Frequency Domain Diffuse Optical Spectroscopy (FD-DOS) is an emerging optical technique that uses near infrared light to probe the hemodynamics of biological tissue. Compared to more common Continuous Wave (CW) methods, FD-DOS uses light that is temporally modulated on the order of MHz to quantify the absorption and scattering of tissue. FD-DOS can also be used to obtain absolute concentration of tissue chromophores such as oxy- and deoxy-hemoglobin, which allow for quantitative measurements of tissue hemodynamics. This dissertation focuses on the evolution of our lab’s custom digital FD-DOS as a platform for taking optical measurement of biological tissue for respiratory and cardiovascular applications. Several important instrumentation improvements will be reviewed that have enhanced the performance of the system while making it more portable and clinic ready. Two translational applications will be described in detail: 1) the use of high-speed FD-DOS for the non-invasive extraction of venous oxygen saturation (SvO2) and 2) the use of FD-DOS to monitor the hemodynamics of the sternocleidomastoid (SCM) muscle towards the non-invasive monitoring of patients on mechanical ventilation. The custom FD-DOS system parameters were adjusted for each application, with a focus on high speed to extract the cardiac signal for the SvO2 project, and a focus on high SNR to measure the highly absorbing SCM. Measurements on healthy volunteers and rabbits were used to assess the feasibility of using FD-DOS for these applications. Finally, preliminary work was conducted to characterize a miniature FD-DOS source and detector with the goal of moving towards a wearable version of FD-DOS. / 2022-05-15T00:00:00Z

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Τα τελευταία χρόνια, οι μη επεμβατικές μέθοδοι διάγνωσης αλλά και θεραπείας κερδίζουν συνεχώς έδαφος έναντι των παραδοσιακών επεμβατικών μεθόδων. Σκοπός της διπλωματικής αυτής εργασίας είναι η μελέτη της μετάδοσης του φωτός μέσα στο ανθρώπινο δέρμα και κυρίως η μελέτη της απορρόφησης που υφίσταται από αυτό, με σκοπό την μέτρηση βιολογικών συντελεστών, όπως οι συγκεντρώσεις κάποιων ουσιών στον οργανισμό, ο υπολογισμός των οποίων μπορεί να οδηγήσει σε χρήσιμα διαγνωστικά συμπεράσματα. Επίσης, αναλύεται η μέθοδος της παλμικής οξυμετρίας, που χρησιμοποιείται ευρύτατα για την παρακολούθηση του αρτηριακού κορεσμού οξυγόνου και του καρδιακού παλμού. Μετρώντας την απορρόφηση του φωτός σε δύο διαφορετικά μήκη κύματος, ένα στο ερυθρό (660 nm) και ένα στο εγγύς υπέρυθρο (940 nm), και απομονώνοντας το μεταβαλλόμενο μέρος αυτής, που οφείλεται στις διακυμάνσεις στον όγκο του αρτηριακού αίματος, μπορούμε να υπολογίσουμε με τη χρήση του νόμου των Beer-Lambert τον κορεσμό του αίματος σε οξυγόνο μέσω του υπολογισμού των συγκεντρώσεων του σε μειωμένη αιμογλοβίνη και σε οξυαιμογλοβίνη. Τέλος, περιγράφεται η υλοποίηση της μεθόδου και ο σχεδιασμός ενός παλμικού οξυμέτρου ενός chip με τη χρήση του μικροεπεξεργαστή MSP430. / Over recent years, non-invasive methods of diagnosis and treatment are gaining ground against the traditional invasive methods. In this thesis, an integrated review of the transfer of optical radiation into human skin and primarily light absorption through human skin is presented, aiming at measuring biological information, such as concentrations of certain substances in the human body, whose calculation can lead to useful diagnostic conclusions. The method of Pulse Oximetry, which is widely used for monitoring arterial oxygen saturation and heart rate of a patient, is also presented. By measuring the absorption of light at two different wavelengths, one red (660 nm) and one near-infrared (940 nm), and isolating its AC component, which is a result of the variations in the volume of arterial blood, we can calculate the oxygen saturation using the Beer-Lambert law, by estimating the concentrations of oxyhemoglobin and reduced hemoglobin. Moreover, the implementation of a single chip portable pulse oximeter using the ultra low power capability of the MSP430 is demonstrated.

