TY  - JOUR
AU  - Kalauzi, Aleksandar
AU  - Matić, Zoran
AU  - Bojić, Tijana
AU  - Platiša, Mirjana M.
PY  - 2023
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10507
AB  - ObjectivesIn order to reveal their structure, Poincaré plots (PP) of electrocardiogram (ECG) RR intervals (RRI) were studied as linear edge planar directed graphs, obtained by connecting all their sequential points. We were also aimed at studying their graph complexity properties.MethodsRRI signals were subjected to a series of different window length (WL) Moving Average Low Pass (MALP) filters. For each filtered graph, four standard PP descriptors: Pearson’s coefficient, SD1, SD2, and SD2/SD1 were calculated, as well as four new graph complexity measures: mean angle between adjacent graph edges; mean number of edge crossings; directional complexity and directional entropy. This approach was applied to signals of twenty young healthy subjects, recorded in four experimental conditions – combination of two body postures (supine and standing) and two breathing regimes (spontaneous and slow 0.1 Hz).ResultsWe found that PP graphs consist of two superimposed components: one originating from Respiratory Sinus Arrhythmia (RSA) oscillations, the other from slow variations (SV) of the RRI time series. This result was further corroborated by observing the transformation of a PP cloud shape occurring in filtered graphs. When applied to subjects, the outcome was that three measures significantly differentiated the two breathing regimes in the RSA region of the WL domain, while four other measures were able to differentiate two body postures in the SV WL region.DiscussionAfter obtaining these results in healthy, we expect to successfully apply this approach to patients suffering from different pathological conditions.
T2  - Biomedical Signal Processing and Control
T1  - Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series
VL  - 80
SP  - 104352
DO  - 10.1016/j.bspc.2022.104352
ER  - 

@article{
author = "Kalauzi, Aleksandar and Matić, Zoran and Bojić, Tijana and Platiša, Mirjana M.",
year = "2023",
abstract = "ObjectivesIn order to reveal their structure, Poincaré plots (PP) of electrocardiogram (ECG) RR intervals (RRI) were studied as linear edge planar directed graphs, obtained by connecting all their sequential points. We were also aimed at studying their graph complexity properties.MethodsRRI signals were subjected to a series of different window length (WL) Moving Average Low Pass (MALP) filters. For each filtered graph, four standard PP descriptors: Pearson’s coefficient, SD1, SD2, and SD2/SD1 were calculated, as well as four new graph complexity measures: mean angle between adjacent graph edges; mean number of edge crossings; directional complexity and directional entropy. This approach was applied to signals of twenty young healthy subjects, recorded in four experimental conditions – combination of two body postures (supine and standing) and two breathing regimes (spontaneous and slow 0.1 Hz).ResultsWe found that PP graphs consist of two superimposed components: one originating from Respiratory Sinus Arrhythmia (RSA) oscillations, the other from slow variations (SV) of the RRI time series. This result was further corroborated by observing the transformation of a PP cloud shape occurring in filtered graphs. When applied to subjects, the outcome was that three measures significantly differentiated the two breathing regimes in the RSA region of the WL domain, while four other measures were able to differentiate two body postures in the SV WL region.DiscussionAfter obtaining these results in healthy, we expect to successfully apply this approach to patients suffering from different pathological conditions.",
journal = "Biomedical Signal Processing and Control",
title = "Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series",
volume = "80",
pages = "104352",
doi = "10.1016/j.bspc.2022.104352"
}

Kalauzi, A., Matić, Z., Bojić, T.,& Platiša, M. M.. (2023). Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series. in Biomedical Signal Processing and Control, 80, 104352.
https://doi.org/10.1016/j.bspc.2022.104352

Kalauzi A, Matić Z, Bojić T, Platiša MM. Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series. in Biomedical Signal Processing and Control. 2023;80:104352.
doi:10.1016/j.bspc.2022.104352 .

Kalauzi, Aleksandar, Matić, Zoran, Bojić, Tijana, Platiša, Mirjana M., "Structure of Poincaré plots revealed by their graph analysis and low pass filtering of the RRI time series" in Biomedical Signal Processing and Control, 80 (2023):104352,
https://doi.org/10.1016/j.bspc.2022.104352 . .

