Effects of Thermal Softening of Double-Lumen Endobronchial Tubes on the Prevention of Postoperative Sore Throat in Smokers: A Randomized Controlled Trial.

OBJECTIVE: Tracheal intubation-related complications, such as postoperative sore throat (POST), hoarseness, and vocal cords injuries, are not uncommon. It is well known that thermal softening of double-lumen endobronchial tubes (DLTs) has been used to prevent these events from happening in non-smokers; however, no study has ever assessed the effects of thermal softening of DLTs in smokers undergoing one-lung anesthesia. The authors aimed to investigate whether thermal softening of DLT can achieve a better effect in preventing POST. DESIGN: A total of 258 smokers scheduled for one-lung anesthesia were randomly assigned to 1 of the following 2 groups: (1) group C (non-thermal softening group) and (2) group T (DLTs were placed in 40°C 0.9% saline for 10 minutes). Incidence and severity of POST and hoarseness were assessed until 48 hours after surgery. Vocal cords were examined using laryngoscope before intubation and immediately after extubation. Patients' hemodynamic change at intubation and extubation was recorded. The primary outcomes were the incidence and severity of POST. The secondary outcomes were the incidence and severity of hoarseness, vocal cords injuries, and patients' hemodynamic change at intubation and extubation. MEASUREMENTS AND MAIN RESULTS: Sore throat and vocal cord injuries occurred less frequently in the thermal softening group than in the control group (31/129 v 60/129, p < 0.01; 21/129 v 49/129, p < 0.001; 12/129 v 35/129, p < 0.001 for sore throat; 14/70 v 27/70, risk ratio (95% confidence interval): 0.52 (0.30-0.90), p = 0.025 for sore throat; 5/129 v 52/129, p < 0.05 for vocal cord injuries). CONCLUSION: Thermal softening of DLTs significantly reduced the incidence and severity of DLTs intubation-related POST within 72 hours after extubation.

Dynamics of erythrocytes in oscillatory shear flows: effects of S/V ratio.

By combining a multiscale structural model of erythrocyte with a fluid-cell interaction model based on the boundary-integral method, we numerically investigate the dynamic response of erythrocytes in oscillatory shear flows (OSFs). The goal is to develop a novel experimental method to test the structural robustness of erythrocytes in transient mechanical loads with small time scales, conditions closely imitating the mechanical environment in vivo. Following the discovery of multiple response modes (wheeling, mode 1 tank treading, and mode 2 tank treading) under these conditions (Zhu & Asaro, 2019), we concentrate on deformation and stress inside RBCs driven by OSF, especially shear deformation of the membrane and the skeleton-bilayer dissociation stress, parameters that are related to mechanically induced structural remodeling such as vesiculation. Effects related to changes in surface area-to-volume (S/V) ratio are considered. Our results show that with the variation of the S/V ratio there could be significant change in terms of the occurrence of response modes even if other parameters are kept unchanged. For example, by reducing the S/V ratio of the cell, an asymmetric mode featuring a mixture of the wheeling and mode 2 tank treading responses is discovered. This mode is found to be associated with large skeleton-bilayer dissociation stress so that its potential impact on OSF-driven vesiculation should not be overlooked. By systematically examining the dependencies of skeleton deformation and skeleton-bilayer dissociation stress upon S/V, this study is critical for the development of the OSF technique in applications such as diagnosis since cell conditions are often reflected in its geometric properties.

[Effects of repeated sevoflurane exposure on hippocampal cell apoptosis and long-term learning and memory ability in neonatal rats].

