Abdominal Respiratory Movements Research Articles

Current Research Status of Respiratory Motion for Thorax and Abdominal Treatment: A Systematic Review.

Malignant tumors have become one of the serious public health problems in human safety and health, among which the chest and abdomen diseases account for the largest proportion. Early diagnosis and treatment can effectively improve the survival rate of patients. However, respiratory motion in the chest and abdomen can lead to uncertainty in the shape, volume, and location of the tumor, making treatment of the chest and abdomen difficult. Therefore, compensation for respiratory motion is very important in clinical treatment. The purpose of this review was to discuss the research and development of respiratory movement monitoring and prediction in thoracic and abdominal surgery, as well as introduce the current research status. The integration of modern respiratory motion compensation technology with advanced sensor detection technology, medical-image-guided therapy, and artificial intelligence technology is discussed and analyzed. The future research direction of intraoperative thoracic and abdominal respiratory motion compensation should be non-invasive, non-contact, use a low dose, and involve intelligent development. The complexity of the surgical environment, the constraints on the accuracy of existing image guidance devices, and the latency of data transmission are all present technical challenges.

Towards Personalization of Planning Target Volume Margins Fitted to the Abdominal Adiposity in Localized Prostate Cancer Patients Receiving Definitive or Adjuvant/Salvage Radiotherapy: Suggestive Data from an ExacTrac vs. CBCT Comparison.

This study aimed to assess whether the patient's abdominal adiposity affects the performance of the Exactrac imaging system compared to the cone beam computed tomography (CBCT)-based setup, which was used as the reference positioning for the image-guided radiotherapy (IGRT) delivery to patients with localized prostate cancer. The daily positionings of patients with localized prostate cancer undergoing definitive or adjuvant/salvage radiotherapy (RT) were analyzed. The abdominal fat areas and pelvic incidence angle were determined on the CT simulation for each patient. A couple of ExacTrac images and a CBCT were acquired daily to verify the patient setup. We recorded every daily set of the three residual translational errors detected on the CBCT after the ExacTrac-based setup. These sets were clustered within three different thresholds (0.1 mm, 0.2 mm, and 0.3 mm), for each of which the influence of adipose tissues on Exactrac accuracy was assessed as the percentage of sub-threshold displacements as the fat parameters varied. A full bladder and empty rectum preparation protocol was adopted as much as possible. From the assessment of 1,770 daily positionings in 55 patients (38 definitive RT, 17 adjuvant/salvage RT), a good agreement between ExacTrac and CBCT could be inferred, which was quite robust against slight variations in the bladder and rectal filling, and the presence or not of the prostate. The percentages of above-threshold corrections increased with increasing abdominal fat, which therefore seemed to reduce the ExacTrac accuracy. This might be influenced by any intrafraction prostate displacement, likely induced by abdominal respiratory movements, and are more pronounced among overweight men. Our results promote the CBCT use over ExacTrac for IGRT of overweight patients with localized prostate cancer, while calling for attention to the probable need for personalization of planning target volume margins depending on the patient's body habitus.

A pilot study of respiratory motion characterization in the abdomen using a fast volumetric 4D‐MRI for MR‐guided radiotherapy

Purpose This pilot study explored the use of fast volumetric four-dimensional magnetic resonance imaging (4D-MRI) for motion characterization in the abdomen, ultimately aiming for the translation to future MR-guided radiotherapy (MRgRT) applications. Methods Nine healthy subjects and four patients underwent shallow free-breathing abdominal scans on a 1.5 T MR simulator using a fast volumetric 4D-MRI sequence with a temporal resolution up to three frames per second. The reference left/right liver and gross target volume (GTV) were segmented on the first frame, and the following consecutive dynamic images were nonlinearly registered to the reference to create the dynamic binary masks. Respiratory probabilistic volumes (rPPVj,i%), which correspond to the probability of being occupied by a volume of interest (VOI), were generated by summating the dynamic binary masks. Subject-specific rPPV144,0% and rPPV144,5% of the GTV were quantitatively compared to the 4D computed tomography (CT)-determined internal target volume (ITV) using the dice similarity coefficient (DSC), volumetric difference, and Hausdorff distance (HD). Results The results showed slightly smaller rPPV144,0% and rPPV144,5% but larger DSC and small HD compared to the 4D-CT-determined ITV, which preliminarily demonstrates the feasibility and capability of characterizing abdominal respiratory motion using the volumetric 4D-MRI-derived rPPV approach. Conclusion The potential usefulness of fast volumetric 4D-MRI for personalized motion management in future MRgRT is proposed.