TY  - CONF
AU  - Matić, Zoran
AU  - Kalauzi, Aleksandar
AU  - Platiša, Mirjana M.
AU  - Bojić, Tijana
PY  - 2022
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10513
AB  - It has become common in research with detrended fluctuation analysis (DFA) to use slopes of regression lines (α1 and α2) and their ratio as measures of fractal properties of dynamical processes such as physiological rhythm fluctuations. In this study, instead of the ratio (α1/α2) in DFA of ECG RR intervals and respiratory signals, we propose the use of a new measure: the inter-fractal angle (θ) - angle that DFA regression lines form between each other. Methods. Angle θ was obtained by means of graphical-analytical calculation. Using one way-Anova test, sensitivity of θ on the influence of slow breathing and orthostasis was compared in respect to ratio α1/α2. Results. Comparisons revealed that changes of (θ) were statistically more significant than changes of αl/α2. Conclusion. Inter-fractal angle is an elegant new measure of DFA that is more sensitive to perturbations such as changes in body posture and breathing regime than α1/α2.
C3  - 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO)
T1  - Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis
SP  - 1
EP  - 2
DO  - 10.1109/ESGCO55423.2022.9931387
ER  - 

@conference{
author = "Matić, Zoran and Kalauzi, Aleksandar and Platiša, Mirjana M. and Bojić, Tijana",
year = "2022",
abstract = "It has become common in research with detrended fluctuation analysis (DFA) to use slopes of regression lines (α1 and α2) and their ratio as measures of fractal properties of dynamical processes such as physiological rhythm fluctuations. In this study, instead of the ratio (α1/α2) in DFA of ECG RR intervals and respiratory signals, we propose the use of a new measure: the inter-fractal angle (θ) - angle that DFA regression lines form between each other. Methods. Angle θ was obtained by means of graphical-analytical calculation. Using one way-Anova test, sensitivity of θ on the influence of slow breathing and orthostasis was compared in respect to ratio α1/α2. Results. Comparisons revealed that changes of (θ) were statistically more significant than changes of αl/α2. Conclusion. Inter-fractal angle is an elegant new measure of DFA that is more sensitive to perturbations such as changes in body posture and breathing regime than α1/α2.",
journal = "2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO)",
title = "Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis",
pages = "1-2",
doi = "10.1109/ESGCO55423.2022.9931387"
}

Matić, Z., Kalauzi, A., Platiša, M. M.,& Bojić, T.. (2022). Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis. in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO), 1-2.
https://doi.org/10.1109/ESGCO55423.2022.9931387

Matić Z, Kalauzi A, Platiša MM, Bojić T. Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis. in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO). 2022;:1-2.
doi:10.1109/ESGCO55423.2022.9931387 .

Matić, Zoran, Kalauzi, Aleksandar, Platiša, Mirjana M., Bojić, Tijana, "Sensitivity Estimations in Favor of Using Inter-fractal Angle in Detrended Fluctuation Analysis" in 2022 12th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO) (2022):1-2,
https://doi.org/10.1109/ESGCO55423.2022.9931387 . .

