Transfer function analysis of heart rate variability in response to water intake: correlation with gastric myoelectrical activity

Laterality of blood perfusion in the lower extremities after drinking saline at different temperatures

Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, there is still a lack of relevant research on whether there are left and right differences in these SkBF change. In the current study, a total of 60 subjects were recruited. Skin blood perfusion of the bilateral lower extremities was recorded simultaneously before and after drinking saline of different temperatures saline by using Laser Doppler flowmetry (LDF). The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed. The results indicated that after drinking saline, the laterality index of SkBF at the lower extremities was different and the laterality index changes of SkBF were mainly reflected in the frequency interval V (0.4-1.6 Hz). There was a weak negative correlation between the laterality index of endothelial NO-dependent component and change rate of root mean square of successive differences (RMSSD) after drinking 4 °C saline. However, after drinking 30 °C saline, there was a weak positive correlation between neurogenic component and RMSSD The distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality.

A system theory based digital model for predicting the cumulative fluid balance course in intensive care patients

Background: Surgical interventions can cause severe fluid imbalances in patients undergoing cardiac surgery, affecting length of hospital stay and survival. Therefore, appropriate management of daily fluid goals is a key element of postoperative intensive care in these patients. Because fluid balance is influenced by a complex interplay of patient-, surgery- and intensive care unit (ICU)-specific factors, fluid prediction is difficult and often inaccurate. Methods: A novel system theory based digital model for cumulative fluid balance (CFB) prediction is presented using recorded patient fluid data as the sole parameter source by applying the concept of a transfer function. Using a retrospective dataset of n = 618 cardiac intensive care patients, patient-individual models were created and evaluated. RMSE analyses and error calculations were performed for reasonable combinations of model estimation periods and clinically relevant prediction horizons for CFB. Results: Our models have shown that a clinically relevant time horizon for CFB prediction with the combination of 48 h estimation time and 8-16 h prediction time achieves high accuracy. With an 8-h prediction time, nearly 50% of CFB predictions are within ±0.5 L, and 77% are still within the clinically acceptable range of ±1.0 L. Conclusion: Our study has provided a promising proof of principle and may form the basis for further efforts in the development of computational models for fluid prediction that do not require large datasets for training and validation, as is the case with machine learning or AI-based models. The adaptive transfer function approach allows estimation of CFB course on a dynamically changing patient fluid balance system by simulating the response to the current fluid management regime, providing a useful digital tool for clinicians in daily intensive care.

Hydration Influence on the Autonomic Recovery of the Coronary Diseases Patient: Geometric Indices Analysis

Purpose: To evaluate the recovery period of autonomic modulation, through geometric indices of heart rate variability (HRV), on coronary artery disease (CAD) patients submitted to a cardiovascular rehabilitation session (CR), associated with hydration. Methods: Thirty male participants of a CR program, diagnosed with CAD were submitted to the control (CP) and hydration protocol (HP) characterized by a CR session. Only during HP were the participants given 8 equal portions of water. The water amount was determined through the hydric loss measured at the CP. During the protocols, the heart rate was measured beat-by-beat at rest (5-10 minutes[M1]) and at recovery (0-5 minutes [M2], 5-10 minutes [M3], 15-20 minutes [M4], 25-30 minutes [M5], 40-45 minutes [M6], 55-60 minutes [M7]) for the HRV analysis, performed by the geometric indices: TINN, RRTRI, SD1, SD2 and SD1/SD2 ratio. Results: Statistically significant differences were observed between the protocols (SD1, p_value = 0.022), moments (TINN, p_value = 0.001; SD1, p_value = 0.019; SD2, p_value = 0.001; SD1/SD2, p_value = 0.001) and moments vs. protocol interaction (SD1, p_value = 0.019). The SD1 index pointed to acceleration of parasympathetic recovery in the first minutes after exercising (HP recovery after M3 [86.07 ± 32.31%] vs. CP recovery after M5[86.43 ± 24.56]) and increase in global variability (TINN-HP remained increased in longer, until M5 (M1 83.10 ± 55.76 ms to M5 116.82 ± 67.54 ms) vs. CP that remained increased for a short time, until M2 (M1 77.93 ± 68.56 ms to M2 134.82 ± 56.08 ms). Conclusions: In CAD patients, hydration promoted a more efficient recovery on parasympathetic autonomic modulation and increased the global HRV in the recovery period.

