Diversas estratégias de ventilação mecânica que estabelecem limites na pressão e volume intratorácicas têm sido propostas para pacientes com síndrome de angustia respiratória aguda (SARA). Estas recomendações são baseadas na observação de que a ventilação mecânica com volume corrente excessivo ou pressão positiva expiratória final (PEEP) insuficiente pode ocasionar lesões pulmonares graves, decorrentes de superdistensão de unidades alveolares. O objetivo do atual estudo foi aplicar manobras de recrutamento alveolar e PEEP em pulmões submetidos à lesão pulmonar aguda (LPA) através da administração de HCl . Foram utilizados 24 suínos Landrace - Largewhite, do sexo feminino, pesando entre 25 e 35 Kg. Após a anestesia os animais foram submetidos à ventilação com volume controlado (6 a 8 ml/Kg) e foram randomizados em 4 grupos: GI (6 animais não submetidos a LPA e tratados com PEEP progressivo de 5, 10, 15 e 20 cmH2O e regressivo de 20 a 5 cmH2O); GII (6 animais não submetidos a LPA e tratados com PEEP progressivo de 5, 10, 15 e 20 cmH2O e regressivo de 20 a 5 cmH2O associado a 3 manobras de recrutamento consecutivas, com pressão de 30 cmH2O antes de cada alteração do PEEP); GIII (6 animais submetidos a 1 hora de LPA por HCl e tratados como GI) e GIV (6 animais submetidos a 1 hora de LPA por HCl e tratados como GII). A mecânica respiratória e oxigenação foram avaliadas a cada 20 minutos, acompanhando cada alteração do PEEP. A LPA foi observada através de severas alterações na oxigenação e mecânica respiratória. A administração de MR associada a PEEP foi capaz de restaurar os valores controle, porém, os elevados valores de PEEP e CPAP foram acompanhados de significantes alterações hemodinâmicas quando comparadas com os animais que não foram submetidos a LPA. O derrecrutamento alveolar ocorreu provavelmente quando os valores de PEEP foram retornados para 5cmH2O. As lesões pulmonares foram uniformes nos animais que foram submetidos ao HCl, evidenciadas pela presença de necrose, hemorragia, congestão e infiltrado de células inflamatórias no interstício e nos alvéolos. O modelo experimental de lesão pulmonar aguda foi adequado para estudar MR seguidas por PEEP, pois apresentou importantes alterações dos valores de oxigenação e complacência, observado 1 hora após a instilação do HCl.Os valores de PEEP de 5cmH2O foram incapazes de manter o recrutamento no momento final do estudo, enquanto que os valores de PEEP de 10cmH2O foram suficientes para restabelecer a oxigenação com mínima alteração hemodinâmica. A complacência não melhorou após as manobras. Futuros estudos são necessários para confirmar os resultados obtidos, especialmente para mostrar que a manutenção do PEEP de 10cmH2O é suficientes para manter o recrutamento após as MR / Different mechanical ventilation strategies which define limits of intrathoracic pressures and volumes are being proposed for patients with acute respiratory distress syndrome (ARDS). These recommendations are based on observations that mechanical ventilation with excessive tidal volumes or insufficient values of positive end expiratory pressure (PEEP) can cause severe lung injury due to overinflation. The aim of the present study was to apply recruitment maneuvers (RM) and PEEP in lungs submitted to acute lung injury (ALI) due to the administration of hydrochloride acid. Twenty four female Landrace – Largewhite pigs, weighing 25 to 35 Kg were used. After anesthesia, animals were submitted to volume controlled mechanical ventilation (6 to 8ml/kg) and were randomly allocated in four groups of 6 animals each: GI animals without ALI and treated with progressive values of PEEP (5, 10, 15 and 20 cmH2O) or regressive (20 to 5 cm H2O); GII animals without ALI and treated with progressive values of PEEP (5, 10, 15 and 20 cmH2O) or regressive (20 to 5 cm H2O) plus 3 consecutive recruitment maneuvers with 30 cmH2O; GIII animals submitted to 1 hour of ALI and treated as GI; GIV animals submitted to 1 hour of ALI and treated as GII. Parameters of respiratory mechanics, ventilation and oxygenation were measured each 20 minutes according to the change of the PEEP values. ALI could be observed by the severe changes of oxygenation and respiratory mechanics noted. The use of RM and PEEP were able to restore control values. Nevertheless, application of high values of PEEP and CPAP were accompanied