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Pulmonary gas exchange
Published in Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson, Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson
Figure 8.12 shows the increase in ventilation/perfusion inequality caused both by increasing altitude and increasing work level in the 40-day low-pressure chamber experiment (Wagner et al. 1987). The vertical scale shows the mean log standard deviation of the blood flow distribution, which is one measure of the degree of ventilation/perfusion inequality. It can be seen that this index was about 0.5 during rest at sea level but increased slightly when the oxygen consumption was raised to over 3 L min−1 during exercise at sea level. At very high altitude, where the barometric pressure was 347 mmHg, the standard deviation at rest rose to approximately 0.9 and it increased further to over 1.5 with exercise. The explanation of these intriguing data is uncertain but may be subclinical pulmonary edema. There was also evidence that rapid ascent was more likely to result in ventilation/perfusion inequality than slow ascent, suggesting that inadequate acclimatization may have been an important factor. It is now known that both subclinical and alveolar edema can occur in some human athletes, even at sea level. This issue has been reviewed in detail elsewhere (Hopkins 2010a and 2010b).
Accuracy of Pressure and Shear Measurement
Published in J G Webster, 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.
Adaptation to Intermittent Hypoxia and its use for Protecting the Heart from Stress and Ischemic Damage
Published in Felix Z. Meerson, Alexander V. Galkin, Adaptive Protection of The Heart: Protecting Against Stress and Ischemic Damage, 2019
Felix Z. Meerson, Alexander V. Galkin
The medical altitude chamber Ural-1 has been described in detail elsewhere, and its appearance is shown in Figure 7. It consists of the low-pressure chamber proper (the “hall”) and remote evacuation and conditioning system providing “ascent” and “descent” rates of 2 to 10 m/s. Such altitude chambers should be installed at policlinics, rehabilitation centers, and clinical research institutions.
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.