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The objective of the thesis was to evaluate the possibility to calculate the unloading distribution between a ventilator and a patient using a new mathematical modelling of the breathing patterns. The modelling used today is considered to lack sufficient precision for clinical use, and is a somewhat simplified model. To evaluate the possibility of a new model, a volunteer test was carried out - recording data such as Edi, pressure, volume and flow. Using this data, and by using a more complex model, tidal volume was estimated and compared to the measured data. The results did not imply any improvement compared to the simpler model regarding the accuracy and the variability. However, more work should be done in this area, as time deficiency prevented further analysis.

Les ventilateurs ont connu des progrès technologiques considérables grâce à l'application de concepts physiologiques, à l'électronique, à l'informatique et la miniaturisation. Leurs conceptions et performances intrinsèques, en revanche, ont pu rester inégales sur certains points. L'objectif de ce travail a été d'évaluer sur un banc d'essai, avec un protocole, adapté aux problématiques soulevées en pratique clinique, tous les ventilateurs de réanimation, transport et de ventilation non invasive de façon rigoureuse et reproductible. Les résultats montrent que 1) l'erreur sur le volume réellement délivré est très fréquente et correspond facilement à 1ml/kg de volume supplémentaire ; le VT indiqué sur les ventilateurs est inférieur au VT réellement délivré ; 2) les performances des nouveaux ventilateurs ne présentent pas d'améliorations significatives par rapport aux meilleurs ventilateurs testés en 2000; les ventilateurs à turbine sont identiques ou proches des meilleurs ventilateurs conventionnels ; 3) les ventilateurs dédiés à la ventilation non invasive montrent de meilleures performances pour s'adapter à la présence de fuites ; 4) la ventilation par percussion intra-pulmonaire superposée à la ventilation conventionnelle peut réduire l'apport de l'humidification, influencer les volumes administrés et induire une pression expiratoire positive intrinsèque. Les tests sur banc montrent une grande hétérogénéité des performances. Une veille technologique semble indispensable pour évaluer tout nouveau ventilateur / The ventilators have markedly improved thanks to progress in respiratory physiology, in informatics and miniaturization. However, their intrinsic performances remain unequal. The aim was to evaluate ventilators performances on reproducible bench test studies adapted to clinical questions. Tests show that 1) the error of really delivered volume is approximately 1 ml/kg of additional volume; the tidal volume (VT) indicated on the ventilators was lower than the real delivered VT ; 2) Performances of new ventilators are comparable to the best ventilators tested in 2000 ; turbine ventilators are quite similar to best conventional ventilators ; 3) The ventilators dedicated to non invasive ventilation showed better performances to cope with leaks 4) The intrapulmonary percussive ventilation superimposed on conventional ventilation can reduce humidity, increase volumes and can generate intrinsic positive expiratory pressure. The bench tests showed a large heterogeneity of performances. A technological watch seems essential to evaluate all new ventilators

Heart disease is a major cause of morbidity and mortality in the United States with coronary artery disease (CAD) representing more than half of all cardiovascular events. Stable patients presenting with symptoms suggestive of CAD are likely to undergo either an exercise ECG and/or imaging study as a first line diagnostic assessment. A cardiopulmonary exercise test (CPX) is an ECG stress test plus ventilatory gas analysis. Recently CPX has been used to detect exercise-induced myocardial ischemia suggestive of underlying CAD. Currently there are a number of diagnostic tests available for the identification of CAD with the most widely used being exercise ECG, myocardial perfusion imaging (MPI) and cardiac catheterization. Exercise ECG, although inexpensive, has a number of well-recognized limitations, including low sensitivity resulting in false positive results. MPI and catheterization are more accurate but also more invasive and expensive. It appears that CPX may improve the diagnostic accuracy of exercise ECG in a cost effective manner.

