Effect of Position Change From the Bed to a Wheelchair on the Regional Ventilation Distribution Assessed by Electrical Impedance Tomography in Patients With Respiratory Failure

Abstract: Background: There is limited knowledge about the effect of position change on regional lung ventilation in patients with respiratory failure. The aim of the study was to examine the physiological alteration of regional lung ventilation during position change from lying in bed to sitting on a wheelchair. Methods: Forty-one patients with respiratory failure who were weaned from ventilators were prospectively enrolled in this study. EIT was used to assess the regional lung ventilation distribution at 4 timepoints (Tbase: baseline, supine position in the bed, T30min: sitting position in the wheelchair after 30 min, T60min: sitting position in the wheelchair after 60 min, Treturn: the same supine position in the bed after position changing). The EIT-based global inhomogeneity (GI) and center of ventilation (CoV) indices were calculated. The EIT images were equally divided into four ventral-to-dorsal horizontal regions of interest (ROIs 1-4). Depending on the improvement in ventilation distribution in dependent regions at T60min (threshold set to 15%), the patients were divided into the dorsal ventilation improved (DVI) and not improved (non-DVI) groups. Results: When patients moved from the bed to a wheelchair, there was a significant and continuous increase of ventilation in the dorsal regions (ROI 3+4: 45.9±12.1, 48.7±11.6, 49.9±12.6, 48.8±10.6 for Tbase, T30min, T60min, and Treturn, respectively; p=0.015) and CoV (48.2±10.1, 50.1±9.2, 50.5±9.6 and 49.5±8.6, p=0.047). In addition, there was a significant decrease in GI at T60min compared to Tbase. The DVI group (n=18) had significantly higher oxygenation levels than did the non-DVI group (n=23) after position changing. ROI4Tbase was significantly negatively correlated with ΔSpO2 (R=0.72, p＜0.001＝. Using a cutoff value of 6.5%, ROI4Tbase had 79.2% specificity and 58.8% sensitivity in indicating the increase in dorsal region related to position change. The corresponding area under the curve was 0.806 (95% CI, 0.677-0.936). Conclusions: Position change may improve ventilation distribution in the study patients. EIT may help to personalize the treatment by identifying the patients benefiting from position change from lying in bed to sitting on a wheelchair.