Intrafraction pancreatic tumor motion patterns during ungated magnetic resonance guided radiotherapy with an abdominal corset.

BackgroundStereotactic body radiotherapy (SBRT) has been shown to be a promising therapy for unresectable pancreatic tumors. However, intrafraction motion, caused by respiratory motion and organ drift, is one of the main concerns for efficient dose delivery in ungated upper abdominal radiotherapy. The aim of this study was to analyze the intrafraction gross tumor volume (GTV) motion in a clinical cohort.Materials and methodsWe included 13 patients that underwent online adaptive magnetic resonance (MR)-guided SBRT for malignancies in the pancreatic region (5 × 8 Gy). An abdominal corset was fitted in order to reduce the abdominal respiratory motion. Coronal and sagittal cine magnetic resonance images of the tumor region were made at 2 Hz during the entire beam-on time of each fraction. We used deformable image registration to obtain GTV motion profiles in all three directions, which were subsequently high-pass and low-pass filtered to isolate the motion caused by respiratory motion and baseline drift, respectively.ResultsThe mean (SD) respiratory amplitudes were 4.2 (1.9) mm cranio-caudal (CC), 2.3 (1.1) mm ventral-dorsal (AP) and 1.4 (0.6) mm left–right (LR), with low variability within patients. The mean (SD) maximum baseline drifts were 1.2 (1.1) mm CC, 0.5 (0.4) mm AP and 0.5 (0.3) mm LR. The mean (SD) minimum baseline drifts were −0.7 (0.5) mm CC, −0.6 (0.5) mm AP and −0.5 (0.4) mm LR.ConclusionOverall tumor motion during treatment was small and interfractionally stable. These findings show that high-precision ungated MR-guided SBRT is feasible with an abdominal corset.

Noncontact In-Bed Measurements of Physiological and Behavioral Signals Using an Integrated Fabric-Sheet Sensing Scheme

Home monitoring requires measuring the physiological and behavioral signals without impairing a subject's everyday life. This paper presents an integrated and noncontact approach for obtaining simultaneous physiological and behavioral signals of recumbent humans in beds using a home-monitoring application. In the proposed approach, a fabric-sheet unified sensing electrode (FUSE) obtains physiological signals by recording the electrocardiogram (ECG), chest and abdominal respiratory movements (RMs), and ballistocardiogram (BCG). The FUSE also detects the behavioral signals of body proximity (BPx) and lateral/supine lying postures. A prototype system with FUSE was validated in a short-term experiment and 6-h overnight measurements on two different groups composed of seven lying subjects. The results confirmed that the approach senses each signal independently and records the ECG, RMs, BCG, and BPx signals simultaneously. The mean sensitivities of the R and T waves of the ECG during sleep were 86.1% and 88.0%, respectively, whereas those of the chest and abdominal RMs were 90.7% and 90.1%, respectively. Although our prototype system has room for improvement, the results suggest that our approach enables the unconstrained, nocturnal monitoring of the physiological and behavioral signals in recumbent humans. The at-home monitoring of the physiological and behavioral signals is expected to contribute to cost-effective personalized healthcare in the future. This noncontact and easy-to-install system for in-bed measurements can facilitate a new era of home monitoring.

