Browsing by Author "Oviedo, Vanessa"

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    A machine-learning regional clustering approach to understand ventilator-induced lung injury: a proof-of-concept experimental study
    (2024) Cruces, Pablo; Retamal, Jaime; Damián, Andrés; Lago, Graciela; Blasina, Fernanda; Oviedo, Vanessa; Medina, Tania; Pérez, Agustín; Vaamonde, Lucía; Dapueto, Rosina; González-Dambrauskas, Sebastian; Serra, Alberto; Monteverde-Fernandez, Nicolas; Namías, Mauro; Martínez, Javier; Hurtado, Daniel E.
    Background The spatiotemporal progression and patterns of tissue deformation in ventilator-induced lung injury (VILI) remain understudied. Our aim was to identify lung clusters based on their regional mechanical behavior over space and time in lungs subjected to VILI using machine-learning techniques. Results Ten anesthetized pigs (27±2 kg) were studied. Eight subjects were analyzed. End-inspiratory and endexpiratory lung computed tomography scans were performed at the beginning and after 12 h of one-hit VILI model. Regional image-based biomechanical analysis was used to determine end-expiratory aeration, tidal recruitment, and volumetric strain for both early and late stages. Clustering analysis was performed using principal component analysis and K-Means algorithms. We identifed three diferent clusters of lung tissue: Stable, Recruitable Unstable, and Non-Recruitable Unstable. End-expiratory aeration, tidal recruitment, and volumetric strain were signifcantly diferent between clusters at early stage. At late stage, we found a step loss of end-expiratory aeration among clusters, lowest in Stable, followed by Unstable Recruitable, and highest in the Unstable Non-Recruitable cluster. Volumetric strain remaining unchanged in the Stable cluster, with slight increases in the Recruitable cluster, and strong reduction in the Unstable Non-Recruitable cluster. Conclusions VILI is a regional and dynamic phenomenon. Using unbiased machine-learning techniques we can identify the coexistence of three functional lung tissue compartments with diferent spatiotemporal regional biomechanical behavior.
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    Capillary refill time response to a fluid challenge or a vasopressor test: an observational, proof-of-concept study
    (2024) Hernández, Glenn; Valenzuela, Emilio Daniel; Kattan, Eduardo; Castro, Ricardo; Guzmán, Camila; Kraemer, Alicia Elzo; Sarzosa, Nicolás; Alegria, Leyla; Contreras, Roberto; Oviedo, Vanessa; Bravo, Sebastián; Soto, Dagoberto; Sáez, Claudia; Ait-Oufella, Hafid; Ospina Tascón, Gustavo; Bakker, Jan
    Background: Several studies have validated capillary refill time (CRT) as a marker of tissue hypoperfusion, and recent guidelines recommend CRT monitoring during septic shock resuscitation. Therefore, it is relevant to further explore its kinetics of response to short-term hemodynamic interventions with fluids or vasopressors. A couple of previous studies explored the impact of a fluid bolus on CRT, but little is known about the impact of norepinephrine on CRT when aiming at a higher mean arterial pressure (MAP) target in septic shock. We designed this observational study to further evaluate the effect of a fluid challenge (FC) and a vasopressor test (VPT) on CRT in septic shock patients with abnormal CRT after initial resuscitation. Our purpose was to determine the effects of a FC in fluid-responsive patients, and of a VPT aimed at a higher MAP target in chronically hypertensive fluid-unresponsive patients on the direction and magnitude of CRT response. Methods Thirty-four septic shock patients were included. Fluid responsiveness was assessed at baseline, and a FC (500 ml/30 mins) was administered in 9 fluid-responsive patients. A VPT was performed in 25 patients by increasing norepinephrine dose to reach a MAP to 80–85 mmHg for 30 min. Patients shared a multimodal perfusion and hemodynamic monitoring protocol with assessments at at least two time-points (baseline, and at the end of interventions). Results CRT decreased significantly with both tests (from 5 [3.5–7.6] to 4 [2.4–5.1] sec, p = 0.008 after the FC; and from 4.0 [3.3–5.6] to 3 [2.6 -5] sec, p = 0.03 after the VPT. A CRT-response was observed in 7/9 patients after the FC, and in 14/25 pts after the VPT, but CRT deteriorated in 4 patients on this latter group, all of them receiving a concomitant low-dose vasopressin. Conclusions Our findings support that fluid boluses may improve CRT or produce neutral effects in fluid-responsive septic shock patients with persistent hypoperfusion. Conversely, raising NE doses to target a higher MAP in previously hypertensive patients elicits a more heterogeneous response, improving CRT in the majority, but deteriorating skin perfusion in some patients, a fact that deserves further research.
