Improvement of Sidestream Dark Field Imaging with an Image Acquisition Stabilizer

Background: In the present study we developed, evaluated in volunteers, and clinically validated an image acquisition stabilizer (IAS) for Sidestream Dark Field (SDF) imaging.Methods: The IAS is a stainless steel sterilizable ring which fits around the SDF probe tip. The IAS creates adhesion to the imaged tissue by application of negative pressure. The effects of the IAS on the sublingual microcirculatory flow velocities, the force required to induce pressure artifacts (PA), the time to acquire a stable image, and the duration of stable imaging were assessed in healthy volunteers. To demonstrate the clinical applicability of the SDF setup in combination with the IAS, simultaneous bilateral sublingual imaging of the microcirculation were performed during a lung recruitment maneuver (LRM) in mechanically ventilated critically ill patients. One SDF device was operated handheld; the second was fitted with the IAS and held in position by a mechanic arm. Lateral drift, number of losses of image stability and duration of stable imaging of the two methods were compared.Results: Five healthy volunteers were studied. The IAS did not affect microcirculatory flow velocities. A significantly greater force had to applied onto the tissue to induced PA with compared to without IAS (0.25 ± 0.15 N without vs. 0.62 ± 0.05 N with the IAS, p < 0.001). The IAS ensured an increased duration of a stable image sequence (8 ± 2 s without vs. 42 ± 8 s with the IAS, p < 0.001). The time required to obtain a stable image sequence was similar with and without the IAS. In eight mechanically ventilated patients undergoing a LRM the use of the IAS resulted in a significantly reduced image drifting and enabled the acquisition of significantly longer stable image sequences (24 ± 5 s without vs. 67 ± 14 s with the IAS, p = 0.006).Conclusions: The present study has validated the use of an IAS for improvement of SDF imaging by demonstrating that the IAS did not affect microcirculatory perfusion in the microscopic field of view. The IAS improved both axial and lateral SDF image stability and thereby increased the critical force required to induce pressure artifacts. The IAS ensured a significantly increased duration of maintaining a stable image sequence

Microvascular and interstitial oxygen tension in the renal cortex and medulla studied in a 4-h rat model of LPS-induced endotoxemia

The pathophysiology of sepsis-induced acute kidney injury remains poorly understood. As changes in renal perfusion and oxygenation have been shown, we aimed to study the short-term effects of endotoxemia on microvascular and interstitial oxygenation in the cortex and medulla, in conjunction with global and renal hemodynamics. In a 4-h rat model of endotoxemia, we simultaneously assessed renal artery blood flow and microvascular and interstitial oxygen tensions in the renal cortex and medulla using ultrasonic flowmetry, dual wavelength phosphorimetry, and tissue oxygen tension monitoring, respectively. Whereas medullary microvascular and interstitial oxygen tensions decreased promptly in line with macrovascular blood flow, changes in cortical oxygenation were only seen later on. During the entire experimental protocol, the gradient between microvascular PO₂ and tissue oxygen tension remained unchanged in both cortex and outer medulla. At study end, urine output was significantly decreased despite a maintained oxygen consumption rate. In this 4-h rat model of endotoxemia, total renal oxygen consumption and the gradient between microvascular PO₂ and tissue oxygen tension remained unaltered, despite falls in renal perfusion and oxygen delivery and urine output. Taken in conjunction with the decrease in urine output, our results could represent either a functional renal impairment or an adaptive respons

Safety of performing transbronchial lung cryobiopsy on hospitalized patients with interstitial lung disease.

INTRODUCTION: Transbronchial lung cryobiopsy (TBLC) has become a popular option for tissue diagnosis of interstitial lung disease (ILD), however reports vary regarding the safety of this procedure. Herein, we evaluate the safety of transbronchial cryobiopsy in hospitalized patients, comparing adverse events to outpatient procedures. METHODS AND MEASUREMENTS: This is a single center, retrospective chart review of all TBLC performed for suspected ILD between November 2013 and March 2017. Biopsies were performed by a board certified interventional pulmonologist or interventional pulmonology fellow using a two-scope technique. RESULTS: One hundred fifty-nine cryobiopsies were performed for the diagnosis of ILD. Rates of adverse events are as follows: pneumothorax 11%, persistent air leak 1.3%, moderate-severe bleeding 3.8%, ICU transfer within 48 h 3.1%, and all cause 30-day mortality 1.9%. No deaths were attributed to the procedure. Comparing adverse events between hospitalized patients and outpatients, rates of pneumothorax were 24% vs 9.9%, persistent air leak 5.9% vs 0.7%, ICU transfer 12% vs 2.1%, and 30-day mortality 5.9% vs 1.4%. However, no differences were statistically significant. CONCLUSION: Practitioners should recognize that while cryobiopsies are a high-yield, safe, and cost-effective alternative to surgical lung biopsy, not all procedures carry the same risk profiles. Hospitalized patients may have a greater propensity for pneumothorax, persistent air leak, transfer to the ICU, and 30-day mortality

Computational Approaches to Zeolite-Based Adsorption Processes

Computational methods to calculate the properties of zeolites in gas adsorption and separation have proven to be a valuable complement to experimental work. Molecular simulation provides a molecular understanding of the mechanisms involved in the adsorption, desorption, and transport. The accuracy and reliability of the predictions depend on the models used for adsorbates and adsorbents, the force fields that describe the interaction, and the computational methods to calculate the properties. The selection of force fields and methods depends on the properties of the systems and on characteristics such as the flexibility of the framework, the hydrophobicity/hydrophilicity of the zeolite, the chirality, the silicon atom substitutions, the nature and concentration of extra framework cations, the composition of the guest gases, the measured property, etc. In this chapter, a brief description of the state of the art of molecular simulation applied to porous materials is provided, as well as a discussion of current challenges in the field.</p