Background: The adverse effects of mechanical ventilation (MV) are a major health concern associated with poor outcomes and economic burden. Some populations, such as those requiring more than one attempt at the gradual removal of MV (weaning), are at risk for longer duration of MV and associated complications. Traumatically injured patients have a higher prevalence of positive illicit drug toxicology then the general population. The traumatically injured, positive for illicit drugs who requires MV, may experience the sequelae of withdrawal syndrome and violate the thresholds that allow weaning, leading to longer durations MV. Methods: A retrospective descriptive analysis of a convenience sample of 52 adult trauma patients from SJHMC admitted between January 1 to December 31, 2014 who presented positive for illicit drugs and required mechanical ventilation. This sample was analyzed to: 1) describe the characteristics of this specific sample, 2) determine the prevalence of a difficult-to-wean subsample, 3) describe the characteristics of this sample during weaning attempts, and 4) determine if the existing weaning protocol necessitates amending. Results: Samples ability to wean; 78.8% (n=41) simple weaning; 15.38% (n=8) difficult weaning; and 5.77% (n=3) prolonged. Zero cases of adverse effects of MV or withdrawal syndrome detected. There was no correlation between stimulant and/or depressant and ability to wean (p=0.662). There was no relationship between injury severity score (ISS) and weaning group (p=0.762). Characteristics identified included; male to female ratio 4:1 and majority with ISS score>24. Variables within weaning protocol were missing 25-84% of data. Conclusion: The ability to wean MV in this sample is similar to what is reported in the general population, suggesting that they are not at risk for difficult weaning or prolonged MV. This sample’s majority was comprised of more traumatically complex, young males than found in the general trauma population. Investigators were unable to analyze or amend the current protocol because of the large amounts of missing data indicating possible gaps in adherence and/or documentation. To our knowledge, this is the first project that describes ability to wean in the traumatically injured positive for illicit drug.

Mechanical ventilation has been a major therapy used by physicians in support of surgery as well as for treating patients with reduced lung function. Despite its many positive outcomes and ability to maintain life, in many cases, it has also led to increased injury of the lungs, further exacerbating the diseased state. Numerous studies have investigated the effects of long term ventilation with respect to lungs, however, the connection between the global deformation of the whole organ and the strains reaching the alveolar walls remains unclear. The walls of lung alveoli also called the alveolar septum are characterized as a multilayer heterogeneous biological tissue. In cases where damage to this parenchymal structure insist, alveolar overdistension occurs. Therefore, damage is most profound at the alveolar level and the deformation as a result of such mechanical forces must be investigated thoroughly. This study investigates a three-dimensional lung alveolar model from generations 22 (alveolar ducts) through 24 (alveoli sacs) in order to estimate the strain/stress levels under mechanical ventilation conditions. Additionally, a multilayer alveolar tissue model was generated to investigate localized damage at the alveolar wall. Using ANSYS, a commercial finite element software package, a fluid-structure interaction analysis (FSI) was performed on both models. Various cases were simulated that included a normal healthy lung, normal lung with structural changes to model disease and normal lung with mechanical property changes to model aging. In the alveolar tissue analysis, strains obtained from the aged lung alveolar analysis were applied as a boundary condition and used to obtain the mechanical forces exerted as a result. This work seeks to give both a qualitative and quantitative description of the stress/strain fields exerted at the alveolar region of the lungs. Regions of stress/strain concentration will be identified in order to gain perspective on where excess damage may occur. Such damage can lead to overdistension and possible collapse of a single alveolus. Furthermore, such regions of intensified stress/strain are translated to the cellular level and offset a signaling cascade. Hence, this work will provide distributions of mechanical forces across alveolar and tissue models as well as significant quantifications of damaging stresses and strains.

