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La tomografía por impedancia eléctrica (TIE) es una modalidad de monitorización funcional respiratoria por imagen, no invasiva y libre de radiación, que permite visualizar en tiempo real la ventilación pulmonar regional y global en pacientes adultos y pediátricos conectados a Ventilación Mecánica (VM). OBJETIVO: Se describe la utilidad de la TIE en dos pacientes críticos pediátricos, en quienes no fue factible realizar medición de mecánica pulmonar, como herramienta para el ajuste de parámetros ventilatorios. CASOS CLÍNICOS: Se presentan dos pacientes pediátricos de 27 y 11 meses con condiciones clínicas diferentes, conectados a VM, en quienes se utilizó la TIE como método de monitoreo de la distribución pulmonar y titulación de la presión positiva al final de la espiración (PEEP) óptima, con el objetivo de obtener una ventilación pulmonar más homogénea. Se presentan mediciones funcionales con diferentes niveles de PEEP y valores de distribución en las distintas regiones de interés (ROI), además de un flujograma de situaciones en las que la TIE podría resultar útil para el ajuste ventilatorio. CONCLUSIÓN: La información funcional proporcionada por la TIE, permitió monitorizar de forma dinámica la VM y optimizar los parámetros ventilatorios, facilitando la implementación de estrategias de protección pulmonar en ambos pacientes, imposibilitados de realizar una medición estática de la mecánica respiratoria.

The Electrical Impedance Tomography (EIT) is a non-invasive and radiation-free respiratory functional imaging monitoring modality that allows real-time visualization of regional and global lung ventilation in adult and pediatric patients connected to mechanical ventilation (MV). OBJECTIVE: This paper describes the utility of EIT in two critical pediatric patients for whom measuring pulmonary mechanics was not feasible. EIT is used as a tool for adjusting ventilatory parameters. CLINICAL CASES: Two pediatric patients aged 27 and 11 months, with different clinical conditions, connected to MV are presented. EIT was used to monitor lung distribution and titrate the optimal Positive End-Expiratory Pressure (PEEP), to achieve more homogeneous lung ventilation. Functional measurements are presented with different PEEP levels and distribution values in different regions of interest (ROI), along with a flowchart illustrating situations where EIT could be useful for ventilatory adjustment. CONCLUSION: The functional information provided by EIT, allowed dynamic monitoring of MV, optimizing ventilatory parameters and facilitating the implementation of lung protective strategies in both patients, unable to undergo static respiratory mechanics measurements.

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BACKGROUND: PEEP is a cornerstone treatment for children with pediatric ARDS. Unfortunately, its titration is often performed solely by evaluating oxygen saturation, which can lead to inadequate PEEP level settings and consequent adverse effects. This study aimed to assess the impact of increasing PEEP on hemodynamics, respiratory system mechanics, and oxygenation in children with ARDS. METHODS: Children receiving mechanical ventilation and on pressure-controlled volume-guaranteed mode were prospectively assessed for inclusion. PEEP was sequentially changed to 5, 12, 10, 8 cm H2O, and again to 5 cm H2O. After 10 min at each PEEP level, hemodynamic, ventilatory, and oxygenation variables were collected. RESULTS: A total of 31 subjects were included, with median age and weight of 6 months and 6.3 kg, respectively. The main reasons for pediatric ICU admission were respiratory failure caused by acute viral bronchiolitis (45%) and community-acquired pneumonia (32%). Most subjects had mild or moderate ARDS (45% and 42%, respectively), with a median (interquartile range) oxygenation index of 8.4 (5.8-12.7). Oxygen saturation improved significantly when PEEP was increased. However, although no significant changes in blood pressure were observed, the median cardiac index at PEEP of 12 cm H2O was significantly lower than that observed at any other PEEP level (P = .001). Fourteen participants (45%) experienced a reduction in cardiac index of > 10% when PEEP was increased to 12 cm H2O. Also, the estimated oxygen delivery was significantly lower, at 12 cm H2O PEEP. Finally, respiratory system compliance significantly reduced when PEEP was increased. At a PEEP of 12 cm H2O, static compliance had a median reduction of 25% in relation to the initial assessment (PEEP of 5 cm H2O). CONCLUSIONS: Although it may improve arterial oxygen saturation, inappropriately high PEEP levels may reduce cardiac output, oxygen delivery, and respiratory system compliance in pediatric subjects with ARDS with low potential for lung recruitability.

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Abstract Background: Positive end-expiratory pressure (PEEP) can overcome respiratory changes that occur during pneumoperitoneum application in laparoscopic procedures, but it can also increase intracranial pressure. We investigated PEEP vs. no PEEP application on ultrasound measurement of optic nerve sheath diameter (indirect measure of increased intracranial pressure) in laparoscopic cholecystectomy. Methods: Eighty ASA I-II patients aged between 18 and 60 years scheduled for elective laparoscopic cholecystectomy were included. The study was registered in the Australian New Zealand Clinical Trials (ACTRN12618000771257). Patients were randomly divided into either Group C (control, PEEP not applied), or Group P (PEEP applied at 10 cmH20). Optic nerve sheath diameter, hemodynamic, and respiratory parameters were recorded at six different time points. Ocular ultrasonography was used to measure optic nerve sheath diameter. Results: Peak pressure (PPeak) values were significantly higher in Group P after application of PEEP (p = 0.012). Mean respiratory rate was higher in Group C at all time points after application of pneumoperitoneum (p < 0.05). The mean values of optic nerve sheath diameters measured at all time points were similar between the groups (p > 0.05). The pulmonary dynamic compliance value was significantly higher in group P as long as PEEP was applied (p = 0.001). Conclusions: During laparoscopic cholecystectomy, application of 10 cmH2O PEEP did not induce a significant change in optic nerve sheath diameter (indirect indicator of intracranial pressure) compared to no PEEP application. It would appear that PEEP can be used safely to correct

