Effects of land cover and air pollution on the risk of preterm births / Efeitos da cobertura de solo e poluição do ar no risco de nascimentos prematuros

ABSTRACT OBJECTIVE To evaluate the association between gestational age and green areas, urban built areas, and the concentration of particulate matter 2.5 (PM2.5) in the city of São Paulo, analyzing the irregular distribution of these areas and pollution levels above the recommended level. METHODS The study population consisted of a cohort of live births from 2012, and data from the Live Birth Information System (Sinasc) of the city of São Paulo were used. Using satellite images and supervised classification, the distribution and quantity of green areas and built areas in the city of São Paulo was obtained, as well as the concentrations of PM2.5. Logistic regressions were used to obtain possible associations. RESULTS The results of the study show that a lower percentage of green areas is significantly associated with a higher chance of preterm births. A higher building density was positively associated with the odds ratio for preterm birth. We did not find any significant associations between air pollution (PM2.5) and preterm births. CONCLUSIONS The results of this study show that greener areas are less associated with preterm births when compared with less green areas.

RESUMO OBJETIVO Avaliar a associação entre a idade gestacional e as áreas verdes, áreas construídas urbanas e a concentração de material particulado 2,5 (MP2,5) em São Paulo, analisando a distribuição irregular dessas áreas e os níveis de poluição acima do recomendado. MÉTODOS A população utilizada no estudo foi a dos nascidos vivos no ano de 2012, com os dados do Sistema de Informações sobre Nascidos Vivo (Sinasc) na cidade de São Paulo. Por meio de imagens de satélites e realizando a classificação supervisionada, obtivemos a distribuição e quantidade de áreas verdes e de áreas construídas, na cidade de São Paulo, assim como as concentrações de MP2,5. Regressões logísticas foram utilizadas para obter possíveis associações. RESULTADOS Os resultados do estudo mostram que menor percentual de áreas verdes está associado significativamente com maior chance de prematuridade. Maior densidade de construção foi associada positivamente com a razão de chance de nascimento prematuro. Não encontramos resultados significativos entre a poluição do ar (MP2,5) e prematuridade. CONCLUSÕES Os resultados deste estudo demostraram que áreas mais verdes em relação às áreas menos verdes são menos associadas a nascimentos prematuros.

Major discrepancy between clinical diagnosis of death and anatomopathological findings in adolescents with chronic diseases during 18-years

Abstract Objectives: To evaluate the inconsistency between clinical diagnosis of death and autopsy findings in adolescents with chronic diseases. Methods: A cross-sectional study including a sample of adolescents' autopsies who died in a pediatric and adolescent tertiary hospital over 18 consecutive years. During this period, there were n = 2912 deaths, and n = 581/2912(20%) occurred in adolescents. Of these, n = 85/581(15%) underwent autopsies and were analyzed. Further results were divided into two groups: Goldman classes I or II (high disagreement between main clinical diagnosis of death and anatomopathological findings, n = 26) and Goldman classes III, IV or V (low or no disagreement between these two parameters, n = 59). Results: Median age at death (13.5 [10‒19] vs. 13 [10‒19] years, p = 0.495) and disease duration (22 [0‒164] vs. 20 [0‒200] months, p = 0.931), and frequencies for males (58% vs. 44%, p = 0.247) were similar between class I/II vs. class III/IV/V. The frequency of pneumonia (73% vs. 48%, p = 0.029), pulmonary abscess (12% vs. 0%, p = 0.026), as well as isolation of yeast (27% vs. 5%, p = 0.008), and virus (15% vs. 2%, p = 0.029) identified in the autopsy, were significantly higher in adolescents with Goldman class I/II compared to those with Goldman class III/IV/V. In contrast, cerebral edema was significantly lower in adolescents of the first group (4% vs. 25%, p = 0.018). Conclusion: This study showed that 30% of the adolescents with chronic diseases had major discrepancies between clinical diagnosis of death and autopsy findings. Pneumonia, pulmonary abscess, as well as isolation of yeast and virus were more frequently identified at autopsy findings in the groups with major discrepancies.

