P -2.78, P < 0.004). Our study found that prone positioning with a spine frame led to a significantly greater increase in airway pressures and a decrease in dynamic compliance when compared to patients positioned prone without the spine frame.

Assessment of prognostic value of heart rate response to single deep breath in cases of acute myocardial infarction involving anterior wall or inferior wall within first 12 hours of admission

Introduction: The sympatho-vagal balance on the SA node produces beat to beat variation in heart rate which is markedly increased in normal subjects on deep breathing cycles. Heart rate variability testing gives an estimation of altered vagal-sympathetic balance and is a marker of low vagal tone on the heart. This study assesses a simple bedside test involving a single cycle of deep breathing to assess heart rate variability response. Methods: A prospective observational study was done from May 2018 to September 2018 in the department of cardiology in 52 subjects diagnosed as suffering from acute myocardial infarction. For this test, ECG recording in all limb leads was taken while the patient was asked to perform deep breathing for ten seconds. The difference between the maximum and minimum R-R interval was recorded as an index of heart rate variability. The patient was then followed up till discharge for improvement or deterioration in clinical condition. Results: Forty-one subjects (78.8%) had a heart variability response of less than 10 beats per minute and the rest eleven (20.2%) individuals had a variability response of &gt;10 beats per minute. Patients who had low heart rate variability (n=41) showed higher incidence of acute left ventricular failure (75%), arrhythmia (17.5%) as compared to patients who had normal heart rate variability. Conclusions: This test can serve as an inexpensive, feasible and bedside alternative to conventional methods and can be correlated with negative prognosis in patients with acute MI.

How restorative landscapes can benefit psychological and physiological responses: a pilot study of human–nature relationships in Sweden and Taiwan

Restorative landscapes provide people with the opportunity to experience nature. This pilot study aimed to determine whether cultural differences affect psychological and physiological responses to restorative landscapes. Two populations, one in Taiwan and one in Sweden, were experimentally compared by showing them photos of restorative landscapes from each country. The results showed that restorativeness was affected more by photos of the restorative landscape in Sweden than in Taiwan. The results showed that restorativeness in terms of psychological and physiological responses was affected. A significant variation in heart rate was observed between the populations: Taiwanese participants experienced higher heart rates when viewing unfamiliar and novel scenery when compared to Swedish participants. No significant differences between the populations were observed regarding attention capacity, working memory, and muscle tension. The psychological and physiological responses to the two countries’ distinctive restorative landscapes may have implications for designing such landscapes in urban green spaces.

The Heart-Brain Relationship:Cardio-Cognitive axis

The bidirectional communication between the heart and the brain, often referred to as the cardio-cognitive axis, plays a pivotal role in maintaining homeostasis and influencing overall health. The physiological basis of cardio-cognitive interactions lies in the intricate network of neural and hormonal pathways that facilitate communication between the heart and the brain. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate, blood pressure, and vascular tone, exerting profound effects on cognitive processes. For instance, the sympathetic activation during a stressful situation triggers the release of catecholamines, influencing attention, memory, and decision-making. Furthermore, the heart's intrinsic nervous system, known as the cardiac plexus, contributes to this bidirectional communication. Studies have shown that the heart can send signals to the brain, modulating emotional processing and cognitive functions. The phenomenon of heart rate variability (HRV), an index of the beat-to-beat variation in heart rate, has emerged as a valuable marker of this interaction. High HRV is associated with better cognitive performance and emotional regulation, emphasizing the importance of a dynamically responsive cardiovascular system. Disruptions in the cardio-cognitive axis can have detrimental consequences. Cardiovascular diseases (CVDs), such as hypertension and atherosclerosis, are known to impact cognitive function. Moreover, conditions like heart failure and arrhythmias contribute to cerebral hypoperfusion, exacerbating the risk of cognitive decline and dementia. Neurotransmitters and hormones released by the cardiovascular system also impact cognitive processes. For instance, catecholamines released during stress, such as epinephrine and norepinephrine, can influence attention and memory. The intricate interdependence between cardiovascular health and cognitive function underscores the importance of a holistic approach to well-being. This essay has explored the neuroanatomical, physiological, and psychological aspects of cardio-cognitive interactions, emphasizing the bidirectional relationships that shape human health. Further research in this interdisciplinary field is essential for developing integrated interventions that target both cardiovascular and cognitive domains, promoting a comprehensive approach to health and longevity.

