Respiratory Period Research Articles

On-board synthetic 4D MRI generation from 4D CBCT for radiotherapy of abdominal tumors: A feasibility study.

Magnetic resonance-guided radiotherapy with an MR-guided LINAC represents potential clinical benefits in abdominal treatments due to the superior soft-tissue contrast compared to kV-based images in conventional treatment units. However, due to the high cost associated with this technology, only a few centers have access to it. As an alternative, synthetic 4D MRI generation based on artificial intelligence methods could be implemented. Nevertheless, appropriate MRI texture generation from CT images might be challenging and prone to hallucinations, compromising motion accuracy. To evaluate the feasibility of on-board synthetic motion-resolved 4D MRI generation from prior 4D MRI, on-board 4D cone beam CT (CBCT) images, motion modeling information, and deep learning models using the digital anthropomorphic phantom XCAT. The synthetic 4D MRI corresponds to phases from on-board 4D CBCT. Each synthetic MRI volume in the 4D MRI was generated by warping a reference 3D MRI (MRIref, end of expiration phase from a prior 4D MRI) with a deformation field map (DFM) determined by (I) the eigenvectors from the principal component analysis (PCA) motion-modeling of the prior 4D MRI, and (II) the corresponding eigenvalues predicted by a convolutional neural network (CNN) model using the on-board 4D CBCT images as input. The CNN was trained with 1000 deformations of one reference CT (CTref, same conditions as MRIref) generated by applying 1000 DFMs computed by randomly sampling the original eigenvalues from the prior 4D MRI PCA model. The evaluation metrics for the CNN model were root-mean-square error (RMSE) and mean absolute error (MAE). Finally, different on-board 4D-MRI generation scenarios were assessed by changing the respiratory period, the amplitude of the diaphragm, and the chest wall motion of the 4D CBCT using normalized root-mean-square error (nRMSE) and structural similarity index measure (SSIM) for image-based evaluation, and volume dice coefficient (VDC), volume percent difference (VPD), and center-of-mass shift (COMS) for contour-based evaluation of liver and target volumes. The RMSE and MAE values of the CNN model reported 0.012±0.001 and 0.010±0.001, respectively for the first eigenvalue predictions. SSIM and nRMSE were 0.96±0.06 and 0.22±0.08, respectively. VDC, VPD, and COMS were 0.92±0.06, 3.08±3.73 %, and 2.3±2.1mm, respectively, for the target volume. The more challenging synthetic 4D-MRI generation scenario was for one 4D-CBCT with increased chest wall motion amplitude, reporting SSIM and nRMSE of 0.82 and 0.51, respectively. On-board synthetic 4D-MRI generation based on predicting actual treatment deformation from on-board 4D-CBCT represents a method that can potentially improve the treatment-setup localization in abdominal radiotherapy treatments with a conventional kV-based LINAC.

On the validity of the state space correspondence strategy based on k-nearest neighbor cross-predictability in assessing directionality in stochastic systems: Application to cardiorespiratory coupling estimation.

We tested the validity of the state space correspondence (SSC) strategy based on k-nearest neighbor cross-predictability (KNNCP) to assess the directionality of coupling in stochastic nonlinear bivariate autoregressive (NBAR) processes. The approach was applied to assess closed-loop cardiorespiratory interactions between heart period (HP) variability and respiration (R) during a controlled respiration (CR) protocol in 19 healthy humans (aged from 27 to 35 yrs, 11 females) and during active standing (STAND) in 25 athletes (aged from 20 to 40 yrs, all men) and 25 non-athletes (aged from 20 to 40 yrs, all men). Over simulated NBAR processes, we found that (i) the SSC approach can detect the correct causal relationship as the direction leads to better KNNCP from the past of the driver to the future state of the target and (ii) simulations suggest that the ability of the method is preserved in any condition of complexity of the interacting series. Over CR and STAND protocols, we found that (a) slowing the breathing rate increases the strength of the causal relationship in both temporal directions in a balanced modality; (b) STAND is more powerful in modulating the coupling strength on the pathway from HP to R; (c) regardless of protocol and experimental condition, the strength of the link from HP to R is stronger than that from R to HP; (d) significant causal relationships in both temporal directions are found regardless of the level of complexity of HP variability and R. The SSC strategy is useful to disentangle closed-loop cardiorespiratory interactions.