TY  - JOUR
AU  - Matić, Zoran
AU  - Kalauzi, Aleksandar
AU  - Moser, Maximilian
AU  - Platiša, Mirjana M.
AU  - Lazarević, Mihailo
AU  - Bojić, Tijana
PY  - 2022
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10599
AB  - In this research we explored the (homeo)dynamic character of cardiorespiratory coupling (CRC) under the influence of different body posture and breathing regimes. Our tool for it was the pulse respiration quotient (PRQ), representing the number of heartbeat intervals per breathing cycle. We obtained non-integer PRQ values using our advanced Matlab® algorithm and applied it on the signals of 20 healthy subjects in four conditions: supine position with spontaneous breathing (Supin), standing with spontaneous breathing (Stand), supine position with slow (0.1 Hz) breathing (Supin01) and standing with slow (0.1 Hz) breathing (Stand01).Main results: Linear features of CRC (in PRQ signals) were dynamically very sensitive to posture and breathing rhythm perturbations. There are obvious increases in PRQ mean level and variability under the separated and joined influence of orthostasis and slow (0.1 Hz) breathing. This increase was most pronounced in Stand01 as the state of joint influences. Importantly, PRQ dynamic modification showed greater sensitivity to body posture and breathing regime changes than mean value and standard deviation of heart rhythm and breathing rhythm. In addition, as a consequence of prolonged supine position, we noticed the tendency to integer quantization of PRQ (especially after 14 min), in which the most common quantization number was 4:1 (demonstrated in other research reports as well). In orthostasis and slow breathing, quantization can also be observed, but shifted to other values. We postulate that these results manifest resonance effects induced by coupling patterns from sympathetic and parasympathetic adjustments (with the second as dominant factor).Significance: Our research confirms that cardiorespiratory coupling adaptability could be profoundly explored by precisely calculated PRQ parameter since cardiorespiratory regulation in healthy subjects is characterized by a high level of autonomic adaptability (responsiveness) to posture and breathing regime, although comparisons with pathological states has yet to be performed. We found Stand01 to be the most provoking state for the dynamic modification of PRQ (cardiorespiratory inducement). As such, Stand01 has the potential of using for PRQ tuning by conditioning the cardiorespiratory autonomic neural networks, e.g., in the cases where PRQ is disturbed by environmental (i.e., microgravity) or pathologic conditions.
T2  - Frontiers in Physiology
T1  - Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime
VL  - 13
DO  - 10.3389/fphys.2022.946613
ER  - 

@article{
author = "Matić, Zoran and Kalauzi, Aleksandar and Moser, Maximilian and Platiša, Mirjana M. and Lazarević, Mihailo and Bojić, Tijana",
year = "2022",
abstract = "In this research we explored the (homeo)dynamic character of cardiorespiratory coupling (CRC) under the influence of different body posture and breathing regimes. Our tool for it was the pulse respiration quotient (PRQ), representing the number of heartbeat intervals per breathing cycle. We obtained non-integer PRQ values using our advanced Matlab® algorithm and applied it on the signals of 20 healthy subjects in four conditions: supine position with spontaneous breathing (Supin), standing with spontaneous breathing (Stand), supine position with slow (0.1 Hz) breathing (Supin01) and standing with slow (0.1 Hz) breathing (Stand01).Main results: Linear features of CRC (in PRQ signals) were dynamically very sensitive to posture and breathing rhythm perturbations. There are obvious increases in PRQ mean level and variability under the separated and joined influence of orthostasis and slow (0.1 Hz) breathing. This increase was most pronounced in Stand01 as the state of joint influences. Importantly, PRQ dynamic modification showed greater sensitivity to body posture and breathing regime changes than mean value and standard deviation of heart rhythm and breathing rhythm. In addition, as a consequence of prolonged supine position, we noticed the tendency to integer quantization of PRQ (especially after 14 min), in which the most common quantization number was 4:1 (demonstrated in other research reports as well). In orthostasis and slow breathing, quantization can also be observed, but shifted to other values. We postulate that these results manifest resonance effects induced by coupling patterns from sympathetic and parasympathetic adjustments (with the second as dominant factor).Significance: Our research confirms that cardiorespiratory coupling adaptability could be profoundly explored by precisely calculated PRQ parameter since cardiorespiratory regulation in healthy subjects is characterized by a high level of autonomic adaptability (responsiveness) to posture and breathing regime, although comparisons with pathological states has yet to be performed. We found Stand01 to be the most provoking state for the dynamic modification of PRQ (cardiorespiratory inducement). As such, Stand01 has the potential of using for PRQ tuning by conditioning the cardiorespiratory autonomic neural networks, e.g., in the cases where PRQ is disturbed by environmental (i.e., microgravity) or pathologic conditions.",
journal = "Frontiers in Physiology",
title = "Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime",
volume = "13",
doi = "10.3389/fphys.2022.946613"
}

Matić, Z., Kalauzi, A., Moser, M., Platiša, M. M., Lazarević, M.,& Bojić, T.. (2022). Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime. in Frontiers in Physiology, 13.
https://doi.org/10.3389/fphys.2022.946613

Matić Z, Kalauzi A, Moser M, Platiša MM, Lazarević M, Bojić T. Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime. in Frontiers in Physiology. 2022;13.
doi:10.3389/fphys.2022.946613 .

