Pendelluft in hypoxemic patients resuming spontaneous breathing: proportional modes versus pressure support ventilation.

BACKGROUND: Internal redistribution of gas, referred to as pendelluft, is a new potential mechanism of effort-dependent lung injury. Neurally-adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV +) follow the patient's respiratory effort and improve synchrony compared with pressure support ventilation (PSV). Whether these modes could prevent the development of pendelluft compared with PSV is unknown. We aimed to compare pendelluft magnitude during PAV + and NAVA versus PSV in patients with resolving acute respiratory distress syndrome (ARDS). METHODS: Patients received either NAVA, PAV + , or PSV in a crossover trial for 20-min using comparable assistance levels after controlled ventilation (> 72 h). We assessed pendelluft (the percentage of lost volume from the non-dependent lung region displaced to the dependent region during inspiration), drive (as the delta esophageal swing of the first 100 ms [ΔPes 100 ms]) and inspiratory effort (as the esophageal pressure-time product per minute [PTPmin]). We performed repeated measures analysis with post-hoc tests and mixed-effects models. RESULTS: Twenty patients mechanically ventilated for 9 [5-14] days were monitored. Despite matching for a similar tidal volume, respiratory drive and inspiratory effort were slightly higher with NAVA and PAV + compared with PSV (ΔPes 100 ms of -2.8 [-3.8--1.9] cm H2O, -3.6 [-3.9--2.4] cm H2O and -2.1 [-2.5--1.1] cm H2O, respectively, p < 0.001 for both comparisons; PTPmin of 155 [118-209] cm H2O s/min, 197 [145-269] cm H2O s/min, and 134 [93-169] cm H2O s/min, respectively, p < 0.001 for both comparisons). Pendelluft magnitude was higher in NAVA (12 ± 7%) and PAV + (13 ± 7%) compared with PSV (8 ± 6%), p < 0.001. Pendelluft magnitude was strongly associated with respiratory drive (ß = -2.771, p-value < 0.001) and inspiratory effort (ß = 0.026, p < 0.001), independent of the ventilatory mode. A higher magnitude of pendelluft in proportional modes compared with PSV existed after adjusting for PTPmin (ß = 2.606, p = 0.010 for NAVA, and ß = 3.360, p = 0.004 for PAV +), and only for PAV + when adjusted for respiratory drive (ß = 2.643, p = 0.009 for PAV +). CONCLUSIONS: Pendelluft magnitude is associated with respiratory drive and inspiratory effort. Proportional modes do not prevent its occurrence in resolving ARDS compared with PSV.

Dynamic relative regional lung strain estimated by computed tomography and electrical impedance tomography in ARDS patients.

BACKGROUND: In the acute distress respiratory syndrome (ARDS), specific lung regions can be exposed to excessive strain due to heterogeneous disease, gravity-dependent lung collapse and injurious mechanical ventilation. Computed tomography (CT) is the gold standard for regional strain assessment. An alternative tool could be the electrical impedance tomography (EIT). We aimed to determine whether EIT-based methods can predict the dynamic relative regional strain (DRRS) between two levels of end-expiratory pressure (PEEP) in gravity-non-dependent and dependent lung regions. METHODS: Fourteen ARDS patients underwent CT and EIT acquisitions (at end-inspiratory and end-expiratory) at two levels of PEEP: a low-PEEP based on ARDS-net strategy and a high-PEEP titrated according to EIT. Three EIT-based methods for DRRS were compared to relative CT-based strain: (1) the change of the ratio between EIT ventilation and end-expiratory lung impedance in arbitrary units ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]), (2) the change of ΔZ/EELI ratio calibrated to mL ([ΔZml low-PEEP/EELIml low-PEEP]/[ΔZml high-PEEP/EELIml high-PEEP]) using CT data, and (3) the relative change of ∆ZAU (∆ZAU low-PEEP/∆ZAU high-PEEP). We performed linear regressions analysis and calculated bias and limits of agreement to assess the performance of DRRS by EIT in comparison with CT. RESULTS: The DRRS assessed by (ΔZml low-PEEP/EELIml low-PEEP)/(ΔZml high-PEEP/EELIml high-PEEP) and ∆ZAU low-PEEP/∆ZAU high-PEEP showed good relationship and agreement with the CT method (R2 of 0.9050 and 0.8679, respectively, in non-dependent region; R2 of 0.8373 and 0.6588, respectively, in dependent region; biases ranging from - 0.11 to 0.51 and limits of agreement ranging from - 0.73 to 1.16 for both methods and lung regions). Conversely, DRRS based on EELIAU ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]) exhibited a weak negative relationship and poor agreement with the CT method for both non-dependent and dependent regions (R2 ~ 0.3; bias of 3.11 and 2.08, and limits of agreement of - 2.13 to 8.34 and from - 1.49 to 5.64, respectively). CONCLUSION: Changes in DRRS during a PEEP trial in ARDS patients could be monitored using EIT, based on changes in ΔZmL/EELIml and ∆ZAU. The relative change ∆ZAU offers the advantage of not requiring CT data for calibration.

