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Call number: LD2668 .T4 1956 H37 / Master of Science

Résumé : Introduction : La ventilation nasale, de plus en plus utilisée chez le nourrisson, peut insuffler de l’air dans l’estomac et causer des reflux gastro-œsophagiens (RGO). Parmi les modes de ventilation nasale, l’aide inspiratoire (AIn) devrait entrainer un plus grand nombre de RGO que le neuro-asservissement de la ventilation assistée (NAVAn), où l’insufflation d’air est plus «physiologique». L’objectif principal de l’étude est de comparer le nombre de RGO en NAVAn et en AIn dans notre modèle ovin d’étude du RGO néonatal et de ventilation nasale. Méthodes : Une polysomnographie avec pH-impédancemétrie œsophagienne de 6 h a été effectuée chez 10 agneaux nouveau-nés. L’enregistrement a été répété trois jours consécutifs (une condition par jour) en respiration spontanée, AIn (15/4 cmH[indice inférieur 2]O) et NAVAn (15/4 cmH[indice inférieur 2]O) dans un ordre randomisé. Résultats : Comparé à la respiration spontanée [13 (23)], le nombre de RGO en 6 h a diminué fortement et de façon similaire en AIn [1 (3)] et en NAVAn [2 (2)] (p < 0,05), même pour des RGO faiblement acides et proximaux. De plus, le nombre d’insufflations d’air n’était pas différent entre l’AIn et la NAVAn. Conclusion : L’AIn et la NAVAn inhibent de façon équivalente les RGO chez l’agneau, incluant les RGO faiblement acides et proximaux, si la pression inspiratoire n’est pas trop élevée et malgré le fait que de l’air soit insufflé dans l’œsophage. Ce résultat est identique à celui obtenu avec l’application d’une pression positive continue nasale (6 cmH[indice inférieur 2]O). Il est possible que la pression positive appliquée lors de la ventilation diminue les relaxations transitoires du sphincter inférieur de l’œsophage, mais des études en manométrie œsophagienne sont nécessaires pour comprendre les mécanismes en jeu. // Abstract : Introduction: Nasal ventilation, increasingly used in infants, can blow air in the stomach and cause gastroesophageal reflux (GER). Among the nasal ventilation modes, pressure support ventilation (nPSV) should lead to a greater number of GER than neurally-adjusted ventilatory assist (nNAVA), where the air delivery is more "physiological". The main objective of the study is to compare the number of GER in nNAVA and nPSV in our unique sheep model of neonatal GER and nasal ventilation. Methods: A 6h polysomnographic recording with esophageal pH-impedance was performed in 10 newborn lambs. The recording was repeated for three consecutive days (one condition per day) for spontaneous breathing, nPSV (15/4 cmH[subscript 2]O) and nNAVA (15/4 cm H[subscript 2]O) in a randomized order. Results: Compared with spontaneous breathing [13 (23)], the number of GER in 6h strongly and similarly decreased in nPSV [1 (3)] and nNAVA [2 (2)] (p < 0.05), even proximal and weakly acidic GER. In addition, the number of air insufflations was not different between nPSV and nNAVA. Conclusion: nPSV and nNAVA both inhibit GER in lambs, including weakly acidic and proximal GER, if the inspiratory pressure is not too high and despite the fact that air is blown into the esophagus. This result is identical to the one obtained with the application of a nasal continuous positive airway pressure (6 cmH[subscript 2]O). It is posssible that the applied positive pressure decreases transient relaxations of the lower esophageal sphincter, but esophageal manometry studies are needed to understand the mechanisms involved.

