Novel method of transpulmonary pressure measurement with an air-filled esophageal catheter

Background There is a strong rationale for proposing transpulmonary pressure-guided protective ventilation in acute respiratory distress syndrome. The reference esophageal balloon catheter method requires complex in vivo calibration, expertise and specific material order. A simple, inexpensive, accurate and reproducible method of measuring esophageal pressure would greatly facilitate the measure of transpulmonary pressure to individualize protective ventilation in the intensive care unit. Results We propose an air-filled esophageal catheter method without balloon, using a disposable catheter that allows reproducible esophageal pressure measurements. We use a 49-cm-long 10 Fr thin suction catheter, positioned in the lower-third of the esophagus and connected to an air-filled disposable blood pressure transducer bound to the monitor and pressurized by an air-filled infusion bag. Only simple calibration by zeroing the transducer to atmospheric pressure and unit conversion from mmHg to cmH2O are required. We compared our method with the reference balloon catheter both ex vivo, using pressure chambers, and in vivo, in 15 consecutive mechanically ventilated patients. Esophageal-to-airway pressure change ratios during the dynamic occlusion test were close to one (1.03 ± 0.19 and 1.00 ± 0.16 in the controlled and assisted modes, respectively), validating the proper esophageal positioning. The Bland–Altman analysis revealed no bias of our method compared with the reference and good precision for inspiratory, expiratory and delta esophageal pressure measurements in both the controlled (largest bias −0.5 cmH2O [95% confidence interval: −0.9; −0.1] cmH2O; largest limits of agreement −3.5 to 2.5 cmH2O) and assisted modes (largest bias −0.3 [−2.6; 2.0] cmH2O). We observed a good repeatability (intra-observer, intraclass correlation coefficient, ICC: 0.89 [0.79; 0.96]) and reproducibility (inter-observer ICC: 0.89 [0.76; 0.96]) of esophageal measurements. The direct comparison with pleural pressure in two patients and spectral analysis by Fourier transform confirmed the reliability of the air-filled catheter-derived esophageal pressure as an accurate surrogate of pleural pressure. A calculator for transpulmonary pressures is available online. Conclusions We propose a simple, minimally invasive, inexpensive and reproducible method for esophageal pressure monitoring with an air-filled esophageal catheter without balloon. It holds the promise of widespread bedside use of transpulmonary pressure-guided protective ventilation in ICU patients.

Hydrolysis of trichosanthin (TCS) catalyzed by imidazolium-based ionic liquids in heating and microwave-assisted modes

Two modes of TCS hydrolysis based on ILs were compared and a higher degree of hydrolysis can be obtained compared to common catalysts.

3D Numerical Simulation of the Hollow Square-Typed Polymer Based on Gas-Assisted Extrusion Method

According to the properties of hollow square-typed polymer extrudate, the three dimensional numerical simulation of hollow square-typed polymer extrudate based on gas-assisted extrusion technology was performed by using finite element method. Meanwhile, four different gas-assisted modes imposed on the outer and inner wall of hollow square-type extrudate were considered. The extrudate swell ratios and field distributions, such as pressure drop, velocities and normal stresses of four different gas-assisted modes were obtained and compared with each other. Research results show that the extrudate swell ratios and field distributions of different gas-assisted modes are completely different. For the mode of gas-assisted on the single wall, the extrudate swell or shrink phenomena are large due to the non-symmetric properties of field distributions. For the no gas-assisted mode, although the physical field values are large, the extrudate swell ratio is not large due to the interaction role of both walls. For the mode of gas-assisted on both walls, the physical field values, such as pressure drop, normal velocities and stresses are all diminished, and the extrudate swell phenomenon was completely eliminated.

ON THE MATHEMATICAL MODELING OF SOLITON-MEDIATED LONG-RANGE ELECTRON TRANSFER

We discuss here possible models for long-range electron transfer (ET) between a donor (D) and an acceptor (A) along an anharmonic (Morse–Toda) one-dimensional (1d)-lattice. First, it is shown that the electron may form bound states (solectrons) with externally, mechanically excited solitons in the lattice thus leading to one form of soliton-mediated transport. These solectrons generally move with supersonic velocity. Then, in a thermally excited lattice, it is shown that solitons can also trap electrons, forming similar solectron bound states; here, we find that ET based on hopping can be modeled as a diffusion-like process involving not just one but several solitons. It is shown that either of these two soliton-assisted modes of transport can facilitate ET over quite long distances.