Application of an autotransfusion pressure control system in blood salvage

OBJECTIVE

This study was performed to evaluate the effect of a homemade autotransfusion pressure-control system on the regulation of negative pressure and to clarify the influence of different negative pressures on the recovered erythrocytes.

METHODS

Fifty patients were randomly divided into five groups, and five different suction-generated negative pressures were applied. Before suction, 6 mL of blood was collected from the surgical field; after suction, 6 mL of blood was collected from the blood storage tank. The hemoglobin, hematocrit, mean corpuscular volume, newly generated standardized plasma free hemoglobin, and change in the hemolysis rate of erythrocytes before and after suction were compared. Additionally, the erythrocyte morphology was observed.

RESULTS

The hemoglobin and hematocrit were significantly different before and after suction in all five groups. As the suction pressure increased, gradual increases were noted in the number of abnormal erythrocytes in the field of view, the newly generated standardized plasma free hemoglobin, and the change in the hemolysis rate.

CONCLUSIONS

The destruction rate of erythrocytes increased as the suction-generated negative pressure increased. When using a pressure-control system, a negative pressure of <200 mmHg should be applied to reduce the damage to the autotransfused blood.

A New inversion method of the initial state of Annulus in killing

Blowout is a major safety concern for well control in oil and gas well engineering and well killing is an important technical means to avoid blowout. Mastering the initial state of the wellbore is the basis to ensure well killing. The traditional gas column model cannot effectively explain the development law of wellbore pressure. Therefore, this paper is based on the actual killing conditions and the principle of gas-liquid two-phase flow. This paper establishes the physical model and mathematical model of the initial state of the wellbore annulus under overflow conditions. By means of the finite difference method and cyclic iteration calculation, the initial state of the wellbore annulus can be accurately inverted, and the calculation results are verified by an example. The results show that, when the wellhead pressure is determined, the wellbore pressure distribution and annular air phase distribution are more reasonable and the initial length of the overflow section is larger, the calculation results of the inversion method are closer to the actual engineering situation. The findings of this study can help to better understand wellbore state before killing and provide a theoretical basis for optimizing killing parameters, which is of great significance for avoiding well control safety risks during killing.

A Novel Method to Maintain the Sample Position and Pressure in Differentially Pumped Systems Below the Resolution Limit of Optical Microscopy Techniques

We present a new method to maintain constant gas pressure over a sample during in situ measurements. The example shown here is a differentially pumped high-pressure X-ray photoelectron spectroscopy system, but this technique could be applied to many in situ instruments. By using the pressure of the differential stage as a feedback source to change the sample position, a new level of consistency has been achieved. Depending on the absolute value of the sample-to-aperture distance, this technique allows one to maintain the distance within several hundred nanometers, which is below the limit of typical optical microscopy systems. We show that this method is well suited to compensate for thermal drift. Thus, X-ray photoelectron spectroscopy data can be acquired continuously while the sample is heated and maintaining constant pressure over the sample. By implementing a precise manipulator feedback system, pressure variations of less than 5% were reached while the temperature was varied by 400 ℃. The system is also shown to be highly stable under significant changes in gas flow. After changing the flow by a factor of two, the pressure returned to the set value within 60 s.

Attenuated Total Reflection (ATR) Sampling in Infrared Spectroscopy of Heterogeneous Materials Requires Reproducible Pressure Control

Attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, in which the sample is pressed against an internal reflection element, is a popular technique for rapid IR spectral collection. However, depending on the accessory design, the pressure applied to the sample is not always well controlled. While collecting data from fabrics with heterogeneous coatings, we have observed systematic pressure-dependent changes in spectra that can be eliminated by more reproducible pressure control. We also described a pressure sensor adapted to work with an ATR tower to enable more precise control of pressure during ATR sampling.

Gravity-Based Precise Cell Manipulation System Enhanced by In-Phase Mechanism

This paper proposes a gravity-based system capable of generating high-resolution pressure for precise cell manipulation or evaluation in a microfluidic channel. While the pressure resolution of conventional pumps for microfluidic applications is usually about hundreds of pascals as the resolution of their feedback sensors, precise cell manipulation at the pascal level cannot be done. The proposed system successfully achieves a resolution of 100 millipascals using water head pressure with an in-phase noise cancelation mechanism. The in-phase mechanism aims to suppress the noises from ambient vibrations to the system. The proposed pressure system is tested with a microfluidic platform for pressure validation. The experimental results show that the in-phase mechanism effectively reduces the pressure turbulence, and the pressure-driven cell movement matches the theoretical simulations. Preliminary experiments on deformability evaluation with red blood cells under incremental pressures of one pascal are successfully performed. Different deformation patterns are observed from cell to cell under precise pressure control.

Mid-frequency ventilation: A potential strategy for lung protective neonatal mechanical ventilation

Mid-frequency ventilation (MFV) is a mode of mechanical ventilation where pressure controlled breaths are delivered at higher than usual respiratory rates with a conventional ventilator. The use of higher than normal frequencies has been used in clinical practice for the last 30 yr. However, MFV is based in the mathematical modeling of a pressure control breath; were as ventilator frequency increases, at a constant inspiratory to expiratory time ratio, alveolar ventilation demonstrates a peak (maximized). This peak is typically found at higher than usual respiratory rates (optimal frequency) and lower tidal volume (V _T ). The clinical consequence is that for a given alveolar ventilation target, MFV provides optimal inspiratory pressure and respiratory frequency with the least V _T . MFV is a strategy where peak alveolar ventilation is identified and results in lower V _T at the same ventilation pressures. Current ventilators are able to deliver higher rates and thus can optimize the delivery of mechanical ventilation. Current clinical practice of mechanical ventilation utilizes a low V _T approach as a protective lung strategy to prevent further ventilator induced lung injury and thus potentially reduce mortality. Further, neonatal and pediatric patients who fail a conventional low V _T protective lung strategy are transitioned to either high frequency ventilation, which delivers small V _T at fast respiratory rates, or more invasive and expensive support such as extracorporeal membrane oxygenation. MFV may offer an alternative to deliver a protective lung strategy without the need for advanced equipment.

An Adaptive Home-Use Robotic Rehabilitation System for the Upper Body

Robotic rehabilitation systems have been developed to treat musculoskeletal conditions, but limited availability prevents most patients from using them. The objective of this paper was to create a home-use robotic rehabilitation system. Data were obtained in real time from a Microsoft \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\rm Kinect}^{\rm TM}$ \end{document} and a wireless surface electromyograph system. Results from the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\rm Kinect}^{\rm TM}$ \end{document} sensor were compared to a standard motion capture system. A subject completed visual follow exercise tasks in a 3-D visual environment. Data from two training exercises were used to generate a neural network, which was then used to simulate the subject's individual performance. The subjects completed both the exercise task output from the neural network (custom), and the unmodified task (standard). In addition, a wearable arm robot prototype was built. Basic system identification was completed, and a control algorithm for the robot based on pressure control was designed and tested. The subjects had greater root-mean-square error for position and velocity variables during the custom exercise tasks. These results suggest that the custom task was difficult to complete, possibly because the neural network was unconstrained. Finally, the robot prototype was able to mimic changes in a subject's elbow angle in real time, demonstrating the feasibility of the robotic rehabilitation system.