The assessment of ventilatory efficiency (VE/VCO2 slope) is increasingly being utilized to complement traditional cardiorespiratory fitness testing during graded exercise. The purpose of this study was to compare cardiorespiratory responses and ventilatory efficiency in obese children during a progressive exercise test to volitional fatigue performed on a treadmill and a cycle ergometer. Fifteen obese male (N=3) and female (N=12) adolescents aged 10 to 18 years were recruited in the study and completed both the treadmill and cycle ergometer trials. Mean age and BMI of the sample was 13.3 years and 38.0 kg/m2, respectively. Maximal oxygen consumption (VO2max) and ventilatory efficiency were determined during both exercise trials. Subsequently, overall VE/VCO2 slope and the slope below and above AT for ventilatory efficiency were compared between the two exercise modes. VO2max was significantly (p<0.05) greater during the treadmill trial (26.09±5.11 ml/kg/min) compared to the cycle ergometer trial (20.71± 4.31 ml/kg/min). The VO2 at anaerobic threshold (AT) was significantly (p<0.05) higher during the treadmill trial, however, the percentage of VO2max at AT was not significantly different between the two modes (treadmill-63.41± 6.29% and cycle ergometer (67.25± 6.99%). While there was no significant difference in the overall VE/VCO2 slope or the VE/VCO2 slope above anaerobic threshold obtained from the two modes, the VE/VCO2 slope below anaerobic threshold was significantly (p<0.05) higher in the treadmill trial (25.06±2.10) compared to the cycle ergometer trial (23.34± 2.12). In our small sample of obese adolescents, we observed a greater VE response for a given VCO2 during treadmill exercise below the anaerobic threshold. The differences observed may be related to a greater activation of muscle afferents during weight bearing exercise in obese adolescents.

Master of Science / Department of Clinical Sciences / Rose M. McMurphy / Hypoventilation (PaCO2 > 45 mmHg) and large P(A-a)O2 gradients due to V/Q mismatch and shunt, are common during isoflurane anesthesia in horses. A fraction of inspired oxygen < 50% has been shown to improve ventilation and decrease intra-operative atelectasis in humans and some animals. The study compared the effects of two different fractions of inspired oxygen, 50% versus > 95%, on ventilation, respiratory pattern, and P(A-a)O2 gradient in isoflurane anesthetized horses. Eight mature horses were sedated with IV xylazine (1.0 mg/kg) and anesthetized with diazepam (0.05 mg/kg) and ketamine (2.2 mg/kg) twice. Anesthesia was maintained with isoflurane (ET1.5 vol%) in either 50 or > 95% oxygen for 90 minutes. Both treatments were randomly assigned to each horse with a one week interval in between treatments. Horses were positioned in dorsal recumbency, connected to a preloaded circle breathing system and allowed to spontaneously ventilate. Measurements included inspiratory and expiratory peak flow and time, tidal volume, respiratory frequency, ETCO2, CO2, O2, PaO2, PaCO2, pH, SaO2, heart rate, and arterial blood pressure. Calculated values included PAO2, P(A-a)O2, P(A-a)O2 rate of change, and physiologic dead space. FiO2 of 50% resulted in a lower PaO2, SaO2, PAO2, and P(A-a)O2. No significant change in PaCO2, ventilatory pattern, or any remaining measured variables was observed (p<0.05). The use of 50% oxygen and nitrogen as the carrier gas did not significantly change the ventilatory characteristics or improve oxygenation in isoflurane anesthetized horses. Repeatable respiratory rhythms characteristics were observed for horses while inspiring 50% and > 95% oxygen. A high A-a oxygen gradient with an equal rate of change overtime was still observed during both treatments.