Le glaucome est une neuropathie optique progressive caractérisée par une perte des fibres nerveuses ganglionnaires. Cette atteinte provoque une diminution graduelle du champ visuel pouvant mener à la cécité. Cependant, le glaucome est présent chez plusieurs patients qui ne présente pas une pression intraoculaire élevée et plusieurs patients ayant une pression intraoculaire anormalement élevée ne développent pas le glaucome. Pour mieux comprendre la pathophysiologie de la maladie, plusieurs chercheurs se sont intéressés aux composantes hémodynamiques de l’œil. L’oxymétrie oculaire est représentée par plusieurs technologies commercialement disponibles qui proposent de mesurer de façon non invasive la saturation en oxygène des structures vasculaires de l’œil. Plusieurs études ont évaluées l’association entre l’état d’oxygénation des différentes structures rétiniennes et le glaucome. L’objectif de cette étude était de vérifier la répétabilité des mesures d’oxymétrie à la tête du nerf optique obtenues avec l’appareil Zilia ainsi que d’étudier l’acquisition afin de déterminer les caractéristiques nécessaires pour obtenir des résultats optimaux. De plus, cette étude a comparé la saturation en oxygène (SaO2) mesurée sur la tête du nerf optique de sujets normaux et de personnes atteintes de glaucome. Une corrélation a aussi été faite entre les valeurs d’oxymétrie et les différentes variable affectées dans le glaucome Ceci est une étude prospective à mesures répétées et à cas-témoins. Les participants ont été recrutés à l’Institut de l’œil des Laurentides. Les participants complétaient un examen oculovisuel complet en plus d’une mesure de la pression artérielle et de la saturation en oxygène pulsée (SpO2). Les valeurs de l’oxymétrie oculaire étaient obtenues avec l’appareil Zilia sur la portion temporale du nerf optique et le logiciel intégré permettait d’obtenir la valeur moyenne de l’acquisition. Aucune différence statistiquement significative n’a été obtenue entre la moyenne des trois mesures de la SaO2 au niveau du nerf optique. Pour la durée de l’acquisition, l’analyse des données a démontré une différence statistiquement significative entre les différentes durées sélectionnées, démontrant une différence entre les acquisitions d’une durée de 5 secondes comparativement aux autres durée d’acquisition. Il n’y avait pas de différence statistiquement significative entre la moyenne de la première mesure obtenue avant et après l’utilisation de la technique d’optimisation. Les résultats indiquent aussi une différence significative entre les valeurs moyennes de SaO2 mesurées à la tête du nerf optique des sujets glaucomateux comparativement aux sujets normaux. On note également une corrélation significative entre les valeurs de SaO2 et le RNFL global obtenu avec l’OCT. Cette étude constitue l’une des premières effectuées avec l’appareil Zilia. Les valeurs moyennes de la SaO2 obtenues à un point précis du nerf optique acquis par l’appareil Zilia sont répétables et une acquisition de 10 secondes pourrait permettre d’obtenir une valeur adéquate. La SaO2 mesurée par l’appareil Zilia sur la tête du nerf optique est diminuée chez les patients atteints de glaucome comparativement aux sujets sains. Il semble aussi avoir une relation entre la valeur de la SaO2 et l’épaisseur du RNFL. Plus d’études sont nécessaires afin d’établir le rôle de cet appareil dans le diagnostic et la gestion des patients atteints de glaucome. / Glaucoma is a progressive optic neuropathy characterized by loss of the retinal nerve fibers layer. This disease causes a decrease in the visual field that can lead to blindness. The main risk factor for glaucoma is the increase of intraocular pressure. However, not all glaucoma patients have an elevated intraocular pressure and many patients continue to progress despite good intraocular pressure control with current therapies. Several authors have focused on the hemodynamic components of the eye. They obtained significant differences in these factors between normal and glaucoma patients. Ocular oximetry is technology that can non-invasively measure oxygen saturation of eye tissues. Several studies have verified the association between ocular oximetry and glaucoma. The Zilia device uses diffuse spectroscopic reflectance to measure oxygen saturation at a specific point. The objective of this study was to verify the repeatability of the oximetry measurements on the head of the optic nerve obtained with the Zilia device and to study the acquisition in order to determine the characteristics necessary to obtain it optimally. Also, we measured the oxygen saturation (SaO2) on the optic nerve of normal subjects and compared it with patients with glaucoma. Additionally, the SaO2 was correlated with different variables affected by glaucoma. This is a prospective repeated-measures and case-cohort study. Participants were recruited at the Laurentian Eye Institute (IOL). They completed a complete eye exam under pupil dilation including a blood pressure measurement with an automated device and the pulse oximetry was obtained by a pulse oximeter (SpO2). The ocular oximetry measures was acquired by the Zilia imaging system on the temporal side of the optic nerve. No statistically significant differences were observed between the average of three SaO2 measurements at the optic nerve. For the duration of the acquisition, the data analysis showed a statistically significant difference between the 5 seconds acquisition compared to the other acquisition duration. There was no statistically significant difference between the average of the first measurement obtained before and after the use of the data optimization technique. The result showed a significant difference in the SaO2 values between glaucomatous participants and normal. We also see a correlation statistically significantly between the SaO2 values and the global RNFL. This study is one of the first one done with the Zilia device. The average value of SaO2 obtained at a specific point of the optic nerve acquired by the Zilia device are repeatable and a 10-second acquisition could provide a precise value. Also, the SaO2 measured with the Zilia imaging system on the optic nerve is significantly lower in glaucoma patients compared to normal patients. More studies are needed to really establish the role of that device in the diagnostic and fully up of patients with glaucoma.