Biosensor-Assisted Method for Abdominal Syndrome Classification Using Machine Learning Algorithm

The digestive system is one of the essential systems in human physiology where the stomach has a significant part to play with its accessories like the esophagus, duodenum, small intestines, and large intestinal tract. Many individuals across the globe suffer from gastric dysrhythmia in combination with dyspepsia (improper digestion), unexplained nausea (feeling), vomiting, abdominal discomfort, ulcer of the stomach, and gastroesophageal reflux illnesses. Some of the techniques used to identify anomalies include clinical analysis, endoscopy, electrogastrogram, and imaging. Electrogastrogram is the registration of electrical impulses that pass through the stomach muscles and regulate the contraction of the muscle. The electrode senses the electrical impulses from the stomach muscles, and the electrogastrogram is recorded. A computer analyzes the captured electrogastrogram (EGG) signals. The usual electric rhythm produces an enhanced current in the typical stomach muscle after a meal. Postmeal electrical rhythm is abnormal in those with stomach muscles or nerve anomalies. This study considers EGG of ordinary individuals, bradycardia, dyspepsia, nausea, tachycardia, ulcer, and vomiting for analysis. Data are collected in collaboration with the doctor for preprandial and postprandial conditions for people with diseases and everyday individuals. In CWT with a genetic algorithm, db4 is utilized to obtain an EGG signal wave pattern in a 3D plot using MATLAB. The figure shows that the existence of the peak reflects the EGG signal cycle. The number of present peaks categorizes EGG. Adaptive Resonance Classifier Network (ARCN) is utilized to identify EGG signals as normal or abnormal subjects, depending on the parameter of alertness (μ). This study may be used as a medical tool to diagnose digestive system problems before proposing invasive treatments. Accuracy of the proposed work comes up with 95.45%, and sensitivity and specificity range is added as 92.45% and 87.12%.

Uncoupling VOR and vestibuloautonomic retention to Coriolis acceleration training in student pilots and control subjects

PURPOSE

Explore the different vestibular physiologic response retention patterns after Coriolis acceleration training in student pilots and extend the results for use with Chinese astronauts in the future.

METHODS

Twelve healthy control male subjects were screened from males familiar with vestibular training and who physically resembled the astronauts. Fourteen student pilots were selected from 23 participants by rotational vestibular function tests. All subjects were exposed to five-day continuous or intermittent Coriolis acceleration training. Subjective motion sickness (MS) symptom scores, electrocardiography, electrogastrography (EGG), post-rotatory nystagmus and renin-angiotensin system responses were measured before, during and after rotational vestibular function tests at different times after vestibular training.

RESULTS

Subjects could tolerate 10 min or 15 min of vestibular with mild MS symptoms. Retention of vestibular autonomic responses (retention of MS symptom scores, heart rate variability, power density of EGG, variations in levels of arginine vasopressin) were approximately 1 week for control subjects and approximately 5 weeks for student pilots. Decreases in slow-phase velocity of post-rotatory nystagmus were maintained for 14 weeks for control subjects and 9 weeks for student pilots.

CONCLUSIONS

Retention of the vestibulo-autonomic reaction after vestibular training was different for control subjects and student pilots. All parameters related to autonomic responses could be maintained at low levels after vestibular training for approximately 1 week for control subjects and approximately 5 weeks for student pilots. Uncoupling patterns between post-rotatory nystagmus and the vestibulo-autonomic reaction may be helpful in the design of clinical rehabilitation plans for balance-disorder patients and for exploration of artificial gravity in future space missions.

Gastric myoelectrical activity in patients with inflammatory bowel disease

Aim: Inflammatory bowel disease is characterized by the presence of gastrointestinal motility disturbances; however alterations in the gastric myoelectrical activity have not been characterized. In this study we have recorded the gastric myoelectrical activity in patients with ulcerative colitis (UC) and Crohn's disease (CD) during their clinical remission. Materials and Methods: Gastric activity was assessed using electrogastrography (EGG) in patients with UC (n = 60), CD (n = 40) and healthy controls (n = 40). In each case, their response to water load test, as well as the dominant frequency (DF), dominant power (DP) and the power ratio (PR) of the electrical activity were recorded. Results: In healthy controls, the resting DF was 2.57 ± 1.05 cycles per minute (cpm), which decreased after water ingestion (2.34 ± 0.99 cpm; P = 0.001). Compared to healthy controls, patients with UC had low resting DF (bradygastria) (2.57 ± 1.05 vs. 1.86 ± 1.28 cpm; P = 0.01). The change in DF after water ingestion was insignificant in patients with UC and CD. Post-water ingestion, healthy controls exhibited an increase in the DP as compared to the resting state, (7.1 [2.93, 102.56] vs. 15.94 [3.92, 133.41] µV²; P = 0.02). Patients with UC (1.26 [0.14, 9.83] vs. 3.27 [0.61, 42.12] µV²) and CD (2.54 [0.44, 47.06] vs. 15.8 [0.1, 126.68] µV²) also showed a significant increase in the DP post-water ingestion. Conclusions: Patients with ulcerative colitis have altered resting gastric myoelectrical activity during the remission phase of the disease.

