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Purpose: Conduct an analysis of cardiac rhythm variability in the cows of the Jersey breed with a different vegetative status.Materials and methods. Indicators of the electrocardiogram (ECG) and cardiac rhythm variability studied on cows of the Jersey breed (n = 103). For the analysis and removal of ECG, the animal studied used the program «Conan-4.5» in the system of frontal administrations according to the method of P. M. Roshchensky. Clinical research methods were carried out according to the methods of clinical inspection of animals B. V. Ears and included — inspection, palpation, percussion and auscultation of the heart area.Results. Among the entire studied array of animals, the largest amount was sympathyone — 50,5%, normotonics — 24,3%, hypersympathicotonics — 16,5%. The smallest amount — vagotonic — 8,7%. For the vagotonic, the respiratory modulation index was 8,16±0,02%, the index of the sympathetic system is 43±0,1%, and the index of slowly wave arrhythmia is 0,8±0,1%. This group of cows parasympathetic (software) prevails over the sympathetic department of the vegetative nervous system. For normotonics, the value of the respiratory modulation index was 4,14±0,03%, the index of the sympathetic system is 96±0,2%, and im is 2,5±0,2%. This group is characterized by an equilibrium state between sympathetic department and VNS. The ids for sympathicotonists amounted to 2,78±0,03%, the index of the sympathetic system is 195±0,2%, and im is 8,2±0,1%. At sympathicotonists, which are characterized by a predominance with VNS above software. The hyper smpathetical respiratory modulation index was 1,34±0,02%, ICAS — 588±0,1%, and im is 11,4±0,3%. In hypersympathicotonists, which are characterized by the predominance of the super-viper vehicle of the vegetative nervous system over parasympathetic.Conclusion. The separation of the entire array on the subgroups based on the vegetative status of animals was based on the indicators of the voltage index of regulatory systems. To confirm the correctness of the separation of the studied array of animals on the subgroup, statistical processing was carried out and a classification matrix was built. Also, to confirm the classification separation matrix, additional statistical processing of the material of the differences between the obtained groups in the square of the distance of the Mahalonobis D2 was carried out. In the course of further registration and mathematical analysis of the variability of the heart rate of cattle (cows of the Jersey breed) with the help of a modern complex electrophysiological laboratory «Conan-4.5» features of indexes of A. Ya. Kaplan were established.

The study of indicators of Kaplan indices in dogs has not been previously conducted and their normal values are not described in the available literature. Given the subtlety of the mechanisms of autonomic regulation of the heart, there is a need to expand the diagnostic base for very common heart diseases in dogs.The aim of the research is to study the Kaplan indices in dogs to assess the possibility of including them in an integrated approach to the analysis of the functioning of the heart in dogs. 74 healthy dogs were examined. The dependence of changes in the Kaplan indices on age was studied. An asymmetric distribution of Kaplan indices in the studied group of dogs was established. Intervalograms were recorded using a computerized polygraphic amplifier "MKS KARDi2-NP" (Russia). Recording was performed on dogs in a resting state, standing or sitting. To analyze the obtained intervalograms, to obtain the values of the Kaplan indices, the integrated instrumental-methodological complex "CONAN" was used.The following Kaplan indices have been studied: Respiratory modulation index (IDM); Sympathoadrenal Tone Index (SAT); Slow-wave arrhythmia index (IMA).The normal values of Kaplan's indices were established: IDM, SAT, IMA for dogs. In this regard, the assessment of these indices should be included in the basic set of methods for diagnosing heart disease in dogs. The absence of dependence of changes in indices on age in dogs was found. The lack of research on Kaplan indices requires additional research in groups of different weight on a representative sample.