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    Effects of capillary refill time-vs. lactate-targeted fluid resuscitation on regional, microcirculatory and hypoxia-related perfusion parameters in septic shock: a randomized controlled trial
    (2020) Castro López, Ricardo; Kattan Tala, Eduardo José; Valenzuela, Emilio Daniel; Alegría, Leyla; Oviedo, Vanessa; Soto, Dagoberto; Vera Alarcón, María Magdalena; Bravo Morales, Sebastián; Bakker, Jan; Hernández P., Glenn
    Abstract Background Persistent hyperlactatemia has been considered as a signal of tissue hypoperfusion in septic shock patients, but multiple non-hypoperfusion-related pathogenic mechanisms could be involved. Therefore, pursuing lactate normalization may lead to the risk of fluid overload. Peripheral perfusion, assessed by the capillary refill time (CRT), could be an effective alternative resuscitation target as recently demonstrated by the ANDROMEDA-SHOCK trial. We designed the present randomized controlled trial to address the impact of a CRT-targeted (CRT-T) vs. a lactate-targeted (LAC-T) fluid resuscitation strategy on fluid balances within 24 h of septic shock diagnosis. In addition, we compared the effects of both strategies on organ dysfunction, regional and microcirculatory flow, and tissue hypoxia surrogates. Results Forty-two fluid-responsive septic shock patients were randomized into CRT-T or LAC-T groups. Fluids were administered until target achievement during the 6 h intervention period, or until safety criteria were met. CRT-T was aimed at CRT normalization (≤ 3 s), whereas in LAC-T the goal was lactate normalization (≤ 2 mmol/L) or a 20% decrease every 2 h. Multimodal perfusion monitoring included sublingual microcirculatory assessment; plasma-disappearance rate of indocyanine green; muscle oxygen saturation; central venous-arterial pCO2 gradient/ arterial-venous O2 content difference ratio; and lactate/pyruvate ratio. There was no difference between CRT-T vs. LAC-T in 6 h-fluid boluses (875 [375–2625] vs. 1500 [1000–2000], p = 0.3), or balances (982[249–2833] vs. 15,800 [740–6587, p = 0.2]). CRT-T was associated with a higher achievement of the predefined perfusion target (62 vs. 24, p = 0.03). No significant differences in perfusion-related variables or hypoxia surrogates were observed. Conclusions CRT-targeted fluid resuscitation was not superior to a lactate-targeted one on fluid administration or balances. However, it was associated with comparable effects on regional and microcirculatory flow parameters and hypoxia surrogates, and a faster achievement of the predefined resuscitation target. Our data suggest that stopping fluids in patients with CRT ≤ 3 s appears as safe in terms of tissue perfusion. Clinical Trials: ClinicalTrials.gov Identifier: NCT03762005 (Retrospectively registered on December 3rd 2018)
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    Hypoxia-related parameters during septic shock resuscitation: Pathophysiological determinants and potential clinical implications
    (AME PUBL CO, 2020) Pavez, Nicolas; Kattan, Eduardo; Vera, Magdalena; Ferri, Giorgio; Daniel Valenzuela, Emilio; Alegria, Leyla; Bravo, Sebastian; Pairumani, Ronald; Santis, Cesar; Oviedo, Vanessa; Soto, Dagoberto; Ospina Tascon, Gustavo; Bakker, Jan; Hernandez, Glenn; Castro, Ricardo
    Background: Assessment of tissue hypoxia at the bedside has yet to be translated into daily clinical practice in septic shock patients. Perfusion markers are surrogates of deeper physiological phenomena. Lactate-to-pyruvate ratio ( LPR) and the ratio between veno-arterial PCO2 difference and Ca-vO(2) (Delta PCO2/Ca-vO(2)) have been proposed as markers of tissue hypoxia, but they have not been compared in the clinical scenario. We studied acute septic shock patients under resuscitation. We wanted to evaluate the relationship of these hypoxia markers with clinical and biochemical markers of hypoperfusion during septic shock resuscitation.
