Normal Breathing Pattern Research Articles

RETRACTED ARTICLE: Diagnosis of the Hypopnea syndrome in the early stage

Hypopnea syndrome is a chronic respiratory disease that is characterized by repetitive episodes of breathing disruptions during sleep. Hypopnea syndrome is a systemic disease that manifests respiratory problems; however, more than 80% of Hypopnea syndrome patients remain undiagnosed due to complicated polysomnography. Objective assessment of breathing patterns of an individual can provide useful insight into the respiratory function unearthing severity of Hypopnea syndrome. This paper explores a novel approach to detect incognito Hypopnea syndrome as well as provide a contactless alternative to traditional medical tests. The proposed method is based on S-Band sensing technique (including a spectrum analyzer, vector network analyzer, antennas, software-defined radio, RF generator, etc.), peak detection algorithm and Sine function fitting for the observation of breathing patterns and characterization of normal or disruptive breathing patterns for Hypopnea syndrome detection. The proposed system observes the human subject and changes in the channel frequency response caused by Hypopnea syndrome utilizing a wireless link between two monopole antennas, placed 3 m apart. Commercial respiratory sensors were used to verify the experimental results. By comparing the results, it is found that for both cases, the pause time is more than 10 s with 14 peaks. The experimental results show that this technique has the potential to open up new clinical opportunities for contactless and accurate Hypopnea syndrome monitoring in a patient-friendly and flexible environment.

Pressure biofeedback unit to assess and train lumbopelvic stability in supine individuals with chronic low back pain.

[Purpose] To determine if pressure biofeedback unit readings are related to abdominal muscle activation and centre of pressure displacement as well as to test the effects of using it as a biofeedback tool to control lumbopelvic motion. [Participants and Methods] Eighteen volunteers with chronic nonspecific low back pain (21.28 ± 1.41 years old) who performed an active straight leg raising (dynamic postural challenge) with and without pressure biofeedback. Changes in the pressure biofeedback unit and on centre of pressure displacement were assessed, as well as bilateral electromyographic abdominal muscle activity. Participants were not allowed to use a Valsalva manoeuvre. [Results] Pressure variation was not significantly correlated with abdominal muscle activity or with mediolateral centre of pressure displacement. When used as a biofeedback instrument, there was a significant increase in almost all abdominal muscles activity as well as a significant decrease in pressure variation and in mediolateral centre of pressure displacement while performing an active straight leg raising with a normal breathing pattern. [Conclusion] Despite not being an indicator of abdominal muscle activity or mediolateral load transfer in the supine position, the pressure biofeedback unit could have great relevance when used in the clinic for biofeedback purposes in individuals with low back pain.

Respiratory morbidity in children with cerebral palsy: an overview

Respiratory problems have a significant impact on morbidity and mortality in patients with cerebral palsy (CP). In particular, recurrent aspiration, impaired airway clearance, spinal and thoracic deformity, impaired lung function, poor nutritional status, and recurrent respiratory infections negatively affect respiratory status. Bronchopulmonary dysplasia may contribute to pulmonary problems, but asthma is not more common in CP than in the general population. We discuss treatment options for each of these factors. Multiple coexisting and interacting factors that influence the respiratory status of patients with CP should be recognized and effectively addressed to reduce respiratory morbidity and mortality. WHAT THIS PAPER ADDS: Respiratory problems are a significant cause of morbidity in patients with cerebral palsy (CP). Respiratory status in patients with CP is influenced by recurrent aspiration and impaired airway clearance. Spinal and thoracic deformity, impaired lung function, poor nutrition, and respiratory infections also negatively affect respiratory status. These factors should all be addressed to reduce respiratory problems in patients with CP.

Phrenic Nerve Simulation for Central Sleep Apnea is Effective and Safe in the Presence of Concomitant Cardiac Devices