Oral enteral nutrition in the emergency department for children with bronchiolitis hospitalized on high flow nasal cannula

ObjectivesWe assessed whether initiation of oral enteral nutrition in the emergency department (ED) for patients with bronchiolitis hospitalized on humidified high flow nasal cannula (HHFNC) was associated with a shorter hospital length of stay (LOS) without an increase in return ED visits or hospital readmissions. Patients and methodsThis retrospective cohort study included children ≤24 months of age with bronchiolitis hospitalized to the general pediatric floor on HHFNC in two time periods: October 1, 2018 – April 30, 2019, and following implementation of a revised institutional bronchiolitis pathway that encouraged enteral nutrition initiation in the ED, October 1, 2021 – April 30, 2022. The primary outcome of interest was hospital LOS where the exposure was enteral feeding in the ED. ResultsWe included 391 ‘fed’, 114 ‘not fed’ and 304 ‘unknown’ patients. HHFNC treatment time (25 h for ‘fed’ vs. 43 h for ‘not fed’ vs. 35 h for‘unknown’, p = 0.0001) and hospital LOS (39 h for ‘fed’ vs. 56 h for ‘not fed’ vs. 48 h for ‘unknown’, p = 0.0001) was shorter in the ‘fed’ group. There were no significant differences in return ED visits or hospital readmissions. Using our median LOS (45.1 h, inter-quartile range 30.2, 64.4 h) while controlling for age, sex, initial HHFNC flow rate, the respiratory oxygenation (ROX) index, viral etiology, and time period, an adjusted logistic regression analysis demonstrated that patients fed in the ED were 1.8 times more likely to have a hospital LOS of <45 h (aOR 1.88, 95% CI 1.11–3.18, p = 0.019). ConclusionsInitiation of oral enteral nutrition in the ED for patients with bronchiolitis on HHFNC is associated with a shorter hospital LOS without an increase in return ED visits or hospital readmissions. Future prospective studies are needed to develop feeding recommendations for children with bronchiolitis receiving HHFNC support.

Tilt-evoked, breathing-driven blood pressure oscillations: Independence from baroreflex-sympathoneural function

PurposeOrthostasis increases the variability of continuously recorded blood pressure (BP). Low-frequency (LF) BP oscillations (Mayer waves) in this setting are related to the vascular-sympathetic baroreflex. Mechanisms of increased high-frequency (HF) BP oscillations at the periodicity of respiration during orthostasis have received less research attention. A previously reported patient with post-neurosurgical orthostatic hypotension (OH) and vascular-sympathetic baroreflex failure had large tilt-evoked, breathing-driven BP oscillations, suggesting that such oscillations can occur independently of vascular-sympathetic baroreflex modulation. In the present study we assessed effects of orthostasis on BP variability in the frequency domain in patient cohorts with or without OH.MethodsPower spectral analysis of systolic BP variability was conducted on recordings from 73 research participants, 42 with neurogenic OH [13 pure autonomic failure, 14 Parkinson’s disease (PD) with OH, 12 parkinsonian multiple system atrophy, and 3 status post-brainstem neurosurgery] and 31 without OH (control group of 16 healthy volunteers and 15 patients with PD lacking OH), before, during, and after 5′ of head-up tilt at 90 degrees from horizontal. The data were log transformed for statistical testing.ResultsAcross all subjects, head-up tilting increased HF power of systolic BP variability (p = 0.001), without a difference between the neurogenic OH and control groups. LF power during orthostasis was higher in the control than in the OH groups (p = 0.009).ConclusionsThe results of this observational cohort study confirm those based on our case report and lead us to propose that even in the setting of vascular-sympathetic baroreflex failure orthostasis increases HF power of BP variability.

Ecotoxicological assessment of natural soil amended with sewage sludge: the impacts on soil edaphic organisms and microbial community.

Sewage sludge usage as agricultural soil amendment is a well-known practice employed worldwide. However, certain components may pose risks to the soil ecosystem. For a better verification of the potential adverse effects on the soil biota, biological assays have become an indispensable tool for an accurate understanding of the residue's behavior on soil, as well as its potential toxicity. Accordingly, to properly assess the effects of natural tropical soil (Oxisoil) amended with sewage sludge, we conducted toxicological tests with edaphic organisms (Enchytraeus crypticus and Folsomia candida) and microbial biomass (through respirometric assessment). Results indicate that E. crypticus and F. candida present similar reproduction sensitivity behavior to sewage sludge. For the microbiological analysis, the results suggest that microbial activity was stimulated by sludge application. For further evaluation of respiration of the microbial community and CO2 stabilization values behavior, Ford-Walford modeling was applied and presented limit values for sludge application in soil for 1.5gkg-1 and 15.0gkg-1 of, approximately, 55mg and 88mg, respectively. CO2 releases were faster and reached stability within 18weeks for the soil with higher sludge content (15.0gkg-1 of dry soil). In contrast, CO2 releases were slower for the soil with lower sludge content (1.5gkg-1 of dry soil), and until the experiment's final period (21weeks) respiration behavior did not reach stability. This study indicates that the stabilized sewage sludge, at the considered recommended application rate, presents a low toxicity risk for the studied bioindicators, being suitable for agricultural use.

