Development and clinical application of impedance pneumography technique

Assessment of the lung function is essential in the diagnosis and management of respiratory disease such as asthma. However, conventional spirometry requires difficult manoeuvres from the subject and is thus unsuitable for young children and infants. This renders the diagnosis of childhood asthma often qualitative, time-consuming and clinically challenging. However, information relating to the lung function can be derived from restful tidal breathing (TB) as well. Traditionally TB has been recorded in short intervals in laboratory conditions with obtrusive instrumentation using a face mask or a mouth piece. The principal aim of this thesis was to develop a noninvasive and convenient, yet highly accurate method for recording TB over extended time periods for clinical purposes, especially in young children. The measurement methodology developed within this thesis is based on impedance pneumography (IP), where breathing is recorded through the respiratory variations of the electrical impedance of the thorax. This is established by placing four skin electrodes on the upper body and connecting them to a recording device. The main focus was in ensuring the accuracy of the IP-derived tidal flow recording as compared to direct measurement from the mouth. This was established by attenuating the distortive cardiac oscillations (CGO) of the impedance signal and by optimising the locations of the skin electrodes. The complete method was then validated in healthy adults during respiratory loading (n=17) and in preschool children with wheezing disorder (n=20). The CGO attenuation was realised through an ensemble averaging based signal processing algorithm. The algorithm takes into account the respiratory modulation of the CGO waveform thus enabling efficient CGO attenuation while preserving the respiratory component of the signal unchanged. The newly proposed electrode configuration provides consistently more linear impedance to lung volume ratio than those previously established in the literature. The complete method integrating these developments provided highly accurate TB flow signal during normal and altered respiratory mechanics (loading) in adults and during induced bronchoconstriction in young children. It may be concluded that in this thesis significant improvements were realised with the IP technique. These improvements were experimentally validated in two studies and the integrated system was found to consistently provide an accurate respiratory flow signal. The method may have clinical implications for the diagnosis of respiratory diseases especially in non-cooperative subjects, such as young children