Mechanical ventilation (MV) is a system that partially or fully assists patients whose respiratory system fails to achieve a gas exchange function. However, MV can cause a ventilator-associated lung injury (VALI) or even contribute to a multiple organ dysfunction syndrome (MODS) in acute respiratory distress syndrome (ARDS) patients. Despite advances in today technologies, mortality rates for ARDS patient are still high. A better understanding of the interactions between airflow from mechanical ventilator and the airway could provide useful information used to develop a better strategy to ventilate patients. The mechanisms, which mechanical ventilation induces airway inflammation, are complex processes and cover a wide range of spatial scales. The multiscale model of the airway have been developed combining the computational models at organ, tissue, and cellular levels. A model at the organ level was used to study behaviors of the airway during mechanical ventilation. Strain distributions in each layer of the airway were investigated using a model at the tissue level. The cellular inflammatory responses during mechanical ventilation were investigated through the cellular automata (CA) model incorporating all biophysical processes during inflammatory responses. The multiscale modeling framework started by obtaining airway displacements from the organ-level model. They were then transferred to the tissue-level model for determining the strain distributions in each airway layer. The strain levels in each layer were then transferred to the cellular-level model for inflammatory responses due to strain levels. The ratio of the number of damage cells to healthy cells was obtained through the cellular-level model. This ratio, in turn, modulated changes in the Young’s modulus of elasticity at the tissue and organ levels. The simulation results showed that high tidal volume (1400 cc) during mechanical ventilation can cause tissue injury due to high concentration of activated immune cells and low tidal volume during mechanical ventilation (700 cc) can prevent tissue injury during mechanical ventilation and can mitigate tissue injury from the high tidal volume ventilation. The multiscale model developed in this research could provide useful information about how mechanical ventilation contributes to airway inflammation so that a better strategy to ventilate patients can be developed.

A fairly large portion of patients receiving surgical or intensive care will need mechanical ventilation at some point. The potential ventilator-induced lung injury (VILI) is thus of interest. One of the main causal factors in VILI is the cyclic energy shifts, i.e. tidal volumes, in the lung during mechanical ventilation. The problem can be approached in two ways. Firstly, one can utilize apneic oxygenation and thus not cause any tidal injuries at all. Secondly, and more traditionally, one can simply lower the tidal volumes and respiratory rates used. The following describes a series of animal experiments exploring these options. In the first two papers, I explored and improved upon the methodology of apneic oxygenation. There is a generally held belief that it is only possible to perform apneic oxygenation by prior denitrogenation and by using 100% oxygen during the apnea. As 100% oxygen is toxic, this has prevented apneic oxygenation from more widespread use. The first paper proves that it is indeed possible to perform apneic oxygenation with less than 100% oxygen. I also calculated the alveolar nitrogen concentration which would conversely give the alveolar oxygen concentration. The second paper addresses the second large limitation of apneic oxygenation, i.e. hypercapnia. Using a high dose infusion of tris(hydroxymethyl)aminomethane (THAM) buffer, a pH > 7.2 could be maintained during apneic oxygenation for more than 4.5 hours. In the last two papers, THAM’s properties as a proton acceptor are explored during respiratory acidosis caused by very low volume ventilation. In paper III, I found that THAM does not, in the long term, affect pH in respiratory acidosis after stopping the THAM infusion. It does, however, lower PVR, even though the PaCO2 of THAM-treated animals had rebounded to levels higher than that of the controls. In the last experiment, I used volumetric capnography to confirm our hypothesis that carbon dioxide elimination through the lungs was lower during the THAM infusion. Again, the PaCO2 rebounded after the THAM infusion had stopped and I concluded that renal elimination of protonated THAM was not sufficient.

