Respiratory Belt Research Articles

Wearable Bluetooth Triage Healthcare Monitoring System.

Triage is the first interaction between a patient and a nurse/paramedic. This assessment, usually performed at Emergency departments, is a highly dynamic process and there are international grading systems that according to the patient condition initiate the patient journey. Triage requires an initial rapid assessment followed by routine checks of the patients’ vitals, including respiratory rate, temperature, and pulse rate. Ideally, these checks should be performed continuously and remotely to reduce the workload on triage nurses; optimizing tools and monitoring systems can be introduced and include a wearable patient monitoring system that is not at the expense of the patient’s comfort and can be remotely monitored through wireless connectivity. In this study, we assessed the suitability of a small ceramic piezoelectric disk submerged in a skin-safe silicone dome that enhances contact with skin, to detect wirelessly both respiration and cardiac events at several positions on the human body. For the purposes of this evaluation, we fitted the sensor with a respiratory belt as well as a single lead ECG, all acquired simultaneously. To complete Triage parameter collection, we also included a medical-grade contact thermometer. Performances of cardiac and respiratory events detection were assessed. The instantaneous heart and respiratory rates provided by the proposed sensor, the ECG and the respiratory belt were compared via statistical analyses. In all considered sensor positions, very high performances were achieved for the detection of both cardiac and respiratory events, except for the wrist, which provided lower performances for respiratory rates. These promising yet preliminary results suggest the proposed wireless sensor could be used as a wearable, hands-free monitoring device for triage assessment within emergency departments. Further tests are foreseen to assess sensor performances in real operating environments.

Noninvasive Method and Metric for Monitoring Lung Condition.

For hospitalized patients with pulmonary conditions, the onset of respiratory decline can occur unnoticed, due to the absence of a way to continuously and noninvasively monitor lung condition. Based on the relationship between lung volume and pleural pressure, we hypothesized that the time delay (∆t) between the start of a respiratory cycle and the occurrence of lung sounds associated with inspiration would correlate with lung volume. Additionally, we developed a re-search tool, consisting of a respiration belt, digital stethoscope, data collection system and MATLAB algorithm, to measure this delay. We conducted a feasibility study with three healthy individuals that involved safely manipulating lung volume, through subject position and activity, and plotting ∆t against volume measurements obtained via spirometry. The results indicated that ∆t was measurable and changed with lung volume and, therefore, has the potential to serve as a lung condition monitoring tool.

Early objective adherence to hypoglossal nerve stimulation therapy.

To assess early adherence to therapy with hypoglossal nerve stimulation therapy. This is a prospective study of consecutive patients with moderate to severe obstructive sleep apnea who underwent implantation of hypoglossal nerve stimulation therapy within a single academic practice and attended a follow-up appointment after greater than 30 days of therapy use. Objective adherence data were extracted from an objective monitoring database and compared to patient characteristics. The study population was 79 participants who were 29.1% female with a mean age of 58.7 ± 12.8 years old, body mass index of 28.9 ± 3.4 kg/m2, and baseline apnea-hypopnea index of 33.8 ± 17.6 events/h. In the first 7 days after device activation, average use was 7.8 h/night, with 91.9% of nights with greater than 4 hours of therapy use and an average of 0.2 pauses in therapy per night. These figures remained stable after 30 days of use: 7.7 h/night, 91.0% of nights longer than 4 hours, and 0.3 pauses per night. Objective evidence of difficulty with acclimatization was associated with age less than 60 years (odds ratio 2.8, 95% confidence interval 1.1-7.1, P = .03) and a history of prior upper airway surgery (3.9, 1.2-11.9, P = .015). Insomnia was present in 31 patients and was not associated with objective evidence of difficulty tolerating therapy. Early adherence to hypoglossal nerve stimulation is excellent (92.4% >4 hours on >70% of nights), suggesting that the acclimatization period is straightforward in most. Younger age and a history of prior upper airway surgery appear to be associated with an increased risk of difficulty with acclimatization. Huyett P. Early objective adherence to hypoglossal nerve stimulation therapy. J Clin Sleep Med. 2022;18(2):631-636.

Transcutaneous Cervical Vagus Nerve Stimulation Lengthens Exhalation in the Context of Traumatic Stress.