Pattern of Autonomic Involvement in Adult Patients with Guillain Barre Syndrome in a Tertiary Hospital

Background: Guillain Barre Syndrome (GBS) is an acute post infectious immune mediated peripheral neuropathy with a marked variation in pathology, clinical presentation and prognosis. Autonomic dysfunction is one of the important manifestations of GBS which may lead to significant morbidity and mortality. Objective: The aim of the study is to assess the autonomic involvement, to determine its frequency and pattern of involvement in adult patients with GBS Methods: An observational, descriptive, cross sectional study was carried out in the Department of Neurology, BSMMU, Dhaka from March, 2015 to September, 2017. Total 43 patients of GBS and 35 apparently healthy controls were recruited as the study population. On the basis of nerve conduction study patients were classified into different groups: acute inflammatory demyelinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN) and acute motor sensory axonal neuropathy (AMSAN) and other variants. Disability status at the time of autonomic testing was measured by Hughes functional grading scale. The following tests of autonomic nervous system were performed in both patients and controls 1) resting heart rate and heart rate on changing posture (30: 15 ratio) 2) supine blood pressure and blood pressure on changing posture 3) heart rate response to valsalva maneuver 4) heart rate response to deep breathing and E: I ratio 5) sphincter disturbance by symptoms questionnaire. Results: The mean age of patients was 35±12 years (range18 to 65 years) and 58.1% were male. Around 88.4 % of patients showed some sort of autonomic dysfunction. Variation of heart rate by different maneuver like posture change, deep breathing and valsalva maneuver was found commonly. Among them 30:15 ratio was abnormal in majority of the patients (82.4%) followed by abnormal max-min HR/min (58.1%) and abnormal valsalva ratio (37.2%). Other abnormalities were postural hypotension (38.2%), sinus tachycardia (25.6%), hypertension (16.3%), hypotension (2.7%), sinus arrhythmia (4.7%), constipation (30%), urinary retention (7%) and urinary incontinence (4.7%). Conclusion: In this study different patterns of autonomic dysfunction was found in 88.4% of patients with GBS involving both sympathetic and parasympathetic components. The present study found no significant association between autonomic dysfunction and motor disability scores. Thus autonomic function assessment is essential in every patient with GBS in addition to motor &amp; sensory function. Bangladesh Medical Res Counc Bull 2022; 48(3): 174-179

0228 Investigating Application of Phase Contrast MRI to Study CSF Movement in Aging and Sleep Deprivation

Abstract Introduction The glymphatic system facilitates solute transport through the exchange of cerebral spinal fluid (CSF) and interstitial fluids using a brain-wide system of perivascular spaces. Such exchange is primarily active during sleep. Aging and sleep disruptions have been shown to decrease glymphatic clearance and increase risk of cognitive impairment. Here, we used phase contrast MRI (PC MRI) to measure CSF egress from the Aqueduct of Sylvius (AoS) as a marker of CSF circulation in the setting of sleep deprivation and aging. Methods Under approved IRB protocols six young adults (22±3 yo, 4F) underwent a night of full sleep and a night of sleep deprivation in a 3T Philips Ingenia Elition scanner with a 32-channel head coil. Additionally, six older adults (66±3 yo, 2F) were scanned using identical MRI protocol but only after full sleep. The PC MRI was a single slice acquisitions with 14 samples within a cardiac cycle. The slice was perpendicular to the AoS and care was taken to avoid any phase wrapping. All individuals also completed the General Practitioner’s assessment of cognition (GPCOG) in the morning prior to their scan. CSF velocity in cm/s was calculated from the phase data. Heart rate (HR) was recorded during the scan using a pulse-oximeter. Results CSF velocity was numerically lower after sleep deprivation (2.6±2.1 cm/s) than after a night of full sleep (3.1±2.0 cm/s) in young adults, but the difference was not significant. CSF velocity in the older adults was lower (2.0□0.5 cm/s, marginally significant at p = 0.10) than in young adults. HR in older adults (59±6) was significantly lower than the young adults under both conditions (full sleep: 68±4, sleep deprivation: (66±11) and, across all participants, HR was weakly correlated (r=-0.35) with CSF velocity. GPCOG was not significantly different across conditions or groups. Conclusion Although only marginally significant, CSF velocity in the AoS, measured by PC MRI is sensitive to HR variations and aging but not to sleep. Continued investigation with a larger sample size is underway to understand if these preliminary observations hold and if CSF velocity in the AoS is associated with glymphatic transport. Support (if any)

