Measurement of PEEP-induced alveolar recruitment: just a research tool?

For positive end-expiratory pressure (PEEP) to have lung protective efficacy in patients with acute respiratory distress syndrome, it must increase the end-expiratory lung volume through alveolar recruitment while avoiding lung over-inflation. PEEP may increase the end-expiratory lung volume either by increasing the proportion of aerated alveoli at end-expiration or by further inflating already ventilated lung regions. The optimal PEEP regimen is still a matter of debate. In theory, the ability to measure of PEEP-induced alveolar recruitment would be extremely useful in titrating PEEP at the bedside. However, until now this measurement has been confined to clinical research settings. Interesting work by Lu and coworkers, published in the previous issue of this journal, deals with the problem of measuring PEEP-induced alveolar recruitment. The 'gold standard' technique (i.e. the computed tomography method) is compared with the pressure-volume curve method. Because implementation of the latter method at the bedside would be relatively simple, that report, in addition to its intrinsic scientific value, may have important clinical implications

Day-case management of chronic suppurative otitis media with cholesteatoma with canal wall down technique surgery: long-term follow-up

The overall number of day-case otologic surgery cases is increasing; however, there is limited experience about performing canal wall down tympanoplasty in patients with chronic suppurative otitis media with cholesteatoma in this setting. The objective of this study was to assess the success of this technique as day-case surgery in terms of results and complications over an 8-year follow up period. We included in this study 42 patients undergoing canal wall down technique tympanoplasty surgery for chronic suppurative otitis media with cholesteatoma performed as day cases during a 2-year period. 30 cases (71.4%) were discharged on the day of surgery, whereas 12 cases (28.6%) were hospitalized and discharged the day after. The principal reasons for failure of discharge on the day of surgery were asthenia (6 cases), vertigo and asthenia (4 cases), undetermined (2 cases). Based on our experience, with a proper preoperative selection, assessment and screening of the patients, mastoidectomy with timpanoplasty for chronic suppurative otitis media with cholesteatoma can be carried out in a day surgery setting with no significant effects on effectiveness of surgery, post-operative symptoms and relapse of disease even in the long term

Seismic Microzonation Studies in the City of Ragusa (Italy)

The geotechnical zonation of the subsoil of the city of Ragusa suggests a high vulnerability of the physical environment added to site amplification of the ground motion phenomena. These elements concur on the definition of the Seismic Geotechnical Hazard of the city of Ragusa that should be correctly evaluated, through geo-settled seismic microzoning maps. Based on the seismic history of Ragusa, the following scenario events have been considered: the “Val di Noto” earthquake of January 11, 1693 (M=7.3), the “Etna” earthquake of March 1, 1818 (M=5.9), the 1895 earthquake (IMAX= 7 EMS), the Modica earthquake of January 23, 1980 (MW = 4.63) and the “Sicilian Earthquake” of December 13, 1990 (ML=5.6). Despite of its lower magnitude, a medium size, local earthquake, such as the 1990 “Sicilian” event, has to be accounted for the seismic hazard assessment of Ragusa, since it may cause heavy damage to the most urbanized area. According to historical data, the epicentre of this earthquake was located in the sea. This earthquake is considered a tectonic earthquake and is associated to the strike-slip segment of the Ibleo-Maltese fault system. This fault system is the major seismogenic structure of Eastern Sicily, and it is considered the responsible of the major historical earthquakes which struck this area in the past. According to the response spectra obtained through the application of the 1-D non-linear models, the city of Ragusa has been divided into some zones with different peak ground acceleration at the surface. Shaking maps for the central area of the city of Ragusa were generated via GIS for the scenario earthquakes. The maps represent an important tool for the seismic improvement of the buildings, indispensable for the mitigation of the seismic risk

Topographic Site Effects Evaluation for the Monte Po Hill in the City of Catania (Italy)

The Monte Po Hill is located in the North-eastern part of the city of Catania; this area is prone to high seismic risk due to the presence of several constructions, including a school, in the vicinity of a toe of a slope, characterized by precarious stability conditions. The study has regarded the evaluation of site effects in correspondence of the site, to which corresponds a different value of the Seismic Geotechnical Hazard. In the beginning of 2007 a seismic station has been also located into the school building, with the aim of recording seismic events. Seismograms obtained by the seismic station have been also used to evaluate the ground response analysis at the surface. Finally the 1-D computer code EERA was also used to model the equivalent-linear earthquake site response analyses of layered soil deposits of the hill. The detail with which the hill has been studied has allowed the construction of a detailed 2-D model of its structure. It has been explored the differences between the computed ground motion for different Vs profiles using QUAD4M and QUAKE/W 2-D codes. It has been also possible to compare the results from different 1-D models reflecting current approaches to the determination of site response

Dynamic Geotechnical Characterization of San Giuliano Di Puglia Seismic Area

The city of San Giuliano di Puglia (CB), located in the Molise region in Southern Italy, is prone to high seismic risk. For site characterisation of soil deep site investigations have been undertaken. Borings, static and dynamic in situ tests have been performed. Among them Cone Penetration Tests (CPT), Cross-Hole (C-H) Down-Hole (D-H) and Seismic Dilatometer Marchetti Tests (SDMT) have been carried out, with the aim to evaluate the soil profile of shear waves velocity (Vs). Moreover the following laboratory tests were carried out on undisturbed samples: Oedometer tests, undrained Triaxial tests and Resonant Column tests. The available data enabled one to compare the shear waves velocity profile obtained by empirical correlations, Down Hole tests and Seismic Dilatometer Marchetti Tests. The influence of strain level on G-γ and D-γ curves was evaluated by means of laboratory tests. Two expression to allows the complete shear modulus degradation with strain level and the inverse variation of damping ratio with normalized shear modulus respectively were proposed. Finally after evaluating the synthetic accelerograms at the bedrock, the ground response analysis at the surface, in terms of time history and response spectra, has been obtained by two non-linear models GEODIN and EERA