Effects of Respiratory Muscle Exercise on Blood Pressure Response by Sympathetic Nervous System Activation

PURPOSE: This study investigated the cardiovascular improvement effect of respiratory muscle exercise and evaluate the possibility of improving and preventing cardiovascular disease (CVD) from a long-term perspective.METHODS: The study was designed as a crossover design with the same subjects (n=9). Subjects underwent a 2-week non-intervention period (CON) and a 2-week respiratory muscle exercise period (RespEX). Body composition, blood pressure, heart rate (HR), and inspiratory capacity were measured for all subjects before and after the intervention. In addition, cold pressure test (CPT) and exercise stress test were performed.RESULTS: Respiratory muscle exercise was found to significantly reduce resting HR (in RespEX, Pre- vs. Post-, &lt;i&gt;p&lt;/i&gt;&lt;.01). This was accompanied by the strengthening of the respiratory muscles. Also, exercise time was increased (in RespEX, Pre- vs. Post-, &lt;i&gt;p&lt;/i&gt;&lt;.001). However, it did not induce an increase in maximal oxygen consumption. The results of the CPT confirmed that hypersensitivity-induced HR increases were prevented.CONCLUSIONS: Respiratory muscle exercise may have some benefits in preventing CVD, but it seems reasonable to use it as an adjunctive therapy to aerobic exercise. Although limited, it was confirmed that respiratory muscle exercise can have a beneficial effect on cardiovascular improvement and CVD prevention through CPT.

Changes in water relations, leaf gas exchange and elemental composition of peach leaves infected with Taphrina deformans (Berk.) Tul

An investigation of water relations, leaf gas-exchange and elemental composition of healthy (control) and naturally infected with Taphrina deformans peach leaves was carried out. It was established that the water content and water potential were significantly higher in the infected leaves, while the relative water content and transpiration rate were not changed. The dark period respiration rate of infected leaves increased dramatically but the gross photosynthesis rate was strongly inhibited. The phosphorus and potassium content of infected leaves was higher than in the healthy leaves, but the content of other analysed elements diminished at different extent. The current work presents the results of the study related to the changes in water status, CO2 exchange rate and elemental composition of T. deformans-infected peach leaves.

Two-level eddy covariance measurements reduce bias in land-atmosphere exchange estimates over a heterogeneous boreal forest landscape

Estimates of land-atmosphere exchanges of carbon, energy, water vapor, and other greenhouse gases based on the eddy covariance (EC) technique rely on the fundamental assumption that the flux footprint area is homogeneous. We investigated the impact of source area heterogeneity on flux estimates in single-level EC measurements over a managed boreal forest landscape. For this purpose, we compared single-level measurements with those from a two-level approach consisting of concurrent EC measurements at 60 and 85 m above the ground. This two-level set-up provided a unique opportunity to obtain nearly congruent diel footprint areas by combining data from the higher and lower levels during day- and nighttime, respectively.We found that the variation in the averaged footprint area between day- and nighttime was reduced by up to 89% in the two-level approach compared to the single-level data at the higher level (85 m). Considering spring, summer, and fall months, the resulting relative potential bias in flux observations due to landscape heterogeneity was highest at short time steps (≤ daily) ranging between 35% and 325% for half-hourly data. During winter months, when stable atmospheric regimes prevailed during day and night, the footprints within the diel course nearly overlapped also at a given single level and hence no improvement of flux estimates was found. The absolute cumulated sums for the study period (excluding winter months) of gross primary production, ecosystem respiration, latent heat, and sensible heat flux were underestimated by about 28%, 52%, 5%, and 3%, respectively, whereas that of net ecosystem CO2 exchange was overestimated by about 109% in the single-level approach. Overall this study suggests that footprint heterogeneity may introduce considerable bias in single-level flux estimates — particularly at short time scales — with large implications for model-data fusion studies, site comparisons, and up- or downscaling of land-atmosphere exchange processes.

Surface guided electron FLASH radiotherapy for canine cancer patients.