by significant hemodynamic changes which could be evidenced in animals without ALI. Derecruitment probably occurred when PEEP value reached 5 cmH2O. The lung lesions were uniform in the HCL-injured animals and consisted of necrosis, hemorrhage, congestion, and inflammatory cells infiltration that involved both the interstitium and the alveoli. The experimental model of lung injury was adequate to the study of RM followed by PEEP since significant changes of the oxygenation and compliance values could be observed 1 hour after acid instillation. PEEP values of 5cmH2O were incapable to maintain recruitment at the end of the observation period, while 10 cmH2O were sufficient to promote the reestablishment of oxygenation index with minimal hemodynamic changes. Compliance did not improve during the maneuvers. Further studies are necessary to confirm the results obtained, especially to show that the maintenance of a PEEP value of 10 cmH2O are sufficient to maintain recruitment after the RM

Diversas estratégias de ventilação mecânica que estabelecem limites na pressão e volume intratorácicas têm sido propostas para pacientes com síndrome de angustia respiratória aguda (SARA). Estas recomendações são baseadas na observação de que a ventilação mecânica com volume corrente excessivo ou pressão positiva expiratória final (PEEP) insuficiente pode ocasionar lesões pulmonares graves, decorrentes de superdistensão de unidades alveolares. O objetivo do atual estudo foi aplicar manobras de recrutamento alveolar e PEEP em pulmões submetidos à lesão pulmonar aguda (LPA) através da administração de HCl . Foram utilizados 24 suínos Landrace - Largewhite, do sexo feminino, pesando entre 25 e 35 Kg. Após a anestesia os animais foram submetidos à ventilação com volume controlado (6 a 8 ml/Kg) e foram randomizados em 4 grupos: GI (6 animais não submetidos a LPA e tratados com PEEP progressivo de 5, 10, 15 e 20 cmH2O e regressivo de 20 a 5 cmH2O); GII (6 animais não submetidos a LPA e tratados com PEEP progressivo de 5, 10, 15 e 20 cmH2O e regressivo de 20 a 5 cmH2O associado a 3 manobras de recrutamento consecutivas, com pressão de 30 cmH2O antes de cada alteração do PEEP); GIII (6 animais submetidos a 1 hora de LPA por HCl e tratados como GI) e GIV (6 animais submetidos a 1 hora de LPA por HCl e tratados como GII). A mecânica respiratória e oxigenação foram avaliadas a cada 20 minutos, acompanhando cada alteração do PEEP. A LPA foi observada através de severas alterações na oxigenação e mecânica respiratória. A administração de MR associada a PEEP foi capaz de restaurar os valores controle, porém, os elevados valores de PEEP e CPAP foram acompanhados de significantes alterações hemodinâmicas quando comparadas com os animais que não foram submetidos a LPA. O derrecrutamento alveolar ocorreu provavelmente quando os valores de PEEP foram retornados para 5cmH2O. As lesões pulmonares foram uniformes nos animais que foram submetidos ao HCl, evidenciadas pela presença de necrose, hemorragia, congestão e infiltrado de células inflamatórias no interstício e nos alvéolos. O modelo experimental de lesão pulmonar aguda foi adequado para estudar MR seguidas por PEEP, pois apresentou importantes alterações dos valores de oxigenação e complacência, observado 1 hora após a instilação do HCl.Os valores de PEEP de 5cmH2O foram incapazes de manter o recrutamento no momento final do estudo, enquanto que os valores de PEEP de 10cmH2O foram suficientes para restabelecer a oxigenação com mínima alteração hemodinâmica. A complacência não melhorou após as manobras. Futuros estudos são necessários para confirmar os resultados obtidos, especialmente para mostrar que a manutenção do PEEP de 10cmH2O é suficientes para manter o recrutamento após as MR / Different mechanical ventilation strategies which define limits of intrathoracic pressures and volumes are being proposed for patients with acute respiratory distress syndrome (ARDS). These recommendations are based on observations that mechanical ventilation with excessive tidal volumes or insufficient values of positive end expiratory pressure (PEEP) can cause severe lung injury due to overinflation. The aim of the present study was to apply recruitment maneuvers (RM) and PEEP in lungs submitted to acute lung injury (ALI) due to the administration of hydrochloride acid. Twenty four female Landrace – Largewhite pigs, weighing 25 to 35 Kg were used. After anesthesia, animals were submitted to volume controlled mechanical ventilation (6 to 8ml/kg) and were randomly allocated in four groups of 6 animals each: GI animals without ALI and treated with progressive values of PEEP (5, 10, 15 and 20 cmH2O) or regressive (20 to 5 cm H2O); GII animals without ALI and treated with progressive values of PEEP (5, 10, 15 and 20 cmH2O) or regressive (20 to 5 cm H2O) plus 3 consecutive recruitment maneuvers with 30 cmH2O; GIII animals submitted to 1 hour of ALI and treated as GI; GIV animals submitted to 1 hour of ALI and treated as GII. Parameters of respiratory mechanics, ventilation and oxygenation were measured each 20 minutes according to the change of the PEEP values. ALI could be observed by the severe changes of oxygenation and respiratory mechanics noted. The use of RM and PEEP were able to restore control values. Nevertheless, application of high values of PEEP and CPAP were accompanied by significant hemodynamic changes which could be evidenced in animals without ALI. Derecruitment probably occurred when PEEP value reached 5 cmH2O. The lung lesions were uniform in the HCL-injured animals and consisted of necrosis, hemorrhage, congestion, and inflammatory cells infiltration that involved both the interstitium and the alveoli. The experimental model of lung injury was adequate to the study of RM followed by PEEP since significant changes of the oxygenation and compliance values could be observed 1 hour after acid instillation. PEEP values of 5cmH2O were incapable to maintain recruitment at the end of the observation period, while 10 cmH2O were sufficient to promote the reestablishment of oxygenation index with minimal hemodynamic changes. Compliance did not improve during the maneuvers. Further studies are necessary to confirm the results obtained, especially to show that the maintenance of a PEEP value of 10 cmH2O are sufficient to maintain recruitment after the RM

INTRODUÇÃO: A lesão pulmonar da nova displasia broncopulmonar se caracteriza por uma diminuição da septação alveolar e do desenvolvimento vascular, ocorre um bloqueio no desenvolvimento pulmonar e consequentemente uma diminuição da alveolarização. A lesão pulmonar ocorre devido à associação de diversos fatores, incluindo a prematuridade, defesas antioxidantes inadequadas, e a ativação da resposta inflamatória. A exposição prolongada ao oxigênio também resulta em anormalidades na formação e na morfologia dos alvéolos, com redução tanto do volume pulmonar como da área de superfície interna alveolar. O objetivo do presente estudo foi comparar dois modelos de indução de lesão pulmonar através da exposição à hiperoxia prolongada em coelhos. MÉTODOS: Coelhas grávidas da raça New-Zealand-White foram sedadas para realização do parto cesáreo no 28º dia de gestação (termo = 31dias), coelhos prematuros foram expostos ao ar ambiente ou FiO295%. Outro grupo nasceu no 29º dia de gestação e foi exposto ao ar ambiente ou a uma FiO2=80%. Os animais foram mantidos em incubadora com controle de temperatura e alimentação e uma fórmula especial de leite similar ao leite de coelha por 11 dias. Desta forma, foram constituídos quatro grupos de estudo: Ar ambiente com 28 dias de gestação (Ar 28); exposição ao oxigênio (FiO2 95%) com 28 dias de gestação (O2 28); ar ambiente com 29 dias de gestação (Ar 29); exposição ao oxigênio (FiO2 = 80%) com 29 dias de gestação (O2 29). Após o sacrifício os pulmões foram fixados com 30 cmH2O de pressão transtraqueal. As lâminas do tecido pulmonar foram submetidas às seguintes colorações: hematoxilina e eosina para análise morfométrica; Weigert, resorcina-orceína modificado para a análise das fibras elásticas e Picrosirius para análise do colágeno. Foi realizada a contagem do Intercepto Linear Médio (Lm), determinada a Área de Superfície Interna (ISA), o número de alvéolos por campo microscópico, o espessamento septal e a proporção de fibras elásticas e colágenas. Análise Estatística: As variáveis contínuas foram analisadas por ANOVA One Way e a análise da sobrevida foi realizada através de uma curva de Kaplan-Meyer. O nível de significância adotado foi de 0.05. RESULTADOS: A sobrevida nos grupos de 29 dias foi melhor quando comparados com o grupo 28 dias. A hiperoxia bloqueou o desenvolvimento normal do pulmão, demonstrado