Gastropod Slime-Based Gel as an Adjustable Synthetic Model for Human Airway Mucus.

Airway mucus works as a protective barrier in the human body, as it entraps pathogens that will be later cleared from the airways by ciliary transport or by coughing, thus featuring the rheological properties of a highly stretchable gel. Nonetheless, the study of these physical barrier as well as transport properties remains limited due to the restricted and invasive access to lungs and bronchi to retrieve mucus and to the poor repeatability inherent to native mucus samples. To overcome these limits, we report on a biobased synthetic mucus prepared from snail slime and multibranched thiol cross-linker, which are able to establish disulfide bonds, in analogy with the disulfide bonding of mucins, and therefore build viscoelastoplastic hydrogels. The gel macroscopic properties are tuned by modifying the cross-linker and slime concentrations and can quantitatively match those of native sputum from donors with cystic fibrosis (CF) or non-cystic fibrosis bronchiectasis (NCFB) both in the small- and large-deformation regimes. Heterogeneous regimes were locally found in the mucus model by passive microrheology, in which both diffusive and non-diffusive motion are present, similar to what is observed in sputa. The biobased synthetic approach proposed in the present study thus allows to produce, with commercially available components, a promising model to native respiratory mucus regarding both mechanical and, to a lesser extent, physicochemical aspects.

Ex-vivo effects of intrapulmonary percussive ventilation on sputum rheological properties.

Intrapulmonary percussive ventilation (IPV) has been postulated to enhance mucociliary clearance by improving tracheobronchial sputum rheological properties. The IPV effects on linear (viscoelasticity) and non-linear (flowing) rheological properties of 40 sputum samples collected from 19 patients with muco-obstructive lung diseases were investigated ex-vivo. Each sputum sample was split into 4 aliquots. These aliquots were independently placed in a circuit connected on one side to an IPV device and on the other side to a lung model that simulated spontaneous adult breaths. IPV was superimposed on simulated breathing. Three aliquots were exposed to a different IPV setting, modifying either percussion frequency or amplitude (4 Hz-200 L/min, 10 Hz-200 L/min, 10 Hz-140 L/min). One aliquot was only exposed to breathing (IPV was switched off, control condition). Each aliquot underwent 5 min of the pre-fixed mechanical stimulation before being recollected to proceed to rheological analysis. Neither percussion frequencies nor amplitudes had a significant impact on any sputum rheological properties studied. These results need to be confirmed in vivo.

Sputum handling for rheology.

The rheology of sputum is viewed as a powerful emerging biophysical marker for monitoring muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and non-CF bronchiectasis (NCFB). However, there is no unified practice to process sputa from collection to analysis, which can lead to highly variable, and sometimes inconsistent results. The main objective of this study is to bring light into the handling of sputum samples to establish a standardised and robust protocol before rheological measurements. Sputum collected from 22 CF and 10 NCFB adults, was divided into control (vortexed and fresh: non-heated and non-frozen) and three treated conditions (either non-vortexed, heated or frozen). In addition, 6 CF expectorations were used to study the dynamics of ageing over 24 h. Sputum's mechanical properties were measured with a rotational rheometer to obtain their properties at rest, elastic ([Formula: see text]) and viscous moduli ([Formula: see text]), and at the onset of flow, critical deformation ([Formula: see text]) and critical stress ([Formula: see text]). We demonstrate that heating sputum is completely destructive while freezing sputa at [Formula: see text] has no discernible effect on their rheology. We also show that the variability of rheological measurements largely resulted from the sample's macroscopic heterogeneity, and can be greatly reduced by non-destructive vortex homogenisation. Finally, we observed contrasted ageing effects as a fonction of purulence: while the viscoelasticity of purulent samples reduced by half within 6 h after collection, semi-purulent samples did not evolve. These results guide towards a robust unified protocol for simple sputum handling in rheometry. We therefore suggest to vortex and snap freeze sputum samples immediately after collection when direct testing is not possible.

Simulation-based education to improve management of refractory anaphylaxis in an allergy clinic.

