The diagnosis of obstructive sleep apnea (OSA) syndrome is overnight PSG (mutli-channel system). But it¡¦s hard to be popularized for the general population (about twenty channel signals). In recent decades, several researches were devoted to a replacement system with only one channel signal (oxyhemoglobin saturation). However, it¡¦s hard to match PSG system¡¦s report without EEG wake information. Consequently, two channels (oxyhemoglobin saturation and EEG) were used of this study to enhance the AHI (estimation index for sleep apnea) prediction performance. After surveying the most recent studies, this work proposes a new basleline removal technique for oxygen saturation signal (SpO2) by using median filter. It was proved this technique improves the diagnostic accuracy for OSA. Furthermore, it is also found that by removing the wake periods, diagnostic accuracy can be improved further. By counting the number of times that the desaturation level has dropped more than 2% for at least 3 seconds, the correlation coefficient between AHI and proposed feature is 0.9218. In addition, by removing the wake period, this correlation increases to 0.9425. By using this feature to classify patients with AHI value larger than 5, the proposed approach achieves 93.78% accuracy, 95.94% sensitivity, 78.87% specificity f. Such results demonstrate the feasibility of using single SpO2 channel system for OSA diagnosis.

The physiological signals of human are very important for the diagnosis of diseases. There are two different applications of physiological signals in this study. One is using oxyhemoglobin saturation to diagnose the obstructive sleep apnea hypopnea syndrome (OSAS); the other is to determine the association between dermatoglyphics and schizophrenia by using fingerprint asymmetry measures. The objective of the first part is to comprehensively evaluate the capablity and reliability of the previously proposed oxyhemoglobin indices derived automatically for predicting the severity of OSAS. Patients with a diagnosis of OSAS by standard polysomnography were recruited from China Medical University Hospital Sleep Center. The result revealed that when AHI cutoff value was set to 30/h, ODI achieves 87.8% sensitivity and 96.6% specificity. Another important finding is that, for both apnea and hypopnea, probability of oxyhemoglobin desaturation increases with increases of body mass index (BMI) and neck circumference (NC). Early detection and intervention strategies for schizophrenia are receiving increasingly more attention. Dermatoglyphic patterns have been hypothesized to be indirect measures for early abnormal developmental processes that can lead to later psychiatric disorders such as schizophrenia. However, previous results have been inconsistent in trying to establish the association between dermatoglyphics and schizophrenia. The goal of second part of this work is to try to resolve this problem by borrowing well developed techniques from the field of fingerprint matching. Fingerprint images were acquired digitally from 40 schizophrenic patients and 51 normal individuals. Based on these images, the sample means of the proposed measures consistently identified the patient group as having a higher degree of asymmetry than the control group.

Exercise-induced hypoxemia is a common observation in endurance-trained athletes. The present study examined the kinetics of oxyhemoglobin saturation during upright (UP) maximal cycling exercise in 84 healthy, untrained subjects between 8 and 26 years old. The prevalence of oxyhemoglobin desaturation (DS: SaO$ sb2 $ 0.05). A subgroup of children (n = 6) repeated the maximal exercise protocol in the supine (SU) position. In NDS values of SaO$ sb2$ were not affected by posture (UP: 95.3 $ pm$ 2.3 vs SU: 94.1 $ pm$ 0.9) for similar VO$ sb{ rm 2max}$ (UP: 3.7 $ pm$ 0.36 vs SU: 3.43 $ pm$ 0.36) (p $>$ 0.05). These observations suggest that exercise-induced DS is independent of age or training status. Differences due to posture may be related to variations in ventilatory and/or pulmonary perfusion parameters.

No description available.