Parasympathetic autonomic dysfunction is more often evidenced than sympathetic autonomic dysfunction in fluctuating and polymorphic symptoms of "long-COVID" patients

Several disabling symptoms potentially related to dysautonomia have been reported in “long-COVID” patients. Unfortunately, these symptoms are often nonspecific, and autonomic nervous system explorations are rarely performed in these patients. This study aimed to evaluate prospectively a cohort of long-COVID patients presenting severe disabling and non-relapsing symptoms of potential dysautonomia and to identify sensitive tests. Autonomic function was assessed by clinical examination, the Schirmer test; sudomotor evaluation, orthostatic blood pressure (BP) variation, 24-h ambulatory BP monitoring for sympathetic evaluation, and heart rate variation during orthostatism, deep breathing and Valsalva maneuvers for parasympathetic evaluation. Test results were considered abnormal if they reached the lower thresholds defined in publications and in our department. We also compared mean values for autonomic function tests between patients and age-matched controls. Sixteen patients (median age 37 years [31–43 years], 15 women) were included in this study and referred 14.5 months (median) [12.0–16.5 months] after initial infection. Nine had at least one positive SARS-CoV-2 RT-PCR or serology result. Symptoms after SARS-CoV-2 infection were severe, fluctuating and disabling with effort intolerance. Six patients (37.5%) had one or several abnormal test results, affecting the parasympathetic cardiac function in five of them (31%). Mean Valsalva score was significantly lower in patients than in controls. In this cohort of severely disabled long-COVID patients, 37.5% of them had at least one abnormal test result showing a possible contribution of dysautonomia to these nonspecific symptoms. Interestingly, mean values of the Valsalva test were significantly lower in patients than in control subjects, suggesting that normal values thresholds might not be appropriate in this population.

A comparison of four common mathematical models to assess baroreflex sensitivity.

Different methods have been used to assess baroreflex gain in experiments where changes in the carotid sinus pressure or the arterial blood pressure using different techniques provoke a baroreflex response, usually a rapid variation of heart rate. Four mathematical models are most used in the literature: the linear regression, the piecewise regression, and two different four-parameter logistic equations: equation 1, Y = (A1-D1)/[1 + eB1(X - C1) ] + D1; equation 2, Y = (A2-D2)/[1 + (X/C2)B2 ] + D2. We compared the four models regarding the best fit to previously published data in all vertebrate classes. The linear regression had the worst fit in all cases. The piecewise regression generally exhibited a better fit than the linear regression, though it returned a similar fit when no breakpoints were found. The logistic equations showed the best fit among the tested models and were similar to each other. We demonstrate that equation 2 is asymmetric and the level of asymmetry is accentuated according to B2. This means that the baroreflex gain calculated when X = C2 is different from the actual maximum gain. Alternatively, the symmetric equation 1 returns the maximum gain when X = C1. Furthermore, the calculation of baroreflex gain using equation 2 disregards that baroreceptors may reset when individuals experience different mean arterial pressures. Finally, the asymmetry from equation 2 is a mathematical artifact inherently skewed to the left of C2, thus bearing no biological meaning. Therefore, we suggest that equation 1 should be used instead of equation 2.

The usability of daytime and night-time heart rate dynamics as digital biomarkers of depression severity.

