The effects of positive end-expiratory pressure (PEEP) application on optic nerve sheath diameter in patients undergoing laparoscopic cholecystectomy: a randomized trial

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

Efeito da manobra de recrutamento alveolar no pós-operatório imediato de cirurgia cardíaca: uma revisão sistemática / Effect of the alveolar recruitment maneuver in the immediate postoperative period of cardiac surgery: a systematic review

Introdução: as cirurgias cardíacas são as intervenções de escolha em níveis mais avançados das doenças cardiovasculares, e complicações pulmonares podem ocorrer como consequência das alterações fisiológicas causadas pela circulação extracorpórea, pela anestesia e pela incisão esterno torácica. A fisioterapia atua com o intuito de prevenir e tratar essas complicações, através da utilização de uma das técnicas de expansão pulmonar mais utilizadas na reversão de hipoxemia e atelectasias, a manobra de recrutamento alveolar, com o objetivo de abrir alvéolos colapsados e aumentar as trocas gasosas. Objetivo: revisar sistematicamente os efeitos da manobra, na relação PaO2/FiO2, SatO2, o tempo de ventilação mecânica, o tempo de internamento, a incidência de atelectasia, a pressão arterial média e a frequência cardíaca. Metodologia: revisão de ensaios clínicos controlados e randomizados nas bases de dados PubMed, Cochrane Library, LILACS e PEDro. Foram incluídos estudos que utilizaram a manobra como prevenção de complicações pulmonares, publicados em inglês e português. Resultados: foram incluídos 4 estudos, publicados entre os anos 2005 e 2017. O nível de pressão da manobra variou entre 30 cmH2O a 40 cmH2O. Os estudos mostraram que a manobra foi estatisticamente relevante na relação PaO2/FiO2, SatO2 e na redução da incidência de atelectasias, sem impacto no tempo de ventilação mecânica, no tempo de internamento, na pressão arterial média e na frequência cardíaca. Conclusão: a manobra de recrutamento pode ser considerada como uma técnica a ser utilizada na prevenção de alterações pulmonares, porém não é possível afirmar se os benefícios da manobra perduraram em longo prazo.

Introduction: Cardiac surgeries are the interventions of choice in more advanced levels of cardiovascular disease, and pulmonary complications can occur as a result of physiological changes caused by cardiopulmonary bypass, anaesthesia and the sternum thoracic incision. Physiotherapy acts with the aim of preventing and treating these complications, through the use of one of the most used lung expansion techniques in the reversal of hypoxemia and atelectasis, the alveolar recruitment maneuver, with the objective of opening collapsed alveoli and increasing gas exchanges. Objective: To systematically review the effects of the maneuver on the PaO2/FiO2 ratio, SatO2, duration of mechanical ventilation, length of hospitalization, incidence of atelectasis, mean arterial pressure and heart rate. Methodology: Review of controlled and randomized clinical trials in PubMed, Cochrane Library, LILACS and PEDro databases. Studies that used the maneuver to prevent pulmonary complications, published in English and Portuguese, were included. Results: 4 studies, published between 2005 and 2017, were included. The maneuver pressure level ranged from 30 cmH2O to 40 cmH2O. The studies showed that the maneuver was statistically relevant in relation to PaO2/FiO2, SatO2 and in reducing the incidence of atelectasis, with no impact on the duration of mechanical ventilation, length of hospitalization, mean arterial pressure and heart rate. Conclusion: The recruitment maneuver can be considered as a technique to be used in the prevention of pulmonary alterations; however, it is not possible to state whether the benefits of the maneuver lasted in the long term.

Research advances on neurally adjusted ventilatory assist / 中华危重病急救医学

Mechanical ventilation has, since its introduction into clinical practice, undergone a major evolution from controlled ventilation to diverse modes of assisted ventilation. Conventional mechanical ventilators depend on flow sensors and pneumatic pressure and controllers to complete the respiratory cycle. Neurally adjusted ventilatory assist (NAVA) is a new form of assisted ventilation in recent years, which monitors the electrical activity of the diaphragm (EAdi) to provide an appropriately level of pressure support. And EAdi is the best available signal to sense central respiratory drive and trigger ventilatory assist. Unlike other ventilation modes, NAVA breathing instructions come from the center. Therefore, NAVA have the synchronous nature of the breaths and the patient-adjusted nature of the support. Compared with traditional ventilation mode, NAVA can efficiently unload respiratory muscles, relieve the risk of ventilator-induced lung injury (VILI), improve patient-ventilator coordination, enhance gas exchange, increase the success rate of weaning, etc. This article reviews the research progress of NAVA in order to provide theoretical guidance for clinical applications.

