Síndrome de distrés respiratorio agudo en la pos-pandemia: una nueva definición global con extensión a regiones de menos recursos / Post-Pandemic Acute Respiratory Distress Syndrome: A New Global Definition with Extension to Lower-Resource Regions

El síndrome de dificultad respiratoria aguda (SDRA), inicialmente descrito en 1967, se caracteriza por insuficiencia respiratoria aguda con hipoxemia profunda, disminución de la distensibilidad pulmonar e infiltrados bilaterales en la Rx de tórax. En 2012 la definición de Berlín estableció tres categorías con base en la hipoxemia (SDRA leve, moderado y grave), precisando aspectos temporales y permitiendo el diagnóstico con ventilación no invasiva. La pandemia de COVID-19 llevó a reconsiderar la definición, enfocándose en el monitoreo continuo de la oxigenación y la oxigenoterapia de alto flujo. En 2021 se propuso una nueva definición global de SDRA, basada en la definición de Berlín, pero incluyendo una categoría para pacientes no intubados, permitiendo el uso de saturación periférica de oxígeno medida con oximetría de pulso/fracción inspirada de oxígeno (SpO2/FiO2) y la ecografía pulmonar para el diagnóstico, y sin ningún requerimiento de soporte especial de la oxigenación en regiones con recursos limitados. Aunque persisten debates, la evolución continua busca adaptarse a las necesidades clínicas y epidemiológicas, y personalizar tratamientos. (AU)

Acute respiratory distress syndrome (ARDS), first described in 1967, is characterized by acute respiratory failure causing profound hypoxemia, decreased pulmonary compliance, and bilateral CXR infiltrates. After several descriptions, the Berlin definition was adopted in 2012, which established three categories of severity according to hypoxemia (mild, moderate and severe), specified temporal aspects for diagnosis, and incorporated the use of non-invasive ventilation. The COVID-19 pandemic led to changes in ARDS management, focusing on continuous monitoring of oxygenation and on utilization of high-flow oxygen therapy and lung ultrasound. In 2021, a New Global Definition based on the Berlin definition of ARDS was proposed, which included a category for non-intubated patients, considered the use of SpO2, and established no particular requirement for oxygenation support in regions with limited resources. Although debates persist, the continuous evolution seeks to adapt to clinical and epidemiological needs, and to the search of personalized treatments. (AU)

Post-pandemic acute respiratory distress syndrome: A New Global Definition with extension to lower-resource regions.

Acute respiratory distress syndrome (ARDS), first described in 1967, is characterized by acute respiratory failure causing profound hypoxemia, decreased pulmonary compliance, and bilateral CXR infiltrates. After several descriptions, the Berlin definition was adopted in 2012, which established three categories of severity according to hypoxemia (mild, moderate and severe), specified temporal aspects for diagnosis, and incorporated the use of non-invasive ventilation. The COVID-19 pandemic led to changes in ARDS management, focusing on continuous monitoring of oxygenation and on utilization of high-flow oxygen therapy and lung ultrasound. In 2021, a New Global Definition based on the Berlin definition of ARDS was proposed, which included a category for non-intubated patients, considered the use of SpO2, and established no particular requirement for oxygenation support in regions with limited resources. Although debates persist, the continuous evolution seeks to adapt to clinical and epidemiological needs, and to the search of personalized treatments.

Airway and Transpulmonary Driving Pressure by End-Inspiratory Holds During Pressure Support Ventilation.

BACKGROUND: The precision of quasi-static airway driving pressure (ΔP) assessed in pressure support ventilation (PSV) as a surrogate of tidal lung stress is debatable because persistent muscular activity frequently alters the readability of end-inspiratory holds. In this study, we used strict criteria to discard excessive muscular activity during holds and assessed the accuracy of ΔP in predicting global lung stress in PSV. Additionally, we explored whether the physiological effects of high PEEP differed according to the response of respiratory system compliance (CRS). METHODS: Adults with ARDS undergoing PSV were enrolled. An esophageal catheter was inserted to calculate lung stress through transpulmonary driving pressure (ΔPL). ΔP and ΔPL were assessed in PSV at PEEP 5, 10, and 15 cm H2O by end-inspiratory holds. CRS was calculated as tidal volume (VT)/ΔP. We analyzed the effects of high PEEP on pressure-time product per minute (PTPmin), airway pressure at 100 ms (P0.1), and VT over PTP per breath (VT/PTPbr) in subjects with increased versus decreased CRS at high PEEP. RESULTS: Eighteen subjects and 162 end-inspiratory holds were analyzed; 51/162 (31.5%) of the holds had ΔPL ≥ 12 cm H2O. Significant association between ΔP and ΔPL was found at all PEEP levels (P < .001). ΔP had excellent precision to predict ΔPL, with 15 cm H2O being identified as the best threshold for detecting ΔPL ≥ 12 cm H2O (area under the receiver operating characteristics 0.99 [95% CI 0.98-1.00]). CRS changes from low to high PEEP corresponded well with lung compliance changes (R2 0.91, P < .001) When CRS increased, a significant improvement of PTPmin and VT/PTPbr was found, without changes in P0.1. No benefits were observed when CRS decreased. CONCLUSIONS: In subjects with ARDS undergoing PSV, high ΔP assessed by readable end-inspiratory holds accurately detected potentially dangerous thresholds of ΔPL. Using ΔP to assess changes in CRS induced by PEEP during assisted ventilation may inform whether higher PEEP could be beneficial.