Alterations in heart rate (HR) may provide new information about physiological signatures of depression severity. This 2-year study in individuals with a history of recurrent major depressive disorder (MDD) explored the intra-individual variations in HR parameters and their relationship with depression severity. Data from 510 participants (Number of observations of the HR parameters = 6666) were collected from three centres in the Netherlands, Spain, and the UK, as a part of the remote assessment of disease and relapse-MDD study. We analysed the relationship between depression severity, assessed every 2 weeks with the Patient Health Questionnaire-8, with HR parameters in the week before the assessment, such as HR features during all day, resting periods during the day and at night, and activity periods during the day evaluated with a wrist-worn Fitbit device. Linear mixed models were used with random intercepts for participants and countries. Covariates included in the models were age, sex, BMI, smoking and alcohol consumption, antidepressant use and co-morbidities with other medical health conditions. Decreases in HR variation during resting periods during the day were related with an increased severity of depression both in univariate and multivariate analyses. Mean HR during resting at night was higher in participants with more severe depressive symptoms. Our findings demonstrate that alterations in resting HR during all day and night are associated with depression severity. These findings may provide an early warning of worsening depression symptoms which could allow clinicians to take responsive treatment measures promptly.

A New Algorithm for Estimating a Noiseless, Evenly Sampled, Heart Rate Modulating Signal.

Heart rate variability (HRV) is commonly intended as the variation in the heart rate (HR), and it is evaluated in the time and frequency domains with various well-known methods. In the present paper, the heart rate is considered as a time domain signal, at first as an abstract model in which the HR is the instantaneous frequency of an otherwise periodic signal, such as with an electrocardiogram (ECG). In this model, the ECG is assumed to be a frequency modulated signal, or carrier signal, where HRV or HRV(t) is the time-domain signal which is frequency modulating the carrier ECG signal around its average frequency. Hence, an algorithm able to frequency demodulate the ECG signal to extract the signal HRV(t) is described, with possibly enough time resolution to analyse fast time-domain variations in the instantaneous HR. After exhaustive testing of the method on simulated frequency modulated sinusoidal signals, the new procedure is eventually applied on actual ECG tracings for preliminary nonclinical testing. The purpose of the work is to use this algorithm as a tool and a more reliable method for the assessment of heart rate before any further clinical or physiological analysis.

Assessment of cardiovascular autonomic dysfunction in untreated adult hypothyroid patients

Introduction and Aim: Hypothyroidism is an endocrine disorder with a high prevalence worldwide in the adult population. Due to the thyroid hormone’s widespread role in controlling metabolic processes to permissive action on the heart, patients with hypothyroidism suffer from a significant chance of acquiring cardiac autonomic dysfunction which further deteriorates the prognosis. Heart rate Variation analysis can be a possible way to detect this autonomic dysfunction early and may help in patient care. This study aims to assess Heart Rate Variability (HRV) parameters in untreated overt hypothyroid patients and compare the parameters of heart rate variability test with an age and sex-matched healthy control group. Materials and Methods: With the permission from the institutional ethics committee, 50 untreated hypothyroid patients are collected from the endocrine outpatient department and 50 healthy age, sex, and matched individuals are taken, maintaining proper inclusion and exclusion criteria. HRV analysis data is collected in both time and frequency domains in both groups and compared using statistical tools. Results: In our research, it is seen that compared to healthy control group, untreated hypothyroid patients have a significant alteration in the following parameters - SDNN (p&lt;0.005) and RMSSD (p&lt;0.009) in the time domain and LF (nu), LF (%), HF (%), LF/HF, HF (nu)[p&lt;0.05] in the frequency domain. Conclusion: Due to several alterations in HRV parameters indicating sympathovagal disbalance in the hypothyroid patients, it can be concluded that untreated hypothyroid patients are prone to develop cardiovascular autonomic dysfunction and HRV analysis can be a possible way to detect it early.

