The dynamic distribution of pulmonary ventilation was studied both theoretically and experimentally. The human lungs were simulated as two compartments driven by independent cyclic pleural pressures. The distribution of tidal volume depended primarily on the regional pressures, but dissimilar pressure swings generated sequential flows. A model of the tracer dynamics in the lung during a breath showed that the ventilation per unit volume was proportional to the time derivative of krypton-81m activity normalized by the activity itself. In gamma camera measurements, the average flow distribution was independent of frequency and tidal volume, but the flow per unit volume in left lateral decubitus subjects was greater in the dependent than the non-dependent lung, and sequential flows were evident. However, lung sound amplitudes were in phase over the dependent and non-dependent regions, varying as the square of the airflow at the mouth. The frequency composition of the sounds remained constant. Thus, nonhomogeneous pleural pressure swings appear to control the dynamic distribution of ventilation. This time-varying quantity can be measured using a short-lived isotope but not directly with lung sounds.

No description available.

This thesis investigates the feasibility of using a set of non-invasive biomedical signals to monitor respiration. The signals of interest being the electrocardiogram (EGG), photoplethysmography (PPG) and impedance plethysmography (IP) signals. The work has two main aims; the first being to estimate breathing rates from the signals, the second being to detect apnoeas from the signals. The fusion of information from different signals is used throughout in developing algorithms that give more accurate respiratory information than that obtained using one signal alone. Respiratory waveforms are derived from the signals, and the accuracy of detecting individual breaths from the waveforms is assessed and compared objectively. Results from evaluations on two separate databases show there is no waveform that gives sufficient accuracy to consider using it alone. A novel fusion method is developed which uses measurements from all three signals. This fusion method is based on weighting the estimates from each signal, according to the innovation from a Kalman filter model, applied to each respiratory waveform separately. The fused estimates give a higher overall correlation with respect to the reference breathing rate values than any of the breathing estimates derived from a single waveform. The detection of both central and obstructive sleep apnoea from the signals is investigated. It is shown that the accuracy of detecting central apnoeas from the IP signal using a timedomain method, often used in practice, can be improved by combining it with information from the frequency-domain. When discriminating between obstructive sleep apnoeic and non-apnoeic data it is seen that combining features from two signals results in a superior classification accuracy than is possible by using features from just one signal. The proposed classification system using just one of these signals, the EGG, is shown to give a performance accuracy comparable to that found in the literature. In conclusion this thesis shows that by fusing information from a number of non-invasive biomedical signals, estimations of breathing rates can be found with correlation 0.8. This is superior to estimation using only the impedance pneumography signal (correlation 0.64) which is currently used to monitor respiration. The fusion approach could potentially be applied to improve other non-invasive physiological monitoring systems.

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1967. / Bibliography: leaves 167-172. / vii, 172 l illus., tables

Thesis (Ph.D.) Dept. of Agricultural Biochemistry, Waite Institute, University of Adelaide, 1970 / xi, 156 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

An integrated description of the respiratory system of the abalone Haliotis iris is presented. These animals are believed to be inherently primitive and still bear the ancestral gastropod gill arrangement, thus allowing physiological examination of a 'living fossil'. Ventilation, gaseous diffusion, blood transport and the anatomical arrangement of the vascular system are examined under a range of conditions. Resting H. iris consume an average of 0.47 µmol 0₂.g live weight⁻¹ .h⁻¹, 87% of which is taken up across the gills, the remainder diffuses directly into the foot and epipodium. A 300g abalone ventilates its gills at a rate of 28mL.min⁻¹, a rate which, due to low resistance to diffusion (diffusion limitation index = 0.47) and a well matched ventilation/perfusion conductance ratio, is adequate to support the quiescent animal. Increased oxygen demand is accommodated by an increase in cardiac stroke volume, elevating output from 9.1 to 24.4 µL.g⁻¹.min⁻¹. At rest the right gill is the predominant gas exchanger, receiving 95.7% of the branchial blood flow, when cardiac output is elevated the left gill becomes equally perfused, effectively doubling the diffusing surface. Ventilation does not increase, and an increased reliance on assistance from external water currents is seen. Previously undescribed components of the vascular system, notably an extensive sinus of mixed venous and arterial blood surrounding the gut and a large vessel that offers a bypass to the right kidney, provide a low resistance circuit between the heart and gills, bypassing the major organs and muscles. The low resistance circuit allows haemolymph to pass from the aorta to the base of the gills with minimal loss of pressure and no phase shift in the pulse, allowing blood to cross the gills with maximal inertia and instantaneous pressure gradient. Haliotis iris therefore appears to have exploited its limited physiological resources to the maximum in the routine operation of its gas exchange system. It is concluded that further improvement could not occur without substantial remodeling of the body plan, which may account for the abandonment of the system by higher gastropods.