Behavior of Endotracheal Tube Cuff Pressure During a Routine Control Maneuver With Different Manometers.

BACKGROUND: The main functions of the endotracheal tube (ETT) cuff are to prevent aspiration and to allow pressurization of the respiratory system. For this purpose, it is essential to maintain adequate pressure inside the cuff, thus reducing the risks for the patient. It is regularly checked using a manometer and is considered the best alternative. The objective of this study was to evaluate the cuff pressure behavior of different ETTs during the simulation of an inflation maneuver using different manometers. METHODS: A bench study was performed. Four brands of 8-mm internal diameter single lumen with a Murphy eye ETT with cuff and 3 different brands of manometers were used. In addition, a pulmonary mechanics monitor was connected to the inside of the cuff through the body of the distal end of the ETT. RESULTS: A total of 528 measurements were made on the 4 ETTs. During the complete procedure (connection and disconnection), there was a significant pressure drop of 7 ± 1.4 cm H2O from the initial pressure (Pinitial) (P < .001), of which 6 ± 1.4 cm H2O was lost during connection (difference between Pinitial and Pconnection). The Preconnection value was 19.1 ± 1.6 cm H2O, showing a significant total pressure drop of 11 ± 1.6 cm H2O (difference between Pinitial and Preconnection) (P < .001). The Pfinal mean was 29.6 ± 1.3 cm H2O. Significant differences were found between manometers according to the time of measurement. A similar phenomenon was evidenced when analyzing different ETTs. CONCLUSIONS: Significant pressure changes occur secondary to ETT cuff measurement, which has important implications for patient safety.

Epidemiology of Weaning From Invasive Mechanical Ventilation in Subjects With COVID-19.

BACKGROUND: Patients requiring mechanical ventilation due to COVID-19 have different characteristics of evolution and outcome compared to the general ICU population. Although early weaning from mechanical ventilation is associated with improved outcomes, inadequate identification of patients unable to be weaned may lead to extubation failure and increased days on mechanical ventilation. Outcomes related to mechanical ventilation weaning in this population are scare and inconclusive. Therefore, the objective of this study was to describe the characteristics of mechanical ventilation weaning in subjects with acute respiratory failure induced by COVID-19. METHODS: This was a multi-center, prospective cohort study. We included adult subjects requiring at least 12 h of mechanical ventilation due to COVID-19 infection admitted to any participating ICUs. Characteristics of the mechanical ventilation weaning and extubation process, as well as clinical results, were the primary outcome variables. Weaning types were defined according to previously described and internationally recognized categories. RESULTS: Three hundred twenty-six subjects from 8 ICUs were included. A spontaneous breathing trial (SBT) was not performed in 52.1% of subjects. One hundred twenty-eight subjects were extubated, and 29.7% required re-intubation. All the subjects included could be classified by Weaning according to a New Definition (WIND) classification (group 0 = 52.1%, group 1 = 28.5%, group 2 = 8.0%, and group 3 = 11.3%) with statistically significant differences in duration of mechanical ventilation (P < .001) and ICU length of stay (P < .001) between groups. CONCLUSIONS: The mechanical ventilation weaning process in subjects with COVID-19 was negatively affected by the disease, with many subjects never completing an SBT. Even though temporal variables were modified, the clinical outcomes in each weaning group were similar to those previously reported.

Ventilatory Parameters in Obstetric Patients With COVID-19 and Impact of Delivery: A Multicenter Prospective Cohort Study.