Sex-related differences in respiratory modulation of sympathetic activity have been observed in rodent models of sleep apnea [intermittent hypoxia (IH)]. In light of sex disparities in the respiratory response to acute IH in humans as well as changes in respiratory modulation of muscle sympathetic nerve activity (MSNA) in clinical sleep apnea, we examined sex-related differences in respiratory modulation of MSNA following acute IH. We hypothesized that respiratory modulation of MSNA would be altered in both male and female participants after IH; however, the respiratory patterning of MSNA following IH would be sex specific. Heart rate, MSNA, and respiration were evaluated in healthy male ( n = 21, 30 ± 5 yr) and female ( n = 10, 28 ± 5 yr) participants during normoxic rest before and after 30 min of IH. Respiratory modulation of MSNA was assessed by fitting polynomials to cross-correlation histograms constructed between sympathetic spikes and respiration. MSNA was elevated after IH in male (20 ± 6 to 24 ± 8 bursts/min) and female (19 ± 8 to 22 ± 10 bursts/min) participants ( P < 0.01). Both male and female participants exhibited respiratory modulation of MSNA ( P < 0.01); however, the pattern differed by sex. After IH, modulation of MSNA within the breath was reduced in male participants ( P = 0.03) but increased in female participants ( P = 0.02). Both male and female adults exhibit changes in respiratory patterning of MSNA after acute IH; however, this pattern differs by sex. These data support sex disparities in respiratory modulation of MSNA and may have implications for conditions such as sleep apnea.

The need to understand and control intracranial pressure (ICP) is required for treatments in various clinical situations. The ICP value can only be measured by direct intracranial catheter or sensor placement, and a non-invasive ICP prediction method has not yet been established. We focused on the natural resonance frequency (NRF) of the brain to predict the ICP value. The ICP value, pulse waveform of intracranial pressure (PWICP) and cervical carotid pressure waveform (CCPW) were simultaneously collected from patients who had undergone ventricular drainage or ICP sensor placement for medical treatment in our institute. A total of 43 data were obtained from 27 patients, age ranged 14-48 (mean: 54) years, body height 137-187 (mean 163) cm and body weight 32-103 (mean 61) kg. The total measured time was 29,653 seconds and the measured mean ICP value in each data ranged from 3.82 to 69.39 (mean 25.9) hPa. Consecutive data was cut into 10.24 seconds, which was called a "column". To decrease respiratory modulation, the largest positive peak of cardiac pulsation of CCPW was picked up in each column, as well as one ICP pulse waveform. The picked-up CCPW and PWICP were averaged by the weighted average method. The transfer characteristics from CCPW to PWICP were calculated by the transfer function method. The first initial negative peak of transfer characteristics was judged as the NRF of the brain. The relationship between the ICP value and the NRF of the brain was presented on the quadratic functions graph (ICP = 0.0329(NRF)2 + 0.0842NRF). These parameters were strongly correlated to each other (R2= 0.9952 coefficient of determination). The individual NRF, which was calculated by the transfer function method, only depends on the measured ICP value and their relationship can be presented in the simple quadratic functions. Funding: This research was funded by Japan Science and Technology Agency (JST) A-STEP feasibility study in 2012, and by Japan's New Energy and Industrial Technology Development Organization (NEDO) in 2013, and by Grants-in-Aid for scientific research in Ministry of Education, Culture, Sports, Science and Technology-Japan from 2015 to 2017 and 2018 to 2020. Receiver: Kenji Furihata. Declaration of Interest: Although the authors (T.G., K.F. and K.H.) have some patents of non-invasive intracranial pressure monitoring apparatus, the claim of the patents belong to affiliated university not to individuals. All of authors had already opened their COI disclosure in Japanese Neurosurgical Society. The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described. Our proposing theory is a quite new concept. We strongly believe that there is nothing to competing interest declaration. Ethical Approval: The simultaneous measurement of intracranial pressure and cervical carotid artery pressure waveform was approved by Ethical Committee of Shinshu University School of Medicine. “Development of non-invasive intracranial pressure monitoring” approved number 2343.

Although respiratory sinus arrhythmia and blood pressure variability have been investigated extensively, there have been far fewer studies of the respiratory modulation of peripheral blood flow in humans. Existing studies have been based primarily on noninvasive measurements using digit photoplethysmography and laser-Doppler flowmetry. The cumulative knowledge derived from these studies suggests that respiration can contribute to fluctuations in peripheral blood flow and volume through a combination of mechanical, hemodynamic, and neural mechanisms. However, the most convincing evidence suggests that the sympathetic nervous system plays the predominant role under normal, resting conditions. This mini-review provides a consolidation and interpretation of the key findings reported in this topical area. Given the need to extract dynamic information from noninvasive measurements under largely “closed-loop” conditions, we propose that the application of analytical tools based on systems theory and mathematical modeling can be of great utility in future studies. In particular, we present an example of how the transfer relation linking respiration to peripheral vascular conductance can be derived using measurements recorded during spontaneous breathing, spontaneous sighs, and ventilator-induced sighs.