Greyhounds were trained to gallop at maximal running speed on a treadmill constructed for the purpose. This speed considerably exceeded maximal aerobic speed and was termed supramaximal. A mask was used to collect expired gases into bags during runs of 7.5 to 60 seconds and over the first 8-10 minutes of the recovery period. Respiratory parameters measured included VE, V02' VC02', R, fR', VT' ventilatory equivalent of °2 uptake and ventilatory equivalent of CO2 production. Respiration was found to be synchronised with the gallop stride, enabling both a high fR and VT. Mean VE reached 6 1.kg-1.min-1. Mean V02 reached 143ml.kg-l.min-l during the 30-45 second segment of running. Lactic acid draining into the blood stream displaced CO2 from the bicarbonate buffer system, so that R rose above 1.0. The highest value of R, 2.3 occurred in the second minute of recovery. The alactacid debt of the greyhound was found to be higher than that of man but was repaid much more rapidly because of the greyhound's superior oxygen transport system. The cardiovascular system was studied using electromagnetic and thermodilution flowmeters, and a heart rate telemeter. Changes in blood pressure caused changes in the relationship of the very elastic aortic root and the electromagnetic transducer cuff so that accurate calibration was not possible. Reliable values of cardiac output were obtained by thermodilution. Parameters measured included HR, cardiac output, SV and PCV taken before, during and for 1 hour after running. The minimum HR whilst sleeping was also obtained, and averaged 42 b min .-1 The HR was highest during runs of 30 seconds, 318 plus/minus18 b min -1. After running it fell sharply to below 160 in the second minute of recovery then rose to 200b.min-l 10 minutes after 30 and 45 second runs. HR was close to resting levels 1 hour after running. PCV after 30 seconds of running was 63.5 + 2.1% and had returned to resting values by 1 hour. Cardiac output during high speed runs was 914 + 209ml.kg-l.min-l while SV at 2.9 + 0.6ml. kg-l was increased 32% above resting SV. Acid-base balance of jugular venous blood was studied. Comparisons with arterial samples taken at the same time showed a useful relationship of arterial and jugular venous blood for lactate, base excess and pH. The time taken for blood lactate to reach its peak value varied with the intensity and the duration of the run. The jugular venous blood lactate level after 45 of running peaked at 181 plus or minus l5mg.dl-l (7 minutes after seconds running) , pH fell to 7.094 plus or minus 0.27, base excess to -23.4 plus or minus 2.7 mEq.l-l and PC02 to 23 + 2 mm Hg. All values had returned to resting level 1 hour after the run. Oxygen consumption during running, alactacid debt, lactate production and distance covered were used to calculate total energy cost and relative contributions of energy sources and energy cost.m -1. Anaerobic sources were the main contributors in the first 15 seconds but in the 15-30 second segment aerobic sources supplied 53% of the energy required and in the 30-45 second segment, 79%. The energy source contributions to30 seconds of running were aerobic 30%, alactacid debt 19% and lactic acid 51%. The energy cost.m-l at supramaximal speeds was higher than predicted by formulae derived from studies of dogs at submaximal speeds. The first 7.5 seconds of running cost almost as much as the next 22.5 seconds, indicating a high cost of acceleration. This is the first quantification of the energy cost of acceleration reported. Compared to man, the greyhound has a very high oxygen uptake during sprinting. Man's major deficiencies as a sprinter are a low maximal heart rate, small heart relative to body size and low PCV. Sprinting impedes respiration in man but aids it in the greyhound. Calculations indicate that when man runs at supramaximal speed, it costs more per metre than predicted by formulae derived at submaximal speeds and that the energy cost of acceleration is of the same order as in the greyhound although man attains a much lower peak speed.

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1994? / Includes bibliographical references (leaves 91-93).

Thesis (D.Sc.) -- University of Adelaide, 1981.