Continuous prolonged prone positioning in COVID-19-related ARDS: a multicenter cohort study from Chile.

BACKGROUND: Prone positioning is currently applied in time-limited daily sessions up to 24 h which determines that most patients require several sessions. Although longer prone sessions have been reported, there is scarce evidence about the feasibility and safety of such approach. We analyzed feasibility and safety of a continuous prolonged prone positioning strategy implemented nationwide, in a large cohort of COVID-19 patients in Chile. METHODS: Retrospective cohort study of mechanically ventilated COVID-19 patients with moderate-to-severe acute respiratory distress syndrome (ARDS), conducted in 15 Intensive Care Units, which adhered to a national protocol of continuous prone sessions ≥ 48 h and until PaO2:FiO2 increased above 200 mm Hg. The number and extension of prone sessions were registered, along with relevant physiologic data and adverse events related to prone positioning. The cohort was stratified according to the first prone session duration: Group A, 2-3 days; Group B, 4-5 days; and Group C, > 5 days. Multivariable regression analyses were performed to assess whether the duration of prone sessions could impact safety. RESULTS: We included 417 patients who required a first prone session of 4 (3-5) days, of whom 318 (76.3%) received only one session. During the first prone session the main adverse event was grade 1-2 pressure sores in 97 (23.9%) patients; severe adverse events were infrequent with 17 non-scheduled extubations (4.2%). 90-day mortality was 36.2%. Ninety-eight patients (24%) were classified as group C; they exhibited a more severe ARDS at baseline, as reflected by lower PaO2:FiO2 ratio and higher ventilatory ratio, and had a higher rate of pressure sores (44%) and higher 90-day mortality (48%). However, after adjustment for severity and several relevant confounders, prone session duration was not associated with mortality or pressure sores. CONCLUSIONS: Nationwide implementation of a continuous prolonged prone positioning strategy for COVID-19 ARDS patients was feasible. Minor pressure sores were frequent but within the ranges previously described, while severe adverse events were infrequent. The duration of prone session did not have an adverse effect on safety.

Inflammatory biomarkers and pendelluft magnitude in ards patients transitioning from controlled to partial support ventilation.