WE‐G‐BRD‐01: A Data‐Driven 4D‐MRI Motion Model to Estimate Full Field‐Of‐View Abdominal Motion From 2D Image Navigators During MR‐Linac Treatment

Purpose:To estimate full field‐of‐view abdominal respiratory motion from fast 2D image navigators using a 4D‐MRI based motion model. This will allow for radiation dose accumulation mapping during MR‐Linac treatment.Methods:Experiments were conducted on a Philips Ingenia 1.5T MRI. First, a retrospectively ordered 4D‐MRI was constructed using 3D transient‐bSSFP with radial in‐plane sampling. Motion fields were calculated through 3D non‐rigid registration. From these motion fields a PCA‐based abdominal motion model was constructed and used to warp a 3D reference volume to fast 2D cine‐MR image navigators that can be used for real‐time tracking. To test this procedure, a time‐series consisting of two interleaved orthogonal slices (sagittal and coronal), positioned on the pancreas or kidneys, were acquired for 1m38s (dynamic scan‐time=0.196ms), during normal, shallow, or deep breathing. The coronal slices were used to update the optimal weights for the first two PCA components, in order to warp the 3D reference image and construct a dynamic 4D‐MRI time‐series. The interleaved sagittal slices served as an independent measure to test the model's accuracy and fit. Spatial maps of the root‐mean‐squared error (RMSE) and histograms of the motion differences within the pancreas and kidneys were used to evaluate the method.Results:Cranio‐caudal motion was accurately calculated within the pancreas using the model for normal and shallow breathing with an RMSE of 1.6mm and 1.5mm and a histogram median and standard deviation below 0.2 and 1.7mm, respectively. For deep‐breathing an underestimation of the inhale amplitude was observed (RMSE=4.1mm). Respiratory‐induced antero‐posterior and lateral motion were correctly mapped (RMSE=0.6/0.5mm). Kidney motion demonstrated good motion estimation with RMSE‐values of 0.95 and 2.4mm for the right and left kidney, respectively.Conclusion:We have demonstrated a method that can calculate dynamic 3D abdominal motion in a large volume, while acquiring real‐time cine‐MR images for MR‐guided radiotherapy.

Four-dimensional MRI using three-dimensional radial sampling with respiratory self-gating to characterize temporal phase-resolved respiratory motion in the abdomen.

To develop a four-dimensional MRI (4D-MRI) technique to characterize the average respiratory tumor motion for abdominal radiotherapy planning. A continuous spoiled gradient echo sequence was implemented with 3D radial trajectory and 1D self-gating for respiratory motion detection. Data were retrospectively sorted into different respiratory phases based on their temporal locations within a respiratory cycle, and each phase was reconstructed by means of a self-calibrating CG-SENSE program. Motion phantom, healthy volunteer and patient studies were performed to validate the respiratory motion detected by the proposed method against that from a 2D real-time protocol. The proposed method successfully visualized the respiratory motion in phantom and human subjects. The 4D-MRI and real-time 2D-MRI yielded comparable superior-inferior (SI) motion amplitudes (intraclass correlation = 0.935) with up-to one pixel mean absolute differences in SI displacements over 10 phases and high cross-correlation between phase-resolved displacements (phantom: 0.985; human: 0.937-0.985). Comparable anterior-posterior and left-right displacements of the tumor or gold fiducial between 4D and real-time 2D-MRI were also observed in the two patients, and the hysteresis effect was shown in their 3D trajectories. We demonstrated the feasibility of the proposed 4D-MRI technique to characterize abdominal respiratory motion, which may provide valuable information for radiotherapy planning.

A dual-Kinect approach to determine torso surface motion for respiratory motion correction in PET.

Respiratory gating is commonly used to reduce blurring effects and attenuation correction artifacts in positron emission tomography (PET). Established clinically available methods that employ body-attached hardware for acquiring respiration signals rely on the assumption that external surface motion and internal organ motion are well correlated. In this paper, the authors present a markerless method comprising two Microsoft Kinects for determining the motion on the whole torso surface and aim to demonstrate its validity and usefulness-including the potential to study the external/internal correlation and to provide useful information for more advanced correction approaches. The data of two Kinects are used to calculate 3D representations of a patient's torso surface with high spatial coverage. Motion signals can be obtained for any position by tracking the mean distance to a virtual camera with a view perpendicular to the surrounding surface. The authors have conducted validation experiments including volunteers and a moving high-precision platform to verify the method's suitability for providing meaningful data. In addition, the authors employed it during clinical (18)F-FDG-PET scans and exemplarily analyzed the acquired data of ten cancer patients. External signals of abdominal and thoracic regions as well as data-driven signals were used for gating and compared with respect to detected displacement of present lesions. Additionally, the authors quantified signal similarities and time shifts by analyzing cross-correlation sequences. The authors' results suggest a Kinect depth resolution of approximately 1 mm at 75 cm distance. Accordingly, valid signals could be obtained for surface movements with small amplitudes in the range of only few millimeters. In this small sample of ten patients, the abdominal signals were better suited for gating the PET data than the thoracic signals and the correlation of data-driven signals was found to be stronger with abdominal signals than with thoracic signals (average Pearson correlation coefficients of 0.74 ± 0.17 and 0.45 ± 0.23, respectively). In all cases, except one, the abdominal respiratory motion preceded the thoracic motion-a maximum delay of approximately 600 ms was detected. The method provides motion information with sufficiently high spatial and temporal resolution. Thus, it enables meaningful analysis in the form of comparisons between amplitudes and phase shifts of signals from different regions. In combination with a large field-of-view, as given by combining the data of two Kinect cameras, it yields surface representations that might be useful in the context of motion correction and motion modeling.