Respiratory mechanics analysis of inspiratory trigger in mechanical ventilation / 中华危重病急救医学

OBJECTIVE@#To find out the circuit pressure and flow at the trigger point by observing the characteristics of the inspiratory trigger waveform of the ventilator, confirm the intra-alveolar pressure as the index to reflect the effort of the trigger according to the working principle of the ventilator combined with the laws of respiratory mechanics, establish the related mathematical formula, and analyze its influencing factors and logical relationship.@*METHODS@#A test-lung was connected to the circuit in a PB840 ventilator and a SV600 ventilator set in pressure-support mode. The positive end-expiratory pressure (PEEP) was set at 5 cmH2O (1 cmH2O ≈ 0.098 kPa), and the wall of test-lung was pulled outwards till an inspiratory was effectively triggered separately in slow, medium, fast power, and separately in flow-trigger mode (sensitivity VTrig 3 L/min, 5 L/min) and pressure-trigger mode (sensitivity PTrig 2 cmH2O, 4 cmH2O). By adjusting the scale of the curve in the ventilator display, the loop pressure and flow corresponding to the trigger point under different triggering conditions were observed. Taking intraalveolar pressure (Pa) as the research object, the Pa (called Pa-T) needed to reach the effective trigger time (TT) was analyzed in the method of respiratory mechanics, and the amplitude of pressure change (ΔP) and the time span (ΔT) of Pa during triggering were also analyzed.@*RESULTS@#(1) Corresponding relationship between pressure and flow rate at TT time: in flow-trigger mode, in slow, medium and fast trigger, the inhalation flow rate was VTrig, and the circuit pressure was separately PEEP, PEEP-Pn, and PEEP-Pn' (Pn, Pn', being the decline range, and Pn' > Pn). In pressure-trigger mode, the inhalation flow rate was 1 L/min (PB840 ventilator) or 2 L/min (SV600 ventilator), and the circuit pressure was PEEP-PTrig. (2) Calculation of Pa-T: in flow-trigger mode, in slow trigger: Pa-T = PEEP-VTrigR (R represented airway resistance). In medium trigger: Pa-T = PEEP-Pn-VTrigR. In fast trigger: Pa-T = PEEP-Pn'-VTrigR. In pressure-trigger mode: Pa-T = PEEP-PTrig-1R. (3) Calculation of ΔP: in flow trigger mode, in flow trigger: without intrinsic PEEP (PEEPi), ΔP = VTrigR; with PEEPi, ΔP = PEEPi-PEEP+VTrigR. In medium trigger: without PEEPi, ΔP = Pn+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn+VTrigR. In fast trigger: without PEEPi, ΔP = Pn'+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn'+VTrigR. In pressure-trigger mode, without PEEPi, ΔP = PTrig+1R; with PEEPi, ΔP = PEEPi-PEEP+PTrig+1R. (4) Pressure time change rate of Pa (FP): FP = ΔP/ΔT. In the same ΔP, the shorter the ΔT, the greater the triggering ability. Similarly, in the same ΔT, the bigger the ΔP, the greater the triggering ability. The FP could better reflect the patient's triggering ability.@*CONCLUSIONS@#The patient's inspiratory effort is reflected by three indicators: the minimum intrapulmonary pressure required for triggering, the pressure span of intrapulmonary pressure, and the pressure time change rate of intrapulmonary pressure, and formula is established, which can intuitively present the logical relationship between inspiratory trigger related factors and facilitate clinical analysis.

Interpretation of new concepts and approaches in the ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies / 中华危重病急救医学

Acute respiratory distress syndrome (ARDS) continues to be one of the most life-threatening conditions for patients in the intensive care unit (ICU). The 2023 European Society of Intensive Care Medicine guidelines on ARDS: definition, phenotyping and respiratory support strategies (2023 Guideline) update the 2017 An Official American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline: mechanical ventilation in adult patients with ARDS (2017 Guideline), including 7 aspects of 3 topics of definitions, phenotyping, and respiratory support strategies [including high flow nasal cannula oxygen (HFNO), non-invasive ventilation (NIV), neuromuscular blocking agents (NMBA), extracorporeal life support (ECLS), positive end-expiratory pressure (PEEP) with recruitment maneuvers (RM), tidal volume (VT), and prone positioning]. 2023 Guideline review and summarize the literature since the publication of the 2017 Guideline, covering ARDS and acute hypoxemic respiratory failure, as well as ARDS caused by novel coronavirus infection. Based on the most recent medical evidence, the 2023 Guideline provide clinicians with new ideas and approaches for nonpharmacologic respiratory support strategies for adults with ARDS. This article provides interpretation of the new concepts, the new approaches, the new recommended grading and new levels of evidence for ARDS in the 2023 Guideline.