Dynamic Site Characterization by the Seismic Dilatometer Marchetti Test in Central Italy

This paper describes and compares the results of in situ and laboratory investigations performed on two Italian sites: St. Giuliano di Puglia (CB) located in the Molise region and Tito Scalo (PZ) located in the Basilicata Region. The tests were carried out to determine the variation of shear wave velocity with depth and strain level by Seismic Dilatometer Marchetti Test (SDMT), Cone Penetration Test (CPT), Noise Analysis Surface Waves (NASW), Down-Hole (DH) Test and Resonant Column Tests (RCT). Some considerations on shear modulus degradation evaluation by SDMT are proposed. The available data also enabled one to compare the shear modulus profile obtained by empirical correlations based on CPT and NASW or laboratory results with Down Hole Test and Seismic Dilatometer Marchetti Test

Soil Liquefaction and Risk Analysis From in Situ Tests for the City of Trapani (Italy)

The paper deals with a microzoning criterion based on CPT data to define liquefaction risk of the city of Trapani, Sicily (Italy). Zonation for liquefaction is a fundamental issue to prevent from seismic disasters since, as lessons of past earthquakes teach, liquefaction of sandy soils has been a major cause of damage to buildings. For the evaluation of the seismic risk of the municipal area of Trapani it has been chosen a scenario earthquake which may represent a possible repetition of the 1968 event. For this earthquake a Richter magnitude M= 6.0 and a maximum ground acceleration amax-= 0.30g have been estimated. While new tools and refinements continue to be developed on the subjects of pore pressure build-up due to earthquake shaking and of liquefaction triggering, reliable evaluation methods already exist for liquefaction microzonation purposes. This study focuses on the application of a method for the evaluation of the liquefaction potential to several sites of the city of Trapani, by means of relationships between liquefaction resistance and corrected cone penetration tests (CPT) resistance

Dynamic Model Tests on Gravity Retaining Walls with Various Surcharge Conditions

Seismic design of retaining walls is traditionally based on the Mononobe-Okabe method of analysis. In recent years a number of theoretical analyses have been presented to predict the seismic behaviour of gravity retaining walls. In this paper some shaking table tests performed on a small prototype of gravity wall retaining dry sand are described and the experimental results are presented with the aim to provide, though qualitatively, an insight into some important aspects of the dynamic behaviour of retaining structures resting on rigid foundation soil. The M-O theory do not consider the particular boundary condition that in the practical design of retaining structures are often in use like backfill geometries or loading condition. Shaking table studies were carried out in order to study the dynamic behaviour of gravity retaining walls resting on rigid foundation soil. Two different system have been taken into consideration namely, a wall retaining a horizontal backfill on which uniform surcharge was placed and a wall on which the uniform surcharge was placed to a distance «d» to the head of the wall

Geotechnical Characterization of a Soft Clay Soil Subjected to a Preloading Embankment

The paper presents the geotechnical characterization of a clay soil subjected to a preloading embankment for the construction of an industrial electronics building in the industrial area (STM M6) of Catania (Sicily, Italy). To determine the geological profile and the geotechnical characteristics of the soil, the site was well investigated by means of in situ and laboratory tests. The following in situ geotechnical tests were carried out: Borings, SPT, CPT, PLT and dynamic in situ tests have been performed. Among them Down-Hole (D-H), Cross-Hole (C-H), SASW and recently Seismic Dilatometer Marchetti Tests (SDMT) have been carried out, with the aim to evaluate the soil profile of shear waves velocity (Vs). Moreover the following laboratory tests were carried out on undisturbed samples retrieved with a 86 mm diameter Shelby sampler: Oedometer tests, Direct shear tests, Triaxial Tests, Resonant Column and Torsional shear tests. Static and dynamic parameters were compared by in situ and laboratory tests. A significantly correspondence between the values of the geotechnical parameters derived from laboratory and in situ tests was observed. The in situ and laboratory geotechnical analysis gives the parameters to evaluate the performance of soil subjected to soil embankment by mathematical modeling

Site Response Analysis in the STM-M6 Industrial Area of the City of Catania (Italy)

The paper presents the case history of the geotechnical characterization of a seismic site for the re-use of an industrial building for producing solar panels in the industrial area of Catania (Sicily, Italy). To determine the geological profile and the geotechnical characteristics of the soil, the site was well investigated by means of in situ and laboratory tests. The following in situ geotechnical tests were carried out: Borings, SPT, CPT, PLT and dynamic in situ tests. Among them Down-Hole (D-H), Cross-Hole (C-H), SASW and recently Seismic Dilatometer Marchetti Tests (SDMT) have been carried out, with the aim to evaluate the soil profile of shear waves velocity (Vs). Moreover the following laboratory tests were carried out on undisturbed samples retrieved with a 86 mm diameter Shelby sampler: Oedometer tests, Direct shear tests, Resonant Column and Torsional shear tests. Static and dynamic parameters obtained by in situ and laboratory tests were reported and analyzed. Moreover the Sicilian earthquake of December 13, 1990 (ML= 5.4) heavy damaged the site, also due to soil amplification. Using the recordings of this earthquake, to evaluate the input motion at the conventional bedrock, the ground response analysis has been obtained by the 1-D non-linear code EERA at the industrial building site. In particular the study has regarded the evaluation of site effects in terms of acceleration time history at the surface, soil amplification factors, as well as in terms of time history and response spectra