Transcutaneous electrical stimulation of the vagus nerve is believed to deliver afferent signaling to the brain that, in turn, yields downstream changes in peripheral physiology, including cardiovascular and respiratory parameters. While the effects of transcutaneous cervical vagus nerve stimulation (tcVNS) on these parameters have been studied broadly, little is known regarding the specific effects of tcVNS on exhalation time and the spontaneous respiration cycle. By understanding such effects, tcVNS could be used to counterbalance sympathetic hyperactivity following distress by enhancing vagal tone through parasympathetically favored modulation of inspiration and expiration - specifically, lengthened expiration relative to inspiration. We thus investigated the effects of tcVNS on respiration timings by decomposing the respiration cycle into inspiration and expiration times and incorporating state-of-the-art respiration quality assessment algorithms for respiratory effort belt and electrocardiogram derived respiration signals. This enabled robust estimation of respiration timings from quality measurements alone. We thereby found that tcVNS increases expiration time minutes after stimulation, compared to a sham control (N = 26). This suggests that tcVNS could counteract sympathovagal imbalance, given the relationship between expiration and heightened vagal tone.

Non-contact breathing monitoring by integrating RGB and thermal imaging via RGB-thermal image registration

Altered breathing rate is an important sign of disease status. Currently used machine-based monitoring of the breathing rate includes contact with the body, which may result in pain and discomfort. In this paper, a non-contact breathing monitoring technique is proposed by integrating RGB and thermal imaging systems with RGB-thermal image registration. This method provides a linear mapping for automated selection of the region of interest (ROI) followed by tracking to extract the breathing rate. To evaluate the efficacy of the proposed approach and its robustness against motion, talking, varying breathing rate or rhythm, and high ambient temperature, this study was conducted in three phases. Validation of the proposed approach demonstrated a strong agreement with the reference method of breathing rate monitoring using a respiration belt. During normal breathing, the mean absolute error (MAE) reached 0.11 bpm (breaths per minute). While in more challenging conditions, defined by three phases, the MAE reached 1.46, 2.08, and 1.69 bpm, respectively. In short, the proposed method performance is a promising alternative to a contact-based method due to its strong agreement and might be useful in diverse applications such as sport studies, rehabilitation centres, quarantine centres, and in hospital or airport screening during the COVID 19 pandemic.

Free-Breathing Abdominal Magnetic Resonance Fingerprinting Using a Pilot Tone Navigator.

Quantitative T1 and T2 mapping in the abdomen provides valuable information in tissue characterization but is technically challenging due to respiratory motions. The proposed technique integrates magnetic resonance fingerprinting (MRF) and pilot tone (PT) navigator with retrospective gating to provide simultaneous quantification of multiple tissue properties in a single acquisition without breath-holding or patient set-up. To develop a free-breathing abdominal MRF technique for quantitative mapping in the abdomen. Prospective. Twelve healthy volunteers. A 3 T, two-dimensional (2D) and three-dimensional (3D) spiral MRF sequence with fast imaging with steady-state free precession (FISP) readout. The PT navigator was compared to standard respiratory belt performance. The T1 and T2 values acquired using 2D and 3D MRF with and without PT were obtained in a phantom and compared to reference values. Digital phantom simulation was performed to evaluate PT MRF reconstruction with varying breathing patterns. In the in vivo studies, T1 and T2 values derived from PT 2D MRF were compared to 2D breath-hold MRF. T1 and T2 values derived from PT 3D MRF were compared to published values. Principal component analysis (PCA), linear regression, relative error, Pearson correlation, paired Student's t-test, Bland-Altman Analysis. The phantom study showed PT MRF T1 values had a mean difference of 0.2% ± 0.1%, and T2 values had a mean difference of 0.1% ± 0.4% when compared to no-PT MRF values. The digital phantom experiment suggested the T1 and T2 maps at both end-exhalation and end-inhalation states resemble the corresponding ground-truth maps. The phantom study showed good agreement between MRF T1 and T2 values and with reference values. In vivo studies demonstrated that 2D and 3D quantitative imaging in the abdomen could be achieved with integration of PT navigation with MRF reconstruction using retrospective gating of respiratory motion. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 1.