Chronic circadian disruption impairs cardiovascular rhythms and leads to kidney disease in mice

Shift workers have an increased risk of developing hypertension and reduced kidney function. Disruption of behavioral or environmental circadian rhythms increases cardiometabolic disease risk in humans and animals. We hypothesized that chronic circadian disruption (CCD) impairs cardiovascular rhythms and increases renal injury markers. Male C57BL/6J mice starting at 8-week of age were maintained under a normal light/dark cycle (12-h light, 12-h dark, control) or a CCD protocol (10-h light, 10-h dark, T20) with ad libitum food and water for 10 weeks. T20 mice gained significantly more body weight compared to control mice. Control mice showed a diurnal variation in food intake, while T20 mice had similar food intake during both light and dark phases with more food consumed in the light phase compared to control mice. Mean arterial pressure (MAP), heart rate (HR), and locomotor activity were measured by telemetry after 10 weeks of CCD. MAP between the light and dark periods was significantly different in control mice (12:12 LD), while T20 mice (10:10 LD) lacked diurnal variation (control 119±3 vs.101±2 mm Hg, dark vs. light, respectively, p&lt;0.001; T20 114±13 vs.113±12 mm Hg, dark vs. light, respectively, p=0.86; n=3-4). Control mice showed a diurnal variation in HR, whereas T20 mice did not show a light-dark difference (Control- 584±11 vs. 511±4 bpm, dark vs. light, respectively, p=0.001; T20- 537±14 vs. 526±5 bpm, dark vs. light, respectively, p=0.48; n=3-4). Dark phase HR was significantly decreased in T20 mice (p=0.01, control vs. T20). Control mice had a light-dark difference in activity, while T20 mice lacked diurnal variation in activity with significantly higher activity during the light phase (p=0.04, control vs. T20). Mice were placed in metabolic cages for urine collection during the light (control: ZT0-12; T20: ZT0-10) and dark (control: ZT12-0; T20: ZT10-0) phases. Urinary excretion of renal tubular injury markers albumin, neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1) were measured (ELISA). Control mice had significantly higher albumin and NGAL excretion in dark vs. light phases, while T20 mice lacked a significant diurnal pattern with significantly elevated albumin and NGAL during the light phase compared to control mice (albumin: control 1.00±0.23 vs. 0.09±0.05 ug/hr dark vs. light, p=0.04, control light vs. T20 light, p=0.04; NGAL: control 1410±223 vs. 89±58 pg/hr dark vs. light, p=0.02, control light vs.T20 light, p=0.04, n=4-6). CCD also blunted the diurnal rhythm of KIM-1 excretion (light cycle, p=0.04, n=3-6). The diurnal variation in sodium and potassium excretion was also lost in T20 mice. These results indicate that CCD impairs cardiovascular rhythms as well as diurnal excretion of electrolytes and renal injury markers, which may increase risk for kidney disease. P01HL136267, AHA 856877 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Relating emotions, psychophysiological indicators and context in public transport trips: Case study and a joint framework for data collection and analysis

This study proposes an experimental framework for collecting on-board data on users' emotions, psychophysiological indicators, and context, to characterize their experience in a granular, scalable, non-intrusive, and ecological way. To gather emotions data, clustering techniques are used to adapt Russell's circumplex model to a transport framework, allowing data to be collected on-board using a smartphone application. For psychophysiological indicators, a specially designed portable PCB (Biomonitor 2.0) is used to record heart rate, heart rate variation, skin temperature, and electrodermal activity with high frequency and fidelity. Context information is collected using ambient sensors and a smartphone application. A proof-of-concept case study is conducted on 44 engineering students traveling for 2.5 hours on various public transport modes in Santiago, Chile, including an autonomous vehicle. The results show that the framework is feasible, and that emotions data can be effectively related to granular records of psychophysiological indicators and context using a discrete choice model. This study sets a precedent for future research to incorporate new granular public transport user satisfaction indicators based on emotions inferred from psychophysiological data and detect causal factors related to users' physical, emotional, and cognitive state.