Matić, Zoran, Kalauzi, Aleksandar, Moser, Maximilian, Platiša, Mirjana M., Lazarević, Mihailo, Bojić, Tijana, "Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime" in Frontiers in Physiology, 13 (2022),
https://doi.org/10.3389/fphys.2022.946613 . .

TY  - JOUR
AU  - Matić, Zoran
AU  - Bojić, Tijana
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8865
T2  - Vojnosanitetski pregled
T1  - Acupuncture, autonomic nervous system and biophysical origin of acupuncture system
VL  - 77
IS  - 1
SP  - 79
EP  - 86
DO  - 10.2298/VSP170818016M
ER  - 

@article{
author = "Matić, Zoran and Bojić, Tijana",
year = "2020",
journal = "Vojnosanitetski pregled",
title = "Acupuncture, autonomic nervous system and biophysical origin of acupuncture system",
volume = "77",
number = "1",
pages = "79-86",
doi = "10.2298/VSP170818016M"
}

Matić, Z.,& Bojić, T.. (2020). Acupuncture, autonomic nervous system and biophysical origin of acupuncture system. in Vojnosanitetski pregled, 77(1), 79-86.
https://doi.org/10.2298/VSP170818016M

Matić Z, Bojić T. Acupuncture, autonomic nervous system and biophysical origin of acupuncture system. in Vojnosanitetski pregled. 2020;77(1):79-86.
doi:10.2298/VSP170818016M .

Matić, Zoran, Bojić, Tijana, "Acupuncture, autonomic nervous system and biophysical origin of acupuncture system" in Vojnosanitetski pregled, 77, no. 1 (2020):79-86,
https://doi.org/10.2298/VSP170818016M . .

TY  - JOUR
AU  - Matić, Zoran
AU  - Platiša, Mirjana M.
AU  - Kalauzi, Aleksandar
AU  - Bojić, Tijana
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8848
AB  - Objective: We explored the physiological background of the non-linear operating mode of cardiorespiratory oscillators as the fundamental question of cardiorespiratory homeodynamics and as a prerequisite for the understanding of neurocardiovascular diseases. We investigated 20 healthy human subjects for changes using electrocardiac RR interval (RRI) and respiratory signal (Resp) Detrended Fluctuation Analysis (DFA, α1RRI, α2RRI, α1Resp, α2Resp), Multiple Scaling Entropy (MSERRI1−4, MSERRI5−10, MSEResp1−4, MSEResp5−10), spectral coherence (CohRRI−Resp), cross DFA (ρ1 and ρ2) and cross MSE (XMSE1−4 and XMSE5−10) indices in four physiological conditions: supine with spontaneous breathing, standing with spontaneous breathing, supine with 0.1 Hz breathing and standing with 0.1 Hz breathing. Main results: Standing is primarily characterized by the change of RRI parameters, insensitivity to change with respiratory parameters, decrease of CohRRI−Resp and insensitivity to change of in ρ1, ρ2, XMSE1−4, and XMSE5−10. Slow breathing in supine position was characterized by the change of the linear and non-linear parameters of both signals, reflecting the dominant vagal RRI modulation and the impact of slow 0.1 Hz breathing on Resp parameters. CohRRI−Resp did not change with respect to supine position, while ρ1 increased. Slow breathing in standing reflected the qualitatively specific state of autonomic regulation with striking impact on both cardiac and respiratory parameters, with specific patterns of cardiorespiratory coupling. Significance: Our results show that cardiac and respiratory short term and long term complexity parameters have different, state dependent patterns. Sympathovagal non-linear interactions are dependent on the pattern of their activation, having different scaling properties when individually activated with respect to the state of their joint activation. All investigated states induced a change of α1 vs. α2 relationship, which can be accurately expressed by the proposed measure—inter-fractal angle θ. Short scale (α1 vs. MSE1−4) and long scale (α2 vs. MSE5−10) complexity measures had reciprocal interrelation in standing with 0.1 Hz breathing, with specific cardiorespiratory coupling pattern (ρ1 vs. XMSE1−4). These results support the hypothesis of hierarchical organization of cardiorespiratory complexity mechanisms and their recruitment in ascendant manner with respect to the increase of behavioral challenge complexity. Specific and comprehensive cardiorespiratory regulation in standing with 0.1 Hz breathing suggests this state as the potentially most beneficial maneuver for cardiorespiratory conditioning. © Copyright © 2020 Matić, Platiša, Kalauzi and Bojić.
T2  - Frontiers in Physiology
T1  - Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling
VL  - 11
SP  - 24
DO  - 10.3389/fphys.2020.00024
ER  - 