BACKGROUND: High-fidelity simulations based on real-life clinical scenarios have frequently been used to improve patient care, knowledge and teamwork in the acute care setting. Still, they are seldom included in the allergy-immunology curriculum or continuous medical education. Our main goal was to assess if critical care simulations in allergy improved performance in the clinical setting. METHODS: Advanced anaphylaxis scenarios were designed by a panel of emergency, intensive care unit, anesthesiology and allergy-immunology specialists and then adapted for the adult allergy clinic setting. This simulation activity included a first part in the high-fidelity simulation-training laboratory and a second at the adult allergy clinic involving actors and a high-fidelity mannequin. Participants filled out a questionnaire, and qualitative interviews were performed with staff after they had managed cases of refractory anaphylaxis. RESULTS: Four nurses, seven allergy-immunology fellows and six allergy/immunologists underwent the simulation. Questionnaires showed a perceived improvement in aspects of crisis and anaphylaxis management. The in-situ simulation revealed gaps in the process, which were subsequently resolved. Qualitative interviews with participants revealed a more rapid and orderly response and improved confidence in their abilities and that of their colleagues to manage anaphylaxis. CONCLUSION: High-fidelity simulations can improve the management of anaphylaxis in the allergy clinic and team confidence. This activity was instrumental in reducing staff reluctance to perform high-risk challenges in the ambulatory setting, thus lifting a critical barrier for implementing oral immunotherapy at our adult center.

Bridging Knowledge Gaps in Anaphylaxis Management Through a Video-Based Educational Tool.

Introduction: We aimed to develop and test the effectiveness of an education tool to help pediatric patients and their families better understand anaphylaxis and its management, and to improve current knowledge and treatment guidelines adherence. Methods: From June 2019 to May 2022, 128 pediatric patients with history of food-triggered anaphylaxis who presented to the allergy outpatient clinics at the study institution were recruited. Consenting families were asked to complete 6 questions related to the triggers, recognition, and management of anaphylaxis at the time of presentation to the clinic. Participants were shown a 5-min animated video on the causes, presentation, and management of anaphylaxis. At the end of the video, the participants were redirected to the same 6 questions to respond again. The scores were recorded in proportion of correct answers (minimum 0.0; maximum 1.0). Results: The mean age of the patients was 5.8 ± 4.5 years (range: 0.5-18.8 years). The majority were males (70 patients; 54.7%). The mean baseline prevideo education questionnaire score was 0.76 ± 0.2 (range: 0.3-1.0), whereas the mean follow-up score was 0.82 ± 0.2 (range: 0.3-1.0). This score difference of 0.06 was statistically significant (P < 0.001). There were no significant associations between change in scores and age or gender of the participants. Conclusion: Our video teaching method was successful in educating patients and their families to better understand anaphylaxis and its management at the moment of the clinical encounter. Retention of knowledge at long-term follow-up should be assessed.

Rapid Viscoelastic Characterization of Airway Mucus Using a Benchtop Rheometer.

In muco-obstructive lung diseases (e.g., asthma, chronic obstructive pulmonary disease, cystic fibrosis) and other respiratory conditions (e.g., viral/bacterial infections), mucus biophysical properties are altered by goblet cell hypersecretion, airway dehydration, oxidative stress, and the presence of extracellular DNA. Previous studies showed that sputum viscoelasticity correlated with pulmonary function and that treatments affecting sputum rheology (e.g., mucolytics) can result in remarkable clinical benefits. In general, rheological measurements of non-Newtonian fluids employ elaborate, time-consuming approaches (e.g., parallel/cone-plate rheometers and/or microbead particle tracking) that require extensive training to perform the assay and interpret the data. This study tested the reliability, reproducibility, and sensitivity of Rheomuco, a user-friendly benchtop device that is designed to perform rapid measurements using dynamic oscillation with a shear-strain sweep to provide linear viscoelastic moduli (G', G", G*, and tan δ) and gel point characteristics (γc and σc) for clinical samples within 5 min. Device performance was validated using different concentrations of a mucus simulant, 8 MDa polyethylene oxide (PEO), and against traditional bulk rheology measurements. A clinical isolate harvested from an intubated patient with status asthmaticus (SA) was then assessed in triplicate measurements and the coefficient of variation between measurements is <10%. Ex vivo use of a potent mucus reducing agent, TCEP, on SA mucus resulted in a five-fold decrease in elastic modulus and a change toward a more "liquid-like" behavior overall (e.g., higher tan δ). Together, these results demonstrate that the tested benchtop rheometer can make reliable measures of mucus viscoelasticity in clinical and research settings. In summary, the described protocol could be used to explore the effects of mucoactive drugs (e.g., rhDNase, N-acetyl cysteine) onsite to adapt treatment on a case-by-case basis, or in preclinical studies of novel compounds.