por um aumento no Lm, uma diminuição significativa na ISA, uma diminuição no número de alvéolos, um aumento na espessura do septo interalveolar e também um aumento na proporção de fibras elásticas e uma diminuição na proporção de fibras colágenas nos dois grupos de animais expostos ao oxigênio em relação aos grupos que permaneceram em ar ambiente. CONCLUSÕES: Em coelhos prematuros o uso de uma concentração de oxigênio menor e um dia a mais de gestação reduziu a taxa de mortalidade mantendo os achados histopatológicos compatíveis aos da displasia broncopulmonar em humanos / INTRODUCTION: The lung injury of the \"new\" bronchopulmonary dysplasia is characterized by a decrease in alveolar septation and vascular development, resulting in a pulmonary arrest and a decrease in alveolarization. Lung damage occurs due to the association of many factors, including prematurity, inadequate antioxidant defenses and activation of the inflammatory response. Prolonged exposure to oxygen also results in abnormalities in the formation and morphology of the alveoli, with reduced lung volume and alveolar internal surface area. The aim of this study was to compare two models of lung injury induced by prolonged exposure to hyperoxia in rabbits. METHODS: New Zealand-White pregnant rabbits were sedated to perform a cesarean section on day 28 of gestation (term = 31days), premature rabbits were exposed to room air or FiO295%. Another group of animals was born at day 29 of gestation and was exposed to room air or FiO2=80%. The animals were kept in an incubator with temperature control and fed with a special milk formula similar to rabbit milk for 11 days. Four study groups were formed: Room air and 28 days of gestation (Air 28); exposure to oxygen (FiO295%) and 28 days of gestation (O2 28); room air and 29 days of gestation (Air 29 ); exposure to oxygen (FiO2=80%) and 29 days of gestation (O2 29). For microscopic evaluation, after sacrifice the lungs were fixed in situ at a constant inflation pressure of 30 cm H20. Lung slices were processed for hematoxylin-eosin staining - for morphometric analysis, Weigert\'s resorcin-orcein modified for the analysis of elastic fibers and Picrosirius - for analysis of collagen. The mean linear intercept (Lm), the internal surface area (ISA), the number of alveoli, the septal thickness and the proportion of elastic and collagen fibers were quantified. Statistical analysis was by One Way ANOVA for continuous variables, survival analysis was performed using a Kaplan-Meyer plot. The level of significance was 0.05. RESULTS: Survival in both 29 days groups was better when compared with 28 days groups. Hyperoxia impaired the normal development of the lung, demonstrated by an increase in Lm, a significant decrease in ISA, a decrease in the alveoli number, an increase in the septal thickness and an increase in the proportion of fibers elastic and a decrease in the proportion of collagen fibers in oxygen exposed animals. CONCLUSIONS: In premature rabbits using a lower concentration of oxygen and one more day of gestation reduced the mortality rate maintaining the histopathological findings similar to bronchopulmonary dysplasia in humans

Introdução: A prática regular de exercício tem sido grandemente associada a efeitos benéficos em doenças pulmonares crônicas como asma e doença pulmonar obstrutiva crônica. Poucos estudos têm avaliado os benefícios do exercício aeróbico na lesão pulmonar aguda (LPA). Objetivo: Neste estudo nós investigamos os mecanismos envolvidos no papel do exercício físico em diminuir os danos pulmonares causados pela LPA induzida por lipopolissacarídeo (LPS). Métodos: Camundongos Balb/c foram divididos em quatro grupos: Controle (CTR), Exercício (Exe), LPS e Exercício+LPS (Exe+LPS). Os animais dos grupos Exe e Exe+LPS foram treinados em baixa intensidade por 60 minutos/dia, 3x/semana, durante 5 semanas. A instilação intratraqueal de LPS (200 /animal) foi realizada 48 horas após o último teste físico nos grupos LPS e Exe+LPS. Vinte e quatro horas após a instilação de LPS nós analisamos os níveis de óxido nítrico exalado (NO), a mecânica respiratória e a densidade de neutrófilos no tecido pulmonar. Nós analisamos também os níveis de extravasamento de proteína, contagem de células totais e diferenciais e os níveis de IL-1, IL-6, KC, IL-10 and TNF- no lavado bronco-alveolar (LBA). Os níveis de IL-6 e IL-10 também foram avaliados no plasma e tecido pulmonar. A expressão de receptores de glicocorticóide (Gre) e da enzima superóxido dismutase (SOD) foi analisada no tecido pulmonar. As atividades enzimáticas de glutationa peroxidade (GPX), catalase (CAT), glutationa redutase (GR), e SOD foram determinadas no homogenato de pulmão por espectrofotometria. O nível de malonaldeído (MDA) foi quantificado no homogenato de pulmão. Resultados: A instilação de LPS resultou em aumento nos níveis de NO exalado (p<0,01), aumento do número de células e neutrófilos no LBA (p<0,001), aumento do número de neutrófilos no parênquima pulmonar (p<0,001), aumento dos valores de resistência e elastância pulmonar (p=0,01), aumento dos níveis de extravasamento de proteína (p0,02), aumento dos níveis de IL-6 e IL-10 no plasma (p<0,02) e aumento dos níveis de IL-1, IL-6 e KC no LBA (p0,005), comparado ao grupo CTR. O exercício aeróbico (grupo Exe+LPS) diminuiu significativamente os níveis de NO exalado (p=0,006), a densidade de neutrófilos no parênquima pulmonar (p=0,004), os valores de resistência e elastância pulmonar (p = 0,003), aumentou a expressão de IL-6, IL-10 e Gre no tecido pulmonar (p0,04) e aumentou o nível de IL- 1 no LBA (p=0,04) comparado ao grupo LPS. Conclusão: Nossos resultados mostram que o exercício desenvolve um importante papel em proteger o pulmão dos efeitos inflamatórios da LPA induzida por LPS. Os efeitos do exercício são principalmente mediados pelo aumento da expressão de citocinas antiinflamatórias, sugerindo que o exercício aeróbico pode modular o balanço inflamatório, antiinflamatório na fase inicial na SARA. / Background: The regular practice of exercise has been increasingly associated to benefic effects on chronic pulmonary conditions such as asthma and chronic obstructive pulmonary disease. Few studies have also reported the effects of aerobic exercise on acute lung injury (ALI). Objective: In this study we investigated the mechanisms involved in the role of exercise in attenuating the pulmonary changes in a model of lipopolysaccharide (LPS)-induced ALI. Methods: BALB/c mice were divided into four groups: Control (CTR), Exercise (Exe), LPS, and Exercise + LPS (Exe+LPS). Mice from Exe and Exe+LPS groups were trained at low intensity exercise for 60 minutes/day, 3 days/week, during 5 weeks. Intratracheal instillation of LPS (200/mouse) was performed 48 hours after the last physical test in the LPS and Exe+LPS groups. Twenty-four hours after LPS instillation we measured exhaled nitric oxide (NO), respiratory mechanics, and the density of neutrophils in lung tissue. We further analyzed protein leakage, total and differential cell counts and the levels of IL-1, IL-6, KC, IL-10 and TNF- in bronchoalveolar lavage fluid (BALF). IL-6 and IL-10 levels were also evaluated in serum and lung tissue. The expression of glucocorticoid receptors (Gre) and superoxide dismutase (SOD) was analyzed in lung tissue. Enzymatic activity of glutathione peroxidase (GPX), catalase (CAT), glutathione reductase (GR) and SOD was determined in lung homogenates by spectrophotometry. The level of malondialdehyde (MDA) was quantified in lung homogenates. Results: LPS instillation resulted in increased levels of exhaled NO (p<0.01), higher number of total cells and neutrophils in the BALF (p<0.001), higher number of neutrophils in the lung parenchyma (p<0.001), higher values of pulmonary resistance and elastance (p=0.01), increase of protein leakage (p0.02), increase of IL-6 and IL-10 level in serum (p<0.02) and increase in IL-1, IL-6 and KC levels in BALF (p0.005), compared to the CTR group. Aerobic exercise (Exe+LPS group) resulted in significantly lower exhaled NO levels (p=0.006), lower density of neutrophils in the lung parenchyma (p=0.004), lower pulmonary resistance and elastance values (p = 0.003), increased expression of IL-6, IL-10 and Gre in lung tissue (p0.04) and increased IL-1 level in BALF (p=0.04) compared to the LPS group. Conclusion: Our results show that exercise plays an important role in protecting the lung from the inflammatory effects of LPS-induced ALI. The effects of exercise are mainly mediated by the increased expression of anti-inflammatory cytokines, suggesting that aerobic preconditioning can modulate the inflammatory-anti-inflammatory balance in the early phase of ARDS.

