Blood Supply Function Research Articles

Modeling the dynamics of risk of altitude decompression sickness

A probabilistic model of decompression sickness is modified by introducing corrections that determine more precisely the risk of tissue injury by gas bubbles as a function of blood supply and bubble nucleation intensity. Parameters of the “worst” virtual tissues and theoretical curves corresponding to empirical data on the cumulative probability of decompression sickness symptoms for some altitude decompression procedures are determined. The parameters are shown to depend on final pressure, physical load, and duration of preoxygenation.

Coronary and extracoronary factors in hypertensive heart failure

1. 1. Cardiachypertrophy is the feature common to cases of congestive heart failure irrespective of the presence or absence of major coronary artery disease. The congestive heart failure associated with an inflammatory or toxic cardiac lesion is an exception to this rule. 2. 2. In hypertrophied heart muscle, the development of surface irregularities of the muscle fibers and alterations in the nuclei appear to be a compensatory mechanism to increase the diffusing surfaces. 3. 3. A decrease in capillary and arteriolar tree proportional to the volume of the muscle mass was observed. 4. 4. Three types of muscle changes were observed in many cases: 4.1. a. Microscopic acute infarcts similar to those seen in major coronary occlusion. 4.2. b. A slow process of fiber dissolution or fatty degeneration. 4.3. c. Connective tissue replacement of myofibrillae by an insensible merging of the muscle fibers with connective tissue. 5. 5. Anatomical, functional, and mechanical factors appear to play a rôle in myocardial fibrosis. This fibrosis is not directly dependent upon coronary sclerosis even in the presence of marked coronary disease. However, myocardial fibrosis appears to be related to anoxemia from whatever cause. 6. 6. A collateral circulation, both intracardiac and extracardiac may play a rôle in preventing failure of the hypertrophied heart. Sinusoids were found to be increased in number and size in many hypertrophied hearts and under certain circumstances are probably intimately associated with the nourishment of the heart. 7. 7. Congestive heart failure is due to coronary insufficiency only in the sense that impairment of nutrition and necrobiosis are, on final analysis, a function of blood supply in heart tissue as in any other tissue. 8. 8. Congestive heart failure is the failure of the heart which fails to undergo further hypertrophy. The cause of failure lies in some disturbance other than the anatomical, though cardiac hypertrophy is the cardinal associated finding. Such hearts may be correlated with demonstrable metabolic disturbances which appear to be the ultimate cause of failure.