Abstract Background: Coronavirus disease 2019 (COVID-19) has spread fast globally comprising a great variety of clinical presentations. It was reported that 15% of patients required admission to intensive care units (ICU). Previous epidemiological studies have reported higher risk of healthcare-associated infections (HCAI) in those patients requiring invasive mechanical ventilation (iMV) due to COVID-19. Aim: To analyze the incidence of HCAI in adults under iMV admitted to ICU of Anchorena San Martín Clinic during COVID-19 pandemic. Methods: Retrospective cohort study, the analysis of normality was carried out using the Shapiro-Wilk test. The multiple regression analysis was performed automatically, based on backward elimination of the variables (backward selection). For the comparison between the COVID-19 and non-COVID-19 groups, the T test or Wilcoxon test was used, as appropriate; and the χ2 or Fisher's exact test. All cumulative incidence function estimates were made with the cmprsk package. Results: 252 patients were included, 40 patients developed HCAI (accumulated incidence was 15.9%), counting for 60 total HCAI events. Age (OR 0.96), number of central venous access devices (CVAD) (OR 2.01), COVID-19 (OR 2.96) and prone positioning (OR 2.78) were associated with HCAI. HCAI was associated with more days of iMV and ICU stay. The accumulated incidence of HCAI in non-COVID-19 patients was lower than in COVID-19 patients. iMV days and mortality were higher in COVID-19. 29.6% of COVID-19 patients developed HCAIs vs 7.1% of non-COVID-19 ones. Conclusión: We describe the incidence of HCAI. Age, COVID-19, CVAD, prone positioning and ICU stay were associated with higher probability of HCAIs.

Resumen Introducción: La pandemia por coronavirus se diseminó mundialmente con una amplia variedad de presentaciones clínicas. Se reportó que 15% de los pacientes requirió internación en una unidad de cuidados intensivos (UCI). Estudios epidemiológicos demostraron que pacientes con ventilación mecánica invasiva (VMi) por SARS-Cov-2 presentan más riesgo de infecciones asociadas a la atención de la salud (IAAS). Objetivo: Describir la incidencia IAAS en adultos internados en UCI en VMi del Sanatorio Anchorena San Martín, durante la pandemia en 2020. Pacientes y Métodos: Estudio de cohorte retrospectivo, el análisis de normalidad se efectuó mediante test Shapiro-Wilk. El análisis de regresión múltiple se realizó en forma automática, (backward selection). Para la comparación entre grupo COVID-19 y no COVID-19 se utilizó T test o Test de Wilcoxon según correspondiera; y el χ2 o el test exacto de Fisher. Todas las estimaciones de las funciones de incidencia acumuladas fueron realizadas con el paquete cmprsk. Resultados: Se incluyeron 252 pacientes, 40 desarrollaron IAAS (incidencia acumulada de 15,9%), con un total de 60 eventos de IAAS. La edad (OR 0,96), cantidad de accesos venosos centrales (AVC) (OR 2,01), COVID-19 (OR 2,96) y decúbito prono (OR 2,78) se asociaron a IAAS. Desarrollar IAAS se asoció a más días de VMi y estadía en UCI. La incidencia acumulada de IAAS en pacientes NO COVID fue menor que en COVID-19. Días de VMi y mortalidad en UCI fueron mayores en pacientes con COVID. El 29,6% de los pacientes con COVID-19 desarrolló algún tipo de IAAS vs 7,1% en NO COVID. Conclusión: Describimos la incidencia de IAAS en nuestra cohorte. La presencia de COVID-19, AVC, el decúbito prono y estadía en UCI se asociaron con mayor probabilidad de contraer una IAAS.