Modeling the noninvasive bi-level positive airway pressure ventilation therapy system and simulated application / 生物医学工程学杂志

Without artificial airway though oral, nasal or airway incision, the bi-level positive airway pressure (Bi-PAP) has been widely employed for respiratory patients. In an effort to investigate the therapeutic effects and measures for the respiratory patients under the noninvasive Bi-PAP ventilation, a therapy system model was designed for virtual ventilation experiments. In this system model, it includes a sub-model of noninvasive Bi-PAP respirator, a sub-model of respiratory patient, and a sub-model of the breath circuit and mask. And based on the Matlab Simulink, a simulation platform for the noninvasive Bi-PAP therapy system was developed to conduct the virtual experiments in simulated respiratory patient with no spontaneous breathing (NSB), chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). The simulated outputs such as the respiratory flows, pressures, volumes, etc, were collected and compared to the outputs which were obtained in the physical experiments with the active servo lung. By statistically analyzed with SPSS, the results demonstrated that there was no significant difference ( P > 0.1) and was in high similarity ( R > 0.7) between the data collected in simulations and physical experiments. The therapy system model of noninvasive Bi-PAP is probably applied for simulating the practical clinical experiment, and maybe conveniently applied to study the technology of noninvasive Bi-PAP for clinicians.

Injuria pulmonar autoinducida por el paciente / Patient self-inflicted lung injury

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)

Pulmonary complications and respiratory management in neurocritical care: a narrative review / 中华医学杂志(英文版)

Neurocritical care (NCC) is not only generally guided by principles of general intensive care, but also directed by specific goals and methods. This review summarizes the common pulmonary diseases and pathophysiology affecting NCC patients and the progress made in strategies of respiratory support in NCC. This review highlights the possible interactions and pathways that have been revealed between neurological injuries and respiratory diseases, including the catecholamine pathway, systemic inflammatory reactions, adrenergic hypersensitivity, and dopaminergic signaling. Pulmonary complications of neurocritical patients include pneumonia, neurological pulmonary edema, and respiratory distress. Specific aspects of respiratory management include prioritizing the protection of the brain, and the goal of respiratory management is to avoid inappropriate blood gas composition levels and intracranial hypertension. Compared with the traditional mode of protective mechanical ventilation with low tidal volume (Vt), high positive end-expiratory pressure (PEEP), and recruitment maneuvers, low PEEP might yield a potential benefit in closing and protecting the lung tissue. Multimodal neuromonitoring can ensure the safety of respiratory maneuvers in clinical and scientific practice. Future studies are required to develop guidelines for respiratory management in NCC.

Hiperinsuflação manual em crianças / Manual hyperinflation in children

RESUMO A hiperinsuflação manual é utilizada em unidades de terapia intensiva neonatal e pediátrica para promover um flow bias expiratório, porém não há consenso sobre os benefícios da técnica. Assim faz-se necessária uma revisão que apresente suas evidências. Este estudo objetiva revisar a literatura sobre a manobra de hiperinsuflação manual em unidades de terapia intensiva neonatal e pediátrica, para analisar as evidências dessa técnica em relação às formas de aplicação (associadas ou não a outras técnicas), sua segurança, o desempenho dos ressuscitadores manuais e a influência da experiência do fisioterapeuta, além de avaliar a qualidade metodológica dos artigos encontrados. Realizou-se uma busca nas bases de dados: Web of Science, ScienceDirect, PubMedⓇ, Scopus, CINAHL e SciELO. Dois pesquisadores selecionaram os artigos de forma independente. Verificaram-se os estudos duplicados, avaliados por títulos, resumos e, então, leitura na íntegra. Analisou-se a qualidade dos artigos pela escala PEDro. Foram incluídos seis artigos, sendo dois com alta qualidade metodológica. Os principais resultados trouxeram informações sobre a contribuição da válvula de pressão positiva expiratória final no aumento dos volumes pulmonares e a utilização das compressões torácicas para otimizar o flow bias expiratório, a influência negativa da experiência do operador no aumento do pico de fluxo inspiratório, o desempenho de diferentes ressuscitadores manuais durante a realização da técnica e a segurança na aplicação, com manutenção da estabilidade hemodinâmica e aumento da saturação periférica de oxigênio. Os estudos disponíveis apontam para um efeito positivo da manobra de hiperinsuflação manual realizada em crianças internadas em unidades de terapia intensiva. Registro PROSPERO: CRD42018108056.

ABSTRACT Manual hyperinflation is used in neonatal and pediatric intensive care units to promote expiratory flow bias, but there is no consensus on the benefits of the technique. Thus, a review that presents supporting evidence is necessary. This study aims to review the literature on the manual hyperinflation maneuver in neonatal and pediatric intensive care units to analyze the evidence for this technique in terms of the forms of application (associated with other techniques or not), its safety, the performance of manual resuscitators and the influence of the physical therapist's experience, in addition to evaluating the methodological quality of the identified articles. A search was performed in the following databases: Web of Science, ScienceDirect, PubMedⓇ, Scopus, CINAHL and SciELO. Two researchers independently selected the articles. Duplicate studies were assessed, evaluated by title and abstract and then read in full. The quality of the articles was analyzed using the PEDro scale. Six articles were included, two of which had high methodological quality. The main results provided information on the contribution of the positive end-expiratory pressure valve to increasing lung volumes and the use of chest compressions to optimize expiratory flow bias, the negative influence of operator experience on the increase in peak inspiratory flow, the performance of different manual resuscitators when used with the technique and the safety of application in terms of maintaining hemodynamic stability and increasing peripheral oxygen saturation. The available studies point to a positive effect of the manual hyperinflation maneuver in children who are admitted to intensive care units. Registration PROSPERO: CRD42018108056.