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Introduction: Understanding the epidemiological profile and risk factors associated with invasive mechanical ventilation (IMV) is essential to manage the patients better and to improve health services. Therefore, our objective was to describe the epidemiological profile of adult patients in intensive care that required IMV in-hospital treatment. Also, to evaluate the risks associated with death and the influence of positive end-expiratory pressure (PEEP) and arterial oxygen pressure (PaO2) at admission in the clinical outcome. Methods: We conducted an epidemiological study analyzing medical records of inpatients who received IMV from January 2016 to December 2019 prior to the Coronavirus Disease (COVID)-19 pandemic in Brazil. We considered the following characteristics in the statistical analysis: demographic data, diagnostic hypothesis, hospitalization data, and PEEP and PaO2 during IMV. We associated the patients' features with the risk of death using a multivariate binary logistic regression analysis. We adopted an alpha error of 0.05. Results: We analyzed 1,443 medical records; out of those, 570 (39.5%) recorded the patients' deaths. The binary logistic regression was significant in predicting the patients' risk of death [X2(9) = 288.335; p < 0.001]. Among predictors, the most significant in relation to death risk were: age [elderly ≥65 years old; OR = 2.226 (95%CI = 1.728-2.867)]; male sex (OR = 0.754; 95%CI = 0.593-0.959); sepsis diagnosis (OR = 1.961; 95%CI = 1.481-2.595); need for elective surgery (OR = 0.469; 95%CI = 0.362-0.608); the presence of cerebrovascular accident (OR = 2.304; 95%CI = 1.502-3.534); time of hospital care (OR = 0.946; 95%CI = 0.935-0.956); hypoxemia at admission (OR = 1.635; 95%CI = 1.024-2.611), and PEEP >8 cmH2O at admission (OR = 2.153; 95%CI = 1.426-3.250). Conclusion: The death rate of the studied intensive care unit was equivalent to that of other similar units. Regarding risk predictors, several demographic and clinical characteristics were associated with enhanced mortality in intensive care unit patients under mechanical ventilation, such as diabetes mellitus, systemic arterial hypertension, and older age. The PEEP >8 cmH2O at admission was also associated with increased mortality since this value is a marker of initially severe hypoxia.

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BACKGROUND: The profile of changes in airway driving pressure (dPaw) induced by positive-end expiratory pressure (PEEP) might aid for individualized protective ventilation. Our aim was to describe the dPaw versus PEEP curves behavior in ARDS from COVID-19 patients. METHODS: Patients admitted in three hospitals were ventilated with fraction of inspired oxygen (FiO2) and PEEP initially adjusted by oxygenation-based table. Thereafter, PEEP was reduced from 20 until 6 cmH2O while dPaw was stepwise recorded and the lowest PEEP that minimized dPaw (PEEPmin_dPaw) was assessed. Each dPaw vs PEEP curve was classified as J-shaped, inverted-J-shaped, or U-shaped according to the difference between the minimum dPaw and the dPaw at the lowest and highest PEEP. In one hospital, hyperdistention and collapse at each PEEP were assessed by electrical impedance tomography (EIT). RESULTS: 184 patients (41 including EIT) were studied. 126 patients (68%) exhibited a J-shaped dPaw vs PEEP profile (PEEPmin_dPaw of 7.5 ± 1.9 cmH2O). 40 patients (22%) presented a U (PEEPmin_dPaw of 12.2 ± 2.6 cmH2O) and 18 (10%) an inverted-J profile (PEEPmin_dPaw of 14,6 ± 2.3 cmH2O). Patients with inverted-J profiles had significant higher body mass index (BMI) and lower baseline partial pressure of arterial oxygen/FiO2 ratio. PEEPmin_dPaw was associated with lower fractions of both alveolar collapse and hyperinflation. CONCLUSIONS: A PEEP adjustment procedure based on PEEP-induced changes in dPaw is feasible and may aid in individualized PEEP for protective ventilation. The PEEP required to minimize driving pressure was influenced by BMI and was low in the majority of patients.

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BACKGROUND: Positive end-expiratory pressure (PEEP) can overcome respiratory changes that occur during pneumoperitoneum application in laparoscopic procedures, but it can also increase intracranial pressure. We investigated PEEP vs. no PEEP application on ultrasound measurement of optic nerve sheath diameter (indirect measure of increased intracranial pressure) in laparoscopic cholecystectomy. METHODS: Eighty ASA I-II patients aged between 18 and 60 years scheduled for elective laparoscopic cholecystectomy were included. The study was registered in the Australian New Zealand Clinical Trials (ACTRN12618000771257). Patients were randomly divided into either Group C (control, PEEP not applied), or Group P (PEEP applied at 10 cmH20). Optic nerve sheath diameter, hemodynamic, and respiratory parameters were recorded at six different time points. Ocular ultrasonography was used to measure optic nerve sheath diameter. RESULTS: Peak pressure (PPeak) values were significantly higher in Group P after application of PEEP (p = 0.012). Mean respiratory rate was higher in Group C at all time points after application of pneumoperitoneum (p < 0.05). The mean values of optic nerve sheath diameters measured at all time points were similar between the groups (p > 0.05). The pulmonary dynamic compliance value was significantly higher in group P as long as PEEP was applied (p = 0.001). CONCLUSIONS: During laparoscopic cholecystectomy, application of 10 cmH2O PEEP did not induce a significant change in optic nerve sheath diameter (indirect indicator of intracranial pressure) compared to no PEEP application. It would appear that PEEP can be used safely to correct respiratory mechanics in cases of laparoscopic cholecystectomy, with no significant effect on optic nerve sheath diameter.

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[This corrects the article DOI: 10.3389/fvets.2022.842613.].