The work presented in this thesis investigates design, computer modelling and testing a sub-wet bulb temperature evaporative cooling system for space air conditioning in buildings. The context of this evaporative cooling technology design is specifically targeted at locations with a hot and dry climate such as that prevailing in most regions of Middle East countries. The focus of this technology is to address the ever-escalating energy consumption in buildings for space cooling using mechanical vapour compression air conditioning systems. In this work, two evaporative cooling configurations both based on sub-wet bulb temperature principle have been studied. Furthermore, in these designs, it was sought to adopt porous ceramic materials as wet media for the evaporative cooler and as building element and use of heat pipes as heat transfer devices. In the first test rig, the prototype system uses porous ceramic materials as part of a functioning building wall element. Experimental and modelling results were obtained for ambient inlet air dry bulb temperature of 30 and 35oC, relative humidity ranging from 35% to 55% and intake air velocity less than 2 (m/s). It was found that the design achieved sub-wet bulb air temperature conditions and a maximum cooling capacity approaching 242 W/m2 of exposed ceramic material wet surface area. The wet bulb effectiveness of the system was higher than unity. The second design exploits the high thermal conductivity of heat pipes to be integrated as an effective heat transfer device with wet porous ceramic flat panels for evaporative cooling. The thermal performance of the prototype was presented and the computer model was validated using laboratory tests at temperatures of 30 and 35oC and relative humidity ranging from 35% to 55%. It was found that at airflow rates of 0.0031kg/s, inlet dry-bulb temperature of 35oC and relative humidity of 35%, the supply air could be cooled to below the inlet air wet bulb temperature and achieve a maximum cooling capacity of about 206 W/m2 of wet ceramic surface area. It was shown that the computer model and experimental tests are largely in good agreement. Finally, a brief case study on direct evaporative cooling thermal performance and environmental impact was conducted as part of a field trip study conducted on an existing large scale installation in Mina Valley, Saudi Arabia. It was found that the evaporative cooling systems used for space cooling in pilgrims’ accommodations and in train stations could reduce energy consumption by as much as 75% and cut carbon dioxide emission by 78% compared to traditional vapour compression systems. This demonstrates strongly that in a region with a hot and dry climate such as Mina Valley, evaporative cooling systems can be an environmentally friendly and energy-efficient cooling system compared to conventional vapour compression systems.

Intrahospitala transporter är riskfyllda, det är rådande konsensus, och desto sjukare patienten är desto större är risken att drabbas för negativa händelser. Majoriteten av patienterna som vårdas på en intensivvårdsavdelning kommer någon gång att behöva genomgå just detta riskmoment. Det är dock inte bara patienterna som riskerar att fara illa. Även sjuksköterskan hamnar i en utsatt situation då risken för avvikande händelser eller vårdskador ökar. Detta examensarbete med en kvalitativ induktiv ansats syftar till att belysa intensivvårdssjuksköterskors erfarenheter och upplevelser kring att genomföra en intrahospital transport av ventilatorbehandlade patienter. Datainsamling har skett med semistrukturerade intervjuer på tre olika intensivvårdsavdelningar i Västra Götalandsregionen under våren 2016. Totalt har åtta intervjuer genomförts. Den insamlade datan har sedan analyserats med hjälp av kvalitativ innehållsanalys och presenteras i 10 subkategorier indelade i tre huvudkategorier. Det tre huvudkategorierna är följande: Personalrelaterade, patientrelaterade och miljörelaterade faktorer. Det framkom i resultatet att intensivvårdssjuksköterskor tänker mycket på de risker som kan uppstå under en intrahospital transport men också att det för sjuksköterskorna kan associeras med en känsla av att vara ensam eller utsatt. Faktorer som framkom som viktiga för att sjuksköterskorna skulle känna sig trygga i sitt arbete var att de hade stöd från sina mer erfarna kollegor för att skapa ett så optimalt temarbete som möjligt.