During recent years FLASH radiotherapy (FLASH-RT) has shown promising results in radiation oncology, with the potential to spare normal tissue while maintaining the antitumor effects. The high speed of the FLASH-RT delivery increases the need for fast and precise motion monitoring to avoid underdosing the target. Surface guided radiotherapy (SGRT) uses surface imaging (SI) to render a 3D surface of the patient. SI provides real-time motion monitoring and has a large scanning field of view, covering off-isocentric positions. However, SI has so far only been used for human patients with conventional setup and treatment. The aim of this study was to investigate the performance of SI as a motion management tool during electron FLASH-RT of canine cancer patients. To evaluate the SI system's ability to render surfaces of fur, three fur-like blankets in white, grey, and black were used to imitate the surface of canine patients and the camera settings were optimized for each blanket. Phantom measurements using the fur blankets were carried out, simulating respiratory motion and sudden shift. Respiratory motion was simulated using the QUASAR Respiratory Motion Phantom with the fur blankets placed on the phantom platform, which moved 10mm vertically with a simulated respiratory period of 4 s. Sudden motion was simulated with an in-house developed phantom, consisting of a platform which was moved vertically in a stepwise motion at a chosen frequency. For sudden measurements, 1, 2, 3, 4, 5, 6, 7, and 10Hz were measured. All measurements were both carried out at the conventional source-to-surface distance (SSD) of 100cm, and in the locally used FLASH-RT setup at SSD=70cm. The capability of the SI system to reproduce the simulated motion and the sampling time were evaluated. As an initial step towards clinical implementation, the feasibility of SI for surface guided FLASH-RT was evaluated for 11 canine cancer patients. The SI camera was capable of rendering surfaces for all blankets. The deviation between simulated and measured mean peak-to-peak breathing amplitude was within 0.6mm for all blankets. The sampling time was generally higher for the black fur than for the white and grey fur, for the measurement of both respiratory and sudden motion. The SI system could measure sudden motion within 62.5ms and detect motion with a frequency of 10Hz. The feasibility study of the canine patients showed that the SI system could be an important tool to ensure patient safety. By using this system we could ensure and document that 10 out of 11 canine patients had a total vector offset from the reference setup position<2mm immediately before and after irradiation. We have shown that SI can be used for surface guided FLASH-RT of canine patients. The SI system is currently not fast enough to interrupt a FLASH-RT beam while irradiating but with the short sampling time sudden motion can be detected. The beam can therefore be held just prior to irradiation, preventing treatment errors such as underdosing the target.

A Thermopile-Based Gas Flow Sensor with High Sensitivity for Noninvasive Respiration Monitoring.

In this work, a N/P polySi thermopile-based gas flow device is presented, in which a microheater distributed in a comb-shaped structure is embedded around hot junctions of thermocouples. The unique design of the thermopile and the microheater effectively enhances performance of the gas flow sensor leading to a high sensitivity (around 6.6 μV/(sccm)/mW, without amplification), fast response (around 35 ms), high accuracy (around 0.95%), and mood long-term stability. In addition, the sensor has the advantages of easy production and compact size. With such characteristics, the sensor is further used in real-time respiration monitoring. It allows detailed and convenient collection of respiration rhythm waveform with sufficient resolution. Information such as respiration periods and amplitudes can be further extracted to predict and alert of potential apnea and other abnormal status. It is expected that such a novel sensor could provide a new approach for respiration monitoring related noninvasive healthcare systems in the future.

On the Different Abilities of Cross-Sample Entropy and K-Nearest-Neighbor Cross-Unpredictability in Assessing Dynamic Cardiorespiratory and Cerebrovascular Interactions.

Nonlinear markers of coupling strength are often utilized to typify cardiorespiratory and cerebrovascular regulations. The computation of these indices requires techniques describing nonlinear interactions between respiration (R) and heart period (HP) and between mean arterial pressure (MAP) and mean cerebral blood velocity (MCBv). We compared two model-free methods for the assessment of dynamic HP-R and MCBv-MAP interactions, namely the cross-sample entropy (CSampEn) and k-nearest-neighbor cross-unpredictability (KNNCUP). Comparison was carried out first over simulations generated by linear and nonlinear unidirectional causal, bidirectional linear causal, and lag-zero linear noncausal models, and then over experimental data acquired from 19 subjects at supine rest during spontaneous breathing and controlled respiration at 10, 15, and 20 breaths·minute-1 as well as from 13 subjects at supine rest and during 60° head-up tilt. Linear markers were computed for comparison. We found that: (i) over simulations, CSampEn and KNNCUP exhibit different abilities in evaluating coupling strength; (ii) KNNCUP is more reliable than CSampEn when interactions occur according to a causal structure, while performances are similar in noncausal models; (iii) in healthy subjects, KNNCUP is more powerful in characterizing cardiorespiratory and cerebrovascular variability interactions than CSampEn and linear markers. We recommend KNNCUP for quantifying cardiorespiratory and cerebrovascular coupling.