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Background: Fluid regimens in acute respiratory distress syndrome (ARDS) are conflicting. The amount of fluid and positive end-expiratory pressure (PEEP) level may interact leading to ventilator-induced lung injury (VILI). We therefore evaluated restrictive and liberal fluid strategies associated with low and high PEEP levels with regard to lung and kidney damage, as well as cardiorespiratory function in endotoxin-induced ARDS. Methods: Thirty male Wistar rats received an intratracheal instillation of Escherichia coli lipopolysaccharide. After 24 h, the animals were anesthetized, protectively ventilated (VT = 6 ml/kg), and randomized to restrictive (5 ml/kg/h) or liberal (40 ml/kg/h) fluid strategies (Ringer lactate). Both groups were then ventilated with PEEP = 3 cmH2O (PEEP3) and PEEP = 9 cmH2O (PEEP9) for 1 h (n = 6/group). Echocardiography, arterial blood gases, and lung mechanics were evaluated throughout the experiments. Histologic analyses were done on the lungs, and molecular biology was assessed in lungs and kidneys using six non-ventilated animals with no fluid therapy. Results: In lungs, the liberal group showed increased transpulmonary plateau pressure compared with the restrictive group (liberal, 23.5 ± 2.9 cmH2O; restrictive, 18.8 ± 2.3 cmH2O, p = 0.046) under PEEP = 9 cmH2O. Gene expression associated with inflammation (interleukin [IL]-6) was higher in the liberal-PEEP9 group than the liberal-PEEP3 group (p = 0.006) and restrictive-PEEP9 (p = 0.012), Regardless of the fluid strategy, lung mechanical power and the heterogeneity index were higher, whereas birefringence for claudin-4 and zonula-ocludens-1 gene expression were lower in the PEEP9 groups. Perivascular edema was higher in liberal groups, regardless of PEEP levels. Markers related to damage to epithelial cells [club cell secreted protein (CC16)] and the extracellular matrix (syndecan) were higher in the liberal-PEEP9 group than the liberal-PEEP3 group (p = 0.010 and p = 0.024, respectively). In kidneys, the expression of IL-6 and neutrophil gelatinase-associated lipocalin was higher in PEEP9 groups, regardless of the fluid strategy. For the liberal strategy, PEEP = 9 cmH2O compared with PEEP = 3 cmH2O reduced the right ventricle systolic volume (37%) and inferior vena cava collapsibility index (45%). Conclusion: The combination of a liberal fluid strategy and high PEEP led to more lung damage. The application of high PEEP, regardless of the fluid strategy, may also be deleterious to kidneys.

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Objective: To evaluate gas exchange, respiratory mechanics, and hemodynamic impact of mechanical ventilation with low tidal volume (VT) in dogs with the use of positive end-expiratory pressure (PEEP) or preceded by alveolar recruitment maneuver (ARM). Study Design: Prospective randomized clinical trial. Animals: Twenty-one healthy client-owned mesocephalic healthy dogs, 1-7 years old, weighing 10-20 kg, and body condition scores 4-6/9 admitted for periodontal treatment. Methods: Isoflurane-anesthetized dogs in dorsal recumbency were ventilated until 1 h with a volume-controlled ventilation mode using 8 mL kg-1 of VT. The dogs were distributed in 2 groups: in the ARM group, PEEP starts in 0 cmH2O, increasing gradually 5 cmH2O every 3 min, until reach 15 cmH2O and decreasing in the same steps until 5 cmH2O, maintaining this value until the end; and PEEP group, in which the pressure 5 cmH2O was instituted from the beginning of anesthesia and maintained the same level up to the end of the anesthesia. Cardiopulmonary, metabolic, oxygenation parameters, and respiratory mechanics were recorded after the anesthesia induction (baseline-BL), 15, 45, and 75 min after BL and during the recovery. Results: The ARM increased the static compliance (Cst) (15 min after baseline) when compared with baseline moment (24.9 ± 5.8 mL cmH20-1 vs. 20.7 ± 5.4 mL cmH20-1-p = 0.0364), oxygenation index (PaO2/FIO2) (505.6 ± 59.2 mmHg vs. 461.2 ± 41.0 mmHg-p = 0.0453) and reduced the shunt fraction (3.4 ± 2.4% vs. 5.5 ± 1.6%-p = 0.062). In the PEEP group, no statistical differences were observed concerning the variables evaluated. At the beginning of the evaluation, the driving pressure (DP) before ARM was significantly greater than all other evaluation time points (6.9 ± 1.8 cmH20). Conclusions and Clinical Relevance: The use of 8 mL kg-1 of VT and 5 cmH20 PEEP without ARM maintain adequate oxygenation and mechanical ventilation in dental surgeries for up to 1 h. The use of ARM slightly improved compliance and oxygenation during the maneuver.

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La Injuria Pulmonar Autoinducida por el Paciente (p-SILI) es una entidad recientemente reconocida. Clásicamente, el daño producido por la ventilación mecánica (VM) se asoció al uso de presión positiva, y para disminuirlo se crearon distintas estrategias conocidas como parámetros de protección pulmonar. Sin embargo, es importante reconocer los potenciales efectos deletéreos de la ventilación espontánea dependientes de la injuria pulmonar previa que sufra el paciente y del esfuerzo que realice. En este artículo se explican los distintos mecanismos que pueden producir p-SILI y las estrategias descritas en la literatura para prevenirla (AU)

Patient self-inflicted lung injury (p-SILI) is a recently recognized disorder. Classically, damage produced by mechanical ventilation (MV) was associated with the use of positive pressure, and different strategies known as lung protection parameters were created to reduce it. Nevertheless, it is important to recognize the potential deleterious effects of the effort made during spontaneous breathing due to previous lung injury suffered by the patient. This article explains the different mechanisms that may produce p-SILI and the prevention strategies described in the literature. (AU)