The transition from controlled to partial support ventilation is a challenge in acute respiratory distress syndrome (ARDS) patients due to the risks of patient-self-inflicted lung injury. The magnitude of tidal volume (VT) and intrapulmonary dyssynchrony (pendelluft) are suggested mechanisms of lung injury. We conducted a prospective, observational, physiological study in a tertiary academic intensive care unit. ARDS patients transitioning from controlled to partial support ventilation were included. On these, we evaluated the association between changes in inflammatory biomarkers and esophageal pressure swing (ΔPes), transpulmonary driving pressure (ΔPL), VT, and pendelluft. Pendelluft was defined as the percentage of the tidal volume that moves from the non-dependent to the dependent lung region during inspiration, and its frequency at different thresholds (- 15, - 20 and - 25%) was also registered. Blood concentrations of inflammatory biomarkers (IL-6, IL-8, TNF-α, ANGPT2, RAGE, IL-18, Caspase-1) were measured before (T0) and after 4-h (T4) of partial support ventilation. Pendelluft, ΔPes, ΔPL and VT were recorded. Nine out of twenty-four patients (37.5%) showed a pendelluft mean ≥ 10%. The mean values of ΔPes, ΔPL, and VT were - 8.4 [- 6.7; - 10.2] cmH2O, 15.2 [12.3-16.5] cmH2O and 8.1 [7.3-8.9] m/kg PBW, respectively. Significant associations were observed between the frequency of high-magnitude pendelluft and IL-8, IL-18, and Caspase-1 changes (T0/T4 ratio). These results suggest that the frequency of high magnitude pendelluft may be a potential determinant of inflammatory response related to inspiratory efforts in ARDS patients transitioning to partial support ventilation. Future studies are needed to confirm these results.

Impacto de la Pandemia por SARS-CoV-2 en el Perfil de Ingreso y Egreso de una Unidad de Cuidados Intensivos según Escala de Categorización Kinesiológica / Impact of the SARS-CoV-2 Pandemic on the Admission and Discharge Profile of an Intensive Care Unit according to the Kinesiological Categorization Scale

Introducción. La pandemia por coronavirus trajo consigo una modificación y una reestructuración de las unidades de cuidados intensivos(UCI). Además se produjo un cambio en el perfil de pacientes que ingresan y egresan en estas unidades. Objetivo. Valorar el impacto de la presente pandemia en el perfil de ingreso y egreso de pacientes en UCI según escala de categorización kinesiológica de la unidad. Métodos. Estudio observacional descriptivo que incluyó 50 sujetos de UCI que contaran con escala de categorización kinesiológica (ECK) al ingreso y egreso de la unidad. La ECK contemplo 3 item de evaluación: Función ventilatoria, manejod e secreciones, grado de cooperación y nivel de actividad. El registro de la ECK se planteó de manera retrospectiva para los periodos Julio-agosto 2018 (prepandemia) y Julio - Agosto 2020 (pandemia). Se utilizó estadística descriptiva, utilizando porcentaje y/o promedio para cada variable según corresponda. Resultados. Al observar la función ventilatoria, el requerimiento de soporte ventilatorio varió de un 64% a un 16% pre ­ pandemia, y de un 100% a un 88% durante la pandemia. Respecto al manejo de secreciones, se observó que los sujetos con tos efectiva varío desde un 60% a un 22% en el periodo pandemia Por otra parte, los pacientes que requirieron succión traqueal de manera constante en pandemia, se mantuvo. entre un 88% a un 92% durante la estadía en UCI. En relación al grado de cooperación, un 78% de los pacientes con COVID-19 ingresó con una dependencia severa o nula cooperación, y al momento del egreso de UCI un 54% se mantenía en la misma condición. Respecto al nivel de actividad, durante el periodo pandemia, un 100% de los ingresos y un 96% de los egresos presentó dependencia total. Conclusión. La pandemia causada por SARS-CoV-2 ha influido directamente en el perfil de ingreso y egreso de pacientes UCI, lo cual enfrentó al personal de salud a un aumento considerable en la carga de trabajo.

Introduction. The coronavirus led to a modification and a building of new intensive care units (ICU). In addition, there was a change in the profile of patients admitted and discharged from these units. Objetive. Assess the impact of this pandemy on the admission and discharge profile of patients in the ICU according to a kinesiological categorization scale of the unit. Methods. Descriptive observational study that included 50 ICU subjects who had a Kinesiology Categorization Scale (ECK) at admission and discharge from the unit. The ECK contemplates 3 evaluation elements: ventilatory function, management and secretions, degree of cooperation and level of activity. The ECK registry was considered retrospectively for the periods July-August 2018 (pre-pandemy) and July-August 2020 (pandemy). Descriptive statistics was developed, using percentage and/or average for each variable as appropriate. Results: Looking at ventilatory function, the requirement for ventilatory support varied from 64% to 16% pre-pandemic, and from 100% to 88% during the pandemic. Regarding the management of secretions, it was shown that the subjects with effective cough varied from 60% to 22% in the pandemic period. On the other hand, the patients who required tracheal suctioning constantly in the pandemic were maintained. between 88% and 92% during the ICU stay. Regarding the degree of cooperation, 78% of the patients with COVID-19 were admitted with a severe dependency or no cooperation, and at the time of discharge from the ICU, 54% were pressed in the same condition. Regarding the level of activity, during the pandemic period, 100% of income and 96% of expenses presented total dependency. Conclusion. The pandemy caused by SARS-CoV-2 has directly influenced the admission and discharge profile of ICU patients, which confronted health personnel with a considerable increase in workload.