Objective: To investigate the effects of repeated sevoflurane exposure on hippocampal cell apoptosis and long-term learning and memory ability in neonatal rats and its regulation on PI3K/AKT pathway. Methods: Ninety SD rats were randomly divided into the control group (25% oxygen), the single exposure group (inhalation of 3% sevoflurane and 25% oxygen on the 6th day after birth), the 3-times exposure group (inhalation of 3% sevoflurane and 25% oxygen on the 6th, 7th, and 8th day after birth), the 5-times exposure group (inhalation of 3% sevoflurane and 25% oxygen on the 6th, 7th, 8th, 9th and 10th day after birth), and the 5-times exposure + 740Y-P (PI3K activator) group (intraperitoneal injection of 0.02 mg/kg 740Y-P after inhalation of sevoflurane for 5 times) according to the random number table method. Morris water maze was used to measure the learning and memory ability; HE staining and transmission electron microscopy were used to observe the morphological and structural changes of neurons in the hippocampus; TUNEL was used to detect the apoptosis of hippocampal nerve cells; Western blot was used to detect the expressions of apoptosis-related proteins (Caspase-3, Bax, Bcl-2) and PI3K/AKT pathway related proteins in the hippocampus of rats. Results: Compared with the control group and the single exposure group, the learning and memory abilities of rats in the 3-times exposure group and the 5-times exposure group were severely reduced, the morphology and structure of hippocampal neurons were severely damaged, and the apoptosis rate of hippocampal nerve cells was increased (P＜0.05), the expressions of Capase-3 and Bax proteins were significantly increased (P＜0.05), and the expressions of Bcl-2 protein and PI3K/AKT pathway protein were significantly decreased (P＜0.05). With the increase in the number of exposures to sevoflurane, the learning and memory abilities of rats were significantly reduced, the hippocampal neuron cells were severely damaged, the hippocampal neuronal apoptosis rate was significantly increased (P＜0.05), and the expressions of PI3K/AKT pathway proteins were significantly reduced (P＜0.05). Compared with the 5-times exposure group, the learning and memory abilities and hippocampal neuron structure of rats in the 5-times exposure +740Y-P group were restored to a certain extent, and the hippocampal neuronal apoptosis rate, the levels of capase-3 and Bax protein were significantly reduced (P＜0.05), while the expressions of Bcl-2 protein and PI3K/AKT pathway protein were increased significantly (P＜0.05). Conclusion: Repeated exposure to sevoflurane can significantly reduce the learning and memory abilities of neonatal rats and exacerbate hippocampal neuronal apoptosis, which may be mediated by inhibiting the PI3K/AKT pathway.

Free swimming of a squid-inspired axisymmetric system through jet propulsion.

An axisymmetric fluid-structure interaction model based on the immersed-boundary approach is developed to study the self-propelled locomotion of a squid-inspired swimmer in relatively low Reynolds numbers (O(102)). Through cyclic deformation, the swimmer generates intermittent jet flow, which, together with the added-mass effect associated with the body deformation, provides thrust. Through a control volume analysis we are able to determine the jet-related thrust. By adding it to the added-mass-related thrust we separate the net thrust on the body from the drag effect due to forward motion, so that the propulsion efficiency in free swimming is found. This numerical algorithm and thrust-drag decomposition method are used to study the dynamics of the bio-inspired locomotion system in different conditions, whereby the performance is characterized by the aforementioned propulsion efficiency as well as the conventionally defined cost of transport.

Effects of dexmedetomidine on neurocognitive disturbance after elective non-cardiac surgery in senile patients: a systematic review and meta-analysis.

OBJECTIVE: Senile patients often experience neurocognitive disturbance after non-cardiac surgery. Several clinical trials have investigated if the perioperative intravenous use of dexmedetomidine has a positive effect on the prevention of neurocognitive dysfunction, but the results have been inconsistent. We performed a meta-analysis to investigate the effects of dexmedetomidine on neurocognitive disturbance after elective non-cardiac surgery in senile patients. METHODS: The PubMed, Cochrane Library, EMBASE and China National Knowledge Infrastructure databases were comprehensively searched for all randomized controlled trials published before 1 February 2020 that investigated the efficacy of dexmedetomidine in the prevention of postoperative delirium (POD) or postoperative cognitive dysfunction (POCD). RESULTS: Sixteen studies involving 4376 patients were included in this meta-analysis. Compared with the control (i.e., saline), the perioperative intravenous use of dexmedetomidine significantly reduced the incidence of POD and POCD. However, patients in the dexmedetomidine group were more likely to develop bradycardia and hypotension during the administration of dexmedetomidine than patients in the control group. There were no differences between the two groups in the incidence of nausea and vomiting or mortality rate. CONCLUSION: Dexmedetomidine has a positive effect on the prevention of neurocognitive disturbance in senile patients after elective non-cardiac surgery.