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Resumen: Introducción: Desde diciembre de 2019, cuando el coronavirus respiratorio tipo 2 y el síndrome de insuficiencia respiratoria agudo (SDRA) por coronavirus tipo 2 (enfermedad por coronavirus 2019 [COVID-19]), se desarrolló en Wuhan, China, se ha convertido en una pandemia mundial, con 105'333.798 casos reportados el 04 de febrero de 2021. El 27 de febrero de 2020, la Ciudad de México reportó el primer caso de COVID-19, seguido de un crecimiento masivo de infecciones en todo el país. El número total de casos hasta hoy es de 1,886.245 con 81,223 casos activos estimados. El 18.77% de los pacientes han requerido hospitalización. El número total de muertes es de 164.290, con una estimación de 184.125. La lesión renal aguda (LRA) se encontró en 28% de los pacientes hospitalizados y en 46% de los pacientes en estado crítico, contribuyendo a una mortalidad significativamente mayor. La identificación de los factores de riesgo es importante para orientar la toma de decisiones tempranas en la clasificación de los pacientes para una monitorización más intensiva y prevenir el aumento de la mortalidad. Objetivo: Analizar el nivel de presión positiva al final de la espiración (PEEP) y factores inflamatorios que intervienen en el desarrollo de LRA e inicio de terapia de reemplazo renal (TRR) en pacientes con COVID-19. Material y métodos: Se realizó un estudio observacional, transversal y retrolectivo en pacientes con ventilación mecánica con SARS-CoV-2 que presentaron LRA y necesidad de TRR ingresados en la Unidad de Cuidados Intensivos Respiratorios del Centro Médico ABC. Se realizó análisis estadístico de medidas de tendencia central, descriptivo; para la identificación de la variable con mayor impacto para el desarrollo de LRA y terapia dialítica se realizó factor predictivo positivo, prueba Pearson para correlacionar con terapia de reemplazo renal. El estudio se aprobó por el Comité de Ética del Centro Médico ABC, Ciudad de México (Folio: ABC TAEABC-22-117). Resultados: Se analizaron en total 210 pacientes con ventilación mecánica con SARS-CoV-2 en la Unidad de Cuidados Intensivos Respiratorios del Centro Médico ABC, de los cuales, 51 (24.17%) desarrollaron LRA y 21 requirieron TRR. Se realizó una curva ROC para predecir el factor con mayor riesgo para presentar LRA, encontrando diferencias significativas en IL-6 con un área bajo la curva ROC de 0.909 (CI: 0.86-0.95). También se encontró significancia estadística en LRA a partir de PEEP por arriba de 13 cmH2O y terapia de reemplazo renal con PEEP > 15 cmH2O. Conclusión: Se encontró una correlación de niveles altos de PEEP y lesión renal aguda. Los marcadores inflamatorios al ingreso del paciente (específicamente IL-6) son parámetros adecuados para guiar el tratamiento; sin embargo, también son de utilidad para orientar a un pronóstico.

Abstract: Introduction: Since December 2019, when respiratory coronavirus type 2 and acute respiratory failure syndrome (ARDS) due to coronavirus type 2 (coronavirus disease 2019 [COVID-19]), developed in Wuhan, China, it has become a global pandemic, with 105,333,798 cases reported on February 4, 2021. On February 27, 2020, Mexico City reported the first case of COVID-19, followed by a massive growth of infections across the country. The total number of cases today is 1,886,245 with 81,223 estimated active cases. 18.77% of patients have required hospitalization. The total number of deaths is 164,290 with an estimated 184,125. AKI was found in 28% of hospitalized patients and 46% of critically ill patients, contributing to significantly higher mortality. Identification of risk factors is important to guide early decision making in triaging patients for more intensive monitoring and prevent increased mortality. Objective: To analyze the level of PEEP and inflammatory factors involved in the development of AKI and onset of RRT in patients with COVID-19. Material and methods: An observational, cross-sectional and retrolective study was performed in mechanically ventilated patients with SARS-CoV-2 who presented AKI and need for RRT admitted to the respiratory intensive care unit of the ABC Medical Center. Statistical analysis of measures of central tendency, descriptive; for the identification of the variable with the greatest impact for the development of AKI and dialytic therapy, a positive predictive factor was performed, Pearson test to correlate with renal replacement therapy. The study was approved by the ethics committee of the ABC Medical Center, Mexico City (Number: ABC TAEABC-22-117). Results: A total of 210 mechanically ventilated patients with SARS-CoV-2 in the Respiratory Intensive Care Unit of the ABC Medical Center were analyzed, of whom 51 patients (24.17%) developed AKI and 21 patients required RRT. An ROC curve was performed to predict the factor with the highest risk of developing AKI, finding significant differences in IL-6 with an area under the ROC curve of 0.909 (CI: 0.86-0.95). Statistical significance was found in AKI with PEEP above 13cmH2O and renal replacement therapy with PEEP > 15cmH2O. Conclusion: A correlation was found between high PEEP levels and acute kidney injury. Inflammatory markers at patient admission (specifically IL-6) are adequate parameters to guide treatment; however, they are also useful to guide prognosis.