INTRODUÇÃO: A lesão pulmonar da nova displasia broncopulmonar se caracteriza por uma diminuição da septação alveolar e do desenvolvimento vascular, ocorre um bloqueio no desenvolvimento pulmonar e consequentemente uma diminuição da alveolarização. A lesão pulmonar ocorre devido à associação de diversos fatores, incluindo a prematuridade, defesas antioxidantes inadequadas, e a ativação da resposta inflamatória. A exposição prolongada ao oxigênio também resulta em anormalidades na formação e na morfologia dos alvéolos, com redução tanto do volume pulmonar como da área de superfície interna alveolar. O objetivo do presente estudo foi comparar dois modelos de indução de lesão pulmonar através da exposição à hiperoxia prolongada em coelhos. MÉTODOS: Coelhas grávidas da raça New-Zealand-White foram sedadas para realização do parto cesáreo no 28º dia de gestação (termo = 31dias), coelhos prematuros foram expostos ao ar ambiente ou FiO295%. Outro grupo nasceu no 29º dia de gestação e foi exposto ao ar ambiente ou a uma FiO2=80%. Os animais foram mantidos em incubadora com controle de temperatura e alimentação e uma fórmula especial de leite similar ao leite de coelha por 11 dias. Desta forma, foram constituídos quatro grupos de estudo: Ar ambiente com 28 dias de gestação (Ar 28); exposição ao oxigênio (FiO2 95%) com 28 dias de gestação (O2 28); ar ambiente com 29 dias de gestação (Ar 29); exposição ao oxigênio (FiO2 = 80%) com 29 dias de gestação (O2 29). Após o sacrifício os pulmões foram fixados com 30 cmH2O de pressão transtraqueal. As lâminas do tecido pulmonar foram submetidas às seguintes colorações: hematoxilina e eosina para análise morfométrica; Weigert, resorcina-orceína modificado para a análise das fibras elásticas e Picrosirius para análise do colágeno. Foi realizada a contagem do Intercepto Linear Médio (Lm), determinada a Área de Superfície Interna (ISA), o número de alvéolos por campo microscópico, o espessamento septal e a proporção de fibras elásticas e colágenas. Análise Estatística: As variáveis contínuas foram analisadas por ANOVA One Way e a análise da sobrevida foi realizada através de uma curva de Kaplan-Meyer. O nível de significância adotado foi de 0.05. RESULTADOS: A sobrevida nos grupos de 29 dias foi melhor quando comparados com o grupo 28 dias. A hiperoxia bloqueou o desenvolvimento normal do pulmão, demonstrado por um aumento no Lm, uma diminuição significativa na ISA, uma diminuição no número de alvéolos, um aumento na espessura do septo interalveolar e também um aumento na proporção de fibras elásticas e uma diminuição na proporção de fibras colágenas nos dois grupos de animais expostos ao oxigênio em relação aos grupos que permaneceram em ar ambiente. CONCLUSÕES: Em coelhos prematuros o uso de uma concentração de oxigênio menor e um dia a mais de gestação reduziu a taxa de mortalidade mantendo os achados histopatológicos compatíveis aos da displasia broncopulmonar em humanos / INTRODUCTION: The lung injury of the \"new\" bronchopulmonary dysplasia is characterized by a decrease in alveolar septation and vascular development, resulting in a pulmonary arrest and a decrease in alveolarization. Lung damage occurs due to the association of many factors, including prematurity, inadequate antioxidant defenses and activation of the inflammatory response. Prolonged exposure to oxygen also results in abnormalities in the formation and morphology of the alveoli, with reduced lung volume and alveolar internal surface area. The aim of this study was to compare two models of lung injury induced by prolonged exposure to hyperoxia in rabbits. METHODS: New Zealand-White pregnant rabbits were sedated to perform a cesarean section on day 28 of gestation (term = 31days), premature rabbits were exposed to room air or FiO295%. Another group of animals was born at day 29 of gestation and was exposed to room air or FiO2=80%. The animals were kept in an incubator with temperature control and fed with a special milk formula similar to rabbit milk for 11 days. Four study groups were formed: Room air and 28 days of gestation (Air 28); exposure to oxygen (FiO295%) and 28 days of gestation (O2 28); room air and 29 days of gestation (Air 29 ); exposure to oxygen (FiO2=80%) and 29 days of gestation (O2 29). For microscopic evaluation, after sacrifice the lungs were fixed in situ at a constant inflation pressure of 30 cm H20. Lung slices were processed for hematoxylin-eosin staining - for morphometric analysis, Weigert\'s resorcin-orcein modified for the analysis of elastic fibers and Picrosirius - for analysis of collagen. The mean linear intercept (Lm), the internal surface area (ISA), the number