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Michael R. Pinsky - One of the best experts on this subject based on the ideXlab platform.

  • Tracheal gas insufflation during Pressure-control ventilation: effect of using a Pressure Relief Valve.
    Critical Care Medicine, 1997
    Co-Authors: Diane T. Gowski, Edgar Delgado, Adelaida M. Miro, Frederick J. Tasota, Leslie A. Hoffman, Michael R. Pinsky
    Abstract:

    OBJECTIVES: Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway Pressure, but a consequence of this Pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with Pressure-control ventilation to augment CO2 elimination. During Pressure-control ventilation with continuous TGI, we observed that peak airway Pressure increased above the set inspiratory Pressure. Based on this observation, we investigated the ability of the Pressure-control ventilator circuit to compensate for continuous TGI and the effect of insertion of a Pressure Relief Valve to eliminate over-pressurization. SETTING: University research laboratory. DESIGN: Using an artificial lung model, we studied the effects of continuous TGI with varying catheter flows (0, 2, 6, and 10 L/ min); ventilator frequencies (10 and 20 breaths/min); inspiratory duty cycles (0.33, 0.50, and 0.67); lung compliance (0.01, 0.02, and 0.04 L/cm H2O); and airway resistance (5, 20, and 50 cm H2O/L/sec) on: a) peak airway Pressure; b) total inspiratory tidal volume; c) ventilator-derived tidal volume; and d) intrapulmonary Pressure at end-exhalation (auto-PEEP). Tests were performed with and without a Pressure Relief Valve whose threshold "pop-off" Pressure was adjusted to match the set inspiratory Pressure (35 cm H2O) for a total of 432 experimental conditions. MEASUREMENTS AND MAIN RESULTS: Our data demonstrate that Pressure-control ventilation augmented with continuous TGI can increase peak airway Pressure above set inspiratory Pressure due to delivery of a higher than intended tidal volume. Predisposing conditions include catheter flow rates of 6 and 10 L/min, long inspiratory time, low compliance, and low resistance. With the Pressure Relief Valve, peak airway Pressure was maintained at the set inspiratory Pressure and total inspiratory tidal volume remained constant. CONCLUSION: A Pressure Relief Valve is a necessary adjunct to maintain peak airway Pressure at set inspiratory Pressure and keep total inspiratory tidal volume constant when continuous TGI is administered in conjunction with Pressure-control ventilation.

Diane T. Gowski - One of the best experts on this subject based on the ideXlab platform.

  • Tracheal gas insufflation during Pressure-control ventilation: effect of using a Pressure Relief Valve.
    Critical Care Medicine, 1997
    Co-Authors: Diane T. Gowski, Edgar Delgado, Adelaida M. Miro, Frederick J. Tasota, Leslie A. Hoffman, Michael R. Pinsky
    Abstract:

    OBJECTIVES: Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway Pressure, but a consequence of this Pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with Pressure-control ventilation to augment CO2 elimination. During Pressure-control ventilation with continuous TGI, we observed that peak airway Pressure increased above the set inspiratory Pressure. Based on this observation, we investigated the ability of the Pressure-control ventilator circuit to compensate for continuous TGI and the effect of insertion of a Pressure Relief Valve to eliminate over-pressurization. SETTING: University research laboratory. DESIGN: Using an artificial lung model, we studied the effects of continuous TGI with varying catheter flows (0, 2, 6, and 10 L/ min); ventilator frequencies (10 and 20 breaths/min); inspiratory duty cycles (0.33, 0.50, and 0.67); lung compliance (0.01, 0.02, and 0.04 L/cm H2O); and airway resistance (5, 20, and 50 cm H2O/L/sec) on: a) peak airway Pressure; b) total inspiratory tidal volume; c) ventilator-derived tidal volume; and d) intrapulmonary Pressure at end-exhalation (auto-PEEP). Tests were performed with and without a Pressure Relief Valve whose threshold "pop-off" Pressure was adjusted to match the set inspiratory Pressure (35 cm H2O) for a total of 432 experimental conditions. MEASUREMENTS AND MAIN RESULTS: Our data demonstrate that Pressure-control ventilation augmented with continuous TGI can increase peak airway Pressure above set inspiratory Pressure due to delivery of a higher than intended tidal volume. Predisposing conditions include catheter flow rates of 6 and 10 L/min, long inspiratory time, low compliance, and low resistance. With the Pressure Relief Valve, peak airway Pressure was maintained at the set inspiratory Pressure and total inspiratory tidal volume remained constant. CONCLUSION: A Pressure Relief Valve is a necessary adjunct to maintain peak airway Pressure at set inspiratory Pressure and keep total inspiratory tidal volume constant when continuous TGI is administered in conjunction with Pressure-control ventilation.