BACKGROUND: Current evidence on obstetric patients requiring advanced ventilatory support and impact of delivery on ventilatory parameters is retrospective, scarce, and controversial. RESEARCH QUESTION: What are the ventilatory parameters for obstetric patients with COVID-19 and how does delivery impact them? What are the risk factors for invasive mechanical ventilation (IMV) and for maternal, fetal, and neonatal mortality? STUDY DESIGN AND METHODS: Prospective, multicenter, cohort study including pregnant and postpartum patients with COVID-19 requiring advanced ventilatory support in the ICU. RESULTS: Ninety-one patients were admitted to 21 ICUs at 29.2 ± 4.9 weeks; 63 patients (69%) delivered in ICU. Maximal ventilatory support was as follows: IMV, 69 patients (76%); high-flow nasal cannula, 20 patients (22%); and noninvasive mechanical ventilation, 2 patients (2%). Sequential Organ Failure Assessment during the first 24 h (SOFA24) score was the only risk factor for IMV (OR, 1.97; 95% CI, 1.29-2.99; P = .001). Respiratory parameters at IMV onset for pregnant patients were: mean ± SD plateau pressure (PP), 24.3 ± 4.5 cm H2O; mean ± SD driving pressure (DP), 12.5 ± 3.3 cm H2O; median static compliance (SC), 31 mL/cm H2O (interquartile range [IQR], 26-40 mL/cm H2O); and median Pao2 to Fio2 ratio, 142 (IQR, 110-176). Respiratory parameters before (< 2 h) and after (≤ 2 h and 24 h) delivery were, respectively: mean ± SD PP, 25.6 ± 6.6 cm H2O, 24 ± 6.7 cm H2O, and 24.6 ± 5.2 cm H2O (P = .59); mean ± SD DP, 13.6 ± 4.2 cm H2O, 12.9 ± 3.9 cm H2O, and 13 ± 4.4 cm H2O (P = .69); median SC, 28 mL/cm H2O (IQR, 22.5-39 mL/cm H2O), 30 mL/cm H2O (IQR, 24.5-44 mL/cm H2O), and 30 mL/cm H2O (IQR, 24.5-44 mL/cm H2O; P = .058); and Pao2 to Fio2 ratio, 134 (IQR, 100-230), 168 (IQR, 136-185), and 192 (IQR, 132-232.5; P = .022). Reasons for induced delivery were as follows: maternal, 43 of 71 patients (60.5%); maternal and fetal, 21 of 71 patients (29.5%); and fetal, 7 of 71 patients (9.9%). Fourteen patients (22.2%) continued pregnancy after ICU discharge. Risk factors for maternal mortality were BMI (OR, 1.10; 95% CI, 1.006-1.204; P = .037) and comorbidities (OR, 4.15; 95% CI, 1.212-14.20; P = .023). Risk factors for fetal or neonatal mortality were gestational age at delivery (OR, 0.67; 95% CI, 0.52-0.86; P = .002) and SOFA24 score (OR, 1.53; 95% CI, 1.13-2.08; P = .006). INTERPRETATION: Contrary to expectations, pregnant patient lung mechanics were similar to those of the general population with COVID-19 in the ICU. Delivery was induced mainly for maternal reasons, but did not change ventilatory parameters other than Pao2 to Fio2 ratio. SOFA24 score was the only risk factor for IMV. Maternal mortality was associated independently with BMI and comorbidities. Risk factors for fetal and neonatal mortality were SOFA24 score and gestational age at delivery.

Performance of Invasive Mode in Different Heated Humidification Systems With High-Flow Nasal Cannula.

BACKGROUND: Oxygen therapy via high-flow nasal cannula generates physiologic changes that impact ventilatory variables of patients. However, we know that there are detrimental effects on airway mucosa related to inhalation of gases. The objective of this study was to evaluate the performance in terms of absolute humidity, relative humidity, and temperature of different brands of heated humidifiers and circuits in the invasive mode during the use of high-flow oxygen therapy in flows between 30 and 100 L/min. METHODS: A prospective observational study conducted at the Sanatorio Anchorena equipment analysis laboratory; September 5 to October 20, 2019. RESULTS: A statistically significant interaction was found among the programmed flows and the different combinations of devices and circuits for the delivery of absolute humidity (P < .001). An effect of flow on delivered absolute humidity was found, regardless of the equipment and circuit combination (P < .001). However, in the invasive mode, the combination of the Fisher&Paykel MR850 heated humidifier with the Medtronic-Dar circuit, the Intersurgical circuit, and the AquaVENT circuit always reached or achieved absolute humidity values > 33 mg/L, even at flows up to 100 L/min. The combination of the Flexicare FL9000 heated humidifier with the Fisher&Paykel RT202 circuit, the Fisher&Paykel Evaqua 2 circuit, the Flexicare circuit, the AquaVENT circuit, and the GGM circuit achieved similar results. The mean (SD) of absolute humidity delivered in the invasive mode (36.2 ± 5.9 mg/L) was higher compared with the noninvasive mode (26.8 ± 7.2 mg/L) (P < .001), regardless of circuit and programmed flows. CONCLUSIONS: When heated humidifiers were used in the invasive mode for high-flow oxygen therapy, absolute humidity depended not only on the heated humidifiers and the combination of circuits but also on the programmed flow, especially at flows > 50 L/min. Moreover, the heated humidifiers exhibited different behaviors, in some cases inefficient, in delivering adequate humidification. However, some equipment improved performance when set to the invasive mode.