In this thesis project, a building in Vegagatan 12, Gävle has been analysed. The main objective has been to find why it consumes more energy than it was expected and to solve theoretically the problems.This building is a low energy building certified by Miljöbyggnad which should use less than 55kWh/m2 year and nowadays it is using 62.23 kWh/m2. In order to find why the building is using more energy than the expected several different things has been measured and analyzed.First of all, the heat exchanger of the ventilation unit has been theoretically examined to see if it works as it should and it does. This has been done using the definition of the heat exchangers.Secondly, the heating system has been analysed by measuring the internal temperature of the building and high temperatures have been found (around 22°C) in the apartments and in the corridors. This leads to 5-10% more use of energy per degree.Thirdly, the position and the necessity of all the heaters have been checked. One of the heaters may not make sense, at least in the way the building has been constructed. This leads to bigger heating needs than the expected.Fourthly, the taps and shower heads have been checked to see if they were efficient. Efficient taps and shower heads, reduce the hot water use up to 40%. The result of this analysis has been that all taps and shower heads are efficient.Fifthly, the hot water system has been studied and some heat losses have been found because the lack of insulation of several pipes. Because of this fact 8.37kWh/m2 are lost per year. This analysis has been carried out with the help of an infra red camera and a TA SCOPE.Sixthly, the theoretical and real U values of the different walls have been obtained and compared (concrete and brick walls). As a conclusion, the concrete wall has been well constructed but, the brick wall has not been well constructed. Because of this fact 1 kWh/m2 of heat are lost every year. Apart from that, windows and thermal bridges have also been checked.

Increased consciousness of the environmental problems has aroused people’s interest of renewable energy systems, especially the application of green features in buildings. The demand for air conditioning / cooling in domestic and non-domestic buildings is rising throughout the world; this increases the reliance on conventional fuels and the global warming effect from greenhouse gas emissions. Passive cooling and energy efficient design can substantially reduce reliance on fuel based heating and cooling. Passive and Hybrid Downdraught Cooling, in different forms, is now technically viable in many parts of the world. This has been established through a combination of research projects. In some hot arid regions, a major part of the energy consumed consists of air-conditioning requirements. Alternative methods, using passive cooling techniques, can assist in reducing the conventional energy consumption in buildings. Evaporative cooling, which can be tracked back several hundreds of years in ancient Egypt and Persia [1–3], is one of the most effective strategies, because of the enormous latent heat needed for evaporation of water. Green features are architectural features used to mitigate migration of various air-borne pollutants and transmission of air from outside to indoor environment in an advantageous way [9]. The reduction of fossil fuel consumption and the associated decrease in greenhouse gas emissions are vital to combat global warming and this can be accomplished, in part, by the use of natural ventilation. To assess the performance of several innovative cooling systems devices and to develop improved models for more established technology, quantitative measurement of output was necessary. This was achieved in this study by the development of simply constructed low energy cooling systems which were calibrated by the innovative use of wind and water as a source. These devices were found to be consistent and accurate in measuring the temperature and cooling load from a number of devices. There were some problems in the original evaporative units. Therefore, a number of modifications have to be made to enhance the systems performance. The novel Windcatcher – PEC cooling system was assessed and different cooling loads were achieved.

A smoke explosion is generally considered as a deflagration of the accumulated unburned fuel inside a closed compartment. However, the term smoke explosion has been widely misused for decades with a great deal of confusion, and very little research has been done towards this topic. The purpose of this research is to study the smoke explosion phenomenon in much more detail through the development of a fire scenario under various experimental conditions including ventilation size, fuel elevation and fuel mass, so that a more comprehensive understanding of this phenomenon can be achieved. A total of twenty experiments are carried out including both exploratory and final experiments. Thirteen experiments result in smoke explosions, among which there are five experiments result in more than one smoke explosion. A phenomenon referred as smoldering decay is observed in all experiments with smoke explosions, making it one of the precursors of the smoke explosion phenomenon. The smoldering decay is often indicated by an exponential decay of the temperature and is caused by the low oxygen concentration within the compartment. Based on the analysis, it is found that the vent size must be at least 50 mm in diameter in order for smoke explosions to occur. The fuel elevation has no influence on the occurrence of the smoke explosion. However when the fuel is placed near the ceiling, the temperature, the mass flow rate and the heat release rate are all lowered significantly. The size of the fuel also has no significant influence except for the duration of the experiment. The concentration of CO is scattered in the range of 1.9% and 4.3% when explosions occur. Hence, the accumulation of CO is considered not to be the direct cause for the smoke explosion. The triggering factor for smoke explosions is believed to be the flammable limit formed by the mixture of hydrocarbon and CO. The pressure difference caused by the explosion inside the compartment has to be at least 27 Pa for it to be considered as a smoke explosion.

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