The phenomenon of negative right ventricular diastolic pressure immediately after operation for relief of isolated pulmonary valve stenosis was investigated in 11 patients. Pressures in the right ventricle and pulmonary artery were measured with a catheter tip micromanometer. One patient had a negative right ventricular diastolic pressure before operation. At the end of operation right ventricu...

Pulmonary hypertension frequently complicates mitral stenosis. Increased pulmonary artery pressure results from raised left atrial pressure, pulmonary arteriolar constriction, and obliterative changes in the pulmonary vascular bed, and usually responds to surgical relief of mitral stenosis. However, severe pulmonary hypertension may persist after surgical treatment of mitral stenosis. We descri...

Progressive narrowing of the aortic valve orifice eventually leads to limitations in cardiac output and myocardial blood flow, particularly during exercise or other physiological stress. The pressure gradient across the stenotic aortic valve is a useful and reproducible measure of the severity of the stenosis in most patients. The mainstay of therapy for aortic stenosis is relief of the fixed o...

Pulmonary valve stenosis was relieved by balloon dilatation during cardiac catheterisation on 27 occasions in 23 infants and children aged 7 days to 12 years, median 31 months (three aged less than 2 weeks). Pulmonary valve diameter was estimated by cross sectional echocardiography to assist in the choice of balloon size. Before dilatation the right ventricular systolic pressure ranged from 41 ...

This paper presents the lumped parameters model of an internal gear crescent pump with relief valve, able to estimate the steady-state flow-pressure characteristic and the pressure ripple. The approach is based on the identification of three variable control volumes regardless of the number of gear teeth. The model has been implemented in the commercial environment LMS Amesim with the developme...

In this paper, the authors present hydraulic and electro-hydraulic simulations of circuits needed for ALARS (Automated Launch Recovery System). fact, is used to launch side-scan sonar into sea. First circuit has following devices: tank, filter, fixed displacement pump, check valve, 4/3- way valve with two buttons, throttle pressure relief hand lever tanks reservoir, filter double acting cylinde...