Nasal High Flow at 25 L/min or Expiratory Resistive Load Do Not Improve Regional Lung Function in Patients With COPD: A Functional CT Imaging Study

BackgroundNasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable chronic obstructive pulmonary disease (COPD) patients.MethodsIn this study, we used non-rigid registration of computed tomography (CT) images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Parametric response maps (Galban et al., 2012) were also computed in each experimental condition. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).ResultsΔHU was: BL (median, IQR): 85 (67.2, 102.8); NHF: 90.7 (57.4, 97.6); ERL: 74.6 (46.4, 89.6) HU (p = 0.531); and LD: 27.8 (22.3, 39.3); 17.6 (15.4, 27.9); and 20.4 (16.6, 23.6) mm (p = 0.120) in the 3 conditions, respectively. No significant difference in trapping was observed. Respiratory rate significantly decreased with both treatments [BL: 17.3 (16.4, 18.9); NHF: 13.7; ERL: 11.4 (9.6, 13.2) bpm; and p < 0.001].ConclusionNeither NHF at 25 L/min nor ERL significantly improved the regional lung ventilation of stable COPD patients with gas trapping, based on functional lung CT imaging. Further study including more subjects is needed to assess the potential effect of NHF on regional lung function at higher flow rates.Clinical Trial Registrationwww.clinicaltrials.gov/under, identifier NCT03821311.

Electrical impedance segmentography: A promising tool for respiratory monitoring?

BACKGROUND: Non-invasive, radiation free bedside monitoring methods have gained increased popularity in the respiratory field. The aim of our study was to report the experience with electrical impedance segmentography (EIS), a rather new technique, which allows continuous visual and quantitative monitoring of regional lung ventilation. METHODS: Prospective, pilot trial in spontaneously breathing, healthy, non-sedated term neonates between 24 and 72 hours post-delivery using a commercially available EIS-device. Systematic review of the literature. RESULTS: A total of 12 neonates were eligible for complete data analysis in our study. EIS was found to be a safe and easy to perform method. The median duration of the study time was 25 minutes (16–40). Individual total and regional impedance values, given in arbitrary units and it's percentage of distribution in the upper and lower right and left lung segments (UR, UL, LR, LL), were variable (median total impedance 207 arbitrary units (AU), UR% 17, LR 27%,UL 28%, LL 23%). A number of influencing factors such as body movements, sucking, jawing, and electrode issues have to be considered for correct data interpretation. The literature search revealed two small experimental studies in neonatal piglets and two human studies (one study in preschool children with bronchopulmonary dysplasia and one case report in a neonate with respiratory distress). CONCLUSIONS: EIS is an innovative technique and a potentially useful tool in studying regional lung ventilation in research and clinical care.

Nasal High Flow at 25 L/min or Expiratory Resistive Load do Not Improve Regional Lung Function in Patients with COPD: A Functional CT Imaging Study

Background: Nasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable COPD patients.Methods: In this study, we used non-rigid registration of CT images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).Results: ΔHU was: BL: 81.7±28.8; NHF: 77.3±28.1; ERL: 70±26.7 HU (p=0.164) and LD: 30.2±12.7; 21.9±10.1 and 20.6±5.8 mm (p=0.044) in the 3 conditions, respectively. Respiratory rate significantly decreased with both treatments (BL:17.6±2.9; NHF:13±3.6; ERL: 11.6±2.8 bpm; p<0.001) while end-expiratory volume tended to increase.Conclusions: Neither NHF at 25 L/min nor ERL significantly improve the regional lung ventilation of stable COPD patients with gas trapping, based on the registration of expiratory and inspiratory CT images. Further studies are needed to assess the potential effect of higher flow rates of NHF.Trial registration: This study was registered with https://clinicaltrials.gov/ under: NCT03821311.

Effect of Early Mobilization from Bed to Wheel Chair on Regional Ventilation Distribution Assessed by Electrical Impedance Tomography in Respiratory Failure Patients

Backgrounds: There was limited knowledge about the effect of early mobilization on regional lung ventilation in patients with respiratory failure. The aim of the study was to examine whether electrical impedance tomography (EIT) could help to predict the improvement in ventilation distribution due to mobilization.Methods: Forty-one patients with respiratory failure, who had weaned from ventilator and received early mobilization were prospectively enrolled in this study. EIT was used to assess regional lung ventilation distributions at 4 timepoints during the early mobilization from bed to wheelchair (Tbase: baseline, supine position at the bed, T30min: sitting position on the wheelchair after 30min, T60min: sitting position on the wheelchair after 60min, Treturn: return to supine position on the bed after early mobilization). The EIT-based global inhomogeneity (GI) and center of ventilation (CoV) indices were calculated. EIT images were equally divided into four ventral-to-dorsal horizontal regions of interest (ROIs 1-4). Depending on the improvement of ventilation distribution in dependent regions at T60min (threshold set to 15%), patients were divided into recruited (DR) and non-recruited (Non-DR) groups. Results: From the bed to the wheelchair, a significant and continuous increase of dependent regional ventilation distribution (ROI 3+4: baseline vs. T30min, vs. T60min: 45.9±12.1 vs. 48.7±11.6 vs. 49.9±12.6, p=0.015) and COV (COV baseline vs. T30min, vs. T60min: 48.2±10.1 vs. 50.1±9.2 vs. 50.5±9.6, p=0.003). Besides, there was a significant decrease of GI at T60min. Patients in the DR group (n=18) had significantly higher oxygenation than the Non-DR group (n=23) after early mobilization. ROI4Tbase was significantly negatively correlated to ΔSpO2 (R=0.72, p＜0.001). Using a cut-off value of 6.5%, ROI4Tbase had a 79.2% specificity and 58.8% sensitivity to predict response of dependent region recruitment due to early mobilization. The corresponding area under curve was 0.806 (95%CI, 0.677-0.936).Conclusions: EIT may be a promising tool to predict the ventilation improvement resulted from early mobilization.Trial registration: Effect of Early Mobilization on Regional Lung Ventilation Assessed by EIT, NCT04081129. Registered 9 June 2019 - Retrospectively registered, https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S00096WT&selectaction=Edit&uid=U00020D9&ts=2&cx=v2cwij