Repercussões da ventilação não invasiva em recém-nascidos prematuros com síndrome do desconforto respiratório agudo: revisão integrativa / Repercussionsof non-invasive ventilation in premature newborns with acute respiratory discomfort syndrome: integrative review / Repercusionesde la ventilación no invasiva en recién nacidos prematuros con síndrome de malestar respiratorio agudo: revisión integrativa

Introdução: Neonatos pré-termos apresentam singularidades anátomo-fisiológicas predispondo-os a complicações respiratórias como a Síndrome do Desconforto Respiratório Aguda. Caracterizada pelo déficit de surfactante pulmonar e consequente insuficiência respiratória, aumentando a necessidade de suporte ventilatório invasivo e não invasivo.Objetivo: Analisar os efeitos da ventilação não invasiva em recém-nascidos prematuros com Síndrome do Desconforto Respiratório Aguda. Metodologia: Trata-se de uma revisão integrativa no qual utilizou-se das bases de dados: SciELO, LILACS, PEDro, MEDLINE e Bireme. Os critérios de inclusão foram estudos relacionadosatemática em portuguêseinglês completos e com publicação entre 2015 a 2020.Resultados:Nos seteestudos sintetizados houve a utilização dos sistemas de suporte ventilatório: pressão positiva em vias aéreas a dois níveis: cânulas nasais aquecidas, umidificadas e de alto fluxo; ventilação de pressão positiva nas vias aéreas nasal, e a ventilação por pressão positiva intermitente nasal. Dois estudos que utilizaram cânulas nasais apontaram efeitos menos benéficos; e um relatou desfechos semelhantes aos demais, além de provocar menor dano nasal. Conclusões: Aventilação não invasiva tevegrande redução do número de falhas de extubação dos pacientes, principalmente naqueles que receberam a ventilação pressão positiva nas vias aéreas nasaise a ventilação por pressão positiva intermitente nasal (AU).

Introduction:Pre-term neonates have anatomophysiologicalsingularities predisposing them to respiratory complications such as Acute Respiratory Discomfort Syndrome. It is characterized by a deficit in pulmonary surfactant and consequent respiratory failure, increasing the need for invasive and non-invasive ventilatory support.Objective:To analyze the effects of non-invasive ventilation in premature newborns with Acute Respiratory Discomfort Syndrome. Methodology:In this integrative review, we used the following databases: SciELO, LILACS, PEDro, MEDLINE, and Bireme. Inclusion criteria were studies wrote in Portuguese and English and published between 2015 and 2020. Results:In the seven synthesized studies, ventilatory support systems were used: positive airway pressure at two levels: heated, humidified, and high-flow nasal cannulas; positive pressure ventilation in the nasal airways; and intermittent positive pressure ventilation. Two studies that used nasal cannulas showed less beneficial effects, and one reported similar outcome to the others, in addition to causing less nasal damage. Conclusions:Non-invasive ventilation had a significant reduction in the number of extubation failures in patients, especially in those who received positive pressure ventilation in the nasal airways and ventilation by positive intermittent nasal pressure (AU).

Introducción:Los neonatos pretérmino presentan singularidades anatomofisiológicasque predisponen a complicaciones respiratorias como el Síndrome de Malestar Respiratorio Agudo. Se caracteriza por un déficit de surfactante pulmonar y la consiguiente insuficiencia respiratoria, aumentando la necesidad de soporte ventilatorio invasivo y no invasivo. Objetivo:Analizar los efectos de la ventilación no invasiva en recién nacidos prematuros con Síndrome de Malestar Respiratorio Agudo. Metodología:En esta revisión integradora se utilizaron las siguientes bases de datos: SciELO, LILACS, PEDro, MEDLINE y Bireme. Los criterios de inclusión fueron estudios escritos en portugués y en inglés y publicados entre 2015 y 2020.Resultados:En los siete estudios sintetizados se utilizaron sistemas de soporte ventilatorio: presión positiva en la vía aéreaen dos niveles: cánulas nasales calentadas, humidificadas y de alto flujo; ventilación con presión positiva en la vía aérea nasal; y ventilación con presión positiva intermitente. Dos estudios que utilizaron cánulas nasales mostraron efectos menos beneficiosos, y uno informó de un resultado similar al de los otros, además de causar menos daño nasal. Conclusiones:La ventilación no invasiva tuvo una reducción significativa en el número de fracasos de extubación en los pacientes, especialmente en aquellos que recibieron ventilación con presión positiva en las vías aéreas nasales y ventilación por presión nasal positiva intermitente (AU).

Estimation of lung recruitment characteristics using the static pressure-volume curve of lungs / 生物医学工程学杂志

Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients' characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.

