The interrupter technique is used to determine airway and tissue resistance. Their accuracy is influenced by the technical properties of the interrupter device and the compliance of the respiratory system. We investigated the influence of valve characteristics and respiratory system compliance on the accuracy of determining airway and tissue resistance by means of a computer simulation. With de...

Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the m...

An 18-year-old patient, who had polysplenia and single ventricle, presented with altered mental status 9 years after a Fontan-type operation and pacemaker implantation. He underwent replacement of common atrioventricular valve and aortic valve plasty 1 year previously and has been placed on multiple medications including beta-blocker for his poor ventricular function. Blood chemistry revealed h...

The velopharynx is a tridimensional muscular valve located between the oral and nasal cavities, consisting of the lateral and posterior pharyngeal walls and the soft palate, and controls the passage of air. Velopharyngeal insufficiency may take place when the velopharyngeal valve is unable to perform its own closing, due to a lack of tissue or lack of proper movement. Treatment options include ...

The case of a 33-year-old male suffering from left sinus Valsalva aneurysm into anterior right ventricle and severe aortic valve regurgitation is presented. Diagnosis of this association was achieved before surgery by cardiac catheterization and Echocardiography. The patient was submitted to surgical repair by closing the orifice of the aneurysm using a bovine pericardium patch. The aortic valv...

Abnormalities in the silastic poppets of cardiac valve prostheses have been detected with increasing frequency. Ball variance can cause serious mechanical dysfunction of the prosthesis and can result in sudden death. Contour sound spectrograms were recorded on 12 patients with ball variance confirmed by operation and 25 controls. In ball variance the frequency of the aortic opening sound at the...

An unstable discharge rate occurs during dry fine powder from a hopper because of the significant two-phase solid/gas interactions that occur in flows. In addition, air bubble phenomenon may silo discharge. this study, we conducted experiments using semi-conical dual-structure hopper, and examined effects on internal flow structure, cavity fluid pressure, pressure inside airtight section, when ...

In the recent past, the mitral valve was referred to as the cornerstone of any echocardiographic examination. Changes in its echocardiographic pattern were considered, in many cases, to be specific for the diseases in which they were described. Among such diseases was hypertrophic cardiomyopathy. Three abnormalities were successively described in the M-mode echocardiograms of patients with the ...

Differing from the traditional method of treating the motion of ring valve-plates as translational or inclined motions of rigid bodies, this paper originated from the concept on deformations involved in the motion processes. Emphasis of research is centered on flexural warping vibrations during opening and closing. Mechanical modelling and mathematical interpretions of plate motion with various...

The equations of motion of plate type suction and discharge valves mounted on reciprocating pistons are given. Their solutions by modal series expansion are discussed and finally given in a form that conforms to the notation and approach used in previous work. Using the definition of an equivalent pressure, it is shown that both types of valves are assisted in closing, which may result in prema...