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    Physiological effects of high-flow nasal cannula oxygen therapy after extubation: a randomized crossover study
    (2023) Basoalto Escobar, Roque Ignacio; Damiani Rebolledo, L. Felipe; Jalil, Yorschua; Bachmann, María Consuelo; Oviedo, Vanessa; Alegría Vargas, Leyla; Valenzuela, Emilio Daniel; Rovegno Echavarria, Maxiliano; Ruiz-Rudolph, Pablo; Cornejo, Rodrigo; Retamal Montes, Jaime; Bugedo Tarraza, Guillermo; Thille, Arnaud W.; Bruhn, Alejandro
    Abstract: Background: Prophylactic high-flow nasal cannula (HFNC) oxygen therapy can decrease the risk of extubation failure. It is frequently used in the postextubation phase alone or in combination with noninvasive ventilation. However, its physiological effects in this setting have not been thoroughly investigated. The aim of this study was to determine comprehensively the effects of HFNC applied after extubation on respiratory effort, diaphragm activity, gas exchange, ventilation distribution, and cardiovascular biomarkers. Methods: This was a prospective randomized crossover physiological study in critically ill patients comparing 1 h of HFNC versus 1 h of standard oxygen after extubation. The main inclusion criteria were mechanical ventilation for at least 48 h due to acute respiratory failure, and extubation after a successful spontaneous breathing trial (SBT). We measured respiratory effort through esophageal/transdiaphragmatic pressures, and diaphragm electrical activity (ΔEAdi). Lung volumes and ventilation distribution were estimated by electrical impedance tomography. Arterial and central venous blood gases were analyzed, as well as cardiac stress biomarkers. Results: We enrolled 22 patients (age 59 ± 17 years; 9 women) who had been intubated for 8 ± 6 days before extubation. Respiratory effort was significantly lower with HFNC than with standard oxygen therapy, as evidenced by esophageal pressure swings (5.3 [4.2–7.1] vs. 7.2 [5.6–10.3] cmH2O; p < 0.001), pressure–time product (85 [67–140] vs. 156 [114–238] cmH2O*s/min; p < 0.001) and ΔEAdi (10 [7–13] vs. 14 [9–16] µV; p = 0.022). In addition, HFNC induced increases in end-expiratory lung volume and PaO2/FiO2 ratio, decreases in respiratory rate and ventilatory ratio, while no changes were observed in systemic hemodynamics, Troponin T, or in amino-terminal pro-B-type natriuretic peptide. Conclusions: Prophylactic application of HFNC after extubation provides substantial respiratory support and unloads respiratory muscles.