The article is devoted to the issues of conceptual development of a new generation of electrocardiogram imitators. A mathematical model is proposed for simulating ECG signal considering the variability of biosignal morphology, the presence of various distortions and artefacts, heart rate variability and respiratory modulation of ECG signal. A block diagram of the ECG simulator was designed.

While respiratory adaptation to exercise is compulsory to cope with the increased metabolic supply to body tissues and with the necessary clearing of metabolic waste, the neural apparatus at stake remains poorly identified. Using viral tracing, ex vivo and in vivo optogenetic and chemogenetic interference strategies in mice, we unravel interactive locomotor and respiratory networks’ nodes that mediate the respiratory rate increase that accompanies a running exercise. We show that the mesencephalic locomotor region (MLR) and the lumbar spinal locomotor pattern generator (lumbar CPG), which respectively initiate and execute the locomotor behavior, access the respiratory network through distinct entry points. The MLR directly projects onto the inspiratory rhythm generator, the preBötzinger complex (preBötC), and can trigger a moderate increase of respiratory frequency, prior to, or even in the absence of, locomotion. In contrast, the lumbar CPG projects onto the retrotrapezoid nucleus (RTN) that in turn contacts the preBötC to enforce, during effective locomotion, higher respiratory frequencies. These data expand, on the one hand, the functional implications of the MLR beyond locomotor initiation to a bona fide respiratory modulation. On the other hand, they expand the adaptive respiratory ambitions of the RTN beyond chemoception to “locomotor- ception”.

Objective: Breathing rate (BR) can be estimated by extracting respiratory signals from the electrocardiogram (ECG) or photoplethysmogram (PPG). The extracted respiratory signals may be influenced by several technical and physiological factors. In this study, our aim was to determine how technical and physiological factors influence the quality of respiratory signals. Approach: Using a variety of techniques 15 respiratory signals were extracted from the ECG, and 11 from PPG signals collected from 57 healthy subjects. The quality of each respiratory signal was assessed by calculating its correlation with a reference oral-nasal pressure respiratory signal using Pearson's correlation coefficient. Main results: Relevant results informing device design and clinical application were obtained. The results informing device design were: (i) seven out of 11 respiratory signals were of higher quality when extracted from finger PPG compared to ear PPG; (ii) laboratory equipment did not provide higher quality of respiratory signals than a clinical monitor; (iii) the ECG provided higher quality respiratory signals than the PPG; (iv) during downsampling of the ECG and PPG significant reductions in quality were first observed at sampling frequencies of

Accurately diagnosing sleep disorders is essential for clinical assessments and treatments. Polysomnography (PSG) has long been used for detection of various sleep disorders. In this research, electrocardiography (ECG) and electromayography (EMG) have been used for recognition of breathing and movement-related sleep disorders. Bio-signal processing has been performed by extracting EMG features exploiting entropy and statistical moments, in addition to developing an iterative pulse peak detection algorithm using synchrosqueezed wavelet transform (SSWT) for reliable extraction of heart rate and breathing-related features from ECG. A deep learning framework has been designed to incorporate EMG and ECG features. The framework has been used to classify four groups: healthy subjects, patients with obstructive sleep apnea (OSA), patients with restless leg syndrome (RLS) and patients with both OSA and RLS. The proposed deep learning framework produced a mean accuracy of 72% and weighted F1 score of 0.57 across subjects for our formulated four-class problem., Paper is offered by the publisher as Open Acess: https://www.mdpi.com/1424-8220/20/9/2594

The frequency of fibrillatory waves (f-waves), F f , exhibits significant variation over time, and previous studies suggest that some of this variation is related to respiratory modulation through the autonomic nervous system. In this study, we tested the hypothesis that this variation (ΔF f ) could be related to acetylcholine concentration ([ACh]) release pattern. Electrocardiograms were recorded from seven patients during controlled respiration before and after full vagal blockade, from which f-wave frequency modulation was characterized. Computational simulations in human atrial tissues were performed to assess the effects of [ACh] release pattern on F f and compared to experimental results in humans. A cross-stimulation protocol was applied onto the tissue to initiate a rotor while cyclically varying [ACh] following a sinusoidal waveform of frequency equal to 0.125 Hz. Different mean levels (0.05, 0.075μM/l) and peak-to-peak ranges (0.1, 0.05, 0.025 μM/l) of [ACh] variation were tested. In all patients, an f-wave frequency modulation could be observed. In 57% of the patients, this modulation was significantly reduced after vagal blockade. Simulations confirmed that rotor frequency variations followed the induced [ACh] patterns. Mean F f was dependent on mean [ACh] level, whileΔF f was dependent on [ACh] variation range.