Comparative Utility of Biofeedback Parameters in Predicting Perceived Relaxation

Background: Biofeedback is a mind-body technique where individuals track their biological functions to decrease stress. Aims and Objectives: There were two objectives in this study: (1) Understand the changes in biofeedback measurements, such as changes in respiration rate and skin temperature, during relaxation and (2) Correlate these changes to their perceived relaxation, which can help determine if certain biofeedback methods can quantify the extent of relaxation. Materials and Methods: Eleven volunteers of 55 ± 3 years were relaxed for 11 min in a controlled environment using a session from the “Calm” app. Four biofeedback parameters were measured during the relaxation period (skin temperature, heart rate, respiration rate, and skin resistance). Postrelaxation, subjects completed a questionnaire to report the changes in their perceived relaxation state. Average skin resistance significantly increased from 314.75 Ω to 393.33 Ω (P = 0.04, two-tailed paired t-test). The changes in all other parameters were statistically insignificant, with the average skin temperature increasing from 86.55°F to 88.04°F (P = 0.24), heart rate decreasing from 71.90 bpm to 71.36 bpm (P = 0.51), and respiration rate decreasing from 14.82 rpm to 14.72 rpm (P = 0.88). All participants reported some degree of relaxation. However, there was no significant correlation between the parameters and degree of subjective relaxation (P &gt; 0.05, Pearson's test). Conclusion: Only skin resistance showed a statistically significant change over the relaxation period, coinciding generally with the volunteers' perception of increased relaxation.

Accuracy of Mean Value of Central Venous Pressure from Monitor Digital Display: Influence of Amplitude of Central Venous Pressure during Respiration

BackgroundA simple measurement of central venous pressure (CVP)-mean by the digital monitor display has become increasingly popular. However, the agreement between CVP-mean and CVP-end (a standard method of CVP measurement by analyzing the waveform at end-expiration) is not well determined. This study was designed to identify the relationship between CVP-mean and CVP-end in critically ill patients and to introduce a new parameter of CVP amplitude (ΔCVP= CVPmax – CVPmin) during the respiratory period to identify the agreement/disagreement between CVP-mean and CVP-end. MethodsIn total, 291 patients were included in the study. CVP-mean and CVP-end were obtained simultaneously from each patient. CVP measurement difference (| CVP-mean – CVP-end |) was defined as the difference between CVP-mean and CVP-end. The ΔCVP was calculated as the difference between the peak (CVPmax) and the nadir value (CVPmin) during the respiratory cycle, which was automatically recorded on the monitor screen. Subjects with | CVP-mean – CVP-end | ≥ 2 mmHg were divided into the inconsistent group, while subjects with | CVP-mean – CVP-end | < 2 mmHg were divided into the consistent group. ResultsΔCVP was significantly higher in the inconsistent group [7.17(2.77) vs.5.24(2.18), p<0.001] than that in the consistent group. There was a significantly positive relationship between ΔCVP and | CVP-mean – CVP-end | (r=0.283, p <0.0001). Bland-Altman plot showed the bias was -0.61 mmHg with a wide 95% limit of agreement (–3.34, 2.10) of CVP-end and CVP-mean. The area under the receiver operating characteristic curves (AUC) of ΔCVP for predicting | CVP-mean – CVP-end | ≥ 2 mmHg was 0.709. With a high diagnostic specificity, using ΔCVP<3 to detect | CVP-mean – CVP-end | lower than 2mmHg (consistent measurement) resulted in a sensitivity of 22.37% and a specificity of 93.06%. Using ΔCVP>8 to detect | CVP-mean – CVP-end | >8 mmHg (inconsistent measurement) resulted in a sensitivity of 31.94% and a specificity of 91.32%. ConclusionsConclusions CVP-end and CVP-mean have statistical discrepancies in specific clinical scenarios. ΔCVP during the respiratory period is related to the variation of the two CVP methods. A high ΔCVP indicates a poor agreement between these two methods, whereas a low ΔCVP indicates a good agreement between these two methods.

