FiO2 prediction formula during low flow oxygen therapy in an adult model: a bench study.

During low-flow oxygen therapy, the true value of inspired oxygen fraction (FiO2) is generally unknown. Knowledge of delivered FiO2 values may be useful as well as to adjust oxygen therapy, as well as to predict patient deterioration. This study proposes a New FiO2 Prediction Formula (NFiO2) for low-flow oxygenation and compares its predictive value to precedent formulas. In a bench study, the O2 Flow rate was delivered through a T-piece connected to a dual-compartment artificial lung controlled by a mechanical ventilator. To test the NFiO2 formula, a set of ventilatory parameters were tested: Tidal Volume was set from 400 to 600 ml, Respiratory Rate (RR) was set from 18 to 30 CPM, Ti/Ttot was set at 0.33 and 0.25, and O2 flow rates from 3 to 10 L/min. A data acquisition system measured all parameters. To quantify the accuracy of the NFiO2 compared to other FiO2 prediction formulas, Bland and Altman agreement analyses were performed. To make use of the Duprez Formula 2018 in clinical practice, we simplified the formula to estimate the FiO2 during oxygenation at low flow. This NFiO2 formula makes use of only O2 Flow Rate and RR. Bias and limits of agreement between predicted FiO2 and benchtop FiO2 highlighted consistent differences between different FiO2 prediction formulas. The NFiO2 and the Duprez Formula 2018 seemed to be the most accurate formulas, followed by the Vincent Formula, and lastly the Shapiro Formula. A New FiO2 Prediction Formula was developed using clinical readily available variables (RR and O2 Flow rate) which showed good accuracy in predicting FiO2 during oxygenation at low flow.

Validation of Baveno VI and Expanded-Baveno VI Criteria for predicting gastroesophageal varices in patients with alcoholic and non-alcoholic fatty liver disease.

Background and aims: Baveno VI and Expanded-Baveno VI Criteria were validated to rule out high-risk esophageal varices (HRV) and to prevent unneeded endoscopies in compensated advanced chronic liver disease (cACLD) mainly related to viral hepatitis. We aim to assess these criteria to rule out low- and high- risk varices in patients with cACLD secondary to alcoholic liver disease (ALD) and non- alcoholic fatty liver disease (NAFLD). Methods: Data were collected retrospectively from 2016 to 2020. Inclusion criteria were: NAFLD and /or ALD related cACLD, a liver stiffness measurement (LSM) ≥ 10 kPa and an esophagogastroduodenoscopy (EGD) within 12 months. Exclusion criteria were: use of non cardioselective ß-blockers, hepatic decompensation, previous variceal bleeding, portal thrombosis, liver cancer, or liver transplant. Results: One hundred and ninety-four patients were included in this study. Eighty-one patients (42%) met Baveno VI criteria and 103 (53%) met Expanded-Baveno VI criteria. Baveno VI criteria yielded a high negative predictive value (NPV ≥ 95%) for detecting HRV and varices of any size. Expanded-Baveno VI criteria yielded a high NPV ≥ 95% only for detecting HRV: the miss rate for varices of any size was 8%. Expanded-Baveno VI criteria could avoid more endoscopies than the original Baveno VI criteria to rule out HRV (53% versus 42%). Conclusion: In this study, both criteria showed high NPV to rule out HRV but only original Baveno VI criteria yielded a satisfactory high NPV to rule out varices of any size. Expanded-Baveno VI criteria could avoid more endoscopies to exclude HRV.

High-flow nasal cannula therapy, factors affecting effective inspired oxygen fraction: an experimental adult bench model.

Oxygenation through High Flow Delivery Systems (HFO) is described as capable of delivering accurate FiO2. Meanwhile, peak inspiratory flow [Formula: see text] ) of patients with acute hypoxemic respiratory failure can reach up to 120 L/min, largely exceeding HFO flow. Currently, very few data on the reliability of HFO devices at these high [Formula: see text] are available. We sought to evaluate factors affecting oxygenation while using HFO systems at high [Formula: see text] in a bench study. Spontaneous breathing was generated with a mechanical test lung connected to a mechanical ventilator Servo-i®, set to volume control mode. Gas flow from a HFO device was delivered to the test lung. The influence on effective inspired oxygen fraction of three parameters (FiO2 0.6, 0.8, and 1, [Formula: see text] from 28 to 98.1 L/min, and HFO Gas Flows from 40 to 60 L/min) were analyzed and are reported. The present bench study demonstrates that during HFO treatment, measured FiO2 in the lung does not equal set FiO2 on the device. The substance of this variation (ΔFiO2) is tightly correlated to [Formula: see text] (Pearson's coefficient of 0.94, p-value < 0.001). Additionally, set FiO2 and Flow at HFO device appear to significatively affect ΔFiO2 as well (p-values < 0.001, adjusted to [Formula: see text] ). The result of multivariate linear regression indicates predictors ([Formula: see text] , Flow and set FiO2) to explain 92% of the variance of delta FiO2 through K-Fold Cross Validation. Moreover, adjunction of a dead space in the breathing circuit significantly decreased ΔFiO2 (p < 0.01). The present bench study did expose a weakness of HFO devices in reliability of delivering accurate FIO2 at high [Formula: see text] as well as, to a lesser extent, at [Formula: see text] below equivalent set HFO Flows. Moreover, set HFO flow and set FIO2 did influence the variability of effective inspired oxygen fraction. The adjunction of a dead space in the experimental set-up significantly amended this variability and should thus be further studied in order to improve success rate of HFO therapy.