ABSTRACT
The ability of materials to withstand environmental influences is a frequent necessity in many industries. Special requirements are imposed by such industries where surfaces are affected by acidity during the processing or storage of products. In such cases, when the basic surface is exposed to chemical influences, it is possible to use enamel coatings, which, with their properties, guarantee the protection of the surface and achieve the required service life of the material. This article deals mainly with the interaction between the base material and the enamel and its resistance to wear between the original and the renovated surface caused by local heating. The article presents a methodical procedure for the preparation of test specimens with an enamel layer prepared by AWJ cutting, eliminating its damage. There are minimal differences in the microstructure between the original and the renovated surface due to the production technique. The renovated enamel surface had more bubbles of a larger size than the original surface. Good adhesion between the base metal material (substrate) and the ground coat was demonstrated. The tested surfaces demonstrated high resistance to intensive abrasion conditions with low linear wear increments.
ABSTRACT
OBJECTIVE/BACKGROUND: Obstructive sleep apnea (OSA) is highly prevalent and often undiagnosed in surgical patients. The aim of this study was to compare polygraphy (PG) performed on sedated patients during surgery to overnight polysomnography (PSG). It was hypothesized that perioperative PG may be used to diagnose OSA. PATIENTS/METHODS: Overnight PSG was performed three days prior to surgery. For surgery, spinal anesthesia and sedation with propofol infusion were used. Sedation depth was monitored by the Bispectral index and maintained for all patients (target level 75). Echocardiography studies were available in three patients, and all were diagnosed with diastolic dysfunction. Relatively high prevalence of CSA in patients with diastolic dysfunction has been previously reported. During surgery, PG recording (Embletta) was performed. Sleep apnea was defined by the type (central/obstructive apnea ≥50%) and by the apnea-hypopnea index (AHI) (events/hour: AHI < 5 no apnea; 5 ≤ AHI < 15 mild apnea; 15 ≤ AHI < 30 moderate apnea; AHI ≥30 severe apnea). Bland-Altman plots were used for analysis, and 2 × 2 decision statistics were calculated for several cut-off values of the AHI. Data were shown as bias with limits of agreement (bias±1.96 standard deviations). RESULTS: Nineteen subjects were studied: nine (47%) were diagnosed with obstructive, seven (37%) with central sleep apnea, and three (16%) with no sleep apnea by overnight PSG. Perioperative PG bias was 12 (-37; 61) for AHI; 6 (-25; 37) for obstructive apnea; 0 (-4; 4) for central apnea, and 6 (-31; 43) for hypopnea. For the detection of OSA, a PG cut-off value of AHI 5 yielded 89% sensitivity and 60% specificity, AHI 15 yielded 86% sensitivity and 67% specificity, and AHI 30 yielded 100% sensitivity and 71% specificity. CONCLUSION: Wide limits of agreement preclude perioperative PG to be used as a diagnostic method; however, it may be useful to screen sedated surgical patients for OSA.