136 The effects of cannabidiol on libido and heart rate in stallions

Changes in the Agriculture Improvement Act of 2018 increased popularity of Cannabidiol (CBD) as a supplement. Exogenous CBD, derived from Cannabis Sativa L., binds to cannabinoid receptors in the endocannabinoid system. These receptors are located throughout the body, CB1 being prominent in the central nervous system and CB2 in the immune system. Physiological effects of CBD have been well researched but the effects on libido have not. Lack of libido or sexual drive can be detrimental to stallion breeding productivity. The use of CBD as a calming supplement in animals is increasing due to marketing strategies. The study objective was to evaluate libido and heart rate (HR) in stallions given a daily oral CBD supplement for 90d. Two-year old stallions (n = 7) were assigned to either Control (CON; n = 3) or Cannabidiol (CBD; n = 4) treatment groups. CBD was administered at 0.6mg/kg of BW/d, while CON was administered an equal volume of olive oil, as a placebo of similar nature. Treatments were top-dressed over morning feed. Horses were weighed every Monday with dosages recalculated accordingly. Data collections occurred 2x/wk during semen collections with an artificial vagina. Behaviors were previously defined, calmly called out and logged as they occurred. Observations included time spent licking a tease mare, time to erection, time to first mount, and time to ejaculation. A Polar® heart rate monitoring system linked to the KER® ClockItapp was usedto measure HR. Variations of HR included resting HR, teasing HR, mounting HR, step-off HR, and walk-off HR. Data was analyzed using a repeated measures ANOVA within R Statistical Program®(R Core Team, 2022). Results were considered significant at P ≤ 0.05. Throughout the duration all stallions exhibited normal sexual behavior, regardless of treatment. A treatment affect was not seen for licking time between CBD and CON (11.92s ± 3.76 and 0.32s ± 0.20 respectively). There was no difference between CBD and CON for time to erection (27.64s ± 6.84 and 22.9s ± 4.76 respectively). Time to first mount CBD stallions averaged 330.6s ± 23.04, CON stallions averaged 359.5s ± 25.51, with no effect of treatment. Time to ejaculation in CBD stallions was 356s ± 23.78 and 374s ± 24.84 in CON stallions. There were no differences in behaviors over time. There was a time x day effect for walk-off HR(P = 0.04), though this was significant in both groups. No other differences in HR occurred. Long-term use of CBD for young stallions was seen to not affect libido. However, supplementation may lower HR over time. The immediate and lasting response to CBD use in mature stallions and older aggressive stallions is needed to understand the effects of using these products.

Heart rate fragmentation in renovascular hypertensive rats

Although rapid oscillations of the heart rate (HR) are attributed to vagal modulation of the heart, a pattern of ultra-rapid HR variation has been named heart rate fragmentation (HRF). It is a recently proposed approach to evaluate sino-atrial instability characterized by the presence of numerous inflections points in a series of successive values of cardiac intervals. HRF is increased in aging and coronary diseases. Hypertension markedly alters HRV indices and might affect HRF as well. This study aimed to investigate the HRF in renovascular hypertension in rats. Wistar rats were anesthetized, and hypertension was surgically induced by partial constriction of the left renal artery with a silver clip with a 0.2 mm gap. In one kidney one clip (1K1C) hypertension model, the contralateral kidney was removed. In two kidneys one clip (2K1C) model, the contralateral kidney was kept intact. Sham-operated control rats underwent to same surgical procedures without receiving the clip around the renal artery. After 45 days (2K1C) or 60 days (1K1C), animals were instrumented with a catheter into the femoral artery, and on the following day, their arterial pressure (AP) was directly recorded without the effect of anesthesia. For HRF analysis, pulse interval (PI) series were generated and transformed into a sequence of symbols “-1,” “0,” or “1” when the difference between successive PI values (transitions) was negative, zero, or positive, respectively. Following, sequences of 4 consecutive symbols were classified according to the number of transitions. The total percentage of inflection points (PIP) and the percentage of sequences with zero (W0), one (W1), two (W2), or three (W3) inflection points were quantified. As expected, the arterial pressure increased in both groups of hypertension rats compared to control counterparts. All HRF indices were found similar in 1K1C hypertensive rats compared to their control counterparts. Nevertheless, in 2K1C hypertensive rats HRF was found to be lower than normotensive controls (PIP: 64±7 vs. 79±1% and W2: 30±1 vs. 39±1% in 2K1C and normotensive controls, respectively). In conclusion, high blood pressure itself does not affect HRF, although, depending on the model of hypertension used, HRF can be markedly impaired. The interpretation of these findings is challenging, and the high levels of angiotensin in the 2K1C model may affect cardiac pacemaker cells, making their action potentials more stable than unstable. However, the specific mechanisms by which this could happen still need to be studied. Funding Sources: FAPESP, CAPES and CNPq This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Measure by measure: Resting heart rate across the 24-hour cycle.