A indução da anestesia no cão obeso é de grande desafio para o anestesista veterinário, pois estes pacientes apresentam alterações respiratórias e cardiovasculares. Além disso, há carência de protocolos anestésicos na literatura. Desta forma, objetivou-se comparar a indução da anestesia em cães obesos (escore corporal igual ou superior a 8) com propofol empregando-se a dose baseada no peso de massa magra ou baseada no peso total. Trinta e cinco cães foram distribuídos em três grupos: 13 cães de peso normal no grupo controle (GC); 15 cães obesos no grupo peso total (GPT) e sete cães obesos no grupo peso de massa magra (GPMM). Todos os cães foram avaliados com auxílio de escala escore de condição corporal (ECC) de 9 pontos e também tiveram a composição de condição corporal determinada por meio do método de diluição de isótopos de deutério. A anestesia foi induzida com 150 mg/kg/h com auxílio de bomba de infusão de propofol até os animais perderem a consciência. Os animais do GPT receberam a infusão de propofol baseado no peso total; os animais do GPMM receberam infusão de propofol baseado no peso de massa magra; e os cães do GC receberam propofol baseado no peso total. Os parâmetros fisiológicos como frequência cardíaca, pressão arterial sistêmica, saturação de oxi-hemoglobina e presença de apneia foram registrados antes e após a indução. A dose empregada de propofol foi 10,7 ± 2,8mg/kg, 14,1 ± 4,7mg/kg e 7,6 ± 1,5mg/kg nos grupos GC, GPMM e GPT, respectivamente, sendo a diferença significante (p<0,001). Na comparação entre os diferentes momentos dentro de cada grupos, observou-se diferença significativa no GC em relação à PAS, onde os valores obtidos após a indução da anestesia (150,8 ± 32,2mmHg) foram menores do que o basal (180,0 ± 34,8mmHg) (p=0,048). No grupo GPMM observou-se diferença na PAD, sendo que os valores basais (103,6 ± 29,1mmHg) foram mais elevados do que após a indução anestésica (79,3 ± 22,8) (p=0,018). Em relação a oxi-hemoglobina periférica houve diferença significativa entre os valores basais e os obtidos após indução da anestesia em todos os grupos sendo. p=0,027, p=0,006 e p=<0,001, respectivamente nos grupos GC, GPMM e GPT. O presente estudo demonstrou que cães obesos requerem dose menor de propofol (7,6 ± 1,5mg/kg) na indução da anestesia em relação aos cães com peso normal (10,7 ± 2,8mg/kg) ao serem anestesiados com a dose baseada no peso total. Não foi possível demostrar que cães obesos que tiveram a dose calculada baseada apenas no peso de massa magra (14,1 ± 4,7mg/kg) necessitem de doses similares a de cães com peso normal com o calculo baseado no peso total (10,7 ± 2,8mg/kg) / The anesthesia induction of the obese dog poses a great challenge to the veterinary anesthesiologist since these patients present respiratory and cardiovasvular alterations. Besides that, there is little information on anesthetic protocols in the literature. Therefore, the objective was to compare the anesthesia induction in obese dogs (body score condicional equal to or greater than 8) using propofol in dosages based on lean body weight or total body weight. Thirty-five dogs were distributed in three groups: 13 dogs with average weight in the control group (CG); 15 obese dogs in total body weight group (TBWG) and seven obese dogs in lean body weight group (LBWG). All dogs were evaluated according to a body condition score chart (BCS) of 9 points and also had their body composition determined using the deuterium dilution method. Anesthesia was inducted with 150 mg/kg/h through a propofol infusion pump until animals lost consciousness. Animals in TBWG received propofol infusion based on total body weight; the animals in LBWG received propofol infusion based on lean body mass, and the dogs in CG received propofol infusion based on total body weight. Physiological parameters such as heart rate, systemic arterial pressure, oxyhemoglobin saturation and the presence of apnea were recorded previous to and post induction. Propofol dose used was 10.7 ± 2.8mg/kg, 14.1 ± 4.7mg/kg and 7.6 ± 1.5mg/kg in groups CG, LBWG and TBWG, respectively, with a significant difference (p<0.001). Comparing different moments within each group, there was a significant difference in GC related to SAP, where values obtained post induction (150.8 ± 32.2) were smaller than basal (180 ± 34.8) (p=0.048). In LBWG there was a difference in DAP, where basal values (103.6 ± 29.1) were higher than post induction (79.3 ± 22.8) (p=0.018). There were significant differences in peripheral oxyhemoglobin saturation between basal values and post anesthesia induction values in all groups with p=0.027, p=0.006 and p<0.001 in CG, LBWG and TBWG, respectively. The current study shows that obese dogs require smaller propofol doses (7.6 ± 1.5mg/kg) than average weight dogs (10.7 ± 2.8mg/kg) when induction anesthesia based on total body weight dosage. It was not possible to demonstrate that obese dogs with doses based on lean body mass (14.1 ± 4.7mg/kg) have propofol dosage needs similar to average weight dogs with dosage based on total body weight (10.7 ± 2.8mg/kg)

