Respiratory Period Research Articles

Heart rate variability characteristics of patients with irritable bowel syndrome and associations with symptoms.

Disturbed brain-gut interactions are assumed to be of importance for symptom generation in patients with irritable bowel syndrome (IBS). The autonomic nervous system (ANS) is part of the bidirectional brain-gut communication, but previous studies in IBS show diverging results. We aimed to identify subgroups of IBS patients with distinct ANS characteristics differentiating them from healthy controls (HC), and to study associations between ANS status and symptoms. Heart rate variability (HRV) was measured in IBS patients and HC (Holter monitoring: supine and standing positions with controlled respiration and ambulatory 24-hour period). Frequency (5minutes, supine, standing) and time domains (24hours, day, night) were analyzed. Validated questionnaires were used to measure gastrointestinal and psychological symptoms in patients. Patients and HC were compared on a univariate and multivariate level (principal component analysis [PCA] and orthogonal partial least squares discriminatory analysis (OPLS-DA)). We analyzed 158 IBS patients (Rome III) and 39 HC. Patients differed significantly from HC in HRV parameters during daytime and in standing position. In the PCA, a majority of patients overlapped with HC, but the weighted means differed (P<.01). A subset of patients (n=30; 19%) with an aberrant global HRV profile was identified through PCA and OPLS-DA; these patients reported more severe symptoms of frequent (P<.05) and loose stools (P=.03), as well as urgency (P=.01). Altered ANS function was demonstrated in patients with IBS, and this might be of particular relevance for symptoms in a subset of the patients.

Smart textile for respiratory monitoring and thoraco-abdominal motion pattern evaluation.

The use of wearable systems for monitoring vital parameters has gained wide popularity in several medical fields. The focus of the present study is the experimental assessment of a smart textile based on 12 fiber Bragg grating sensors for breathing monitoring and thoraco-abdominal motion pattern analysis. The feasibility of the smart textile for monitoring several temporal respiratory parameters (ie, breath-by-breath respiratory period, breathing frequency, duration of inspiratory and expiratory phases), volume variations of the whole chest wall and of its compartments is performed on 8 healthy male volunteers. Values gathered by the textile are compared to the data obtained by a motion analysis system, used as the reference instrument. Good agreement between the 2 systems on both respiratory period (bias of 0.01 seconds), breathing frequency (bias of -0.02 breaths/min) and tidal volume (bias of 0.09 L) values is demonstrated. Smart textile shows good performance in the monitoring of thoraco-abdominal pattern and its variation, as well.

C-FMCW Based Contactless Respiration Detection Using Acoustic Signal

Recent advances in ubiquitous sensing technologies have exploited various approaches to monitoring vital signs. One of the vital signs is human respiration which typically requires reliable monitoring with low error rate in practice. Previous works in respiration monitoring however either incur high cost or suffer from poor error rate. In this paper, we propose a Correlation based Frequency Modulated Continuous Wave method (C-FMCW) which is able to achieve high ranging resolution. Based on C-FMCW, we present the design and implementation of an audio-based highly-accurate system for human respiration monitoring, leveraging on commodity speaker and microphone widely available in home environments. The basic idea behind the audio-based method is that when a user is close to a pair of speaker and microphone, body movement during respiration causes periodic audio signal changes, which can be extracted to obtain the respiration rate. However, several technical challenges exist when applying C-FMCW to detect respiration with commodity acoustic devices. First, the sampling frequency offset between speakers and microphones if not being corrected properly would cause high ranging errors. Second, the uncertain starting time difference between the speaker and microphone varies over time. Moreover, due to multipath effect, weak periodic components due to respiration can easily be overwhelmed by strong static components in practice. To address those challenges, we 1) propose an algorithm to compensate dynamically acoustic signal and counteract the offset between speaker and microphone; 2) co-locate speaker and microphone and use the received signal without reflection (self-interference) as a reference to eliminate the starting time difference; and 3) leverage the periodicity of respiration to extract weak periodic components with autocorrelation. Extensive experimental results show that our system detects respiration in real environments with the median error lower than 0.35 breaths/min, outperforming the state-of-the-arts.