What else in times of COVID-19? The role of minimally invasive autopsy for the differential diagnosis of acute respiratory failure in a case of kala-azar

ABSTRACT Visceral leishmaniasis (VL) is a chronic vector-borne zoonotic disease caused by trypanosomatids, considered endemic in 98 countries, mainly associated with poverty. About 50,000-90,000 cases of VL occur annually worldwide, and Brazil has the second largest number of cases in the world. The clinical picture of VL is fever, hepatosplenomegaly, and pancytopenia, progressing to death in 90% of cases due to secondary infections and multi-organ failure, if left untreated. We describe the case of a 25-year-old female who lived in the metropolitan area of Sao Paulo, who had recently taken touristic trips to several rural areas in Southeastern Brazil and was diagnosed post-mortem. During the hospitalization in a hospital reference for the treatment of COVID-19, the patient developed acute respiratory failure, with chest radiographic changes, and died due to refractory shock. The ultrasound-guided minimally invasive autopsy diagnosed VL (macrophages containing amastigote forms of Leishmania in the spleen, liver and bone marrow), as well as pneumonia and bloodstream infection by gram-negative bacilli.

Salivary glands are a target for SARS-CoV-2: a source for salivacontamination

The ability of the new coronavirus SARS-CoV-2 to spread and contaminate is one of the determinants of the COVID-19 pandemic status. SARS-CoV-2 has been detected in saliva consistently, with similar sensitivity to that observed innasopharyngeal swabs. We conducted ultrasound-guided postmortem biopsies in COVID-19 fatal cases. Samples ofsalivary glands (SGs; parotid, submandibular, and minor) were obtained. We analyzed samples using RT-qPCR, immu-nohistochemistry, electron microscopy, and histopathological analysis to identify SARS-CoV-2 and elucidate qual-itative and quantitative viral proles in salivary glands. The study included 13 female and 11 male patients, with amean age of 53.12 years (range 8­83 years). RT-qPCR for SARS-CoV-2 was positive in 30 SG samples from18 patients (60% of total SG samples and 75% of all cases). Ultrastructural analyses showed spherical 70­100 nm viral particles, consistent in size and shape with the Coronaviridae family, in the ductal lining cell cytoplasm,acinar cells, and ductal lumen of SGs. There was also degeneration of organelles in infected cells and the presence of acluster of nucleocapsids, which suggests viral replication in SG cells. Qualitative histopathological analysis showedmorphologic alterations in the duct lining epithelium characterized by cytoplasmic and nuclear vacuolization, as wellas nuclear pleomorphism. Acinar cells showed degenerative changes of the zymogen granules and enlarged nuclei.Ductal epithelium and serous acinar cells showed intense expression of ACE2 and TMPRSS receptors. An anti-SARS-CoV-2 antibody was positive in 8 (53%) of the 15 tested cases in duct lining epithelial cells and acinar cellsof major SGs. Only two minor salivary glands were positive for SARS-CoV-2 by immunohistochemistry. Salivaryglands are a reservoir for SARS-CoV-2 and provide a pathophysiological background for studies that indicate theuse of saliva as a diagnostic method for COVID-19 and highlight this biological uid's role in spreading the disease.© 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

An autopsy study of the spectrum of severe COVID-19 in children: From SARS to different phenotypes of MIS-C

Background: COVID-19 in children is usually mild or asymptomatic, but severe and fatal paediatric cases have been described. The pathology of COVID-19 in children is not known; the proposed pathogenesis for severe cases includes immune-mediated mechanisms or the direct effect of SARS-CoV-2 on tissues. We describe the autopsy findings in five cases of paediatric COVID-19 and provide mechanistic insight into the mechanisms involved in the pathogenesis of the disease. Methods: Children and adolescents who died with COVID-19 between March 18 and August 15, 2020 were autopsied with a minimally invasive method. Tissue samples from all vital organs were analysed by histology, electron microscopy (EM), reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). Findings: Five patients were included, one male and four female, aged 7 months to 15 years. Two patients had severe diseases before SARS-CoV-2 infection: adrenal carcinoma and Edwards syndrome. Three patients were previously healthy and had multisystem inflammatory syndrome in children (MIS-C) with distinct clinical presentations: myocarditis, colitis, and acute encephalopathy with status epilepticus. Autopsy findings varied amongst patients and included mild to severe COVID-19 pneumonia, pulmonary microthrombosis, cerebral oedema with reactive gliosis, myocarditis, intestinal inflammation, and haemophagocytosis. SARSCoV- 2 was detected in all patients in lungs, heart and kidneys by at least one method (RT-PCR, IHC or EM), and in endothelial cells from heart and brain in two patients with MIS-C (IHC). In addition, we show for the first time the presence of SARS-CoV-2 in the brain tissue of a child with MIS-C with acute encephalopathy, and in the intestinal tissue of a child with acute colitis. Interpretation: SARS-CoV-2 can infect several cell and tissue types in paediatric patients, and the target organ for the...(AU)