Association between ventilatory settings and pneumothorax in extremely preterm neonates

OBJECTIVES: Pneumothorax is a catastrophic event associated with high morbidity and mortality, and it is relatively common in neonates. This study aimed to investigate the association between ventilatory parameters and the risk of developing pneumothorax in extremely low birth weight neonates. METHODS: This single-center retrospective cohort study analyzed 257 extremely low birth weight neonates admitted to a neonatal intensive care unit between January 2012 and December 2017. A comparison was carried out to evaluate the highest value of positive end-expiratory pressure (PEEP), peak inspiratory pressure (PIP), and driving pressure (DP) in the first 7 days of life between neonates who developed pneumothorax and those who did not. The primary outcome was pneumothorax with chest drainage necessity in the first 7 days of life. A matched control group was created in order to adjust for cofounders associated with pneumothorax (CRIB II score, birth weight, and gestational age). RESULTS: There was no statistically significant difference in PEEP, PIP, and DP values in the first 7 days of life between extremely low birth weight neonates who had pneumothorax with chest drainage necessity and those who did not have pneumothorax, even after adjusting for potential cofounders. CONCLUSIONS: Pressure-related ventilatory settings in mechanically ventilated extremely low birth weight neonates are not associated with a higher risk of pneumothorax in the first 7 days of life.

Protective mechanical ventilation in patients with risk factors for ARDS: prospective cohort study / Ventilação mecânica protetora em pacientes com fator de risco para SDRA: estudo de coorte prospectiva

ABSTRACT Objective: To evaluate the association that protective mechanical ventilation (MV), based on VT and maximum distending pressure (MDP), has with mortality in patients at risk for ARDS. Methods: This was a prospective cohort study conducted in an ICU and including 116 patients on MV who had at least one risk factor for the development of ARDS. Ventilatory parameters were collected twice a day for seven days, and patients were divided into two groups (protective MV and nonprotective MV) based on the MDP (difference between maximum airway pressure and PEEP) or VT. The outcome measures were 28-day mortality, ICU mortality, and in-hospital mortality. The risk factors associated with the adoption of nonprotective MV were also assessed. Results: Nonprotective MV based on VT and MDP was applied in 49 (42.2%) and 38 (32.8%) of the patients, respectively. Multivariate Cox regression showed that protective MV based on MDP was associated with lower in-hospital mortality (hazard ratio = 0.37; 95% CI: 0.19-0.73) and lower ICU mortality (hazard ratio = 0.40; 95% CI: 0.19-0.85), after adjustment for age, Simplified Acute Physiology Score 3, and vasopressor use, as well as the baseline values for PaO2/FiO2 ratio, PEEP, pH, and PaCO2. These associations were not observed when nonprotective MV was based on the VT. Conclusions: The MDP seems to be a useful tool, better than VT, for adjusting MV in patients at risk for ARDS.

RESUMO Objetivo: Avaliar a associação da ventilação mecânica (VM) protetora, com base no VT e na pressão de distensão máxima (PDM), com a mortalidade em pacientes com fator de risco para SDRA. Métodos: Este estudo de coorte prospectivo foi conduzido em uma UTI e incluiu 116 pacientes em VM que apresentavam pelo menos um fator de risco para o desenvolvimento de SDRA. Os parâmetros ventilatórios foram coletados duas vezes ao dia durante sete dias, e os pacientes foram divididos em dois grupos (VM protetora e VM não protetora) com base na PDM (diferença entre pressão máxima de vias aéreas e PEEP) ou no VT. Os desfechos foram mortalidade em 28 dias, mortalidade na UTI e mortalidade hospitalar. Os fatores de risco associados com a adoção da VM não protetora também foram avaliados. Resultados: A VM não protetora com base no VT e na PDM ocorreu em 49 (42,2%) e em 38 (32,8%) dos pacientes, respectivamente. A regressão multivariada de Cox mostrou que a VM protetora com base na PDM associou-se a menor mortalidade hospitalar (hazard ratio = 0,37; IC95%: 0,19-0,73) e em UTI (hazard ratio = 0,40; IC95%, 0,19-0,85), após ajuste para idade, Simplified Acute Physiology Score 3, uso de vasopressor e valores basais de PaO2/FiO2, PEEP, pH e PaCO2. Essas associações não foram observadas quando a VM não protetora foi baseada no VT. Conclusões: A PDM parece ser uma ferramenta útil, melhor do que o VT, para o ajuste da VM em pacientes sob risco para SDRA.