Swallowing Muscle Dysfunction and Residual Factor of Dysphagia with Community- Acquired Pneumonia in the Elderly

Objectives: This study aimed to elucidate the characteristics of swallowing function, including swallowing muscle activity, and the residual factors of dysphagia in elderly patients with community-acquired pneumonia (CAP). Study design: A total of 163 subjects were included in the study. The subjects were classified into an oral intake independent group (severe aspiration), which comprises subjects who have a total fiberoptic endoscopic evaluation of swallowing (FEES) score of seven or more, and an oral intake restriction group (no aspiration or mild aspiration), which comprises subjects who have a total FEES score of less than seven. These two groups were compared, and the residual factors of dysphagia were analyzed. Results: Significant differences between the two groups were found in the repetitive saliva swallowing test, geriatric nutritional risk index, pneumonia severity, swallowing muscle activity, and respiratory rate fasting period. Multivariate logistic regression analysis revealed that the duration of swallowing muscle activity (OR 15.7, 95% CI 1.29 to 19.66; P=0.031) and respiratory rate (OR 1.22, 95% CI 1.03 to 1.58; P=0.026) were the residual factors of dysphagia in elderly people with CAP. Conclusions: This study highlighted the importance of an early approach that focuses on swallowing function and respiratory rate in the rehabilitation of elderly people with dysphagia and CAP. The results for the residual factors of dysphagia provide new evidence in the field of rehabilitation and will help reduce hospitalization and readmission for pneumonia.

6. Study of the feasibility of the implementation of VMAT stereotactic radiotherapy for pulmonary sites

Introduction The objective of this study is to investigate the feasibility of using the VMAT treatment technique during pulmonary stereotactic treatment. The related perturbations caused by the movements come from two sources, the dose gradient or the dose blur and the interplay effect. These two effects will be studied in order to determine their impact on the dose distribution according to the amplitude of the movement and their consequences on the realization of treatments in free-breathing. Methods The study was performed retrospectively for 14 patients treated in stereotactic conditions by coplanar fixed fields. All patients benefited from a 4D scanner acquisition to obtain 3D series images on 10 respiratory phases [0–90%], and of an the average 3D image series (AVE). The tumor volumes and amplitudes were [22.8 ± 18.1] cm3 and [8.5 ± 8.2] mm. Dosimetric’s plan of each patient was performed on the Eclipse TPS with the Acuros V.11 algorithm and a 1 mm calculation grid on the AVE 3D image series. These planes have been optimized for ballistics of two half-arcs, collimator at 45°, and a hypo-fractionation of 5 ∗ 10 Gy. The set has been validated by a medical physicist and radiotherapist. Then, each scheduling was carried over to the AVE series of heterogeneous Cheese phantom (Gammex) acquired in 4D thanks to a dynamic CIRS platform (Model 008) reproducing the patient’s respiratory signals. For each patient, 6 measurements per Gafchromic EBT3 film were made on a Novalis Truebeam STX (Varian, Brainlab) in the Cheese phantom placed on the dynamic platform: 1 reference film per half-arc without movement, 1 film per half-arcs, starting the irradiation at the phase 0% of the respiratory signal of the patient and 1 film by half arcs starting the irradiation at the phase 50% of the patient’s respiratory signal. The RIT software was used to compare films to each other and to the TPS dose calculations to determine the interplay effect and the dose gradient effect, respectively. Results For the amplitudes and respiratory periods of the 14 patients, the interplay effect is negligible because the differences are small between the films acquired by starting at the 0% phase and those acquired at the 50% phase with an average gamma index of 98.9 ± 1.8% in 2%/2 mm. On contrary, the dose gradient effect (comparison TPS vs Film at 0% and 50%) can be seen from 6.5 mm amplitude with a mean gamma index of 3%/3 mm passing from 99.5 ± 0.7% for the amplitudes from 0 to 6.5 mm to 87.2 ± 10.9% for the amplitudes from 6.5 to 10 mm. The gamma index of 2%/2 mm increases from 94.0 ± 4.9% to 74.2 ± 13.4%. Conclusions This study on the feasibility of the implementation of pulmonary stereotaxic in VMAT shows that it is possible to treat a patient in free-breathing up to 6 mm of motion amplitude. From this limit, it is necessary to proceed under the control of a respiratory affection system. Moreover, the interplay effect does not affect distribution’s dose and only the effect of the dose gradient is visible for these configurations.

