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.

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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.