Resumo: Introdução: Desde dezembro de 2019, quando o coronavírus respiratório tipo 2 e a síndrome do desconforto respiratório agudo do coronavírus (SDRA) (doença de coronavírus 2019 [COVID-19]), desenvolvida em Wuhan, China, tornou-se uma pandemia em todo o mundo, com 105'333.798 casos relatados em fevereiro 4, 2021. Em 27 de fevereiro de 2020, a Cidade do México relatou o primeiro caso de COVID-19, seguido por um crescimento maciço de infecções em todo o país. O número total de casos até o momento é de 1,886.245, com uma estimativa de 81,223 casos ativos. 18.77% dos pacientes necessitaram de internação. O número total de óbitos é de 164.290, com estimativa de 184.125. A LRA foi encontrada em 28% dos pacientes hospitalizados e 46% dos pacientes críticos, contribuindo para uma mortalidade significativamente maior. A identificação dos fatores de risco é importante para orientar a tomada de decisão precoce na classificação dos pacientes para monitoramento mais intensivo e para evitar o aumento da mortalidade. Objetivo: Analisar o nível de PEEP e fatores inflamatórios envolvidos no desenvolvimento de LRA e início de TRS em pacientes com COVID-19. Material e métodos: Realizou-se um estudo observacional, transversal e retroletivo em pacientes ventilados mecanicamente com SARS-CoV-2 que apresentavam LRA e necessidade de TRS internados na unidade de terapia intensiva respiratória do Centro Médico ABC. Foi realizado análise estatística de medidas de tendência central, descritiva; para identificar a variável de maior impacto no desenvolvimento de LRA e terapia dialítica, realizou-se fator preditivo positivo, o teste de Pearson para correlacionar com a terapia renal substitutiva. O estudo foi aprovado pelo comitê de ética do Centro Médico ABC, Cidade do México (Folio: ABC TAEABC-22-117). Resultados: Foram analisados um total de 210 pacientes com ventilação mecânica com SARS-CoV-2 na unidade de terapia intensiva respiratória do Centro Médico ABC, dos quais 51 pacientes (24.17%) desenvolveram LRA e 21 pacientes requereram TRS. Realizou-se uma curvatura ROC para prever o fator com maior risco para apresentar LRA encontrando diferenças significativas em IL-6 com uma área sob a curvatura ROC de 0.909(CI: 0.86-0.95). Da mesma forma, foi encontrada significância estatística na LRA por PEEP acima de 13 cmH2O e terapia renal substitutiva com PEEP > 15 cmH2O. Conclusão: Encontrou-se uma correlação entre níveis elevados de PEEP e lesão renal aguda. Marcadores inflamatórios na admissão do paciente (especificamente IL-6) são parâmetros adequados para orientar o tratamento; no entanto, eles também são úteis para orientar uma previsão.

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Resumen: Introducción: el uso de presión positiva al final de la espiración mejora la oxigenación y recluta alvéolos, aunque también provoca alteraciones hemodinámicas e incrementa la presión intracraneal. Material y métodos: se realizó un estudio preexperimental de un solo grupo en pacientes pediátricos aquejados de traumatismo craneoencefálico grave, con hipoxemia asociada, tratados con diferentes niveles de presión positiva al final de la espiración, a los que se les monitorizó la presión intracraneal y la presión de perfusión cerebral para evaluar el efecto de esta maniobra ventilatoria en las variables intracraneales. Resultados: predominaron las edades entre cinco y 17 años, 14 (73.68%) y la escala de coma de Glasgow al ingreso de ocho a nueve puntos (47.36%). La presión intracraneal aumenta cuando la presión positiva al final de la espiración supera los 12 cmH2O. La escala de coma de Glasgow al ingreso de ocho puntos se asoció con secuelas ligeras o ausencia de secuelas (47.36%), todos los niños con tres puntos fallecieron. Conclusiones: el empleo de presión positiva al final de la espiración en el traumatismo craneoencefálico grave requiere de monitorización continua de la presión intracraneal. Corregir la hipertensión intracraneal y la inestabilidad hemodinámica son condiciones necesarias previas al tratamiento.

Abstract: Introduction: the use of positive end expiratory pressure improves oxygenation and recruits pulmonary alveoli, however at the same time it leads to hemodynamic changes and increase intracranial pressure. Material and methods: a prospective descriptive study was done with pediatric patients afflicted with severe traumatic brain injury associated with hypoxemia and treated with different levels of positive end expiratory pressure, to whom the intracranial pressure and cerebral perfusion pressure were monitored so as to evaluate the effect of this ventilation maneuver over the intracranial variables. Results: patients with age between 5-17 years old as well as male sex, 14 (73.68%) were predominant. 9 (47.36%) showed Glasgow coma scale of 8 points on admission. Intracranial pressure starts to rise when the positive end expiratory pressure exceeds 12 cmH2O. Glasgow coma scale with 8 points was associated with mild disability or no disability (47.36%). All the patients that scored 3 points died. Conclusions: the use of positive end expiratory pressure to correct hypoxemia was an applicable therapeutic alternative as long as continuous intracranial pressure monitoring was available in a systematic and personalized way. The correction of intracranial hypertension and hemodynamic instability were a necessary condition before using the ventilatory maneuver in these patients.

Resumo: Introdução: o uso de pressão positiva no final da expiração melhora a oxigenação e recruta alvéolos, embora também cause alterações hemodinâmicas e aumente a pressão intracraniana. Material e métodos: realizou-se um estudo pré-experimental de um único grupo em pacientes pediátricos vítimas de traumatismo cranioencefálico grave, com hipoxemia associada, tratados com diferentes níveis de pressão positiva ao final da expiração, nos quais foram monitoradas a pressão intracraniana e a pressão de perfusão cerebral, para avaliar o efeito desta manobra ventilatória em variáveis intracranianas. Resultados: predominou a faixa etária entre 5-17 anos, 14 (73.68%) e a escala de coma de Glasgow na admissão de 8 pontos, 9 (47.36%). A pressão intracraniana aumenta quando a pressão positiva no final da expiração excede 12 cmH2O. A escala de coma de Glasgow na admissão de 8 pontos foi associada a sequelas leves ou sem sequelas (47.36%), todas as crianças com 3 pontos morreram. Conclusões: a utilização de pressão positiva no final da expiração no TCE grave requer monitorização contínua da pressão intracraniana. A correção da hipertensão intracraniana e da instabilidade hemodinâmica são condições necessárias prévias ao tratamento.