The partial pressures of carbon dioxide and oxygen in the blood are the dominant homeostatic controller of respiration. Over the course of evolution, in addition to its primary purpose of exchange of gases, the control of ventilatory apparatus has become a part of a large number of non-respiratory motor behaviours such as swallowing, vocalization and abdominal straining during parturition. The emotional states and sleep–wakefulness states are associated with altered respiratory pattern. A number of reflexes protect the respiratory tract from environmental irritants, from aspiration of mucous and from food during ingestion. The thorough information regarding the patterns of respiratory modulation during a wide variety of the physiological activities shall be presented this chapter along with the most recent information on the neural basis for such modulations.

Automatically determining when a person falls asleep from easily available vital signals is important, not just for medical applications but also for practical ones, such as traffic safety or smart homes. Oscillatory mechanisms of heart dynamics and respiration cycle couple differently during sleep and awake. Specifically, respiratory modulation of heart rhythm or Respiratory Sinus Arrhythmia (RSA) is more prominent during sleep, as both sleep and RSA are connected to strong vagal activity. The onset of sleep can be recognized or even predicted as the increase of cardio-respiratory coupling. Here, we employ this empirical fact to design a method for detecting the change of consciousness status (sleep/awake) based only on heart rate variability (HRV) data. Our method relies on quantifying the (self)similarity among shapelets – short chunks of HRV time series - whose ‘shapes’ are related to the respiration cycle. To test our method, we examine the HRV data of 75 healthy individuals recorded with microsecond precision. We find distinctive patterns stable across age and sex, that are not only indicative of sleep and awake, but allow pinpoint the change from awake to sleep almost immediately. More systematic analysis along these lines could lead to a reliable prediction of sleep.

Respiratory interoception may play an important role in the perception of respiratory symptoms in pulmonary diseases. As the respiratory cycle affects startle eye blink responses, startle modulation may be used to assess visceral-afferent signals from the respiratory system. To ascertain the potential impact of brainstem-relayed signals on cortical processes, we investigated whether this pre-attentive respiratory modulation of startle (RMS) effect is also reflected in the modulation of higher cognitive, evaluative processing of the startle stimulus. Twenty-nine healthy volunteers received 80 acoustic startle stimuli (100 or 105 dB(A); 50 ms), which were presented at end and mid inspiration and expiration, while performing a paced breathing task (0.25 Hz). Participants first responded to the startle probes by 'as fast as possible' button pushes and then rated the perceived intensity of the stimuli. Psychomotor response time was divided into 'reaction time' (RT; from stimulus onset to home button release; represents stimulus evaluation) and 'movement time' time (MT; from home button release to target button press). Intensity judgments were higher and RTs accelerated during mid expiration. No effect of respiratory cycle phase was found on eye blink responses and MTs. We conclude that respiratory cycle phase affects higher cognitive, attentional processing of startle stimuli. ispartof: Neuroscience Letters vol:711 ispartof: location:Ireland status: Published online

Objective: Although the important role of respiratory modulation of the cardiovascular system in the development of hypertension has been demonstrated in animal studies, little research has assessed this modulation in essential hypertensive patients. We aimed to explore whether respiratory-related variations in cardiovascular variables are changed in hypertensive patients and their potential relationships with the respiratory pattern. Methods: Respiration, ECG, and beat-to-beat blood pressure (BP) were simultaneously measured in 46 participants (24 hypertensive patients and 22 normotensive participants) during rest and a mental arithmetic task (MAT). Respiratory-triggered averaging and orthogonal subspace projection methods were used to assess the respiratory modulations of BP and heart rate (HR). Respiratory parameters including inspiratory time, expiratory time, respiratory rate and their variabilities were also characterized. Results: The inspiratory time, expiratory time, respiratory rate and their variabilities were not different between hypertensive and normotensives. Additionally, the modulation of HR by respiration was also similar between the two groups. Hypertensive patients exhibited an amplified respiratory modulation of systolic BP (SBP), as assessed from the amplitude of respiratory-related changes and the percentage of the power of respiratory-related variation, and also reflected from the temporal pattern of respiratory modulation of SBP. The exaggerated respiratory-related variation of SBP in hypertensive patients accounted for ≈23% of the total power of SBP, producing an absolute change of ≈4.5 mmHg in SBP. MAT was characterized by decreased inspiratory time and increased variabilities of expiratory time and respiratory rate with no changes in the amplitude of respiratory modulations. Conclusion: Hypertensive patients had excessive respiratory modulation of SBP, despite having similar respiratory pattern with normotensives. These findings highlight the importance of respiratory influence in BP variation and suggest that respiratory modulation of SBP may have prognostic information for cardiovascular events in hypertensive patients.