Detailed dosimetric evaluation of inter-fraction and respiratory motion in lung stereotactic body radiation therapy based on daily 4D cone beam CT images

Objective. Periodic respiratory motion and inter-fraction variations are sources of geometric uncertainty in stereotactic body radiation therapy (SBRT) of pulmonary lesions. This study extensively evaluates and validates the separate and combined dosimetric effect of both factors using 4D-CT and daily 4D-cone beam CT (CBCT) dose accumulation scenarios. Approach. A first cohort of twenty early stage or metastatic disease lung cancer patients were retrospectively selected to evaluate each scenario. The planned-dose (3DRef) was optimized on a 3D mid-position CT. To estimate the dosimetric impact of respiratory motion (4DRef), inter-fractional variations (3DAcc) and the combined effect of both factors (4DAcc), three dose accumulation scenarios based on 4D-CT, daily mid-cone beam CT (CBCT) position and 4D-CBCT were implemented via CT-CT/CT-CBCT deformable image registration (DIR) techniques. Each scenario was compared to 3DRef. A separate cohort of ten lung SBRT patients was selected to validate DIR techniques. The distance discordance metric (DDM) was implemented per voxel and per patient for tumor and organs at risk (OARs), and the dosimetric impact for CT-CBCT DIR geometric errors was calculated. Main results. Median and interquartile range (IQR) of the dose difference per voxel were 0.05/2.69 Gy and −0.12/2.68 Gy for and For the IQR was considerably smaller −0.15/0.78 Gy. These findings were confirmed by dose volume histogram parameters calculated in tumor and OARs. For CT-CT/CT-CBCT DIR validation, DDM (95th percentile) was highest for heart (6.26 mm)/spinal cord (8.00 mm), and below 3 mm for tumor and the rest of OARs. The dosimetric impact of CT-CBCT DIR errors was below 2 Gy for tumor and OARs. Significance. The dosimetric impact of inter-fraction variations were shown to dominate those of periodic respiration in SBRT for pulmonary lesions. Therefore, treatment evaluation and dose-effect studies would benefit more from dose accumulation focusing on day-to-day changes then those that focus on respiratory motion.

Seasonal and tidal controls of the quantity and quality of dissolved organic matter at the marsh creek-estuarine interface

Tidal marshes are an important source of dissolved organic matter (DOM) to estuaries, and DOM plays an integral role in regulating water quality and health of coastal ecosystems. However, our understanding of temporal patterns of DOM quantity and composition at the marsh-estuarine interface is limited. This study investigated temporal changes in colored DOM (CDOM), an important component of dissolved organic carbon (DOC), exchanged across a brackish marsh-estuarine system. The sources of DOC were examined using stable carbon isotope values whereas the sources of CDOM were based on spectroscopic properties, including absorbance and fluorescence excitation-emission matrices (EEMs). Samplings at the Taskinas marsh creek-interface in Virginia (USA) captured a range of tidal stages, seasons, and environmental conditions over a three-year timeseries. Water from low and high tides was used to represent marsh and estuarine endmembers, respectively. Absorbance of CDOM at 440 nm ranged from 0.83 to 6.75 m-1, and the highest values were found during low tides (mean 2.78 ± 0.21 m −1). EEMs were composed of three humic-like components (C1, C2, C3) and one protein-like component (C4). Generally, the terrestrial humic-like (C1) and marine humic-like (C2) components were more abundant than other measured components. Seasonally, CDOM absorbance was highest in spring and summer. Contributions of CDOM from terrestrial sources increased in spring during periods of high runoff and peaked in summer during periods of high marsh productivity. Higher contributions of terrestrially derived CDOM were also measured in fall during periods of plant senescence. The aquatic component (C4) was higher during periods of increased phytoplankton production and during periods of high microbial respiration of terrestrial and planktonic organic matter. Although the amount of marsh exported CDOM varied with season, its composition varied considerably less, especially with respect to autochthonous CDOM. In a focused study in 2018, inferences about the terrestrial versus estuarine sources of CDOM were compared to source inferences made using measurements of stable carbon isotopes (δ13C) of DOC and DIC. δ13CDOC values ranged from −32.25 to −25.91‰, indicative of wetland organic matter and humic-like DOM; δ13CDIC ranged from −9.69 to −3.12‰, consistent with groundwater and estuarine sources. Overall, CDOM and stable isotope measurements indicate that humic materials were the primary source of DOM at this marsh-estuarine interface, including inputs from marsh plants and soils and products from microbial degradation of marsh and terrestrial materials, with lesser contributions from aquatic sources.