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BACKGROUND: Mechanical ventilation can injure lung tissue and respiratory muscles. The aim of the present study is to assess the effect of the amount of spontaneous breathing during mechanical ventilation on patient outcomes. METHODS: This is an analysis of the database of the 'Medical Information Mart for Intensive Care (MIMIC)'-III, considering intensive care units (ICUs) of the Beth Israel Deaconess Medical Center (BIDMC), Boston, MA. Adult patients who received invasive ventilation for at least 48 hours were included. Patients were categorized according to the amount of spontaneous breathing, i.e., ≥50% ('high spontaneous breathing') and <50% ('low spontaneous breathing') of time during first 48 hours of ventilation. The primary outcome was the number of ventilator-free days. RESULTS: In total, the analysis included 3,380 patients; 70.2% were classified as 'high spontaneous breathing', and 29.8% as 'low spontaneous breathing'. Patients in the 'high spontaneous breathing' group were older, had more comorbidities, and lower severity scores. In adjusted analysis, the amount of spontaneous breathing was not associated with the number of ventilator-free days [20.0 (0.0-24.2) vs. 19.0 (0.0-23.7) in high vs. low; absolute difference, 0.54 (95% CI, -0.10 to 1.19); P=0.101]. However, 'high spontaneous breathing' was associated with shorter duration of ventilation in survivors [6.5 (3.6 to 12.2) vs. 7.6 (4.1 to 13.9); absolute difference, -0.91 (95% CI, -1.80 to -0.02); P=0.046]. CONCLUSIONS: In patients surviving and receiving ventilation for at least 48 hours, the amount of spontaneous breathing during this period was not associated with an increased number of ventilator-free days.

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BACKGROUND AND OBJECTIVES: With the intensive study of lung protective ventilation strategies, people begin to advocate the individualized application of positive end-expiratory pressure (PEEP). This study investigated the optimal PEEP in patients during one-lung ventilation (OLV) and its effects on pulmonary mechanics and oxygenation. METHODS: Fifty-eight patients who underwent elective thoracoscopic lobectomy were randomly divided into two groups. Both groups received an alveolar recruitment maneuver (ARM) after OLV. Patients in Group A received optimal PEEP followed by PEEP decremental titration, while Group B received standard 5 cmH2O PEEP until the end of OLV. Relevant indexes of respiratory mechanics, pulmonary oxygenation and hemodynamics were recorded after entering the operating room (T0), 10 minutes after intubation (T1), pre-ARM (T2), 20 minutes after the application of optimal PEEP (T3), at the end of OLV (T4) and at the end of surgery (T5). Postoperative outcomes were also assessed. RESULTS: The optimal PEEP obtained in Group A was 8.8 ± 2.4 cmH2O, which positively correlated with BMI and forced vital capacity (FVC). Group A had a higher CPAT than Group B at T3, T4, T5 (p < 0.05) and a smaller ΔP than Group B at T3, T4 (p < 0.01). At T4, PaO2 was significantly higher in Group A (p < 0.01). At T3, stroke volume variation was higher in Group A (p < 0.01). Postoperative outcomes did not differ between the two groups. CONCLUSIONS: Our findings suggest that the individualized PEEP can increase lung compliance, reduce driving pressure, and improve pulmonary oxygenation in patients undergoing thoracoscopic lobectomy, with little effect on hemodynamics.

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RESUMO Objetivo: Avaliar se a diminuição da pressão arterial provocada pela elevação da pressão parcial positiva final corresponde à variação da pressão de pulso como indicador de fluido-responsividade. Métodos: Estudo de caráter exploratório que incluiu prospectivamente 24 pacientes com choque séptico ventilados mecanicamente e submetidos a três etapas de elevação da pressão parcial positiva final: de 5 para 10cmH2O (nível da pressão parcial positiva final 1), de 10 para 15cmH2O (nível da pressão parcial positiva final 2) e de 15 para 20cmH2O (nível da pressão parcial positiva final 3). Alterações da pressão arterial sistólica, da pressão arterial média e da variação da pressão de pulso foram avaliadas durante as três manobras. Os pacientes foram classificados como responsivos (variação da pressão de pulso ≥ 12%) e não responsivos a volume (variação da pressão de pulso < 12%). Resultados: O melhor desempenho para identificar pacientes com variação da pressão de pulso ≥ 12% foi observado no nível da pressão parcial positiva final 2: variação de pressão arterial sistólica de -9% (área sob a curva de 0,73; IC95%: 0,49 - 0,79; p = 0,04), com sensibilidade de 63% e especificidade de 80%. A concordância foi baixa entre a variável de melhor desempenho (variação de pressão arterial sistólica) e a variação da pressão de pulso ≥ 12% (kappa = 0,42; IC95%: 0,19 - 0,56). A pressão arterial sistólica foi < 90mmHg no nível da pressão parcial positiva final 2 em 29,2% dos casos e em 41,6,3% no nível da pressão parcial positiva final 3. Conclusão: Variações da pressão arterial em resposta à elevação da pressão parcial positiva final não refletem de modo confiável o comportamento da variação da pressão de pulso para identificar o status da fluido-responsividade.

Abstract Objective: To evaluate whether the decrease in blood pressure caused by the increase in the positive end-expiratory pressure corresponds to the pulse pressure variation as an indicator of fluid responsiveness. Methods: This exploratory study prospectively included 24 patients with septic shock who were mechanically ventilated and subjected to three stages of elevation of the positive end-expiratory pressure: from 5 to 10cmH2O (positive end-expiratory pressure level 1), from 10 to 15cmH2O (positive end-expiratory pressure level 2), and from 15 to 20cmH2O (positive end-expiratory pressure level 3). Changes in systolic blood pressure, mean arterial pressure, and pulse pressure variation were evaluated during the three maneuvers. The patients were classified as responsive (pulse pressure variation ≥ 12%) or unresponsive to volume replacement (pulse pressure variation < 12%). Results: The best performance at identifying patients with pulse pressure variation ≥ 12% was observed at the positive end-expiratory pressure level 2: -9% systolic blood pressure variation (area under the curve 0.73; 95%CI: 0.49 - 0.79; p = 0.04), with a sensitivity of 63% and specificity of 80%. Concordance was low between the variable with the best performance (variation in systolic blood pressure) and pulse pressure variation ≥ 12% (kappa = 0.42; 95%CI: 0.19 - 0.56). The systolic blood pressure was < 90mmHg at positive end-expiratory pressure level 2 in 29.2% of cases and at positive end-expiratory pressure level 3 in 41.63% of cases. Conclusion: Variations in blood pressure in response to the increase in positive end-expiratory pressure do not reliably reflect the behavior of the pulse pressure as a measure to identify the fluid responsiveness status.