The effects of carbonated water upon gastric and cardiac activities and fullness in healthy young women

Although previous reports suggested that carbonated water drinking was effective against gastrointestinal symptoms, there is little information about the effects of carbonated water on gastric and appetite sensation. We therefore investigated the effect of carbonated water on short-term fullness with respect to gastric and cardiac responses in 19 healthy young women. Each subject was tested on three separate days at approximately 9 a.m. after an overnight fast. Gastric motility, evaluated by electrogastrography (EGG) and heart rate (HR), was measured for 20 min in the fasting state and 40 min after ingestion of water. Preloads consisted of an equivalent amount (250 mL) of water (W) or carbonated water (CW) and no drinking (blank). Fullness scores were measured using visual analog scales. To determine gastric motility, we assessed the component of bradygastria (1-2 cycles/min [cpm]), normogastria (2-4 cpm), tachygastria (4-9 cpm), and dominant frequency of the EGG power spectrum. After ingestion of CW, significant increases in fullness scores were observed compared with W. All postprandial EGG powers were significantly greater than preprandial, but no group difference was found. However, a dominant frequency tended to shift toward a lower band after ingestion of W. A significantly higher HR was found following consumption of CW as opposed to W. Multiple regression analysis revealed that increased HR was a significant variable contributing to the variances in fullness after ingestion of CW at 40 min. Our data suggest that CW may induce a short-term, but significant, satiating effect through enhanced postprandial gastric and cardiac activities due possibly to the increased sympathetic activity and/or withdrawal of parasympathetic activity.

Respiratory sinus arrhythmia as an index of vagal activity during stress in infants: respiratory influences and their control

Respiratory sinus arrhythmia (RSA) is related to cardiac vagal outflow and the respiratory pattern. Prior infant studies have not systematically examined respiration rate and tidal volume influences on infant RSA or the extent to which infants' breathing is too fast to extract a valid RSA. We therefore monitored cardiac activity, respiration, and physical activity in 23 six-month old infants during a standardized laboratory stressor protocol. On average, 12.6% (range 0–58.2%) of analyzed breaths were too short for RSA extraction. Higher respiration rate was associated with lower RSA amplitude in most infants, and lower tidal volume was associated with lower RSA amplitude in some infants. RSA amplitude corrected for respiration rate and tidal volume influences showed theoretically expected strong reductions during stress, whereas performance of uncorrected RSA was less consistent. We conclude that stress-induced changes of peak-valley RSA and effects of variations in breathing patterns on RSA can be determined for a representative percentage of infant breaths. As expected, breathing substantially affects infant RSA and needs to be considered in studies of infant psychophysiology.

The influence of oral water load on energy expenditure and sympatho-vagal balance in obese and normal weight women

INTRODUCTION

Oral water load may increase the energy expenditure (EE) by stimulation of sympathetic dependent thermogenesis. Thus, drinking of water may be helpful in weight reduction. The aim of the study is to assess the influence of water load on energy expenditure and sympathetic activity in obese and normal weight women.

MATERIAL AND METHODS

Forty-five women were included. Energy expenditure was measured twice, in the morning and after oral water load, by the indirect calorimetric method. The heart rate variability parameters low frequency (LF), high frequency (HF), LF/HF index, standard deviation of normal RR intervals (SDNN) and root mean square difference among successive RR normal intervals (rMSSD) were used for the indirect assessment of the sympatho-vagal balance.

RESULTS

Resting energy expenditure (REE) was significantly higher in obese than in normal weight women (1529 ±396 kcal/day vs. 1198 ±373 kcal/day; p = 0.02). In both study groups after water load EE increased significantly (by 20% and by 12%, corresponding to 8.6 kcal/h and 5.2 kcal/h respectively), while, LF/HF index increased simultaneously. The increase of energy expenditure (EE) did not exceed the energetic cost of water heating, from room to body temperature - 15 kcal/1000 ml. There was no correlation between changes of energy expenditure (EE) and heart rate variability (HRV) parameters.