Photoplethysmography (PPG) sensors, typically found in wrist-worn devices, can continuously monitor heart rate (HR) in large populations in real-world settings. Resting heart rate (RHR) is an important biomarker of morbidities and mortality, but no universally accepted definition nor measurement criteria exist. In this study, we provide a working definition of RHR and describe a method for accurate measurement of this biomarker, recorded using PPG derived from wristband measurement across the 24-hour cycle. 433 healthy subjects wore a wrist device that measured activity and HR for up to 3 months. HR during inactivity was recorded and the duration of inactivity needed for HR to stabilise was ascertained. We identified the lowest HR during each 24-hour cycle (true RHR) and examined the time of day or night this occurred. The variation of HR during inactivity through the 24-hour cycle was also assessed. The sample was also subdivided according to daily activity levels for subset analysis. Adequate data was obtained for 19,242 days and 18,520 nights. HR stabilised in most subjects after 4 minutes of inactivity. Mean (SD) RHR for the sample was 54.5 (8.0) bpm (day) and 50.5 (7.6) bpm (night). RHR values were highest in the least active group (lowest MET quartile). A circadian variation of HR during inactivity was confirmed, with the lowest values being between 0300 and 0700 hours for most subjects. RHR measured using a PPG-based wrist-worn device is significantly lower at night than in the day, and a circadian rhythm of HR during inactivity was confirmed. Since RHR is such an important health metric, clarity on the definition and measurement methodology used is important. For most subjects, a minimum rest time of 4 minutes provides a reliable measurement of HR during inactivity and true RHR in a 24-hour cycle is best measured between 0300 and 0700 hours. Funding: This study was funded by Google.

Heart Rate Variation is The Clinical Sign Associated with The Deepest Plane of Anesthesia During Induction: The Novel Finding and Its Clinical Implications

Heart Rate Variation is The Clinical Sign Associated with The Deepest Plane of Anesthesia During Induction: The Novel Finding and Its Clinical Implications

The incremental significance of heart rate recovery as a predictor during exercise-stress myocardial perfusion SPECT imaging in individuals with suspected coronary artery disease.

Major adverse cardiac events (MACE) are more likely to occur when abnormal heart rate recovery (HRR). This study aimed to assess the incremental predictive significance of HRR over exercise stress myocardial perfusion single-photon emission computed tomography (MPS) results for MACE in individuals with suspected coronary artery disease (CAD). Between January 2014 and December 2017, we continually gathered data on 595 patients with suspected CAD who received cycling exercise stress MPS. HRR at 1, 2, 3, and 4 min were used as study variables to obtain the optimal cut-off values of HRR for MACE. The difference between the peak heart rate achieved during exercise and the heart rate at 1, 2, 3, and 4 min was used to calculate the HRR, as shown in HRR3. Heart rate variations between two locations in time, such as HRR2 min-1 min, were used to establish the slope of HRR. All patients were followed for a minimum of 4 years, with MACE as the follow-up goal. The associations between HRR and MACE were assessed using Cox proportional hazards analyses. Patients with MACE were older (P = 0.001), and they also had higher rates of hypertension, dyslipidemia, diabetes, abnormal MPS findings (SSS ≥ 5%), medication history (all P < 0.001), and lower HRR values (all P < 0.01). Patients with and without MACE did not significantly vary in their HRR4 min-3 min. The optimal cut-off of HRR1, 2, and 3 combined with SSS can stratify the risk of MACE in people with suspected CAD (all P < 0.001). HRR 1, 2, and 3 and its slope were linked to MACE in multivariate analysis, where HRR3 was the most significant risk predictor. With a global X2 increase from 101 to 126 (P < 0.0001), HRR3 demonstrated the greatest improvement in the model's predictive capacity, incorporating clinical data and MPS outcomes. HRR at 3 min has a more excellent incremental prognostic value for predicting MACE in patients with suspected CAD following cycling exercise stress MPS. Therefore, incorporating HRR at 3 min into known predictive models may further improve the risk stratification of the patients.

