Search

Background and Aims: Various methods are used to predict the depth of insertion of central venous catheters (CVCs). We evaluated a bronchoscopy-based carinal measurement technique to predict this depth. Methods: We randomised adults undergoing cardiac surgery into a bronchoscopy group or the Peres' formula-based method group. CVCs were inserted through the right internal jugular vein. The skin insertion reference point was at the level of the cricoid cartilage lateral to the carotid artery. In the bronchoscopy group, the depth of insertion was determined by the total length from the carina to the proximal end of the tracheal tube (TT) (measured with a flexible bronchoscope) minus (the sum of the distances from the skin insertion reference point to the TT and the length of the TT outside the mouth). In the Peres' group, height (cm)/10 determined the depth of insertion. Confirmation of CVCs' distal tip position was done with transoesophageal echocardiography. The area from 2 cm proximal to 1 cm distal to the superior vena cava-right atrium junction was considered ideal. The primary outcome was the proportion of correct CVC placements. The secondary outcome was the alignment of the CVCs. Results: Forty-one patients in the bronchoscopy group and 40 patients in the Peres' group were enroled. A greater proportion of CVCs was placed correctly in the bronchoscopy group (87.8% vs. 37.5%; P = 0.001). A more significant proportion of CVC tips was abutting the vessel wall in the Peres' group (45% vs. 19.5%; P = 0.014). Conclusion: Bronchoscopy-based carinal measurement technique results in more accurate placement of CVCs compared to the Peres' method. Keywords: Bronchoscopy, central venous catheters, chest X-ray, depth, radiology, Author(s): Satyajeet Misra (corresponding author) [1]; Prasanta K. Das [1]; Bikram K. Behera [1]; Devishree Das [1]; Tarun K. Patra [1] INTRODUCTION Adequate depth of insertion of central venous catheters [...]

The thermocapillary flow of multiple liquid layers over contoured substrates finds applications in many industrial phenomena via micro-electromechanical systems/nano-electromechanical systems devices. This study theoretically explores the thermocapillary transport of binary-liquid layers in a wavy microchannel with serpentine wall profiles. Sinusoidal profiles are considered for the microchannel walls' temperature and surface topology. Patterned slip conditions at the walls are also accounted for in the analysis to make the problem more realistic. We semi-analytically solve the energy and momentum equations to understand the system's thermal and hydrodynamic characteristics for the limiting conditions of M a , R e , and C a. The leading- and higher-order solutions of the temperature and flow field are separately shown to demonstrate the advection terms' contribution to the transport equations. The circulatory flow obtained due to periodic thermal stimuli can be used to enhance the mixing efficiency of the system. We also present how the parameters like phase difference between the thermal stimulus, relative thermal conductivity, and relative film thickness ratio of the liquid layers can be altered to control the flow characteristics to obtain the most potent thermocapillary effect. [ABSTRACT FROM AUTHOR]

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease. There are a few reports of uncorrected TOF patients surviving into adulthood requiring noncardiac surgery. They are commonly susceptible to developing brain abscesses due to paradoxical embolism and lack of pulmonary phagocytic clearance. A 32-year-old man, a known patient of TOF with pulmonary atresia and major aortopulmonary collateral arteries, presented with left side weakness and seizures. He was drowsy with a Glasgow Coma Scale (GCS) of 13/15, heart rate of 72/min, oxygen saturation of 78% with 6 L/min oxygen via face mask, and blood pressure of 90/60 mm Hg with noradrenaline at 0.5 mcg/kg/min. He had central cyanosis, clubbing, and icterus. The left upper and lower limb power was 2/5, whereas it was 5/5 for the right. Cardiovascular examination revealed a grade 3/6 continuous murmur at the base of the heart. No pulmonary abnormality was noted on auscultation. Echocardiography showed large subaortic ventricular septal defect (VSD) with overriding of the aorta, pulmonary atresia, right-sided aortic arch, and ejection fraction of 62%. Magnetic resonance imaging (MRI) of the brain revealed features suggestive of brain abscess. Brain abscess drainage was performed under scalp block with sedation to avoid major hemodynamic fluctuations. The procedure was uneventful, and the patient's power on the left side improved postprocedure. Scalp block with sedation is a suitable alternative to general anesthesia for drainage of brain abscess in TOF patients. [ABSTRACT FROM AUTHOR]

The effect of contact line pinning on nucleation is reported using continuum thermodynamics. Based on the principle of the free-energy maximization, closed-form expressions in the dimensionless form for the free-energy of the three-phase metastable system and the thermodynamic barrier are formulated with respect to the system geometry and the substrate wettability. The condition of maximality limits the dynamic contact angle within the cluster-phase-phobic regime. The dimensionless nucleation barrier or the potency factor can be divided into two components related to the system geometry and the pinning effect. Depending on the relative value of the equilibrium and the critical dynamic contact angle, the contact line pinning can either have favorable or adverse effects. Associated pinningdepinning transition can also lead to the crossovers related to barrierless and homogeneous nucleation. Contact line tension is found to have a considerable effect during these transitional scenarios. Complete wetting transition associated with barrierless nucleation can take place due to the presence of tensile (negative) line tension. On the other hand, complete drying transition related to homogeneous nucleation can occur when line tension is compressive (positive) in nature. The pinning has a favorable effect only when the substrate wettability is within the cluster-phase-philic regime. There can be favorable, adverse, or no pinning effects when the substrate wettability is within the clusterphase- phobic regime. Although the contact line is pinned, the minimum value of the potency factor is obtained when equilibrium and dynamic contact angles are equal. [ABSTRACT FROM AUTHOR]

