Human pregnancy is characterized by significant increases in central ventilatory drive and perceived respiratory discomfort (breathlessness). The physiological mechanisms of hyperventilation and breathlessness in pregnancy remain largely unknown and understudied. Objective: The main purpose of this research was to elucidate the mechanisms of maternal hyperventilation, and to systematically examine the contribution of alterations in central ventilatory drive, static/dynamic respiratory mechanics and their interaction with respect to the intensity of perceived breathlessness during exercise in pregnancy. General Methods: Experiments were conducted between 34-38 wks gestation and again 4-5 months post-partum in a total of 35 healthy, young women. A comprehensive mathematical model of ventilatory control was used to examine the role of alterations in wakefulness and central chemoreflex drives to breathe, acid-base balance and female sex hormones in maternal hyperventilation. The effects of pregnancy on detailed ventilatory (breathing pattern, airway function, operating lung volumes, esophageal pressure-derived indices of respiratory mechanics) and perceptual (breathing and leg discomfort) responses to incremental cycle exercise to the limits of tolerance were also examined. Results: Maternal hyperventilation resulted from a complex interaction between alterations in arterial and central acid-base balance and other factors that directly affect ventilation, including increased wakefulness and central chemoreflex drives to breathe, increased metabolism and decreased cerebral blood flow. Mechanical adaptations of the respiratory system, including recruitment of resting inspiratory capacity and reduced airway resistance, accommodated the increased demand for tidal volume expansion during exercise in pregnancy, while preserving effort-displacement and breathlessness-ventilation relationships. Variation in the severity of gestational breathlessness could not be explained by respiratory mechanical/muscular factors, but ultimately reflected variation in the amplitude of maternal hyperventilation and temporal desensitization to the sensory consequences of increased ventilation. Conclusion: Our results indicated that 1) the hyperventilation and attendant hypocapnia/alkalosis of pregnancy can be explained by alterations in wakefulness and central chemoreflex drives to breathe, acid-base balance, metabolic rate and cerebral blood flow; 2) mechanical adaptations of the respiratory system obviated the anticipated rise in perceived breathlessness for a given ventilation during exercise in pregnancy, and helped to ensure that peak aerobic working capacity was admirably preserved, even in late gestation; and 3) gestational breathlessness ultimately reflected the normal awareness of increased ventilation and contractile respiratory muscle effort. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2008-08-28 16:01:40.78

The goal of conformal radiation techniques is to improve local tumour control through dose escalation to target volumes while at the same time sparing surrounding healthy tissue. Respiratory motion is known to be the largest intra-fractional organ motion and the most significant source of uncertainty in treatment planning for chest lesions. A method to account for the effects of respiratory motion is to use four-dimensional radiotherapy. While analytical models are useful, it is essential that the motion problem in radiotherapy is addressed by both modeling as well as experimentally studies so that different obstacles can be overcome before clinical implementation of a motion compensation method. Validation of techniques aimed at measuring and minimizing the effects of respiratory motion require a realistic dynamic deformable phantom for use as a gold standard. In this work we present the design, construction, performance and deformable image registration of a novel breathing, tissue equivalent phantom with a deformable lung that can reproducibly emulate 3D non-isotropic lung deformations according to any real lung-like breathing pattern. The phantom consists of a Lucite cylinder filled with water containing a latex balloon stuffed with dampened natural sponges. The balloon is attached to a piston that mimics the human diaphragm. Nylon wires and Lucite beads, emulating vascular and bronchial bifurcations, were glued at various locations, uniformly throughout the sponges. The phantom is capable of simulating programmed irregular breathing patterns with varying periods and amplitudes. A deformable, tissue equivalent tumour, suitable for holding radiochromic film for dose measurements was embedded in the sponge. Experiments for 3D motion assessment, motion reproducibility as well as deformable image registration and validation are presented using the deformable phantom.

The increased work of breathing associated with intense cycling has been identified as a factor that may negatively affect cycling performance. The aerodynamic position, abnormal respiratory mechanics either at rest or during exercise, and the development of a tachypnoeic breathing pattern are factors known to increase the work of breathing. Breathing pattern retraining aims to decrease the work of breathing by delaying the onset of dynamic hyperinflation and the recruitment of accessory breathing muscles. To date no studies have investigated the performance, physiological and perceptual consequences of manipulating breathing pattern in trained cyclists. Purpose: The aim of the present study was to investigate the effect of breathing pattern retraining on 20-km time trial performance and respiratory and metabolic measures in competitive cyclists. Method: Twenty-four competitive male cyclists (age 37.7 ± 8.6 years, mean ± SD; peak 4.34 ± 0.47 L·min-1) were match paired on 20-km time trial performance and assigned at random to either an intervention group (breathing pattern retraining; N = 12) or control group (N = 12). 20-km time trial performance, pulmonary function and the physiological and perceptual response during a maximal incremental cycle step test were assessed pre- and post-intervention. The intervention group underwent four weeks of specific breathing pattern retraining using exercises designed to reduce dynamic hyperinflation and optimise respiratory mechanics. The control group attended the laboratory once a week during this period and performed a 10 minute sub-maximal ride wearing a biofeedback breathing harness. The control group was led to believe the purpose for their participation was to investigate the effect that maximal exercise had on breathing pattern, and to test the reliability of the breathing harness. There was no attempt to modify the breathing pattern of the control group. Data were analysed using an MS Excel spreadsheet designed for statistical analysis. The uncertainty in the effect was expressed as 90% confidence limits and a smallest worthwhile effect of 1.0% was assumed. Results: The intervention group showed substantial improvements in 20-km time trial performance (-1.5 ± 1.1%) and incremental power (3.2 ± 3%). Additionally, breathing frequency (-13.2 ± 8.9%; -9.5 ± 8.4%), tidal volume (10.6 ± 8.5%; 9.4 ± 7.6%), inspiratory time (10.1 ± 8%; 9.4 ± 7.7%), breathing RPE (-30 ± 33.9%; -24.7 ± 28.1%) and leg RPE (-27.9 ± 38.5%; -24.7 ± 28.2%) were all positively affected at lactate threshold and lactate turn point. No positive changes were observed in the control group for 20-km time trial performance (0.0 ± 1.0%), incremental power (-1.4 ± 3.5%), breathing frequency (-1.6 ± 8.0%; -2.0 ± 7.9%), tidal volume (0.9 ± 7.2%; 2.9 ± 9.4%), breathing RPE (16.1 ± 50.2%, 24.8 ± 43%) or leg RPE (13.4 ± 39.6%; 19.9 ± 43.2%) . Conclusion: These results provide evidence of the performance enhancing effect of four weeks of breathing pattern retraining in cyclists. Furthermore, they suggest breathing pattern can be retrained to exhibit a controlled pattern, without a tachypnoeic shift, during high intensity cycling. Additionally, these results indicate breathing pattern retraining attenuates the respiratory and peripheral perceived effort during incremental exercise. Key words: Breathing pattern disorders, retraining, blood stealing, cycling, performance, power output, respiratory mechanics, perceived exertion, 20km-TT

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 7 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Michigan, 1984.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (M.Sc.). / Written for the Dept. of Human Genetics. Title from title page of PDF (viewed 2009/07/02). Includes bibliographical references.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.