The determination of required pressure level to provide an optimum treatment is an important task for vascular clinicians. This thesis is a first investigation including both venous and arterial femoral velocities and distal microcirculation of the forefoot to evaluate the effects of varying uniform external compression applied to the whole lower limb in humans. The ultrasound technique has been used to evaluate the maximal venous and arterial velocities in femoral common vessels. The microcirculation and the cutaneous oxygenation of the forefoot were recorded by laser Doppler fluxmetry and transcutaneous oxygen and carbon dioxide pressure measurements respectively. The findings of the present investigation support the concept that a uniform pressure applied to the full length of a healthy leg when the subject is in recumbent position should probably not exceed 10 mmHg, since significant impairment of both macro and microcirculation can be found. A database of information collected from twenty eight healthy subjects was established. Using this database and regression analysis, a new empirical model was produced which gave a hierarchical description of oxygen in terms of applied pressure and subject's characteristics. The developed model was expressed in terms of a cubic polynomial and was analysed in the content of catastrophy theory. This was appropriate to account for sudden changes in the data. Although the results obtained were based on this preliminary study, it appears that the predictive results are extremely encouraging and form a solid basis for future research. The observations of cubic forms in medical statistics as well as the inclusion of micro and macro in a single model are approaches that have been neglected in the past. A further area of apparent neglect appears to be in the careful selection of the sampling intervals to optimise information content of the database.

No description available.

No description available.

Venous disease is a very common disease that affects millions of people worldwide. While some of the factors that cause the development of varicose veins are well understood, the aetiology of venous ulceration is poorly understood. It has been demonstrated that venous valve failure in the large veins is an important factor leading to the development of varicose veins, however whether similar valves exist in the very small superficial veins of the human leg, and what role these valves may have in venous disease, is unknown. Therefore, the purpose of this study is to: 1. Identify whether venous valves are present in the very small superficial veins of the human leg, and if they are present, 2. Describe the density, size distribution, morphology, and regional distribution of these microvenous valves in �normal� cadaveric legs 3. Compare the �normal� microvenous valves from cadaveric tissue with microvenous valves from pathologic legs with chronic venous disease, to answer the hypothesis that individuals that develop venous ulceration have fewer microvenous valves than the normal population. In order to examine microvenous valves, two main methods have been utilised, E12 sheet plastination and vascular casting. These methods in combination provide valuable insights into the anatomy of microvenous channels, and allow examination and quantification of the venous valves. Using several techniques, this study has shown that microvenous valves are present within the very small veins of the superficial tissue of the human leg. These microvalves have been shown to be most prevalent in the smallest of the veins, down to 18[mu]m in diameter. Approximately 60% of the valves were found to be associated with tributaries. The gaiter region was demonstrated to contain the lowest number and density of microvenous valves, significantly less that the upper or mid calf regions. In addition, the gaiter region was found to have a much lower proportion of microvalves in the most superficial veins, when compared with the other regions examined. Contrary to our hypothesis, the number and density of microvalves in venous diseased legs was not different to that of normal legs. Similarly, the size and regional distributions were also not different. However, the microvalves from the venous diseased legs were significantly stretched and incompetent, allowing retrograde flow from the large veins through to the dermal capillaries. In conclusion, this study has shown that venous valves are present in the smallest of the superficial veins of the human leg, and that their density and distribution is not different between normal and venous diseased individuals. However, the microvalves from the diseased legs were incompetent and allowed retrograde flow. The role that these valves play in normal and pathological circulation is unclear, and warrants further examination.