Continuous and non-invasive respiratory rate (RR) monitoring would significantly improve patient outcomes. Currently, RR is under-recorded in clinical environments and is often measured by manually counting breaths. In this work, we investigate the use of respiratory signal quality quantification and several neural network (NN) structures for improved RR estimation. We extract respiratory modulation signals from the electrocardiogram (ECG) and photoplethysmogram (PPG) signals, and calculate a possible RR from each extracted signal. We develop a straightforward and efficient respiratory quality index (RQI) scheme that determines the quality of each moonddulation-extracted respiration signal. We then develop NNs for the estimation of RR, using estimated RRs and their corresponding quality index as input features. We determine that calculating RQIs for modulation-extracted RRs decreased the mean absolute error (MAE) of our NNs by up to 38.17%. When trained and tested using 60-sec waveform segments, the proposed scheme achieved an MAE of 0.638 breaths per minute. Based on these results, our scheme could be readily implemented into non-invasive wearable devices for continuous RR measurement in many healthcare applications.

NEW FINDINGS What is the central question of the study? There are sex differences in the respiratory network and in the regulation of arterial blood pressure. Female rats develop hypertension after chronic intermittent hypoxia (CIH). In this context, we evaluated the respiratory-related mechanism underlying the development of hypertension in CIH-exposed female rats. What is the main finding and its importance? Female rats exposed to CIH develop changes in the respiratory pattern related to inspiration and sympathetic overactivity phase locked to the inspiratory phase of the respiratory cycle, which is different from CIH-exposed male rats. These data suggest a specific respiratory mechanism for sympathetic overactivity in hypertensive CIH-exposed female rats. Chronic intermittent hypoxia (CIH) induces sympathetic overactivity and hypertension in male rats. Enhanced respiratory modulation of sympathetic activity in juvenile male rats exposed to CIH occurs in the expiratory phase of the respiratory cycle, characterizing changes in respiratory-sympathetic coupling. Different from other experimental models of hypertension, CIH induces an increase in arterial pressure in adult female rats similar to that observed in male rats. However, the mechanisms underlying the hypertensive phenotype in CIH-exposed female rats remain to be elucidated. Moreover, several lines of evidence have documented sex differences in respiratory network activity in response to hypoxia. Considering that CIH-exposed male rats present an increase in the respiratory modulation of sympathetic activity and there are sex differences in the respiratory network, we hypothesized that CIH-exposed female rats develop an increase in the respiratory modulation of sympathetic activity different from CIH-exposed male rats. In this study, we investigated sympathetic and respiratory activities in juvenile female rats exposed to CIH using an in situ working heart-brainstem preparation. The CIH-exposed female rats developed changes in the respiratory pattern and changes in the respiratory-sympathetic coupling marked by sympathetic overactivity phase locked to inspiration, which was different from male rats exposed to CIH. This study revealed a specific respiratory-related mechanism for sympathetic overactivity linked to inspiration that explains, at least in part, the hypertensive phenotype in female rats exposed to CIH.

