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. This study aimed to examine the physiological alteration of regional lung ventilation during the position change from lying in bed to sitting on a wheelchair. Methods: In this study, 41 patients with respiratory failure who were weaned from the ventilators were prospectively enrolled. The electrical impedance tomography (EIT) was used to assess the regional lung ventilation distribution at four time points (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 the 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 the patients moved from the bed to a wheelchair, there was a significant and continuous increase in 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 with Tbase. The DVI group (n = 18) had significantly higher oxygenation levels than the non-DVI group (n = 23) after position changing. ROI4Tbase was significantly negatively correlated with the 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 the dorsal region related to the position change. The corresponding area under the curve (AUC) was 0.806 (95% CI, 0.677-0.936). Conclusions: Position change may improve the ventilation distribution in the study patients. The EIT can visualize real-time changes of the regional lung ventilation at the bedside to guide the body position change of the patients in the intensive care unit (ICU) and measure the effect of clinical practice. 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.

Keywords: bedside monitoring; body position change; early mobilizations; electrical impedance tomography (EIT); regional lung ventilation.

Conflict of interest statement

ZZ receives consultant fees from Draeger Medical. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2021 Yuan, Chi, Long, He and Zhao.

Figures

Figure 1

Evolution of the estimated marginal means of ROI 1–4, GI, and COV at different time points. ROI, region of interest; GI, global inhomogeneity; COV, center of ventilation; p value by general linear model repeated measures. *p < 0.05 indicates a significant difference between this time point and Tbase.

Figure 2

Relationship between ΔROI 3 + 4 and ΔSpO2, ROI 4(base) and ΔROI 3 + 4, and ROI 4(base) and ΔSpO2 in 41 patients. ΔROI 3 + 4 means ROI 3 + 4 at T60min −ROI 3 + 4 at Tbase. ΔSpO2 means SpO2 at T60 min–SpO2 at Tbase. ROI 4(base) means ROI 4 at Tbase. Some data points overlap.

Figure 3

Evolution of the estimated marginal means of ROI 1–4, GI and COV at different time points in two subgroups. GI, global inhomogeneity; COV, center of ventilation; DVI, dorsal-ventilation improved group; Non-DVI, dorsal-ventilation not-improved group. The green line indicates the DVI group and the red line indicates the non-DVI group. p value by general linear model repeated measures. *p < 0.05 indicates a significant difference between this time point and Tbase.

Figure 4

ROC curve using ROI 4(base) to distinguish DVI patients (AUC 0.806).

Figure 5

EIT image from supine position (Tbase) to sitting position on a wheelchair. 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.