Image acquisition optimization of a limited-angle intrafraction verification (LIVE) system for lung radiotherapy.

Limited-angle intrafraction verification (LIVE) has been previously developed for four-dimensional (4D) intrafraction target verification either during arc delivery or between three-dimensional (3D)/IMRT beams. Preliminary studies showed that LIVE can accurately estimate the target volume using kV/MV projections acquired over orthogonal view 30° scan angles. Currently, the LIVE imaging acquisition requires slow gantry rotation and is not clinically optimized. The goal of this study is to optimize the image acquisition parameters of LIVE for different patient respiratory periods and gantry rotation speeds for the effective clinical implementation of the system. Limited-angle intrafraction verification imaging acquisition was optimized using a digital anthropomorphic phantom (XCAT) with simulated respiratory periods varying from 3 s to 6 s and gantry rotation speeds varying from 1°/s to 6°/s. LIVE scanning time was optimized by minimizing the number of respiratory cycles needed for the four-dimensional scan, and imaging dose was optimized by minimizing the number of kV and MV projections needed for four-dimensional estimation. The estimation accuracy was evaluated by calculating both the center-of-mass-shift (COMS) and three-dimensional volume-percentage-difference (VPD) between the tumor in estimated images and the ground truth images. The robustness of LIVE was evaluated with varied respiratory patterns, tumor sizes, and tumor locations in XCAT simulation. A dynamic thoracic phantom (CIRS) was used to further validate the optimized imaging schemes from XCAT study with changes of respiratory patterns, tumor sizes, and imaging scanning directions. Respiratory periods, gantry rotation speeds, number of respiratory cycles scanned and number of kV/MV projections acquired were all positively correlated with the estimation accuracy of LIVE. Faster gantry rotation speed or longer respiratory period allowed less respiratory cycles to be scanned and less kV/MV projections to be acquired to estimate the target volume accurately. Regarding the scanning time minimization, for patient respiratory periods of 3-4 s, gantry rotation speeds of 1°/s, 2°/s, 3-6°/s required scanning of five, four, and three respiratory cycles, respectively. For patient respiratory periods of 5-6 s, the corresponding respiratory cycles required in the scan changed to four, three, and two cycles, respectively. Regarding the imaging dose minimization, for patient respiratory periods of 3-4 s, gantry rotation speeds of 1°/s, 2-4°/s, 5-6°/s required acquiring of 7, 5, 4 kV and MV projections, respectively. For patient respiratory periods of 5-6 s, 5 kV and 5 MV projections are sufficient for all gantry rotation speeds. The optimized LIVE system was robust against breathing pattern, tumor size and tumor location changes. In the CIRS study, the optimized LIVE system achieved the average center-of-mass-shift (COMS)/volume-percentage-difference (VPD) of 0.3 ± 0.1 mm/7.7 ± 2.0% for the scanning time priority case, 0.2 ± 0.1 mm/6.1 ± 1.2% for the imaging dose priority case, respectively, among all gantry rotation speeds tested. LIVE was robust against different scanning directions investigated. The LIVE system has been preliminarily optimized for different patient respiratory periods and treatment gantry rotation speeds using digital and physical phantoms. The optimized imaging parameters, including number of respiratory cycles scanned and kV/MV projection numbers acquired, provide guidelines for optimizing the scanning time and imaging dose of the LIVE system for its future evaluations and clinical implementations through patient studies.

Photosynthesis enhanced dark respiration in three marine phytoplankton species

The effects of previous photosynthetic activity on dark respiration rates were investigated in Heterocapsa rotundata (Dinophyceae), Rhodomonas salina (Cryptophyceae) and Thalassiosira weissflogii (Coscinodiscophyceae). Dark respiration rates were measured after 1 to 3h of light exposure in 12 bottles where incubation irradiances ranging from 0 to 600μmolphotonsm−2s−1. The results showed that the dark respiration increases with increasing light exposure (both irradiance and duration) in all exponentially growing cultures but not in two experiments with cultures in stationary phase (T. weissflogii). This relationship could be described by a linear model for all species, relating respiration to the previous accumulated photosynthetic product with a slope of about 0.035h−1, indicating a growth-related respiration of 3.5% per hour of the newly fixed carbon. The maximum respiration rate (Rmax) was estimated from both light dose and accumulated photosynthetic product using a non-linear model. Although Rmax and light-saturated gross photosynthesis (Pgmax) varied between the three species, a similar Rmax: Pgmax ratio of ~0.12 was found. The maintenance respiration rates which are comparable with maintenance respiration rates from literature, varied from 0.004 to 0.02molO2g−1Chlh−1 for the three species. Overall, this study suggests a diel periodicity of phytoplankton respiration driven by accumulation of newly fixed carbon in light. The consequence is a decreasing respiration rate during the night or during long dark incubations.