ABSTRACT Objective: To compare gas exchange indices behavior by using liberal versus conservative oxygenation targets in patients with moderate to severe acute respiratory distress syndrome secondary to COVID-19 under invasive mechanical ventilation. We also assessed the influence of high FiO2 on respiratory system mechanics. Methods: We prospectively included consecutive patients aged over 18 years old with a diagnosis of COVID-19 and moderate-severe acute respiratory distress syndrome. For each patient, we randomly applied two FiO2 protocols to achieve SpO2 88% - 92% or 96%. We assessed oxygenation indices and respiratory system mechanics. Results: We enrolled 15 patients. All the oxygenation indices were significantly affected by the FiO2 strategy (p < 0.05) selected. The PaO2/FiO2 deteriorated, PA-aO2 increased and Pa/AO2 decreased significantly when using FiO2 to achieve SpO2 96%. Conversely, the functional shunt fraction was reduced. Respiratory mechanics were not affected by the FiO2 strategy. Conclusion: A strategy aimed at liberal oxygenation targets significantly deteriorated gas exchange indices, except for functional shunt, in COVID-19-related acute respiratory distress syndrome. The respiratory system mechanics were not altered by the FiO2 strategy. Clinical Trials Register: NCT04486729.

RESUMO Objetivo: Comparar o comportamento dos índices de troca gasosa conforme o uso de alvos de oxigenação liberais em comparação a conservadores em pacientes com síndrome do desconforto respiratório agudo moderada a grave secundária à COVID-19 e em uso de ventilação mecânica; avaliar a influência da FiO2 elevada na mecânica do sistema respiratório. Métodos: Foram incluídos prospectivamente pacientes consecutivos com idades acima de 18 anos, diagnóstico de COVID-19 e síndrome do desconforto respiratório agudo moderada e grave. Para cada paciente, aplicou-se aleatoriamente dois protocolos de FiO2 para obter SpO2 de 88% a 92% ou 96%. Avaliaram-se os índices de oxigenação e a mecânica do sistema respiratório. Resultados: Foram incluídos 15 pacientes. Todos seus índices foram significantemente afetados pela estratégia de FiO2 (p < 0,05). A proporção PaO2/FiO2 deteriorou, o PA-aO2 aumentou e o Pa/AO2 diminuiu significantemente com a utilização de FiO2 para obter SpO2 96%. Opostamente, a fração de shunt funcional foi reduzida. A mecânica respiratória não foi afetada pela estratégia de FiO2. Conclusão: Uma estratégia com alvos liberais de oxigenação deteriorou significantemente os índices de troca gasosa, com exceção do shunt funcional, em pacientes com síndrome do desconforto respiratório agudo relacionada à COVID-19. A mecânica do sistema respiratório não foi alterada pela estratégia de FiO2. Registro Clinical Trials: NCT04486729.

RESUMO A respiração espontânea pode ser prejudicial para pacientes com pulmões previamente lesados, especialmente na vigência de síndrome do desconforto respiratório agudo. Mais ainda, a incapacidade de assumir a respiração totalmente espontânea durante a ventilação mecânica e a necessidade de voltar à ventilação mecânica controlada se associam com mortalidade mais alta. Existe uma lacuna no conhecimento em relação aos parâmetros que poderiam ser úteis para predizer o risco de lesão pulmonar autoinflingida pelo paciente e detecção da incapacidade de assumir a respiração espontânea. Relata-se o caso de um paciente com lesão pulmonar autoinflingida e as correspondentes variáveis, básicas e avançadas, de monitoramento da mecânica do sistema respiratório, além dos resultados fisiológicos e clínicos relacionados à respiração espontânea durante ventilação mecânica. O paciente era um homem caucasiano com 33 anos de idade e história clínica de AIDS, que apresentou síndrome do desconforto respiratório agudo e necessitou ser submetido à ventilação mecânica invasiva após falha do suporte ventilatório não invasivo. Durante os períodos de ventilação controlada, adotou-se estratégia de ventilação protetora, e o paciente mostrou evidente melhora, tanto do ponto de vista clínico quanto radiográfico. Contudo, durante cada período de respiração espontânea sob ventilação com pressão de suporte, apesar dos parâmetros iniciais adequados, das regulagens rigorosamente estabelecidas e do estrito monitoramento, o paciente desenvolveu hipoxemia progressiva e piora da mecânica do sistema respiratório, com deterioração radiográfica claramente correlacionada (lesão pulmonar autoinflingida pelo paciente). Após falha de três tentativas de respiração espontânea, o paciente faleceu por hipoxemia refratária no 29° dia. Neste caso, as variáveis básicas e avançadas convencionais não foram suficientes para identificar a aptidão para respirar espontaneamente ou predizer o risco de desenvolver lesão pulmonar autoinflingida pelo paciente durante a ventilação de suporte parcial.