Estimating Energy Expenditure Using Wearable Sensors During Locomotion

Introduction. Measures of metabolic energy expenditure can provide valuable insight into healthy and impaired gait, the design and control of assistive devices, and rehabilitation progress. The gold standard for estimating energy expenditure during locomotion is indirect calorimetry, where oxygen use is captured at the mouth. Although accurate, indirect calorimetry systems are expensive, cumbersome, and often limited to lab settings.
 Objective. The aim of our research is to develop a lightweight, portable, and low-cost method for accurately estimating energy expenditure using wearable sensors. Our method must meet the following design criteria: i. estimate walking and running energy expenditure within 5% error of gold standard measures, ii. maintain accuracy given changes to terrain and external loads, iii. provide a continuous estimate with estimate intervals a maximum of one minute apart, and iv. cost under $1000.
 Methods. In pilot testing, we instrumented two participants (male, 21-22 years, 84-90 kg, 1.88-1.90m) with indirect calorimetry to measure gold standard energy expenditure, as well as the following wearable sensors: an accelerometer at the pelvis and foot, a heart rate monitor, and a respiratory belt. The participants walked and ran on a predefined outdoor route on Queen’s campus, including sections with distinct average inclines (0% and 5%). Participants also wore ankle weights (3% body weight) for particular sections of the route. We will use a multiple regression analysis, with cross-validation design, to predict energy expenditure using custom metrics derived from the wearable sensors.

Integrating Breathing Techniques Into Psychotherapy to Improve HRV: Which Approach Is Best?

IntroductionApproaches to improve heart rate variability and reduce stress such as breathing retraining are more frequently being integrated into psychotherapy but little research on their effectiveness has been done to date. Specifically, no studies to date have directly compared using a breathing pacer at 6 breaths per minute with compassion focused soothing rhythm breathing.Current StudyIn this randomized controlled experiment, 6 breaths per minute breathing using a pacer was compared with compassion focused soothing rhythm breathing, with a nature video being used as a control group condition.MethodsHeart rate variability (HRV) measures were assessed via electrocardiogram (ECG) and respiration belt, and an automated blood pressure machine was used to measure systolic diastolic blood pressure, and heart rate (HR). A total of 96 participants were randomized into the three conditions. Following a 5-min baseline, participants engaged in either 6 breath per minute breathing, soothing rhythm breathing, or watched a nature video for 10 min. To induce a stressful state, participants then wrote for 5 min about a time they felt intensely self-critical. Participants then wrote for 5 min about a time they felt self-compassionate, and the experiment ended with a 10-min recovery period.ResultsConditions did not significantly differ at baseline. Overall, HRV, as measured by standard deviation of NN intervals (SDNN), low frequency HRV (LF HRV), and LF/HF ratio, increased during the intervention period, decreased during self-critical writing, and then returned to baseline levels during the recovery period. High frequency HRV (HF HRV) was not impacted by any of the interventions. The participants in the 6 breath per minute pacer condition were unable to consistently breathe at that rate and averaged about 12 breaths per minute. Time by Condition analyses revealed that both the 6 breaths per minute pacer and soothing breathing rhythm conditions lead to significantly higher SDNN than the nature video condition during breathing practice but there were no significant differences between conditions in response to the self-critical and self-compassionate writing or recovery periods. The 6 breath per minute pacer condition demonstrated a higher LF HRV and LF/HF ratio than the soothing rhythm breathing condition, and both intervention conditions had a higher LF HRV and LF/HF ratio than the nature video.ConclusionsAlthough the 6 breath per minute pacer condition participants were not able to breath consistently at the low pace, both the participants attempting to breathe at 6 breaths per minute as well as those in the soothing rhythm breathing condition effectively increased HR variability as measured by SDNN, and attempting to breathe at 6 breaths per minute led to the highest LF HRV and LF/HF ratio. Both breathing approaches impacted HRV more than watching a relaxing nature video and can potentially be used as key adjuncts in psychotherapy to aid in regulating physiological functioning, although it appears that consistent breathing practice would be needed.