Extended minimally invasive autopsy: Technical improvements for the investigation of cardiopulmonary events in COVID-19

OBJECTIVES: Ultrasound-guided minimally invasive autopsies (MIA-US) are an alternative to conventional autopsies and have been used in our institution to investigate the pathophysiology of COVID-19 since the beginning of the pandemic. Owing to the limitations of post-mortem biopsies for evaluating cardiopulmonary events involving large vessels, we continuously improved the technique during this period. Objectives: To demonstrate the usefulness of an extended MIA-US technique (EMIA-US) for the study of thoracic involvement in COVID-19. METHOD: US-guided percutaneous tissue sampling was combined with a small thoracic incision (≤5 cm), allowing for the sampling of larger tissue samples or even the entire organ (lungs and heart). RESULTS: EMIA-US was performed for eight patients who died of COVID-19 in 2021. We demonstrate cardiopulmonary events, mainly thromboembolism and myocardial infarction, that could be evaluated using EMIA-US. CONCLUSIONS: Minimally invasive image-guided post-mortem tissue sampling is a flexible and practical method to conduct post-mortem studies of human diseases, mainly in areas that do not have autopsy facilities or, alternatively, when autopsy is not possible owing to financial constraints, cultural and religious values, or for safety reasons, such as in the case of highly contagious infectious diseases. We present evidence that EMIA-US is feasible and can be used as an alternative to increase the accuracy of MIA-US in detecting cardiopulmonary events involving large vessels, which may not be assessed through post-mortem biopsies.

Miliary tuberculosis: a severe opportunistic infection in juvenile systemic lupus erythematosus patients / Tuberculose miliar: infecção oportunista grave em pacientes com lúpus eritematoso sistêmico juvenil

Abstract Introduction One of the main issues in juvenile systemic lupus erythematosus (JSLE) patients is infection, such as tuberculosis (TB). Of note, SLE patients are susceptible to pulmonary and extrapulmonary TB. However, to our knowledge, this contagious disease was rarely reported in pediatric lupus population, particularly diffuse or miliary TB. Therefore, from January 1983 to December 2011, 5,635 patients were followed-up at our Pediatric Rheumatology Unit and 285 (5%) of them met the American College of Rheumatology classification criteria for SLE. Case reports Four (1.4%) of our JSLE patients had disseminated TB and were described herein. All of them were female gender, received BCG vaccination and did not have a history of TB household contact. The median of current age at TB diagnosis and the period between JSLE and TB diagnosis were 17 years old (range 14-20) and 5.5 years (range 2-7), respectively. All patients developed miliary TB during the course of the disease. The median of SLE Disease Activity Index 2000 (SLEDAI-2K) was 4 (2-16) and the patients were treated with immunosuppressive agents (glucocorticoid, azathioprine and/or intravenous cyclophosphamide). Two of them presented sepsis and TB diagnosis was only established at autopsy, especially with lungs, central nervous system and abdominal involvements. Anti-TB therapy (isoniazid, rifampicin and pyrazinamide) was indicated in the other two TB cases, however they deceased. Discussion Miliary TB is a rare and severe opportunist infection in pediatric lupus population. This study reinforces the importance of routine searches for TB in JSLE patients.

Resumo Introdução Um dos principais problemas no lúpus eritematoso sistêmico juvenil (LESJ) é a infecção, como a tuberculose (TB). É importante observar que pacientes com LES são suscetíveis à tuberculose pulmonar e extrapulmonar. No entanto, de acordo com o que se sabe, essa doença contagiosa é raramente relatada na população pediátrica com lúpus, particularmente a TB difusa ou miliar. De janeiro de 1983 a dezembro de 2011, 5.635 pacientes foram acompanhados na Unidade de Reumatologia Pediátrica; 285 deles (5%) preencheram os critérios de classificação para LES do American College of Rheumatology. Relatos de caso Quatro (1,4%) de nossos pacientes com LESJ tinham tuberculose disseminada e foram descritos neste estudo. Todos eram do sexo feminino, receberam a vacina BCG e não tinham história de contato domiciliar com a TB. A mediana da idade no momento do diagnóstico da TB e o período entre os diagnósticos de LES e tuberculose foram de 17 anos (variação de 14 a 20) e 5,5 anos (variação de dois a sete), respectivamente. Todas as pacientes desenvolveram tuberculose miliar durante o curso da doença. A mediana no SLE Disease Activity Index 2000 (SLEDAI-2K) foi de 4 (2 a 16) e as pacientes foram tratadas com agentes imunossupressores (glicocorticoides, azatioprina e/ou ciclofosfamida intravenosa). Duas delas apresentaram sepse e o diagnóstico de tuberculose só foi determinado na necropsia, com envolvimento especialmente dos pulmões, do sistema nervoso central e do abdome. A terapia antituberculose (isoniazida, rifampicina e pirazinamida) foi indicada nos outros dois casos de TB; porém, as pacientes foram a óbito. Discussão A TB miliar é uma infecção oportunista rara e grave na população pediátrica com lúpus. Este estudo reforça a importância de pesquisas de rotina para TB em pacientes com LESJ.