CONCLUSIONS

The increase of EE induced by water load is mostly related to the heating of the consumed water to body temperature. The assessment of autonomic balance by means of standard HRV indices had been found insufficient for detection of actually operating mechanisms.

QUANTIFICATION OF RESPIRATORY SINUS ARRHYTHMIA USING HILBERT–HUANG TRANSFORM

To investigate whether the first intrinsic mode function, obtained from Hilbert–Huang transform (HHT), of heart rate variability is respiratory related. Electrocardiogram and chest circumference signals were recorded from 10 healthy subjects at supine rest. The HHT was applied to both R-R interval and chest circumference signals to figure out their first intrinsic mode functions (C1RR and C1RESP, respectively) from which the instantaneous amplitude, phase, and frequency were calculated. Although the instantaneous amplitudes and frequencies of C1RR and C1RESP were variable, linear regression analysis indicated a phase lock between C1RR and C1RESP. Intake of 500 ml water significantly elevated the amplitude ratio of C1RR to C1RESP; however, the phase difference of C1RR to C1RESP was still unchanged. The data indicate that the first intrinsic mode function of heart rate variability is respiratory related and may be equivalent to respiratory sinus arrhythmia. As compared to fast Fourier transform, HHT of respiratory sinus arrhythmia provides a comparative spatial measurement with a much higher temporal resolution.

Gastric tone, volume and emptying after implantation of an intragastric balloon for weight control

BACKGROUND

The intragastric balloon, filled with air or liquid is used before elective bariatric surgery because its efficacy is limited. This might be the consequence of altered gastric functions. Therefore, we aimed to investigate, in an animal model, the changes in gastric motility and emptying induced by long-term insertion of a balloon used for weight reduction.

METHODS

Ten Göttingen mini-pigs were allocated into two groups with and without an intragastric balloon for 5 months. Balloons were inserted under endoscopy during general anesthesia and were filled with 350 mL of air. Gastric emptying was evaluated by scintigraphy. Gastric volume was measured by single photon emission computed tomography and proximal gastric compliance obtained using an electronic barostat. Changes in vagal tone were assessed by heart rate variability (HRV).

KEY RESULTS

After balloon insertion, gastric volume was significantly increased (2047 +/- 114.8 cm(3) after vs 1674 +/- 142.5 cm(3) before insertion, P < 0.05). Gastric compliance was also larger in balloon group (219 +/- 23.4 mL mmHg(-1) in balloon vs 168 +/- 7.7 mL mmHg(-1) in control group). Gastric emptying was reduced after insertion of the balloon (T(1/2) = 204 +/- 28.8 min vs 159 +/- 25.4 before vs after insertion). High frequency components of the spectral analysis of HRV, representing vagal tone, were increased in balloon group.

CONCLUSIONS & INFERENCES

The proximal stomach was enlarged after the insertion of a balloon in the stomach as a consequence of an increased gastric compliance. This change in compliance was probably causative for a reduction in gastric emptying rate of solids. These alterations were associated with increased vagal tone.

The effect of a meal and water loading on heart rate variability in children with functional dyspepsia

BACKGROUND

Alteration in autonomic function has been implicated as a possible pathophysiologic mechanism in functional dyspepsia (FD) in adults.

METHODS

This was a two-part study. For the first part of the study, nine children with FD and 28 controls underwent heart rate variability (HRV) analysis for 30 min baseline and for 60 min following a test meal. For the second part of the study, eight children with FD and 26 controls underwent HRV analysis for 30 min baseline and for 60 min following rapid water loading. HRV analysis yielded measures for power in the high frequency (HF) band (vagal activity), power in the low frequency (LF) band (mainly sympathetic activity), and LF/HF (sympathovagal balance).

RESULTS

HRV parameters did not differ between FD patients and controls in either baseline period or following water loading. Following the meal, HF was higher and LF and LF/HF were lower in FD patients as compared to controls. Baseline LF/HF was positively correlated with the water load volume in controls and negatively correlated with the water load volume in FD patients.

CONCLUSION

FD in children is associated with an abnormal autonomic response best demonstrated following a meal. The relationship between baseline sympathovagal balance and water load volume in FD patients is distinctly different from the relationship in control children.