Smart Textile Based on 12 Fiber Bragg Gratings Array for Vital Signs Monitoring

Over the last decades, wearable systems have gained interest for vital signs monitoring. Among several technologies, fiber Bragg grating (FBG) sensors are becoming popular for some advantages, such as high sensitivity, magnetic resonance compatibility, and the capability of performing distributed measurements. The aim of this paper is twofold: the description of the design and the fabrication of a smart textile based on an array of 12 FBGs; its feasibility assessment for monitoring respiratory parameters (i.e., respiratory rate, respiratory period, and inspiratory and expiratory periods) and heart rate on healthy volunteers in two positions (standing and supine). The increased number of FBGs embedded in this system with respect to previous developed prototypes aims at improving its accuracy in the estimation of the mentioned parameters. Future testing will be performed to investigate if the proposed solution allows improving the measurements of respiratory volumes exchanges and in new scenarios (e.g., sports medicine, including walking, running, and cycling activities).

K-band Doppler radar for contact-less overnight sleep marker assessment: a pilot validation study.

An estimated 45million persons in Europe are annually subjected to sleep-wake disorders. State-of-the-art polysomnography provides sophisticated insights into sleep (patho)physiology. A drawback of the method, however, is the obtrusive setting dependent on a clinical-based sleep laboratory with high operational costs. A contact-less prototype was developed to monitor limb movements and vital signs during sleep. A dual channel K-band Doppler radar transceiver captured limb movements and periodic chest wall motion due to respiration and heart activity. A wavelet transform based multi-resolution analysis (MRA) approach isolated limb movements, respiration, and heart rate from the demodulated signal. A test bench setup characterized the prototype simulating near physiological chest wall motions caused by periodic respiration and heartbeats in humans. Single- and multi-tone test bench simulations showed extremely low relative percentage errors of the prototype for respiratory and heart rate within -2 and 1%. The performance of the prototype was validated in overnight comparative studies, involving two healthy volunteers, with polysomnography as the reference. The prototype has successfully classified limb movements, with a sensitivity and specificity of 88.9 and 76.8% respectively, and has achieved accurate respiratory and heart rate measurement performance with overall absolute errors of 1 breath per minute for respiration and 3 beats per minute for heart rate. This pilot study shows that K-band Doppler radar and wavelet transform MRA seem to be valid for overnight sleep marker assessment. The contact-less approach might offer a promising solution for home-based sleep monitoring and assessment.

Relações entre o comportamento climático e doenças respiratórias em Barreiras/BA

A influência de parâmetros meteorológicos e antrópicos nas condições da saúde da população permitem, à ciência geográfica, analisar essa relação, seja por meio de métodos estatísticos ou técnicas de análise espacial. Na cidade de Barreiras, localizada na região Oeste da Bahia, o incremento populacional nas últimas quatro décadas foi expressivo com aproximadamente 3.100 hab.ano-1 no período de 1980 a 2015. As condições atmosféricas podem ser apontadas como um dos principais condicionantes a problemas de saúde pública a esta população, com destaque para as doenças do aparelho respiratório, que ocupam a terceira posição das causas de internações na cidade de Barreiras/BA, o que demanda ações das diversas esferas de gestão. Desta forma, buscou-se neste trabalho realizar uma análise geográfica, com investigação da ocorrência das principais doenças respiratórias e os períodos de maior incidência, a partir dos dados disponíveis no sistema DATASUS, bem como a verificação de dados meteorológicos utilizados na associação entre os mesmos, no período de 2000 a 2010. Resultados apontam a existência de uma associação entre o comportamento das condições atmosféricas e a ocorrência de doenças do aparelho respiratório, com destaque para as faixas etárias de crianças e idosos.