Metrópoles, cobertura vegetal, áreas verdes e saúde / Metropolises, vegetation, green areas and health

A falta de planejamento no processo de urbanização das grandes metrópoles tem produzido numerosas externalidades negativas, entre elas a supressão de sua cobertura vegetal e de áreas verdes. Inúmeros benefícios têm sido reportados sobre como a presença da vegetação no meio ambiente urbano favorece fatores ambientais, sociais e econômicos, influenciando na saúde da população. O presente trabalho busca apresentar uma série de estudos com enfoque na associação entre áreas verdes e saúde e também uma sucinta reflexão sobre a importância do assunto no município de São Paulo...

The lack of planning in the urbanization process of big cities worldwide has produced numerous negative externalities, including the suppression of vegetation and green spaces. Multiple benefits have been reported on how urban vegetation promotes and influences environmental, social and economic factors, as well as people’s health. This paper presents a series of studies focusing on the association between urban vegetation and human health, as well as a brief reflection on the importance of this issue in the city of São Paulo...

Diagnosis of primary ciliary dyskinesia / Diagnóstico de discinesia ciliar primária

Primary ciliary dyskinesia (PCD) is a genetic disorder of ciliary structure or function. It results in mucus accumulation and bacterial colonization of the respiratory tract which leads to chronic upper and lower airway infections, organ laterality defects, and fertility problems. We review the respiratory signs and symptoms of PCD, as well as the screening tests for and diagnostic investigation of the disease, together with details related to ciliary function, ciliary ultrastructure, and genetic studies. In addition, we describe the difficulties in diagnosing PCD by means of transmission electron microscopy, as well as describing patient follow-up procedures.

Discinesia ciliar primária (DCP) é uma doença genética que compromete a estrutura e/ou a função ciliar, causando retenção de muco e bactérias no trato respiratório e levando a infecções crônicas nas vias aéreas superiores e inferiores, defeitos de lateralidade visceral e problemas de fertilidade. Revisamos os sinais e sintomas respiratórios da DCP, os testes de triagem e a investigação diagnóstica, bem como detalhes relacionados ao estudo da função, ultraestrutura e genética ciliar. Descrevemos também as dificuldades em diagnosticar a DCP por meio de microscopia eletrônica de transmissão, bem como o seguimento dos pacientes.

In vivo assessment of antiretroviral therapy-associated side effects

Antiretroviral therapy has been associated with side effects, either from the drug itself or in conjunction with the effects of human immunodeficiency virus infection. Here, we evaluated the side effects of the protease inhibitor (PI) indinavir in hamsters consuming a normal or high-fat diet. Indinavir treatment increased the hamster death rate and resulted in an increase in triglyceride, cholesterol and glucose serum levels and a reduction in anti-oxLDL auto-antibodies. The treatment led to histopathological alterations of the kidney and the heart. These results suggest that hamsters are an interesting model for the study of the side effects of antiretroviral drugs, such as PIs.

Academic autopsies in Brazil - a national survey / Autópsias acadêmicas no Brasil - um inquérito nacional

Objective: To investigate the number and rate of academic autopsies, general organization, educational and research in Brazilian academic services. Methods: Standardized questionnaires were sent to Brazilian medical schools (n=177) and active pathology residency programs (n=53) from March to June 2009. Data were collected for years 2003 to 2008. Results: Thirty-two academic services in 11 Brazilian states answered the survey. Twenty-one (65.6%) perform less than a hundred autopsies for natural causes and less than fifty pediatric or fetal autopsies/year. Twenty-four (75%) perform less than a hundred adult autopsies/year. Many institutions (46.9%) reported a drop in the number of autopsies in a six-year period. The total autopsy count and autopsy rate in 2008 ranged 1-632 (median = 80), and 0-66% (mean = 10.6%), respectively. A steady decrease in the total count of autopsies in a pool of 19 institutions was observed (p<0.01). Median autopsy rates have fallen from 19.3%, in 2003, to 10.6%, in 2008 (p=0.07). Significant discrepancies at autopsies led to changes in institutional healthcare practice in 37.5% of the services. The low number of autopsies was a limiting factor in undergraduate education for 25% of respondents. A minimum number of autopsies is required to complete the pathology residency program in 34.6% of the services. Conclusion: The total number and the rate of academic autopsies have decreased in Brazil between 2003 and 2008. The number of autopsies and the general organization of academic services must be enhanced to improve medical education, research, and the quality control of patient care. .