Relationship Between Endothelial and Angiogenesis Biomarkers Envisage Mortality in a Prospective Cohort of COVID-19 Patients Requiring Respiratory Support.

Purpose: Endothelial damage and angiogenesis are fundamental elements of neovascularisation and fibrosis observed in patients with coronavirus disease 2019 (COVID-19). Here, we aimed to evaluate whether early endothelial and angiogenic biomarkers detection predicts mortality and major cardiovascular events in patients with COVID-19 requiring respiratory support. Methods: Changes in serum syndecan-1, thrombomodulin, and angiogenic factor concentrations were analysed during the first 24 h and 10 days after COVID-19 hospitalisation in patients with high-flow nasal oxygen or mechanical ventilation. Also, we performed an exploratory evaluation of the endothelial migration process induced by COVID-19 in the patients' serum using an endothelial cell culture model. Results: In 43 patients, mean syndecan-1 concentration was 40.96 ± 106.9 ng/mL with a 33.9% increase (49.96 ± 58.1 ng/mL) at day 10. Both increases were significant compared to healthy controls (Kruskal-Wallis p < 0.0001). We observed an increase in thrombomodulin, Angiopoietin-2, human vascular endothelial growth factor (VEGF), and human hepatocyte growth factor (HGF) concentrations during the first 24 h, with a decrease in human tissue inhibitor of metalloproteinases-2 (TIMP-2) that remained after 10 days. An increase in human Interleukin-8 (IL-8) on the 10th day accompanied by high HGF was also noted. The incidence of myocardial injury and pulmonary thromboembolism was 55.8 and 20%, respectively. The incidence of in-hospital deaths was 16.3%. Biomarkers showed differences in severity of COVID-19. Syndecan-1, human platelet-derived growth factor (PDGF), VEGF, and Ang-2 predicted mortality. A multiple logistic regression model with TIMP-2 and PDGF had positive and negative predictive powers of 80.9 and 70%, respectively, for mortality. None of the biomarkers predicted myocardial injury or pulmonary thromboembolism. A proteome profiler array found changes in concentration in a large number of biomarkers of angiogenesis and chemoattractants. Finally, the serum samples from COVID-19 patients increased cell migration compared to that from healthy individuals. Conclusion: We observed that early endothelial and angiogenic biomarkers predicted mortality in patients with COVID-19. Chemoattractants from patients with COVID-19 increase the migration of endothelial cells. Trials are needed for confirmation, as this poses a therapeutic target for SARS-CoV-2.

Estimation of changes in cyclic lung strain by electrical impedance tomography: Proof-of-concept study.