Psychological adjustment and autonomic disturbances in inflammatory bowel diseases and irritable bowel syndrome

Psychological factors and the autonomic nervous system (ANS) are implicated in the pathogenesis of inflammatory bowel diseases (IBD) and irritable bowel syndrome (IBS). This study aimed to assess, firstly the way IBS and IBD patients cope with their pathology according to their affective adjustment and secondly the possible links between these affective adjustments and ANS reactivity. Patients with Crohn's disease (CD; n=26), ulcerative colitis (UC; n=22), or IBS (n=27) were recruited and compared to 21 healthy subjects based on psychological variables (trait- and state anxiety, depressive symptomatology, negative mood, perceived stress, coping, health locus of control) and sympatho-vagal balance through heart-rate variability monitored at rest. A principal component analysis, performed on all affective variables, isolated a leading factor labelled as "affective adjustment". In each disease, patients were distributed into positive and negative affective adjustment. In all the diseases, a positive affect was associated with problem-focused coping, and a negative affect with emotion-focused coping and external health locus of control. Results show that the sympatho-vagal balance varied according to the disease. In CD presenting positive affectivity, an adapted high sympathetic activity was observed. In UC, a parasympathetic blunt was observed in the presence of negative affectivity and an equilibrated sympatho-vagal balance in the presence of positive affectivity. In contrast, in IBS, an important dysautonomia (with high sympathetic and low parasympathetic tone) was constantly observed whatever the affective adjustment. In conclusion, this study suggests that the equilibrium of the ANS is differentially adapted according to the disease. This equilibrium is conjugated with positive affective and cognitive adjustment in IBD (CD and UC) but not in IBS.

Involvement of sympathetic function in the sleep-related change of gastric myoelectrical activity in rats

The gastric myoelectrical activity (GMA) fluctuates across sleep-wake states as a result of modulation by the brain-gut axis. The role of the autonomic nervous system in this phenomenon, however, was not elucidated fully. Through simultaneous recording and subsequent continuous power spectral analysis of electroencephalogram, electromyogram, electrocardiogram and electrogastromyogram (EGMG) in 16 freely moving Wistar rats, the sleep-wake states of the animals were defined and indices of cardiac autonomic regulation and GMA were calculated. We found that both cardiac autonomic regulation and GMA fluctuated through sleep-wake cycles. Correlation analysis further revealed significant correlations between EGMG power and each of the R-R interval, high-frequency power, low-frequency power, very-low-frequency power, low-frequency power to high-frequency power ratio and normalized low-frequency power of heart rate variability with respect to their trend of change across different sleep-wake states. These results suggest that the sleep-wake-related change of GMA was related to sympathovagal balance. The sympathetic nerve may play a more important role in the central modulation of GMA than perceived previously.

Studying noninvasive indices of vagal control: the need for respiratory control and the problem of target specificity

Respiratory sinus arrhythmia (RSA) is a popular index of cardiac vagal control; however, research has rarely adequately addressed respiratory influences on RSA. In addition, simplistic views of the parasympathetic system have resulted in an overinterpretation of RSA as a general indicator of vagal control. Research using a respiration-corrected time-domain index of RSA has yielded plausible findings that substantially deviate from uncorrected RSA. Paced breathing, which is used for baseline calibration of RSA in this correction procedure, allows for a representative sampling of respiratory influences on RSA and has minimal impact on autonomic regulation. Past research has largely focused on cardiac vagal activity and ignored the extent of target specificity in the parasympathetic system. More research is needed on new noninvasive indices of vagal control at other organ sites. Studies also need to address muscarinic receptor sensitivity before noninvasive vagal indices can be interpreted as markers of central vagal outflow.

Autonomic nervous system response to a solid meal and water loading in healthy children: its relation to gastric myoelectrical activity

The aim of this study was to investigate the correlation of gastric myoelectrical and autonomic activities in healthy children. Simultaneous recordings of electrogastrography (EGG) and electrocardiogram (ECG) were performed in healthy children before and after a solid meal and water loading respectively. The autonomic activity was assessed by spectral analysis of the heart rate variability (HRV). The solid meal resulted in an increase in EGG-dominant frequency (2.92 cpm vs 3.16 cpm, P < 0.05), dominant power (46.9 dB vs 53.7 dB, P < 0.05) and percentage normal slow waves (81.9%vs 89.0%, P < 0.05), while only dominant power increased following water loading. Power in the low-frequency band of HRV (LF) was significantly increased and power in the high-frequency band of HRV (HF) significantly decreased following the solid meal. Postprandial LF was positively and HF negatively correlated with the postprandial increase in EGG-dominant power. Water loading was not associated with any significant changes in HRV parameters. These results suggest that both vagal and sympathetic pathways are involved in modulation of gastric myoelectrical activity.