Objetivo: Investigar o número e a taxa de autópsias acadêmicas, organização geral, ensino e pesquisa em serviços acadêmicos brasileiros. Métodos: Questionários padronizados enviados para escolas médicas brasileiras (n=177) e programas de residência em patologia ativos (n=53) de março a junho de 2009. Dados coletados referentes ao período de 2003 a 2008. Resultados: Trinta e dois serviços em 11 estados responderam à pesquisa. Vinte e um (65,6%) realizam menos de cem autópsias de causas naturais e menos de cinquenta autópsias fetais ou pediátricas/ano. Vinte e quatro (75%) realizam menos de cem autópsias de adultos/ano. Muitas instituições (46,9%) relataram queda no número de autópsias em seis anos. A contagem total e a taxa de autópsias em 2008 variaram, respectivamente, de 1 a 632 (mediana=80) e de 0 a 66% (média=10,6%). Foi observada uma redução contínua no total de autópsias em um grupo de 19 instituições (p<0,01). A mediana da taxa de autópsias caiu de 19,3%, em 2003, para 10,6%, em 2008 (p=0,07). Discrepâncias significativas observadas em autópsias levaram a mudanças na prática institucional de saúde em 37,5% dos serviços. O baixo número de autópsias foi limitante no ensino de graduação para 25% dos entrevistados. Um número mínimo de autópsias é necessário para completar o programa de residência em patologia em 34,6% dos serviços. Conclusão: O número total e a taxa de autópsias acadêmicas diminuíram no Brasil entre 2003 e 2008. O número de autópsias e organização geral dos serviços acadêmicos deve ser melhorado para fortalecer a educação médica, pesquisa e controle de qualidade prestado ao paciente. .

Asthma as a cause of death / Asma como causa de morte

Mortes causadas por asma são incomuns, mas, mesmo assim, respondem por cerca de 287.000 óbitos anuais mundialmente. Embora as taxas de mortalidade por asma venham diminuindo em diversos países, há grande disparidade na mortalidade por asma no mundo. A maior parte das mortes está relacionada ao manejo clinico subótimo. Fatores frequentemente envolvidos com asma quase fatal e fatal incluem história prévia de crises quase fatais, intubação/ventilação mecânica prévia, hospitalização ou admissão em UTI, falta de adesão ao tratamento, percepção falha de dispneia, distúrbios psicológicos e nível socioeconômico baixo. Na autópsia, os pulmões de pacientes que morreram de asma estão geralmente hiperinflados e os brônquios maiores e menores ocluídos por muco. Os achados histológicos incluem descolamento epitelial, espessamento da lâmina reticularis da membrana basal, glândulas submucosas e músculo liso aumentados e composição alterada da matriz extracelular nas vias aéreas grandes e pequenas. A inflamação brônquica é generalizada, sendo proeminente na camada adventícia das pequenas vias. Os mecanismos que levam à morte na asma não estão claros. O espasmo potente da musculatura lisa e a produção excessivade muco parecem ser os eventos chave que culminam em morte. Uma exacerbação aguda pode ser mortal em pacientes com asma mal controlada e subtratada e que tenham alterações estruturais nas vias aéreas pré-existentes

Respiratory mechanics do not always mirror pulmonary histological changes in emphysema