High-Flow Nasal Cannula and Standard Oxygen in Acute Hypoxemic Respiratory Failure Due to COVID-19.

BACKGROUND: The evidence regarding benefits of high-flow nasal cannula (HFNC) in patients with COVID-19 is controversial. The aim of this study was to evaluate the impact of HFNC in comparison with standard oxygen therapy on the frequency of endotracheal intubation at 28 d in subjects with acute hypoxemic respiratory failure (AHRF) secondary to SARS-CoV-2 infection. METHODS: A retrospective, age- and sex-matched-paired, cohort study was conducted in subjects with moderate-to-severe AHRF. Intervention group was treated with HFNC, and control group was treated with standard oxygen therapy. Baseline characteristics and clinical evolution were analyzed. Mantel-Haenszel test was used for categorical variables. Paired samples Wilcoxon test was used for quantitative variables. Multivariate analysis was performed using conditional multiple logistic regression. RESULTS: Eighty-four subjects were included. The median time from admission to progression of oxygen therapy to FIO2 ≥ 0.5 or HFNC was 1 (interquartile range [IQR] 0-3) d. PaO2 /FIO2 at the time of oxygen therapy progression showed a median of 150.5 (IQR 100.0-170.0) for the entire sample and was lower in HFNC group compared with control group (median 135 [IQR 96-162] vs median 158 [IQR 132-174], respectively, P = .02). Endotracheal intubation at 28 d was observed in 54.8% HFNC and 73.8% standard oxygen (unadjusted odds ratio 0.38 [95% CI 0.13-1.07], P = .069). In the multivariate analysis, presence of dyspnea at hospital admission, Sequential Organ Failure Assessment score, and PaO2 /FIO2 at time of progression of oxygen therapy to FIO2 ≥ 0.5 was identified as confounding factors for the association between the intervention group and the outcome. Use of HFNC was not an independent predictor of endotracheal intubation frequency after adjusting confounders (odds ratio 0.26 [95% CI 0.04-1.51], P = .13). CONCLUSIONS: In this study, HFNC therapy in subjects with AHRF secondary to COVID-19 was not an independent predictor of endotracheal intubation, compared with standard oxygen therapy, after adjusting for confounders.

[Comparison between the first and second COVID-19 wave of patients who required invasive mechanical ventilation in an intensive care unit in Argentina]. / Comparación entre la primera y segunda ola de pacientes con COVID-19 que requirieron ventilación mecánica invasiva en una unidad de cuidados intensivos de Argentina.

INTRODUCTION: the information regarding characteristics and ventilatory results comparing the first (W1) and the second wave (W2) in Argentina are limited. The main objective of this study was to describe general characteristics and ventilatory variables in COVID-19 patients who required invasive mechanical ventilation (IMV) and compare differences between waves. Secondarily, factors associated with mortality in intensive care unit (ICU) were studied. METHODS: We conducted a prospective observational cohort study that included patients older than 18 years infected with SARS-CoV-2 consecutively admitted to ICU with IMV between August 1, 2020, and June 30, 2021. We included 412 patients. RESULTS: We found statistically significant differences (p < 0.001) in age [W1 64(55-72) vs W2 59 (50-66) years], presence of COPD [W1 n = 42 (19.8%) vs. W2 n = 13(6.3%)], plateau pressure [W1 27(25-30) cm H2O vsW2 24 (22-27) cmH2O], driving pressure (ΔP) [W1 15 (13-17) cmH2O vs. W2 12 (11-14) cm H2O] compliance [W1 40 mL/cmH2O (32-46) vs. W2 = 33 mL/cm H2O (27-40)]; reintubation [W1 30.4% (n = 63/207) vs. W2 13.7% (n = 28/205)]. We identified as independent factors associated with mortality the following variables: age [OR 1.07(95% CI 1.05-1.09)], the ΔP in the first 24 hours [OR 1.19(95% CI 1.10-1.28)] and W2 [OR 1.81 (95% IC1.12-2.93); p = 0.015. DISCUSSION: During W2 the patients were younger. It was possible to achieve ventilatory mechanics more adjusted to a protective ventilation strategy. In conclusion, in the patients studied, age and ΔP were independent predictors of mortality.