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RESUMEN Objetivo: Comparar las medidas de gasto cardiaco por ecocardiografía transtorácica y por catéter arterial pulmonar en pacientes en ventilación mecánica con presión positiva al final de la espiración elevada. Evaluar el efecto de la insuficiencia tricúspide. Métodos: Se estudiaron 16 pacientes en ventilación mecánica. El gasto cardiaco se midió con el catéter arterial pulmonar y por ecocardiografía transtorácica. Las medidas se realizaron en diferentes niveles de presión positiva al final de la espiración (10cmH2O, 15cmH2O, y 20cmH2O). Se evalúo el efecto de la insuficiencia tricúspide sobre la medida de gasto cardiaco. Se estudió el coeficiente de correlación intraclase; el error medio y los límites de concordancia se estudiaron con el diagrama de Bland-Altman. Se calculó el porcentaje de error. Resultados: Se obtuvieron 44 pares de medidas de gasto cardiaco. Se obtuvo un coeficiente de correlación intraclase de 0,908, p < 0,001; el error medio fue 0,44L/min para valores de gasto cardíaco entre 5 a 13L/min. Los límites de concordancia se encontraron entre 3,25L/min y -2,37L/min. Con insuficiencia tricúspide el coeficiente de correlación intraclase fue 0,791, sin insuficiencia tricúspide el coeficiente de correlación intraclase fue 0,935. La presencia de insuficiencia tricúspide aumentó el porcentaje de error de 32 % a 52%. Conclusiones: En pacientes con presión positiva al final de la espiración elevada la medida de gasto cardiaco por ecocardiografía transtorácica es comparable con catéter arterial pulmonar. La presencia de insuficiencia tricúspide influye en el coeficiente de correlación intraclase. En pacientes con presión positiva al final de la espiración elevada, el uso de ecocardiografía transtorácica para medir gasto cardiaco es comparable con las medidas invasivas.

ABSTRACT Objective: To compare cardiac output measurements by transthoracic echocardiography and a pulmonary artery catheter in mechanically ventilated patients with high positive end-expiratory pressure. To evaluate the effect of tricuspid regurgitation. Methods: Sixteen mechanically ventilated patients were studied. Cardiac output was measured by pulmonary artery catheterization and transthoracic echocardiography. Measurements were performed at different levels of positive end-expiratory pressure (10cmH2O, 15cmH2O, and 20cmH2O). The effect of tricuspid regurgitation on cardiac output measurement was evaluated. The intraclass correlation coefficient was studied; the mean error and limits of agreement were studied with the Bland-Altman plot. The error rate was calculated. Results: Forty-four pairs of cardiac output measurements were obtained. An intraclass correlation coefficient of 0.908 was found (p < 0.001). The mean error was 0.44L/min for cardiac output values between 5 and 13L/min. The limits of agreement were 3.25L/min and -2.37L/min. With tricuspid insufficiency, the intraclass correlation coefficient was 0.791, and without tricuspid insufficiency, 0.935. Tricuspid insufficiency increased the error rate from 32% to 52%. Conclusions: In patients with high positive end-expiratory pressure, cardiac output measurement by transthoracic echocardiography is comparable to that with a pulmonary artery catheter. Tricuspid regurgitation influences the intraclass correlation coefficient. In patients with high positive end-expiratory pressure, the use of transthoracic echocardiography to measure cardiac output is comparable to invasive measures.

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Introdução: Os pacientes submetidos a cirurgias abdominais possuem riscos de complicações pulmonares no período pós-operatório, tais como: diminuição da atividade respiratória, alteração da relação ventilação/perfusão e intensificação no trabalho dos músculos respiratórios, aumentando a morbidade e a mortalidade hospitalar. Objetivo: Avaliar o impacto da pressão positiva expiratória na função pulmonar em pacientes no pós-operatório de cirurgias abdominal eletiva. Métodos: Caracteriza-se como um estudo exploratório do tipo ensaio clínico randomizado, composto por 40 pacientes randomizados em dois grupos, grupo intervenção foi submetido a um protocolo de pressão positiva expiratória nas vias respiratórias com pressão positiva expiratória final de 10 cmH2O e deambulação por 150 metros e o grupo controle realizou deambulação por 150 metros e orientações sobre a importância da inspiração profunda a cada duas horas, sendo realizada avaliação no pós-operatório imediato e no momento da alta hospitalar. Resultados: Pode-se perceber um padrão homogêneo entre os grupos estudados, observou-se significância estatística na análise intragrupos nas variáveis saturação periférica de oxigênio (p < 0,0001) e no pico de fluxo expiratório (p = 0,009) e na capacidade vital forçada (p < 0,0001). Na análise entre os grupos observou-se diferença estatística na saturação periférica de oxigênio (p = 0,010) e no pico de fluxo expiratório (p = 0,012). Conclusão: Pode-se concluir, no presente estudo, que a utilização da pressão positiva expiratória no pós-operatório de cirurgias abdominais impactou positivamente na saturação periférica de oxigênio e no pico de fluxo expiratório, demonstrando um benefício significativo no processo ventilatório e difusional no grupo estudado. (AU)