Kangaroo care: cardio-respiratory relationships between the infant and caregiver

BackgroundKangaroo care, i.e., skin-to-skin cohabitation (SSC) between an infant and caregiver, is often used in neonatal intensive care units to promote bonding, breastfeeding and infant growth. The direct salutary effects of SSC on cardio-respiratory control in preterm infants remain equivocal; some reports suggest improved breathing stability, others indicate worsening of apnea, bradycardia and hypoxemia. AimThe purpose of this study was to investigate physiological relationships between the infant and caregiver during SSC. We hypothesized that respiratory stability of the premature infant is influenced by the caregiver's heartbeat. DesignA prospective study was performed in eleven preterm infants (6 female; mean PCA 32 wks). SSC was compared to a preceding incubator-control period (CTL) matched for time from feed and condition duration. Abdominal respiratory movement, electrocardiogram, skin temperature and blood-oxygen levels were recorded from the infant and the caregiver. ResultsDuring CTL, infant interbreath interval variance (IBIv; respiratory instability) was directly related to its own heart rate variance (HRv; rho=0.770, p=0.009). During SSC, infant IBIv and apnea incidence were each related to caregiver HRv (rho 0.764, p=0.006; rho 0.677, p=0.022, respectively). Infant cardio-respiratory coupling was also enhanced during SSC compared to CTL in the eupneic frequency range (0.7–1.5Hz, p=0.018) and reduced for slower frequencies (0.15–0.45Hz; p=0.036). ConclusionThese findings suggest that during SSC, respiratory control of the premature infant is influenced by the caregiver's cardiac rhythm. We propose that the caregiver's heartbeat causes sensory perturbations of the infant via somatic or other afferents, revealing a novel cohabitation-induced feed-back mechanism of respiratory control in the neonate.

SU‐E‐J‐48: Development of An Abdominal Compression Device for Respiratory Correlated Radiation Therapy

Purpose:The aim of this study is to develop the abdominal compression device which could control pressure level according to the abdominal respiratory motion and evaluate its feasibility.Methods:In this study, we focused on developing the abdominal compression device which could control pressure level at any point of time so the developed device is possible to use a variety of purpose (gating technique or respiratory training system) while maintaining the merit of the existing commercial device. The compression device (air pad form) was designed to be able to compress the front and side of abdomen and the pressure level of the abdomen is controlled by air flow. Pressure level of abdomen (air flow) was determined using correlation data between external abdominal motion and respiratory volume signal measured by spirometer. In order to verify the feasibility of the device, it was necessary to confirm the correlation between the abdominal respiratory motion and respiratory volume signal and cooperation with respiratory training system also checked.Results:In the previous study, we could find that the correlation coefficient ratio between diaphragm and respiratory volume signal measured by spirometer was 0.95. In this study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion measured by belt‐transducer (correlation coefficient ratio was 0.92) and used the correlated respiratory volume data as an abdominal pressure level. It was possible to control the pressure level with negligible time delay and respiratory volume data based guiding waveforms could be properly inserted into the respiratory training system.Conclusion:Through this feasibility study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion. Also initial assessment of the device and its compatibility with the respiratory training system were verified. Further study on application in respiratory gated therapy and respiratory training system will be investigated.This work was supported by Radiation Technology R&D program (No. 2013M2A2A7043498)and Basic Atomic Energy Research Institute (BAERI)(No. NRF‐2009‐0078390) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.