A indução da anestesia no cão obeso é de grande desafio para o anestesista veterinário, pois estes pacientes apresentam alterações respiratórias e cardiovasculares. Além disso, há carência de protocolos anestésicos na literatura. Desta forma, objetivou-se comparar a indução da anestesia em cães obesos (escore corporal igual ou superior a 8) com propofol empregando-se a dose baseada no peso de massa magra ou baseada no peso total. Trinta e cinco cães foram distribuídos em três grupos: 13 cães de peso normal no grupo controle (GC); 15 cães obesos no grupo peso total (GPT) e sete cães obesos no grupo peso de massa magra (GPMM). Todos os cães foram avaliados com auxílio de escala escore de condição corporal (ECC) de 9 pontos e também tiveram a composição de condição corporal determinada por meio do método de diluição de isótopos de deutério. A anestesia foi induzida com 150 mg/kg/h com auxílio de bomba de infusão de propofol até os animais perderem a consciência. Os animais do GPT receberam a infusão de propofol baseado no peso total; os animais do GPMM receberam infusão de propofol baseado no peso de massa magra; e os cães do GC receberam propofol baseado no peso total. Os parâmetros fisiológicos como frequência cardíaca, pressão arterial sistêmica, saturação de oxi-hemoglobina e presença de apneia foram registrados antes e após a indução. A dose empregada de propofol foi 10,7 ± 2,8mg/kg, 14,1 ± 4,7mg/kg e 7,6 ± 1,5mg/kg nos grupos GC, GPMM e GPT, respectivamente, sendo a diferença significante (p<0,001). Na comparação entre os diferentes momentos dentro de cada grupos, observou-se diferença significativa no GC em relação à PAS, onde os valores obtidos após a indução da anestesia (150,8 ± 32,2mmHg) foram menores do que o basal (180,0 ± 34,8mmHg) (p=0,048). No grupo GPMM observou-se diferença na PAD, sendo que os valores basais (103,6 ± 29,1mmHg) foram mais elevados do que após a indução anestésica (79,3 ± 22,8) (p=0,018). Em relação a oxi-hemoglobina periférica houve diferença significativa entre os valores basais e os obtidos após indução da anestesia em todos os grupos sendo. p=0,027, p=0,006 e p=<0,001, respectivamente nos grupos GC, GPMM e GPT. O presente estudo demonstrou que cães obesos requerem dose menor de propofol (7,6 ± 1,5mg/kg) na indução da anestesia em relação aos cães com peso normal (10,7 ± 2,8mg/kg) ao serem anestesiados com a dose baseada no peso total. Não foi possível demostrar que cães obesos que tiveram a dose calculada baseada apenas no peso de massa magra (14,1 ± 4,7mg/kg) necessitem de doses similares a de cães com peso normal com o calculo baseado no peso total (10,7 ± 2,8mg/kg) / The anesthesia induction of the obese dog poses a great challenge to the veterinary anesthesiologist since these patients present respiratory and cardiovasvular alterations. Besides that, there is little information on anesthetic protocols in the literature. Therefore, the objective was to compare the anesthesia induction in obese dogs (body score condicional equal to or greater than 8) using propofol in dosages based on lean body weight or total body weight. Thirty-five dogs were distributed in three groups: 13 dogs with average weight in the control group (CG); 15 obese dogs in total body weight group (TBWG) and seven obese dogs in lean body weight group (LBWG). All dogs were evaluated according to a body condition score chart (BCS) of 9 points and also had their body composition determined using the deuterium dilution method. Anesthesia was inducted with 150 mg/kg/h through a propofol infusion pump until animals lost consciousness. Animals in TBWG received propofol infusion based on total body weight; the animals in LBWG received propofol infusion based on lean body mass, and the dogs in CG received propofol infusion based on total body weight. Physiological parameters such as heart rate, systemic arterial pressure, oxyhemoglobin saturation and the presence of apnea were recorded previous to and post induction. Propofol dose used was 10.7 ± 2.8mg/kg, 14.1 ± 4.7mg/kg and 7.6 ± 1.5mg/kg in groups CG, LBWG and TBWG, respectively, with a significant difference (p<0.001). Comparing different moments within each group, there was a significant difference in GC related to SAP, where values obtained post induction (150.8 ± 32.2) were smaller than basal (180 ± 34.8) (p=0.048). In LBWG there was a difference in DAP, where basal values (103.6 ± 29.1) were higher than post induction (79.3 ± 22.8) (p=0.018). There were significant differences in peripheral oxyhemoglobin saturation between basal values and post anesthesia induction values in all groups with p=0.027, p=0.006 and p<0.001 in CG, LBWG and TBWG, respectively. The current study shows that obese dogs require smaller propofol doses (7.6 ± 1.5mg/kg) than average weight dogs (10.7 ± 2.8mg/kg) when induction anesthesia based on total body weight dosage. It was not possible to demonstrate that obese dogs with doses based on lean body mass (14.1 ± 4.7mg/kg) have propofol dosage needs similar to average weight dogs with dosage based on total body weight (10.7 ± 2.8mg/kg)

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.

