[In vitro study on the sealing effect of different shapes of cuff tracheal tubes under the lowest safe pressure].

OBJECTIVE: To compare the effectiveness of cylindrical-shaped and conical-shaped cuff catheters for airway closure using different pressure measurement methods at the lowest safe pressure and to guide the clinical application. METHODS: Twenty-four patients with endotracheal intubation admitted to the intensive care unit (ICU) of Guangxi Medical University Cancer Hospital from December 2021 to January 2022 were enrolled. Leakage test in vitro was performed on the secretion on the patients' cuff. The needle and plunger from 20 mL syringe was separated, the syringe was sealed with adhesive, and the syringe nozzle was filled thoroughly to create a tracheal model. Consecutively, both cylindrical-shaped and conical-shaped cuff catheters were inserted into the simulated trachea, and the cuff pressure was calibrated to 20 cmH2O (1 cmH2O ≈ 0.098 kPa) before commencing the experiment. The viscosity of the secretion on the patients' cuff was classified (grade I was watery subglottic secretion, grade II was thick subglottic secretion, grade III was gel-like subglottic secretion), and the same viscosity secretion was injected into the catheter cuff. Utilizing a self-control approach, intermittent pressure measurement was initially conducted on both the cylindrical-shaped and conical-shaped cuff by improved pressure measurement method (intermittent pressure measurement group), followed by continuous pressure measurement experiment (continuous pressure measurement group). The leakage volume of the three viscosity subglottic secretions and the values of cuff pressure measurement of different shaped cuff catheters at 4, 6, 8 hours of inflation were recorded. RESULTS: A total of 180 retention samples were extracted from 24 patients with tracheal intubation during ventilation, with 90 samples in each of the two groups using different pressure measurement methods, and 30 samples of retention materials with different viscosities in each group. In the intermittent pressure measurement group, at 4 hours of inflation, all samples of secretion with grade I and grade II on cylindrical-shaped cuff leaked, while 3 samples of secretion with grade III also leaked. For conical-shaped cuff, 28 samples of secretion with grade I leaked, only 2 samples of secretion with grade II leaked, and there was no leak for secretion with grade III. At 6 hours of inflation, all samples of the three viscosity secretions on different shaped cuffs leaked. The leakage was gradually increased with the prolongation of inflation time. In the continuous pressure measurement group, at 4 hours of inflation, all samples of secretion with grade I on cylindrical-shaped cuff leaked, while 29 samples of secretion with grade II leaked, and there was no leak for secretion with grade III. For the conical-shaped cuff, 26 samples of secretion with grade I leaked, and there was no leak for secretion with grade II and grade III. At 6 hours of inflation, the conical-shaped cuff still had no leak for secretion with grade III. As the inflation time prolonged, the leakage of subglottic secretion on different shaped cuffs in both groups was gradually increased. At 8 hours of inflation, all samples experienced leakage, but the leakage of subglottic secretion on different shaped cuffs in the continuous pressure measurement group was significantly reduced as compared with the intermittent pressure measurement group [leakage for secretion with grade III (mL): 1.00 (0.00, 1.25) vs. 2.00 (1.00, 2.00) on the cylindrical-shaped cuff, 1.00 (0.00, 1.00) vs. 2.00 (2.00, 2.00) on the conical-shaped cuff, both P < 0.01]. The values of pressure measurement of cuffs with different shapes at different time points of inflation in the continuous pressure measurement group were within the set range (20-21 cmH2O). The cuff pressure at 4 hours of inflation in the intermittent pressure measurement group was significantly lower than the initial value (cmH2O: 18.3±0.6 vs. 20.0±0.0 in the cylindrical-shaped cuff, 18.4±0.6 vs. 20.0±0.0 in the conical-shaped cuff, both P < 0.01), and the cuff pressure in both shaped cuffs showed a significant decrease tendency as inflation time prolonged. However, there was no statistically significant difference in values of pressure measurement between the different shaped cuff catheters. CONCLUSIONS: Continuous pressure monitoring devices can maintain the effective sealing of conical-shaped cuff catheters at the lowest safe pressure. When using an improved pressure measurement method for intermittent pressure measurement and/or using a cylindrical cuff catheter, the target pressure should be set at 25-30 cmH2O, and the cuff pressure should be adjusted regularly.

The alpha-2A-adrenergic receptor gene polymorphism modulates gray matter structural networks, visual memory, and inhibitory cognitive control in children with attention deficit/hyperactivity disorder.

