Cardiopulmonary stress

Adapted from Madama VE. Pulmonary function testing and cardiopulmonary stress testing. Albany, NY, Delmar, 1993.)... 

For the growing number of patients with combined pulmonary hypertension and abnormal left ventricular hemodynamics, a careful hemodynamic study can help to delineate the subtleties of both diseases and response to therapies. Exercise catheterization is recommended in those patients with normal hemodynamics at rest, but with a pretest likelihood of PAH and/or other data suggesting exercise-induced symptoms, for instance, exercise echo or cardiopulmonary stress test. Unfortunately, to date there is no consensus as to the best exercise protocols for an appropriate hemodynamic assessment. Among those used include upright bicycle with neck pulmonary arterial (PA) lines at 75% predicted maximum exercise, supine bicycle, supine arm exercise, and supine volume loading. In all cases, it is essential to carefully measure PCWP, cardiac outputs, and PA pressures at consistent parts of the respiratory cycle, and not merely PA pressures. 

Prime solutions used during cardiopulmonary bypass, prepared with either pasteurized human albumin or fresh-frozen plasma, were found to have low TAC, which may increase oxidative stress in neonates undergoing cardiopulmonary bypass (M26). 

I I I Clermont G, Vergely C, Jazayeri S, et al. Systemic free radical activation is a major event involved in myocardial oxidative stress related to cardiopulmonary bypass. Anesthesiology 2002 96 80-87. 

During cardiopulmonary bypass, addition of fluids such as anticoagulants leads to a reduction in the hematocrit or percentage or the total blood volume that is made up of red blood cells. Thus the elastic properties of blood do not affect blood flow in a BO [48]. Further, since the hematocrit of the blood is low, cell-cell interactions are likely to be less important. In modem BOs, the average relative shear stress on the blood is about 5-30 Pa [20]. Under these conditions, blood may be modeled as a shear-thinning fluid. Consequently, a Newtonian blood analogue fluid cannot model the variation of blood viscosity with shear rate. 

Gu YJ, Boonstra PW, Graaff R, Rijnsburger AA, Mungroop H, and van Oeveren W. Pressure drop, shear stress, and activation of leukocytes during cardiopulmonary bypass A comparison between hollow fibre and flat sheet membrane oxygenators. Artif. Organs 2000 24(1) 43 8. 

Immediately following cardiopulmonary bypass an elevation in pulmonary vascular resistance is poorly tolerated. The pulmonary vasculature of such children is prone to intense vasoconstriction in response to stress that may result in pulmonary hypertensive crises. This may necessitate therapeutic maneuvers, including continued paralysis and anesthesia, to blunt the stress response " and hyperventilation and alkalosis to promote pulmonary vasodilation. The realization that inhaled nitric oxide could act as a selective pulmonary vasodilator " holds great promise for this patient population, and a number of studies have attested to its efficacy both in the preoperative evaluation during cardiac catheterization and postoperatively in the intensive care unit " . 

Workers who perform heavy physical work are subjected not only to forces and stresses from the immediate physical environment but also to mechanical forces generated from within the body. As a result of these forces and stresses, a strain is produced on the worker s musculoskeletal system as well as on other systems such as the cardiopulmonary system. One of the most important issues in the apphcation of ergonomics to work design is to reduce the stresses imposed on the musculoskeletal and cardiopulmonary systems (Ayoub and Mital 1989). Several approaches have been used by different investigators to estabhsh safe handling limits, including the psychophysical approach, the physiological approach, and the biomechanical approach. 

These disorders include hypertensive disease, ischemic heart disease, other forms of heart disease, and cerebrovascular disease. As with cancer, the specific contribution of occupational factors to the causation of CVD has been debated, but there is agreement that some workplace factors contribute to or cause CVD (see Smith and Sainfort 1990 for a detailed discussion of psychosocial factors and their contribution). Four main occupational sources of CVD causation are agents that affect cardiopulmonary capacity, chemicals, noise, and psychosocial stress. 

Cardiovascular disease, namely, coronary artery disease, remains the leading cause of death in the developed nations. Over the last few years, MEMS sensors have advanced the understanding of blood flow, namely, fluid shear stress, in arterial circulation. Fluid shear stress is defined as the frictional force acting tangentially on the surface of a blood vessel wall. Furthermore, the measurement of wall shear stress is important to study the durability of prosthetic valves and to monitor thrombosis or blood clots in cardiopulmonary bypass machines, artificial hearts, and left ventricular assist devices. Luminal shear stress measurement predicts the development of atherosclerotic plaque in patients at risk for acute heart attacks. In this context, the application of microscale hot-wire anemometry bridges fluid mechanics of blood flow with vascular biology. 

Ulus, AT, Aksoyek, A, Ozkan, M, Katircioglu, SF and Basu, S (2003) Cardiopulmonary bypass as a cause of free radical-induced oxidative stress and enhanced blood-bome isoprostanes in humans. Free Radio Biol Med, 34, 911-917. 

Cohen D, Horiuchi K, Kemper M, et al. Modulating effects of propofol on metabolic and cardiopulmonary responses to stressful intensive care unit procedures. Crit Care Med 1996 24 612-617. 

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