Mandibular Movements As Accurate Reporters of Respiratory Effort during Sleep: Validation against Diaphragmatic Electromyography

Mandibular movements (MM) are considered as reliable reporters of respiratory effort (RE) during sleep and sleep disordered breathing (SDB), but MM accuracy has never been validated against the gold standard diaphragmatic electromyography (EMG-d). To assess the degree of agreement between MM and EMG-d signals during different sleep stages and abnormal respiratory events. Twenty-five consecutive adult patients with SDB were studied by polysomnography (PSG) that also included multipair esophageal diaphragm electromyography and a magnetometer to record MM. EMG-d activity (microvolt) and MM (millimeter) amplitudes were extracted by envelope processing. Agreement between signals amplitudes was evaluated by mixed linear regression and cross-correlation function and in segments of PSG including event-free and SDB periods. The average total sleep time was 370 ± 18 min and the apnea hypopnea index was 24.8 ± 5.2 events/h. MM and EMG-d amplitudes were significantly cross-correlated: median r (95% CI): 0.67 (0.23-0.96). A mixed linear model showed that for each 10 µV of increase in EMG-d activity, MM amplitude increased by 0.28 mm. The variations in MM amplitudes (median range: 0.11-0.84 mm) between normal breathing, respiratory effort-related arousal, obstructive, mixed, and central apnea periods closely corresponded to those observed with EMG-d activity (median range: 2.11-8.23 µV). MM amplitudes change proportionally to diaphragmatic EMG activity and accurately identify variations of RE during normal sleep and SDB.

Hydrochar enhances growth of poplar for bioenergy while marginally contributing to direct soil carbon sequestration

AbstractHydrothermal carbonization (HTC) has been proposed as an alternative method to pyrolysis for producing C‐rich amendments for soil C sequestration. However, the use of hydrochar (HC) as soil amendment is still controversial due to the limited information on the potential benefits and trade‐offs that may follow its application into soil. This study investigated the effects of HC starting from maize silage on plant growth in a 2‐year controlled experiment on poplar for bioenergy and evaluated HC stability in soil by periodic soil respiration and isotopic (δ13C) measurements. HC application caused a substantial and significant increase in plant biomass after one and two years after planting, and no evident signs of plant diseases were evident. Isotopic analysis on soil and CO2 efflux showed that slightly less than half of the C applied was re‐emitted as CO2 within 12 months. On the contrary, considering that the difference in the amount of N fixed in wood biomass in treated and not‐treated poplars was 16.6 ± 4.8 g N m−2 and that the soil N stocks after one year since application did not significantly change, we estimated that approximately 85% of the N applied with HC could have been potentially lost as leachate or volatilized into the atmosphere as N2O, in response to nitrification/denitrification processes in the soil. Thus, the permanence, additionality and leakage of C sequestration strategy using HC are deeply discussed.

Investigation of flow characteristics in regions of intermittent formation of flow separation inside the nasal cavity

We used computational fluid dynamics to study airflow characteristics in the space between the bulla and the middle turbinate (Region P1) and the superior meatus (Region P2) of the human upper airway, which exhibit intermittent flow separation. For comparison, we examined airflow passage in the inferior meatus (Region N), where large-scale flow separation develops. We assessed six different flow rates, based on realistic human respiration data representing one full period of respiration, in an anatomically correct numerical model. The simulation results showed that airflow in regions P1 and P2 had a relatively smaller separation bubble with a larger variation of bubble size with time, whereas region N exhibited a more gradually changing, two-dimensional rotation-like motion. Distinctive features of flow characteristics in regions P1 and P2 were relatively low Reynolds number, higher curvature of streamlines of the local main flow, with the existence of locations exhibiting intermittent occurrence of relatively quite high level of wall shear during inspiration.

