Effect of valve closure time on the determination of respiratory resistance by flow interruption

1987 ◽  
Vol 25 (2) ◽  
pp. 136-140 ◽  
Author(s):  
J. H. T. Bates ◽  
I. W. Hunter ◽  
P. D. Sly ◽  
S. Okubo ◽  
S. Filiatrault ◽  
...  
Keyword(s):  
Valve Closure ◽  
Respiratory Resistance ◽  
Flow Interruption ◽  
Closure Time

Charts for water hammer in pipelines resulting from valve closure from full opening only

1985 ◽  
Vol 12 (2) ◽  
pp. 241-264 ◽  
Author(s):  
Bryan W. Karney ◽  
Eugen Ruus
Keyword(s):  
Good Accuracy ◽  
Pipe Wall ◽  
Pressure Head ◽  
Wall Friction ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Closure Time ◽  
Basic Parameters ◽  
Valve Opening ◽  
Open Position

Maximum pressure head rises, which result from total closure of the valve from an initially fully open position, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Uniform, equal-percentage, optimum, and parabolic closure arrangements are analysed. Basic parameters such as pipeline constant, relative closure time, and pipe wall friction are considered with closures from full valve opening only. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe with good accuracy for the closure arrangements considered. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the parabolic closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Uniform closure produces pressure head rise that usually lies between those produced by the parabolic and the equal-percentage closure arrangements, except for the range of low pressure head rise combined with low or zero friction, where the rise due to uniform closure approaches that produced by optimum closure.

scholarly journals Radiographic pelvimetry in 0 to 24 month-old pacas (Agouti paca, Linnaeus, 1766)

2019 ◽  
Vol 71 (4) ◽  
pp. 1293-1298
Author(s):  
N.F. Smargiassi ◽  
I.C.C. Lippi ◽  
R.G.S. Oliveira ◽  
M.R.F. Machado ◽  
T.H.C. Sasahara ◽  
...  
Keyword(s):  
Age Determination ◽  
Strong Tendency ◽  
Birth Date ◽  
Scientific Interest ◽  
Closure Time ◽  
Ossification Centers ◽  
Constant Growth

ABSTRACT The pelvimetry consists of the metric determination of the pelvis dimensions and its use is directly related to the reproduction. The cartilage closure time of the ossification centers varies according to the bone, some closing already in the uterine life and others remaining present for many years. The objective was to evaluate, radiographically, the pelvic diameters by pelvimetry during the first 24 months of life in pacas, the second lagest Brazilian rodent and an animal that has shown big recent scientific interest, aiming the estimated age determination. Twelve pacas were used, which were monthly radiographed up from birth until 24 months old, with the animals anesthetized. The pacas are dolicopelvic animals and with pelvis presenting strong tendency to constant growth along the 12 first months of age, fact that can be useful in the approximated animals’ age determination that do not have precise birth date, for example.

Abstract 1606: High Specificity of Prolonged Isovolumic Contraction Time for Reverse Remodeling Associated with Cardiac Resynchronization Therapy

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Chinami Miyazaki ◽  
Charles J Bruce ◽  
Margaret M Redfield ◽  
Raul E Espinosa ◽  
David L Hayes ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Cardiac Resynchronization Therapy ◽  
Roc Analysis ◽  
High Specificity ◽  
Cardiac Resynchronization ◽  
Reverse Remodeling ◽  
Contraction Time ◽  
Valve Closure ◽  
Resynchronization Therapy ◽  
Closure Time

Background: Isovolumic contraction time (ICT) and pre-ejection period (PEP) are altered by electrical conduction delay as well as impaired contractility. An abnormal PEP has been used to select patients for cardiac resynchronization therapy (CRT), however, the predictive value of PEP for reverse remodeling (RR) has not been reported. The purpose of this study is to determine the predictive value of ICT and PEP for the RR in a prospective, single center CRT registry. Methods: Prospective registry of all heart failure patients undergoing CRT with echo pre-implant and at 3 and 6 months after implant. PEP was measured from the ECG Q wave onset to the aortic valve opening from the left ventricular outflow tract pulsed-wave Doppler tracing. The timing interval from the QRS onset to mitral valve closure was measured (mitral valve closure time). ICT was calculated as PEP-mitral valve closure time. RR was defined as >15% reduction in end-systolic volume (ESV) measured by biplane Simpson’s method. Death due to cardiac cause and heart transplantation during the 6 month period were considered as a non-response in the receiver-operating characteristics (ROC)analysis. Results: Echocardiography data was available in 83 patients at 3 and 59 patients at 6 month after CRT. RR occurred in 42 patients (51%) at 3 months and in 32 (54%) patients at 6 months By ROC analysis, the area under the curve (AUC) for predicting RR was 0.74 for ICT (p<0.001) and 0.73 for PEP (p=0.001) (See table ). ICT>123 ms yielded a very high specificity of 90–93% to predict responders at 6 month after CRT either in entire population or after excluding the patients with atrial fibrillation. Conclusion: A prolonged ICT is highly specific for predicting reverse remodeling after CRT although it is found in a limited number of patients. A strategy employing a screening ICT measurement may identify patients highly likely to achieve reverse remodeling after CRT, but can not be used to exclude patients for CRT. ROC analysis

