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Biomedical subjects

R F Bellamy

Publications and source records attributed to R F Bellamy.

6 recordsLinked to original sources
PubMed1979

Factors determining delayed peak flow in canine myocardial reactive hyperaemia.

It has been suggested that delayed restoration of flow to the deeper layers of the myocardium is responsible for the gradual rise to peak flow rate characteristic of myocardial hyperaemia (RH). The distribution of coronary flow during RH was studied by injecting radiomicrospheres into the left atrium open chest dog preparations just prior to the end of a 15 s occlusion of the left circumflex branch. The artery was then reoccluded after 1, 2, or 4 s of RH. Myocardium perfused by the left anterior decending branch served as a control; the ratio of endocardial to epicardial (end/epi) perfusion in this bed averaged 1.14. During coronary occlusion and during the first second of RH the end/epi ratio in the hyperaemic zone averaged 50% of control, but rose progressively to equal control at the time of peak flow. Although evanescent subendocardial ischaemia may contribute to the gradual rise to peak flow rate it cannot by itself account for the time course of this response.

Animals↗
PubMed1979

Blood viscosity.

Explore the source record for details and available documents.

Blood Viscosity↗
PubMed1978

Diastolic coronary artery pressure-flow relations in the dog.

Conscious dogs were used to investigate the relations between aortic (Pa) pressure and coronary flow (F) during individual diastoles. When the dogs were in a semibasal state, coronary pressure-flow relations were described by a family of lines, and diastolic flow was a linear function of aortic pressure. For a given perfusion pressure, higher flows were associated with lines of progressively greater slope and lower zero flow pressure intercept (Pf=0). Zero flow pressure intercepts were estimated by extrapolation and found to vary between 20 and 50 mm Hg, depending on the magnitude of flow. The zero flow pressure may represent the height of a vascular waterfall caused by vasomotor tone with the resistance-controlling coronary flow being (P-Pf=0).F-1. Interventions that decrease vasomotor tone increase coronary flow by both decreasing vascular resistance and increasing the perfusion pressure gradient. The gradient increases because the effective coronary back pressure is the height of the vascular waterfall and the latter is reduced when vasomotor tone falls. Passive changes in vessel dimensions, arterial recruitment, and autoregulation appear to be of little importance during individual diastoles.

Animals↗
PubMedDate not supplied

The medical effects of conventional weapons.

The medical effects of weapons used in modern conventional warfare are, overwhelmingly, penetrating. Fragments from explosive munitions such as shells, rockets, and grenades are the predominate source of missiles, especially in high-intensity war. Bullets from assault rifles and machine guns cause fewer casualties, except in counterinsurgency operations. The threat from penetrating missiles depends upon the part of the body that is struck and, to a lesser extent, upon the physical characteristics of the missile. The missile's mass and velocity determine its potential to do physical damage, but the extent to which this potential is realized depends upon diverse factors such as shape, construction, and stability. The American experience in the wars of this century indicate that approximately 20%-25% of all casualties died on the battlefield and are therefore classified as killed in action. Approximately 3%-5% die while receiving care, and thus are classified as died of wounds. Wounds of the brain or heart and great vessels are the most common causes of death. Prevention of sepsis in soft-tissue and orthopedic wounds is the major medical treatment problem in survivors. Since it determines the quality and quantity of combat casualty care, the single most important factor determining mortality or morbidity for combat casualties is the tactical situation.

Firearms↗