Browsing by Author "Benites, Martín H."

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    Association between controlled mechanical ventilation and systemic inflammation in acute hypoxemic respiratory failure: an observational cohort study
    (2025) Bachmann Barrón, María Consuelo; Benites, Martín H.; Oviedo Álvarez, Vanessa Andrea; Hamidi Vadeghani, Majd Niki; Soto Muñoz, Dagoberto Igor; Basoalto Escobar, Roque Ignacio; Cruces, Pablo; Jalil Contreras, Yorschua Frederick; Damiani Rebolledo, L. Felipe; Bugedo Tarraza, Guillermo; Bruhn, Alejandro; Retamal Montes, Jaime
    Background In patients with acute hypoxemic respiratory failure, spontaneous breathing efforts may contribute to patient self-inflicted lung injury through increased ventilation inhomogeneity and systemic inflammation. Whether early transition to controlled mechanical ventilation (CMV) mitigates these effects remains uncertain. Methods This observational, prospective cohort study included 40 ICU patients with acute hypoxemic respiratory failure who initially breathed spontaneously. Based on clinical decisions, patients were managed with either continued spontaneous breathing (SB group, n = 12) or transitioned to CMV (CMV group, n = 28). Arterial blood gases, hemodynamics, plasma cytokines (IL-6 and IL-8), and ventilation distribution via electrical impedance tomography (EIT) were recorded at baseline and after 24 h. In the CMV group, intermediate time points (T2, T6, T12) were also assessed after intubation. The trial was registered in ClinicalTrials.gov (NCT03513809). Results In the CMV group, respiratory rate and heart rate decreased significantly over time. IL-6 levels dropped markedly from 305 ± 938 pg/mL at baseline to 27 ± 58 pg/mL at 24 h (p = 0.0195), accompanied by a significant improvement in oxygenation (PaO₂/FiO₂ from 140 ± 51 to 199 ± 67, p = 0.0004). EIT data showed improved ventilation distribution with increased end-expiratory lung impedance, decreased global inhomogeneity, and a shift in the center of ventilation toward dorsal regions. In contrast, the SB group showed no significant changes over 24 h in gas exchange, systemic inflammation, or EIT-derived parameters. Conclusions In patients with acute hypoxemic respiratory failure initially breathing spontaneously, transition to CMV was associated with reduced IL-6 levels and improved ventilatory homogeneity over 24 h. These exploratory findings indicate that connection to controlled mechanical ventilation was associated with reduced systemic inflammation, a relationship that warrants confirmation in larger prospective studies.
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    Effects of changes in trunk inclination on ventilatory efficiency in ARDS patients: quasi-experimental study
    (2023) Benites, Martín H.; Torres, David; Poblete, Fabián; Labbé, Francisco; Bachmann, María C.; Regueira, Tomas E.; Soto, Leonardo; Ferre, Andrés; Dreyse, Jorge; Retamal Montes, Jaime
    Trunk inclination from semirecumbent head-upright to supine-flat positioning reduces driving pressure and increases respiratory system compliance in patients with acute respiratory distress syndrome (ARDS). These effects are associated with an improved ventilatory ratio and reduction in the partial pressure of carbon dioxide (PaCO2). However, these physiological effects have not been completely studied, and their mechanisms have not yet been elucidated. Therefore, this study aimed to evaluate the effects of a change in trunk inclination from semirecumbent (45°) to supine-flat (10°) on physiological dead space and ventilation distribution in different lung regions. Results: twenty-two ARDS patients on pressure-controlled ventilation underwent three 60-min steps in which trunk inclination was changed from 45° (baseline) to 10° (intervention) and back to 45° (control) in the last step. Tunk inclination from a semirecumbent (45°) to a supine-flat (10°) position resulted in a higher tidal volume [371 (± 76) vs. 433 (± 84) mL (P < 0.001)] and respiratory system compliance [34 (± 10) to 41 (± 12) mL/cmH2O (P < 0.001)]. The CO2 exhaled per minute improved from 191 mL/min (± 34) to 227 mL/min (± 38) (P < 0.001). Accordingly, Bohr’s dead space ratio decreased from 0.49 (± 0.07) to 0.41 (± 0.06) (p < 0.001), and PaCO2 decreased from 43 (± 5) to 36 (± 4) mmHg (p < 0.001). In addition, the impedance ratio, which divides the ventilation activity of the ventral region by the dorsal region ventilation activity in tidal images, dropped from 1.27 (0.83–1.78) to 0.86 (0.51–1.33) (p < 0.001). These results, calculated from functional EIT images, indicated further ventilation activity in the dorsal lung regions. These effects rapidly reversed once the patient was repositioned at 45°. Conclusions: a change in trunk inclination from a semirecumbent (45 degrees) to a supine-flat position (10 degrees) improved Bohr’s dead space ratio and reduced PaCO2 in patients with ARDS. This effect is associated with an increase in tidal volume and respiratory system compliance, along with further favourable impedance ventilation distribution toward the dorsal lung regions. This study highlights the importance of considering trunk inclination as a modifiable determinant of physiological parameters. The angle of trunk inclination is essential information that must be reported in ARDS patients.