Application of a spring-dashpot system to clinical lung tumor motion data

The treatment efficacy of radiation therapy for lung tumors can be increased by compensating for breath-induced tumor motion. In this study, we quantitatively examine a mathematical model of pseudomechanical linkages between an external surrogate signal and lung tumor motion. A spring-dashpot system based on the Voigt model was developed to model the correlation between abdominal respiratory motion and tumor motion during lung radiotherapy. The model was applied to clinical data obtained from 52 treatments ("beams") from 10 patients, treated on the Mitsubishi Real-Time Radiation Therapy system, Sapporo, Japan. In Stage 1, model parameters were optimized for individual patients and beams to determine reference values and to investigate how well the model can describe the data. In Stage 2, for each patient the optimal parameters determined for a single beam were applied to data from other beams to investigate whether a beam-specific set of model parameters is sufficient to model tumor motion over a course of treatment. In Stage 1, the baseline root mean square (RMS) residual error for all individually optimized beam data was 0.90 ± 0.40 mm (mean ± 1 standard deviation). In Stage 2, patient-specific model parameters based on a single beam were found to model the tumor position closely, even for irregular beam data, with a mean increase with respect to Stage 1 values in RMS error of 0.37 mm. On average, the obtained model output for the tumor position was 95% of the time within an absolute bound of 2.0 and 2.6 mm in Stages 1 and 2, respectively. The model was capable of dealing with baseline, amplitude and frequency variations of the input data, as well as phase shifts between the input abdominal and output tumor signals. These results indicate that it may be feasible to collect patient-specific model parameters during or prior to the first treatment, and then retain these for the rest of the treatment period. The model has potential for clinical application during radiotherapy treatment of lung tumors.

Automated detecting and classifying of sleep apnea syndrome based on genetic-SVM

Sleep apnea SA is one of the common sleep disorders. It has several consequences that can affect daily life activities. The common diagnose procedure is carried out through an overnight sleep test. The test usually includes of several bio-signals recordings that are used to detect this syndrome. The conventional approach of detecting the sleep apnea uses a manual analysis of most bio-signals to achieve reasonable accuracy. The manual process of this test, is highly cost and time consuming. This paper presents a novel automatic system for detecting and classifying apnea events by using just a few of bio-signals that are related to breathe defect. This method uses only the air flow, thoracic and abdominal respiratory movement as inputs for the system. The proposed technique consists of four main parts which are; signal segmentation, feature generation, feature selection and data reduction based on genetic SVM, and classification. Statistical analyzes on the attained results show efficiency of this system and its superiority versus previous methods even with more bio-signals as input.

Genetic Fuzzy Approach based Sleep Apnea/Hypopnea Detection

Sleep Apnea (SA) is one of the most common and important part of sleep disorders. Unfortunately, sleep apnea may be going undiagnosed for years, because of the person's unawareness. The common diagnose procedure usually required an overnight sleep test. During the test, a recording of many biosignals, which related to breath, are obtained by polysomnography machine to detect this syndrome. The manual process for detecting the sleep Apnea by analysis the recording data is highly cost and time consuming. So, several works tried to develop systems that achieve this automatically. This paper proposes a genetic fuzzy approach for detecting Apnea/Hypopnea events by using Air flow, thoracic and abdominal respiratory movement signals and Oxygen desaturation as the inputs. Results show efficiently of this approach.

Agonal Sequences in 14 Filmed Hangings With Comments on the Role of the Type of Suspension, Ischemic Habituation, and Ethanol Intoxication on the Timing of Agonal Responses

The Working Group on Human Asphyxia has analyzed 14 filmed hangings: 9 autoerotic accidents, 4 suicides, and 1 homicide. The following sequence of agonal responses was observed: rapid loss of consciousness in 10 ± 3 seconds, mild generalized convulsions in 14 ± 3 seconds, decerebrate rigidity in 19 ± 5 seconds, beginning of deep rhythmic abdominal respiratory movements in 19 ± 5 seconds, decorticate rigidity in 38 ± 15 seconds, loss of muscle tone in 1 minute 17 seconds ± 25 seconds, end of deep abdominal respiratory movements in 1 minute 51 seconds ± 30 seconds, and last muscle movement in 4 minutes 12 seconds ± 2 minutes 29 seconds. The type of suspension and ethanol intoxication does not seem to influence the timing of the agonal responses, whereas ischemic habituation in autoerotic practitioner might decelerate the late responses to hanging.