Il est connu qu’on retrouve chez les femmes en post-ménopause un risque plus important de développer des maladies oculaires comparativement aux hommes du même groupe d’âge. Il semble que les changements hormonaux, et en particulier la baisse importante des niveaux d’estradiol, secondaires à la sénescence folliculaire constituent un facteur étiologique à long terme. Cela étant, il est légitime de se demander si les variations des niveaux d’hormones sexuelles endogènes peuvent également occasionner des effets à court terme sur les tissus de l’œil. Cette interrogation constitue d’ailleurs le motif principal de l’élaboration de la présente étude. Sachant qu’il se produit chez les femmes non ménopausées des variations continuelles des niveaux d’hormones sexuelles stéroïdiennes au cours de leur cycle menstruel, des femmes en âge de procréer ont été recrutées comme sujets d’étude. Dans un deuxième temps, afin de trouver le paramètre d’intérêt, on a effectué une revue de la documentation scientifique qui révèle un fait bien établi : les estrogènes favorisent la vasodilatation des vaisseaux sanguins par l’intermédiaire du monoxyde d’azote, et permettent, par le fait même, l’accroissement du débit sanguin tissulaire. Or, comment mesurer des variations de débit sanguin dans des tissus oculaires? Comme il est expliqué dans la discussion du présent mémoire, les variations d’oxygénation dans un organe dont le métabolisme est relativement stable sont le reflet de variations de débit sanguin. Grâce à une technique de mesure basée sur la spectroréflectométrie, il est possible de mesurer le taux d’oxyhémoglobine (HbO2) des lits capillaires du disque optique. En observant les variations du taux d’oxyhémoglobine au cours du cycle menstruel chez les sujets, on peut ainsi mesurer l’effet des variations hormonales cycliques sur l’irrigation des tissus oculaires. En somme, l’objectif de cette recherche est de mieux comprendre, en suivant le cycle menstruel des femmes, l’effet des hormones sexuelles endogènes sur l’oxygénation des lits capillaires du disque optique. Étant à la base du métabolisme de l’œil, l’apport en oxygène et en divers substrat véhiculés par la circulation sanguine est important au maintien de la santé oculaire. L’éclaircissement du lien entre les hormones et l’oxygénation de la rétine constituerait un avancement important, puisqu’il permettrait de comprendre pourquoi certaines atteintes oculaires, comme la cécité, touchent davantage les femmes. Les résultats de cette étude ont démontré que le taux d’oxyhémoglobine mesuré dans les lits capillaires du disque optique de l’œil ne subit pratiquement pas de variations significatives durant le cycle menstruel lorsqu’on considère les incertitudes des valeurs mesurées. Également, on observe une variabilité similaire des taux d’oxyhémoglobine mesurés chez les femmes en âge de procréation et chez les hommes du même groupe d’âge. Cela suggère que les changements hormonaux cycliques, qui ne se produisent que chez les femmes, n’occasionnent probablement pas de variation significative mesurable du taux d’oxyhémoglobine. Bref, malgré les effets possibles des estrogènes sur le diamètre artériolaire, il semble que les mécanismes locaux de régulation du débit sanguin tissulaire maintiennent un état d’équilibre propre au tissu irrigué et adapté aux besoins métaboliques locaux. / Postmenopausal women, when compared to men from the same age group, are more prone to develop ocular disease. It is thought that long term hormonal changes caused by ovarian senescence, and especially the drop in estradiol, are the etiological mechanism by which this phenomenon occurs. Whether variations in the levels of endogenous sexual hormones can produce short term effects in the tissues of the eye is less understood and, therefore, constitutes the main reason for carrying out the present study. Given that non menopausal women have repeated short term changes in the levels of sex steroid hormones during their menstrual cycle, we have recruited such women as study subjects. We also reviewed the scientific literature to establish what would be the parameter of interest and found a well characterised phenomenon: estrogens promote vasodilation by increasing nitrogen oxide production and thus promote a rise in blood flow. As to measuring variations in blood flow within the eye, it was explained in the discussion of the present memoir that changes in the