Pediatric Simulation of Intrinsic PEEP and Patient-Ventilator Trigger Asynchrony During Mechanical Ventilation.

BACKGROUND: Intrinsic PEEP during mechanical ventilation occurs when there is insufficient time for expiration to functional residual capacity before the next inspiration, resulting in air trapping. Increased expiratory resistance (RE), too rapid of a patient or ventilator breathing rate, or a longer inspiratory to expiratory time ratio (TI/TE) can all be causes of intrinsic PEEP. Intrinsic PEEP can result in increased work of breathing and patient-ventilator asynchrony (PVA) during patient-triggered breaths. We hypothesized that the difference between intrinsic PEEP and ventilator PEEP acts as an inspiratory load resulting in trigger asynchrony that needs to be overcome by increased respiratory muscle pressure (Pmus). METHODS: Using a Servo lung model (ASL 5000) and LTV 1200 ventilator in pressure control mode, we developed a passive model demonstrating how elevated RE increases intrinsic PEEP above ventilator PEEP. We also developed an active model investigating the effects of RE and intrinsic PEEP on trigger asynchrony (expressed as percentage of patient-initiated breaths that failed to trigger). We then studied if trigger asynchrony could be reduced by increased Pmus. RESULTS: Intrinsic PEEP increased significantly with increasing RE (r = 0.97, P = .006). Multivariate logistic regression analysis showed that both RE and negative Pmus levels affect trigger asynchrony (P < .001). CONCLUSIONS: A passive lung model describes the development of increasing intrinsic PEEP with increasing RE at a given ventilator breathing rate. An active lung model shows how this can lead to trigger asynchrony since the Pmus needed to trigger a breath is greater with increased RE, as the inspiratory muscles must overcome intrinsic PEEP. This model will lend itself to the study of intrinsic PEEP engendered by a higher ventilator breathing rate, as well as higher TI/TE, and will be useful in ventilator simulation scenarios of PVA. The model also suggests that increasing ventilator PEEP to match intrinsic PEEP can improve trigger asynchrony through a reduction in RE.

Lesão renal aguda em pacientes críticos em ventilação mecânica com pressão positiva / Lesión renal aguda en pacientes críticos en ventilación mecánica con presión positiva / Acute kidney injury in critically ill patients on positive pressure mechanical ventilation

Resumo Objetivo Avaliar o efeito do uso de ventilação mecânica com pressão positiva expiratória final (PEEP) na função renal dos pacientes internados em Unidade de Terapia Intensiva (UTI). Métodos Estudo de coorte retrospectivo, quantitativo, desenvolvido na UTI de um hospital público de Brasília, Distrito Federal. A amostra foi constituída de 52 prontuários de pacientes internados na UTI de novembro de 2016 a dezembro de 2018. A coleta dos dados foi realizada por meio de um questionário com dados demográficos, clínicos e laboratoriais. Os pacientes foram alocados em grupos: (1) PEEP ≤ 5 cmH2O, (2) PEEP > 5 cmH2O e < 10 cmH2O e (3) PEEP ≥ 10 cmH2O. Resultados A média de idade dos pacientes foi de 59 anos e 50% deles tinha mais de 63 anos. Constatou-se que 63,16% dos pacientes que estavam em ventilação mecânica com pressão positiva ao final da expiração ≥ 10 cmH2O evoluíram no estágio 1 (menor gravidade de lesão renal aguda (LRA)) e 21,5% no estágio 2 (moderada gravidade). Ainda assim, um pequeno percentual (5,8%) de pacientes evoluiu a óbito. Pacientes sem sucesso no desmame da ventilação mecânica apresentaram 10,24 vezes a chance de evoluir com LRA. Conclusão o emprego da ventilação mecânica pode determinar danos à função renal dos pacientes internados em unidade de terapia intensiva e que aqueles com maior necessidade de oferta de PEEP evoluíram com diferentes gravidades e persistência da LRA.