Ventilatory Mechanics in Endurance Athletes

The lungs were once thought to be over-built for exercise. However, upon further research, endurance athletes have been found to reach their maximum ventilation, demonstrating an insufficiency of the lungs to accommodate the demands of highly demanding endurance sport. This knowledge has inspired researchers to look further into the exercise ventilatory responses and, in doing so, researchers discovered that the adaptations of the pulmonary system to endurance training are still not well understood. Potential reasons for this lack of knowledge may be methodological measurement limitations, as ventilatory mechanics have been measured classically either invasively or by breathing maneuvers. These measurements are difficult to perform during high intensity exercise and in large groups of athletes. However, recent innovations in motion analysis technology have allowed for ventilatory mechanics to be measured during high intensity exercise, potentially allowing for further insight into how high intensity endurance training impacts ventilatory mechanics. The purpose of this study is to describe normal ventilatory mechanics during exercise in endurance trained and healthy untrained individuals, explore potential gender differences during exercise and investigate the impact of flow limitation during exercise on ventilatory mechanics, using a motion analysis system that allows researchers to obtain information on chest wall volume changes and chest wall compartmental interactions during high intensity exercise. This motion analysis system is called Optoelectronic Plethysmography (OEP). This dissertation is comprised of an introduction to the work and the 3 projects that comprise the dissertation along with an appendix, which includes a complete literature review. The three projects are as follows (1) an introduction to motion analysis as a tool in measuring ventilatory mechanics, (2) research determining the differences in the ventilatory mechanics in endurance athletes and healthy controls from rest to maximal exercise and (3) the differences in ventilatory mechanics between endurance trained women who demonstrate expiratory flow limitation during high intensity exercise versus endurance trained women who do not. Project 1: Optoelectronic Plethysmography (OEP) is a motion analysis tool that can be used to define exercise ventilatory mechanics by analyzing chest wall movements and calculating volume changes. By analyzing breathing mechanics by motion analysis rather than traditional breathing maneuvers, individual components of the chest wall can be analyzed and changes in volume throughout the chest wall can be assessed without altering the individual's natural breathing pattern. This review presents the history and development of OEP technology, along with a summary of the methods used and a discussion of findings to date, giving insight into exercise ventilatory mechanics never investigated before. Project 2: Differences between the ventilatory mechanics of endurance athletes and non athletes using motion analysis have not yet been described. To determine how increased ventilatory demand impacts ventilatory kinematics, we compared the total chest wall volume variations (VCW) of 18 male and female endurance-trained athletes (ET) to 14 untrained individuals (UT) during exercise. We hypothesized that training and gender would have an effect on VCW and kinematics at maximal exercise. Gender and training significantly influenced chest wall kinematics. Female ET did not change chest wall end-expiratory volume (VCW,ee) or pulmonary ribcage end-expiratory volume (VRCp,ee) with exercise, while female UT significantly decreased VCW,ee and VRCp,ee with exercise (p<0.05). Female ET significantly increased pulmonary ribcage end-inspiratory volume (VRCp,ei) with exercise (p<0.05), while female UT did not change VRCp,ei with exercise. Male ET significantly increased VRCp,ei with exercise (p<0.05); male UT did not. Men and women had significantly different VCW (p <0.05). Women demonstrated the greatest variation of VCW in the pulmonary ribcage compartment (VRCp). Men had similar volumes in the VRCp and the abdomen (VAb). In conclusion, gender and training had a significant association with ventilatory kinematics. Project 3: Research has found potential limitations of the airways to accommodate the large tidal volumes generated during high intensity exercise. This airway