Introduction Central sleep apnea (CSA) is common in patients with heart failure. Many of these patients also have cardiac implantable electronic devices (CIED). The remedē® System is an implantable neurostimulator for CSA which transvenously stimulates the phrenic nerve to contract the diaphragm, restoring a normal breathing pattern and improving sleep, oxygenation and quality of life. In the remedē System Pivotal Trial, 44% (64/151) of patients had a prior CIED at the time of phrenic nerve stimulation (PNS) implant. Interaction testing was conducted at implant and therapy initiation (1 month post implant). Hypothesis PNS for the treatment of CSA is effective and safe in patients with a prior CIED. Methods Implant metrics, sleep metrics and related serious adverse events (AE) were compared based on the presence or absence of a CIED in patients enrolled in the remedē System Pivotal Trial. Results Of 64 subjects with a CIED, 33 (52%) had an ICD, 20 (31%) CRT-D, 10 (16%) PM, and 1 (2%) CRT-P. Implant metrics: remedē System implant time (2.7 ± 0.8 hours with vs 2.7 ± 0.9 hours without), fluoroscopy time (42 ± 22 min with vs 44 ± 23 min without) and contrast used (57 ± 51 cc with vs. 59 ± 59 cc without) were similar with or without CIED. Successful placement of a left-sided lead for PNS was similar with and without CIED (60% (38/64) vs. 67% (58/87)) as were improvements in central apnea index (-25.7 ± 18.0 events/hour with vs -19.8 ± 17.9 events/hour without) and oxygen desaturation ≥4% index (-23.4 ± 15.7 events/hour with vs -20.9 ± 19.2 events/hour without). Related serious AE through 24 months were lower in the CIED group overall with 8 events reported in 6 (9%) patients compared to 13 events in 11 (13%) patients in the group without CIED. The only event more prevalent in the CIED group was concomitant device interaction, with 4 CIED oversensing events reported in 3 patients resulting in the delivery of ICD therapy in 2 patients (1 shock, 1 anti-tachycardia pacing). Device interactions could be resolved by re-programming the PNS System in all patients without need for surgical revision. Improved concomitant device interaction testing procedures are part of device training and product labeling. Conclusion Phrenic nerve stimulation can effectively and safely treat CSA in patient with a CIED. Rare device interactions could be handled by reprogramming.

Afferent neural feedback overrides the modulating effects of arousal, hypercapnia and hypoxaemia on neonatal cardiorespiratory control.

Evidence obtained at whole animal, organ-system, and cellular and molecular levels suggests that afferent volume feedback is critical for the establishment of adequate ventilation at birth. As a result of the irreversible nature of the vagal ablation studies performed to date, it was difficult to quantify the roles of afferent volume input, arousal and changes in blood gas tensions on neonatal respiratory control. During reversible perineural vagal block, profound apnoeas and hypoxaemia and hypercarbia were observed, necessitating the termination of perineural blockade. Respiratory depression and apnoeas were independent of sleep state. We demonstrate that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. A change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period. Afferent volume feedback plays a vital role in neonatal respiratory control. Mechanisms for the profound respiratory depression and life-threatening apnoeas observed in vagally denervated neonatal animals remain unclear. We investigated the roles of sleep states, hypoxic-hypercapnia and afferent volume feedback on respiratory depression using reversible perineural vagal block during the early postnatal period. Seven lambs were instrumented during the first 48h of life to record/analyse sleep states, diaphragmatic electromyograph, arterial blood gas tensions, systemic arterial blood pressure and rectal temperature. Perineural cuffs were placed around the vagi to attain reversible blockade. Postoperatively, during the awake state, both vagi were blocked using 2% xylocaine for up to 30min. Compared to baseline values, pHa , and decreased and increased during perineural blockade (P<0.05). Four of seven animals exhibited apnoeas of ≥20s requiring the immediate termination of perineural blockade. Breathing rates decreased from the baseline value of 53±12 to 24±20breathsmin-1 during blockade despite an increased (P<0.001). Following blockade, breathing patterns returned to baseline values despite marked hypocapnia ( 33±3torr; P=0.03). Respiratory depression and apnoeas were independent of sleep states. The present study provides the much needed physiological evidence indicating that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. Rather, a change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period.

Efferent projections of excitatory and inhibitory preBötzinger Complex neurons.

The preBötzinger Complex (preBötC), a compact medullary region essential for generating normal breathing rhythm and pattern, is the kernel of the breathing central pattern generator (CPG). Excitatory preBötC neurons in rats project to major breathing-related brainstem regions. Here, we provide a brainstem connectivity map in mice for both excitatory and inhibitory preBötC neurons. Using a genetic strategy to label preBötC neurons, we confirmed extensive projections of preBötC excitatory neurons within the brainstem breathing CPG including the contralateral preBötC, Bötzinger Complex (BötC), ventral respiratory group, nucleus of the solitary tract, parahypoglossal nucleus, parafacial region (RTN/pFRG or alternatively, pFL /pFV ), parabrachial and Kölliker-Füse nuclei, as well as major projections to the midbrain periaqueductal gray. Interestingly, preBötC inhibitory projections paralleled the excitatory projections. Moreover, we examined overlapping projections in the pons in detail and found that they targeted the same neurons. We further explored the direct anatomical link between the preBötC and suprapontine brain regions that may govern emotion and other complex behaviors that can affect or be affected by breathing. Forebrain efferent projections were sparse and restricted to specific nuclei within the thalamus and hypothalamus, with processes rarely observed in cortex, basal ganglia, or other limbic regions, e.g., amygdala or hippocampus. We conclude that the preBötC sends direct, presumably inspiratory-modulated, excitatory and inhibitory projections in parallel to distinct targets throughout the brain that generate and modulate breathing pattern and/or coordinate breathing with other behaviors, physiology, cognition, or emotional state.