Fabrication and Validation of Respiratory Control Belt Using Load Cell Sensor

Purpose: In this work, we have focused on fabrication and validation of a respiratory belt that produces respiratory signals from the patient’s abdominal and thorax. Materials and Methods: A load cell transducer was attached to the belt to create an electrical signal from respiratory movement. It converts a force or load into an equivalent electrical signal or digitized load value. The accuracy of the signals from our respiratory control belt was evaluated according to a comparison with the signals from commercial SOMNO medical device. Results: The pattern of the signals from our respiratory belt is in good agreement (4%/3mm) with the pattern of commercial SOMNO medical device. Conclusion: The manufactured respiratory control belt can be used during imaging and radiotherapy procedures for breath control in a patient's abdominal and thorax region.

Acute physiologic effects of N95 respirator use on gastroenterologists performing simulated colonoscopy

During the severe acute respiratory syndrome coronavirus 2 pandemic, N95 filtering facepiece respirator (FFR) use was required while performing aerosol-generating procedures. We studied the physiologic effects of N95 FFR use in a cohort of gastroenterologists performing simulated colonoscopies. Data collection and comparisons included (1) symptoms and change in vital signs in 12 gastroenterologists performing simulated colonoscopy for 60 minutes while wearing a surgical mask (SM) and faceshield (FS); N95 FFR, SM, and FS; and powered air-purifying respirator (PAPR) and (2) respiratory belt plethysmography and continuous electrocardiographic frequency-based heart rate (HR) variability indices including very low frequency power (measures intracardiac sympathetic tone) and low frequency to high frequency ratios (intracardiac sympathetic to vagal ratio) in 11 gastroenterologists performing simulated colonoscopy while wearing an SM (15 minutes), N95 FFR and SM (60 minutes), and SM (15 minutes) in rapid sequence. Ten of 12 gastroenterologists (83%) reported symptoms with N95 FFR use, most commonly breathing difficulty, frustration, fatigue, and headache. Nine of these gastroenterologists (75%) had associated significant HR elevation. Respiratory peak to trough measurement showed a significant increase (F(2)= 7.543, P= .004) during the N95 FFR stage, which resolved after removal of the N95 FFR. Although not statistically different, all gastroenterologists showed a decrease in sympathetic to vagal ratios and an increase in intracardiac sympathetic effects in the N95 FFR stage. PAPR use was better tolerated but was associated with headache and elevated HR in 4 gastroenterologists (33%). N95 FFR use by gastroenterologists is associated with development of acute physiologic changes and symptoms.

Stereotactic EEG Practices: A Survey of United States Tertiary Referral Epilepsy Centers.

Stereotactic EEG (SEEG) is being increasingly used in the intracranial evaluation of refractory epilepsy in the United States. In this study, the authors describe current practice of SEEG among National Association of Epilepsy Centers tertiary referral (level IV) centers. Using the Survey Monkey platform, a survey was sent to all National Association of Epilepsy Centers level IV center directors. Of 192 centers polled, 104 directors completed the survey (54% response rate). Ninety-two percent currently perform SEEG. Of these, 55% of institutions reported that greater than 75% of their invasive electrode cases used SEEG. Stereotactic EEG was commonly used over subdural electrodes in cases of suspected mesial temporal lobe epilepsy (87%), nonlesional frontal lobe epilepsy (79%), insular epilepsy (100%), and individuals with prior epilepsy surgery (74%). Most centers (72%) used single-lead electrocardiogram monitoring concurrently with SEEG, but less than half used continuous pulse oximetry (47%) and only a few used respiratory belts (3%). Other significant intercenter technical variabilities included electrode nomenclature and choice of reference electrode. Patient care protocols varied among centers in patient-to-nurse ratio and allowed patient activity. Half of all centers had personnel who had prior experience in SEEG (50.5%); 20% of centers had adopted SEEG without any formal training. Stereotactic EEG has become the principal method for intracranial EEG monitoring in the majority of epilepsy surgery centers in the United States. Most report similar indications for use of SEEG, though significant variability exists in the utilization of concurrent cardiopulmonary monitoring as well as several technical and patient care practices. There is significant variability in level of background training in SEEG among practitioners. The study highlights the need for consensus statements and guidelines to benchmark SEEG practice and develop uniform standards in the United States.