Apple WatchTM huserar funktionaliteter inom medicinteknik. Detta är ett examensarbete inom medicinteknik som ställer frågan om hur pass bra mätningar den utför i förhållande till motsvarande medicinteknisk produkt. Smartklockan kan identifiera R-toppar i EKG mycketväl, och därigenom också förmaksflimmer. I förhållande till pulsoximeter presenteras syremättnad några procentenheter för högt och följsamheten är något stel. Apple WatchTM mäter puls bra vid högre hjärtslagsfrekvenser, men har kraftigt begränsad träffsäkerhet och sämre följsamhet vid mätningar i vila. Det kan inte styrkas att Apple WatchTM kan användas som verktyg för att ställa någon medicinsk diagnos, utifrån testerna i detta arbetet, där datamängd och urvalsgrupp samtidigt varit för liten för att kunna ge riktig statistisk signifikans. / The Apple WatchTM has functionalities related to the field of medical technology. This is a degree project in medical engineering that raises the question how adequate measurements it can acquire, in relation to a corresponding medical device. The Apple WatchTM can identify R waves in ECG very well and thereby also atrial fibrillation. In relation to pulse oximeters, oxygen saturation is given a few percentage points too high and the compliance is somewhat rigid. Apple WatchTM measures heart rate well at higher heart rates, but has severely limited accuracy and has poorer compliance when measuring at rest. The tests of this work shows that the Apple WatchTM should not be used as a tool for making any medical diagnosis, but the amount of data and test subjects were not sufficient enough to make it statistically significant.

Background: Ice hockey is a fast-paced sport with a high possibility of acquiring dental damage and concussions which can be prevented by mouthguards (MG). Despite this, many athletes choose not to use MG due to drawbacks such as discomfort and restricted airways. Restricted airways provided by MG might be reduced by external nasal dilator strips (ENDS). ENDS could contribute to increased aerobic capacity, blood oxygen saturation and self-reported compliance of ENDS by elevating airflow through the nose. Therefore, ENDS could contribute to enhanced performance and recovery rate while reducing the discomfort of MG that could lead to an increased usage of MG among healthy young adult ice hockey players. Aim: The aim was to study aerobic capacity, and oxygen saturation using mouthguard with and without external nasal dilator strips during submaximal bicycle tests. A second aim was to study the compliance of external nasal dilator strips when using mouthguard in healthy young adult ice hockey players. Method: In this experimental study using a cross-over design 15 young adult ice hockey players were contacted to attend on two separate test occasions, with and without ENDS. Aerobic capacity was measured with a Ekblom-Bak submaximal bicycle test (VO2max) and a pulse oximeter was used to examine oxygen saturation (%SpO2). Post-testing, the participants stated self-reported compliance using ENDS based on the numeric rating scale (0-10, positive-negative attitude of usage). Data are presented as mean and standard deviation. Differences between groups were analyzed with the Wilcoxon- signed rank test based on median (Q1-Q3). Result: Nine participants, aged 18-19 completed both test occasions. This study found that ENDS provided no significant difference in estimated VO2max mean (±SD), with ENDS 63.3 (±5.5) and without ENDS 64.2 (±5.0), nor %SpO2 during standard load. A significant increase showed in %SpO2 for higher individual load by 3%, with ENDS 97.1 (±1.3) and without ENDS 94.1 (±4.5). The participants experienced the test as more strenuous with ENDS than without ENDS applied, without significant difference. Despite this, the participants had a positive attitude towards the usage of ENDS. Conclusion This study regarding healthy young adult ice hockey players showed that ENDS provided no significant difference in aerobic capacity. Oxygen saturation however resulted in a positive significant difference at the higher individual load. The majority of the participants in this study propose a positive compliance with ENDS. The results are interpreted with caution due to the small sample.