Resumen Objetivo Evaluar el efecto del uso de la ventilación mecánica con presión positiva espiratoria final (PEEP) en la función renal de los pacientes internados en Unidad de Cuidados Intensivos (UTI). Métodos Estudio de corte retrospectivo, cuantitativo, desarrollado en la UCI de un hospital público de Brasília, Distrito Federal. La amuestra estuvo constituida por 52 prontuarios de pacientes internados en la UCI de noviembre de 2016 a diciembre de 2018. La recolección de los datos se realizó por medio de un cuestionario con datos demográficos, clínicos y laboratoriales. Los pacientes fueron distribuidos en grupos: (1) PEEP ≤ 5 cmH2O, (2) PEEP > 5 cmH2O y < 10 cmH2O y (3) PEEP ≥ 10 cmH2O. Resultados El promedio de edad de los pacientes era de 59 años y el 50 % de ellos tenía más de 63 años. Se constató que el 63,16 % de los pacientes que estaban en ventilación mecánica con presión positiva al final de la expiración ≥ 10 cmH2O evolucionaron en la etapa 1 (menor gravedad de lesión renal aguda (LRA)) y 21,5 % en la etapa 2 (moderada gravedad). Aun así, un pequeño porcentaje (5,8 %) de pacientes falleció. Pacientes sin éxito en la descontinuación de la ventilación mecánica presentaron 10,24 veces la posibilidad de evolucionar con LRA. Conclusión el uso de la ventilación mecánica puede determinar daños a la función renal de los pacientes internados en una unidad de cuidados intensivos y que los que tengan una mayor necesidad de oferta de PEEP evolucionaron con distintas gravedades y persistencia de la LRA.

Abstract Objective To assess the effect of using mechanical ventilation with positive end-expiratory pressure (PEEP) on the renal function of patients admitted to the Intensive Care Unit (ICU). Methods This is a quantitative retrospective cohort study developed in the ICU of a public hospital in Brasília, Distrito Federal. The sample consisted of 52 medical records of patients admitted to the ICU from November 2016 to December 2018. Data collection was performed through a questionnaire with demographic, clinical and laboratory data. Patients were allocated in two groups: (1) PEEP ≤ 5 cmH2O, (2) PEEP > 5 cmH2O and < 10 cmH2O, and (3) PEEP ≥ 10 cmH2O. Results The mean age of patients was 59 years and 50% of them were over 63 years. It was found that 63.16% of patients who were on mechanical ventilation with positive end-expiratory pressure ≥ 10 cmH2O evolved in stage 1 (less severe acute kidney injury (AKI)) and 21.5% in stage 2 (moderate gravity). Even so, a small percentage (5.8%) of patients died. Patients who were unsuccessful in weaning from mechanical ventilation had a 10.24-fold chance of developing AKI. Conclusion mechanical ventilation use can cause damage to the renal function of patients hospitalized in the intensive care unit and that those with greater need to offer PEEP evolved with different severities and persistence of AKI.

Characterization of pulmonary impairment associated with COVID-19 in patients requiring mechanical ventilation. / Caracterização do comprometimento pulmonar associado à COVID-19 em pacientes com necessidade de ventilação mecânica.

OBJECTIVE: To detect early respiratory and hemodynamic instability to characterize pulmonary impairment in patients with severe COVID-19. METHODS: We retrospectively analyzed data collected from COVID-19 patients suffering from acute respiratory failure requiring intubation and mechanical ventilation. We used transpulmonary thermodilution assessment with a PiCCO™ device. We collected demographic, respiratory, hemodynamic and echocardiographic data within the first 48 hours after admission. Descriptive statistics were used to summarize the data. RESULTS: Fifty-three patients with severe COVID-19 were admitted between March 22nd and April 7th. Twelve of them (22.6%) were monitored with a PiCCO™ device. Upon admission, the global-end diastolic volume indexed was normal (mean 738.8mL ± 209.2) and moderately increased at H48 (879mL ± 179), and the cardiac index was subnormal (2.84 ± 0.65). All patients showed extravascular lung water over 8mL/kg on admission (17.9 ± 8.9). We did not identify any argument for cardiogenic failure. CONCLUSION: In the case of severe COVID-19 pneumonia, hemodynamic and respiratory presentation is consistent with pulmonary edema without evidence of cardiogenic origin, favoring the diagnosis of acute respiratory distress syndrome.