Electroencephalographic Abnormalities in Patients with Idiopathic Insomnia

Objective: The main goal of the present research is to describe the electroencephalographic activity during sleep and the cyclic alternating pattern (CAP) on idiopathic insomniac patients. Methods: 22 idiopathic insomnia patients were included. Sleep recording included: fully conventional EEG recording (32 electrodes, with 16 channels getting ipsilateral bipolar recordings), EOG, EMG, EKG, thoracic and abdominal respiratory movements, nasal flow and oximetry. Results: Out of the 22 registered patients, 10 (45%) showed no electroencephalographic alteration, while 12 (55%) exhibited an electroencephalographic alteration (irritative activity). Concerning PSG variables, significant differences between groups (no EEG alteration and EEG alterations) were detected in: sleep latency, total sleep time, total wake time, sleep efficiency, light sleep percentage, slow waves sleep percentage and on the sub type A1 index of the cyclic alternant pattern CAP. Conclusions: The present data strongly suggest that within the population diagnosed with idiopathic insomnia, there is a subgroup in which the electroencephalographic alterations may play a critical role as the source of the sleep abnormality.

The “Air-bag System”: A Novel Respiratory Monitoring Device Collaborated with RPM System

Respiratory motion is an issue that is becoming increasingly important in the era of image-guided radiotherapy. The Real-Time Position Management System (RPM, Varian Medical System, Palo Alto, CA) is commercially available gating equipment which is popular around the world. This system uses a plastic box with a reflective marker which is placed on the patient's abdomen to detect the vertical motion by an infrared camera. However, this method with such a single point detector has several limitations to obtain the accurate respiratory motion. We developed the novel substitution device for this plastic box of the RPM system to monitor the patient's body volume change as an external respiration signal. The “Air-bag System”, a novel respiratory monitoring device, consists of a non-elastic air bag connected with an elastic air bag. A non-elastic air bag is placed between the patient's body and the stereotactic fixation frame. A current meter located between two bags measures the air flows back and forth between two bags. The data are processed by personal computer and translated the respiratory motion into swinging decoy markers displayed on the computer screen so that an infrared camera of RPM system can capture the swinging marker instead of an infrared reflective marker. 4D-CT data of 15 lung cancer patients were acquired by the RPM system with the “Air-bag System”. On each phase of the 4D data, correlations between the lung volume and the body volume were evaluated. 4D-CT data of another 3 lung cancer patients were acquired by the RPM system recording with two different respiratory motions. One is an abdominal respiratory motion using an infrared reflective marker placed on the patient's abdomen, the other one is a thorax respiratory volume shift using the air bag set on the patient's chest. The respiratory phases (8 phases) at each instant in time based on modeling two different motion amplitudes were compared. There was a strong correlation (r2 = 0.976) between the lung volume and the body volume on each respiratory phase. Comparing the reconstructed 4D-CT images on each respiratory phase recorded by using an infrared reflective marker to those recorded by using the “Air-bag System” resulted in no difference on all respiratory phases. The novel respiratory gating device which monitors the patient's body volume as an external respiration signal was developed. Recording with this “Air-bag System”, applicability of RPM system is not limited owing to enough amplitude and more accurate determination of the magnitude of respiratory motion. Moreover, abdominal compression with the air bag reduces the movement of diaphragm which can decrease the intra-thoracic organ motion without loading additional stress on the patient.