Hikaru Matsuda - One of the best experts on this subject based on the ideXlab platform.

  • Clinical application of vacuum-assisted cardiopulmonary bypass with a Pressure Relief Valve
    European Journal of Cardio-Thoracic Surgery, 2001
    Co-Authors: Yoshitaka Hayashi, Koji Kagisaki, Takahiro Yamaguchi, Taichi Sakaguchi, Yoshihisa Naka, Yoshiki Sawa, Shigeaki Ohtake, Hikaru Matsuda
    Abstract:

    Objectives: Hemodilution induced by cardiopulmonary bypass (CPB) often prevents open heart operations without blood transfusion because of a large CPB-priming volume. A vacuum-assisted venous drainage system appears to overcome this problem and our previous experimental study demonstrated the beneficial effect of a vacuum-assisted CPB with a Pressure Relief Valve. In this study, we clinically applied this novel system, and evaluated its efficacy by comparing it with the results of a conventional siphon-dependent drainage system. Methods: Sixty patients undergoing open heart operation were divided into Group V (vacuum-assisted system, na 30) and Group S (siphondependent system, na 30). The vacuum-assisted system contains a powerful vacuum generator and a Pressure Relief Valve to keep the negative Pressure in the reservoir constant when the blood suction is used. Results: The CPB-priming volume was significantly smaller in Group V (V vs. S: 1071 ^ 88 vs. 1405 ^ 137 ml; P , 0:01), resulting in the lower hemodilution in Group V evidenced by the minimum hemoglobin level (V vs. S: 6.83 ^ 1.06 vs. 5.78 ^ 0.79 mg/dl; P , 0:01) and blood transfusion rate (V vs. S: 9 vs. 20%; P , 0:01). There were no significant differences in the plasma free hemoglobin level and the reduction ratio of plasma haptoglobin between the groups. Conclusions: These data demonstrate that this vacuum-assisted CPB can provide simplification of the CPB circuit, resulting in a smaller CPB-priming volume and lower hemodilution. This vacuum-assisted CPB may attenuate the negative effect of CPB by minimizing hemodilution and appears to be a useful modification to accomplish no blood-requiring open heart operations. q 2001 Elsevier Science B.V. All rights reserved.

  • A Novel Technique for Cardiopulmonary Bypass Using Vacuum System for Venous Drainage with Pressure Relief Valve: An Experimental Study
    Artificial organs, 1998
    Co-Authors: Satoshi Taketani, Koji Kagisaki, Takahiro Yamaguchi, Yoshiki Sawa, Shigeaki Ohtake, Takafumi Masai, Hajime Ichikawa, Hikaru Matsuda
    Abstract:

