Air Leak Syndrome In Patients With Severe Covid Pneumonia.

Abstract: There are number of emerging studies that link the air leak syndrome (ALS) with COVID 19 disease but still data to explain the association, incidence and outcome in these patients is lacking. We aim to understand the risk factors and clinical outcome of these air leakage events in COVID 19 patients admitted to our institution. Methods: This is a single-centered case series conducted at the COVID unit of the SMBBIT in Karachi, Pakistan. Data collection was done from April 24, 2020 to June 10, 2021. Results: There were 19 patients with severe COVID pneumonia who developed air leaks. Most common finding was subcutaneous emphysema 94%. Four patients (21%) didn't receive positive pressure ventilation in any form. Median time of developing air leak from admission is 5 [2-9] and from PPV is 2 [1-3] days. There was high percentage of mortality 84.5 % in these patients.

Airway fires during surgery: Management and prevention.

Airway fires pose a serious risk to surgical patients. Fires during surgery have been reported for many years with flammable anesthetic agents being the main culprits in the past. Association of airway fires with laser surgery is well-recognized, but there are reports of endotracheal tube fires ignited by electrocautery during pharyngeal surgery or tracheostomy or both. This uncommon complication has potentially grave consequences. While airway fires are relatively uncommon occurrences, they are very serious and can often be fatal. Success in preventing such events requires a thorough understanding of the components leading to a fire (fuel, oxidizer, and ignition source), as well as good communication between all members present to appropriately manage the fire and ensure patient safety. We present a case of fire in the airway during routine adenotonsillectomy. We will review the causes, preventive measures, and brief management for airway fires.

Fracture toughness testing: A discriminatory mechanical testing performance indicator for glass-ionomer restoratives?

OBJECTIVES: To investigate the single-edge notched (SEN) bend fracture toughness (KIC) testing methodology as a reproducible and discriminatory mechanical testing protocol for encapsulated and hand-mixed glass-ionomers (GI). METHODS: SEN bend test-pieces (35.0±0.1mm length, 6.0±0.1mm width, 3.0±0.1mm thickness with a sharp notch formed at mid-length by embedding a scalpel blade) were prepared for KIC testing using three encapsulated GI products (Chemfil Rock, Fuji IXGP Fast Capsule and Ionofil Molar AC). In addition, test-pieces were prepared from a hand-mixed GI product (Ionofil Molar) which contained between 100% and 20% of the manufacturer's recommended powder content (in 10% decrements) for a constant weight of liquid. Groups of 20 test-pieces were prepared for each encapsulated GI product (n=3) and hand-mixed GI powder:liquid mixing ratio (n=9). Data were statistically analyzed and the coefficients of variation (CoV) determined for each encapsulated GI product and hand-mixed GI powder:liquid mixing ratio. RESULTS: The KIC testing methodology failed to discriminate between the encapsulated GI products that were investigated (p=0.225). For the hand-mixed GI, the KIC testing methodology also failed to discriminate between the powder:liquid mixing ratios investigated (R(2)=0.576). The pooled CoV (10%) for the encapsulated GI products and for the powder:liquid mixing ratio groups (12%) identified the reproducibility of the test for this experiment. For the hand-mixed GI mixing ratio groups with between 100% to 50% of the recommended powder content, no trend could be discerned. SIGNIFICANCE: The KIC testing methodology failed to discriminate between different encapsulated GI products and hand-mixed GI powder:liquid mixing ratio groups investigated, despite KIC being an intrinsic material property and the coefficient of variation being acceptable.

Conventional glass-ionomer materials: A review of the developments in glass powder, polyacid liquid and the strategies of reinforcement.

OBJECTIVES: The development of glass-ionomers (GIs) from the earliest experimental GI formulations to the modern day commercially available GIs was reviewed. The aim of the review was to identify the developments in the glass powder and polyacid liquid constituents of GIs since their inception in the late 1960s. DATA: The glass powder has undergone major changes from the earliest GI powder formulation (G200) in an effort to enhance the reactivity with the polyacid liquid. The GI liquids have also been optimised by the manufacturers in terms of polyacid composition, molecular weight and concentration to improve the handling characteristics. Despite these developments in the glass powder and polyacid liquid constituents, GIs cannot 'truly' be advocated for the restoration of posterior dentition due to the poor mechanical properties when compared with dental amalgam and resin-based composites (RBCs). SOURCES: Various attempts to improve the mechanical properties of GIs through substitution of reinforcing fillers to the GI powder or modification of the GI liquid were identified in the dental literature. Despite the claimed improvements in mechanical properties of the modified GIs, a wide variation in mixing and testing conditions was identified which prevented a valid assessment of the reported reinforcement strategies. When investigating a GI reinforcement strategy it is crucial that the mixing and testing conditions are standardised to allow a valid comparison between studies. STUDY SELECTION: The dental literature reporting the earliest experimental GIs to modern day commercially available GIs (1969-2015) was reviewed. In addition, full-text publications and abstracts published in English reporting various GI reinforcement strategies were included. CONCLUSION: Nevertheless, major improvements in GI formulations through a reinforcement strategy have yet to be made to enable clinical usage of GIs for the restoration of posterior dentition. CLINICAL SIGNIFICANCE: GIs chemically are inherently weak but bond to sound tooth structure without the need for preconditioning or removal of sound tooth structure such that improvements in the mechanical properties of GIs would be desirable. Although advances have been made through different GI glass powder and polyacid liquid formulations over the past 40 years, further improvements in the mechanical properties of the current GIs are required to be indicated for the restoration of posterior dentition. The literature is replete with reports on GI reinforcement, however, improved reporting and control of mixing and testing conditions are required for a valid assessment of the reinforcement strategies.