Bradykinin-induced angioedema in the emergency department.

BACKGROUND: Acute airway angioedema commonly occurs through two distinct mechanisms: histamine- and bradykinin-dependent. Although they respond to distinct treatments, these two potentially life-threatening states present similarly. Poor recognition of the bradykinin-dependent pathway leads to treatment errors in the emergency department (ED), despite the availability of multiple pharmacologic options for hereditary angioedema (HAE) and other forms of bradykinin-induced angioedema. Here, we consider the pathophysiology and clinical features of bradykinin-induced angioedema, and we present a systematic literature review exploring the effectiveness of the available therapies for managing such cases. METHODS: PubMed searches using 'emergency', 'bradykinin' and various therapeutic product names identified studies reporting the efficacy of treatments for bradykinin-induced angioedema in the ED setting. In all, 22 studies met prespecified criteria and are analysed here. FINDINGS: Whereas histamine-induced angioedema has a faster onset and often presents with urticaria, bradykinin-induced angioedema is slower in onset, with greater incidence of abdominal symptoms. Acute airway angioedema in the ED should initially be treated with anaphylactic protocols, focusing on airway management and treatment with epinephrine, antihistamine and systemic steroids. Bradykinin-induced angioedema should be considered if this standard treatment is not effective, despite proper dosing and regard of beta-adrenergic blockade. Therapeutics currently approved for HAE appear as promising options for this and other forms of bradykinin-induced angioedema encountered in the ED. CONCLUSION: Diagnostic algorithms of bradykinin-induced angioedema should be followed in the ED, with early use of approved therapies to improve patient outcomes.

Rheological analysis of sputum from patients with chronic bronchial diseases.

Bronchial diseases are characterised by the weak efficiency of mucus transport through the lower airways, leading in some cases to the muco-obstruction of bronchi. It has been hypothesised that this loss of clearance results from alterations in the mucus rheology, which are reflected in sputum samples collected from patients, making sputum rheology a possible biophysical marker of these diseases and their evolution. However, previous rheological studies have focused on quasi-static viscoelastic (linear storage and loss moduli) properties only, which are not representative of the mucus mobilisation within the respiratory tract. In this paper, we extend this approach further, by analysing both quasi-static and some dynamic (flow point) properties, to assess their usability and relative performance in characterising several chronic bronchial diseases (asthma, chronic obstructive pulmonary disease, and cystic fibrosis) and distinguishing them from healthy subjects. We demonstrate that pathologies influence substantially the linear and flow properties. Linear moduli are weakly condition-specific and even though the corresponding ranges overlap, distinct levels can be identified. This directly relates to the specific mucus structure in each case. In contrast, the flow point is found to strongly increase in muco-obstructive diseases, which may reflect the complete failure of mucociliary clearance causing episodic obstructions. These results suggest that the analysis of quasi-static and dynamic regimes in sputum rheology is in fact useful as these regimes provide complementary markers of chronic bronchial diseases.

Complications following chin laceration reparation using tissue adhesive compared to suture in children.

BACKGROUND: Tissue adhesive is widely used in the emergency department to repair minor lacerations but there exists a debate as to whether it should be used for chin lacerations. The main objective of this study was to evaluate the rate of wound dehiscence of chin lacerations repaired with tissue adhesive in comparison to sutures. METHODS: This was a retrospective chart review including all children requiring a facial laceration reparation in a single tertiary care paediatric hospital. The primary outcome was wound dehiscence in the 30 days following reparation, comparing the use of tissue adhesive and sutures. The independent variable of interest was the use of tissue adhesive vs suture. A random sample of charts was reviewed in duplicate to insure reliability of the chart review. RESULTS: Among the 2044 children presenting with a facial laceration requiring an intervention, 1804 (88%) were repaired using tissue adhesive. The laceration was located on the chin in 360 (18%) of patients. The use of tissue adhesive was not statistically associated with a higher risk of dehiscence for all facial lacerations (difference: 0.2; 95%CI: -1.9 to 0.8%), nor for chin lacerations (difference 2.2%; 95%CI: -7.5 to 4.4%). However, the probability of dehiscence was higher for chin laceration in comparison to other localizations (difference of 1.6%; 95%CI: 0.5-3.6%). CONCLUSION: While the rate of dehiscence was higher for chin lacerations compared to other facial localizations, the risk of dehiscence was not statistically different for chin laceration repaired with tissue adhesive or sutures.