oxygenation of an organ with a constant metabolism are induced by changes in the blood flow irrigating that organ. Using a method based on spectroreflectometry, it is possible to measure oxyhaemoglobin levels (HbO2) in the capillaries of the optic disc. By studying the variation of the HbO2 levels during the menstrual cycle, we can appreciate the effect of the cyclic hormonal changes on the ocular blood flow. The supply in oxygen and nutrients brought to an organ by its blood flow is essential for its metabolism. Therefore, the discovery of a correlation between sex hormone levels and the oxygenation of the retina would prove to be an important step towards understanding the higher frequency of certain ocular diseases in postmenopausal women, as compared to men of the same age group. The results of our study show that HbO2 levels in the capillary beds of the optic disc do not undergo statistically significant variations during the menstrual cycle. The same results were found, during a similar observational period, for male subjects used in the study as controls. These results suggest that cyclic variations in the levels of sex hormones, which occur only in nonmenaopausal women, do not induce significant changes in the oxygenation of the optic disc. In short, despite the possible effect of estrogens on the arteriolar diameter, it seems that local regulatory mechanisms of the blood flow maintain a tissue in a state of equilibrium that is adapted to its specific metabolic demand.

Il est connu qu’on retrouve chez les femmes en post-ménopause un risque plus important de développer des maladies oculaires comparativement aux hommes du même groupe d’âge. Il semble que les changements hormonaux, et en particulier la baisse importante des niveaux d’estradiol, secondaires à la sénescence folliculaire constituent un facteur étiologique à long terme. Cela étant, il est légitime de se demander si les variations des niveaux d’hormones sexuelles endogènes peuvent également occasionner des effets à court terme sur les tissus de l’œil. Cette interrogation constitue d’ailleurs le motif principal de l’élaboration de la présente étude. Sachant qu’il se produit chez les femmes non ménopausées des variations continuelles des niveaux d’hormones sexuelles stéroïdiennes au cours de leur cycle menstruel, des femmes en âge de procréer ont été recrutées comme sujets d’étude. Dans un deuxième temps, afin de trouver le paramètre d’intérêt, on a effectué une revue de la documentation scientifique qui révèle un fait bien établi : les estrogènes favorisent la vasodilatation des vaisseaux sanguins par l’intermédiaire du monoxyde d’azote, et permettent, par le fait même, l’accroissement du débit sanguin tissulaire. Or, comment mesurer des variations de débit sanguin dans des tissus oculaires? Comme il est expliqué dans la discussion du présent mémoire, les variations d’oxygénation dans un organe dont le métabolisme est relativement stable sont le reflet de variations de débit sanguin. Grâce à une technique de mesure basée sur la spectroréflectométrie, il est possible de mesurer le taux d’oxyhémoglobine (HbO2) des lits capillaires du disque optique. En observant les variations du taux d’oxyhémoglobine au cours du cycle menstruel chez les sujets, on peut ainsi mesurer l’effet des variations hormonales cycliques sur l’irrigation des tissus oculaires. En somme, l’objectif de cette recherche est de mieux comprendre, en suivant le cycle menstruel des femmes, l’effet des hormones sexuelles endogènes sur l’oxygénation des lits capillaires du disque optique. Étant à la base du métabolisme de l’œil, l’apport en oxygène et en divers substrat véhiculés par la circulation sanguine est important au maintien de la santé oculaire. L’éclaircissement du lien entre les hormones et l’oxygénation de la rétine constituerait un avancement important, puisqu’il permettrait de comprendre pourquoi certaines atteintes oculaires, comme la cécité, touchent davantage les femmes. Les résultats de cette étude ont démontré que le taux d’oxyhémoglobine mesuré dans les lits capillaires du disque optique de l’œil ne subit pratiquement pas de variations significatives durant le cycle menstruel lorsqu’on considère les incertitudes des valeurs mesurées. Également, on observe une variabilité similaire des taux d’oxyhémoglobine mesurés chez les femmes en âge de procréation et chez les hommes du même groupe d’âge. Cela suggère que les