Non-Contact Respiration Monitoring and Body Movements Detection for Sleep Using Thermal Imaging.

Monitoring of respiration and body movements during sleep is a part of screening sleep disorders related to health status. Nowadays, thermal-based methods are presented to monitor the sleeping person without any sensors attached to the body to protect privacy. A non-contact respiration monitoring based on thermal videos requires visible facial landmarks like nostril and mouth. The limitation of these techniques is the failure of face detection while sleeping with a fixed camera position. This study presents the non-contact respiration monitoring approach that does not require facial landmark visibility under the natural sleep environment, which implies an uncontrolled sleep posture, darkness, and subjects covered with a blanket. The automatic region of interest (ROI) extraction by temperature detection and breathing motion detection is based on image processing integrated to obtain the respiration signals. A signal processing technique was used to estimate respiration and body movements information from a sequence of thermal video. The proposed approach has been tested on 16 volunteers, for which video recordings were carried out by themselves. The participants were also asked to wear the Go Direct respiratory belt for capturing reference data. The result revealed that our proposed measuring respiratory rate obtains root mean square error (RMSE) of bpm. The advantage of this approach lies in its simplicity and accessibility to serve users who require monitoring the respiration during sleep without direct contact by themselves.

Kalman Filtering for Posture-Adaptive in-Bed Breathing Rate Monitoring Using Bed-Sheet Pressure Sensors

Breathing rate (BR) is one of the vital signs used in physiological monitoring. Conventional BR monitoring requires attaching wired canula/thermistor on the buco-nasal area to measure air-flow, inducing discomfort to the subject. Abdominal/thoracic belts are also used to detect breathing movements whereas esophageal pressure is the gold standard to measure breathing effort. In this paper, we aim to validate the consistency of using only bed-sheet pressure sensors to monitor the BR in healthy adults. We propose a method and demonstrate that it could be used interchangeably with respiratory belts which were approved for medical use by the American Association of Sleep Medicine (AASM). We build a ten-sinusoidal model-based extended Kalman Filter to adaptively estimate the breathing movements' signal from the body pressure distribution data. The model is posture-specific, I.e., parameters are optimized based on the detected posture. An artificial neural network (ANN) model was used to detect four bed postures to perform the kalman filter parameters' optimization step. The BRs of 12 healthy adults are recorded using the pressure mattress and a reference respiratory belt. To validate the method as a surrogate measure, a Bland-Altman (BA) analysis was performed on both pressure and belt data, and the linear relationship is evaluated using Pearson Correlation Coefficient (PCC). Interestingly, a high inter-rater agreement, an average maximum difference of 1.93 Breaths Per Minute (BrPM), a confidence interval of 95%, along with a strong linear relationship of 95.8% on average between the two methods were interestingly obtained. The presented results show the suitability of the proposed solution in medical applications requiring respiration monitoring.

Cardiorespiratory Monitoring Data during Sleep in Healthy Canadian Infants

Rationale: Sleep study interpretation in children needs to be based on age-specific normal values. Although several studies have reported normal cardiorespiratory parameters during sleep in children and adolescents, few have included younger children.Objectives: To describe cardiopulmonary indices, specifically oxygen saturation and heart rate, as well as frequency of obstructive and central apneas in healthy 1-year-old Canadian infants during sleep.Methods: Home sleep cardiorespiratory monitoring was performed among infants participating in the Edmonton subcohort of the CHILD (Canadian Healthy Infant Longitudinal Development) study at their 1-year follow-up visit. A portable sleep monitoring device, which included a nasal pressure cannula, an oronasal thermal airflow sensor, a pulse oximeter, and respiratory inductance plethysmography belts, was used to collect sleep architecture and cardiorespiratory data during one night of monitoring in the home. Sleep scoring was done in blocks of 5 minutes using a novel pilot sleep scoring algorithm.Results: Among the 562 subjects (mean ± standard deviation age 1.1 ± 0.2 yr) who attempted home sleep cardiorespiratory monitoring, 91% provided technically acceptable data with no loss of signal preventing analysis of any parameter. Obstructive and central apneas were rare, with a median obstructive apnea index of 0.0 events/h (10th percentile, 0.0; 90th percentile, 0.5) and a median central apnea index of 2.5 events/h (10th percentile, 0.6; 90th percentile, 7.1). Median oxygen saturation was 97.0% (10th percentile, 95.4; 90th percentile, 97.9). The oxygen desaturation index was 6.7 events/h (10th percentile, 1.4; 90th percentile, 15.8), with infants spending only 0.1% (10th percentile, 0.0; 90th percentile, 0.6) of the time with an oxygen saturation below 92%.Conclusions: These results provide important reference data for healthy infants undergoing cardiorespiratory monitoring during sleep.