ABSTRACT Spontaneous breathing can be deleterious in patients with previously injured lungs, especially in acute respiratory distress syndrome. Moreover, the failure to assume spontaneous breathing during mechanical ventilation and the need to switch back to controlled mechanical ventilation are associated with higher mortality. There is a gap of knowledge regarding which parameters might be useful to predict the risk of patient self-inflicted lung injury and to detect the inability to assume spontaneous breathing. We report a case of patient self-inflicted lung injury, the corresponding basic and advanced monitoring of the respiratory system mechanics and physiological and clinical results related to spontaneous breathing. The patient was a 33-year-old Caucasian man with a medical history of AIDS who developed acute respiratory distress syndrome and needed invasive mechanical ventilation after noninvasive ventilatory support failure. During the controlled ventilation periods, a protective ventilation strategy was adopted, and the patient showed clear clinical and radiographic improvement. However, during each spontaneous breathing period under pressure support ventilation, despite adequate initial parameters and a strictly adjusted ventilatory setting and monitoring, the patient developed progressive hypoxemia and worsening of respiratory system mechanics with a clearly correlated radiographic deterioration (patient self-inflicted lung injury). After failing three spontaneous breathing assumption trials, he died on day 29 due to refractory hypoxemia. Conventional basic and advanced monitoring variables in this case were not sufficient to identify the aptitude to breathe spontaneously or to predict the risk and development of patient self-inflicted lung injury during partial support ventilation.

ABSTRACT Objective: To identify common practices related to the use and titration of pressure-support ventilation (PC-CSV - pressure control-continuous spontaneous ventilation) in patients under mechanical ventilation and to analyze diagnostic criteria for over-assistance and under-assistance. The secondary objective was to compare the responses provided by physician, physiotherapists and nurses related to diagnostic criteria for over-assistance and under-assistance. Methods: An online survey was conducted using the Survey Monkey tool. Physicians, nurses and physiotherapists from Argentina with access to PC-CSV in their usual clinical practice were included. Results: A total of 509 surveys were collected from October to December 2018. Of these, 74.1% were completed by physiotherapists. A total of 77.6% reported using PC-CSV to initiate the partial ventilatory support phase, and 43.8% of respondents select inspiratory pressure support level based on tidal volume. The main objective for selecting positive end-expiratory pressure (PEEP) level was to decrease the work of breathing. High tidal volume was the primary variable for detecting over-assistance, while the use of accessory respiratory muscles was the most commonly chosen for under-assistance. Discrepancies were observed between physicians and physiotherapists in relation to the diagnostic criteria for over-assistance. Conclusion: The most commonly used mode to initiate the partial ventilatory support phase was PC-CSV. The most frequently selected variable to guide the titration of inspiratory pressure support level was tidal volume, and the main objective of PEEP was to decrease the work of breathing. Over-assistance was detected primarily by high tidal volume, while under-assistance by accessory respiratory muscles activation. Discrepancies were observed among professions in relation to the diagnostic criteria for over-assistance, but not for under-assistance.