Alveolar recruitment maneuvers for children with cancer and acute respiratory distress syndrome: a feasibility study / Manobras de recrutamento alveolar em crianças com câncer e síndrome do desconforto respiratório agudo: um estudo de viabilidade

ABSTRACT Objective: Acute respiratory distress syndrome (ARDS) can be a devastating condition in children with cancer and alveolar recruitment maneuvers (ARMs) can theoretically improve oxygenation and survival. The study aimed to assess the feasibility of ARMs in critically ill children with cancer and ARDS. Methods: We retrospectively analyzed 31 maneuvers in a series of 12 patients (median age of 8.9 years) with solid tumors (n=4), lymphomas (n=2), acute lymphoblastic leukemia (n=2), and acute myeloid leukemia (n=4). Patients received positive end-expiratory pressure from 25 up to 40 cmH20, with a delta pressure of 15 cmH2O for 60 seconds. We assessed blood gases pre- and post-maneuvers, as well as ventilation parameters, vital signs, hemoglobin, clinical signs of pulmonary bleeding, and radiological signs of barotrauma. Pre- and post-values were compared by the Wilcoxon test. Results: Median platelet count was 53,200/mm3. Post-maneuvers, mean arterial pressure decreased more than 20% in two patients, and four needed an increase in vasoactive drugs. Hemoglobin levels remained stable 24 hours after ARMs, and signs of pneumothorax, pneumomediastinum, or subcutaneous emphysema were absent. Fraction of inspired oxygen decreased significantly after ARMs (FiO2; p=0.003). Oxygen partial pressure (PaO2)/FiO2 ratio increased significantly (p=0.0002), and the oxygenation index was reduced (p=0.01), but all these improvements were transient. Recruited patients' 28-day mortality was 58%. Conclusions: ARMs, although feasible in the context of thrombocytopenia, lead only to transient improvements, and can cause significant hemodynamic instability.

RESUMO Objetivo: A síndrome do desconforto respiratório agudo (SDRA) pode ser uma condição devastadora em crianças com câncer e as manobras de recrutamento alveolar (MRA) podem melhorar a oxigenação e a sobrevida. O objetivo foi avaliar a viabilidade das MRA em crianças gravemente doentes com câncer e SDRA. Métodos: Analisamos retrospectivamente 31 manobras em 12 pacientes (idade mediana de 8,9 anos), com tumores sólidos (n=4), linfomas (n=2) e leucemias linfoide (n=2) e mieloide agudas (n=4). Os pacientes receberam pressão expiratória final positiva de 25 a 40 cmH20, com delta de pressão de 15 cmH2O por 60 segundos. Gasometrias foram analisadas pré e pós-manobras, bem como os parâmetros de ventilação, sinais vitais, hemoglobina, sinais clínicos de sangramento pulmonar e sinais radiológicos de barotrauma. Valores foram comparados com o teste de Wilcoxon. Resultados: A contagem mediana de plaquetas era de 53.200/mm3. Após as manobras, em dois pacientes, a pressão arterial média declinou mais de 20%, e quatro necessitaram de aumento de drogas vasoativas. A hemoglobina permaneceu estável 24 horas após a MRA, sem sinais de pneumotórax, pneumomediastino ou enfisema subcutâneo. Houve diminuição significativa nas frações inspiradas de oxigênio (FiO2; p=0,003). A relação pressão arterial de oxigênio (PaO2)/FiO2 aumentou (p=0,002), e o índice de oxigenação caiu (p=0,01), mas essas melhoras foram transitórias. A mortalidade em 28 dias foi de 58%. Conclusões: As MRA, embora viáveis no contexto da trombocitopenia, levam apenas a melhorias transitórias e podem causar instabilidade hemodinâmica significativa.

Relación de las medidas de mecánica ventilatoria y radiográficas con el tiempo de conexión a ventilación mecánica en pacientes COVID-19: un análisis preliminar / Relations of ventilatory mechanical and radiographic measures with the connection time to mechanical ventilation in patients COVID-19: a preliminary analysis

RESUMEN: Los pulmones son el sitio predominante en la infección por COVID-19. Esta puede conducir al síndrome distrés respiratorio agudo (SDRA). Frente a su sintomatología severa, la ventilación mecánica (VM), y sus valores de mecánica ventilatoria aparecen como una herramienta fundamental. Un complemento, para analizar el estado de avance de esta patología es la radiografía de tórax (RT), aunque en ocasiones esta depende de la experiencia del equipo de salud. Así el objetivo de esta investigación fue explorar la relación de las medidas de mecánica ventilatoria y radiográficas con el tiempo de conexión a VM en pacientes COVID-19. Estudio retrospectivo, que incluyó a 23 pacientes en VM. Se recolectó información de variables de mecánica ventilatoria; PEEP, presión plateau, presión de distensión y compliance estática. Desde la RT se midió, altura y ancho pulmonar, ángulo costodiafragmático y espacio intercostal. Los resultados indicaron que las variables de mecánica ventilatoria tales como el PEEP y el plateau se relacionaron significativamente con el tiempo de conexión a VM (r=0,449; p=0,035 y r=0,472; p=0,026), mientras que las variables radiográficas construidas en base al ángulo costodiafragmático y el espacio intercostal presentaron similares comportamientos (r= 0,462; p=0,046 y r=-0,543; p=0,009). En conclusión, la presión resultante de la programación del ventilador mecánico junto a cambios estructurales observados en la RT, se relacionan con el tiempo de conexión a VM.