The ADRA2A-1291 C > G polymorphism and deficits in visual memory and inhibitory control were associated with attention deficit hyperactivity disorder (ADHD). The present study aimed to examine whether the ADRA2A G/G genotype affected gray matter (GM) networks in ADHD and whether these gene-brain modulations were associated with cognitive function in ADHD. Seventy-five drug-naïve ADHD children and 70 healthy controls were recruited. The GM networks were obtained based on areal similarities of GM, and network topological properties were analyzed using graph theory. Visual memory and inhibitory control were assessed by the visual memory test and the Stroop test, respectively. SNP genotyping of rs1800544 was performed. A significant interaction between ADHD diagnosis and gene polymorphism was observed in the nodal degree of the left inferior parietal lobule and left inferior (opercular) frontal gyrus. In the ADHD group, nodal efficiency in the left inferior (orbital) frontal gyrus in ADHD with G/G was lower than that in ADHD without G/G. Moreover, the ADRA2A-modulated alterations in nodal properties were associated with visual memory and inhibitory control. Our findings provide novel gene-brain behavior association evidence that GM network alterations, especially in the frontoparietal loop, were related to visual memory and inhibitory control in ADHD children with ADRA2A-G/G.

[Application study on improving the methods of endotracheal cuff pressure measurement to prevent ventilator-associated pneumonia].

OBJECTIVE: To compare the intra cuff pressure changes during improved and the traditional method of cuff pressure measurement, then evaluate the effects of ventilator-associated pneumonia (VAP) prevention. The results highlighted practical recommendations in the process of ETT cuff pressure measurement. METHODS: (1) Experimental studies were carried out on the tracheal model with two groups: traditional pressure measurement group and improved pressure measurement group. The traditional pressure measurement group was connected to a handheld pressure gauge with the indicate cuff to get the intra-cuff pressure. The improved method was to insert a 3-way stopcock between the handheld pressure gauge and the indicate cuff. The 3-way stopcock to stabilize handheld pressure gauge reading at 32 cmH2O (1 cmH2O = 0.098 kPa) before measure the intra-cuff pressure. The pressure loss caused by two pressure measurement methods and the leakage of liquid on the balloon after 10 minutes was compared. (2) Clinical researches: a historic cohort study, patients with mechanical ventilation (MV) admitted to intensive care unit (ICU) of Guangxi Medical University Cancer Hospital from June 2014 to May 2018 were enrolled. The control group (249 cases) was treated with traditional method during June 2014 to May 2016, and the observation group (314 cases) was treated with improved method during June 2016 to May 2018. Clusters of strategies and actions of VAP prevention were applied in both groups. Incidence of VAP, duration of MV, and the length of ICU stay were compared between the two groups. RESULTS: (1) Experimental study: the pressure leakage of the traditional pressure measurement group was (10.18±0.47) cmH2O, and that of the improved pressure measurement group was (1.33±0.42) cmH2O, with statistically significant difference between the two groups (t = 32.535, P = 0.000). All fluid on the cuffs leak after 10 minutes of traditional ways of measurement, however, no visible fluid on the cuffs leaked with improved procedures. (2) Clinical research: the incidence of VAP in the observation group was slightly lower than that in the control group, however there was no significant difference [5.10% (16/314) vs. 8.43% (21/249), P > 0.05]. The duration of MV and the length of ICU stay in the observation group were significantly shorter than those in the control group (days: 9.93±3.14 vs. 16.77±5.45, 11.63 ±2.28 vs. 19.12±5.10, both P < 0.01). CONCLUSIONS: The improved procedures of intra-cuff pressure measurement is a practical method to avoid the pressure leakage and fluid leakage, and the clinical course of MV patients can be significantly improved by combining the clusters of nursing strategies and actions.

Anti-diarrhoeal and anti-microbial activity of Flos populi (male inflorescence of Populus tomentosa Carrière) aqueous extracts.

ETHNOPHARMACOLOGICAL RELEVANCE: Flos populi (male inflorescence of Populus tomentosa Carrière) has been traditionally used in East Asian countries for the treatment of various inflammatory diseases, strengthening the spleen and stomach, anti-rheumatic, anti-tumor and anti-diarrhoeal. AIM OF THE STUDY: To evaluate the in vivo or in vitro anti-diarrhoeal and anti-microbial activity of Flos populi aqueous extract. MATERIALS AND METHODS: Acute toxicity of Flos populi aqueous extract (FPAE) was investigated. Castor oil-induced diarrhoea method was used to evaluate the anti-diarrhoeal activity, inhibition of defecation and diarrhoea were determined in mice, effects on castor oil-induced enteropooling, intestinal transit and intestinal fluid secretion in rats or mice. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of FPAE against strains of three clinical bacterial isolates and one reference strain were used to test the anti-microbial activity. RESULTS: The FPAE reduced the frequency of diarrhoea episodes and decreased the propulsion of charcoal meal through the gastrointestinal tract in a dose dependent manner. FPAE (100-500 mg/kg, p.o.) produced dose-dependent and significant (P<0.01) protection of mice against castor oil-induced diarrhoea. FPAE, dose-dependently and significantly (P< 0.01) delayed the onset of castor-oil induced diarrhoea, decreased the frequency of defecation, and reduced the severity of diarrhoea. Compared with control animals, FPAE, dose-dependently and significantly (P< 0.01) decreased the volume of castor oil-induced intestinal fluid secretion, and reduced the number, weight and wetness of faecal droppings. There was no deaths or abnormalities in behaviour seen in the acute toxicity test. The aqueous extract displayed anti-microbial effects to three species of bacteria in anti-microbial test. CONCLUSION: The findings of this study indicate that FPAE possesses anti-diarrhoeal property in rats and mice and confirm the ethnomedicinal use of Flos Populi as a valuable natural remedy for the treatment, management and/or control of diarrhoea. These results may support the fact that this plant is traditionally used to cure diarrhoea.