Background: Many risk factors for venous thromboembolism have been identified, but two particular exposures - the use of combined oral contraceptives and long-distance air travel - have generated considerable concern in recent years. In contrast, a possible link between venous thromboembolism and a third exposure - the use of psychotropic drugs - was first raised in the 1950s, but has received surprisingly little attention. Information about all three exposures and the risk of fatal events is limited. These risks were examined in three inter-related national population-based studies. Methods: The underlying study population included all men and women aged 15 - 59 years who died in New Zealand between 1990 and 2000, for whom the underlying cause of death was pulmonary embolism. The potential associations between fatal pulmonary embolism and the use of oral contraceptives and psychotropic drugs were explored in a general practice records-based case-control study. Non-users were the reference category for all analyses. Contraceptive supply data were used to estimate the absolute risk of death from pulmonary embolism in users of oral contraceptives. A second case-control study, in which computer-assisted telephone interviews were undertaken with the next of kin of cases who had been resident in New Zealand, and with sex and age-matched controls randomly selected from the electoral roll, investigated the possible association between long-distance air travel and fatal pulmonary embolism. Finally, the absolute risk of dying from pulmonary embolism following a long-distance flight was estimated in a descriptive study based on official migration data and deaths in recent air travellers. Results: The adjusted odds ratio for use of any oral contraceptive in the three months before the index date (the onset of the fatal episode) was 13.1 (95% CI 4.4 - 39.0). The odds ratio for formulations containing desogestrel and gestodene was about three times higher than the point estimate for levonorgestrel products; preparations containing cyproterone acetate appeared to carry the highest risk. The estimated absolute risk of fatal pulmonary embolism in current users of oral contraceptives was 10.5 (95% CI 6.2 - 16.6) per million woman-years. The adjusted odds ratio for current use of any antipsychotic was 13.3 (95% CI 2.3 - 76.3). Low-potency antipsychotics carried a 20-fold increase in risk; thioridazine was the main drug involved. Antidepressant use was also associated with a significantly increased risk (adjusted odds ratio 4.9 [95% CI 1.1 - 22.5]). Compared with non-travellers, people who had undertaken a flight of more than eight hours� duration in the preceding four weeks were eight times more likely to die from pulmonary embolism (odds ratio 7.9 [95% CI 1.1 - 55.1]). The absolute risk of fatal pulmonary embolism following air travel of more than eight hours was 1.3 (95% CI 0.4 - 3.0) per million arrivals. Conclusions: The present research was the first to have estimated the relative risks of fatal pulmonary embolism in relation to three exposures: oral contraceptive use in a population in which preparations containing desogestrel and gestodene preparations were widely used, conventional antipsychotics, and long-distance air travel. The findings were consistent with previous, and subsequent, studies of non-fatal events. Increased risks of fatal pulmonary embolism in users of antidepressants, and in people with an intellectual disability, have not been described previously and warrant further investigation. Referral and diagnostic biases are very unlikely in these studies of fatal events, and other types of bias and possible confounding are considered unlikely explanations for the findings.

Venous disease is a very common disease that affects millions of people worldwide. While some of the factors that cause the development of varicose veins are well understood, the aetiology of venous ulceration is poorly understood. It has been demonstrated that venous valve failure in the large veins is an important factor leading to the development of varicose veins, however whether similar valves exist in the very small superficial veins of the human leg, and what role these valves may have in venous disease, is unknown. Therefore, the purpose of this study is to: 1. Identify whether venous valves are present in the very small superficial veins of the human leg, and if they are present, 2. Describe the density, size distribution, morphology, and regional distribution of these microvenous valves in �normal� cadaveric legs 3. Compare the �normal� microvenous valves from cadaveric tissue with microvenous valves from pathologic legs with chronic venous disease, to answer the hypothesis that individuals that develop venous ulceration have fewer microvenous valves than the normal population. In order to examine microvenous valves, two main methods have been utilised, E12 sheet plastination and vascular casting. These methods in combination provide valuable insights into the anatomy of microvenous channels, and allow examination and quantification of the venous valves. Using several techniques, this study has shown that microvenous valves are present within the very small veins of the superficial tissue of the human leg. These microvalves have been shown to be most prevalent in the smallest of the veins, down to 18[mu]m in diameter. Approximately 60% of the valves were found to be associated with tributaries. The gaiter region was demonstrated to contain the lowest number and density of microvenous valves, significantly less that the upper or mid calf regions. In addition, the gaiter region was found to have a much lower proportion of microvalves in the most superficial veins, when compared with the other regions examined. Contrary to our hypothesis, the number and density of microvalves in venous diseased legs was not different to that of normal legs. Similarly, the size and regional distributions were also not different. However, the microvalves from the venous diseased legs were significantly stretched and incompetent, allowing retrograde flow from the large veins through to the dermal capillaries. In conclusion, this study has shown that venous valves are present in the smallest of the superficial veins of the human leg, and that their density and distribution is not different between normal and venous diseased individuals. However, the microvalves from the diseased legs were incompetent and allowed retrograde flow. The role that these valves play in normal and pathological circulation is unclear, and warrants further examination.