OBJETIVO: Detectar precocemente a instabilidade respiratória e hemodinâmica para caracterizar o comprometimento pulmonar em pacientes com COVID-19 grave. MÉTODOS: Analisamos retrospectivamente os dados colhidos de pacientes com COVID-19 que apresentaram insuficiência respiratória aguda com necessidade de intubação e ventilação mecânica. Utilizamos a avaliação da termodiluição transpulmonar por meio do dispositivo PiCCO™. Foram coletados os dados demográficos, respiratórios, hemodinâmicos e ecocardiográficos dentro das primeiras 48 horas após a admissão. Para resumir os dados, utilizamos estatística descritiva. RESULTADOS: Entre 22 de março e 7 de abril de 2020, foram admitidos 23 pacientes com COVID-19 grave. Foram monitorados com o dispositivo PiCCO™ 12 (22,6%) deles. Quando da admissão, o volume diastólico final global indexado era normal (média de 738,8mL ± 209,2) e, na hora 48, encontrava-se moderadamente aumentado (879mL ± 179), enquanto o índice cardíaco se achava abaixo do normal (2,84 ± 0,65). Todos os pacientes revelaram a presença de água extravascular pulmonar acima de 8mL/kg na admissão (17,9 ± 8,9). Não identificamos qualquer evidência de origem cardiogênica. CONCLUSÃO: No caso de pneumonia grave por COVID-19, o quadro hemodinâmico e respiratório é compatível com edema pulmonar sem evidência de origem cardiogênica, o que favorece o diagnóstico de síndrome do desconforto respiratório agudo.

Caracterização do comprometimento pulmonar associado à COVID-19 em pacientes com necessidade de ventilação mecânica / Characterization of pulmonary impairment associated with COVID-19 in patients requiring mechanical ventilation

RESUMO Objetivo: Detectar precocemente a instabilidade respiratória e hemodinâmica para caracterizar o comprometimento pulmonar em pacientes com COVID-19 grave. Métodos: Analisamos retrospectivamente os dados colhidos de pacientes com COVID-19 que apresentaram insuficiência respiratória aguda com necessidade de intubação e ventilação mecânica. Utilizamos a avaliação da termodiluição transpulmonar por meio do dispositivo PiCCO™. Foram coletados os dados demográficos, respiratórios, hemodinâmicos e ecocardiográficos dentro das primeiras 48 horas após a admissão. Para resumir os dados, utilizamos estatística descritiva. Resultados: Entre 22 de março e 7 de abril de 2020, foram admitidos 23 pacientes com COVID-19 grave. Foram monitorados com o dispositivo PiCCO™ 12 (22,6%) deles. Quando da admissão, o volume diastólico final global indexado era normal (média de 738,8mL ± 209,2) e, na hora 48, encontrava-se moderadamente aumentado (879mL ± 179), enquanto o índice cardíaco se achava abaixo do normal (2,84 ± 0,65). Todos os pacientes revelaram a presença de água extravascular pulmonar acima de 8mL/kg na admissão (17,9 ± 8,9). Não identificamos qualquer evidência de origem cardiogênica. Conclusão: No caso de pneumonia grave por COVID-19, o quadro hemodinâmico e respiratório é compatível com edema pulmonar sem evidência de origem cardiogênica, o que favorece o diagnóstico de síndrome do desconforto respiratório agudo.

ABSTRACT Objective: To detect early respiratory and hemodynamic instability to characterize pulmonary impairment in patients with severe COVID-19. Methods: We retrospectively analyzed data collected from COVID-19 patients suffering from acute respiratory failure requiring intubation and mechanical ventilation. We used transpulmonary thermodilution assessment with a PiCCO™ device. We collected demographic, respiratory, hemodynamic and echocardiographic data within the first 48 hours after admission. Descriptive statistics were used to summarize the data. Results: Fifty-three patients with severe COVID-19 were admitted between March 22nd and April 7th. Twelve of them (22.6%) were monitored with a PiCCO™ device. Upon admission, the global-end diastolic volume indexed was normal (mean 738.8mL ± 209.2) and moderately increased at H48 (879mL ± 179), and the cardiac index was subnormal (2.84 ± 0.65). All patients showed extravascular lung water over 8mL/kg on admission (17.9 ± 8.9). We did not identify any argument for cardiogenic failure. Conclusion: In the case of severe COVID-19 pneumonia, hemodynamic and respiratory presentation is consistent with pulmonary edema without evidence of cardiogenic origin, favoring the diagnosis of acute respiratory distress syndrome.

Intrinsic Dynamic Positive End-Expiratory Pressure in Stable Patients with Chronic Obstructive Pulmonary Disease.