O consumo máximo de oxigênio (VO2máx), o limiar ventilatório (LV), ponto de compensação respiratória (PCR) e a economia de corrida (EC) são importantes variáveis fisiológicas associadas com a aptidão aeróbia em corrida. Acredita-se que o polimorfismo da enzima conversora de angiotensina (ECA) possa estar influenciando nos valores dessas variáveis. Contudo, essa relação causal não tem sido amplamente estudada durante a corrida. Dessa forma, o objetivo do presente trabalho foi investigar a associação entre os genótipos da ECA e o VO2máx, LV, PCR e EC mensuradas durante a corrida em esteira. Cento e cinquenta (n = 150) voluntários fisicamente ativos realizaram os seguintes testes: a) teste incremental máximo para determinação do VO2máx, LV e PCR; b) dois testes de velocidade constante (10 km/h e 12 km/h) em esteira para determinação da EC. Os genótipos apresentaram a frequência de: II = 21% ; ID = 52% e DD = 27%. Os resultados apresentaram uma tendência dos indivíduos com o genótipo II apresentarem maiores valores do VO2máx (p = 0.08), bem como a análise do efeito prático apresentou um possível efeito benéfico desse genótipo. No entanto, não foi constatada diferença entre os valores do LV, PCR, e EC entre os indivíduos. Esses resultados sugerem que o genótipo II da ECA pode estar influenciando nos valores da variável máxima relacionada com o consumo de oxigênio / The maximal oxygen uptake (VO2máx), ventilatory threshold (VT), respiratory compensation point (RCP), and running economy (RE) are important variables associated with running aerobic fitness. However, the influence of Angiotensin Converting Enzyme (ACE) polymorphism on these variables determined in running has not been largely investigated. Therefore, the present study aimed to investigate the relationship between ACE genotypes and maximal oxygen uptake, respiratory compensation point, and running economy measured in running. One hundred and fifty (n = 150) physically active young men performed the following tests: a) a maximal incremental treadmill test to determine VO2máx and RCP, b) two constant-speed running test (10 km.h-1 and 12 km.h-1) to determine the RE. The genotype frequency were II = 21 %; ID = 52 %; DD = 27 %. There were a likely beneficial effect and a tendency for the participants with ACE II genotype to have higher VO2max values than DD or ID genotypes (p = 0.08) and the smallest worthwhile effects show a beneficial effect. There were not associations between the genotypes for RCP and RE. These findings suggest that II ACE genotype would influence in maximal variable correlated with oxygen consumption

Os avanços tecnológicos ocorridos na última década trouxeram enormes benefícios, no sentido de possibilitar o uso de equipamentos computadorizados, que permitem a aquisição, processamento e armazenamento de um grande número de variáveis respiratórias e metabólicas em exercício físico, em tempo real e de ciclo a ciclo respiratório. Dentro deste novo cenário, o estudo realizado com esta nova geração de equipamentos, nas respectivas áreas de conhecimento, pôde ser direcionado, usando-se métodos matemáticos e estatísticos computadorizados, os quais possibilitam a aplicação de procedimentos automáticos e/ou semi-automáticos na solução de problemas específicos. É dentro deste contexto que se insere o presente estudo, que tem por objetivo comparar, em indivíduos sadios do sexo masculino, o limiar de anaerobiose ventilatório, durante o exercício físico dinâmico, usando-se métodos visuais gráficos e métodos baseados em modelos matemáticos, automáticos e semi-automáticos. Foram estudados 24 voluntários sadios do sexo masculino, com idade média de 33,8 ± 9,25 anos. Todos eles se submeteram a um ou dois testes de esforço físico dinâmico, segundo um protocolo contínuo do tipo rampa, na posição sentada, em cicloergômetro eletromagnético, acoplado a um sistema ergoespirométrico computadorizado (CPX/D – MedGraphics), que possibilita o cálculo de múltiplas variáveis cardiorrespiratórias, como: ventilação pulmonar (VE), produção de CO2 (VCO2), consumo de O2 (VO2), equivalentes ventilatórios de O2 (VE/VO2) e de CO2 (VE/VCO2), frações parciais do O2 (PETO2) e do CO2 (PETCO2) no final da expiração, quociente de trocas respiratórias (RER), freqüências respiratória (RR) e cardíaca (FC), além dos valores de potência aplicada e da velocidade de pedalagem no cicloergômetro. Os valores