Background: Many risk factors for venous thromboembolism have been identified, but two particular exposures - the use of combined oral contraceptives and long-distance air travel - have generated considerable concern in recent years. In contrast, a possible link between venous thromboembolism and a third exposure - the use of psychotropic drugs - was first raised in the 1950s, but has received surprisingly little attention. Information about all three exposures and the risk of fatal events is limited. These risks were examined in three inter-related national population-based studies. Methods: The underlying study population included all men and women aged 15 - 59 years who died in New Zealand between 1990 and 2000, for whom the underlying cause of death was pulmonary embolism. The potential associations between fatal pulmonary embolism and the use of oral contraceptives and psychotropic drugs were explored in a general practice records-based case-control study. Non-users were the reference category for all analyses. Contraceptive supply data were used to estimate the absolute risk of death from pulmonary embolism in users of oral contraceptives. A second case-control study, in which computer-assisted telephone interviews were undertaken with the next of kin of cases who had been resident in New Zealand, and with sex and age-matched controls randomly selected from the electoral roll, investigated the possible association between long-distance air travel and fatal pulmonary embolism. Finally, the absolute risk of dying from pulmonary embolism following a long-distance flight was estimated in a descriptive study based on official migration data and deaths in recent air travellers. Results: The adjusted odds ratio for use of any oral contraceptive in the three months before the index date (the onset of the fatal episode) was 13.1 (95% CI 4.4 - 39.0). The odds ratio for formulations containing desogestrel and gestodene was about three times higher than the point estimate for levonorgestrel products; preparations containing cyproterone acetate appeared to carry the highest risk. The estimated absolute risk of fatal pulmonary embolism in current users of oral contraceptives was 10.5 (95% CI 6.2 - 16.6) per million woman-years. The adjusted odds ratio for current use of any antipsychotic was 13.3 (95% CI 2.3 - 76.3). Low-potency antipsychotics carried a 20-fold increase in risk; thioridazine was the main drug involved. Antidepressant use was also associated with a significantly increased risk (adjusted odds ratio 4.9 [95% CI 1.1 - 22.5]). Compared with non-travellers, people who had undertaken a flight of more than eight hours� duration in the preceding four weeks were eight times more likely to die from pulmonary embolism (odds ratio 7.9 [95% CI 1.1 - 55.1]). The absolute risk of fatal pulmonary embolism following air travel of more than eight hours was 1.3 (95% CI 0.4 - 3.0) per million arrivals. Conclusions: The present research was the first to have estimated the relative risks of fatal pulmonary embolism in relation to three exposures: oral contraceptive use in a population in which preparations containing desogestrel and gestodene preparations were widely used, conventional antipsychotics, and long-distance air travel. The findings were consistent with previous, and subsequent, studies of non-fatal events. Increased risks of fatal pulmonary embolism in users of antidepressants, and in people with an intellectual disability, have not been described previously and warrant further investigation. Referral and diagnostic biases are very unlikely in these studies of fatal events, and other types of bias and possible confounding are considered unlikely explanations for the findings.

Thesis (PhD) - Swinburne University of Technology, 2008. / Submitted for the degree of Doctor of Philosophy, Swinburne University of Technology - 2008. Typescript. Includes bibliographical references (p.271-304).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 11, p. 2019-2020. Includes "Response of liver enzymes and other proteins to amino acid deficient diets, [by] J.R. Prigmore, J.W. Bothwell, and J.N. Williams, Jr. Reprinted from Proceedings of the Society for Experimental Biology and Medicine, vol. 88 (1955) p. 43-46" (4 leaves inserted between leaves 27-28). Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The human body is truly a fascinating and complex creation of our Maker. Because of the complexity and variability, many of its workings were little known until recent years. Some of the more amazing facts of the circulatory system follow. If the individual blood vessels of a single adult, i.e., artery, arteriole capillary, venule and vein, were laid end to end, they would extend more than 60,000 miles. For the average adult, the heart beats 70 times per minute; for the well-conditioned athlete, 50-60 beats per minute; and for the extraordinary athlete, as few as 37 times per minute. The volume of blood pumped per beat is approximately 80ml, which is equivalent to 5-6 liters quarts) of fluid per minute. During heavy exercise, it may increase to over 30 quarts per minute. The volume of blood pumped is approximately 5000-6000 quarts per day during more than 1000 cycles of the total blood supply of approximately 10 pints in the average human. Another point of interest is the ability of the arterioles to constrict, thereby decreasing the flow of blood to the skin to as little as 1 per cent of its normal value. This is done to preserve blood temperature at 37° Centigrade and is called vasoconstriction. Within the venous system, the body's blood gathering network, there is a tremendous redundancy of paths all leading back to the heart because of a system of valving that allows blood flow in one direction only. Should one path become closed or impaired, there is always another to be taken. The venous system will be explained in more detail in later paragraphs. The above information is summarized from the writings of Langely (1) and Nourse (2).