Os prematuros frequentemente necessitam de ajuda para iniciar a respiração, pois líquido amniótico residual e deficiência de surfactante podem impedir o estabelecimento da CRF. A necessidade de intubação e do uso de ventilação com pressão positiva está relacionada à chamada lesão pulmonar induzida pela ventilação. A intubação endotraqueal é uma ocorrência comum na unidade de terapia intensiva neonatal. A extubação acidental (EA) ou o deslocamento acidental do tubo endotraqueal é um evento inseguro e adverso. Um estudo norteamericano relatou que a EA é o quarto evento adverso mais comum na UTIN. Isso coloca o neonato em risco de morbidade significativa. As hipóteses iniciais para este estudo considerando as características locais do serviço, são que a taxa de extubação acidental deste serviço seria superior ou igual à encontrada na literatura e que as consequências da perda de volume pulmonar causada pela EA geraria uma necessidade de aumento de parâmetros ventilatórios, expondo esses pacientes a um maior risco de desenvolvimento de lesão pulmonar induzida pela ventilação mecânica. O presente estudo teve como objetivo estabelecer a densidade de extubação acidental para cada 100 pacientes-dia e os fatores de risco e as consequências associadas à extubação acidental em uma unidade de terapia intensiva neonatal. A coleta de dados ocorreu o período de fevereiro a dezembro de 2016. Foram elegíveis todos os recém-nascidos intubados com necessidade de ventilação mecânica invasiva e selecionados, para o estudo, os recém-nascidos em assistência ventilatória há pelo menos 12 horas. Nos 10 meses e meio de estudo (318 dias), observou-se uma média de 9,04 pacientes intubados por dia, sendo analisados 2875 pacientes-dia com via aérea artificial. Nos 318 dias de observação ocorreram 45 extubações acidentais, com taxa de EA de 1,57 para cada 100 dias intubação. Os recém-nascidos tinham em média 26,55±35,35 dias de vida na EA, mínimo de 3 dias e máximo de 182 dias. Na amostra estudada, todos os recém-nascidos necessitaram de reintubação após o evento de EA. As características clínicas foram semelhantes nos dois grupos. Assim, os dados apresentados evidenciam que os grupos estudados se apresentaram bastante homogêneos. Foram associados como fatores de risco para EA a utilização de material inadequado para a fixação da cânula orotraqueal (esparadrapo), a carência de pessoal para os cuidados diários (mais de 2 pacientes por funcionário), e mostrou-se ainda a grande importância dos alarmes de saturação sanguínea já que foram responsáveis por 60% diagnóstico da ocorrência do evento. A EA acarretou piora das condições respiratórias com necessidade de aumento do suporte ventilatório ( maior necessidade de oxigênio, pressão inspiratória e PEEP) e recuperação lenta às condições pré- acidente em média 5,7 dias. Concomitante com o aumento da necessidade de suporte respiratório houve maior ocorrência de hiperóxia após o acidente, levantando o temor de efeitos deletérios sinérgicos sobre o pulmão já anteriormente debilitado dos prematuros. É necessária a conscientização da administração e das equipes de profissionais da saúde das UTINs unidades, da enorme importância de se prevenir e diagnosticar precocemente a extubação acidental. / Premature infants often require help in initiating breathing, since residual amniotic fluid and surfactant deficiency may prevent the establishment of functional residual capacity. The need for intubation and the use of positive pressure ventilation is related with ventilator-induced lung injury. Endotracheal intubation is a common occurrence in the neonatal intensive care unit. Accidental extubation (AE) or accidental displacement of the endotracheal tube is an unsafe and adverse event. An American study has reported that EA is the fourth most common adverse event in the NICU. This puts the neonate at risk of significant morbidity. The initial hypotheses for this study considering the local characteristics of the service are that the rate of accidental extubation of this service would be higher than or equal to that found in the literature and that the consequences of loss of lung volume caused by the AE would generate a need for increased ventilatory parameters , exposing these patients to a higher risk of lung injury induced by mechanical ventilation. The present study aimed to establish the accidental extubation density for each 100 patients per day and the risk factors and consequences associated with accidental extubation in a neonatal intensive care unit. Data were collected from February to December 2016. All intubated newborns requiring invasive mechanical ventilation were eligible and the newborns in ventilatory assistance were selected for at least 12 hours for the study. In the 10 and a half months of study (318 days), an average of 9.04 intubated patients per day was observed, with 2875 day-patients with artificial airway being analyzed. In the 318 days of observation, there were 45 accidental extubations, with an AE rate of 1.57 for every 100 days of intubation. The newborns had a mean of 26.55±35.35 days of life in AE, a minimum of 3 days and a maximum of 182 days. In the studied sample, all newborns required reintubation after the AE event. As constitutional aspects were seem in the two groups. Thus, the presented data evidences that the studied groups are quite homogeneous. Risk factors for the use of materials for the fixation of the orotracheal waist (tape), a shortage of personnel for the longest care, and the greater importance of the alarms were included. of blood saturation that was responsible for 60% of the occurrence of the event. AE is one of the largest public health service companies in the world, inspiratory pressure and PEEP, and average recurring expenses an average of 5.7 days. Concomitant with the increased risk of respiratory accident for most cases following the occurrence of an accident, raising the risk of fire and synergy over the previous exercise already weakened of the premature. Immigration is an awareness of NICU management and staff of health professionals, which is important in preventing and early diagnosis of accidental extubation.