Le glaucome représente la première cause de cécité irréversible à l’échelle mondiale. C’est une maladie neuro-dégénérative caractérisée traditionnellement par une pression intraoculaire (PIO) élevée, un dommage du nerf optique et un défaut du champ visuel correspondant. En fait, la PIO élevée constitue le facteur de risque central associé au développement du glaucome. Cependant, en dépit d’un contrôle adéquat de la PIO, la maladie continue à progresser chez certains patients. Cela montre qu’il existe d’autres facteurs impliqués dans la pathogenèse du glaucome. Des études récentes indiquent qu’un dérèglement de l’oxygène est associé à son développement. En utilisant une nouvelle technologie multi-spectrale capable de mesurer la saturation en oxygène (SaO2) dans les structures capillaires de la rétine, cette étude tentera de déterminer si un état d’oxygénation anormal pourrait se retrouver à la papille optique des patients souffrant de glaucome. Une meilleure compréhension du rôle de l’oxygène pourrait aider à améliorer le pronostic du glaucome. Les résultats de l’étude indiquent que le facteur de position (supérieure, temporale et inférieure de la papille optique) n’a aucun effet sur la mesure SaO2 ainsi que sa variabilité chez les patients normaux. La comparaison de la SaO2 entre les sujets normaux et glaucomateux ne montre pas de différence statistiquement significative. En conclusion, la SaO2 «normale» mesurée dans les yeux glaucomateux n'exclut pas nécessairement que l'hypoxie ne soit pas impliquée dans la pathogenèse. Au moment de l’étude, la PIO était bien contrôlée par des médicaments topiques, ce qui pourrait influencer l’oxygénation à la papille optique. / Glaucoma is the leading cause of irreversible blindness worldwide. Traditionally, open-angle glaucoma was defined as a neurodegenerative disease characterized by high intraocular pressure (IOP), progressive retinal cell death with subsequent visual field loss. Elevated IOP has been identified as one of the major risk factors for glaucomatous optic nerve damage. However, adequate IOP control cannot prevent progression of the disease in all patients suggesting that there are other factors involved in the pathogenesis of glaucoma. Recent studies suggest that hypoxia may contribute to the development of glaucoma. Using a new multi-spectral detection system of oxygen saturation (O2Sa), this study determined whether an abnormal state of oxygenation at the optic disc could be found in glaucoma patients. Knowledge about the influence of the oxygen in glaucoma may help to improve the pronostic of the disease. The results of the study indicate that the position factor (superior, temporal and inferior of the optic nerve head) has no effect on the measurement of O2Sa and its variability in normal patients. Comparing the O2Sa between normal subjects and glaucoma subjects shows no statistically significant difference. In conclusion, the «normal» O2Sa measured in glaucomatous eyes does not necessarily exclude that hypoxia is not involved in the pathogenesis of glaucoma because glaucoma patients were under treatment with topical drops that lowered IOP. These medicines could affect the oxygenation of the optic disc.

"Non-invasive remote physiological monitoring of soldiers on the battlefield has the potential to provide fast, accurate status assessments that are key to improving the survivability of critical injuries. The development of WPI’s wearable wireless pulse oximeter, designed for field-based applications, has allowed for the optimization of important hardware features such as physical size and power management. However, software-based digital signal processing (DSP) methods are still required to perform physiological assessments. This research evaluated DSP methods that were capable of providing arterial oxygen saturation (SpO2), heart rate (HR), heart rate variability (HRV), and respiration rate (RR) measurements derived from data acquired using a single optical sensor. In vivo experiments were conducted to evaluate the accuracies of the processing methods across ranges of physiological conditions. Of the algorithms assessed, 13 SpO2 methods, 1 HR method, 6 HRV indices, and 4 RR methods were identified that provided clinically acceptable measurement accuracies and could potentially be employed in a wearable pulse oximeter."