Relationship between oro and nasopharynx permeability and the direction of facial growth.

Most scientific literature relates vertical growth to individuals with decreased upper airway permeability. However, we often find subjects with a long face and a normal breathing pattern, most likely caused by other aetiological factors. And, frequently, we also find decreased upper airway permeability with horizontal growth. The aim of the study was to compare the cephalometric measurements of the oro and nasopharynx permeability with the facial growth direction and to identify the most common facial growth direction in individuals with decreased upper airway permeability. Cephalometric analysis was carried out in 158 pre-adolescent patients at the Orthodontic appointment, using facial profile teleradiographs. Parameters used were Jabarak's ratio and measurement of oro-nasopharynx space. Data collected were submitted to statistical treatment. This study points to the presence of an intermediate growth in individuals with diminished oro and nasopharynx permeability, either simultaneous or separate. The number of individuals with diminished permeability and vertical growth is close to the number of individuals with horizontal growth. The individuals with diminished permeability of the upper airway present an intermediate growth direction, representing the most frequent type. In the less common growth directions, there is a slight tendency to horizontal facial growth verified in individuals with diminished nasopharynx permeability. Also, a light tendency to vertical facial growth is present when oropharynx permeability is reduced.

SU‐G‐BRA‐11: Tumor Tracking in An Iterative Volume of Interest Based 4D CBCT Reconstruction

Purpose:4D CBCT can allow evaluation of tumor motion immediately prior to radiation therapy, but suffers from heavy artifacts that limit its ability to track tumors. Various iterative and compressed sensing reconstructions have been proposed to reduce these artifacts, but are costly time‐wise and can degrade the image quality of bony anatomy for alignment with regularization. We have previously proposed an iterative volume of interest (I4D VOI) method which minimizes reconstruction time and maintains image quality of bony anatomy by focusing a 4D reconstruction within a VOI. The purpose of this study is to test the tumor tracking accuracy of this method compared to existing methods.Methods:Long scan (8–10 mins) CBCT data with corresponding RPM data was collected for 12 lung cancer patients. The full data set was sorted into 8 phases and reconstructed using FDK cone beam reconstruction to serve as a gold standard. The data was reduced in way that maintains a normal breathing pattern and used to reconstruct 4D images using FDK, low and high regularization TV minimization (λ=2,10), and the proposed I4D VOI method with PTVs used for the VOI. Tumor trajectories were found using rigid registration within the VOI for each reconstruction and compared to the gold standard.Results:The root mean square error (RMSE) values were 2.70mm for FDK, 2.50mm for low regularization TV, 1.48mm for high regularization TV, and 2.34mm for I4D VOI. Streak artifacts in I4D VOI were reduced compared to FDK and images were less blurred than TV reconstructed images.Conclusion:I4D VOI performed at least as well as existing methods in tumor tracking, with the exception of high regularization TV minimization. These results along with the reconstruction time and outside VOI image quality advantages suggest I4D VOI to be an improvement over existing methods.Funding support provided by CPRIT grant RP110562‐P2‐01

Clinical associations with immature breathing in preterm infants: part 2—periodic breathing

BackgroundPeriodic breathing (PB) is a normal immature breathing pattern in neonates that, if extreme, may be associated with pathologic conditions.MethodsWe used our automated PB detection system to analyze all bedside monitor chest impedance data on all infants <35 weeks’ gestation in the University of Virginia Neonatal Intensive Care Unit from 2009-2014 (n=1211). Percent time spent in PB was calculated hourly (>50 infant-years’ data). Extreme PB was identified as a 12h period with PB >6 standard deviations above the mean for gestational age (GA) and post-menstrual age (PMA) and >10% time in PB.ResultsPB increased with GA, with the highest amount in infants 30-33 weeks’ GA at about 2 weeks’ chronologic age. Extreme PB was identified in 76 infants and in 45% was temporally associated with clinical events including infection or necrotizing enterocolitis (NEC), immunizations, or caffeine discontinuation. In 8/28 cases of septicemia and 10/21 cases of NEC there was a >2-fold increase in %PB over baseline in the day prior to diagnosis.ConclusionInfants <35 weeks GA spend, on average, <6% of the time in PB. An acute increase in PB may reflect illness or physiological stressors or may occur without any apparent clinical event.