SUMMARY: The lungs are the predominant site of COVID-19 infection. This can lead to severe acute respiratory síndrome (ARDS). In view of its severe symptoms, mechanical ventilation (MV) and its ventilatory mechanics values appear as a fundamental tool. Chest radiography (CR) is a complement to analyze the state of progress of this pathology, although this sometimes depends on the experience of the health team. Thus, the aim of this research was to explore the relationship of ventilatory mechanics and radiographic measures with connection time to MV in COVID-19 patients. Retrospective study, which included 23 patients on MV. Information on ventilatory mechanics variables was collected; PEEP, plateau pressure, distension pressure and static compliance. And from CR, lung height and width, costodiaphragmatic angle and intercostal space were measured. The results indicated that ventilatory mechanics variables such as PEEP and plateau were significantly related to connection time to MV (r = 0.449; p = 0.035 and r = 0.472; p = 0.026), while the radiographic variables Constructed on the basis of the costodiaphragmatic angle and the intercostal space, they showed similar behaviors (r = 0.462; p = 0.046 and r = -0.543; p = 0.009). In conclusion, the pressure resulting from mechanical ventilator programming, together with the structural changes observed in CR, are related to the connection time to MV.

O comportamento da pressão arterial após elevação da pressão parcial positiva final pode auxiliar na determinação do status de fluido-responsividade em pacientes com choque séptico? / Can the behavior of blood pressure after elevation of the positive end-expiratory pressure help to determine the fluid responsiveness status in patients with septic shock?

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.

Características y resultados de los pacientes infectados con nCoV19 con requerimiento de ventilación mecánica invasiva en la Argentina / Characteristics and outcomes of patients infected with nCoV19 requiring invasive mechanical ventilation in Argentina

RESUMEN Objetivo: El coronavirus ha emergido este año como causa de neumonía viral. Una de las principales características es su rápida transmisión y su potencial severidad. El objetivo de este estudio de serie de casos es describir las características clínicas de los pacientes con confirmación de enfermedad por coronavirus (COVID-19) admitidos en diferentes unidades de cuidados intensivos de la Argentina con requerimiento de ventilación mecánica. Métodos: Estudio de serie de casos, descriptivo-prospectivo, multicéntrico realizado entre el 01 de abril y el 08 de mayo de 2020. Se incluyeron los datos de los pacientes mayores a 18 años, que ingresaron a la unidad de cuidados intensivos con requerimiento de ventilación mecánica por falla respiratoria aguda con diagnóstico positivo de COVID-19 Resultados: Se registraron las variables de 47 pacientes de 31 unidades cuidados intensivos, 78.7% hombres de una mediana de edad de 61 años, con un SAPS II de 43, un índice de Charlson de 3. El modo ventilatorio inicial fue volume control - continuous mandatory ventilation con volumen corriente menor a 8mL/kg en el 100% de los casos, con una mediana de presión positiva al final de la espiración de 10,5cmH2O. A la fecha de cierre del estudio, 29 pacientes fallecieron, 8 alcanzaron el alta, y 10 pacientes continúan internados al cierre del estudio. El SAPS II fue mayor entre los fallecidos (p = 0.046). El índice de Charlson se asoció con mayor mortalidad (OR = 2,27 IC95% 1,13 - 4,55; p = 0,02). Conclusión: Los pacientes con COVID-19 y ventilación mecánica de esta serie presentan variables clínicas similares a las descriptas a la fecha en otros reportes internacionales. Nuestros hallazgos proporcionan datos que permitirían de alguna manera predecir los resultados.

Abstract Objective: A novel coronavirus emerged this year as a cause of viral pneumonia. The main characteristics of the virus are rapid transmission, high contagion capacity and potential severity. The objective of this case series study is to describe the clinical characteristics of patients with confirmed coronavirus disease (COVID-19) admitted to different intensive care units in Argentina for mechanical ventilation. Methods: A descriptive, prospective, multicenter case series study was conducted between April 1 and May 8, 2020. Data from patients older than 18 years who were admitted to the intensive care unit for mechanical ventilation for acute respiratory failure with a positive diagnosis of COVID-19 were included. Results: The variables for 47 patients from 31 intensive care units were recorded: 78.7% were men (median age of 61 years), with a SAPS II score of 43 and a Charlson index score of 3. The initial ventilatory mode was volume control - continuous mandatory ventilation with a tidal volume less than 8mL/kg in 100% of cases, with a median positive end-expiratory pressure of 10.5cmH2O. At the end of the study, 29 patients died, 8 were discharged, and 10 remained hospitalized. The SAPS II score was higher among patients who died (p = 0.046). Charlson comorbidity index was associated with higher mortality (OR = 2.27, 95% CI 1.13 - 4.55, p = 0.02). Conclusion: Patients with COVID-19 and on mechanical ventilation in this series presented clinical variables similar to those described to date in other international reports. Our findings provide data that may predict outcomes.