A continuous perfusion microplate for cell culture.

We describe a 96-well microplate with fluidically connected wells that enables the continuous fluid perfusion between wells without the need for external pumping. A single unit in such a perfusion microplate consists of three wells: a source well, a sample (cell culture) well in the middle and a waste well. Fluid perfusion is achieved using a combination of the hydrostatic pressure generated by different liquid levels in the wells and the fluid wicking through narrow strips of a cellulose membrane connecting the wells. There is an excellent correspondence between the observed perfusion flow dynamics and the flow simulations based on Darcy's Law. Hepatocytes (C3A cells) cultured for 4 days in the perfusion microplate with no media exchange in the cell culture well had the same viability as hepatocytes exposed to a daily exchange of media. EOC 20 cells that require media conditioned by LADMAC cells were shown to be equally viable in the adjacent cell culture well of the perfusion microplate with LADMAC cells cultured in the source well. Tegafur, a prodrug, when added to primary human hepatocytes in the source well, was metabolized into a cytotoxic metabolite that kills colon cancer cells (HCT 116) cultured in the adjacent cell culture well; no toxicity was observed when only medium was in the source well. These results suggest that the perfusion microplate is a useful tool for a variety of cell culture applications with benefits ranging from labor savings to enabling in vivo-like toxicity studies.

Dynamic simulation of droplet interaction and self-assembly in a nematic liquid crystal.

We use dynamic simulations to explore the pairwise interaction and multiparticle assembly of droplets suspended in a nematic liquid crystal. The computation is based on a regularized Leslie-Ericksen theory that allows orientational defects. The homeotropic anchoring on the drop surface is of sufficient strength as to produce a satellite point defect near the droplet. Based on the position of the defects relative to the host droplet and the far-field molecular orientation, we have identified five types of pairwise attractive and repulsive forces. In particular, long-range attraction between two droplets with their line of centers along the far-field orientation decays as R-4, with R being the center-to-center separation. This agrees with prior static calculations and a phenomenological model that treats the attraction as that between two dipoles. For interaction in shorter ranges, our simulations agree qualitatively with experimental measurements and static calculations. However, there is considerable quantitative discrepancy among the few existing studies and our simulation. We suggest that this is partly due to the dynamic nature of the process, which has never been taken into account in prior calculations. Multidrop simulations show the formation of linear chains through pairwise interactions between nearby droplets. Parallel chains repel or attract each other depending on the relative orientation of the drop-to-defect vector. These are consistent with experimental observations of chain formation and two-dimensional self-assembly in bulk nematics and smectic-C films.

Simulation of neutrophil deformation and transport in capillaries using newtonian and viscoelastic drop models.

It is well known that neutrophils take much longer to traverse the pulmonary capillary bed than erythrocytes, and this is likely due to differences in the structure and rheology of the cells. In this study, we simulate the transit of a neutrophil in a capillary using a Newtonian drop model and a viscoelastic drop model. The cell membrane is represented by an interface with isotropic and constant tension, and the cell motion and deformation are described by a phase-field method. The governing equations are solved using finite elements in an axisymmetric geometry, and the thin interfaces are resolved by mesh adaptivity. With a fixed pressure drop, the entry of a cell into a capillary consists of several stages in which the flow rate varies in distinct manners. The entrance time is consistent with experimental measurements. It decreases with the pressure drop, increases with the cell viscosity and generally decreases with the relaxation time of a viscoelastic cytoplasm. The capillary geometry has a strong effect on the entry and transit of a neutrophil. The entrance time increases sharply when the capillary diameter decreases or when the capillary is constricted by a pinch.

Dynamic evolution of topological defects around drops and bubbles rising in a nematic liquid crystal.

We report observations of topological defects around drops and bubbles that rise through a vertically aligned nematic liquid crystal. We provide direct evidence for downstream convection of the Saturn-ring defect and its transformation to a hyperbolic point defect. The point defect is convected further in the wake of the drop or bubble as the rising velocity increases. In equilibrium, both defect configurations may persist for long times in the narrow cell. But the point defect sometimes spontaneously opens into a Saturn ring, indicating the latter as the globally stable configuration in the presence of tight wall confinement.