RESUMEN Objetivo: Identificar las prácticas habituales de uso y titulación del modo presión soporte (PC-CSV - pressure control continuous spontaneous ventilation) en pacientes bajo ventilación mecánica y analizar las formas de reconocimiento de sobreasistencia y subasistencia. Secundariamente, comparar las respuestas según profesión en relación al diagnóstico de sobreasistencia y subasistencia. Métodos: Se realizó una encuesta online utilizando la herramienta Survey Monkey. Se incluyeron a médicos, enfermeros y kinesiólogos de Argentina que tuvieran acceso al uso de PC-CSV en su práctica habitual. Resultados: Se recolectaron 509 encuestas desde octubre a diciembre 2018. El 74,1% de ellas correspondió a kinesiólogos. Un 77,6% refirió utilizar PC-CSV para iniciar la fase de soporte parcial. Un 43,8% selecciona el valor de presión de soporte inspiratorio basándose en volumen corriente. El principal objetivo de la selección de PEEP fue disminuir el trabajo respiratorio. El volumen corriente alto fue la variable primordial de detección de sobreasistencia, mientras que el uso de músculos accesorios fue la más elegida para subasistencia. Se observaron diferencias entre médicos y kinesiólogos en relación a las formas de detección de sobreasistencia. Conclusión: El modo más utilizado para la fase de soporte parcial es PC-CSV. La variable más elegida para titular la presión de soporte inspiratorio es volumen corriente y el principal objetivo de la PEEP es disminuir el trabajo respiratorio. La sobreasistencia es detectada prioritariamente por un volumen corriente elevado, mientras que la subasistencia mediante el uso de músculos accesorios. Se halló diferencias entre profesiones en relación a los criterios de detección de sobreasistencia.

ABSTRACT The respiratory system mechanics depend on the characteristics of the lung and chest wall and their interaction. In patients with acute respiratory distress syndrome under mechanical ventilation, the monitoring of airway plateau pressure is fundamental given its prognostic value and its capacity to assess pulmonary stress. However, its validity can be affected by changes in mechanical characteristics of the chest wall, and it provides no data to correctly titrate positive end-expiratory pressure by restoring lung volume. The chest wall effect on respiratory mechanics in acute respiratory distress syndrome has not been completely described, and it has likely been overestimated, which may lead to erroneous decision making. The load imposed by the chest wall is negligible when the respiratory system is insufflated with positive end-expiratory pressure. Under dynamic conditions, moving this structure demands a pressure change whose magnitude is related to its mechanical characteristics, and this load remains constant regardless of the volume from which it is insufflated. Thus, changes in airway pressure reflect changes in the lung mechanical conditions. Advanced monitoring could be reserved for patients with increased intra-abdominal pressure in whom a protective mechanical ventilation strategy cannot be implemented. The estimates of alveolar recruitment based on respiratory system mechanics could reflect differences in chest wall response to insufflation and not actual alveolar recruitment.

RESUMEN La mecánica del sistema respiratorio depende de las características del pulmón, la caja torácica y su interacción. En pacientes con síndrome de distrés respiratorio agudo bajo ventilación mecánica el monitoreo de la presión meseta en la vía aérea es fundamental debido a su valor pronóstico y su capacidad de reflejar el estrés pulmonar. Sin embargo, su validez puede verse afectada por cambios en las características mecánicas de la caja torácica, y además, no otorga información para la correcta titulación de presión positiva al final de la espiración en función de restablecer el volumen pulmonar. La influencia que la caja torácica ejerce sobre la mecánica del sistema respiratorio en síndrome de distrés respiratorio agudo no ha sido completamente descripta y es probable que haya sido sobredimensionada pudiendo conducir a toma de decisiones erróneas. Ante la insuflación con presión positiva al final de la espiración, la carga impuesta por la caja torácica es despreciable. En condiciones dinámicas, desplazar esta estructura demanda un cambio de presión cuya magnitud se relaciona con sus características mecánicas, dicha carga se mantiene constante independientemente del volumen a partir del cual es insuflada. Por lo que cambios en la presión en la vía aérea reflejan modificaciones en las condiciones mecánicas del pulmón. El monitoreo avanzado podría reservarse para pacientes con incremento de la presión intra-abdominal en los que no pueda implementarse una estrategia de ventilación mecánica protectora. Las estimaciones de reclutamiento alveolar basadas en la mecánica del sistema respiratorio podrían ser reflejo del diferente comportamiento de la caja torácica a la insuflación y no verdadero reclutamiento alveolar.