do LAV em exercício foram calculados por quatro diferentes métodos, que usam como critério de medida deste parâmetro, a mudança de inclinação da VCO2, da VE e do PET O2 em relação ao tempo ou da VCO2 em relação ao VO2. Estes métodos foram os seguintes: 1- método Visual VCO2 (M. VISUAL VCO2); 2- método Visual PET O2 (M. VISUAL PET O2); 3- método Automático, usando algoritmo, incorporado ao sistema MedGraphics (M. AUTOMÁTICO); 4- método semi-automático, implementado em nosso Laboratório, baseado no uso de modelos bissegmentados Linear-Linear (M. L-L VCO2) e Linear-Quadrático (M. L-Q VCO2) na condição de resposta da VCO2 em relação ao tempo e em relação ao VO2 (M. L-L VCO2 - VO2 e M. L-Q VCO2 - VO2). Os modelos bissegmentados se basearam na aplicação da soma dos quadrados dos resíduos, quando o conjunto de dados é ajustado pelo método dos mínimos quadrados, para uma reta inicial e final ou uma reta inicial e uma curva quadrática final. Após análise qualitativa e quantitativa apropriada ao conjunto de dados, chegou-se às seguintes conclusões: 1- os valores de LAV calculados pelos métodos visuais VCO2 e PET O2 foram significativamente superiores (p<0,05) aos obtidos pelos métodos Automático e L-L VCO2; 2- o método Visual VCO2 mostrou melhor desempenho do que o método Visual PET O2; 3- os valores do LAV calculados pelos métodos Automático e L-L VCO2 não foram estatisticamente diferentes e ambos subestimaram os valores do LAV, comparativamente aos métodos visuais VCO2 e PET O2 (p<0,05); 4- os métodos baseados em modelos bissegmentados L-L e L-Q mostraram que somente o M. L-L, para o caso da resposta da VCO2 em relação ao tempo, foi útil para medir quantitativamente o LAV; 5- o método semi-automático bissegmentar L-L VCO2 mostrou melhor desempenho do que o método Automático, quando ambos foram comparados qualitativa e quantitativamente (maior porcentagem de casos em que foi possível aplicar o modelo e melhor comportamento dos parâmetros das regressões lineares do LAV, relacionando potência e VO2); 6- o método semi-automático bissegmentar L-L VCO2 se mostrou promissor, no sentido de que possa ser aprimorado e usado, em futuro próximo, como método totalmente automático de determinação do limiar de anaerobiose ventilatório durante o exercício físico dinâmico. / The technological achievements in last decade made possible to use in laboratory facilities digital computerized equipments that allowed the acquisition, storage ande processing of cardiorespiratory variables during exercise on real time basis. Also, as a consequence of these advances, it was possible to apply mathematical models to represent physiological responses under experimental conditions. The present study must be understood in the context above described. It had the the purpose to compare the ventilatory anaerobic threshold (VAT) during dynamic exercise, by four different methods. Two of them are based on visual analyses made on graphic plots of computer monitor, and two others are based on application of mathematical models. Twenty four active and sedentary healthy men were studied in the present project (mean age 33.8 ± 9.2 years). All of them were studied in seated position using an electronic braked cycle ergometer (CORIVAL 400 – Quinton), that allowed the application of ramp powers using a computer software incorporated to the ergoespirometric system (MedGraphics – CPX/D). This system allowed the recording and processing of all cardiorespiratory variables usually needed in exercise physiology, as follow: O2 uptake (VO2), CO2 production (VCO2), minute respiratory ventilation (VE), respiratory equivalent ratio (RER), VE/VO2, VE/VCO2, and end tidal expiratory values of O2 (PET O2) and CO2 (PET CO2), as well as, power and rotation speed cycle ergometer values. The exercise protocol included a four minute period at a minimum power (3 - 4 Watts) followed by a ramp (15 – 35 Watts) adjustable individually on the basis of sex, age and weight of volunteers – the peak power was limited by the occurrence of unpleasant symptons or when the heart rate reached a target age value. The VAT values during exercise were measured by using four different methods: 1- visual loss of linearity related to time (VCO2 VIS. M.); 2- visual response of PET O2 at lowest value before the progressive increase in exercise; 3- automatic detection using MedGraphics algorithm; 4- semiautomatic method using