BACKGROUND: Assessment of intrinsic dynamic positive end-expiratory pressure (PEEPi,dyn) may be clinically important in stable patients with chronic obstructive pulmonary disease (COPD), but epidemiological data are scant. OBJECTIVES: The aim of our study was (i) to assess the PEEPi,dyn in a large population of stable patients with COPD and (ii) to evaluate the correlations with some noninvasive measurements routinely assessed. METHOD: Retrospective analysis of lung mechanics, dynamic volumes, arterial blood gases, dyspnoea by means of the Medical Research Council (MRC) scale, the COPD Assessment Test score, and maximal inspiratory/expiratory pressures in 87 hypercapnic and 62 normocapnic patients. RESULTS: The mean PEEPi,dyn was significantly higher in hypercapnic than normocapnic patients (2.8 ± 2.2 vs. 1.9 ± 1.6 cm H2O, respectively, p = 0.0094). PEEPi,dyn did not differ according to Global Initiative for Chronic Obstructive Lung Disease stage, MRC score, or use or not of long-term oxygen therapy. There were significant although weak correlations between PEEPi,dyn and airway obstruction, hyperinflation, respiratory muscle function, arterial CO2 tension, and number of exacerbations/year. The transdiaphragmatic pressure was the strongest variable associated to PEEPi,dyn (R = 0.5713, p = 0.001). CONCLUSION: In stable patients with COPD, PEEPi,dyn is higher in hypercapnic patients and weakly correlated to noninvasive measures of lung and respiratory muscle function.

Abordaje hemodinámico y ventilatorio en pacientes con COVID-19.

The severe acute respiratory syndrome (SARS-Cov-2) is a clinical entity generated by this new virus a Coronavirus (COVID-19). Disease called COVID-19 (CoronaVIrus Disease 2019) by the World Health Organization. Its presentation is acute respiratory failure characterized by hyperinflation of the lung that leads to an increase in capillaries and epithelial permeability, with loss of ventilation of lung tissue and increases lung stiffness. These disturbances lead to imbalances between ventilation and perfusion ratio, which ultimately result in hypoxemia and impaired carbon dioxide clearance. For this review, a search of PubMed and Trip Database was performed. Due to the scarcity of publications, a specific search algorithm was not used. The objective is to review, the evidence and the recommendations of national and international experts, of the hemodynamic and ventilatory management of these patients.

El coronavirus del síndrome respiratorio agudo grave 2 (SARS-CoV-2, conocido previamente como nCoV-2019) es el agente causal de una nueva enfermedad denominada COVID-19 (COronaVIrus Disease 2019) por la Organización Mundial de la Salud. Su presentación es la insuficiencia respiratoria aguda caracterizada por una hiperinflación del pulmón que conduce a un incremento de los capilares y permeabilidad epitelial, con pérdida de la aireación de tejido pulmonar e incremento de la rigidez pulmonar. Estas alteraciones conducen a desequilibrios entre la ventilación y la relación de perfusión, que finalmente resultan en hipoxemia y deterioro de la depuración de dióxido de carbono. Para la presente revisión se realizó una búsqueda en PubMed y Trip Database. Debido a la escasez de publicaciones no se utilizó un algoritmo de búsqueda específico. El objetivo es dar a conocer, de acuerdo con la evidencia y las recomendaciones de expertos nacionales e internacionales, el manejo hemodinámico y ventilatorio de estos pacientes.

Exploring a social work lead mindfulness-based intervention to address burnout among inpatient psychiatric nurses: a pilot study.

Acute psychiatric nurses experience workplace stressors related to organizational factors including staffing shortages, along with interpersonal conflict with patients and colleagues. The pilot study examined the experience of burnout among acute care psychiatric nurses and the usefulness of a social work lead mindfulness-based intervention for reducing burnout elements. Findings indicated participants experienced emotional exhaustion associated with their work, but also a significant degree of personal accomplishment. Nurses identified the intervention as having the potential to promote better emotional regulation in the workplace and beyond. Social worker education on mindfulness techniques may represent an untapped resource for improving the emotional wellness and effective patient care.

Mean Airway Pressure As a Predictor of 90-Day Mortality in Mechanically Ventilated Patients.