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    Physiological effects of high-flow nasal cannula oxygen therapy after extubation: a randomized crossover study
    (Springer Open, 2023) Basoalto Escobar, Roque Ignacio; Damiani Rebolledo, L. Felipe; Jalil Contreras, Yorschua Frederick; Bachmann Barrón, Maria Consuelo; Oviedo, Vanessa; Alegria Vargas, Leyla; Valenzuela Espinoza Emilio Daniel; Rovegno Echavarria, David Maximiliano; Ruiz-Rudolph, Pablo; Cornejo, Rodrigo; Retamal Montes, Jaime; Bugedo Tarraza, Guillermo; Thille, Arnaud W.; Bruhn, Alejandro
    Background: Prophylactic high-flow nasal cannula (HFNC) oxygen therapy can decrease the risk of extubation failure. It is frequently used in the postextubation phase alone or in combination with noninvasive ventilation. However, its physiological effects in this setting have not been thoroughly investigated. The aim of this study was to determine comprehensively the effects of HFNC applied after extubation on respiratory effort, diaphragm activity, gas exchange, ventilation distribution, and cardiovascular biomarkers. Methods: This was a prospective randomized crossover physiological study in critically ill patients comparing 1 h of HFNC versus 1 h of standard oxygen after extubation. The main inclusion criteria were mechanical ventilation for at least 48 h due to acute respiratory failure, and extubation after a successful spontaneous breathing trial (SBT). We measured respiratory effort through esophageal/transdiaphragmatic pressures, and diaphragm electrical activity (ΔEAdi). Lung volumes and ventilation distribution were estimated by electrical impedance tomography. Arterial and central venous blood gases were analyzed, as well as cardiac stress biomarkers. Results: We enrolled 22 patients (age 59 ± 17 years; 9 women) who had been intubated for 8 ± 6 days before extubation. Respiratory effort was significantly lower with HFNC than with standard oxygen therapy, as evidenced by esophageal pressure swings (5.3 [4.2–7.1] vs. 7.2 [5.6–10.3] cmH2O; p < 0.001), pressure–time product (85 [67–140] vs. 156 [114–238] cmH2O*s/min; p < 0.001) and ΔEAdi (10 [7–13] vs. 14 [9–16] µV; p = 0.022). In addition, HFNC induced increases in end-expiratory lung volume and PaO2/FiO2 ratio, decreases in respiratory rate and ventilatory ratio, while no changes were observed in systemic hemodynamics, Troponin T, or in amino-terminal pro-B-type natriuretic peptide. Conclusions: Prophylactic application of HFNC after extubation provides substantial respiratory support and unloads respiratory muscles. Trial registration January 15, 2021. NCT04711759.
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    Reduction of Respiratory Rate in COVID-19-Associated ARDS
    (2022) Damiani, L. Felipe; Oviedo, Vanessa; Alegria, Leyla; Soto, Dagoberto; Basoalto, Roque; Consuelo Bachmann, M.; Jalil Contreras, Yorschua Frederick; Santis, Cesar; Vera, Magdalena; Retamal, Jaime; Bruhn, Alejandro; Bugedo, Guillermo
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    Spontaneous breathing promotes lung injury in an experimental model of alveolar collapse
    (2022) Bachmann, María Consuelo; Cruces, Pablo; Díaz, Franco; Oviedo, Vanessa; Goich, Mariela; Fuenzalida, José; Damiani Rebolledo, L. Felipe; Basoalto, Roque; Jalil, Yorschua F.; Carpio Cordero, David; Hamidi Vadeghani, Niki; Cornejo, Rodrigo; Rovegno Echavarria, Maximiliano; Bugedo Tarraza, Guillermo; Bruhn, Alejandro; Retamal Montes, Jaime
    Vigorous spontaneous breathing has emerged as a promotor of lung damage in acute lung injury, an entity known as “patient self-inflicted lung injury”. Mechanical ventilation may prevent this second injury by decreasing intrathoracic pressure swings and improving regional air distribution. Therefore, we aimed to determine the effects of spontaneous breathing during the early stage of acute respiratory failure on lung injury and determine whether early and late controlled mechanical ventilation may avoid or revert these harmful effects. A model of partial surfactant depletion and lung collapse was induced in eighteen intubated pigs of 32 ±4 kg. Then, animals were randomized to (1) SB‐group: spontaneous breathing with very low levels of pressure support for the whole experiment (eight hours), (2) Early MV-group: controlled mechanical ventilation for eight hours, or (3) Late MV-group: first half of the experiment on spontaneous breathing (four hours) and the second half on controlled mechanical ventilation (four hours). Respiratory, hemodynamic, and electric impedance tomography data were collected. After the protocol, animals were euthanized, and lungs were extracted for histologic tissue analysis and cytokines quantification. SB-group presented larger esophageal pressure swings, progressive hypoxemia, lung injury, and more dorsal and inhomogeneous ventilation compared to the early MV-group. In the late MV-group switch to controlled mechanical ventilation improved the lung inhomogeneity and esophageal pressure swings but failed to prevent hypoxemia and lung injury. In a lung collapse model, spontaneous breathing is associated to large esophageal pressure swings and lung inhomogeneity, resulting in progressive hypoxemia and lung injury. Mechanical ventilation prevents these mechanisms of patient self-inflicted lung injury if applied early, before spontaneous breathing occurs, but not when applied late.