OBJECTIVE: To verify the accordance of functional and morphometric parameters during the development of emphysema. METHODS: BALB/c mice received a nasal drop of either papain or saline solution and were studied after 1, 3, 15, 28, and 40 days. Functional parameters, such as airway resistance, tissue damping, and tissue elastance, were analyzed. To evaluate the structural changes and possible mechanisms involved in this disease, we measured the mean linear intercept, the volume proportions of elastic and collagen fibers, the number of macrophages, the numbers of cells expressing metalloprotease 12 and 8-isoprostane in lung parenchyma. RESULTS: We only observed decreases in tissue elastance and tissue damping on the 28th day, with a concomitant increase in the mean linear intercept, indicating the presence of emphysema. However, only the mean linear intercept values remained increased until the 40th day. The volume proportion of collagen fibers was increased from the 15th day to the 40th day, whereas the volume proportion of elastic fibers was only increased on the 40th day. The number of macrophages increased beginning on the 1st day. The expression of metalloproteinase 12 was increased from the 3rd day until the 40th day. However, 8-isoprostane expression was only increased on the 1st and 3rd days. CONCLUSIONS: In this study, morphometric parameters were found to be more reliable for detecting the presence of emphysema than the functional parameters measured by respiratory mechanics. Further investigations are necessary to understand how the extracellular matrix remodeling observed in the lung parenchyma could be involved in this process.

Urban, traffic- related particles and lung tumors in urethane treated mice

OBJECTIVE: The present study was designed to evaluate the effects of urban, traffic-related, fine particulate matter (PM2.5) on mice lung tumorigenesis under controlled exposure conditions. METHODS: Four groups of female Swiss mice were treated with intraperitonial injections of urethane and saline solution. Urethane was used to start the carcinogenesis process. The animals were housed in two chambers receiving filtered and polluted air. In the polluted air chamber, pollutant levels were low. After two months of exposure, the animals were euthanized and lung tumoral nodules were counted. RESULTS: Saline-treated animals showed no nodules. Urethane-treated animals showed 2.0+2.0 and 4.0+3.0 nodules respectively, in the filtered and non-filtered chambers (p = 0.02), thus showing experimental evidence of increased carcinogenic-induced lung cancer with increasing PM2.5 exposure. CONCLUSION: Our data support the concept that low levels of PM2.5 may increase the risk of developing lung tumors.

Hantavirus asociado a sepsis estafilocócica: caso clínico / Hantavirus infection associated to a staphylococcal sepsis: report of one case

We report a previously healthy 36-year-old mole who developed a pulmonary syndrome caused by Hantavirus infection. He was admitted to an intensive care unit in shock and respiratory failure and died four hours after admission. Blood cultures were positive for Staphylococcus aureus. This patient could be an index case that shows, for the first time, an association of Hantavirus Pulmonary Syndrome with Staphylococcus aureus infection similar to what happens with other viruses.

Effects of different peep levels on mesenteric leukocyte-endothelial interactions in rats during mechanical ventilation

INTRODUCTION: Mechanical ventilation with positive end expiratory pressure (PEEP) improves oxygenation and treats acute pulmonary failure. However, increased intrathoracic pressure may cause regional blood flow alterations that may contribute to mesenteric ischemia and gastrointestinal failure. We investigated the effects of different PEEP levels on mesenteric leukocyte-endothelial interactions. METHODS: Forty-four male Wistar rats were initially anesthetized (Pentobarbital I.P. 50mg/kg) and randomly assigned to one of the following groups: 1) NAIVE (only anesthesia; n=9), 2) PEEP 0 (PEEP of 0 cmH2O, n=13), 3) PEEP 5 (PEEP of 5 cmH2O, n=12), and 4) PEEP 10 (PEEP of 10 cmH2O, n=13). Positive end expiratory pressure groups were tracheostomized and mechanically ventilated with a tidal volume of 10 mL/kg, respiratory rate of 70 rpm, and inspired oxygen fraction of 1. Animals were maintained under isoflurane anesthesia. After two hours, laparotomy was performed, and leukocyte-endothelial interactions were evaluated by intravital microscopy. RESULTS: No significant changes were observed in mean arterial blood pressure among groups during the study. Tracheal peak pressure was smaller in PEEP 5 compared with PEEP 0 and PEEP 10 groups (11, 15, and 16 cmH2O, respectively; p<0.05). After two hours of MV, there were no differences among NAIVE, PEEP 0 and PEEP 5 groups in the number of rollers (118±9,127±14 and 147±26 cells/10minutes, respectively), adherent leukocytes (3±1,3±1 and 4±2 cells/100µm venule length, respectively), and migrated leukocytes (2±1,2±1 and 2±1 cells/5,000µm², respectively) at the mesentery. However, the PEEP 10 group exhibited an increase in the number of rolling, adherent and migrated leukocytes (188±15 cells / 10 min, 8±1 cells / 100 µm and 12±1 cells / 5,000 µm², respectively; p<0.05). CONCLUSIONS: High intrathoracic pressure was harmful to mesenteric microcirculation in the experimental model of rats with normal lungs and ...