Endotracheal Tube Cuff Pressures in Adult Patients Undergoing General Anaesthesia in Two Johannesburg Academic Hospitals

Background: Endotracheal tube (ETT) cuff pressure commonly exceeds the recommended range of 20–30 cm H₂O during anaesthesia. A set volume of air will not deliver the same cuff pressure in each patient and the pressure exerted by the ETT cuff can lead to complications, with either over- or under-inflated cuffs. These can include a sore throat and cough, aspiration, volume loss during positive pressure ventilation, nerve palsies, tracheomalacia and tracheal stenosis. No objective means of ETT cuff pressure monitoring is available in the operating theatres of Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) and Chris Hani Baragwanath Academic Hospital (CHBAH). The ETT cuff pressure of patients undergoing general anaesthesia is therefore unknown.Method: ETT cuff pressure of 96 adult patients undergoing general anaesthesia without nitrous oxide at CMJAH and CHBAH was measured by one researcher. A RUSCH Endotest™ manometer was used to measure ETT cuff pressure in size 7.0 – 8.5 mm ETTs. The cuff inflation technique that was used by the anaesthetist was also documented.Results: The mean ETT cuff pressure recorded was 47.5 cm H₂O (range 10–120 cm H₂O). ETT cuff pressures exceeded 30 cm H₂O in 64.58% of patients. Only 18.75% of patients had ETT cuff pressures within the recommended range of 20–30 cm H₂O. There was no statistically significant difference between the ETT cuff pressures measured at the two hospitals. Minimal occlusive volume was the most frequent technique used to inflate the ETT cuff (37.5%); this was followed by inflating the ETT cuff with a predetermined volume of air in 31.25% of cases and palpation of the pilot balloon (27.08%). There was no statistically significant difference between the ETT cuff pressure measured and the inflation technique used by the anaesthetist.Conclusion: ETT cuff pressures of the majority of patients undergoing general anaesthesia at two academic hospitals were higher than the recommended range. ETT cuff pressure should routinely be measured using a manometer.Keywords: Adults, Endotracheal Tube Cuff Pressures, General Anaesthesia, Manomete

Rapid and scale-independent microfluidic manufacture of liposomes entrapping protein incorporating in-line purification and at-line size monitoring

Within this paper we present work that has the ability to de-risk the translation of liposomes from bench to the clinic. We have used microfluidics for the rapid and scale-independent manufacture of liposomes and have incorporated in-line purification and at-line monitoring of particle size. Using this process, we have manufactured a range of neutral and anionic liposomes incorporating protein. Factors investigated include the microfluidics operating parameters (flow rate ratio (FRR) and total flow rate (TFR)) and the liposome formulation. From these studies, we demonstrate that FRR is a key factor influencing liposome size, protein loading and release profiles. The liposome formulations produced by microfluidics offer high protein loading (20–35%) compared to production by sonication or extrusion (<5%). This high loading achieved by microfluidics results from the manufacturing process and is independent of lipid selection and concentration across the range tested. Using in-line purification and at-line size monitoring, we outline the normal operating range for effective production of size controlled (60–100 nm), homogenous (PDI <0.2) high load liposomes. This easy microfluidic process provides a translational manufacturing pathway for liposomes in a wide-range of applications

Silk nanoparticle manufacture in semi-batch format

Silk nanoparticles have demonstrated utility across a range of biomedical applications, especially as drug delivery vehicles. Their fabrication by bottom-up methods such as nanoprecipitation, rather than top-down manufacture, can improve critical nanoparticle quality attributes. Here, we establish a simple semi-batch method using drop-by-drop nanoprecipitation at the lab scale that reduces special-cause variation and improves mixing efficiency. The stirring rate was an important parameter affecting nanoparticle size and yield (400 < 200 < 0 rpm), while the initial dropping height (5.5 vs 7.5 cm) directly affected nanoparticle yield. Varying the nanoparticle standing time in the mother liquor between 0 and 24 h did not significantly affect nanoparticle physicochemical properties, indicating that steric and charge stabilizations result in high-energy barriers for nanoparticle growth. Manufacture across all tested formulations achieved nanoparticles between 104 and 134 nm in size with high β-sheet content, spherical morphology, and stability in aqueous media for over 1 month at 4 °C. This semi-automated drop-by-drop, semi-batch silk desolvation offers an accessible, higher-throughput platform for standardization of parameters that are difficult to control using manual methodologies

Design and development of novel screen-printed microelectrode and microbiosensor arrays fabricated using ultrafast pulsed laser ablation

© 2016 Elsevier B.V. All rights reserved. A new generic platform for the development of microbiosensors combining screen-printing and ultrafast pulsed laser technologies has been developed, characterised and evaluated. This new platform consists of a layer of screen-printed carbon ink containing the enzyme and mediator, covered with an insulating layer formed from a dielectric screen printed ink. Microholes were drilled through the insulated layer by ultrafast pulsed laser ablation to generate the microbiosensor array. The geometry of the microelectrode array was evaluated by optical microscopy, white light surface profiling and scanning electron microscopy. The electrochemical behaviour of the microelectrode array was characterised by cyclic voltammetry and compared with macroelectrodes. The analytical performance of the microbiosensor array was evaluated with external counter and reference electrodes for hydrogen peroxide and glucose determination showing linearity up to 4 mmol L-1 and 20 mmol L-1 (360 mg dL-1) respectively. The full screen printed three-electrode configuration shows linearity for glucose determination up to 20 mmol L-1 (360 mg dL-1). This study provides a new fabrication method for microelectrode and microbiosensor arrays capable for the first time to retain the activity of the enzymatic system after processing by pulse laser ablation