Introducción: la información sobre características y resultados ventilatorios que comparen la primera (O1) y segunda (O2) ola de COVID-19 en Argentina son limitados. El objetivo principal de este estudio fue describir las características generales y variables ventilatorias en pacientes COVID-19 que requirieron ventilación mecánica invasiva (VMI) y comparar las diferencias entre olas. Secundariamente se estudiaron factores asociados con mortalidad en la unidad de cuidados intensivos (UCI). Métodos: Realizamos un estudio observacional analítico de cohorte prospectiva que incluyó pacientes mayores de 18 años infectados por SARS-CoV-2 ingresados de forma consecutiva a la unidad de cuidados intensivos, con requerimiento de VMI, entre el 1 de agosto de 2020 y el 30 de junio de 2021. Se incluyeron 412 pacientes. Resultados: Encontramos diferencias estadísticamente significativas (p < 0.001) en: la edad [O1 64 (55-72) años versus O2 59 (50-66) años]; presencia de EPOC [O1 n = 41 (19.8%) versus O2 n = 13 (6.3%)]; Presión meseta [O1 27 (25-30) cmH2O versus O224 (22-27) cmH2O],presión de conducción (ΔP) [O1 15 (13-17) cmH2O versus O2 12 (11-14) cmH2O]; complacencia [O1 40 mL/cmH2O (32-46) versus O2 33 mL/cmH2O (27-40)]; reintubación [O1 30.4% (n=63/207) versus O2 13.7% (n=28/205)]. Se identificaron como factores independientes asociados a mortalidad las siguientes variables: edad [(OR 1.07 (IC 95% 1.05-1.09)], el ΔP en las primeras 24 h [(OR 1.19 (IC 95% 1.10-1.28)] y O2 [OR 1.81 (IC 95% 1.12-2.93); p = 0.015]. Discusión: Durante O2, los pacientes eran más jóvenes. Fue posible lograr una mecánica ventilatoria más ajustada a una estrategia de ventilación protectora. Como conclusión, en los pacientes estudiados la edad y ΔP fueron predictores independientes de mortalidad.

Comparación entre la primera y segunda ola de pacientes con COVID-19 que requirieron ventilación mecánica invasiva en una unidad de cuidados intensivos de Argentina / Comparison between the first and second COVID-19 wave of patients who required invasive mechanical ventilation in an intensive care unit in Argentina

Resumen Introducción: la información sobre características y resultados ventilatorios que comparen la primera (O1) y segunda (O2) ola de COVID-19 en Argentina son limitados. El objetivo principal de este estudio fue describir las características generales y variables ventilatorias en pacientes COVID-19 que requirieron ventilación mecánica invasiva (VMI) y comparar las diferencias entre olas. Secundariamente se es tudiaron factores asociados con mortalidad en la unidad de cuidados intensivos (UCI). Métodos: Realizamos un estudio observacional analítico de cohorte prospectiva que incluyó pacientes mayores de 18 años infectados por SARS-CoV-2 ingresados de forma consecutiva a la unidad de cuidados intensivos, con requerimiento de VMI, entre el 1 de agosto de 2020 y el 30 de junio de 2021. Se incluyeron 412 pacientes. Resultados: Encontramos diferencias estadísticamente significativas (p < 0.001) en: la edad [O1 64 (55-72) años versus O2 59 (50-66) años]; presencia de EPOC [O1 n = 41 (19.8%) versus O2 n = 13 (6.3%)]; Presión meseta [O1 27 (25-30) cmH2O versus O224 (22-27) cmH2O],presión de conducción (ΔP) [O1 15 (13-17) cmH2O versus O2 12 (11-14) cmH2O]; complacencia [O1 40 mL/cmH2O (32-46) versus O2 33 mL/cmH2O (27-40)]; reintubación [O1 30.4% (n=63/207) versus O2 13.7% (n=28/205)]. Se identificaron como factores independientes asociados a mortalidad las siguientes variables: edad [(OR 1.07 (IC 95% 1.05-1.09)], el ΔP en las primeras 24 h [(OR 1.19 (IC 95% 1.10-1.28)] y O2 [OR 1.81 (IC 95% 1.12-2.93); p = 0.015]. Discusión: Durante O2, los pacientes eran más jóvenes. Fue posible lograr una mecánica ventilatoria más ajustada a una estrategia de ventilación protectora. Como conclusión, en los pacientes estudiados la edad y ΔP fueron predictores independientes de mortalidad.