changements hormonaux cycliques, qui ne se produisent que chez les femmes, n’occasionnent probablement pas de variation significative mesurable du taux d’oxyhémoglobine. Bref, malgré les effets possibles des estrogènes sur le diamètre artériolaire, il semble que les mécanismes locaux de régulation du débit sanguin tissulaire maintiennent un état d’équilibre propre au tissu irrigué et adapté aux besoins métaboliques locaux. / Postmenopausal women, when compared to men from the same age group, are more prone to develop ocular disease. It is thought that long term hormonal changes caused by ovarian senescence, and especially the drop in estradiol, are the etiological mechanism by which this phenomenon occurs. Whether variations in the levels of endogenous sexual hormones can produce short term effects in the tissues of the eye is less understood and, therefore, constitutes the main reason for carrying out the present study. Given that non menopausal women have repeated short term changes in the levels of sex steroid hormones during their menstrual cycle, we have recruited such women as study subjects. We also reviewed the scientific literature to establish what would be the parameter of interest and found a well characterised phenomenon: estrogens promote vasodilation by increasing nitrogen oxide production and thus promote a rise in blood flow. As to measuring variations in blood flow within the eye, it was explained in the discussion of the present memoir that changes in the oxygenation of an organ with a constant metabolism are induced by changes in the blood flow irrigating that organ. Using a method based on spectroreflectometry, it is possible to measure oxyhaemoglobin levels (HbO2) in the capillaries of the optic disc. By studying the variation of the HbO2 levels during the menstrual cycle, we can appreciate the effect of the cyclic hormonal changes on the ocular blood flow. The supply in oxygen and nutrients brought to an organ by its blood flow is essential for its metabolism. Therefore, the discovery of a correlation between sex hormone levels and the oxygenation of the retina would prove to be an important step towards understanding the higher frequency of certain ocular diseases in postmenopausal women, as compared to men of the same age group. The results of our study show that HbO2 levels in the capillary beds of the optic disc do not undergo statistically significant variations during the menstrual cycle. The same results were found, during a similar observational period, for male subjects used in the study as controls. These results suggest that cyclic variations in the levels of sex hormones, which occur only in nonmenaopausal women, do not induce significant changes in the oxygenation of the optic disc. In short, despite the possible effect of estrogens on the arteriolar diameter, it seems that local regulatory mechanisms of the blood flow maintain a tissue in a state of equilibrium that is adapted to its specific metabolic demand.

This master´s thesis deals with processing and analysis of data, acquired from experimental examination performed with functional magnetic resonance imaging technique. It is an oddball type experimental task and its goal is an examination of cognitive functions of the subject. The principles of functional magnetic resonance imaging, possibilities of experimental design, processing of acquired data, modeling of a response of organism and statistical analysis are described in this work. Furthermore, particular parts of preprocessing and analysis are carried out using real data set from experiment. The main goal of this work is suggestion and realization of model, which enables advanced categorization of stimuli, considering the type of previous rare stimulus and the number of frequent stimuli within them. With its in-depth categorization, this model enables detail exploration of cerebral processes, associated mainly with attention, memory, expectancy or cognitive closure. The second point of that work is an evaluation of models of hemodynamic response, which are applied in statistical analysis of data from fMRI experiment. Comparison of basis functions, the models of hemodynamic response to experimental stimulation used for general linear model, is performed in this work. The result of this comparison is an evaluation of detection efficiency of activated voxels, false positivity rate and computational and user difficulty.