OBJECTIVES: To determine the association between mean airway pressure and 90-day mortality in patients with acute respiratory failure requiring mechanical ventilation and to compare the predictive ability of mean airway pressure compared with inspiratory plateau pressure and driving pressure. DESIGN: Prospective observational cohort. SETTING: Five ICUs in Lima, Peru. SUBJECTS: Adults requiring invasive mechanical ventilation via endotracheal tube for acute respiratory failure. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of potentially eligible participants (n = 1,500), 65 (4%) were missing baseline mean airway pressure, while 352 (23.5%) were missing baseline plateau pressure and driving pressure. Ultimately, 1,429 participants were included in the analysis with an average age of 59 ± 19 years, 45% female, and a mean PaO2/FIO2 ratio of 248 ± 147 mm Hg at baseline. Overall, 90-day mortality was 50.4%. Median baseline mean airway pressure was 13 cm H2O (interquartile range, 10-16 cm H2O) in participants who died compared to a median mean airway pressure of 12 cm H2O (interquartile range, 10-14 cm H2O) in participants who survived greater than 90 days (p < 0.001). Mean airway pressure was independently associated with 90-day mortality (odds ratio, 1.38 for difference comparing the 75th to the 25th percentile for mean airway pressure; 95% CI, 1.10-1.74) after adjusting for age, sex, baseline Acute Physiology and Chronic Health Evaluation III, baseline PaO2/FIO2 (modeled with restricted cubic spline), baseline positive end-expiratory pressure, baseline tidal volume, and hospital site. In predicting 90-day mortality, baseline mean airway pressure demonstrated similar discriminative ability (adjusted area under the curve = 0.69) and calibration characteristics as baseline plateau pressure and driving pressure. CONCLUSIONS: In a multicenter prospective cohort, baseline mean airway pressure was independently associated with 90-day mortality in mechanically ventilated participants and predicts mortality similarly to plateau pressure and driving pressure. Because mean airway pressure is readily available on all mechanically ventilated patients and all ventilator modes, it is a potentially more useful predictor of mortality in acute respiratory failure.

Innovative in vitro method to study ventilator induced lung injury.

Mechanical ventilation (MV) is a life-saving therapy for critically ill patients, alleviating the work of breathing and supporting adequate gas exchange. However, MV can cause ventilator induced lung injury (VILI) by baro/volu- and atelectrauma, even lead to acute respiratory distress syndrome (ARDS), and substantially augment mortality. There is a need for specific biomarkers and novel research platforms for VILI/ARDS research to study these detrimental disorders and seek ways to avoid or prevent them. Previous in vitro studies on bronchial epithelium, cultured in air-liquid interface (ALI) conditions, have generally utilized static or constant pressure.  We have developed a Cyclical Pressure ALI Device (CPAD) that enables cyclical stress on ALI cultured human bronchial cells, with the aim of mimicking the effects of MV. Using CPAD we were able to analyze differentially expressed VILI/ARDS and innate immunity associated genes along with increased expression of associated proteins. CPAD provides an easy and accessible way to analyze functional and phenotypic changes that occur during VILI and may provide a platform for future drug testing.

Continuous monitoring of intrinsic PEEP based on expired CO2 kinetics: an experimental validation study.

BACKGROUND: Quantification of intrinsic PEEP (PEEPi) has important implications for patients subjected to invasive mechanical ventilation. A new non-invasive breath-by-breath method (etCO2D) for determination of PEEPi is evaluated. METHODS: In 12 mechanically ventilated pigs, dynamic hyperinflation was induced by interposing a resistance in the endotracheal tube. Airway pressure, flow, and exhaled CO2 were measured at the airway opening. Combining different I:E ratios, respiratory rates, and tidal volumes, 52 different levels of PEEPi (range 1.8-11.7 cmH2O; mean 8.45 ± 0.32 cmH2O) were studied. The etCO2D is based on the detection of the end-tidal dilution of the capnogram. This is measured at the airway opening by means of a CO2 sensor in which a 2-mm leak is added to the sensing chamber. This allows to detect a capnogram dilution with fresh air when the pressure coming from the ventilator exceeds the PEEPi. This method was compared with the occlusion method. RESULTS: The etCO2D method detected PEEPi step changes of 0.2 cmH2O. Reference and etCO2D PEEPi presented a good correlation (R2 0.80, P < 0.0001) and good agreement, bias - 0.26, and limits of agreement ± 1.96 SD (2.23, - 2.74) (P < 0.0001). CONCLUSIONS: The etCO2D method is a promising accurate simple way of continuously measure and monitor PEEPi. Its clinical validity needs, however, to be confirmed in clinical studies and in conditions with heterogeneous lung diseases.