Abstract Introduction: the information regarding characteristics and ventilatory results comparing the first (W1) and the second wave (W2) in Argentina are limited. The main objective of this study was to describe general charac teristics and ventilatory variables in COVID-19 patients who required invasive mechanical ventilation (IMV) and compare differences between waves. Secondarily, factors associated with mortality in intensive care unit (ICU) were studied. Methods: We conducted a prospective observational cohort study that included patients older than 18 years infected with SARS-CoV-2 consecutively admitted to ICU with IMV between August 1, 2020, and June 30, 2021. We included 412 patients. Results: We found statistically significant differences (p < 0.001) in age [W1 64(55-72) vs W2 59 (50-66) years], presence of COPD [W1 n = 42 (19.8%) vs. W2 n = 13(6.3%)], plateau pressure [W1 27(25-30) cm H2O vsW2 24 (22-27) cmH2O], driving pressure (ΔP) [W1 15 (13-17) cmH2O vs. W2 12 (11-14) cm H2O] compliance [W1 40 mL/cmH2O (32-46) vs. W2 = 33 mL/cm H2O (27-40)]; reintubation [W1 30.4% (n = 63/207) vs. W2 13.7% (n = 28/205)]. We identified as independent factors associated with mortality the following variables: age [OR 1.07(95% CI 1.05-1.09)], the ΔP in the first 24 hours [OR 1.19(95% CI 1.10- 1.28)] and W2 [OR 1.81 (95% IC1.12-2.93); p = 0.015. Discussion: During W2 the patients were younger. It was possible to achieve ventilatory mechanics more adjusted to a protective ventilation strategy. In conclusion, in the patients studied, age and ΔP were independent predictors of mortality.

High-Flow Oxygen Therapy Application in Chronic Obstructive Pulmonary Disease Patients With Acute Hypercapnic Respiratory Failure: A Multicenter Study.

OBJECTIVES: To evaluate the effect of high-flow oxygen implementation on the respiratory rate as a first-line ventilation support in chronic obstructive pulmonary disease patients with acute hypercapnic respiratory failure. DESIGN: Multicenter, prospective, analytic observational case series study. SETTING: Five ICUs in Argentina, between August 2018 and September 2019. PATIENTS: Patients greater than or equal to 18 years old with moderate to very severe chronic obstructive pulmonary disease, who had been admitted to the ICU with a diagnosis of hypercapnic acute respiratory failure, were entered in the study. INTERVENTIONS: High-flow oxygen therapy through nasal cannula delivered using high-velocity nasal insufflation. MEASUREMENTS AND MAIN RESULTS: Forty patients were studied, 62.5% severe chronic obstructive pulmonary disease. After the first hour of high-flow nasal cannula implementation, there was a significant decrease of respiratory rate compared with baseline values, with a 27% decline (29 vs 21 breaths/min; p < 0.001). Furthermore, a significant reduction of Paco2 (57 vs 52 mm Hg [7.6 vs 6.9 kPa]; p < 0.001) was observed. The high-flow nasal cannula application failed in 18% patients. In this group, the respiratory rate, pH, and Paco2 showed no significant change during the first hour in these patients. CONCLUSIONS: High-flow oxygen therapy through nasal cannula delivered using high-velocity nasal insufflation was an effective tool for reducing respiratory rate in these chronic obstructive pulmonary disease patients with acute hypercapnic respiratory failure. Early determination and subsequent monitoring of clinical and blood gas parameters may help predict the outcome.

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

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.

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.

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.

Performance of Different Active Humidification Systems in High-Flow Oxygen Therapy.

BACKGROUND: We sought to evaluate the performance in terms of absolute humidity (AH), relative humidity (RH), and temperature of different heated humidifiers (HH) and circuits that are commonly used to deliver high-flow oxygen therapy in conventional ranges (30-60 L/min) and unconventional ranges (70-100 L/min). METHODS: In this prospective, observational study, an electronic thermohygrometer was used to obtain the required measurements. A mechanical ventilator was used as a source for high-flow nasal cannula oxygen therapy. For active humidification, the following equipment was used: a HH with standard disposable water trap circuit, 3 servo-controlled HH, and 7 circuits with a heated wire. Data on environmental conditions (ie, temperature, RH, AH) were collected from the laboratory during each measurement; the temperature, RH, and AH resulting from the application of 8 flows (30-100 L/min) were also recorded. Variables were compared with analysis of variance for repeated measurements with Tukey post hoc tests. A value of P < .05 was assumed to be significant. RESULTS: During the study, a statistically significant difference was found in the average AH for each flow for the different devices (P < .005). The highest AH values were recorded with the Fisher & Paykel MR850 and the Medtronic-DAR circuit (AH = 40.8 mg/L with flow of 50 L/min, P < .005), and the lowest AH values were recorded with the Flexicare FL9000 HH and the Flexicare circuit (AH = 11.4 mg/L with 100 L/min flow, P < .005). For flows > 50 L/min, the best performance for all flows in terms of AH was found with the Fisher & Paykel MR850 HH, regardless of the circuit used. CONCLUSIONS: During oxygen therapy with very high gas flows, HH devices behave differently and in many cases are inefficient in delivering adequate humidification, even at conventional flows. Caution is therefore recommended when selecting the device and flow settings for the implementation of high-flow nasal cannula oxygen therapy.