limitation has been defined as expiratory flow limitation (EFL) observed during high intensity exercise in a large percentage of healthy women. Because of endurance athletes' ability to exercise at high intensities for prolonged periods of time and produce greater than average tidal volumes, female endurance athletes may be particularly susceptible to EFL and the impact EFL may have on performance. The purpose of this last chapter was to investigate the ventilatory mechanics and exercise capacity parameters of female endurance athletes with and without EFL. Female competitive cyclists participated in two days of testing; day one consisted of a maximal aerobic capacity test (V ̇o2max test) with spirometry and day two involved chest wall motion analysis testing during two steady state exercise tests. Baseline flow volume loops were performed prior to exercise and repeated post exercise. During exercise participants performed flow volume loops at minutes 4, 6, 8 and last 30 seconds of exercise. EFL was considered present when the exercise flow volume loop surpassed the baseline flow volume loop. To quantify the degree of flow limitation when comparing the peak exercise flow volume loop to the baseline flow volume loop, we calculated the percent flow volume loop reserve (%FVL reserve). Two levels of submaximal constant-load exercise bouts (at 60% and 85% maximal watts) were employed to investigate if EEFL impacted ventilatory mechanics differently at different intensities. Optoelectronic plethysmography (OEP) was employed to measure VT from the pulmonary ribcage (VRCp), abdominal ribcage (VRCa) and the abdomen (VAb), as well as to measure end-expiratory volume chest wall volume (EEEV) to calculate potential dynamic hyperinflation. Comparison of participants with and without EFL was made using an ANOVA or Kruskal-Wallis test (p≤0.05). Predictors of %FVL reserve were explored with a multiple linear regression. Two participants were not included in the data analysis due to the presence of asthma (one at rest, one exercise induced) as determined by spirometry during day one testing. Out of the other 28 participants, 6 participants had definite EFL (DEFL) demonstrated by overlapping of the peak exercise flow volume loop with the pre and post exercise flow volume loop, 5 had borderline EFL (BEFL) demonstrated by an overlapping of only the pre exercise flow volume loop and 17 had no EFL (NEFL) demonstrated by no overlapping of the pre or post flow volume loops. All participants had within normal limits of the percent predicted normal reference values in resting forced expiratory volume in 1 second (FEV1), forced mid expiratory flow rates (FEF25-75L/sec), forced vital capacity (FVC) and FEV1/FVC ratio. DEFL and BEFL participants' had a significantly lower FEV1/FVC ratio compared to NEFL (p=0.003), DEFL had significantly lower FEF25-75% predicted normal reference values before and after exercise compared to NEFL (p=0.004). There were no differences in the exercise capacity values between groups. During the day two steady state tests, there was a significant interaction effect between groups and exercise intensity in the %VRCa (p=0.045) and % VAb (p=0.049). End-tidal carbon dioxide pressure, FEF25-75%, history of self reported excessive mucus with exercise and % VRCp during the 85% constant load test explained 71.6% of the variability in %FVL reserve in our regression model (p=0.002). Independent predictors of %FVL reserve were: end-tidal carbon dioxide pressure (p=0.033), FEF25-75% (p=0.010) and history of excessive mucus with exercise (0.014). In conclusion, female endurance athletes demonstrating EFL had normal but significantly different FeV1/FVC ratio and significantly different abdominal ribcage and abdomen percent contribution with increased exercise intensity, but similar exercise capacities compared to the female endurance athletes with no EFL. Also, independent predictors of %FVL reserve were found to be FEF25-75%, history of mucus production with exercise and end-tidal carbon dioxide level at peak exercise. This dissertation has provided further insight into the ventilatory mechanics of endurance athletes and how potential airway limitation can impact high intensity exercise. Further research can seek to better understand if the differences in ventilatory mechanics between endurance athletes with EFL and no EFL allow for preservation of exercise capacity in the presence of airway limitatio