Validation of a leg movements count and periodic leg movements analysis in a custom polysomnography system

BackgroundPeriodic leg movements (PLM) during sleep (PLMS) are considered strongly related to restless legs syndrome (RLS), and are associated with polymorphisms in RLS risk genes. Various software for automatic analysis of PLMS are available, but only few of them have been validated. Aim of this study was to validate a leg movements count and analysis integrated in a commercially available polysomnography (PSG) system against manual scoring.MethodsTwenty RLS patients with a PLMS index > 20/h and 20 controls with a PLMS index < 5/h were included. Manual and computerized scoring of leg movements (LM) and PLM was performed according to the standard American Academy of Sleep Medicine (AASM) criteria. LM and PLM indices during sleep and wakefulness, the rate of PLMS associated with respiratory events, intermovement interval and periodicity indices were manually and automatically scored.ResultsThe correlation between manual and computerized scoring was high for all investigated parameters (Spearman correlation coefficients 0.751–0.996, p < 0.001; intraclass correlation coefficients 0.775–0.999, p < 0.001). Bland-Altman plots showed high agreement between manual and automatic analysis.ConclusionsThis study validated an automatic LM count and PLM analysis against the gold standard manual scoring according to AASM criteria. The data demonstrate that the software used in this study has an outstanding performance for computerized LM and PLM scoring, and LM and PLM indices generated with this software can be reliably integrated in the routine PSG report. This automatic analysis is also an excellent tool for research purposes.

Multiscale CT-Based Computational Modeling of Alveolar Gas Exchange during Artificial Lung Ventilation, Cluster (Biot) and Periodic (Cheyne-Stokes) Breathings and Bronchial Asthma Attack

An airflow in the first four generations of the tracheobronchial tree was simulated by the 1D model of incompressible fluid flow through the network of the elastic tubes coupled with 0D models of lumped alveolar components, which aggregates parts of the alveolar volume and smaller airways, extended with convective transport model throughout the lung and alveolar components which were combined with the model of oxygen and carbon dioxide transport between the alveolar volume and the averaged blood compartment during pathological respiratory conditions. The novel features of this work are 1D reconstruction of the tracheobronchial tree structure on the basis of 3D segmentation of the computed tomography (CT) data; 1D−0D coupling of the models of 1D bronchial tube and 0D alveolar components; and the alveolar gas exchange model. The results of our simulations include mechanical ventilation, breathing patterns of severely ill patients with the cluster (Biot) and periodic (Cheyne-Stokes) respirations and bronchial asthma attack. The suitability of the proposed mathematical model was validated. Carbon dioxide elimination efficiency was analyzed in all these cases. In the future, these results might be integrated into research and practical studies aimed to design cyberbiological systems for remote real-time monitoring, classification, prediction of breathing patterns and alveolar gas exchange for patients with breathing problems.

周期性呼吸・無呼吸発作に対して腹臥位が呼吸安定化に効果的であった超低出生体重児の1例

周期性呼吸・無呼吸発作に対して腹臥位が呼吸安定化に効果的であった超低出生体重児の1例

Transient Dynamics Simulation of Airflow in a CT-Scanned Human Airway Tree: More or Fewer Terminal Bronchi?

Using computational fluid dynamics (CFD) method, the feasibility of simulating transient airflow in a CT-based airway tree with more than 100 outlets for a whole respiratory period is studied, and the influence of truncations of terminal bronchi on CFD characteristics is investigated. After an airway model with 122 outlets is extracted from CT images, the transient airflow is simulated. Spatial and temporal variations of flow velocity, wall pressure, and wall shear stress are presented; the flow pattern and lobar distribution of air are gotten as well. All results are compared with those of a truncated model with 22 outlets. It is found that the flow pattern shows lobar heterogeneity that the near-wall air in the trachea is inhaled into the upper lobe while the center flow enters the other lobes, and the lobar distribution of air is significantly correlated with the outlet area ratio. The truncation decreases airflow to right and left upper lobes and increases the deviation of airflow distributions between inspiration and expiration. Simulating the transient airflow in an airway tree model with 122 bronchi using CFD is feasible. The model with more terminal bronchi decreases the difference between the lobar distributions at inspiration and at expiration.