Automatic detection of reverse-triggering related asynchronies during mechanical ventilation in ARDS patients using flow and pressure signals.

Asynchrony due to reverse-triggering (RT) may appear in ARDS patients. The objective of this study is to validate an algorithm developed to detect these alterations in patient-ventilator interaction. We developed an algorithm that uses flow and airway pressure signals to classify breaths as normal, RT with or without breath stacking (BS) and patient initiated double-triggering (DT). The diagnostic performance of the algorithm was validated using two datasets of breaths, that are classified as stated above. The first dataset classification was based on visual inspection of esophageal pressure (Pes) signal from 699 breaths recorded from 11 ARDS patients. The other classification was obtained by vote of a group of 7 experts (2 physicians and 5 respiratory therapists, who were trained in ICU), who evaluated 1881 breaths gathered from recordings from 99 subjects. Experts used airway pressure and flow signals for breaths classification. The RT with or without BS represented 19% and 37% of breaths in Pes dataset while their frequency in the expert's dataset were 3% and 12%, respectively. The DT was very infrequent in both datasets. Algorithm classification accuracy was 0.92 (95% CI 0.89-0.94, P < 0.001) and 0.96 (95% CI 0.95-0.97, P < 0.001), in comparison with Pes and experts' opinion. Kappa statistics were 0.86 and 0.84, respectively. The algorithm precision, sensitivity and specificity for individual asynchronies were excellent. The algorithm yields an excellent accuracy for detecting clinically relevant asynchronies related to RT.

Complications of Congenital Hernia in Pregnancy: A Case Report.

Congenital hernias, frequently misdiagnosed during pregnancy, are potentially fatal and require prompt repair. A pregnant woman with medical history of repaired congenital hernia was admitted with misdiagnosis of preeclampsia. Physical examination and chest x-ray revealed a Bochdalek hernia. Transitory stabilization prompted surgeons to postpone hernia repair, but an urgent thoracotomy was required to relieve a subsequent bowel obstruction that was complicated by an intrathoracic colonic perforation. Emergent cesarean delivery was required with a good maternal and fetal outcome. A multidisciplinary team was present in the operating room. All monitoring catheters were placed in advance in the intensive care unit. During recovery, the patient experienced ventricular fibrillation, presumed to be a manifestation of takotsubo syndrome, which responded favorably to cardiopulmonary resuscitation.

Oxigenoterapia a alto flujo con cánula nasal en el tratamiento de la falla respiratoria aguda hipoxémica en una paciente embarazada: reporte de un caso / High-flow nasal cannula in the treatment of acute hypoxemic respiratory failure in a pregnant patient: case report

RESUMEN Existe poca evidencia que avale el uso de ventilación mecánica no invasiva en falla respiratoria aguda hipoxémica. Sin embargo, considerando las complicaciones asociadas a la intubación endotraqueal, se intentó implementar ventilación mecánica no invasiva en una paciente de 24 años cursando 32 semanas de gestación, que ingresó a la unidad de cuidados intensivos con falla respiratoria aguda hipoxémica y sepsis a foco urinario. La falta de tolerancia a la ventilación mecánica no invasiva, nos indujo a utilizar un método alternativo con el fin de evitar la intubación endotraqueal. La implementación de terapia con oxígeno a alto flujo a través de cánula nasal permitió superar la situación, presentando a ésta técnica como una opción de tratamiento en pacientes obstétricas críticas, segura tanto para la madre como para el feto.

ABSTRACT Little evidence exists to support the use of noninvasive mechanical ventilation for acute hypoxemic respiratory failure. However, considering the complications associated with endotracheal intubation, we attempted to implement noninvasive mechanical ventilation in a 24-year-old patient who was 32 weeks pregnant and was admitted to the intensive care unit with acute hypoxemic respiratory failure and sepsis secondary to a urinary tract infection. Lack of tolerance to noninvasive mechanical ventilation led us to use an alternative method to avoid endotracheal intubation. The use of high-flow nasal cannula allowed to overcome this situation, wich supports this technique as a treatment option for critical obstetric patients that is safe for both the mother and fetus.

Effects of High-Flow Nasal Cannula on End-Expiratory Lung Impedance in Semi-Seated Healthy Subjects.

