Ciências da Vida | Artigos em revistas internacionais / Papers in international journals
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- Increased lung inflammation with oxygen supplementation in tracheotomized spontaneously breathing rabbits: an experimental prospective randomized studyPublication . Machado, Humberto S.; Nunes, Catarina S.; Sá, Paula; Couceiro, António; Silva, Álvaro Moreira da; Águas, ArturBackground Mechanical ventilation is a well–known trigger for lung inflammation. Research focuses on tidal volume reduction to prevent ventilator-induced lung injury. Mechanical ventilation is usually applied with higher than physiological oxygen fractions. The purpose of this study was to investigate the after effect of oxygen supplementation during a spontaneous ventilation set up, in order to avoid the inflammatory response linked to mechanical ventilation. Methods A prospective randomised study using New Zealand rabbits in a university research laboratory was carried out. Rabbits (n = 20) were randomly assigned to 4 groups (n = 5 each group). Groups 1 and 2 were submitted to 0.5 L/min oxygen supplementation, for 20 or 75 minutes, respectively; groups 3 and 4 were left at room air for 20 or 75 minutes. Ketamine/xylazine was administered for induction and maintenance of anaesthesia. Lungs were obtained for histological examination in light microscopy. Results All animals survived the complete experiment. Procedure duration did not influence the degree of inflammatory response. The hyperoxic environment was confirmed by blood gas analyses in animals that were subjected to oxygen supplementation, and was accompanied with lower mean respiratory rates. The non-oxygen supplemented group had lower mean oxygen arterial partial pressures and higher mean respiratory rates during the procedure. All animals showed some inflammatory lung response. However, rabbits submitted to oxygen supplementation showed significant more lung inflammation (Odds ratio = 16), characterized by more infiltrates and with higher cell counts; the acute inflammatory response cells was mainly constituted by eosinophils and neutrophils, with a relative proportion of 80 to 20% respectively. This cellular observation in lung tissue did not correlate with a similar increase in peripheral blood analysis. Conclusions Oxygen supplementation in spontaneous breathing is associated with an increased inflammatory response when compared to breathing normal room air. This inflammatory response was mainly constituted with polymorphonuclear cells (eosinophils and neutrophils). As confirmed in all animals by peripheral blood analyses, the eosinophilic inflammatory response was a local organ event.
- Spontaneous one-lung ventilation increases the lung inflammatory response : an experimental pilot studyPublication . Machado, Humberto S.; Sá, Paula; Nunes, Catarina S.; Couceiro, António; Silva, Álvaro Moreira da; Águas, ArturStudy objective: The purpose of this study was to investigate if spontaneous one-lung ventilation would induce any type of inflammatory lung response when compared to spontaneous two-lung ventilation and its intensity, by quantification of inflammatory cells in lung histology at the end of the procedure. Design: In vivo prospective randomised animal study Setting: University research laboratory Subjects: New Zealand rabbits Interventions: Rabbits (n=20) were randomly assigned to 4 groups (n=5 each group). Groups 1 and 2 were submitted to one-lung ventilation, during 20 and 75 minutes respectively; groups 3 and 4 were submitted to two-lung ventilation during 20 and 75 minutes and considered controls. Ketamine/xylazine was administered for induction and maintenance of anesthesia. One-lung ventilation was achieved by administration of air into the interpleural space, and left lung collapse was visually confirmed through the centre of the diaphragm. Measurements: Lung histology preparations were observed under light microscopy for quantification of the inflammatory response (light, moderate and severe). Main results: All subjects had at least light inflammatory response. However, rabbits submitted to one-lung ventilation had a statistically significant value for the occurrence of moderate inflammation (p<0.05). The inflammatory response found included mainly eosinophils, with an average proportion of 75/25 to other polymorphonuclear cells. No differences between groups were found regarding gas exchange, heart rate and respiratory rate. Conclusions: In this spontaneous one-lung ventilation model, lung collapse was positively associated with a greater inflammatory response when compared to normal two-lung ventilation.