Ventilatory mechanics in thoracic surgery

This thesis proved that chest wall motion analysis technology could be used in thoracic surgery to answer a number of clinical and physiological questions. We used it either as a diagnostic tool or for the evaluation of an intervention outcome. We divided its use as a diagnostic tool into two categories; 1- diagnosis before surgery and 2- diagnosis after surgery. In the evaluation of an intervention outcome, we divided its use after a number of interventions: 1. Cosmetic Surgery: Chapter 5: The Effect of Pectus Carinatum (Pigeon Chest) Repair on Chest Wall Mechanics 2. Prognostic Surgery: a) Chapter 4: The Effect of Chest Wall Reconstruction on Chest Wall Mechanics b) Chapter 10: Late Changes in Chest Wall Mechanics Post Lung Resection: The Effect of Lung Cancer Resection In COPD patients 3. Palliative Surgery: a) Chapter 6: The Effect of Lung Volume Reduction Surgery on Chest Wall Mechanics b) Chapter 3: The Effect of Diaphragmatic Plication (Fixation) on Chest Wall Mechanics 4. Post-operative Intervention: Chapter 8: The Effect of Thoracic Nerve Blocks on Chest Wall Mechanic

Characterization and processing of novel neck photoplethysmography signals for cardiorespiratory monitoring

Epilepsy is a neurological disorder causing serious brain seizures that severely affect the patients' quality of life. Sudden unexpected death in epilepsy (SUDEP), for which no evident decease reason is found after post-mortem examination, is a common cause of mortality. The mechanisms leading to SUDEP are uncertain, but, centrally mediated apneic respiratory dysfunction, inducing dangerous hypoxemia, plays a key role. Continuous physiological monitoring appears as the only reliable solution for SUDEP prevention. However, current seizure-detection systems do not show enough sensitivity and present a high number of intolerable false alarms. A wearable system capable of measuring several physiological signals from the same body location, could efficiently overcome these limitations. In this framework, a neck wearable apnea detection device (WADD), sensing airflow through tracheal sounds, was designed. Despite the promising performance, it is still necessary to integrate an oximeter sensor into the system, to measure oxygen saturation in blood (SpO2) from neck photoplethysmography (PPG) signals, and hence, support the apnea detection decision. The neck is a novel PPG measurement site that has not yet been thoroughly explored, due to numerous challenges. This research work aims to characterize neck PPG signals, in order to fully exploit this alternative pulse oximetry location, for precise cardiorespiratory biomarkers monitoring. In this thesis, neck PPG signals were recorded, for the first time in literature, in a series of experiments under different artifacts and respiratory conditions. Morphological and spectral characteristics were analyzed in order to identify potential singularities of the signals. The most common neck PPG artifacts critically corrupting the signal quality, and other breathing states of interest, were thoroughly characterized in terms of the most discriminative features. An algorithm was further developed to differentiate artifacts from clean PPG signals. Both, the proposed characterization and classification model can be useful tools for researchers to denoise neck PPG signals and exploit them in a variety of clinical contexts. In addition to that, it was demonstrated that the neck also offered the possibility, unlike other body parts, to extract the Jugular Venous Pulse (JVP) non-invasively. Overall, the thesis showed how the neck could be an optimum location for multi-modal monitoring in the context of diseases affecting respiration, since it not only allows the sensing of airflow related signals, but also, the breathing frequency component of the PPG appeared more prominent than in the standard finger location. In this context, this property enabled the extraction of relevant features to develop a promising algorithm for apnea detection in near-real time. These findings could be of great importance for SUDEP prevention, facilitating the investigation of the mechanisms and risk factors associated to it, and ultimately reduce epilepsy mortality.Open Acces