A monitorização após o parto é necessária a manutenção da vida nos bezerros clonados. É imperativo que os protocolos e procedimentos, bem como a avaliação clínica dos sistemas cardiovascular e respiratório sejam aprimorados para a sobrevida dos clones. As avaliações que permitam averiguar a capacidade de oxigenação dos pulmões são de crucial importância na assistência ao neonato, sendo que para essa finalidade tem-se recomendado a utilização da hemogasometria. O estudo foi dividido em quatro capítulos, sendo o 1 º Capítulo: Comparação das diferenças da adaptação neonatal de bezerros da raça Nelore(n=10) e de bezerros da raça Holandesa(n=10) nas trocas gasosas e nos parâmetros hemodinâmicos obtidos por meio do cateter de Swan-Ganz, o 2 º Capítulo: Avaliação da hemodinâmica e da hemogasometria de bezerros clonados(n=3), e o 3º Capítulo: Relato da utilização da ventilação mecânica não invasiva - modo CPAP- no tratamento de hipóxia neonatal em 10 bezerros e o 4º Capítulo: Avaliação hemodinâmica e hemogasométrica de bezerros neonatos com distúrbios respiratórios submetidos a ventilação mecânica não invasiva com mascara facial modo ventilatório CPAP (n=12). O objetivo deste trabalho será padronizar a utilização de ventiladores em bezerros neonatos dando o suporte respiratório necessário, avaliando hemodinâmicas da pressão da artéria pulmonar, freqüência cardíaca, débito cardíaco por meio da utilização do cateter de Swan-Ganz, a hemogasometria de sangue arterial para avaliação dos distúrbios respiratórios e obtenção dos valores de normalidade dos parâmetros, além de conhecer a adaptação neonatal das raças Nelore e holandesa. Foram determinadas média pressão artéria pulmonar, pressão artéria pulmonar ocluída, pressão ventrículo direito, pressão átrio direito, temperatura, pH, pCO2, pO2, HCO3, BE, SO2. Os animais foram ventilados modo CPAP- ventilação mecânica não invasiva com mascara facial com pressão positiva no final da expiração(PEEP). / Monitoring after calving is required for the maintenance of life in cloned calves. It is imperative that protocols and procedures, as well as the clinical assessment of cardiovascular and respiratory systems are improved for the survival of clones. Evaluations in order to verify the oxygenation capacity of lungs are crucial in neonatal care, and for this purpose has recommended the use of blood gas analysis. The study was divided into four chapters, the 1st chapter: Comparison of differences in neonatal adaptation of Nellore calves (n = 10) and Holstein calves (n = 10) in gas exchange and hemodynamic parameters obtained by through the Swan-Ganz, the 2nd Chapter: hemodynamic evaluation and blood gas analysis of cloned calves (n = 3), and the 3rd Chapter: Reporting the use of noninvasive mechanical ventilation - CPAP- in the treatment of neonatal hypoxic 10 calves and Chapter 4: hemodynamic evaluation and hemogasometric of newborn calves with respiratory disorders underwent noninvasive ventilation with face mask ventilation mode CPAP (n = 12). The purpose of this study is to standardize the use of mechanical ventilators in newborn calves giving the required respiratory support, evaluating hemodynamic pulmonary artery pressure, heart rate, cardiac output by using of the Swan-Ganz catheter, arterial blood gas analysis to evaluation of respiratory disorders and obtaining the parameters normal values, and know the neonatal adaptation of Nellore and Hostein Frisian races. They were determined means of pulmonary artery pressure, pulmonary artery wedge pressure, right ventricular pressure, right atrial pressure, temperature, pH, pCO2, pO2, HCO 3, BE, SO 2. The animals were ventilated CPAP- noninvasive ventilation mode with face mask with positive pressure at the end of expiration (PEEP)

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