Within the framework of the classical theory of heterogeneous nucleation, a thermokinetic model is developed for line-tension-associated droplet nucleation on conical textures considering growth or shrinkage of the formed cluster due to both interfacial and peripheral monomer exchange and by considering different geometric configurations. Along with the principle of free energy extremization, Katz kinetic approach has been employed to study the effect of substrate conicity and wettability on the thermokinetics of heterogeneous water droplet nucleation. Not only the peripheral tension is found to have a considerable effect on the free energy barrier but also the substrate hydrophobicity and hydrophilicity are observed to switch over their roles between conical crest and trough for different growth rates of the droplet. Besides, the rate of nucleation increases and further promotes nucleation for negative peripheral tension as it diminishes the free energy barrier appreciably. Moreover, nucleation inhibition can be achievable for positive peripheral tension due to the enhancement of the free energy barrier. Analyzing all possible geometric configurations, the hydrophilic narrower conical cavity is found to be the most preferred nucleation site. These findings suggest a physical insight into the context of surface engineering for the promotion or the suppression of nucleation on real or engineered substrates. [ABSTRACT FROM AUTHOR]

A rigorous thermodynamic formulation of the geometric model for heterogeneous nucleation including line tension effect is missing till date due to the associated mathematical hurdles. In this work, we develop a novel thermodynamic formulation based on Classical Nucleation Theory (CNT), which is supposed to illustrate a systematic and a more plausible analysis for the heterogeneous nucleation on a planar surface including the line tension effect. The appreciable range of the critical microscopic contact angle (θc), obtained from the generalized Youngâ€s equation and the stability analysis, is θ∞ < θc < θ†for positive line tension and is θM < θc < θ∞ for negative line tension. θ∞ is the macroscopic contact angle, θ†is the contact angle for which the Helmholtz free energy has the minimum value for the positive line tension, and θM is the local minima of the nondimensional line tension effect for the negative line tension. The shape factor f, which is basically the dimensionless critical free energy barrier, becomes higher for lower values of θ∞ and higher values of θc for positive line tension. The combined effect due to the presence of the triple line and the interfacial areas (ƒL + ƒS) in shape factor is always within (0, 3.2), resulting ƒ in the range of (0, 1.7) for positive line tension. A formerly presumed appreciable range for θc (0 < θc < θ∞) is found not to be true when the effect of negative line tension is considered for CNT. Estimation based on the property values of some real fluids confirms the relevance of the present analysis. [ABSTRACT FROM AUTHOR]

The micellization behavior of cetylammonium bromide and its mono-, di-, and trihydroxyethylated group analogues and water/oil (w/o) microemulsion formation with them were studied with detailed thermodynamic and structural considerations. The transfer of n-hexanol from oil to the droplet interface was exothermic in nature and the C3/n-hexanol/isoctane bearing microemulsion is more convenient for enzyme accommodation at the interface to augment better catalytic activity.

We propose dielectrophoretic force driven coalescence of droplets having equal or nonequal sizes with an electrode base actuation system over a solid surface. Coupled electrohydrodynamic conservation equations are solved to simulate the phenomenon based on finite volume scheme. Volume of fluid technique is used to capture the interface. Electric potential and dissimilarity index are varied to comprehend the coalescence dynamics. The interplay between the capillary and electrostatic influences during the coalescence is analyzed by tracking the dimension of the liquid connection formed at the onset of fusion. Efforts have been made to characterize the liquid bridge formation as a function of inertia normalized time scale. The capillary force showed higher dominance in the initial period of agglomeration. The electrostatic influence can be perceived at the latter stages of the growth of liquid connection. Directional predilection in the flow field is observed during the coalescence of dissimilar droplets. © 2018 American Institute of Chemical Engineers AIChE J, 65: 829–839, 2019 [ABSTRACT FROM AUTHOR]

Liquid flows over patterned and/or contoured substrates is utilized in many practical applications e.g., lubrication flow in MEMS (micro-electromechanical systems) /NEMS (nano-electromechanical systems) devices, cell sorting operations in biology, etc. The topological gradients in such geometries induce thermal gradients, which in turn generates Marangoni hydrodynamics. Here, we theoretically showcase the interplay of substrate topology, imposed wavy temperature stimulus, and chemically patterned wall slip to generate thermo-capillarity in thin liquid films. We obtain analytical solutions for the thermal and the hydrodynamic fields for low Marangoni Ma and Reynolds Re number thermocapillary effect. Vorticity is observed to generate and transport at the liquid-gas interface, and further transported to the bulk film by vertical diffusion and convection. We also study further to understand the significance of different geometric and physical parameters on the Marangoni thermo-fluid-dynamics. Interplay of constructive and destructive interference between the wave forms of the substrate topology and imposed periodic thermal stimulus may yield maximum interfacial temperature gradients and strong thermo-capillarity. It is also observed that the lower values of system Biot number Bi enables better diffusion of heat from the patterned substrate to obtain stable thermo-capillarity. Further, the presence of optimal slip patterning allows for stronger and tuned circulations in the liquid film. [ABSTRACT FROM AUTHOR]