A contribution to unobtrusive video-based measurement of respiratory signals

Due to the growing popularity of video-based methods for physiological signal measurement, and taking into account the technological advancements of these type of devices, this work proposes a series of new novel methods to obtain the respiratory signal from a distance, based on video analysis. This thesis aims to improve the state of the art video methods for respiratory measurement, more specifically, by presenting methods that can be used to obtain respiratory variability or perform respiratory rhythm measurements. Moreover, this thesis also aims to present a new implementation of a time-frequency signal processing technique, to improve its computational efficiency when applied to the respiratory signals. In this document a first approach to video-based methods for respiratory signal measurement is performed, to assert the feasibility of using a consumer-grade camera, not only to measure the mean respiratory rate or frequency, but to assert if this hardware could be used to acquire the raw respiratory signal and the respiratory rhythm as well. In this regard a new video-based method was introduced that measures the respiratory signal of a subject at a distance, with the aid of a custom pattern placed on the thorax of the subject. Given the results from the first video-based method, a more broad approach was taken by comparing three different types of video hardware, with the aim to characterise if they could be used for respiratory signal acquisition and respiratory variability measurements. The comparative analysis was performed in terms of instantaneous frequency, as it allowed to characterise the methods in terms of respiratory variability and to compare them in the same terms with the reference method. Subsequently, and due to the previous obtained results, a new method was proposed using a stereo depth camera with the aim to tackle the limitations of the previous study. The proposed method uses an hybrid architecture were the synchronized infrared frame and depth point-cloud from the same camera are acquired. The infrared frame is used to detect the movements of the subject inside the scene, and to recompute on demand a region of interest to obtain the respiratory signal from the depth point-cloud. Furthermore, in this study an opportunistic approach is taken in order to process all the obtained data, as it is also the aim of this study to verify if using a more realistic approach to respiratory signal analysis in real-life conditions, would influence the respiratory rhythm measurement. Even though the depth camera method proved reliable in terms of respiratory rhythm measurement, the opportunistic approach relied on visual inspection of the obtained respiratory signal to properly define each piece. For this reason, a quality indicator had to be proposed that could objectively identify whenever a respiratory signal contained errors. Furthermore, from the idea to characterise the movements of a subject, and by changing the measuring point from a frontal to a lateral perspective to avoid most of the occlusions, a new method based on obtaining the movement of the thoraco-abdominal region using dense optical flow was proposed. This method makes us of the phase of the optical flow to obtain the respiratory signal of the subject, while using the modulus to compute a quality index. Finally, regarding the different signal processing methods used in this thesis to obtain the instantaneous frequency, there were none that could perform in real-time, making the analysis of the respiratory variability not possible in real-life systems where the signals have to be processed in a sample by sample basis. For this reason, as a final chapter a new implementation of the synchrosqueezing transform for time-frequency analysis in real-time is proposed, with the aim to provide a new tool for non-contact methods to obtain the variability of the respiratory signal in real-time.A causa de la creixent popularitat en la mesura de senyals fisiològics amb mètodes de vídeo, i tenint en compte els avenços tecnològics d'aquests dispositius, aquesta tesi proposa una sèrie de nous mètodes per tal d'obtenir la respiració a distància mitjançant l'anàlisi de vídeo. Aquesta tesi té com a objectiu millorar l'estat de l'art referent a la mesura de senyal respiratòria mitjançant els mètodes que en ella es descriuen, així com presentar mètodes que puguin ser usats per obtenir la variabilitat o el ritme respiratori. A més, aquesta tesi té com a objectiu presentar una nova implementació d'un mètode de processat de senyal temps-freqüencial, per tal de millorar-ne l'eficiència computacional quant s’aplica a senyals respiratoris. En aquest document, es realitza una primera aproximació a la mesura de senyal respiratòria mitjançant mètodes de vídeo per tal de verificar si és factible utilitzar una càmera de consum, no només per mesurar el senyal respiratori, sinó verificar si aquest tipus de hardware també pot ser emprat per obtenir el ritme respiratori. En aquest sentit, es presenta en aquest document un nou mètode d'adquisició de senyal respiratòria a distància basat en vídeo, el qual fa ús d'un patró ubicat al tòrax del subjecte per tal d'obtenir-ne la respiració. Un cop obtinguts els resultats del primers resultats, s'han analitzat tres tipus diferents de càmeres, amb la finalitat de caracteritzar-ne la viabilitat d'obtenir el senyal respiratori i la seva variabilitat. L'estudi comparatiu s'ha realitzat en termes de freqüència instantània, donat que permet caracteritzar els mètodes en termes de variabilitat respiratòria i comparar-los, en les mateixes condicions, amb el mètode de referencia. A continuació, s'ha presentat un nou mètode basat en una càmera de profunditat estèreo amb la finalitat de millorar i corregir les limitacions anteriors. El nou mètode proposat es basa en una arquitectura hibrida la qual utilitza els canals de vídeo infraroig i de profunditat de forma sincronitzada. El canal infraroig s'utilitza per detectar els moviments del subjecte dins l'escena i calcular, sota demanda, una regió d'interès que s'utilitza posteriorment en el canal de profunditat per extreure el senyal respiratori. A més a més, en aquest estudi s'ha utilitzat una aproximació oportunista en el processat del senyal respiratori, donat que també és un dels objectius d'aquest estudi, verificar si el fet d'utilitzar una aproximació més realista en l'adquisició de senyal, pot influir en la mesura del ritme respiratori. Tot i que el mètode anterior es mostra fiable en termes de mesura del ritme respiratori, la selecció oportunista del senyal necessita d’inspecció visual per tal de definir correctament cada fragment. Per aquest motiu, era necessari definir un índex de qualitat el qual permetés identificar de forma objectiva cada tram de senyal, així com detectar si el senyal conté errors. Partint de la idea de caracteritzar el moviment del subjecte de l'estudi anterior, i modificant el punt de mesura frontal cap a un de lateral per tal d'evitar oclusions, es proposa un nou mètode basat en l'obtenció del moviment toràcic-abdominal a partir del flux òptic del senyal de vídeo. Aquest mètode recupera el senyal respiratori del subjecte a partir de la fase del flux òptic, tot calculant un índex de qualitat a partir del mòdul. Finalment, i tenint en compte els diferents mètodes de processat utilitzats en aquesta tesi per tal de obtenir la freqüència instantània, es pot apreciar que cap d'ells és capaç de funcionar en temps real, fent inviable l'anàlisi de la variabilitat respiratòria en sistemes reals amb processat mostra a mostra. Per aquest motiu, en el capítol final d'aquesta tesi, s'ha proposat una nova implementació de la transformació "synchrosqueezing" per tal de realitzar l’anàlisi temporal-freqüencial en temps real, i proveir d'una nova eina per tal d'obtenir la variabilitat respiratòria en temps real, amb mètodes sense contacte