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    Physiological and clinical effects of trunk inclination adjustment in patients with respiratory failure: a scoping review and narrative synthesis
    (2024) Benites, Martín H.; Zapata Canivilo, Marcelo; Poblete, Fabian; Labbe, Francisco; Battiato, Romina; Ferre, Andrés; Dreyse, Jorge; Bugedo, Guillermo; Bruhn, Alejandro; Costa, Eduardo L. V.; Retamal, Jaime
    Background Adjusting trunk inclination from a semi-recumbent position to a supine-flat position or vice versa in patients with respiratory failure significantly affects numerous aspects of respiratory physiology including respiratory mechanics, oxygenation, end-expiratory lung volume, and ventilatory efficiency. Despite these observed effects, the current clinical evidence regarding this positioning manoeuvre is limited. This study undertakes a scoping review of patients with respiratory failure undergoing mechanical ventilation to assess the effect of trunk inclination on physiological lung parameters. Methods The PubMed, Cochrane, and Scopus databases were systematically searched from 2003 to 2023. Interventions: Changes in trunk inclination. Measurements: Four domains were evaluated in this study: 1) respiratory mechanics, 2) ventilation distribution, 3) oxygenation, and 4) ventilatory efficiency. Results After searching the three databases and removing duplicates, 220 studies were screened. Of these, 37 were assessed in detail, and 13 were included in the final analysis, comprising 274 patients. All selected studies were experimental, and assessed respiratory mechanics, ventilation distribution, oxygenation, and ventilatory efficiency, primarily within 60 min post postural change. Conclusion In patients with acute respiratory failure, transitioning from a supine to a semi-recumbent position leads to decreased respiratory system compliance and increased airway driving pressure. Additionally, C-ARDS patients experienced an improvement in ventilatory efficiency, which resulted in lower PaCO2 levels. Improvements in oxygenation were observed in a few patients and only in those who exhibited an increase in EELV upon moving to a semi-recumbent position. Therefore, the trunk inclination angle must be accurately reported in patients with respiratory failure under mechanical ventilation.
