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JUSTIFICATIVA E OBJETIVOS: A fisioterapia respiratória (FR) em pacientes submetidos a suporte ventilatório invasivo, atua diretamente no sistema ventilatório podendo alterar a mecânica pulmonar através da complacência pulmonar dinâmica (Cdyn) e da resistência do sistema respiratório (Rsr). Porém, as alterações descritas após a realização de FR permanecem controversas. O objetivo deste estudo foi avaliar as alterações da mecânica pulmonar em pacientes em ventilação mecânica invasiva (VMI). MÉTODO: Foi realizado estudo prospectivo e aleatório, controlado do tipo cruzado, incluindo pacientes com mais de 48 horas em VMI. Os protocolos de fisioterapia respiratória (PF) e de aspiração traqueal isolada (PA) foram aleatorizados para a ordem de aplicação, com intervalo de 24 horas entre eles. Dados da mecânica pulmonar e das variáveis cardiorrespiratórias foram coletados antes da aplicação do protocolo, imediatamente após; 30 minutos e 120 minutos após a aplicação dos protocolos. RESULTADOS: Doze pacientes completaram o estudo. A pneumonia foi a causa mais comum de insuficiência respiratória (IRpA). Não houve diferença estatisticamente significativa entre os grupos em relação à Cdyn, volume de ar corrente (VAC) e volume-minuto (VM). A Rsr diminuiu de forma significativa imediatamente após (de 10,4 ± 3 cmH2O/L/seg para 8,9 ± 2 cmH2O/L/seg; p < 0,02), 30 minutos após (de 10,4 ± 3 cmH2O/L/seg para 9 ± 2 cmH2O/L/seg; p < 0,01) e 120 min após (de 10,4 ± 3 cmH2O/L/seg para 9 ± 2 cmH2O/L/seg; p < 0,03) a aplicação do protocolo de fisioterapia respiratória. Quando comparado com o protocolo de aspiração traqueal isolada foi significativamente menor nos momentos 30 (9 ± 2 cmH2O/L/seg versus 10,2 ± 2 cmH2O/L/seg; p < 0,04) e 120 minutos (9 ± 2 cmH2O/L/segundo versus 10,4 ± 3 cmH2O/L/seg; p < 0,04). CONCLUSÕES: O protocolo de fisioterapia respiratória foi eficaz na diminuição da Rsr quando comparado com o protocolo de aspiração. Essa diminuição manteve-se duas horas após a sua aplicação, o que não ocorreu quando realizada apenas a aspiração traqueal isolada.BACKGROUND AND OBJECTIVES: The chest physiotherapy (CP) in patients submitted to invasive support ventilation acts directly in the breathing system, and it could alter the lung mechanics through the dynamic lung compliance (DynC) and resistance of the breathing system (Rbs). However the alterations after the accomplishment of CP are still controversy. The objective of this study was to evaluate the alterations of the lung mechanics in patients in invasive mechanical ventilation (IMV). METHODS: It was a prospective, randomized, and controlled and crossover study, with patient with more than 48 hours in IMV. The protocol of chest physiotherapy and isolated tracheal aspiration they were randomized for the application order with a window of 24 hours among them. Data of lung mechanics and its varied cardiorespiratory were collected moments before the protocol, immediately after the application of the protocol, 30 minutes and 120 minutes after the application of the protocols. RESULTS: Twelve patients completed the study. Pneumonia was the mean cause respiratory failure (RF). There was not statistical difference among the groups in relation to Cdyn, volume tidal (Vt) and volume minute (Ve). Rbs decreased in a significant way immediately after (of 10.4 ± 3 cmH2O/L/seg for 8.9 ± 2 cmH2O/L/seg; p < 0.02), 30 minutes after (of 10.4 ± 3 cmH2O/L/seg for 9 ± 2 cmH2O/L/seg; p < 0.01) and 120 minutes after (of 10.4 ± 3 cmH2O/L/seg for 9 ± 2 cmH2O/L/seg; p < 0.03) application the protocol of chest physiotherapy. When compared with the protocol of isolated tracheal aspiration it was significantly smaller in the 30 (9 ± 2 cmH2O/L/seg versus10.2 ± 2 cmH2O/L/seg; p < 0.04) and 120 minutes (9 ± 2 cmH2O/L/seg versus 10.4 ± 3 cmH2O/L/seg; p < 0.04). CONCLUSIONS: The protocol of chest physiotherapy was effective in the decrease of Rsr when compared with the aspiration protocol. That decrease was maintained for two hours after its application, what did not happen when only the just accomplished the tracheal aspiration was performed isolated.

Introduction: Mouse models of emphysema are important tools for testing different therapeutic strategies. The aim of this study was to develop a mouse model of emphysema induced by different doses of elastase in order to produce different degrees of severity. Methods: Thirty female mice (C57BL/6) were used in this study. Different doses of porcine pancreatic elastase were administered intratracheally once a week for four weeks, as follows: 0.1 U (n=8), 0.15 U (n=7), and 0.2 U (n=7). Control mice (n=8) received 50 microL of sterile saline solution intratracheally. Lung mechanics were analyzed by plethysmography. Mean linear intercept and volume fraction occupied by collagen and elastic fibers were determined. Results: An increase in lung resistance was observed with 0.2 U of elastase [median (P-25-P75): 2.02 (1.67; 2.34) cmH2O.s/mL], as well as a decrease in tidal volume and minute ventilation. Peak expiratory flow increased significantly in the groups treated with 0.15 U and 0.2 U of elastase. Mean linear intercept was higher with 0.15 U and 0.2 U of elastase, with destruction of alveolar walls [median (P-25-P75): 30.31 (26.65-43.13) microm and 49.49 (31.67-57.71) microm respectively]. The volume fraction occupied by collagen and elastic fibers was lower in the group receiving 0.2 U of elastase. Conclusion: Four intratracheal instillations of 0.2 U of elastase once a week induced changes in lung function and histology, producing an experimental model of severe pulmonary emphysema, whereas 0.15 U resulted in only histological changes.