of alveoli, the septal thickness and the proportion of elastic and collagen fibers were quantified. Statistical analysis was by One Way ANOVA for continuous variables, survival analysis was performed using a Kaplan-Meyer plot. The level of significance was 0.05. RESULTS: Survival in both 29 days groups was better when compared with 28 days groups. Hyperoxia impaired the normal development of the lung, demonstrated by an increase in Lm, a significant decrease in ISA, a decrease in the alveoli number, an increase in the septal thickness and an increase in the proportion of fibers elastic and a decrease in the proportion of collagen fibers in oxygen exposed animals. CONCLUSIONS: In premature rabbits using a lower concentration of oxygen and one more day of gestation reduced the mortality rate maintaining the histopathological findings similar to bronchopulmonary dysplasia in humans

The goal of lung-protective mechanical ventilation is to provide life-sustaining support of gas exchange while minimizing the risk of ventilator-induced lung injury. Multi-frequency oscillatory ventilation (MFOV) was proposed as an alternative lung-protective modality, in which multiple frequencies of pressure and flow oscillations are delivered simultaneously at the airway opening and allowed to distribute throughout the lung in accordance with regional mechanical properties. The distribution of oscillatory flow is frequency-dependent, such that regions overventilated at one frequency may be underventilated at another. Thus the central thesis of this work was that ventilation heterogeneity is frequency-dependent, and therefore ventilation with multiple simultaneous frequencies can be optimized to reduce the risk of ventilator-induced lung injury. Simulations in computational models of distributed oscillatory flow and gas transport demonstrated the sensitivity of regional ventilation heterogeneity to subject size, ventilation frequency, and injury severity. Although the risk of injury in the model associated with strain or strain rate individually was minimized by single-frequency ventilation, the risk of injury associated with mechanical power in lung parenchymal tissue was minimized by MFOV. In an experimental model of acute lung injury, MFOV was associated with reductions in the magnitude and spatial gradient of regional lung strain estimated by four-dimensional CT image registration, as well as increased rates of regional gas transport estimated by wash-in of xenon tracer gas. In conclusion, computational models demonstrated the potential for optimization of MFOV waveforms, and experimental trials demonstrated evidence of improved regional ventilation during MFOV.

Ischemia-reperfusion (IR) injury is a severe complication in lung transplantation characterized by inflammation, alveolar damage, and hypoxemia. Alpha 1-antitrypsin (A1AT), a protease inhibitor, is currently used clinically for the treatment of A1AT deficiency emphysema. A1AT has been shown to have the potential to reduce IR injury through its anti-inflammatory and anti-apoptotic effects. We hypothesized that A1AT will ameliorate IR injury through these effects. We tested A1AT in two models of IR: a cell culture model of simulated lung transplantation and a rat in situ pulmonary ligation model. In cell culture, we found that A1AT exerts its protective effects by inhibiting cell death and inflammatory cytokine release in a dose-dependent manner. In the rat pulmonary ischemia-reperfusion model, we found that A1AT improved lung function by inhibiting apoptosis and inflammation. There is potential for future application of A1AT in the treatment of IR injury in lung transplantation.

Ischemia-reperfusion (IR) injury is a severe complication in lung transplantation characterized by inflammation, alveolar damage, and hypoxemia. Alpha 1-antitrypsin (A1AT), a protease inhibitor, is currently used clinically for the treatment of A1AT deficiency emphysema. A1AT has been shown to have the potential to reduce IR injury through its anti-inflammatory and anti-apoptotic effects. We hypothesized that A1AT will ameliorate IR injury through these effects. We tested A1AT in two models of IR: a cell culture model of simulated lung transplantation and a rat in situ pulmonary ligation model. In cell culture, we found that A1AT exerts its protective effects by inhibiting cell death and inflammatory cytokine release in a dose-dependent manner. In the rat pulmonary ischemia-reperfusion model, we found that A1AT improved lung function by inhibiting apoptosis and inflammation. There is potential for future application of A1AT in the treatment of IR injury in lung transplantation.