RESPIRATORY RESISTANCE AND THE EFFECT OF EXERCISE IN FEMALE TEEN ATHLETES WITH PARADOXICAL VOCAL FOLD MOTION

Paradoxical vocal fold motion (PVFM) disorder, often referred to as vocal cord dysfunction (VCD), interferes with breathing because the vocal folds adduct during inspiration making it difficult to inhale. When PVFM is triggered by exercise, it can impact competitive play. Athletes with PVFM are often misdiagnosed as having exercise-induced asthma, but do not respond to asthma treatment. Directly visualizing the larynx (laryngoscopy) when symptoms are present is the current "gold standard" for diagnosing PVFM. However, laryngoscopy is invasive and expensive. Standardized noninvasive alternative methodologies are needed for clinically feasible assessment of PVFM by the speech-language pathologist. Respiratory resistance (Rr), measured with the Airflow Perturbation Device (APD), may be useful for assessing PVFM because vocal fold adduction can increase Rr markedly. This research comprises three studies with an overarching goal to validate an objective, non-invasive measure of Rr for identifying abnormal constriction of the laryngeal airway associated with PVFM disorder. Study 1 compared APD-measured Rr to glottal area (GA) assessed through laryngoscopy in a healthy subject feigning PVFM-type breathing. Study 2 assessed intra- and intersession test-retest reliability of APD-determined Rr for a control group of 12 healthy female teenage athletes during resting tidal breathing (RTB) and post-exercise breathing (PEB). Study 3 examined differences between the same 12 healthy athletes with 12 athletes diagnosed with PVFM matched for sex, age, and activity level, for Rr, exercise duration, and dyspnea ratings for RTB and PEB. The results revealed: 1) a strong negative correlation (r = -0.824) between Rr and GA suggesting that the APD can indirectly measure changes in the laryngeal airway; 2) strong test-retest reliability for APD-measured inspiratory (Ri) and expiratory (Re) resistance during RTB (ICC > .95), and PEB (ICC >.85); and 3) in control athletes, Ri and Re decreased during PEB as compared with RTB, whereas in athletes with PVFM, both Ri and Re increased during PEB with statistical significance reached for Ri (p <.001). During exercise, athletes with PVFM reported severe dyspnea and exercised for shorter durations. This research demonstrates that a diagnostic protocol for PVFM should include measures of Rr, exercise duration, and perceived dyspnea

Conception et implémentation d'un réseau sans-fil pour la surveillance continue des signes vitaux