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    Respiratory effects of trunk inclination in obese and non-obese patients mechanically ventilated for ARDS
    (2025) Benites, Martín H.; Bihari, Shailesh; Battiato, Romina; Bruhn, Alejandro; Bugedo Tarraza, Guillermo; Costa, Eduardo L. V.; Dellamonica, Jean; Guérin, Claude; Langer, Thomas; Marini, John J.; Marrazo, Francesco; Mezidi, Mehdi; Selickman, John; Wiersema, Ubbo F.; Retamal Montes, Jaime
    Background Adjusting trunk inclination in patients with acute respiratory distress syndrome directly affects physiological variables such as respiratory mechanics and PaCO2 levels. These effects may vary according to the body mass index (BMI) due to differences in lung and chest wall mechanics, highlighting the need for further investigation to clarify the clinical relevance of body position across patient subgroups. Methods A secondary analysis compared the physiological effects of increasing trunk inclination angles between mechanically ventilated patients with obesity (BMI ≥ 30 kg/m2) and those without obesity (BMI < 30 kg/m2). Results Data from 159 patients collected across seven individual studies were analyzed. The following physiological changes were observed in response to increased trunk inclination: Sixty-five patients with obesity presented a greater decrease in respiratory system compliance (-7.5 [-10; -5] mL/cmH2O; p < 0.001) compared to ninety-four patients without obesity (-3.5 [-7; -0.08] mL/cmH2O; p = 0.045). Lung compliance decreased in obese patients (-7.8 [-12.4; -3.3] mL/cmH2O; p < 0.001), whereas no significant changes were observed in patients without obesity (-5.9 [-14.2; 2.3] mL/cmH2O; p = 0.160). Chest wall compliance decreased by -42.9 [-63.2; -22.6] mL/cmH2O (p < 0.001) in obese patients and by -47.7 [-95.3; -0.15] mL/cmH2O in non-obese patients (p = 0.049). PaCO2 increased in obese patients by 4.6 [1.4; 7.8] mmHg (p = 0.004) but not in patients without obesity (2.5 [-0.6; 5.6] (p = 0.113). No significant differences were observed in PaO2/FIO2 between phases. Conclusions Increasing the trunk inclination angle during passive ventilation reduces respiratory system, lung, and chest wall compliance. This effect was more pronounced in obese patients. Moreover, only this population exhibited an increase in PaCO2. We acknowledge the methodological heterogeneity across the included studies, which may have influenced the results. Overall, our results highlight the importance of considering BMI as a significant variable that influences individual physiological responses to changes in bed inclination.
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    Ventilation-induced acute kidney injury in acute respiratory failure: Do PEEP levels matter?
    (Springer Nature, 2025) Benites, Martín H.; Suarez-Sipmann, Fernando; Kattan Tala, Eduardo José; Cruces, Pablo; Retamal Montes, Jaime
    Acute Respiratory Distress Syndrome (ARDS) is a leading cause of morbidity and mortality among critically ill patients, and mechanical ventilation (MV) plays a critical role in its management. One of the key parameters of MV is the level of positive end-expiratory pressure (PEEP), which helps to maintain an adequate lung functional volume. However, the optimal level of PEEP remains controversial. The classical approach in clinical trials for identifying the optimal PEEP has been to compare “high” and “low” levels in a dichotomous manner. High PEEP can improve lung compliance and significantly enhance oxygenation but has been inconclusive in hard clinical outcomes such as mortality and duration of MV. This discrepancy could be related to the fact that inappropriately high or low PEEP levels may adversely affect other organs, such as the heart, brain, and kidneys, which could counteract its potential beneficial effects on the lung. Patients with ARDS often develop acute kidney injury, which is an independent marker of mortality. Three primary mechanisms have been proposed to explain lung-kidney crosstalk during MV: gas exchange abnormalities, such as hypoxemia and hypercapnia; remote biotrauma; and hemodynamic changes, including reduced venous return and cardiac output. As PEEP levels increase, lung volume expands to a variable extent depending on mechanical response. This dynamic underlies two potential mechanisms that could impair venous return, potentially leading to splanchnic and renal congestion. First, increasing PEEP may enhance lung aeration, particularly in highly recruitable lungs, where previously collapsed alveoli reopen, increasing lung volume and pleural pressure, leading to vena cava compression, which can contribute to systemic venous congestion and abdominal organ impairment function. Second, in lungs with low recruitability, PEEP elevation may induce minimal changes in lung volume while increasing airway pressure, resulting in alveolar overdistension, vascular compression, and increased pulmonary vascular resistance. Therefore, we propose that high PEEP settings can contribute to renal congestion, potentially impairing renal function. This review underscores the need for further rigorous research to validate these perspectives and explore strategies for optimizing PEEP settings while minimizing adverse renal effects.