Pressure Regulators
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod in The Primary FRCA Structured Oral Examination Study Guide 1, 2017
How does a single-stage regulator work?Pressure regulators consist of two chambers, a high-pressure chamber and a low or control pressure chamber, separated by a conical valve whose orifice is controlled by a spring connected to a diaphragm in the control chamber.They work by balancing the force from the spring against the force generated by pressure against the diaphragm.This shows that the performance of the valve is related to the ratio of the areas of the diaphragm and the valve: the bigger the difference, the greater the drop in pressure for the same force applied by the spring.From the diagram it can be seen that if the inlet pressure (P) increases, the diaphragm will lift and the conical valve will shut and vice versa. The pressure in the control chamber can be fixed or varied by altering the tension in the spring.
Accuracy of Pressure and Shear Measurement
J G Webster in Prevention of Pressure Sores, 2019
Each different type of pressure sensor has its own unique characteristics. As a result, the calibration methods used will vary depending on the sensor of choice. When calibrating an conductive polymer pressure sensor, a simple brass weight can be used to apply a uniform pressure to the sensor. Since the sensor area is known the applied pressure is easily calculated. However, applying a simple brass weight to a semiconductor diaphragm pressure sensor will produce no change in the sensor output. Figure 9.3 shows that placing a rigid weight with an area larger than the diaphragm will not cause any deflection of the diaphragm. Figure 11.2 shows a simple calibration apparatus which has proved useful for calibrating a variety of pressure sensors. A pneumatic pressure chamber driving a piston is another common calibration apparatus.
A
Anton Sebastian in A Dictionary of the History of Medicine, 2018
Artificial Respiration The first experiment on artificial respiration in animals was performed in 1667 by Robert Hooke (1635–1703), who kept the animals alive by blowing air through their lungs with bellows. Similar experiments were done by Robert Boyle (1627–1691) in the same year. John Fothergill (1712–1780), a physician from Yorkshire, in 1744 referred to the recovery of a man dead in appearance by distending his lungs with air. In 1855 Marshall Hall (1790–1857) of Nottingham, began his pioneering studies and introduced a method of artificial respiration. Theodore Tuffier (1857–1929) and Louis Hallion used the insufflation method in a patient during surgery for partial resection of his lung in 1896. This method was improved by Eugene Louis Doyen (1859–1916) and Rudolph Matas (1860–1957), who were cardiothoracic surgeons. The negative-pressure chamber was developed by German surgeon, Ferdinand Sauerbruch in 1903, and was in use up to 1940. Endotracheal insufflation used on a wider basis in early 1900 made it practical and revolutionized surgery and anesthesia.
Biomechanical Effects of Two Forms of PGF2α on Ex-vivo Rabbit Cornea
Published in Current Eye Research, 2021
Rong Zhu, XiaoBo Zheng, LiLi Guo, YiPing Zhao, Yuan Wang, Jie Wu, AYong Yu, JunJie Wang, FangJun Bao, Ahmed Elsheikh
Briefly, 24 corneas of each group were mounted onto a custom-built pressure chamber where mechanical clamps were used to ensure tight edge connection along the ring of scleral tissue of the specimen. The pressure chamber was filled with PBS and connected to a syringe pump to control the pressure inside the chamber. A differential pressure transducer (DMP-HS, Hangzhou, China) was adopted to monitor the real-time pressure in the chamber. A laser beam (LK series, Keyence, Milton Keynes, UK) was used to capture the displacement of corneal apex with 0.05 micron resolution. The experimental procedure illustrated in Figure 1 has been described in a previous study.19 Side images (Figure 1a) of each cornea were captured at different loading levels (0, 4, 8 mmHg, etc.) by three cameras (EOS 60D, Canon, Inc. Tokyo, Japan) arranged around the specimen with angles 75°, 195° and 316° measured from the right horizontal direction (Figure 1b). The anterior profiles were identified from the camera images using Image J software (version 1.45s, National Institutes of Health, USA) with 10 micron resolution. This process was used to determine the initial shape of specimen used later in construction of numerical models.
The FlowOx device for the treatment of peripheral artery disease: current status and future prospects
Published in Expert Review of Medical Devices, 2021
Patients with PAD are at risk of developing wounds and often have a delayed or impaired wound healing process. The areas of the lower leg and foot that are in contact with the pressure chamber during FlowOx treatment could theoretically be at risk of tissue damage. As part of the safety assessment, pressure measurements at contact points between the leg and the pressure chamber were performed during INP, concluding that the skin areas were not exposed to pressures, neither level nor duration, that impose a risk to PAD patients. The pressure levels were lower than those imposed by other interventions or treatments for PAD, diabetes, or critical limb ischemia (Dr. Daniel Parker, University of Salford, Manchester, UK, unpublished report).
Aerosols modification with H2O2 reduces airborne contamination by dental handpieces
Published in Journal of Oral Microbiology, 2021
Andrei Cristian Ionescu, Eugenio Brambilla, Lamberto Manzoli, Giovanna Orsini, Valentina Gentili, Roberta Rizzo
This study, not unlike any other, has strengths and limitations that must be discussed. A negative pressure chamber was custom-built according to a Class III cabinet’s specifications to accurately replicate the clinical operative conditions in a standardized way. Operator’s and patient’s phantom position, distance, and the handpiece setup were chosen to simulate a clinical situation where a conventional procedure was performed. The tested viral solutions were prepared using artificial saliva and inoculated into the patient phantom’s oral cavity immediately before each experimental run. This procedure was aimed to approximate as closely as possible the characteristics of aerosol spreading in the clinical setting.
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