Optical twisting to monitor the rheology of single cells.

BACKGROUND: Biological cells exhibit complex mechanical properties which determine their responses to applied force. OBJECTIVE: We developed an optical method to probe the temporal evolution of power-law rheology of single cells. METHODS: The method consisted in applying optically a constant mechanical torque to a birefringent microparticle bound to the cell membrane, and observing dynamics of the particle's in-plane rotation. RESULTS: The deformation dynamics of the membrane followed a power law of time, which directly relates to cytoskeletal prestress as reported in the literature. The temporal evolution of this rheological behaviour, over time scales of several minutes, showed strong variations of the exponent on single adherent cells not subject to any specific treatment. CONCLUSIONS: The consistent observation of variations in the exponent suggests that, in their normal activity, living cells modulate their prestress by up to three orders of magnitude within minutes.

Dynamics of colloid accumulation under flow over porous obstacles.

The accumulation of colloidal particles to build dense structures from dilute suspensions may follow distinct routes. The mechanical, structural and geometrical properties of these structures depend on local hydrodynamics and colloidal interactions. Using model suspensions flowing into microfabricated porous obstacles, we investigate this interplay by tuning both the flow pattern and the ionic strength. We observe the formation of a large diversity of shapes, and demonstrate that growing structures in turn influence the local velocity pattern, favouring particle deposition either locally or over a wide front. We also show that these structures are labile, stabilised by the flow pushing on them, in low ionic strength conditions, or cohesive, in a gel-like state, at higher ionic strength. The interplay between aggregate cohesion and erosion thus selects preferential growth modes and therefore dictates the final shape of the structure.

Thermocapillary migration in small-scale temperature gradients: application to optofluidic drop dispensing.

We experimentally investigate the thermocapillary migration induced by local laser heating of the advancing front of a growing droplet confined in a microfluidic channel. When heating implies an effective increase in interfacial tension, the laser behaves as a "soft door" whose stiffness can be tuned via the optical parameters (beam power and waist). The light-driven thermocapillary velocity of a growing droplet, which opposes the basic flow, is characterized for different types of fluid injection, either pressure or flow rate driven, and various channel aspect ratios. Measurements are interpreted using a simplified model for the temperature gradient at the interface, based on a purely diffusive, three-layer system. Considering the mean temperature gradient, we demonstrate that the classical large-scale temperature gradient behavior is retrieved in the opposite case when the thermal gradient length scale is smaller than the droplet size. We also demonstrate that the thermocapillary velocity is proportional to the smallest droplet curvature imposed by the channel confinement. This suggests that the thermocapillary velocity is in fact proportional to the mean temperature gradient and to the largest interface curvature radius, which both coincide with the imposed one and the spherical droplet radius in large-scale and unconfined situations. Furthermore, as used surfactant concentrations are largely above the critical micelle concentration, we propose a possible explanation, relying on state-of-the-art considerations on high-concentration surfactant-covered interfaces for the observed effective increase in interfacial tension with temperature. We also propose a mechanism for explaining the blocking effect at the scaling-law level. This mechanism involves the temporal evolution of hydrodynamic and thermocapillary forces, based on experimental observations. We finally show that this optocapillary interaction with a microfluidic droplet generator allows for controlling either the flow rate (valve) or the droplet size (sampler), depending on the imposed fluid injection conditions.

An optical toolbox for total control of droplet microfluidics.

The use of microfluidic drops as microreactors hinges on the active control of certain fundamental operations such as droplet formation, transport, division and fusion. Recent work has demonstrated that local heating from a focused laser can apply a thermocapillary force on a liquid interface sufficient to block the advance of a droplet in a microchannel (C. N. Baroud, J.-P. Delville, F. Gallaire and R. Wunenburger, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2007, 75(4), 046302). Here, we demonstrate the generality of this optical approach by implementing the operations mentioned above, without the need for any special microfabrication or moving parts. We concentrate on the applications to droplet manipulation by implementing a wide range of building blocks, such as a droplet valve, sorter, fuser, or divider. We also show how the building blocks may be combined by implementing a valve and fuser using a single laser spot. The underlying fundamentals, namely regarding the fluid mechanical, physico-chemical and thermal aspects, will be discussed in future publications.