@article{
author = "Matić, Zoran and Platiša, Mirjana M. and Kalauzi, Aleksandar and Bojić, Tijana",
year = "2020",
abstract = "Objective: We explored the physiological background of the non-linear operating mode of cardiorespiratory oscillators as the fundamental question of cardiorespiratory homeodynamics and as a prerequisite for the understanding of neurocardiovascular diseases. We investigated 20 healthy human subjects for changes using electrocardiac RR interval (RRI) and respiratory signal (Resp) Detrended Fluctuation Analysis (DFA, α1RRI, α2RRI, α1Resp, α2Resp), Multiple Scaling Entropy (MSERRI1−4, MSERRI5−10, MSEResp1−4, MSEResp5−10), spectral coherence (CohRRI−Resp), cross DFA (ρ1 and ρ2) and cross MSE (XMSE1−4 and XMSE5−10) indices in four physiological conditions: supine with spontaneous breathing, standing with spontaneous breathing, supine with 0.1 Hz breathing and standing with 0.1 Hz breathing. Main results: Standing is primarily characterized by the change of RRI parameters, insensitivity to change with respiratory parameters, decrease of CohRRI−Resp and insensitivity to change of in ρ1, ρ2, XMSE1−4, and XMSE5−10. Slow breathing in supine position was characterized by the change of the linear and non-linear parameters of both signals, reflecting the dominant vagal RRI modulation and the impact of slow 0.1 Hz breathing on Resp parameters. CohRRI−Resp did not change with respect to supine position, while ρ1 increased. Slow breathing in standing reflected the qualitatively specific state of autonomic regulation with striking impact on both cardiac and respiratory parameters, with specific patterns of cardiorespiratory coupling. Significance: Our results show that cardiac and respiratory short term and long term complexity parameters have different, state dependent patterns. Sympathovagal non-linear interactions are dependent on the pattern of their activation, having different scaling properties when individually activated with respect to the state of their joint activation. All investigated states induced a change of α1 vs. α2 relationship, which can be accurately expressed by the proposed measure—inter-fractal angle θ. Short scale (α1 vs. MSE1−4) and long scale (α2 vs. MSE5−10) complexity measures had reciprocal interrelation in standing with 0.1 Hz breathing, with specific cardiorespiratory coupling pattern (ρ1 vs. XMSE1−4). These results support the hypothesis of hierarchical organization of cardiorespiratory complexity mechanisms and their recruitment in ascendant manner with respect to the increase of behavioral challenge complexity. Specific and comprehensive cardiorespiratory regulation in standing with 0.1 Hz breathing suggests this state as the potentially most beneficial maneuver for cardiorespiratory conditioning. © Copyright © 2020 Matić, Platiša, Kalauzi and Bojić.",
journal = "Frontiers in Physiology",
title = "Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling",
volume = "11",
pages = "24",
doi = "10.3389/fphys.2020.00024"
}

Matić, Z., Platiša, M. M., Kalauzi, A.,& Bojić, T.. (2020). Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling. in Frontiers in Physiology, 11, 24.
https://doi.org/10.3389/fphys.2020.00024

Matić Z, Platiša MM, Kalauzi A, Bojić T. Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling. in Frontiers in Physiology. 2020;11:24.
doi:10.3389/fphys.2020.00024 .

Matić, Zoran, Platiša, Mirjana M., Kalauzi, Aleksandar, Bojić, Tijana, "Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling" in Frontiers in Physiology, 11 (2020):24,
https://doi.org/10.3389/fphys.2020.00024 . .