Novel Dynamic Hepatic Magnetic Resonance Imaging Strategy Using Advanced Parallel Acquisition, Rhythmic Breath-Hold Technique, and Gadoxetate Disodium Enhancement.

The aim of the study was to evaluate image quality of a dynamic hepatic magnetic resonance (MR) imaging strategy based on advanced parallel acquisition combined with rhythmic breath-hold and gadoxetate disodium enhancement. Twenty-seven patients (21 male/6 female; mean age, 57.3 years) were enrolled in this institutional review board-approved study and underwent MR imaging at 3 T. The sequence (T1 3-dimensional gradient-recalled echo; acceleration factor, 4; reconstruction mode; controlled aliasing in parallel imaging resulting in higher acceleration factors; acquisition time, 10.4 seconds) was repeated at 8 fixed time points within the 3 minutes after contrast agent injection. Image quality was evaluated on a 5-point scale (1, excellent; 5, nondiagnostic). Dynamic sequences were classified according to perfusion phases and contrast characteristics. Artifacts and position of the liver in the z axis were recorded and analyzed. Overall image quality was found to be 1.44 (95% confidence interval, 1.18-1.71). Contrast was scored as excellent in 25 of 27 patients for central vessels and 22 of 27 patients for peripheral vessels. Adequate-quality arterial-phase images were obtained in all 27 patients. Double arterial and single arterial phases were acquired in 13 of 27 and 14 of 27 patients (n = 6 arterial dominant, n = 8 early arterial phases), respectively. In 1 (3.7%) of 27 patients, severe respiratory artifacts were seen during an early arterial phase. Artifacts were observed in 21 of 27 patients and rated as mild in 19 of these. Compromised quality was related to receiver coils (17 of 29), parallel imaging (6 of 29), breathing (3 of 29), and other causes (3 of 29). The position of the liver throughout the dynamic phases was highly constant, with a greatest mean shift of +2.9 mm throughout the first dynamic acquisition. Advanced parallel acquisition with rhythmic breath-hold and gadoxetate injection allows arterial phase imaging without breathing artifacts; a decelerated yet normal breathing pattern results in very robust breath-hold depth.

Design, performance characteristics and application examples of a new 4D motion platform

In this publication, a three-dimensionally movable motion phantom is described and its performance characteristics are evaluated. The intended primary fields of application for the phantom are the quality assurance (QA) of respiratory motion management devices in radiation therapy (RT) like gating or tumour tracking systems, training for clinical use of these techniques, and related 4DRT research. Considering especially the QA aspect, the phantom was designed as a motion platform that can be equipped with an appropriate add-on like standard QA phantoms for dosimetric measurements. The platform is driven by three computer-controlled independent linear motors (motion range: 40×50×50mm in anterior-posterior/superior-inferior/lateral direction; max. velocity: 3.9 m/s; max. acceleration: 10 m/s2), which allow the simulation of normal breathing patterns as well as arbitrary trajectories and anomalous events like coughing or baseline drift. For normal breathing patterns (here: sinusoidal curves with an amplitude of 20mm and a period of 3s/6s), the accuracy of the simulated motion paths was measured to be within 0,521mm even for the ArcCHECK® (weight: 20kg) as a platform load – values that we consider to be sufficient for the intended fields of application. The respective use of the motion phantom is illustrated.

Palatal surface and volume in mouth-breathing subjects evaluated with three-dimensional analysis of digital dental casts-a controlled study.