O desmame é a transição da ventilação mecânica para a espontânea ao final da assistência ventilatória artificial. Não existem estudos específicos sobre esta fase de transição na espécie equina porém, os elevados valores na tensão de dióxido de carbono arterial (PaCO2) ao desmame e os baixos valores na tensão de oxigênio arterial (PaO2) na recuperação pós-anestésica (RPA) refletem a necessidade do estudo de modalidades mais seguras de desmame. Sendo assim, este estudo objetivou comparar dois diferentes protocolos de desmame da ventilação mecânica em equinos hígidos. Para tanto, foram utilizados 20 equinos, de 5±2 anos de idade e pesando 456±90 kg, submetidos a procedimento cirúrgico em decúbito dorsal. Os animais foram divididos aleatoriamente em 2 grupos de acordo com o protocolo de desmame, sendo considerado Grupo Controle os animais que foram submetidos a diminuição gradual da frequência respiratória (FR) isoladamente e Grupo PSV os animais que foram submetidos à redução da FR associada à administração de pressão de suporte ventilatório (PSV). Avaliou-se os parâmetros cardiovasculares, de ventilação, de oxigenação e metabólicos durante o desmame, a desconexão da ventilação mecânica e a RPA. Ao final do desmame, o Vexp (12,49±1,93 L) e o VT (28,10±6,17 mL/kg) do Grupo PSV foram superiores aos do Grupo Controle (Vexp de 7,66±2,66 L e VT de 16,88±4,30 mL/kg). Durante o desmame, a PaCO2 aumentou 29% (de 44±3 mmHg para 57±6 mmHg) e houve diminuição de 28% da relação PaO2/FiO2 (de 391±68 mmHg para 280±28) e de 9% da SaO2 (de 100±1% para 91±3%) apenas no Grupo Controle. Na RPA houve hipoxemia transitória no Grupo Controle após 15 (PaO2 de 48±5 mmHg) e 35 minutos (PaO2 de 57±7 mmHg) da desconexão do ventilador, e no Grupo PSV obteve-ve relação PaO2/FiO2 e SaO2 superior à do Grupo Controle durante a RPA. Concluiu-se que o uso da PSV no desmame foi capaz de manter os parâmetros ventilatórios e de oxigenação adequados durante todos os momentos de avaliação, e o desmame por redução gradativa da FR não impediu a ocorrência de hipercapnia transitória ao final do desmame e hipoxemia transitória na RPA. Considerando-se a higidez dos animais, estas alterações foram revertidas sem intervenção clínica, mas devem ser consideradas em animais debilitados. / Weaning from mechanical ventilation is the transition from mechanical to spontaneous ventilation at the end of the ventilatory support. There are no specific studies about this transition phase in horses. However, high tension of carbon dioxide pressure (PaCO2) at weaning and low values of arterial oxygen tension (PaO2) during recovery from anaesthesia suggest the need to study safer modalities of weaning. The scope of this study was to compare two weaning protocols from mechanical ventilation in healthy horses. With this purpose we studied 20 horses with a mean age of 5±2 years and a mean weight of 456±90 kg, scheduled to surgery in dorsal recumbency. Animals were randomly assigned one of the 2 weaning protocols, considering from Control Group those animals submitted to gradual decrease in respiratory rate (RR) set alone and from PSV Group those animals submitted to gradual decrease in RR associated with pressure support ventilation (PSV) administration. We evaluated cardiovascular, ventilatory, oxygenation and metabolic parameters during weaning, ventilator disconnection and recovery from anaesthesia. At the end of weaning, Vexp (12,49±1,93 L) and VT (28,10±6,17 mL/kg) of PSV Group were superior to the Control Group (Vexp of 7.66±2.66 L and VT of 16.88±4.30 mL/kg). During weaning PaCO2 increased by 29% (44±3 mmHg to 57±6 mmHg) and there was increasing PaO2/FiO2 ratio by 28% (391±68 mmHg to 280±28) and SaO2 by 9% (100±1% to 91±3%) only in Control Group. In the recovery phase there was transient hypoxemia in Control Group after 15 (PaO2 of 48±5 mmHg) and 35 minutes (PaO2 of 57±7 mmHg) of ventilator disconnection, and PaO2/FiO2 ratio and SaO2 in PSV Group were superior to the Control Group in the recovery phase. We conclude that the use of PSV in the weaning from mechanical ventilation phase was capable to remain ventilatory and oxygenation parameters appropriate in all evaluations, and weaning only by gradual decrease of RR did not prevent the occurrence of transient hypercapnia at the end of weaning and transient hypoxemia in the recovery from anaesthesia. Considering the healthiness of the animals, these changes were reversed without clinical intervention, but should be considered important recovery events in critical horses.