Post-hoc physiological waveform extraction from motion estimation in simultaneous multislice (SMS) functional MRI using separate stack processing.

Motion estimation is an essential step in functional MRI (fMRI) preprocessing. Usually, fMRI processing software packages (eg, FSL and AFNI) automatically estimate motion parameters in order to counteract the effects of motion. However, the time courses of the motion estimation for fMRI data also contain information about physiological processes. Here, we show that respiration and cardiac signals can be extracted from motion estimation at significantly higher bandwidth than is possible with current methods. To detect motion at high effective temporal resolution (HighRes), the motion parameters of stacks of simultaneously acquired slices were estimated separately, then combined. This method was validated by extracting physiological motion signals from resting state fMRI (rsfMRI) data (Enhanced Nathan Kline Institute-Rockland Sample) and comparing them to respiration belt and pulse oximeter signals. HighRes motion time-courses with an effective sampling rate of 15.5 and 11.4 Hz were extracted from repetition time (TR) = 0.645 and 1.4 s data, respectively. Respiration waveforms were extracted with significantly higher accuracy than the original motion parameters. Even cardiac waveforms could be extracted, despite the fact that the sampling time or TR values were too long to sample cardiac frequencies. HighRes motion traces provide insight into the subjects' motion at higher frequencies than can be estimated using standard techniques. In its simplest form, this technique can recover accurate respiration signals and may reveal additional complexity in brain motion.

Analysis of Breathing Patterns from Thermal Images Using an Automated Segmentation Method

Breathing is one of the important vital signs in diagnosing and monitoring for patients’ treatment and disease. Few modalities have been used to evaluate breathing activity such as respiratory belt, thermistor and capacitive sensor. However, these requires external attachments such as electrode or sensor which might be inconvenience over long period of time. Hence, we proposed the use of thermography as a contactless monitoring device. In this study, inspiration time and expiration time of three different breathing patterns such as normal, prolonged and rapid breathing patterns were measured by using the thermography. Thermal images obtained from the subjects were processed and analysed by using an automated segmentation method which integrate the knowledge of edge-based and region-based segmentation methods into the algorithm developed. The algorithm developed in this study has shown that the tracker was able to segment the region of interest of the thermal images automatically and it provides a more accurate and stable results than manual calculation method. Thus, three different types of breathing patterns could be identified based on the inspiration time to expiration time ratio. Results shows that there was less than 5% of relative error which suggest the benefit of this algorithm.

Modulation of respiration pattern variability and its relation to anxiety symptoms in remitted recurrent depression

BackgroundDepression is related to default mode network (DMN) connectivity and higher respiration pattern variability (RPV). In addition, DMN connectivity and RPV are interrelated and predict a poorer clinical course of depression. The association of RPV and depression might further be boosted by anxiety levels. Aim of the present study was to investigate whether a mindfulness-based training in emotionally challenged remitted depressed participants (rMDD) leads to reduced DMN connectivity and lower RPV, and if RPV interacts with anxiety levels. MethodsTo challenge participants, sad mood was induced with keywords of personal negative life events in 49 rMDD during fMRI before and after a 4-week mindfulness-based attention training (MBAT) or progressive muscle relaxation. Respiration was measured by means of a built-in respiration belt. ResultsAfter both trainings, rMDD showed no significant changes in DMN connectivity. However, MBAT was effective in reducing the RPV which was related to lower anxiety levels especially in high anxious individuals. ConclusionsRPV can be influenced by training which may hint to an underlying biological pathway of training effects. Importantly, these effects seem to be associated with anxiety levels. Therefore, respiration focused training might be an important tool assisting the treatment of depression and anxiety.