To compare the anatomical characteristics of the maxillary arch, identified as palatal surface area and volume, between mouth-breathing and nose-breathing subjects using a three-dimensional (3D) analysis of digital dental casts. Twenty-one Caucasian subjects (14 females and 7 males) with a mean age of 8.5 years [standard deviation (SD) 1.6 years] were selected according to the following criteria: mouth-breathing pattern due to allergic rhinitis, early mixed dentition, skeletal Class I relationship, and pre-pubertal stage of cervical vertebral maturation. This study group (SG) was compared with a control group (CG) of 17 nose-breathing subjects (9 females and 8 males, mean age: 8.5 years; SD: 1.7 years). For each subject, initial dental casts were taken and the upper arch was scanned using a 3D laser scanner. On each digital model, 3D measurements were performed to analyse maxillary arch morphology. Between-group differences were tested with the independent sample Student's t-test (P < 0.05). In mouth-breathing subjects, changes in physiological function of the upper respiratory tract resulted in skeletal adaptations of the maxillary arch. In the SG, both palatal surface area and volume were significantly smaller when compared with values of the CG. In particular, the palatal surface area and palatal volume were, respectively, 13.5 and 27.1 per cent smaller in the SG when compared to the CG. Subjects with prolonged mouth breathing showed a significant reduction of the palatal surface area and volume leading to a different development of the palatal morphology when compared with subjects with normal breathing pattern.

Capnography monitoring in procedural sedation for bronchoscopy.

Capnography monitoring in procedural sedation for bronchoscopy.

A novel therapeutic approach for the treatment of central sleep apnea: The remedē® system.

Central sleep apnea (CSA) occurs primarily in cardiovascular patients and is associated with high morbidity and mortality. The disorder often is unrecognized due to the overlap of symptoms with those of the underlying cardiac disease. CSA can be easily diagnosed with a sleep study. Following optimization of all co-morbidities, the therapeutic approach available currently focuses on mask-based therapies which suffer from poor patient adherence. A new therapy, the remedē® System, has been developed; it utilizes a transvenous, fully implantable system providing phrenic nerve stimulation intended to restore a more normal breathing pattern. The therapy demonstrated promising results based on an initial chronic study and a randomized trial is underway to further evaluate safety and efficacy of this novel system in patients with CSA.

Unconstrained Video Monitoring of Breathing Behavior and Application to Diagnosis of Sleep Apnea

This paper presents a new real-time automated infrared video monitoring technique for detection of breathing anomalies, and its application in the diagnosis of obstructive sleep apnea. We introduce a novel motion model to detect subtle, cyclical breathing signals from video, a new 3-D unsupervised self-adaptive breathing template to learn individuals' normal breathing patterns online, and a robust action classification method to recognize abnormal breathing activities and limb movements. This technique avoids imposing positional constraints on the patient, allowing patients to sleep on their back or side, with or without facing the camera, fully or partially occluded by the bed clothes. Moreover, shallow and abdominal breathing patterns do not adversely affect the performance of the method, and it is insensitive to environmental settings such as infrared lighting levels and camera view angles. The experimental results show that the technique achieves high accuracy (94% for the clinical data) in recognizing apnea episodes and body movements and is robust to various occlusion levels, body poses, body movements (i.e., minor head movement, limb movement, body rotation, and slight torso movement), and breathing behavior (e.g., shallow versus heavy breathing, mouth breathing, chest breathing, and abdominal breathing).

Assessment of the Effects of Controlled Frequency Breathing on Lactate Levels in Swimming

Assessment of the Effects of Controlled Frequency Breathing on Lactate Levels in Swimming A randomly assigned maximal effort 100-yd swim test was conducted twice, once with normal breathing (NB) pattern (1 breath every 2-3 strokes), and the second using controlled frequency breathing (CFB) pattern (1 breath every 7 strokes) in 21 trained female swimmers (19.0 ± 1.1 years). Post-swim blood lactate levels, heart rate, and time to completion were measured and assessed after completion of each bout. Blood samples were taken from the earlobe at rest (prior to the bout), 0-min,1.5-min, 3-min, and 5-min post-swim. Heart rate was taken at rest and at the same time points as blood lactate.

Evaluation of maxillary arch dimensions and palatal morphology in mouth-breathing children by using digital dental casts

ObjectiveThe aim of the present study was to analyze the variations of maxillary arch size and of palatal morphology in subjects with prolonged mouth-breathing due to allergic rhinitis when compared with a control group with normal breathing pattern by using a three-dimensional analysis on digital casts. Methods26 Caucasian children (19 females and 7 males) with a mean age of 8.5 years (SD 1.6 years) were selected according to the following criteria: mouth-breathing pattern due to allergic rhinitis, early mixed dentition, skeletal Class I relationship and prepubertal stage of cervical vertebral maturation. The study group was compared with a control group of 17 nasal breathing subjects (9 females; 8 males, mean age 8.5 years SD 1.7 years). For each subject an initial dental cast was taken and the upper arch was scanned by using a tridimensional scanner. On each digital model linear measurements were performed to analyze maxillary arch dimensions and palatal morphology. Significant between-group differences were tested with the Student t-test (p<0.05). Resultsthe transverse dimension of the upper arch was significantly smaller in subjects of the study group thus confirming the influence of oral breathing on skeletal development with a significant constriction of the whole palate. The study group showed a higher and sharper palatal vault at the level of second deciduous molars and of first permanent molars. ConclusionsChildren with mouth-breathing pattern showed a significant constriction of the maxillary arch and an increased palatal height when compared with subjects with normal breathing pattern.