A comparative evaluation of dexmedetomidine and magnesium sulfate during awake fiber optic orotracheal intubation in patients scheduled for cervical spine surgeries: A prospective study

Background: Fiber optic intubation has become an integral part in management of anticipated difficult airways. Various anesthetic drugs have been used to assist awake fiber optic intubation (AFOI) for producing conscious sedation to provide a calm, cooperative, and responsive patient without respiratory depression for successful awake fibre optic intubation. Aims and Objectives: The aim of the present study was to compare the efficacy of dexmedetomidine and magnesium sulfate during awake fiber optic orotracheal intubation in patients scheduled for cervical spine surgeries. Materials and Methods: A randomized, prospective, and comparative study design was conducted in 60 patients in JAH group of hospitals. All patients were randomly divided into two groups: Group A (n=30) patients received dexmedetomidine (1 μg/kg) and Group B (n=30) patients received magnesium sulfate (40 mg/kg) in 100 ml normal saline over 10 min. The fiber optic orotracheal intubation was performed and primary outcome was level of sedation assessed using Ramsay sedation score. Other parameters of study included cough score and intubation score to compare intubating conditions. The secondary outcomes of study included variations in hemodynamic parameters heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and SPO2 during drug infusion at 2-min interval, immediately after intubation and every 10 min after intubation till 30 min. Results: Group A (Dexmedetomidine) had better sedation score, cough score, and intubation score with stable hemodynamic variables than Group B (Magnesium Sulphate) with statistically significant results. Conclusion: Patients receiving dexmedetomidine had better sedation providing more optimum conditions for AFOI with stable hemodynamic parameters and lesser adverse effects during the procedure than magnesium sulfate.

Nociception level response to calibrated stimulations in children: First assessment of the nociception level index in pediatric anesthesia

IntroductionIntraoperative monitoring of nociception has made great progress in adult anesthesia. However, pediatric data are scarce. The Nociception Level (NOL) is one of the most recent indexes of nociception. Its originality is that it provides a multiparametric assessment of nociception. In adults, NOL monitoring allowed lower perioperative opioid requirements, hemodynamic stability, and qualitative postoperative analgesia. So far, the NOL has never been used in children. Our objective was to validate the ability of NOL to provide a quantitative assessment of nociception in anesthetized children. MethodsIn 5–12 years old children anesthetized with sevoflurane and alfentanil (10 µg kg−1), before surgical incision, we performed three standardized tetanic stimulations (5 s, 100 Hz) of different intensities (10−30–60 mA) in a randomized order. NOL, heart rate, blood pressure and Analgesia-Nociception Index variations were assessed after each stimulation. ResultsThirty children were included. Data were analyzed with a covariance pattern linear mixed regression model. NOL increased after the stimulations (p < 0.05 at each intensity). NOL response was influenced by stimulation intensity (p < 0.001). Heart rate and blood pressure were barely modified by the stimulations. Analgesia-Nociception Index decreased after the stimulations (p < 0.001 at each intensity). Analgesia-Nociception index response was not influenced by stimulation intensity (p = 0.064). NOL and Analgesia-Nociception Index responses were significantly correlated (Pearson r = 0.47; p < 0.001). ConclusionsNOL allows a quantitative assessment of nociception under anesthesia in 5–12 years-old children. This study provides a solid basis for all future investigations on NOL monitoring in pediatric anesthesia. RegistrationNCT05233449.