RESUMO
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.
RESUMO
Introduction: The use of high-flow nasal oxygen (HFNO) is a simple method that can reduce intubation in patients with hypoxemic acute respiratory failure (ARF). Early and prolonged prone position has demonstrated benefits on mortality in mechanically ventilated patients and on intubation in awake patients with ARF. However, strategies to achieve adherence to awake prone positioning (APP) have not been previously described. Case and outcomes: We present six patients with ARF due to COVID-19 treated with HFNO and APP. The median (p25-75) of PaFiO2 upon admission was 121 (112-175). The average duration of APP on the first day was 16 h (SD 5 h). Duration (median p25-75) in APP for the following 20 days was 13 (10-18) h/day. Several strategies such as the presence of a health care team, recreational activities, adaptation of the circadian rhythm, oral nutritional support, and analgesics were used to improve prone tolerance. None of the patients suffered from delirium, all were ambulating on discharge from the ICU and none require intubation. Conclusion: The case series presented show the feasibility of prolonged use of HFNO and APP in patients with COVID-19 and severe persistent hypoxemia and described strategies to enhance adherence.
RESUMO
BACKGROUND: High-flow nasal cannula (HFNC) enables delivery of humidified gas at high flow while controlling the FIO2 . Although its use is growing in patients with acute respiratory failure, little is known about the impact of HFNC on lung volume. Therefore, we aimed to assess lung volume changes in healthy subjects at different flows and positions. METHODS: This was a prospective physiological study performed in 16 healthy subjects. The changes in lung volumes were assessed by measuring end-expiratory lung impedance by using electrical impedance tomography. All the subjects successively breathed during 5 min in these following conditions: while in a supine position without HFNC (T0) and 3 measurements in a semi-seated position at 45° without HFNC (T1), and with HFNC at a flow of 30 L/min (T2), and 50 L/min (T3). RESULTS: Compared with the supine position, the values of end-expiratory lung impedance significantly increased with the subjects in a semi-seated position. End-expiratory lung impedance significantly increased after HFNC initiation in subjects in a semi-seated position and further increased by increasing flow at 50 L/min. When taking the end-expiratory lung impedance measurement in subjects in a semi-seated position (T1) as reference, the differences among the medians of global end-expiratory lung impedance were statistically significant (P < .001), which amounted to 1.05 units in T1; 1.12 units in T2; and 1.44 units in T3 (P < .05 for all comparisons, Wilcoxon test). The breathing frequency did not differ between the supine and semi-seated position (T0 and T1) but significantly decreased after initiation of HFNC and further decreased at high flow. T0 and T1 were not different (P = .13); whereas there was a statistically significant difference among T1, T2, and T3 (P < .05, post hoc test with Bonferroni correction). CONCLUSIONS: In healthy subjects, the semi-seated position and the use of HFNC increased end-expiratory lung impedance globally. These changes were accompanied by a significant decrease in the breathing frequency.
Assuntos
Oxigenoterapia/métodos , Postura/fisiologia , Adulto , Cânula , Impedância Elétrica , Feminino , Voluntários Saudáveis , Humanos , Medidas de Volume Pulmonar , Masculino , Estudos Prospectivos , Taxa Respiratória , Decúbito Dorsal/fisiologia , Volume de Ventilação PulmonarRESUMO
OBJECTIVE: To demonstrate that among patients with acute respiratory distress syndrome (ARDS), the presence of diffuse alveolar damage (DAD) at histological examination, as compared to its absence, defines a specific subphenotype. METHODS: We studied 149 patients who died in our ICU with the clinical diagnosis of ARDS according to the Berlin Definition (BD) and who had autopsy examination. We compared the change over time of different clinical variables in patients with (n = 49) and without (n = 100) DAD. A predictive model for the presence of DAD was developed and validated in an independent cohort of 57 patients with ARDS and postmortem examination (21 of them with DAD). RESULTS: Patients with DAD, as compared to patients without DAD, had a lower PaO2/FiO2 ratio and dynamic respiratory system compliance, and a higher SOFA score and INR, and were more likely to die of hypoxemia and less likely to die of shock. In multivariate analysis, variables associated with DAD [odds ratio, 95% confidence interval (CI)] were PaO2/FiO2 ratio [0.988 (0.981-0.995)], dynamic respiratory system compliance [0.937 (0.892-0.984)] and age [0.972 (0.946-0.999)]. Areas under the ROC curve (95 % CI) for the classification of DAD using the regression model or the BD were, respectively, 0.74 (0.65-0.82) and 0.64 (0.55-0.72) (p = 0.03). In the validation cohort, the areas under the ROC curve for the diagnosis of DAD were 0.73 (0.56-0.90) and 0.67 (0.54-0.81) for the regression model and the BD, respectively. CONCLUSIONS: The presence of DAD appears to define a specific subphenotype in patients with ARDS. Targeting patients with DAD within the population of patients with the clinical diagnosis of ARDS might be appropriate to find effective therapies for this condition.