The Importance of a Normal Breathing Pattern for an Effective Abdominal-Hollowing Maneuver in Healthy People: An Experimental Study

A normal breathing pattern while performing the abdominal-hollowing (AH) maneuver or spinal-stabilization exercise is essential for the success of rehabilitation programs and exercises. In previous studies, subjects were given standardized instructions to control the influence of respiration during the AH maneuver. However, the effect of breathing pattern on abdominal-muscle thickness during the AH maneuver has not been investigated. To compare abdominal-muscle thickness in subjects performing the AH maneuver under normal and abnormal breathing-pattern conditions and to investigate the effect of breathing pattern on the preferential contraction ratio (PCR) of the transverse abdominis. Comparative, repeated-measures experimental study. University research laboratory. 16 healthy subjects (8 male, 8 female) from a university population. A real-time ultrasound scanner was used to measure abdominal-muscle thickness during normal and abnormal breathing patterns. A paired t test was used to assess the effect of breathing pattern on abdominal-muscle thickness and PCR. Muscle thickness in the transverse abdominis and internal oblique muscles was significantly greater under the normal breathing pattern than under the abnormal pattern (P < .05). The PCR of the transverse abdominis was significantly higher under the normal breathing pattern compared with the abnormal pattern (P < .05). The results indicate that a normal breathing pattern is essential for performance of an effective AH maneuver. Thus, clinicians should ensure that patients adopt a normal breathing pattern before performing the AH maneuver and monitor transverse abdominis activation during the maneuver.

Role of Inhibition in Respiratory Pattern Generation

Postsynaptic inhibition is a key element of neural circuits underlying behavior, with 20-50% of all mammalian (nongranule) neurons considered inhibitory. For rhythmic movements in mammals, e.g., walking, swimming, suckling, chewing, and breathing, inhibition is often hypothesized to play an essential rhythmogenic role. Here we study the role of fast synaptic inhibitory neurotransmission in the generation of breathing pattern by blocking GABA(A) and glycine receptors in the preBötzinger complex (preBötC), a site essential for generation of normal breathing pattern, and in the neighboring Bötzinger complex (BötC). The breathing rhythm continued following this blockade, but the lung inflation-induced Breuer-Hering inspiratory inhibitory reflex was suppressed. The antagonists were efficacious, as this blockade abolished the profound effects of the exogenously applied GABA(A) receptor agonist muscimol or glycine, either of which under control conditions stopped breathing in vagus-intact or vagotomized, anesthetized, spontaneously breathing adult rats. In vagotomized rats, GABA(A)ergic and glycinergic antagonists had little, if any, effect on rhythm. The effect in vagus-intact rats was to slow the rhythm to a pace equivalent to that seen after suppression of the aforementioned Breuer-Hering inflation reflex. We conclude that postsynaptic inhibition within the preBötC and BötC is not essential for generation of normal respiratory rhythm in intact mammals. We suggest the primary role of inhibition is in shaping the pattern of respiratory motor output, assuring its stability, and in mediating reflex or volitional apnea, but not in the generation of rhythm per se.

An Impulse Radio Ultrawideband System for Contactless Noninvasive Respiratory Monitoring

We design a impulse radio ultrawideband radar monitoring system to track the chest wall movement of a human subject during respiration. Multiple sensors are placed at different locations to ensure that the backscattered signal could be detected by at least one sensor no matter which direction the human subject faces. We design a hidden Markov model to infer the subject facing direction and his or her chest movement. We compare the performance of our proposed scheme on 15 human volunteers with the medical gold standard using respiratory inductive plethysmography (RIP) belts, and show that on average, our estimation is over 81% correlated with the measurements of a RIP belt system. Furthermore, in order to automatically differentiate between periods of normal and abnormal breathing patterns, we develop a change point detection algorithm based on perfect simulation techniques to detect changes in the subject's breathing. The feasibility of our proposed system is verified by both the simulation and experiment results.