BACKGROUND: High-flow nasal cannula (HFNC) enables delivery of humidified gas at high flow while controlling the FIO2 . Although its use is growing in patients with acute respiratory failure, little is known about the impact of HFNC on lung volume. Therefore, we aimed to assess lung volume changes in healthy subjects at different flows and positions. METHODS: This was a prospective physiological study performed in 16 healthy subjects. The changes in lung volumes were assessed by measuring end-expiratory lung impedance by using electrical impedance tomography. All the subjects successively breathed during 5 min in these following conditions: while in a supine position without HFNC (T0) and 3 measurements in a semi-seated position at 45° without HFNC (T1), and with HFNC at a flow of 30 L/min (T2), and 50 L/min (T3). RESULTS: Compared with the supine position, the values of end-expiratory lung impedance significantly increased with the subjects in a semi-seated position. End-expiratory lung impedance significantly increased after HFNC initiation in subjects in a semi-seated position and further increased by increasing flow at 50 L/min. When taking the end-expiratory lung impedance measurement in subjects in a semi-seated position (T1) as reference, the differences among the medians of global end-expiratory lung impedance were statistically significant (P < .001), which amounted to 1.05 units in T1; 1.12 units in T2; and 1.44 units in T3 (P < .05 for all comparisons, Wilcoxon test). The breathing frequency did not differ between the supine and semi-seated position (T0 and T1) but significantly decreased after initiation of HFNC and further decreased at high flow. T0 and T1 were not different (P = .13); whereas there was a statistically significant difference among T1, T2, and T3 (P < .05, post hoc test with Bonferroni correction). CONCLUSIONS: In healthy subjects, the semi-seated position and the use of HFNC increased end-expiratory lung impedance globally. These changes were accompanied by a significant decrease in the breathing frequency.

High-flow nasal cannula in the treatment of acute hypoxemic respiratory failure in a pregnant patient: case report. / Oxigenoterapia a alto flujo con cánula nasal en el tratamiento de la falla respiratoria aguda hipoxémica en una paciente embarazada: reporte de un caso.

Little evidence exists to support the use of noninvasive mechanical ventilation for acute hypoxemic respiratory failure. However, considering the complications associated with endotracheal intubation, we attempted to implement noninvasive mechanical ventilation in a 24-year-old patient who was 32 weeks pregnant and was admitted to the intensive care unit with acute hypoxemic respiratory failure and sepsis secondary to a urinary tract infection. Lack of tolerance to noninvasive mechanical ventilation led us to use an alternative method to avoid endotracheal intubation. The use of high-flow nasal cannula allowed to overcome this situation, wich supports this technique as a treatment option for critical obstetric patients that is safe for both the mother and fetus.

Existe poca evidencia que avale el uso de ventilación mecánica no invasiva en falla respiratoria aguda hipoxémica. Sin embargo, considerando las complicaciones asociadas a la intubación endotraqueal, se intentó implementar ventilación mecánica no invasiva en una paciente de 24 años cursando 32 semanas de gestación, que ingresó a la unidad de cuidados intensivos con falla respiratoria aguda hipoxémica y sepsis a foco urinario. La falta de tolerancia a la ventilación mecánica no invasiva, nos indujo a utilizar un método alternativo con el fin de evitar la intubación endotraqueal. La implementación de terapia con oxígeno a alto flujo a través de cánula nasal permitió superar la situación, presentando a ésta técnica como una opción de tratamiento en pacientes obstétricas críticas, segura tanto para la madre como para el feto.

Evaluation of an active humidification system for inspired gas.

OBJECTIVES: The effectiveness of the active humidification systems (AHS) in patients already weaned from mechanical ventilation and with an artificial airway has not been very well described. The objective of this study was to evaluate the performance of an AHS in chronically tracheostomized and spontaneously breathing patients. METHODS: Measurements were quantified at three levels of temperature (T°) of the AHS: level I, low; level II, middle; and level III, high and at different flow levels (20 to 60 L/minute). Statistical analysis of repeated measurements was performed using analysis of variance and significance was set at a P<0.05. RESULTS: While the lowest temperature setting (level I) did not condition gas to the minimum recommended values for any of the flows that were used, the medium temperature setting (level II) only conditioned gas with flows of 20 and 30 L/minute. Finally, at the highest temperature setting (level III), every flow reached the minimum absolute humidity (AH) recommended of 30 mg/L. CONCLUSION: According to our results, to obtain appropiate relative humidity, AH and T° of gas one should have a device that maintains water T° at least at 53℃ for flows between 20 and 30 L/m, or at T° of 61℃ at any flow rate.