Existant en tant que pratique sportive, l’apnée est également de plus en plus utilisée dans d’autres activités sportives dont la natation, à l’entraînement et/ou en compétition. Toutefois, les réponses à l‘apnée dynamique ont été peu explorées lors d’efforts physiques intenses, en particulier en natation. L’objectif de ce travail de thèse est donc d’étudier sur le terrain en situation de nage (étude 1 et 2) et en laboratoire (étude 3) lors d’un exercice intermittent de pédalage, les réponses physiologiques, psychologiques et ergogéniques à l’apnée aiguë apparaissant lors d’efforts intenses. Le métabolisme a été notamment évalué à partir de la mesure de l’oxygénation tissulaire, de paramètres sanguins et de marqueurs hormonaux. Les principaux résultats de ces études montrent qu’en apnée la performance dépendrait de la capacité des sujets à maintenir leur fréquence cardiaque et que l’effort est globalement perçu comme plus dur. L’apnée n’induisait pas d’augmentation de la lactatémie, sans doute en lien avec l’absence de modification de l’extraction musculaire de l’oxygène. Au niveau cérébral, le maintien de l’oxygénation expliquerait la non modification du temps de réaction en apnée. Enfin toutes nos études ont révélé une désaturation artérielle significative en apnée, dès la première apnée de 10 secondes (étude 3) mais sans effet de la capacité d’apnée (étude 1) ou de l’intensité de nage (étude 2) suggérant que la durée compenserait l’intensité. Il serait donc intéressant d’étudier ultérieurement les effets respectifs du couple intensité/durée et les effets chroniques d’un entraînement comportant un exercice intermittent intense lors d’apnées dynamiques. / Existing as a sport practice, apnea is also increasingly used in other sports activities including swimming, training and/or competition. However, responses to dynamic apnea have been little explored during intense physical exercise, especially in swimming. The objective of this thesis is to study, in the field in swimming situations (study 1 and 2) and in the laboratory (study 3) during an intermittent cycling exercise, the physiological, psychological and ergogenic responses to acute apnea appearing during intense exercises. Metabolism was especially assessed by measurement of tissue oxygenation, blood parameters and hormonal markers. The main results of these studies show that in apnea the performance would depend on the ability of the subjects to maintain their heart rate and that the exercise is globally perceived as harder. Apnea did not induce an increase in lactatemia, probably related to the lack of modification of the muscle extraction of oxygen. At the cerebral level, the maintenance of the oxygenation would explain that the reaction time is not altered with apnea. Finally, all our studies revealed a significant arterial desaturation in apnea at the first repetition of the 10-second apnea (study 3) but without the effect of apnea capacity (study 1) or swimming intensity (study 2) suggesting that the duration would compensate for the intensity. It would therefore be interesting to study later the respective effects of the intensity/duration pair and the chronic effects of training involving intense intermittent exercise during dynamic apneas.

<p>Systemic infection, major surgery, trauma and many other causes can lead to impaired organ function. Compensated shock is not detected by global hemodynamic and oxygen measurements, as they take no account for regional variations. Focus has therefore gradually turned from looking at systemic changes to selective investigations of regional blood flow and ischemia. This thesis presents a series of experiments evaluating new application and validation of various monitoring techniques.</p><p>An experimental porcine model with anesthetized and invasively monitored animals was used. The circulatory interventions included endotoxin infusion (septic shock), aortic constriction and selective clamping of splanchnic arteries. The aim was to compare air with saline tonometry, to validate the intraperitoneal use of tonometry and to reexamine the use of endoluminal reflectance pulse oxymetry. To investigate the relative contributions of regional blood flow and detection of ischemia, measurements of hepatic venous oxygen saturation (ShvO₂), lactate concentrations and PCO₂ gap were used.</p><p>Our findings support the use of air instead of saline as the preferred technique for tonometric measurements. With the intraperitoneal application of tonometry we gain more information on regional aspects of the splanchnic circulation, and it appears to be a reliable monitoring option for early detection of ischemia in the small intestine. Measurements of ShvO₂will give an overall reflection of the intestinal circulation. The sigmoid colonic pulse oximetry showed a non-linear response in relation to regional blood flow, and will therefore not be able to detect gradual changes in oxygen saturation. Determination of the regional to endtidal PCO₂ gap might prove valuable for monitoring of the intestinal circulation.</p><p>Because of sophisticated interactions between portal and hepatic arterial blood flow and hepatic compensation for regional ischemia, a combination of monitoring techniques might be needed. The results of this study will hopefully encourage clinical evaluation of intraperitoneal tonometry and endtidal PCO₂ gap recordings for non-invasive, semi-continuous, trend monitoring of the splanchnic circulation.</p>