Agonal Sequences in Eight Filmed Hangings: Analysis of Respiratory and Movement Responses to Asphyxia by Hanging*

It has been proposed that filmed hangings may hold the key to a better understanding of human asphyxia, and The Working Group on Human Asphyxia was formed to systematically review and compare these video recordings. This study analyzed eight filmed hangings. Considering time 0 to represent the onset of the final hanging, rapid loss of consciousness was observed (at 8-18 sec), closely followed by convulsions (at 10-19 sec). A complex pattern of decerebrate rigidity and decorticate rigidity then followed. Between 1 min 38 sec and 2 min 15 sec, muscle tone seemed to be lost, the body becoming progressively flaccid. From then on, isolated body movements were observed from time to time, the last one occurring between 1 min 2 sec and 7 min 31 sec. As for the respiratory responses, all cases presented deep rhythmic abdominal respiratory movements (last one between 1 min 2 sec and 2 min 5 sec).

Pressure‐rate product and phase angle as measures of acute inspiratory upper airway obstruction in rhesus monkeys

There are limited validated, objective, and minimally invasive techniques for the bedside evaluation of upper airway obstruction (UAO) in sick infants, despite its frequency in pediatric medicine. Prior techniques include pressure-rate product (PRP), a product of esophageal pressure and respiratory rate and phase angles (PAs), a measure of asynchrony between ribcage and abdominal respiratory movements in infants with UAO. The purpose of this study is to validate the PRP and compare it to a previously validated PA in rhesus monkeys. Calibrated resistors were applied to the inspiratory limb of 10 anesthetized, intubated, and spontaneously breathing rhesus monkeys (weight 8.7 +/- 2.5 kg). Airway pressure, respiratory rate, PAs, heart rate, and oxygen saturation were recorded. Obstruction was applied in random order as 0, 5, 20, 200, 500, and 1,000 cmH(2)O/L/sec for 2-min periods, the last 15 sec (10-20 breaths) were analyzed for each timeframe. PA increased significantly at the 200 cmH(2)O/L/sec level but it reached a plateau above 500 cmH(2)O/L/sec. PRP rose progressively and was significantly different at all levels of obstruction. Esophageal pressure change was progressively and statistically significantly different from baseline and each other at 200, 500, and 1,000 cmH(2)O/L/sec (P < 0.001). In this model of UAO, PRP tracks increasing inspiratory load better than PA. PRP continued to be linear up through the highest inspiratory resistance where the change in PA reached a plateau before the highest load. The assessment of esophageal pressure changes may offer the simplest objective measure of UAO.

A simple method for labeling CT images with respiratory states

A method is described for labeling CT images with their respiratory state by a needle, connected to the patient's chest/abdomen. By means of a leverage the needle follows the abdominal respiratory motion. The needle is visible as a blurred spot in every CT slice. The method was tested with nine patients. A series of volume scans during free breathing was performed. The detected positions of the moving needle in every single slice were compared to each other thus enabling respiratory state assignment. The tool is an inexpensive alternative to complex respiratory measuring tools for four dimensional (4D) CT and was greatly accepted in the clinic due to its simplicity.

Ondine's Curse in a Patient with Unilateral Medullary and Bilateral Cerebellar Infarctions

Central sleep apnea (CSA), also known as Ondine's curse (OC), is a phenomenon characterized by episodes of repeated apnea during sleep due to disorders of the central nervous system. We report a patient with CSA/OC due to right dorsolateral medullary and bilateral cerebellar infarctions that occurred in the clinical setting of right vertebral artery stenosis. Polysomnography (PSG) showed repeated episodes of absence of nasal cannula flow accompanying cessation of thoracic and abdominal respiratory movements and a decline in blood oxygen saturation. The duration of apnea was as long as 12 seconds. Brain magnetic resonance (MR) images showed acute infarctions involving the right dorsolateral medulla, bilateral cerebellar vermis and paramedian cerebellar hemispheres. MR angiography showed nonvisualization of the right vertebral artery. Transcranial Doppler sonography showed a high resistance flow profile in the right vertebral artery and normal flow patterns in the basilar artery and left vertebral artery. These findings suggest that the medullary and bilateral cerebellar infarcts were caused by stenosis/pseudo-occlusion of the right vertebral artery. Reduced respiratory afferent inputs to the dorsal respiratory group of medullary neurons, the nucleus tractus solitarius and reduced "automatic" components of the respiratory drive may play a role in the development of CSA/OC.