Acute lung injury is marked by profound neutrophil influx along with fluid accumulation that impairs lung function at the cost of high mortality (up to 40%). Neutrophils are activated and their constitutive apoptosis is inhibited during this phase in order to be competent phagocytes over the next few hours. Activated neutrophils release copious amounts of toxic mediators that cause tissue damage leading to impaired barrier function and finally, impaired lung function. Therefore, one of the critical needs is to identify molecules that regulate neutrophil migration and silence activated neutrophils to prevent exuberant tissue damage. Angiostatin is an anti-angiogenic molecule highly expressed in lavage fluid of patients with acute respiratory distress syndrome. Angiostatin has recently been shown to inhibit neutrophil infiltration in mice peritonitis. However, the role of angiostatin in modulating neutrophil physiology and lung inflammation remains unknown. I studied the role of angiostatin, an anti-angiogenic molecule, in neutrophil activation and recruitment <i>in vivo</i> and <i>in vitro</i>. Angiostatin was endocytosed only by activated neutrophils, inhibited neutrophil polarity in fMLP-activated neutrophils probably through integrin &alpha;_V&beta;₃, and inhibited MAPK signalling in LPS-activated neutrophils. Angiostatin suppressed formation of reactive oxygen species and activated caspase-3 in neutrophils in both pre-and post-LPS treatments. Finally, angiostatin reduced adhesion and emigration of neutrophils in post-capillary venules of TNF&alpha;-treated cremaster muscle. The next study was designed to investigate the role of angiostatin in acute lung injury. I used <i>E. coli</i> lipopolysaccharide induced acute lung injury mouse model to test the effects of angiostatin through analyses of bronchoalveolar lavage and lung tissues. In addition, I made novel use of synchrotron diffraction enhanced imaging of mouse lungs to assess lung area and contrast ratios over 9 hours as surrogates for lung inflammation. Subcutaneous treatment with angiostatin reduced neutrophil influx, protein accumulation, lung Gr1+ neutrophils and myeloperoxidase activity, phosphorylated p38 MAPK without affecting the levels of MIP-1&alpha;, IL-1&beta;, KC and MCP-1 in lavage and lung homogenates. Diffraction enhanced imaging showed that angiostatin causes a time-dependent improvement in lung area and lung contrast ratios that reflect improvement in lung edema. Overall, the study shows that angiostatin is a novel inhibitor of acute lung injury in mice. Moreover, DEI offers a highly useful technique in evaluating dynamics of lung inflammation and to investigate the therapeutic impact of new drugs on lung inflammation. I conclude that angiostatin is a novel inhibitor of neutrophil migration, activation and acute lung injury.

Immune cells such as neutrophils and monocytes enter tissues after tissue damage and clear cell debris to allow repair cells such as fibroblasts to close the wound. Monocytes also differentiate into fibroblast-like cells called fibrocytes to mediate wound healing, similar to fibroblasts. However, in abnormal wound healing such as acute respiratory distress syndrome (ARDS) and fibrosing diseases, the accumulation of immune cells such as neutrophils or fibrocytes become detrimental to health. In ARDS, neutrophils accumulate in the lungs and causes additional damage by producing reactive oxygen species (ROS). In fibrosing diseases, increased fibrocyte differentiation is one of the causes that increase extracellular matrix deposition, which leads to severe scar tissue build up. Since there are no effective treatments for ARDS or fibrosing diseases, understanding the regulation of neutrophil activation or fibrocyte differentiation could be helpful to develop new effective therapies. The Gomer lab has found several factors that either promote or inhibit fibrocyte differentiation. The pro-fibrotic cytokines such as IL-4 and IL-13 potentiate fibrocyte differentiation while the plasma protein serum amyloid P (SAP), crosslinked IgG, and the pro-inflammatory cytokines IFN-γ and IL-12 inhibit fibrocyte differentiation. In this thesis, I have now shown that additional factors such as toll-like receptor 2 (TLR2) agonists and low molecular weight hyaluronic acid (LMWHA) inhibit fibrocyte differentiation, while high molecular weight hyaluronic acid (HMWHA) potentiate fibrocyte differentiation. The accumulation of neutrophils in the lungs is one of the major factors that debilitate the health of a patient in ARDS. Since neutrophils have Fc receptors, I examined the effect of SAP on neutrophil spreading, adherence, activation, and accumulation. SAP inhibits neutrophil spreading induced by cell debris and TNF-α induced adhesion, but SAP is unable to have any effect on classic neutrophil adhesion molecules or the production of hydrogen peroxide. SAP inhibits neutrophil accumulation in the lungs of bleomycin-injured mice. There is an exciting possibility of using SAP as a therapeutic agent to treat ARDS.