Ventilación mecánica simultánea con un solo ventilador a varios pacientes / Simultaneous mechanical ventilation of several patients with a single ventilator

Resumen Introducción: La ventilación mecánica simultánea a varios pacientes con un solo ventilador podría disminuir el déficit de esos dispositivos para atender a los enfermos con insuficiencia respiratoria aguda por Covid-19. Objetivo: Comunicar los resultados de un ejercicio de ventilación mecánica con un ventilador en un simulador de pulmón, y simultáneamente en dos y cuatro simuladores. Resultados: No se observaron diferencias estadísticamente significativas entre la presión positiva al final de la espiración, presión media de la vía aérea y presión pico programadas, registradas y medidas, excepto al ventilar simultáneamente cuatro simuladores de pulmón. Conclusiones: La ventilación mecánica simultánea debe ser instaurada por personal médico con experiencia en el procedimiento, restringirse a dos pacientes y ser realizada en la unidad de cuidados intensivos.

Abstract Introduction: Simultaneous mechanical ventilation of several patients with a single ventilator might reduce the deficit of these devices for the care of patients with acute respiratory failure due to Covid-19. Objective: To communicate the results of a mechanical ventilation exercise with a ventilator in a lung simulator, and simultaneously in two and four. Results: No statistically significant differences were observed between positive end-expiratory pressure, mean airway pressure, and programmed, recorded and measured peak pressure, except when simultaneously ventilating four lung simulators. Conclusions: Simultaneous mechanical ventilation should be implemented by medical personnel with experience in the procedure, be restricted to two patients and carried out in the intensive care unit.

Historia de la ventilación mecánica. De la Antigüedad a Copenhague 1952 / The history of mechanical ventilation

The aim of mechanical ventilation is to substitute physiological respiratory function. The boom of mechanical ventilation came during the XVIII century with the development of Reanimation Societies in Europe, who promoted the use of positive pressure ventilation modes. This type of ventilation caused new complications due to excessive positive pressure in the airway. Therefore, during the XIX century negative pressure ventilation predominated, which became essential during the second half of the 19th century and first half of the 20th century. Positive pressure ventilation was relegated to operating rooms until 1952, when it was imposed over negative pressure ventilation during the Copenhagen polio epidemic. Björn Ibsen contributed significantly to this change of ventilation paradigm, which led to the latest ventilation strategies and the development of the actual intensive care units.

Parâmetros hemodinâmicos e ventilatórios em coelhos anestesiados com isoflurano, submetidos à ventilação controlada à pressão com ou sem PEEP / Hemodynamic and ventilatory parameters in rabbits anesthetized with isoflurane submitted to pressure controlled ventilation with or without PEEP

Foi comparada a ventilação controlada à pressão com ou sem pressão positiva expiratória final (PEEP), em coelhos, distribuídos em três grupos, denominados GP (grupo ventilação ciclada à pressão), GPP (grupo ventilação ciclada à pressão com PEEP) e GE (grupo ventilação espontânea - grupo controle). Os animais foram anestesiados com isoflurano, em circuito com reinalação de gases, durante duas horas. As médias de pressão arterial média (PAM) e pressão arterial sistólica (PAS) permaneceram discretamente abaixo dos valores normais em todos os grupos. Houve diminuição significativa da PAM e da PAS no grupo submetido à PEEP (GPP) ao longo do tempo. A pressão parcial de dióxido de carbono arterial (PaCO2) foi maior no GPP quando comparado aos outros grupos no último momento, gerando acidemia respiratória após uma hora de procedimento. A concentração de dióxido de carbono ao final da expiração (ETCO2) apresentou médias discretamente elevadas no grupo não tratado com PEEP (GP) e no grupo controle, enquanto o GPP apresentou maiores médias, possivelmente, relacionadas à diminuição do volume corrente neste grupo. Com base nesses resultados, foi possível concluir que a utilização da PEEP levou à acidemia, que se agravou ao longo do tempo anestésico. Ademais, a anestesia prolongada com isoflurano promove depressão cardiorrespiratória, independentemente do modo ventilatório empregado.(AU)

Pressure controlled ventilation with or without positive end-expiratory pressure (PEEP) was compared in rabbits, which were divided into three groups denominated GP (pressure cycled ventilation group), GPP (pressure cycled ventilation with PEEP group) and GE (spontaneous ventilation group - control group). The animals were anesthetized with isoflurane in a gas rebreathing circuit for two hours. The means of mean arterial pressure (MAP) and systolic blood pressure (SBP) remained slightly below normal values ​​in all groups. There was a significant decrease in MAP and SBP in the group submitted to PEEP (GPP) over time. The partial pressure of arterial carbon dioxide (PaCO2) was higher in GPP when compared to the other groups, inducing respiratory acidosis after one hour. The end-expired carbon dioxide concentration (ETCO2) presented slightly elevated means in the GP, while the GPP presented higher means, possibly related to the decrease in tidal volume in this group. Based on these results it was concluded that the use of PEEP led to acidemia that worsened over anesthetic time. In addition, prolonged isoflurane anesthesia promotes cardiorespiratory depression, regardless the ventilatory mode employed.(AU)