Winter respiratory C losses provide explanatory power for net ecosystem productivity

AbstractAccurate predictions of net ecosystem productivity (NEPc) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEPc (e.g., climate and nutrients) are not entirely understood yet, particularly when considering the influence of past periods. Here we explored the explanatory power of the compensation day (cDOY)—defined as the day of year when winter net carbon losses are compensated by spring assimilation—for NEPc in 26 forests in Europe, North America, and Australia, using different NEPc integration methods. We found cDOY to be a particularly powerful predictor for NEPc of temperate evergreen needleleaf forests (R2 = 0.58) and deciduous broadleaf forests (R2 = 0.68). In general, the latest cDOY correlated with the lowest NEPc. The explanatory power of cDOY depended on the integration method for NEPc, forest type, and whether the site had a distinct winter net respiratory carbon loss or not. The integration methods starting in autumn led to better predictions of NEPc from cDOY then the classical calendar method starting 1 January. Limited explanatory power of cDOY for NEPc was found for warmer sites with no distinct winter respiratory loss period. Our findings highlight the importance of the influence of winter processes and the delayed responses of previous seasons' climatic conditions on current year's NEPc. Such carry‐over effects may contain information from climatic conditions, carbon storage levels, and hydraulic traits of several years back in time.

Kölliker-Fuse nuclei regulate respiratory rhythm variability via a gain-control mechanism.

Respiration varies from breath to breath. On the millisecond timescale of spiking, neuronal circuits exhibit variability due to the stochastic properties of ion channels and synapses. Does this fast, microscopic source of variability contribute to the slower, macroscopic variability of the respiratory period? To address this question, we modeled a stochastic oscillator with forcing; then, we tested its predictions experimentally for the respiratory rhythm generated by the in situ perfused preparation during vagal nerve stimulation (VNS). Our simulations identified a relationship among the gain of the input, entrainment strength, and rhythm variability. Specifically, at high gain, the periodic input entrained the oscillator and reduced variability, whereas at low gain, the noise interacted with the input, causing events known as "phase slips", which increased variability on a slow timescale. Experimentally, the in situ preparation behaved like the low-gain model: VNS entrained respiration but exhibited phase slips that increased rhythm variability. Next, we used bilateral muscimol microinjections in discrete respiratory compartments to identify areas involved in VNS gain control. Suppression of activity in the nucleus tractus solitarii occluded both entrainment and amplification of rhythm variability by VNS, confirming that these effects were due to the activation of the Hering-Breuer reflex. Suppressing activity of the Kölliker-Fuse nuclei (KFn) enhanced entrainment and reduced rhythm variability during VNS, consistent with the predictions of the high-gain model. Together, the model and experiments suggest that the KFn regulates respiratory rhythm variability via a gain control mechanism.

Abstract PR199

Background & Objectives: Remifentanil as a potent ultra short opioid agonist, rapidly metabolized in mother and fetus is becoming more and more popular in labor analgesia as alternative to neuroaxial analgesia. Recent studies comparing epidural with remifentanil analgesia showed us much better pain relieve scores in epidural analgesia; however there was no big difference in satisfaction scores in both groups. In this study, we compared maternal and neonatal side effects, as well as patient satisfaction. Materials & Methods: We analyzed 55 patients, ASA I, at term admitted for spontaneous labor and divided into two groups. The first group (30 patients) received continuous epidural infusion (0.1% Bupivacain and Fentanyl 2 μg/ml) 10 ml/h beginning immediately after the initial dose. The second group (25 patients) received iPCA with remifentanil titrated from 20 mcg up to a maximum bolus dose of 50 mcg with a lockout interval of 2 minutes. Our primary outcome was maternal and neonatal safety. We evaluate pulse oximetry (SpO2), heart rate, respiratory rate, sedation scores, Apgar scores and umbilical cord blood gas analysis. Supplementary oxygen was administered continuously during the respiratory monitoring period. The secondary outcome was efficacy evaluated through hourly pain scores and satisfaction scores (two different 10 point Visual Analoge Scales). Results: Mean SpO2 was lower in the remifentanil group 96.4% vs 98.2 for epidural group. No respiratory depression (respiration rate <9 or SpO2 <90%) was found in both groups. The Ramsay sedation scores were significantly higher in the remifentanil group, P < 0.0001. Apgar scores and neonatal respiratory outcomes were similar. As expected, remifentanil was inferior to epidural analgesia with respect to the pain scores at all time points, P < 0.0001. No significant difference between the two groups in maternal satisfaction (8.9 for the remifentanil group and 9.1 for the epidural group). Conclusion: IPCA with remifentanil provides satisfactory level of labor analgesia, with lower SpO2 and more sedation. It can be a viable alternative to epidural analgesia, but continuous monitoring and oxygen supply is mandatory.