Introduction: Patients undergoing abdominal surgery have a risk of pulmonary complications in the postoperative period, such as: decreased respiratory activity, altered ventilation / perfusion ratio, and increased respiratory muscle work, increasing hospital morbidity and mortality. Objective: To evaluate the impact of positive expiratory pressure on lung function in postoperative patients of elective abdominal surgeries. Methods: Characterized as an exploratory study of the type randomized clinical trial, composed of 40 patients randomized into two groups, the intervention group was submitted to a protocol of positive expiratory pressure in the respiratory tract with final expiratory positive pressure of 10 cmH2O and ambulation for 150 meters and the control group underwent walking for 150 meters and guidelines on the importance of deep inspiration every two hours, being evaluated in the immediate postoperative period and at the time of hospital discharge. Results: A homogeneous pattern could be observed between the groups studied. Statistical significance was observed in the intra-group analysis in the variables peripheral oxygen saturation (p <0.0001) and peak expiratory flow (p = 0.009) vital forcing (p <0.0001). In the analysis between groups, a statistical difference was observed in peripheral oxygen saturation (p = 0.010) and peak expiratory flow (p = 0.012). Conclusion: We concluded that the use of positive expiratory pressure in the postoperative period of abdominal surgeries had a positive impact on peripheral oxygen saturation and peak expiratory flow, demonstrating a significant benefit in the ventilatory and diffusional process in the studied group. (AU)

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Acute respiratory distress syndrome was first described by Ashbaugh, Petty, Levine y Bigellow in 1967 writing in The Lancet. Their study was based on a case series of 12 patients with acute respiratory distress, cyanosis refractory to oxygen therapy, decreased lung compliance and diffuse infiltrates evident on the chest radiograph. Mortality was 58% with greater survival in five patients managed with mechanical ventilation and positive end expiratory pressure. Histopathology revealed heavy lungs, atelectasis, interstitial and alveolar edema, as well as hyaline membranes. 50 years after the publication of this article, advances in knowledge and management of this disease have been considerable, which is reflected in decreased mortality. The aim of this paper is to describe the original publication, recognize its importance and genious of its authors, to celebrate the 50th anniversary of this landmark and fundamental paper in intensive care medicine and honor their authors.

El síndrome de insuficiencia respiratoria aguda fue descrito por primera vez en la revista The Lancet en el año 1967 por Ashbaugh, Petty, Levine y Bigellow. Su estudio se fundamenta en la descripción de una serie de 12 enfermos que presentaban insuficiencia respiratoria aguda, cianosis refractaria a tratamiento con oxígeno, disminución de la distensibilidad pulmonar e infiltrados difusos en la radiografía de tórax. La mortalidad fue del 58%, con más oportunidad de sobrevida en aquellos enfermos manejados con ventilación mecánica y presión positiva al final de la espiración. El estudio histopatológico mostró pulmones de mayor peso, atelectasias, edema intersticial y alveolar, y membranas hialinas. A 50 años de su publicación, se han logrado importantes avances en el conocimiento y el tratamiento de esta enfermedad, lo que se ha reflejado en una disminución de la mortalidad. El objetivo de este trabajo es describir la publicación original y reconocer su importancia y la genialidad de los autores, para de esta manera celebrar el cincuentenario de este artículo clave y fundamental en la medicina intensiva y hacer un justo homenaje a los que participaron en su publicación.

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Intraoperative positive end-expiratory pressure (PEEP) has been proposed to restore lung volumes and improve respiratory function in obesity. However, the biological impact of different PEEP levels on the lungs in obesity remains unknown. We aimed to compare the effects of PEEP = 2 cmH2O versus PEEP = 6 cmH2O during ventilation with low tidal volumes on lung function, histology, and biological markers in obese and non-obese rats undergoing open abdominal surgery. Forty-two Wistar rats (21 obese, 21 non-obese) were anesthetized and tracheotomized, and laparotomy was performed with standardized bowel manipulation. Rats were randomly ventilated with protective tidal volume (7 ml/kg) at PEEP = 2 cmH2O or PEEP = 6 cmH2O for 4 h, after which they were euthanized. Lung mechanics and histology, alveolar epithelial cell integrity, and biological markers associated with pulmonary inflammation, alveolar stretch, extracellular matrix, and epithelial and endothelial cell damage were analyzed. In obese rats, PEEP = 6 cmH2O compared with PEEP = 2 cmH2O was associated with less alveolar collapse (p = 0.02). E-cadherin expression was not different between the two PEEP groups. Gene expressions of interleukin (IL)-6 (p = 0.01) and type III procollagen (p = 0.004), as well as protein levels of tumor necrosis factor-alpha (p = 0.016), were lower at PEEP = 6 cmH2O than at PEEP = 2 cmH2O. In non-obese animals, PEEP = 6 cmH2O compared with PEEP = 2 cmH2O led to increased hyperinflation, reduced e-cadherin (p = 0.04), and increased gene expression of IL-6 (p = 0.004) and protein levels of tumor necrosis factor-alpha (p-0.029), but no changes in fibrogenesis. In conclusion, PEEP = 6 cmH2O reduced lung damage and inflammation in an experimental model of mechanical ventilation for open abdominal surgery, but only in obese animals.

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Mechanical ventilation is a life-support system used to maintain adequate lung function in patients who are critically ill or undergoing general anesthesia. The benefits and harms of mechanical ventilation depend not only on the operator's setting of the machine (input), but also on their interpretation of ventilator-derived parameters (outputs), which should guide ventilator strategies. Once the inputs-tidal volume (VT), positive end-expiratory pressure (PEEP), respiratory rate (RR), and inspiratory airflow (V')-have been adjusted, the following outputs should be measured: intrinsic PEEP, peak (Ppeak) and plateau (Pplat) pressures, driving pressure (ΔP), transpulmonary pressure (PL), mechanical energy, mechanical power, and intensity. During assisted mechanical ventilation, in addition to these parameters, the pressure generated 100 ms after onset of inspiratory effort (P0.1) and the pressure-time product per minute (PTP/min) should also be evaluated. The aforementioned parameters should be seen as a set of outputs, all of which need to be strictly monitored at bedside in order to develop a personalized, case-by-case approach to mechanical ventilation. Additionally, more clinical research to evaluate the safe thresholds of each parameter in injured and uninjured lungs is required.