A discriminatory mechanical testing performance indicator protocol for hand-mixed glass-ionomer restoratives.

OBJECTIVES: To identify a reproducible and discriminatory mechanical testing methodology to act as a performance indicator for hand-mixed glass-ionomer (GI) restoratives. METHODS: Groups of 20 (five batches of four) cylinders (6.0±0.1 mm height, 4.0±0.1 mm diameter) for compressive fracture strength (CFS) and compressive modulus (CM) testing, bars (25.0±0.1 mm length, 2.0±0.1 mm width, 2.0±0.1 mm thickness) for three-point flexure strength (TFS) and tensile flexural modulus (TFM) testing, discs (13.0±0.1 mm diameter, 1.0±0.1 mm thickness and 10.0±0.1 mm diameter, 3.10±0.03 mm thickness) for biaxial flexure strength (BFS) and Hertzian indentation (HI) testing, respectively, were prepared using a hand-mixed GI restorative manipulated with 100-20% (in 10% increments) of the manufacturers recommended powder content for a constant weight of liquid. Data were statistically analyzed at p<0.05, the coefficient of variation (CoV) was assessed for the four tests at each powder:liquid mixing ratio investigated (n=9) and a Weibull analysis performed on the CFS, TFS and BFS data to assess the reliability of the data sets. The failure mode and fracture origin of the HI specimens was assessed by fractography. RESULTS: For the hand-mixed GI restorative, a progressive reduction in the powder content (by 10% for a constant weight of liquid) resulted in a progressive linear deterioration (p<0.001) in the CFS (R2=0.957), CM (R2=0.961) and TFM (R2=0.982) data. However, no linear deterioration (p>0.05) was identified for the TFS (R2=0.572), BFS (R2=0.81) and HI (R2=0.234). The CoV and Weibull data identified distinct regions--three for the CFS and TFS data and two for the BFS data sets, within the range of powder:liquid mixing ratios investigated. Fractographic analysis of HI specimens revealed a transition in failure mode from bottom-initiated radial cracking to top-initiated cone cracking on reducing the powder content for a constant weight of liquid. SIGNIFICANCE: The CFS test is the only discriminatory performance indicator for hand-mixed GIs from amongst the four mechanical testing approaches (CFS, TFS, BFS and HI) investigated. The CM and TFM represent an intrinsic material property independent of specimen dimensions and may be used as an adjunct to a mechanical testing approach when investigating hand-mixed GIs.

Hertzian indentation testing of glass-ionomer restoratives: A reliable and clinically relevant testing approach.

OBJECTIVES: To investigate the load to failure of encapsulated posterior glass-ionomer (GI) restoratives tested under Hertzian indentation and to explore the validity and reproducibility of the test results achieved for consideration of inclusion as an ISO testing protocol. METHODS: Groups of 20 disc-shaped specimens (10.0±0.1mm diameter, 3.10±0.03mm thickness) were prepared (in batches of four) from three encapsulated posterior GI restoratives. Discs were tested while resting freely on a dentine analogue material at 24h under Hertzian indentation at a rate of 1mm/min delivered through a 20mm diameter hard steel ball. The failure mode and fracture origin of the GI specimens was assessed by fractography. Statistical analyses of the load to failure data were conducted using SPSS software (p<0.05) with the normality and homogeneity of variance of the load to failure data assessed using the Shapiro-Wilk and Levene's test, respectively. Data was also analysed using regression analyses to identify trends within the load to failure data sets. RESULTS: The load to failure data for the GI restorative groups investigated were normally distributed (p>0.05), homogenous (p>0.05) and not significantly influenced by batch (p>0.780) or specimen number (p>0.447) although significant differences (p<0.05) between the GI restorative materials were evident. Fractographic analysis identified smooth fracture surfaces parallel to the loading axis where the failure mode was bottom initiated radial cracking. The mean coefficient of variation (CoV) for the GI restorative load to failure data sets achieved using Hertzian indentation testing was 7%. SIGNIFICANCE: The failure mode and fracture origin of the GI restoratives tested using Hertzian indentation is representative of the clinical situation in vivo. The reliability of the load to failure data sets produced were improved compared with routinely employed mechanical testing approaches suggesting the possibility of inclusion as an ISO testing protocol.