Les dépenses de santé augmentent continuellement année après année et prennent une grande partie du budget d’un pays. Pendant les soins médicaux, les signes vitaux, tels que le rythme cardiaque et la respiration, sont des paramètres clés qui sont surveillés en permanence. La toux est un indicateur important de plusieurs problèmes comme la maladie pulmonaire obstructive chronique (MPOC), et c’est aussi la principale raison pour laquelle les patients consultent un médecin. En fait, c’est un mécanisme de défense pulmonaire des voies respiratoires qui permet l’expulsion de substances indésirables et irritantes. Les capteurs de corps sans fil sont de plus en plus utilisés par les cliniciens et les chercheurs, dans un large éventail d’applications telles que le sport, l’ingénierie spatiale et la médecine. La surveillance des signes vitaux en temps réel peut considérablement augmenter la précision du diagnostic et peut permettre des méthodes de guérison automatiques, par exemple, la détection et l’arrêt des crises d’épilepsie ou de narcolepsie. Les paramètres respiratoires sont essentiels en oxygénothérapie, en milieu hospitalier et en surveillance ambulatoire, tandis que l’évaluation de la sévérité de la toux est essentielle pour traiter plusieurs maladies, comme la bronchopneumopathie chronique obstructive (BPCO). Dans cette thèse, un système de surveillance respiratoire sans fil de faible puissance avec détection de la toux est présenté. Ce système utilise des capteurs multimodaux, portables et sans-fils, conçus à l’aide de composants conventionnels disponibles dans le commerce. Ces capteurs portables utilisent une unité de mesure inertielle à 9 axes de faible puissance pour mesurer la fréquence respiratoire, et un microphone MEMS pour effectuer la détection de la toux. L’architecture de chaque capteur sans fil est présentée. De plus, les résultats montrent que le capteur à petite taille de 26,67 x 65,53 mm² consomme environ 12 à 16,2 mA et peut durer au moins 6 heures avec une batterie lithium-ion miniature de 100 mA. L’unité d’acquisition, l’unité de communication sans fil et les algorithmes de traitement de données sont décrits. Les performances du réseau de capteurs sont présentées pour des tests expérimentaux en comparant avec la pléthysmographie d’inductance respiratoire.Health care expenses are continuously increasing year after year and taking a large part of a country’s budget. During medical care, vital signs, such as heart and breathing rates, are key parameters that are continuously monitored. Coughing is a prominent indicator of several problems such as COPD, and it is also the main reason for why patients seek medical advice. In fact, it is a pulmonary defense mechanism of the respiratory tract that allows the expulsion of undesirable and irritating substances. Wireless body sensors are increasingly used by clinicians and researchers, in a wide range of applications such as sports, space engineering and medicine. Monitoring vital signs in real time can dramatically increase diagnosis accuracy and enable automatic curing procedures, e.g. detect and stop epilepsy or narcolepsy seizures. Breathing parameters are critical in oxygen therapy, hospital and ambulatory monitoring, while the assessment of cough severity is essential when dealing with several diseases, such as chronic obstructive pulmonary disease (COPD). In this thesis, a low-power wireless respiratory monitoring system with cough detection is proposed to measure the breathing rate and the frequency of coughing. This system uses wearable wireless multimodal patch sensors, designed using off the shelf components. These wearable sensors use a low-power 9-axis inertial measurement unit to measure the respiratory frequency, and a MEMs microphone to perform cough detection. The architecture of each wireless patch-sensor is presented. In fact, the results show that the small 26.67 x 65.53 mm² patch-sensor consumes around 12 to 16.2 mA, and can last at least 6 hours with a miniature 100 mA lithium ion battery. The acquisition unit, the wireless communication unit and the data processing algorithms are described. The proposed network performance is presented for experimental tests with a freely behaving user in parallel with the gold standard respiratory inductance plethysmograph

The design and evaluation of discrete wearable medical devices for vital signs monitoring

The observation, recording and appraisal of an individual’s vital signs, namely temperature, heart rate, blood pressure, respiratory rate and blood oxygen saturation (SpO2), are key components in the assessment of their health and wellbeing. Measurements provide valuable diagnostic data, facilitating clinical diagnosis, management and monitoring. Respiratory rate sensing is perhaps the most under-utilised of all the vital signs, being routinely assessed by observation or estimated algorithmically from respiratory-induced beat-to-beat variation in heart rate. Moreover there is an unmet need for wearable devices that can measure all or most of the vital signs. This project therefore aims to a) develop a device that can measure respiratory rate and b) develop a wearable device that can measure all or most of the vital signs. An accelerometer-based clavicular respiratory motion sensor was developed and compared with a similar thoracic motion sensor and reference using exhalatory flow. Pilot study results established that the clavicle sensor accurately tracked the reference in monitoring respiratory rate and outperformed the thoracic device. An Ear-worn Patient Monitoring System (EPMS) was also developed, providing a discrete telemonitoring device capable of rapidly measuring tympanic temperature, heart rate, SpO2 and activity level. The results of a comparative pilot study against reference instruments revealed that heart rate matched the reference for accuracy, while temperature under read (< 1°C) and SpO2 was inconsistent with poor correlation. In conclusion, both of the prototype devices require further development. The respiratory sensor would benefit from product engineering and larger scale testing to fully exploit the technology, but could find use in both hospital and community-based The design and evaluation of discrete wearable medical devices for vital signs monitoring DG Pitts ii Cranfield University monitoring. The EPMS has potential for clinical and community use, having demonstrated its capability of rapidly capturing and wirelessly transmitting vital signs readings. Further development is nevertheless required to improve the thermometer probe and resolve outstanding issues with SpO2 readings