Facile preparation of biocompatible poly (lactic acid)-reinforced poly(ε-caprolactone) fibers via graphite nanoplatelets -aided melt spinning.

Addition of high-aspect-ratio (AR) nanofillers can markedly influence flow behavior of polymer systems. As a result, application of graphite nanoplatelets (GNP) allows preparation of microfibrillar composites (MFC) based on PCL matrix reinforced with in-situ generated PLA fibrils. This work deals, for the first time, with preparation of analogous melt-drawn fibers. Unlike other blend-based fibers, the spinning and melt drawing leads to structure of deformed inclusions due to unfavorable ratio of rheological parameters of components. Subsequent moderate cold drawing of the system with dissimilar deformability of components causes strengthening with PLA fibrils. Unexpectedly, high velocity and extent of cold drawing leads to structure with low-AR inclusions, similar to the original melt-drawn blend. Extensive fast deformation of the soft PCL matrix does not allow sufficient stress transfer to rigid PLA. In spite of peculiarities found, the GNP-aided melt spinning allows facile preparation of biodegradable biocompatible fibers with wide range of diameters (80-400 µm) and parameters (2.35-18 cN/tex).

Graphite nanoplatelets-modified PLA/PCL: Effect of blend ratio and nanofiller localization on structure and properties.

Structure and properties of poly(lactic acid) (PLA)/poly (ɛ-caprolactone) (PCL) influenced by graphite nanoplatelets (GNP) were studied in dependence on blend composition. Electron microscopy indicates predominant localization of GNP in PCL. GNP-induced changes in viscosity hinder refinement of PCL inclusions, support PCL continuity in the co-continuous system, and lead to reduction of PLA inclusions size without GNP being present at the interface in the PCL-matrix blend. Negligible differences in crystallinity of both phases indicate that mechanical behaviour is mainly influenced by reinforcement and GNP-induced changes in morphology. Addition of 5 parts of GNP leads to ~40% and ~25% increase of stiffness in the PCL- and PLA-matrix systems, respectively, whereas the reinforcing effect is practically eliminated in the co-continuous systems due to GNP-induced lower continuity of PLA which enhances toughness. Impact resistance of the 80/20 blend shows increase with 5 parts content due to synergistic effect of PCL/GNP stacks, whereas minor increase in the blend of the ductile PCL matrix with brittle PLA inclusions is caused by GNP-modification of the component parameters. Results indicate high potential of GNP in preparing biocompatible systems with wide range of structure and properties.

How accurately can the aetiology of cardiac arrest be established in an out-of-hospital setting? Analysis by "concordance in diagnosis crosscheck tables".

INTRODUCTION: Several previous studies have focused on establishing the cause of cardiac arrest (CA) during cardiopulmonary resuscitation (CPR) provided in an out-of-hospital setting. OBJECTIVES: To analyze the ability of professional advanced life support providers to correctly establish the aetiology of cardiac arrest during out-of-hospital CPR. STUDY DESIGN: A retrospective cohort study analysing 211 cases of out-of-hospital cardiac arrest. METHOD: The aetiology assumed by out-of-hospital physicians was compared with the diagnosis that was later established by clinicians or pathologists. RESULTS: Cases were sorted into five diagnostic groups and the overall diagnostic concordance was 74.4% (157 of 211 cases). The cardiac aetiology was presumed in 132 out of 211 patients and confirmed in 135 out of 211 patients. However, an analysis of individual cases of the cardiac causes of cardiac arrest revealed diagnostic matches in only 112 cases. Acute myocardial infarction (AMI) or pulmonary embolism (PE), both of which represent cases that can be potentially influenced by thrombolytic therapy, were presumed in 74 (53+21) and confirmed in 97 (77+20) cases, however with individual diagnostic matches in only 55 cases. CONCLUSION: This study demonstrates the importance of analysing concordance in presumed and definitive diagnosis of individual cases, since an overall comparison in a cohort of cases may be highly misleading. It introduces the method of the crosscheck table for visualization and comparison of presumed and final diagnoses. The two alternative approaches of inclusion rule for applying the thrombolytic therapy in out-of-hospital care were discussed with regard to the recent TROICA study.

A sudden increase in partial pressure end-tidal carbon dioxide (P(ET)CO(2)) at the moment of return of spontaneous circulation.

BACKGROUND: Previous studies established that a level of partial pressure end-tidal carbon dioxide (P(ET)CO(2)) of 10 mm Hg divided patients undergoing advanced life support (ALS) into those likely to be resuscitated (values > 10 mm Hg) and those likely to die during ALS (values < 10 mm Hg). OBJECTIVE: The study tested the significance of a sudden increase in the P(ET)CO(2) in signaling the return of spontaneous circulation (ROSC) during ALS. MATERIAL AND METHODS: P(ET)CO(2) values were continuously recorded during ALS in out-of-hospital patients with cardiac arrest. Constant ventilation was maintained by an automatic device. There were 108 patients, representing two extreme outcomes of ALS, who were subdivided into two groups. The first group included 59 patients with a single ROSC followed by a stable spontaneous circulation. The second group included 49 patients with no signs of ROSC. RESULTS: ROSC was associated with a sudden increase in P(ET)CO(2) that remained significantly higher than before ROSC. P(ET)CO(2) did not rise during the entire ALS in the second group of patients without ROSC and was lower than in the first group of patients. CONCLUSIONS: In constantly ventilated patients, P(ET)CO(2) is significantly higher (about 10 mm Hg) after ROSC than before ROSC. A sudden increase in P(ET)CO(2) exceeding 10 mm Hg may indicate ROSC. Consequently, the rule of 10 mm Hg may be extended to include a sudden increase in continuously recorded P(ET)CO(2) by more than 10 mm Hg as an indicator of the possibility of ROSC.