    To decrease the circuit priming volume, develop safety, and simplify the equipment, a cardiopulmonary bypass (CPB) circuit using a vacuum suction venous drainage system with a Pressure Relief Valve was developed. The efficacy of this vacuum system was compared to that of a conventional siphon system. The system contains a powerful vacuum generator and a Pressure Relief Valve to keep the negative Pressure constant when blood suction is used. Using 8 mongrel dogs, the feasibility and the efficacy of this CPB system was tested. The changes in the negative Pressure in the reservoir were within 5 mm Hg whether the suction lines were switched on or off. In all animals the amount of blood in the venous reservoir was stable throughout bypass. The decrease of priming volume was from 725 ml (siphon system) to 250 ml (vacuum system). At the end of CPB, the levels of hemoglobin in the vacuum system were significantly higher than those in the siphon system. These results demonstrated that this vacuum drainage system can provide simplification and a miniaturization of the cardiopulmonary bypass circuit resulting in low hemodilution during CPB.

A. Alleyne - One of the best experts on this subject based on the ideXlab platform.

  • A model reference load controller with adaptation using a two stage Pressure Relief Valve
    Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148), 2001
    Co-Authors: Rong Zhang, A. Alleyne
    Abstract:

    To investigate generic power optimization problems of hydrostatic transmissions, an Earthmoving Vehicle Powertrain Simulator (EVPS) was built at the University of Illinois. A model reference load controller is designed to simulate different load dynamics for this "hardware-in-the-loop" test-bed. A two-stage Pressure Relief Valve serves as an actuator to change the load loop Pressure, thus to control the resistance on a hydraulic motor. The actuator dynamics result in a zero in such a load control problem, which limits the performance. The zero can be avoided by using an online simulation method. A Least Square Estimator as an adaptation updates plant parameters in real time to improve the online simulation accuracy. Simulation and experimental results of the load controller for a traction load reference model are presented. Relevant models of the hydraulic drive, the Pressure Valve and the traction load are also included.

Jian Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Fluid-structure interaction dynamic simulation of spring-loaded Pressure Relief Valves under seismic wave
    2018
    Co-Authors: Jian Zhang
    Abstract:

    In this paper, a fluid-structure interaction dynamic simulation method of spring-loaded Pressure Relief Valve was established. The dynamic performances of the fluid regions and the stress and strain of the structure regions were calculated at the same time by accurately setting up the contact pairs between the solid parts and the coupling surfaces between the fluid regions and the structure regions. A two way fluid-structure interaction dynamic simulation of a simplified Pressure Relief Valve model was carried out. The influence of vertical sinusoidal seismic waves on the performance of the Pressure Relief Valve was preliminarily investigated by loading sine waves. Under vertical seismic waves, the Pressure Relief Valve will flutter, and the reseating Pressure was affected by the amplitude and frequency of the seismic waves. This simulation method of the Pressure Relief Valve under vertical seismic waves can provide effective means for investigating the seismic performances of the Valves, and make up for the shortcomings of the experiment.

  • Prediction of blowdown of a Pressure Relief Valve using response surface methodology and CFD techniques
    Applied Thermal Engineering, 2018
    Co-Authors: Jian Zhang, Yang Liu, William Dempster, Jiuhong Jia
    Abstract:

    Abstract In this study, parametric assessment of the main geometric design features of a Pressure Relief Valve (PRV) with a backPressure chamber and two adjusting rings was conducted using response surface methodology. This design approach was established by using computational fluid dynamics (CFD) to model the dynamic performance of the opening and closing of a nuclear power main steam Pressure Relief Valve (NPMS PRV). An experimental facility was established to test the NPMS PRV in accordance with the standard ASME PTC 25, and to validate the CFD model. It was found that the model can accurately simulate the dynamic performance of the NPMS PRV; the difference in blowdown between the simulation and experiment results is found to be below 0.6%. Thus, the model can be used as part of a design analysis tool. The backPressure chamber assisted in the reseating and decreased the blowdown of the NPMS PRV from 18.13% to 5.50%. The sensitivity to Valve geometry was investigated, and an explicit relationship between blowdown and Valve geometry was established (with a relative error less than 1%) using the response surface methodology; this will allow designers to assess the Valve settings without the need for a CFD model.