An FMCW Radar for Localization and Vital Signs Measurement for Different Chest Orientations.

This work tests the ability of a frequency-modulated continuous wave (FMCW) radar to measure the respiratory rate and the heartbeat of a subject in challenging indoor scenarios. To simulate a realistic configuration for ambient assisted living (AAL) applications, in which the thorax orientation towards the antenna is typically unknown, four different scenarios were considered. Measurements were performed on five volunteers positioned with the chest, left, back, and right side facing the antenna, respectively. The GHz radar and the antennas used for the measurements were suitably designed for the considered application. To obtain a low cost and compact system, series-fed arrays were preferred over other antenna topologies. The geometry of the patches was opportunely shaped to reduce the side lobe level (SLL) and increase the bandwidth, thus ensuring good system performances. In all scenarios, the vital signs extracted from the radar signal were compared with the ones collected by a photoplethysmograph and a respiratory belt, used as references. A statistical analysis of the measured data on the different subjects and orientations was performed, showing that the radar was able to measure with high accuracy both the respiratory rate and the heartbeat in all considered configurations.

Hydrogen sulphide stimuli shorten exhalation during sleep as well as in wakefulness

In the attentive waking state, pleasant odours often prolong inhalation while unpleasant odours often shorten the exhalation. It should be checked whether this induced breathing pattern is maintained even during sleep. 23 healthy normosmic adults were examined by polysomnography for one night and randomized pulsed either with H2S, phenylethyl alcohol (PEA) or CO2 via a flow olfactometer. The determination of the sleep stages was based on the standard polysomnography curves. From the breathing curves (respiratory nasal pressure breathing, thoracic or abdominal belt breathing) a low-artefact curve was selected and seven breaths were measured from their breathing signal around the trigger impulse. The duration of inspiration (DIN) and the duration of the expiration (DEX) were determined from the six prestimulatory breaths and from breath with the stimulus onset and thus defined a reaction index (RI) indicating whether there is a significant change in shortening or prolonging DIN and/or DEX. These different RI were corrected by the spontaneous baseline RI and analysed according to the type of stimulus and the sleep stages. Reaction indices with reductions of DEX were larger than spontaneous RI and RI for PEA and H2S stimulation. In the case of CO2 irritation, RI with reductions of DIN and DEX were larger than with olfactory stimulation. All RI were equal in their amount between sleep stages. In REM, the difference between olfactory RI with shortened DEX between H2S and PEA stimulation was greatest. When stimulated with an unpleasant smell in sleep, the respiratory reaction pattern from the awake state is preserved. RI with shortened DEX can be considered as an imperfect arousal.

3D Camera and Pulse Oximeter for Respiratory Events Detection.

The purpose of this study was to derive a respiratory movement signal from a 3D time-of-flight camera and to investigate if it can be used in combination with SpO2 to detect respiratory events comparable to polysomnography (PSG) based detection. We derived a respiratory signal from a 3D camera and developed a new algorithm that detects reduced respiratory movement and SpO2 desaturation to score respiratory events. The method was tested on 61 patients' synchronized 3D video and PSG recordings. The predicted apnea-hypopnea index (AHI), calculated based on total sleep time, and predicted severity were compared to manual PSG annotations (manualPSG). Predicted AHI evaluation, measured by intraclass correlation (ICC), and severity classification were performed. Furthermore, the results were evaluated by 30-second epoch analysis, labelled either as respiratory event or normal breathing, wherein the accuracy, sensitivity, specificity and Cohen's kappa were calculated. The predicted AHI scored an ICC r = 0.94 (0.90 - 0.96 at 95% confidence interval, p < 0.001) compared to manualPSG. Severity classification scored 80% accuracy, with no misclassification by more than one severity level. Based on 30-second epoch analysis, the method scored a Cohen's kappa = 0.72, accuracy = 0.88, sensitivity = 0.80, and specificity = 0.91. Our detection method using SpO2 and 3D camera had excellent reliability and substantial agreement with PSG-based scoring. This method showed the potential to reliably detect respiratory events without airflow and respiratory belt sensors, sensors that can be uncomfortable to patients and susceptible to movement artefacts.