EPISYNC study: predictors of patient-ventilator asynchrony in a prospective cohort of patients under invasive mechanical ventilation - study protocol.

INTRODUCTION: Patient-ventilator asynchrony is common during the entire period of invasive mechanical ventilation (MV) and is associated with worse clinical outcomes. However, risk factors associated with asynchrony are not completely understood. The main objectives of this study are to estimate the incidence of asynchrony during invasive MV and its association with respiratory mechanics and other baseline patient characteristics. METHODS AND ANALYSIS: We designed a prospective cohort study of patients admitted to the intensive care unit (ICU) of a university hospital. Inclusion criteria are adult patients under invasive MV initiated for less than 72 hours, and with expectation of remaining under MV for more than 24 hours. Exclusion criteria are high flow bronchopleural fistula, inability to measure respiratory mechanics and previous tracheostomy. Baseline assessment includes clinical characteristics of patients at ICU admission, including severity of illness, reason for initiation of MV, and measurement of static mechanics of the respiratory system. We will capture ventilator waveforms during the entire MV period that will be analysed with dedicated software (Better Care, Barcelona, Spain), which automatically identifies several types of asynchrony and calculates the asynchrony index (AI). We will use a linear regression model to identify risk factors associated with AI. To assess the relationship between survival and AI we will use Kaplan-Meier curves, log rank tests and Cox regression. The calculated sample size is 103 patients. The statistical analysis will be performed by the software R Programming (www.R-project.org) and will be considered statistically significant if the p value is less than 0.05. ETHICS AND DISSEMINATION: The study was approved by the Ethics Committee of Instituto do Coração, School of Medicine, University of São Paulo, Brazil, and informed consent was waived due to the observational nature of the study. We aim to disseminate the study findings through peer-reviewed publications and national and international conference presentations. TRIAL REGISTRATION NUMBER: NCT02687802; Pre-results.

Identifying and treating intrinsic PEEP in infants with severe bronchopulmonary dysplasia.

RATIONALE: Infants with severe bronchopulmonary dysplasia (sBPD) and airway obstruction may develop dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEPi ), which impairs patient/ventilator synchrony. OBJECTIVES: To determine if PEEPi is present in infants with sBPD during spontaneous breathing and if adjusting ventilator PEEP improves patient/ventilator synchrony and comfort. METHODS: Interventional study in infants with sBPD. PEEPi measured by esophageal pressure (Pes) and pneumotachometer, during pressure-supported breaths. PEEP i defined as the difference between Pes at start of the inspiratory effort minus Pes at onset of inspiratory flow. The set PEEP was adjusted to minimize PEEP i . "Best PEEP" was the setting with minimal wasted efforts (WE), an inspiratory effort seen on the Pes waveform without a corresponding ventilator breath. FiO 2 and SpO 2 measured pre- and post-PEEP adjustment. Sedation requirements evaluated 72 hours preprocedure and postprocedure. RESULTS: Twelve infants were assessed (gestational age, 24.9 ± 1.4 weeks; study age, 48.8 ± 1.5 weeks, postmenstrual age). Mean baseline ventilator PEEP was 16.4 cm H2 O (14-20 cm H 2 O). Eight infants required an increase, one, a reduction, and three, no change in the set PEEP. For the eight infants requiring an increase in set PEEP, there was an 18.9% reduction in WE and a reduction in FiO 2 (0.084 ± 0.058) requirements in the subsequent 24 hours. Conditional sedation was reduced in five infants postprocedure. No adverse events occurred during testing. CONCLUSION: PEEPi is measurable in infants with sBPD with concurrent esophageal manometry and flow-time tracings without the need for pharmacological paralysis. In those with PEEP i , increasing ventilator PEEP to offset PEEP i improves synchrony.

Lung Compliance and Outcomes in Patients With Acute Respiratory Distress Syndrome Receiving ECMO.