bisegmentar mathematical models (Linear-Linear and Linear-Quadratic) applied to VCO2 and VE in relation to time (VCO2 L-L M.; VCO2 L-Q M.; VE L-L M.; VE L-Q M.) and to VCO2 in relation to VO2 during exercise (VCO2 vs. VO2 L-L M.; VCO2 vs. VO2 L-Q M.). The bisegmentar models were based on the measure of the square sum of residual values related to fitting of two functions, Linear-Linear and Linear-Quadratic, appling the least-square method. After qualitative and quantitative analyses of data, it was possible to reach to the following conclusions: 1- the VAT values measured by VCO2 and PET O2 visual methods were higher (p<0.05) than the ones obtained by Automatic and semi automatic methods; 2- the Visual VCO2 compared to PET O2 method, presented a better performance when VO2 and power values are represented by regression lines; 3- the VAT values obtained by Automatic and semiautomatic methods were not statistically different and have shown lower values when compared to visual methods (VCO2 and PET O2); 4- comparing the performance of the all bisegmentar methods tested, only the VCO2 L-L related to time was useful for measuring the VAT; 5- compared to Automatic method, the VCO2 L-L method could be applied in higher percentage of cases and presented parameters of regression lines (inclination and intercept) closer to visual methods; 6- the semiautomatic method applied to the response VCO2 in relation to time has shown a promising method that if fully automatic may be useful to calculate VAT in men.

Background: Children with complex congenital heart disease (CHD) are exposed to cyanosis from birth until their surgical repair and are often not expected to participate in physical activities to the same extent as healthy peers because of a limited maximal exercise capacity (V̇O2max). Despite limitations in V̇O2max, these children may still have the capacity to perform most daily physical activity because it requires only a submaximal effort. The purpose of this research was to examine the relationships between submaximal exercise capacity, daily physical activity and cyanosis exposure, in children with complex CHD. Methods: Children with a single functioning ventricle (Fontan), tetralogy of Fallot or transposition of the great arteries, 10 to 17 years old were deemed eligible. The Bruce treadmill protocol with breath-by-breath analysis of oxygen consumption was used to assess submaximal exercise capacity. Five measures of submaximal exercise capacity were evaluated: energy consumption (V̇O2) at the ventilatory threshold, V̇O2 at a heart rate of 130 beats per minute (bpm), metabolic equivalents (METs) at ventilatory threshold, METs at 130 bpm and heart rate at stage 1 of the Bruce protocol. Moderate-to vigorous physical activity (MVPA) was measured (Actical accelerometer with 15 second epochs) for 7 consecutive days. Exposure to cyanosis was calculated by subtracting the child’s date of birth from the date of surgical repair. Results: Participants were children with a Fontan single ventricle (n=5), tetralogy of Fallot (n=4) or transposition of the great arteries (n=7). Daily physical activity was positively associated with V̇O2 at ventilatory threshold (r = 0.78, n = 16, p = < 0.01) and V̇O2 at a heart rate of 130 bpm (r = 0.61, n = 16, p = 0.01). Children who did more than 60 minutes of physical activity per day (n=4) achieved significantly higher energy expenditure before reaching ventilatory threshold, (95% CI of the difference [8.23, 24.85], t(14) = 4.27, p = < 0.01) and at a heart rate of 130 bpm (95% CI of the difference [1.61, 14.33], t(14) = 2.69, p = 0.02). Lastly, V̇O2 at ventilatory threshold was negatively associated with days spent in cyanosis (r = .55, n = 16, p = 0.03), Conclusion: Higher V̇O2 at ventilatory threshold and V̇O2 at a heart rate of 130 bpm was associated with more daily minutes spent in moderate-to-vigorous physical activity. These results suggest that children who meet the recommended 60 minutes of MVPA would have a higher submaximal exercise capacity (V̇O2 at ventilatory threshold or a heart rate of 130 bpm), than children who did not meet the MVPA guidelines. Lastly, children who were exposed to cyanosis for a longer period of time had a lower submaximal V̇O2 at ventilatory threshold, than children who were exposed to cyanosis for a shorter period of time.

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