Cephalopod-inspired robot capable of cyclic jet propulsion through shape change.

The compliance and conformability of soft robots provide inherent advantages when working around delicate objects or in unstructured environments. However, rapid locomotion in soft robotics is challenging due to the slow propagation of motion in compliant structures, particularly underwater. Cephalopods overcome this challenge using jet propulsion and the added mass effect to achieve rapid, efficient propulsion underwater without a skeleton. Taking inspiration from cephalopods, here we present an underwater robot with a compliant body that can achieve repeatable jet propulsion by changing its internal volume and cross-sectional area to take advantage of jet propulsion as well as the added mass effect. The robot achieves a maximum average thrust of 0.19 N and maximum average and peak swimming speeds of 18.4 cm/s (0.54 body lengths/s) and 32.1 cm/s (0.94 BL/s), respectively. We also demonstrate the use of an onboard camera as a sensor for ocean discovery and environmental monitoring applications.

Dynamics of a squid-inspired swimmer in free swimming.

The untethered swimming performance of a two-dimensional squid-inspired swimmer is studied. Our model includes fully-coupled fluid-structure interaction and an idealized activation algorithm that drives periodic shape change of the body. We present results of both escape jetting via a single deflation-coasting motion and long-distance swimming via repeated inflation-deflation cycles. In both cases added-mass-related force is found to contribute significantly to thrust generation. Moreover, we find that the increase of the jet speed and oscillation frequency leads to higher swimming velocity. This, however, is achieved at the cost of reduced propulsion efficiency (i.e. higher cost of transport). During long-distance swimming, the system experiences three successive stages, acceleration, steady-state swimming, and off-track swimming caused by symmetry-breaking instability in the wake. Associated with these stages, three wake patterns are observed, nozzle-vortex-dominated wake, transit wake, and asymmetrical wake.

Numerical investigation of cephalopod-inspired locomotion with intermittent bursts.

Inspired by recent studies about the fluid dynamics of cephalopods in their escaping swimming mode, we propose a novel design of an underwater propulsion system using a deformable body with pressure chamber, which propels itself in burst-coast cycles through a combined effect of pulsed jet and added-mass related thrust. To investigate the performance of this system we create a free-swimming computational model-the body deformation is prescribed yet the forward motion is driven by hydrodynamic forces. Our focus is on a single bursting cycle, which corresponds to the case that the system rests between bursts. The results can also be applied to the starting stage of a continuous cruising motion. A numerical model using the boundary element method is developed to computationally study the swimming process and the dynamic characteristics of this system. The results show that in the bursting phase its peak speed depends on the size of the body, the deformation time, the amount of volume change during the deformation, and the size of the nozzle where the jet flow is generated. The optimal speed is found to coincide with the critical formation number, indicating that the formation of vortex rings in the wake plays a pivotal role in the dynamics of the system. The dynamics of the system in the coasting phase and the process of refilling the pressure chamber are also studied.

Effects of stiffness distribution and spanwise deformation on the dynamics of a ray-supported caudal fin.

Using a fluid-structure interaction model, we study the effect of ray stiffness distribution on the deformation and performance of a caudal fin. By prescribing a simple swaying motion, our results show that through passive structural deformation alone it is possible to reproduce some complicated fin movements (e.g. the cup and 'W'-shape deformations) observed in real fish. Moreover, it has been numerically shown that, compared with a fin with uniform ray stiffness, at the same (average) ray stiffness fins with nonuniform stiffness distribution may achieve further performance enhancement, e.g. increase in propulsion efficiency and decrease in lateral force generation. This is attributed to spanwise deformations caused by phase differences between different rays.