RATIONALE: Cyclic strain may be a determinant of ventilator-induced lung injury. The standard for strain assessment is the computed tomography (CT), which does not allow continuous monitoring and exposes to radiation. Electrical impedance tomography (EIT) is able to monitor changes in regional lung ventilation. In addition, there is a correlation between mechanical deformation of materials and detectable changes in its electrical impedance, making EIT a potential surrogate for cyclic lung strain measured by CT (StrainCT ). OBJECTIVES: To compare the global StrainCT with the change in electrical impedance (ΔZ). METHODS: Acute respiratory distress syndrome patients under mechanical ventilation (VT 6 mL/kg ideal body weight with positive end-expiratory pressure 5 [PEEP 5] and best PEEP according to EIT) underwent whole-lung CT at end-inspiration and end-expiration. Biomechanical analysis was used to construct 3D maps and determine StrainCT at different levels of PEEP. CT and EIT acquisitions were performed simultaneously. Multilevel analysis was employed to determine the causal association between StrainCT and ΔZ. Linear regression models were used to predict the change in lung StrainCT between different PEEP levels based on the change in ΔZ. MAIN RESULTS: StrainCT was positively and independently associated with ΔZ at global level (P < .01). Furthermore, the change in StrainCT (between PEEP 5 and Best PEEP) was accurately predicted by the change in ΔZ (R2 0.855, P < .001 at global level) with a high agreement between predicted and measured StrainCT . CONCLUSIONS: The change in electrical impedance may provide a noninvasive assessment of global cyclic strain, without radiation at bedside.

Experiencia de reconversión de un servicio clínico anestésico-quirúrgico en unidad de pacientes críticos COVID-19 en un hospital universitario / Experience of transforming a clinical surgical-anesthetic unit into a COVID-19 critical patient one in a teaching hospital

INTRODUCTION: The experience of restructuring a clinical surgical-anesthetic unit into a critical patient unit in charge of surgical- anesthetic personnel is presented during the period from May to July 2020 in the context of a SARS-CoV-2 pandemic. OBJECTIVES: Describe the unit's restructuring process, considering technical aspects, changes in staff functions, clinical outcomes of the patients, quality indicators obtained and the psychological impact on the healthcare team. MATHERIAL AND METHODS: The strategies implemented by the responsible experts were described (ie: engineering). Clinical data were obtained from an insti- tutional database and electronical medical records. The management of human resources was described using administrative records of the services of anesthesiology, OR and critical patient unit. The psychological impact on the unit staff was evaluated by applying the Maslach questionnaire. The quality of the clinical management of the unit was obtained from the compilation of standardized quality indicators for the critical patient units of the institution. RESULTS: 25 patients were admitted in the unit. The mean age was 62 ± 12 years. About the complications, 52% had pulmonary embolism, 36% had acute kidney injury, and 1 patient died. The prevalence of Burnout Syndrome was 73.6%. The occurrence of adverse events was minimal. DISCUSSION: The transformation of an anesthetic-surgical unit into a COVID critical patient one, demands a complex net of coordinated strategies to allow facing the attention demand with positive clinical results, at the expense of the health care team mental health.

INTRODUCCIÓN: Se presenta la experiencia de reconversión de una unidad de cuidados posanestésicos a una unidad de cuidados intensivos a cargo de personal anestésico-quirúrgico entre mayo y julio de 2020, en contexto de pandemia por SARS-CoV-2. OBJETIVOS: Describir el proceso de reconversión considerando aspectos técnicos, pertinentes al recurso humano, resultados clínicos, indicadores de calidad e impacto psicológico en el equipo de salud. MATERIALES Y MÉTODOS: Se describen las estrategias implementadas por los expertos responsables. Se obtienen datos clínicos desde base de datos institucional y ficha clínica electrónica. Se describe la gestión del recurso humano utilizando registros administrativos de los servicios involucrados. El impacto psicológico en el personal fue evaluado aplicando el cuestionario de Maslach. La calidad de la gestión clínica se obtiene a partir de indicadores de calidad estandarizados para las unidades de pacientes críticos de nuestro establecimiento. RESULTADOS: Se atendieron 25 pacientes en la unidad. La edad promedio fue 62 ± 12 años. El 52% presentó tromboembolismo pulmonar, 36% injuria renal aguda como complicación. Un paciente falleció. La prevalencia de síndrome de Burnout fue de 73,6%. La ocurrencia de eventos adversos fue baja. CONCLUSIONESConclusiones: La reconversión de una unidad anestésico-quirúrgica a una unidad crítica COVID-19, demanda un complejo entramado de estrategias coordinadas que permiten responder a la demanda de atención con resultados clínicos positivos, a expensas del costo de la salud mental del equipo de salud involucrado.