Daily ROX index can predict transitioning to mechanical ventilation within the next 24 h in COVID-19 patients on HFNC.

INTRODUCTION: High flow nasal cannula (HFNC) is used to prevent invasive ventilation in COVID-19-associated hypoxemia. The respiratory rate­oxygenation (ROX) index has been reported to predict failure of HFNC in patients with COVID-19 pneumonia during the intensive care unit stay when measured in first hours of therapy. However, the clinical course of ICU patients may change substantially in the first days of admission. The objective of this study was to investigate whether ROX index obtained in the first four days of ICU admission could predict the need for invasive respiratory support within the next 24 h of measurements. METHODS: A retrospective cross-sectional study was performed using a database that included adult patients with COVID-19 pneumonia treated in the ICU. Patients were followed from ICU admission and ROX index was calculated daily on HFNC. Receiver operating characteristics curves (ROCs) were performed. RESULTS: Two hundred forty-nine patients were enrolled, 48% of whom require mechanical ventilation (MV). The area under the ROC of the pooled 4-day values of the ROX index as a predictor of transition from HFNC to MV within 24 h of measurements was 0.86 (95%CI 0.83 to 0.88, P < 0.001) with a cutoff point of 4.06. CONCLUSION: In COVID-19 patients in high flow nasal cannula, daily ROX index measurements successfully predicted transition to mechanical ventilation within the next 24 h.

Positive end-expiratory pressure induced changes in airway driving pressure in mechanically ventilated COVID-19 Acute Respiratory Distress Syndrome patients.

BACKGROUND: The profile of changes in airway driving pressure (dPaw) induced by positive-end expiratory pressure (PEEP) might aid for individualized protective ventilation. Our aim was to describe the dPaw versus PEEP curves behavior in ARDS from COVID-19 patients. METHODS: Patients admitted in three hospitals were ventilated with fraction of inspired oxygen (FiO2) and PEEP initially adjusted by oxygenation-based table. Thereafter, PEEP was reduced from 20 until 6 cmH2O while dPaw was stepwise recorded and the lowest PEEP that minimized dPaw (PEEPmin_dPaw) was assessed. Each dPaw vs PEEP curve was classified as J-shaped, inverted-J-shaped, or U-shaped according to the difference between the minimum dPaw and the dPaw at the lowest and highest PEEP. In one hospital, hyperdistention and collapse at each PEEP were assessed by electrical impedance tomography (EIT). RESULTS: 184 patients (41 including EIT) were studied. 126 patients (68%) exhibited a J-shaped dPaw vs PEEP profile (PEEPmin_dPaw of 7.5 ± 1.9 cmH2O). 40 patients (22%) presented a U (PEEPmin_dPaw of 12.2 ± 2.6 cmH2O) and 18 (10%) an inverted-J profile (PEEPmin_dPaw of 14,6 ± 2.3 cmH2O). Patients with inverted-J profiles had significant higher body mass index (BMI) and lower baseline partial pressure of arterial oxygen/FiO2 ratio. PEEPmin_dPaw was associated with lower fractions of both alveolar collapse and hyperinflation. CONCLUSIONS: A PEEP adjustment procedure based on PEEP-induced changes in dPaw is feasible and may aid in individualized PEEP for protective ventilation. The PEEP required to minimize driving pressure was influenced by BMI and was low in the majority of patients.

Involvement of Respiratory Muscles During the Timed Inspiratory Effort Index Measurement With Surface Electromyography.

BACKGROUND: Mechanical ventilation is a life-support therapy that can be associated with respiratory muscle dysfunction that may perturb the weaning process. The timed inspiratory effort (TIE) index is a recently proposed weaning index that has been reported to be effective in predicting successful weaning. We sought to analyze the respiratory muscle groups involved with the TIE index measurement utilizing the surface electromyography (sEMG). METHODS: We conducted a prospective observational study including 46 mechanically ventilated subjects. The variable analyzed with sEMG was the root mean square (RMS) for correlation with the degree of recruitment of motor units and strength. The data were obtained along the 60 s of the TIE index measurement and analyzed in each one of the 3 20-s intervals. Pooled and individual muscle RMS values were analyzed comparing success and failure groups. P < .05 was considered significant. RESULTS: The median (interquartile range) age of the participants was 80 (71-87) y. The pooled sEMG data showed that muscle strength increased over time, following the profile observed for maximum inspiratory pressure, irrespective of the analyzed group. However, in line with the findings regarding maximum inspiratory pressure, the RMS medians were statistically higher at every 20-s interval in the success group. Diaphragm strength increased over time, with values reaching statistically significant differences at the end of the observation period, but only in the success group. In addition, diaphragm strength was statistically higher during the whole test in the success group. Finally, there was a substantial increase in sternocleidomastoid strength over time after 40 s of observation, which was not observed in the scalene muscles. CONCLUSIONS: Subjects succeeding in a weaning trial had higher muscle strength, confirmed in the pooled and the individual sEMG analysis. A vigorous diaphragm with low fatigue potential seems essential for successful weaning; the sternocleidomastoid may also be of importance in this regard.

Serial Weekly Measurements of the Timed Inspiratory Effort Index Can Predict Successful Prolonged Weaning.

BACKGROUND: Patients who require prolonged weaning from mechanical ventilation represent a major challenge in intensive care, and the timed inspiratory effort (TIE) index has been shown to be a clinically valuable tool to predict weaning success. OBJECTIVE: To evaluate whether weekly serial measurements of the TIE index can predict the success in prolonged weaning. METHODS: A prospective observational study in which the subjects who started the weaning process off mechanical ventilation underwent weekly measurements of the TIE index. The area under the receiver operating characteristic curve was used to evaluate the accuracy of the TIE index as a predictor of weaning success. A multivariate Cox regression model was developed to test the association of TIE index values of ≥1.0 cm H2O/s with a failure of weaning. RESULTS: Seventy subjects were selected. Their median (IQR) age was 72 (62-78) y, the median (IQR) duration of mechanical ventilation was 17.5 (14-28) d, and the median (IQR) APACHE II (Acute Physiology and Chronic Health Evaluation) II score was 28 (24-31). Thirty-five of the 70 subjects (50%) died, 22 of them after successful weaning. A total of 224 tests were performed over 56 d. The area under the receiver operating characteristic curve of the TIE index was 0.93. In the analysis of the probability of success during the follow-up (Kaplan-Meier method), a significant difference was obtained in favor of those with a TIE index of ≥ 1.0 cm H2O/s (53% vs 32%, P = .030). In the multivariate Cox regression analysis, values of the TIE index ≥ 1.0 cm H2O/s revealed an inverse, strong, and independent association with failure (hazard ratio 0.36, 95% CI 0.15-0.91; P = .030). The following variables were also found to have an independent but direct association with failure: age and length of time before weaning. CONCLUSIONS: When measured weekly, a TIE index of ≥1.0 cm H2O/s was a good predictor of success in subjects who required prolonged weaning in our hospital.