In mammals respiratory-locked hippocampal rhythms are implicated in the scaffolding and transfer of information between sensory and memory networks. These oscillations are entrained by nasal respiration and driven by the olfactory bulb. They then travel to the piriform cortex where they propagate further downstream to the hippocampus and modulate neural processes critical for memory formation. In humans, bypassing nasal airflow through mouth-breathing abolishes these rhythms and impacts encoding as well as recognition processes thereby reducing memory performance. It has been hypothesized that similar behavior should be observed for the consolidation process, the stage between encoding and recognition, were memory is reactivated and strengthened. However, direct evidence for such an effect is lacking in human and nonhuman animals. Here we tested this hypothesis by examining the effect of respiration on consolidation of episodic odor memory. In two separate sessions, female and male participants encoded odors followed by a 1 h awake resting consolidation phase where they either breathed solely through their nose or mouth. Immediately after the consolidation phase, memory for odors was tested. Recognition memory significantly increased during nasal respiration compared with mouth respiration during consolidation. These results provide the first evidence that respiration directly impacts consolidation of episodic events, and lends further support to the notion that core cognitive functions are modulated by the respiratory cycle. SIGNIFICANCE STATEMENT Memories pass through three main stages in their development: encoding, consolidation, and retrieval. Growing evidence from animal and human studies suggests that respiration plays an important role in the behavioral and neural mechanisms associated with encoding and recognition. Specifically nasal, but not mouth, respiration entrains neural oscillations that enhance encoding and recognition processes. We demonstrate that respiration also affects the consolidation stage. Breathing through the nose compared with the mouth during consolidation enhances recognition memory. This demonstrates, first, that nasal respiration is important during the critical period were memories are reactivated and strengthened. Second, it suggests that the neural mechanisms responsible may emerge from nasal respiration.

Why sympathetic activity rises in neurogenic hypertension remains unknown. It has been postulated that changes in the electrical excitability of medullary pre-sympathetic neurones are the main causal mechanism for the development of sympathetic overactivity in experimental hypertension. Here we review recent data suggesting that enhanced sympathetic activity in neurogenic hypertension is, at least in part, dependent on alterations in the electrical excitability of medullary respiratory neurones and their central modulation of sympatho-excitatory networks. We also present results showing a critical role for carotid body tonicity in the aetiology of enhanced central respiratory modulation of sympathetic activity in neurogenic hypertension. We propose a novel hypothesis of respiratory neurone channelopathy induced by carotid body overactivity in neurogenic hypertension that may contribute to sympathetic excess. Moreover, our data support the notion of targeting the carotid body as a potential novel therapeutic approach for reducing sympathetic vasomotor tone in neurogenic hypertension.

An introduction to the Respiratory Rate Estimation (RRest) project, with a focus on the assessment of RR algorithms reported in this publication: Charlton P.H. et al. Extraction of respiratory signals from the electrocardiogram and photoplethysmogram: technical and physiological determinants, Physiological Measurement, 2017. DOI: http://doi.org/10.1088/1361-6579/aa670e This presentation is designed for use in Journal Club settings. Originally presented at the University of Oxford on 11th May 2016., This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC, Grant EP/H019944/1); the Oxford and King's College London Centres of Excellence in Medical Engineering funded by the Wellcome Trust and EPSRC under Grants WT88877/Z/09/Z and WT088641/Z/09/Z; the National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's & St Thomas' NHS Foundation Trust and King's College London; the NIHR Oxford Biomedical Research Centre Programme; a Royal Academy of Engineering Research Fellowship (RAEng) awarded to David A Clifton; and an EPSRC Challenge Award to David A Clifton. The views expressed are those of the authors and not necessarily those of the EPSRC, Wellcome Trust, NIHR, NHS, Department of Health or RAEng., {"references":["Charlton P.H. et al. Extraction of respiratory signals from the electrocardiogram and photoplethysmogram: technical and physiological determinants, Physiological Measurement, 2017. DOI: 10.1088/1361-6579/aa670e"]}

DPOP quantifies respiratory modulations in the photoplethysmogram. It has been proposed as a noninvasive surrogate for pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients. The correlation between DPOP and PPV may degrade due to low perfusion effects. We implemented an automated DPOP algorithm with an optional correction for low perfusion. These two algorithm variants (DPOPa and DPOPb) were tested on data from 20 mechanically ventilated OR patients split into a benign “stable region” subset and a whole record “global set.” Strong correlation was found between DPOP and PPV for both algorithms when applied to the stable data set:R=0.83/0.85for DPOPa/DPOPb. However, a marked improvement was found when applying the low perfusion correction to the global data set:R=0.47/0.73for DPOPa/DPOPb. Sensitivities, Specificities, and AUCs were 0.86, 0.70, and 0.88 for DPOPa/stable region; 0.89, 0.82, and 0.92 for DPOPb/stable region; 0.81, 0.61, and 0.73 for DPOPa/global region; 0.83, 0.76, and 0.86 for DPOPb/global region. An improvement was found in all results across both data sets when using the DPOPb algorithm. Further, DPOPb showed marked improvements, both in terms of its values, and correlation with PPV, for signals exhibiting low percent modulations.