Volumetric scalability of microfluidic and semi-batch silk nanoprecipitation methods

Silk fibroin nanoprecipitation by organic desolvation in semi-batch and microfluidic formats provides promising bottom-up routes for manufacturing narrow polydispersity, spherical silk nanoparticles. The translation of silk nanoparticle production to pilot, clinical, and industrial scales can be aided through insight into the property drifts incited by nanoprecipitation scale-up and the identification of critical process parameters to maintain throughout scaling. Here, we report the reproducibility of silk nanoprecipitation on volumetric scale-up in low-shear, semi-batch systems and estimate the reproducibility of chip parallelization for volumetric scale-up in a high shear, staggered herringbone micromixer. We showed that silk precursor feeds processed in an unstirred semi-batch system (mixing time > 120 s) displayed significant changes in the nanoparticle physicochemical and crystalline properties following a 12-fold increase in volumetric scale between 1.8 and 21.9 mL while the physicochemical properties stayed constant following a further 6-fold increase in scale to 138 mL. The nanoparticle physicochemical properties showed greater reproducibility after a 6-fold volumetric scale-up when using lower mixing times of greater similarity (8.4 s and 29.4 s) with active stirring at 400 rpm, indicating that the bulk mixing time and average shear rate should be maintained during volumetric scale-up. Conversely, microfluidic manufacture showed high between-batch repeatability and between-chip reproducibility across four participants and microfluidic chips, thereby strengthening chip parallelization as a production strategy for silk nanoparticles at pilot, clinical, and industrial scales

Correction : Mixing and flow-induced nanoprecipitation for morphology control of silk fibroin self-assembly

Correction for ‘Mixing and flow-induced nanoprecipitation for morphology control of silk fibroin self-assembly’ by Saphia A. L. Matthew et al., RSC Adv., 2022, 12, 7357–7373. https://doi.org/10.2039/D1RA07764C. The authors regret that there were sub-figure placement errors present in Fig. 4 and 5 of the main article. The sub-figure placement error in Fig. 4 was carried into Fig. S3, which shows additional statistical significances. The corrected figures are shown below

Mixing and flow-induced nanoprecipitation for morphology control of silk fibroin self-assembly

Tuning silk fibroin nanoparticle morphology using nanoprecipitation for bottom-up manufacture is an unexplored field that has the potential to improve particle performance characteristics. The aim of this work was to use both semi-batch bulk mixing and micro-mixing to modulate silk nanoparticle morphology by controlling the supersaturation and shear rate during nanoprecipitation. At flow rates where the shear rate was below the critical shear rate for silk, increasing the concentration of silk in both bulk and micro-mixing processes resulted in particle populations of increased sphericity, lower size, and lower polydispersity index. At high flow rates, where the critical shear rate was exceeded, the increased supersaturation with increasing concentration was counteracted by increased rates of shear-induced assembly. The morphology could be tuned from rod-like to spherical assemblies by increasing supersaturation of the high-shear micro-mixing process, thereby supporting a role for fast mixing in the production of narrow-polydispersity silk nanoparticles. This work provides new insight into the effects of shear during nanoprecipitation and provides a framework for scalable manufacture of spherical and rod-like silk nanoparticles

Analysis of surfactant-associated bacteria in the sea surface microlayer using deoxyribonucleic acid sequencing and synthetic aperture radar

The sea surface microlayer (SML) is the upper 1 mm of the ocean, where Earth’s biogeochemical processes occur between the ocean and atmosphere. It is physicochemically distinct from the water below and highly variable in space and time due to changing physical conditions. Some microorganisms influence the composition of the SML by producing surfactants for biological functions that accumulate on the surface, decrease surface tension, and create slicks. Slicks can be visible to the eye and in synthetic aperture radar (SAR) satellite imagery. This study focuses on surfactant-associated bacteria in the near-surface layer and their role in slick formation where oil is present

Stochastic optics: A local realistic analysis of optical tests of Bell inequalities

Stochastic optics may be considered as simply a local realistic interpretation of quantum optics and, in this sense, it is a first step in the reinterpretation of the whole of quantum theory. However, as it is not possible to interpret all the details of quantum theory in a local realistic manner, as shown by Bell’s theorem, minor changes are introduced in the formalism with the consequence that the new theory makes different predictions in some special cases. In stochastic optics, the quantum-operator formalism is simply considered a formal way of dealing with stochastic fields. In particular, the quantum zero point is taken as a real random electromagnetic radiation filling the whole of space. This radiation noise has the same nature as light signals, the only difference being the greater intensity of the latter. We assume that photon detectors have an intensity threshold just above the level of the noise, thus detecting only signals. Transmission of radiation through polarizers follows Malus’s law, but the interplay of signal and noise leads quite naturally to the prediction that the detection probability of some signals is enhanced, which is known to be a necessary condition for the violation of the empirically tested Bell inequalities. In our view, correlated photon pairs are pairs of light signals supercorrelated in polarization, in the sense that, as well as the signal, the accompanying noise is also correlated. Thus stochastic optics allows predictions for the empirical correlations very close, but not identical, to the quantum ones. The theory is applied to the analysis of all experiments designed to test the Bell inequalities by measuring polarization correlations of photon pairs. The predictions agree with quantum optics and experiments within statistical errors, except for the Holt-Pipkin experiment. In this case, the experimental results agree with stochastic optical predictions within two standard deviations while violating quantum optics by four