BACKGROUND: Limited data are available regarding mechanical ventilation strategies in patients with acute respiratory distress syndrome receiving extracorporeal membrane oxygenation (ECMO). METHODS: A retrospective analysis of acute respiratory distress syndrome patients on ECMO was conducted in 9 hospitals in Korea. Data on ventilator settings (pre-ECMO and 0, 4, 24, and 48 hours after ECMO) were collected. Based on the effect of the duration and intensity of mechanical ventilator on outcomes, time-weighted average values were calculated for ventilator parameters. RESULTS: The 56 patients included in the study had a mean age of 55.5 years. The hospital and 6-month mortality rates were 48.1% and 54.0%, respectively, with a median ECMO duration of 9.4 days. After initiation of ECMO, peak inspiratory pressure, above positive end-expiratory pressure, tidal volume, and respiration rate were reduced, while lung compliance did not change significantly. Before and during ECMO support, tidal volume and lung compliance were higher in 6-month survivors than in nonsurvivors. In Cox proportional models, both lung compliance (odds ratio, 0.961; 95% confidence interval, 0.928 to 0.995) and time-weighted average-lung compliance (odds ratio, 0.943; 95% confidence interval, 0.903 to 0.986) were significantly associated with 6-month mortality. Kaplan-Meier curves revealed that patients with higher lung compliance before ECMO had a longer survival time at the 6-month follow-up than did those with lower lung compliance. CONCLUSIONS: Lung compliance, whether before or during ECMO, may be an important predictor of outcome in acute respiratory distress syndrome patients receiving ECMO. However, this result requires confirmation in larger clinical studies.

[Effect of neurally adjusted ventilatory assist on trigger of mechanical ventilation in acute exacerbation of chronic obstructive pulmonary disease patients with intrinsic positive end-expiratory pressure].

Objective: To compare the trigger delay and work of trigger between neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients with intrinsic positive end-expiratory pressure (PEEP) during mechanical ventilation. Methods: AECOPD patients with intrinsic PEEP (PEEPi) greater than or equal to 3 cmH(2)O (1 cmH(2)O=0.098 kPa) were enrolled during invasive mechanical ventilation. Subjects were ventilated with low, medium and high pressure under either NAVA or PSV mode. Servo Tracker software continuously recorded the waveform of ventilator and respiratory mechanics indexes (including respiratory frequency, inspiratory tidal volume (Vti), minute ventilation volume (VE), peak airway pressure (PIP), inspiratory time), and calculated trigger and expiratory conversion delay time, work of trigger and total work of breath. Results: A total of 14 AECOPD patients were enrolled with the average PEEPi (4.3±1.3) cmH(2)O. PSV inspiratory trigger delay time was positively correlated with PEEPi (r=0.913, P<0.05). Compared with PSV, NAVA significantly decreased trigger delay time in low, medium and high pressure level groups [(48±17) ms vs. (167±86) ms, (63±65) ms vs. (247±240) ms, (63±49) ms vs. (342±192) ms,respectively all P<0.05]. Similar results were shown as to work of trigger [(0.92±0.36) µV∙s vs. (1.22±0.70) µV∙s, (1.08±0.51) µV∙s vs. (1.62±1.25) µV∙s, (1.20±0.96) µV∙s vs. (2.29±1.02) µV∙s, all P<0.05]. Trigger delay time increased according to the increase of pressure level in PSV mode. Conclusion: The presence of PEEPi in AECOPD patients leads to obvious trigger delay under PSV mode, which is positively correlated with PEEPi level. NAVA significantly reduces trigger delay time and work of trigger compared with PSV mode.

3D airway model to assess airway dead space.

High flow therapy works partly by washout of airway dead space, the volume of which has not been quantified in newborns. This observational study aimed to quantify airway dead space in infants and to compare efficacy of washout between high flow devices in three-dimensional (3D) printed airway models of infants weighing 2.5-3.8 kg. Nasopharyngeal airway dead space volume was 1.5-2.0 mL/kg in newborns. A single cannula device produced lower carbon dioxide (CO2) levels than a dual cannula device (33.7, 31.2, 23.1, 15.9, 10.9 and 6.3 mm Hg vs 36.8, 35.5, 32.1, 26.8, 23.1 and 18.8 mm Hg at flow rates of 1, 2, 3, 4, 6 and 8 L/min, respectively; p<0.0001 at all flow rates). Airway pressure was 1 mm Hg at all flow rates with the single cannula but increased at higher flow rates with the dual cannula.Relative nasopharyngeal airway dead space volume is increased in newborns. In 3D-printed airway models, a single cannula high flow device produces improved CO2 washout with lower airway pressure.