Multiscale partial information decomposition of dynamic processes with short and long-range correlations: theory and application to cardiovascular control

Objective. In this work, an analytical framework for the multiscale analysis of multivariate Gaussian processes is presented, whereby the computation of Partial Information Decomposition measures is achieved accounting for the simultaneous presence of short-term dynamics and long-range correlations. Approach. We consider physiological time series mapping the activity of the cardiac, vascular and respiratory systems in the field of Network Physiology. In this context, the multiscale representation of transfer entropy within the network of interactions among Systolic arterial pressure (S), respiration (R) and heart period (H), as well as the decomposition into unique, redundant and synergistic contributions, is obtained using a Vector AutoRegressive Fractionally Integrated (VARFI) framework for Gaussian processes. This novel approach allows to quantify the directed information flow accounting for the simultaneous presence of short-term dynamics and long-range correlations among the analyzed processes. Additionally, it provides analytical expressions for the computation of the information measures, by exploiting the theory of state space models. The approach is first illustrated in simulated VARFI processes and then applied to H, S and R time series measured in healthy subjects monitored at rest and during mental and postural stress. Main Results. We demonstrate the ability of the VARFI modeling approach to account for the coexistence of short-term and long-range correlations in the study of multivariate processes. Physiologically, we show that postural stress induces larger redundant and synergistic effects from S and R to H at short time scales, while mental stress induces larger information transfer from S to H at longer time scales, thus evidencing the different nature of the two stressors. Significance. The proposed methodology allows to extract useful information about the dependence of the information transfer on the balance between short-term and long-range correlations in coupled dynamical systems, which cannot be observed using standard methods that do not consider long-range correlations.

Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar

AbstractPedogenic carbonate is widespread at mid latitudes where warm and dry conditions favor soil carbonate growth from spring to fall. The mechanisms and timing of pedogenic carbonate formation are more ambiguous in the tropical domain, where long periods of soil water saturation and high soil respiration enhance calcite dissolution. This paper provides stable carbon, oxygen and clumped isotope values from Quaternary and Miocene pedogenic carbonates in the tropical domain of Myanmar, in areas characterized by warm (&gt;18°C) winters and annual rainfall up to 1,700 mm. We show that carbonate growth in Myanmar is delayed to the driest and coldest months of the year by sustained monsoonal rainfall from mid spring to late fall. The range of isotopic variability in Quaternary pedogenic carbonates can be solely explained by temporal changes of carbonate growth within the dry season, from winter to early spring. We propose that high soil moisture year‐round in the tropical domain narrows carbonate growth to the driest months and makes it particularly sensitive to the seasonal distribution of rainfall. This sensitivity is also enabled by high winter temperatures, allowing carbonate growth to occur outside the warmest months of the year. This high sensitivity is expected to be more prominent in the geological record during times with higher temperatures and greater expansion of the tropical realm. Clumped isotope temperatures, δ13C and δ18O values of tropical pedogenic carbonates are impacted by changes of both rainfall seasonality and surface temperatures; this sensitivity can potentially be used to track past tropical rainfall distribution.

A preliminary study on the effect of breathing on heart rate and blood pressure variability in patients with chronic diseases with abnormal sleep breathing

ObjectiveTo analyze the relationship between heart rate and blood pressure variability and respiration in patients with chronic respiratory disorders during night sleep.Methods16 patients with chronic diseases with abnormal sleep and respiration were included. Polysomnography was used to analyze the R‐R interval of nasal airflow electrocardiogram in normal stable breathing period and wave breathing period (OB) during nighttime sleep, and the variation of blood pressure based on finger‐tip photoelectric volume pulse wave (PPG) and pulse wave conduction time (PTT).The ResultsThe ratio of the number of respiratory cycles to the number of heart rate variability cycles (B‐n / HRV‐n) was (1.00 ± 0.04), to the number of systolic blood pressure (SBP) variability cycles (B‐n / SBPV‐n) was (1.02 ± 0.10), and diastolic blood pressure (DBP) variability cycles (B‐n / DBPV‐B‐n) was (1.00 ± 0.11), The ratio of respiratory cycle number to heart rate variability cycle number (OB‐n / OB‐HRV‐n) during OB was (1.22 ± 0.18). The ratio of respiratory cycle number to systolic blood pressure variation cycle number (OB‐n / OB‐SBPV‐n) was (1.19 ± 0.22), and DBP(OB‐n / OB‐DBPV‐n) was (1.15 ± 0.15), both of which were higher than those in normal stable breathing period (P &lt; 0.01). During the normal and stable breathing period, the average amplitude of heart rate variability (HRV‐B‐M) of each respiratory cycle rhythm was (2.64 ± 1.59) bpm, the average amplitude of systolic blood pressure variability (SBPV‐B‐M) of each respiratory cycle rhythm was (2.83 ± 1.22) mmhg, and diastolic blood pressure variability (DBPV‐B‐M) was (2.40 ± 0.86) mmhg, which were slightly higher than those of the normal people, but there was no significant difference compared with the normal people and hypertensive patients without sleep apnea. The mean amplitude of heart rate variability (OB‐HRV‐B‐M) at each respiratory cycle rhythm in OB period was (3.56 ± 1.57) bpm, the mean amplitude of heart rate variability (OB‐HRV‐OB‐M) at each OB period was (13.75 ± 4.25) bpm, The average amplitude of diastolic blood pressure variability (OB‐DBPV‐B‐M) was (2.82 ± 1.95) mmhg, which was higher than that in normal stable respiratory period. The difference between OB‐SBPV‐B‐M and normal stable respiratory systolic blood pressure variability (SBPV‐B‐M) was significant. The variation range of systolic blood pressure (OB‐SBPV‐OB‐M) in each OB cycle was (16.83 ± 9.29) mmhg, which was much larger than that of OB‐SBPV‐B‐M and SBPV‐B‐M (P &lt; 0.01).ConclusionThe variations of blood pressure and heart rate in patients with chronic respiratory disorders during normal and stable breathing at night are similar to those in normal people and hypertensive patients without sleep respiratory disorders in the same period in our laboratory, The variation amplitude of heart rate and blood pressure in wavy breathing period was greater than that in normal and stable breathing period .confirming that the variation of heart rate and blood pressure was respiratory origin.

