Adherence to protective mechanical ventilation in COVID-19 versus non-COVID-19-associated acute respiratory distress syndrome: Comparison between two prospective cohorts

OBJECTIVE

To compare adherence to protective mechanical ventilation (MV) parameters in patients with acute respiratory distress syndrome (ARDS) caused by COVID-19 with patients with ARDS from other etiologies.

DESIGN

Multiple prospective cohort study.

SETTING

Two Brazilian cohorts of ARDS patients were evaluated. One with COVID-19 patients admitted to two Brazilian intensive care units (ICUs) in 2020 and 2021 (C-ARDS, n=282), the other with ARDS-patients from other etiologies admitted to 37 Brazilian ICUs in 2016 (NC-ARDS, n=120).

PATIENTS

ARDS patients under MV.

INTERVENTIONS

None.

MAIN VARIABLES OF INTEREST

Adherence to protective MV (tidal volume ≤8mL/kg PBW; plateau pressure ≤30cmH2O; and driving pressure ≤15cmH2O), adherence to each individual component of the protective MV, and the association between protective MV and mortality.

RESULTS

Adherence to protective MV was higher in C-ARDS than in NC-ARDS patients (65.8% vs. 50.0%, p=0.005), mainly due to a higher adherence to driving pressure ≤15cmH2O (75.0% vs. 62.4%, p=0.02). Multivariable logistic regression showed that the C-ARDS cohort was independently associated with adherence to protective MV. Among the components of the protective MV, only limiting driving pressure was independently associated with lower ICU mortality.

CONCLUSIONS

Higher adherence to protective MV in patients with C-ARDS was secondary to higher adherence to limiting driving pressure. Additionally, lower driving pressure was independently associated with lower ICU mortality, which suggests that limiting exposure to driving pressure may improve survival in these patients.

Impacts of a fraction of inspired oxygen adjustment protocol in COVID-19 patients under mechanical ventilation: A prospective cohort study

OBJECTIVE

We examined weather a protocol for fraction of inspired oxygen (FiO₂) adjustment can reduce hyperoxemia and excess oxygen use in COVID-19 patients mechanically ventilated.

DESIGN

Prospective cohort study.

SETTING

Two intensive care units (ICUs) dedicated to COVID-19 patients in Brazil.

PATIENTS

Consecutive patients with COVID-19 mechanically ventilated.

INTERVENTIONS

One ICU followed a FiO₂ adjustment protocol based on SpO₂ (conservative-oxygen ICU) and the other, which did not follow the protocol, constituted the control ICU.

MAIN VARIABLES OF INTEREST

Prevalence of hyperoxemia (PaO₂>100mmHg) on day 1, sustained hyperoxemia (present on days 1 and 2), and excess oxygen use (FiO₂>0.6 in patients with hyperoxemia) were compared between the two ICUs.

RESULTS

Eighty two patients from the conservative-oxygen ICU and 145 from the control ICU were included. The conservative-oxygen ICU presented lower prevalence of hyperoxemia on day 1 (40.2% vs. 75.9%, p<0.001) and of sustained hyperoxemia (12.2% vs. 49.6%, p<0.001). Excess oxygen use was less frequent in the conservative-oxygen ICU on day 1 (18.3% vs. 52.4%, p<0.001). Being admitted in the control ICU was independently associated with hyperoxemia and excess oxygen use. Multivariable analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FiO₂ use and adverse clinical outcomes.

CONCLUSIONS

Following FiO₂ protocol was associated with lower hyperoxemia and less excess oxygen use. Although those results were not associated with better clinical outcomes, adopting FiO₂ protocol may be useful in a scenario of depleted oxygen resources, as was seen during the COVID-19 pandemic.

Dielectric behavior of epoxy/BaTiO₃ composites using nanostructured ceramic fibers obtained by electrospinning

Composite materials made of epoxy resin and barium titanate (BT) electrospun nanostructured fibers were prepared. BT fibers were synthesized from a sol based on barium acetate, titanium isopropoxide, and poly(vinyl pyrrolidone). The fibers were heat-treated at different temperatures and characterized by X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy. Mats of BT fibers heat-treated at 800 °C were embedded in epoxy resin into suitable molds. The composites were characterized by SEM, and dielectric measurements were performed by means of dielectric spectroscopy. The dielectric permittivity and dielectric modulus of epoxy resin/BT-fiber composites were measured for two types of samples: with the electrodes parallel and perpendicular to the BT fiber layers. Interestingly, composite samples with electrodes perpendicular to the fiber layers and a BT content as low as 2 vol % led to dielectric permittivities three times higher than that of pure epoxy resin.