First Attempt at Using Electrical Impedance Tomography to Predict High Flow Nasal Cannula Therapy Outcomes at an Early Phase

Abstract

Objective: Spatial and temporal ventilation distributions in patients with acute respiratory failure during high flow nasal cannula (HFNC) therapy were previously studied with electrical impedance tomography (EIT). The aim of the study was to explore the possibility of predicting HFNC failure based on various EIT-derived parameters.Methods: High flow nasal cannula failure was defined reintubation within 48 h after HFNC. EIT was performed with the patients spontaneously breathing in the supine position at the start of HFNC. EIT-based indices (comprising the global inhomogeneity index, center of ventilation, ventilation delay, rapid shallow breathing index, minute volume, and inspiration to expiration time) were explored and evaluated at three time points (prior to HFNC, T1; 30 min after HFNC started, T2; and 1 h after, T3).Results: A total of 46 subjects were included in the final analysis. Eleven subjects had failed HFNC. The time to failure was 27.8 ± 12.4 h. The ROX index (defined as SpO2/FiO2/respiratory rate) for HFNC success patients was 8.3 ± 2.7 and for HFNC failure patients, 6.2 ± 1.8 (p = 0.23). None of the investigated EIT-based parameters showed significant differences between subjects with HFNC failure and success. Further subgroup analysis indicated that a significant difference in ventilation inhomogeneity was found between ARDS and non-ARDS [0.54 (0.37) vs. 0.46 (0.28) as evaluated with GI, p < 0.01]. Ventilation homogeneity significantly improved in ARDS after 60-min HFNC treatment [0.59 (0.20) vs 0.57 (0.19), T1 vs. T3, p < 0.05].Conclusion: Spatial and temporal ventilation distributions were slightly but insignificantly different between the HFNC success and failure groups. HFNC failure could not be predicted by changes in EIT temporal and spatial indexes of ventilation distribution within the first hour. Further studies are required to predict the outcomes of HFNC.

Reply to Li et al.

“…On the other hand, more severe patients enrolled in our study, compared with the study by Li and colleagues ( 3 ), might be the main reason for the poor predictive value of ΔMOX after a short time of HFNC (2 h). Compared with the report by Li and colleagues, a higher acute physiologic assessment and chronic health evaluation II score (21 vs. 18) and a higher intubation rate (46.7% vs. 22.9%) were observed in patients in our study.…”

Volume–OXygenation Index to Predict High-flow Nasal Cannula Failure: How to Capture the Tidal Volume Matters

“…In a previous study, we attempted to use EIT for early prediction (within 1 h) of HFNC failure ( 4 ). As inspired by the work ( 1 ), we combined ROX and VOX indices and retrospectively analyzed the data from the previous study ( 4 ) using EIT-based VT and RR (EIT-based min volume [MV]) at 1 hour after HFNC. This parameter ΔEMOX was calculated as follows: …”

Electrical Impedance Tomography in Acute Respiratory Distress Syndrome Management

“…Interestingly, flows higher than 60 L/min were associated with increased ventral ventilation (overdistension) and poor tolerability (72). Favorable changes in lung homogeneity indexes (GI, CoV, and RVD) do not predict HFNC success (73).…”