The significance of a concomitant clavicle fracture in flail chest patients: incidence, concomitant injuries, and outcome of 12,348 polytraumata from the TraumaRegister DGU®

PurposeIsolated clavicle fractures (CF) rarely show complications, but their influence in the thorax trauma of the seriously injured still remains unclear. Some authors associate CF with a higher degree of chest injuries; therefore, the clavicle is meant to be a gatekeeper of the thorax.MethodsA retrospective analysis of the TraumaRegister DGU® (project 2017-10) was carried out involving the years 2009–2016 (ISS ≥ 16, primary admission to a trauma center). Cohort formation: unilateral and bilateral flail chest injuries (FC), respectively, with and without a concomitant CF.Results73,141 patients (26.5% female) met the inclusion criteria and 12,348 had flail chest injuries (FC; 20.0% CF; 67.7% monolateral FC), 25,425 other rib fractures (17.7% CF), and 35,368 had no rib fractures (6.5% CF). On average, monolateral FC patients were 56.0 ± 17.9 years old and bilateral FC patients were 57.7 ± 19 years old. The ISS in unilateral and bilateral FC were 29.1 ± 11.7 and 42.2 ± 12.9 points, respectively. FC with a CF occurred more frequently with bicycle and motorbike injuries in monolateral FC and pedestrians in bilateral FC injuries and less frequently due to falls. Patients with a CF in addition to a FC had longer hospital and ICU stays, underwent artificially respiration for longer periods, and died less often than patients without a CF. The effects were highly significant in bilateral FC. CF indicates more relevant concomitant injuries of the lung, scapula, and spinal column. Moreover, CF was associated with more injuries of the extremities in monolateral CF.ConclusionDue to the relevance of a concomitant CF fracture in FC, diagnostics should focus on finding CFs or rule them out. Combined costoclavicular injuries are associated with a significantly higher degree of thoracic injuries and longer hospital stays.

Causality of cortical and cardiovascular activity during cyclic alternating pattern in non-rapid eye movement sleep.

The dynamic interplay between central and autonomic nervous system activities plays a pivotal role in orchestrating sleep. Macrostructural changes such as sleep-stage transitions or phasic, brief cortical events elicit fluctuations in neural outflow to the cardiovascular system, but the causal relationships between cortical and cardiovascular activities underpinning the microstructure of sleep are largely unknown. Here, we investigate cortical-cardiovascular interactions during the cyclic alternating pattern (CAP) of non-rapid eye movement sleep in a diverse set of overnight polysomnograms. We determine the Granger causality in both 507 CAP and 507 matched non-CAP sequences to assess the causal relationships between electroencephalography (EEG) frequency bands and respiratory and cardiovascular variables (heart period, respiratory period, pulse arrival time and pulse wave amplitude) during CAP. We observe a significantly stronger influence of delta activity on vascular variables during CAP sequences where slow, low-amplitude EEG activation phases (A1) dominate than during non-CAP sequences. We also show that rapid, high-amplitude EEG activation phases (A3) provoke a more pronounced change in autonomic activity than A1 and A2 phases. Our analysis provides the first evidence on the causal interplay between cortical and cardiovascular activities during CAP. Granger causality analysis may also be useful for probing the level of decoupling in sleep disorders. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.