Objectives: Negative energy balance can impair regeneration of the respiratory epithelium and limit the functionality of respiratory muscles, which can prolong mechanical ventilation. The present study sought to quantify and identify deviation in energy requirements of patients with septic shock during and upon liberation from mechanical ventilation. Methods: Patients admitted into intensive care with initial diagnosis of septic shock and mechanical ventilation-dependent were recruited. Their metabolic requirements before and after liberation from mechanical ventilation were measured by indirect calorimetry. Paired t-test was used to examine the variance between the two modes of breathing and Spearman rho correlation coefficient to examine relationship of selected indicators. Results: Thirty-five patients, 20 males and 15 females mean age 69 ±10 years, body height of 1.58 ±0.08 meters, and ideal body weight 59.01 ±7.63 kg were recruited. Median APACHEII score was 22, length of stay in the intensive care was 45 ±65 days and duration on mechanical ventilation was 24 ±25 days. Measured energy expenditure during ventilation was 2090 ±489 kcal∙d-1 upon liberation from ventilation was 1910 ±579 kcal∙d-1, and actual caloric intake was 1148 ±495 kcal∙d-1. Paired-t test showed that measured energy expenditure (p=0.02), actual calories provision and energy expenditure with (p=0.00) and without (p=0.00) ventilator support were all significantly different. Mean carbohydrate oxidation was 0.17 ±0.09 g·min-1 when patients were on mechanical ventilation compared to 0.14 ±0.08 g·min-1 upon liberalization from it, however, the results were not statistically significant. Furthermore, mean lipid oxidation was 0.08 ±0.05 g·min-1 during mechanical ventilation and 0.09±0.07 g·min-1 upon liberalization from it and the mean difference was not statistically significant. Spearman correlation coefficient showed a positive relationship between actual calorie provision and duration of stay in intensive care (r=0.41 and p=0.01) and duration on mechanical ventilation (r=0.55 and p=0.00). Oxygen consumption (r=0.49 and p=0.00) and carbon dioxide production (r=0.4 and p=0.02) were moderately strong and positive during and upon liberation from mechanical ventilation. Correlation between lipid oxidation and oxygen consumption during ventilation (r=0.74, p=0.00) and after ventilation (r=0.82, p=0.00) as well as lipid oxidation and carbon dioxide production during ventilation (r=0.37, p=0.03) and liberation from ventilator (r=0.91, p=0.00) were significantly correlated with each other in grams per minute only. Conclusions: This is a pioneering study to examine energy expenditure and substrate utilization and oxidation within a single cohort of patients. The lower measured energy expenditure upon liberation from mechanical ventilation among critically ill patients could result from positive pressure support from ventilation, the repeated cycle of “rest” and “work” during weaning from ventilators and the asynchronization between self-initiated breathing effort and the ventilatory support. The positive relationship in duration on mechanical ventilation and length of stay with calorie consumption could be longer stay led to more time for progression to reach nutrition targets. . Any discrepancy in energy expenditure and substrate utilization with and without ventilatory support should be monitored. Future studies are important to examine whether matching energy expenditure with energy intake could promote positive clinical outcomes.