Comparisons of CFD and Traditional Solutions for Steam Hammer Events

2017 ◽  
Author(s):  
Alex Mayes ◽  
Kshitij P. Gawande ◽  
Dennis K. Williams
Keyword(s):  
Pressure Wave ◽  
Power Plants ◽  
Peak Load ◽  
Critical Length ◽  
Pressure Change ◽  
Piping System ◽  
Valve Closure ◽  
Pipe System ◽  
Closure Time ◽  
Pressure Changes

Sudden pressure changes in the piping system of power plants are inevitable, and thus potential serious damage to large components, piping system, and piping supports is possible. To protect valuable components from such events, abrupt valve closure is employed to restrict the flow and prevent significant incidents and the resulting plant downtime. Unfortunately, when a valve is suddenly closed to prevent damage caused by unexpected events, a pressure wave within the flow is created, which travels upstream and impacts at the pipeline elbows. These events, involving sudden changes in pressure, are known as steam hammer. This steam hammer pressure wave, traveling through the pipe system, is capable of producing significant transient loads and stresses, which can disrupt the piping supports. As such there is a need for further investigation. The pressure wave depends on the characteristics of the flow, valve closure time, the elbow-to-elbow pipe section lengths, and the piping system flexibility. The present study performs a CFD analysis of the fluid experiencing such a sudden pressure change. OpenFOAM is used for this analysis and considers all the flow parameters, valve closure time, and critical length of the straight pipe. The study intends to provide a means of calculating the transient steam hammer loads applied on the pipe elbows, which consequently allows appropriate pipe support selection based upon the resulting peak loads. This computational analysis is compared to analytical methods for peak load determination such as rigid column theory, the Joukowsky method, and the steam hammer method explained by Coccio (1967) and Goodling (1989).

Determination of Total Respiratory Resistance in Health and Disease by Added External Resistance

CHEST Journal ◽  
1988 ◽  
Vol 93 (3) ◽  
pp. 537-540 ◽  
Author(s):  
Shou-Teh Chiang ◽  
Joseph Green ◽  
Yu-Cheng Kao
Keyword(s):  
Respiratory Resistance ◽  
External Resistance ◽  
Health And Disease

Comparison of descending phlebography with quantitative photoplethysmography, air plethysmography, and duplex quantitative valve closure time in assessing deep venous reflux

1992 ◽  
Vol 16 (6) ◽  
pp. 0913-0920 ◽  
Author(s):  
Thomas S. Riles ◽  
Harold J. Welch ◽  
Eleni C. Faliakou ◽  
Robert L. McLaughlin ◽  
Susan E. Umphrey ◽  
...  
Keyword(s):  
Valve Closure ◽  
Venous Reflux ◽  
Closure Time ◽  
Air Plethysmography

A modified forced oscillation technique for measurements of respiratory resistance

1977 ◽  
Vol 42 (4) ◽  
pp. 650-655 ◽  
Author(s):  
H. Aronsson ◽  
L. Solymar ◽  
J. Dempsey ◽  
J. Bjure ◽  
T. Olsson ◽  
...  
Keyword(s):  
Forced Oscillation ◽  
Signal To Noise Ratio ◽  
Optimization Technique ◽  
Forced Oscillation Technique ◽  
Respiratory Resistance ◽  
Asthmatic Children ◽  
The Difference ◽  
Resistance Value ◽  
Automated Determination

We present a modification of forced oscillation technique for automated determination of total respiratory resistance during inspiration. The modifications consist of a computerized signal averaging and an optimization technique in the assessment of the resistance value. Thereby a favorable signal-to-noise ratio is obtained, allowing very low superimposed pressure oscillations. The method is validated by comparison with a conventional esophageal balloon method, by estimating added mechanical resistances in healthy subjects and by measuring the effect of bronchodilation in asthmatic children. The coefficient of variation as obtained from day-to-day measurements was about 7%. Mechanical resistances, estimated as the difference in total resistance with and without external resistance, were within 7% of their values determined for the resistances alone. A significant decrease in resistance was obtained in each of the asthmatic children following bronchodilation.

Sign in / Sign up

Export Citation Format

Share Document