Comparing Airway Clearance Techniques' Effects on Lung Aeration: Ａ Crossover Trial Using Electrical Impedance Tomography

Background: Ventilator-associated pneumonia is a common infection in medical care settings. High-frequency chest wall oscillation (HFCWO) is frequently used as an airway clearance therapy for patients undergoing invasive mechanical ventilation. Previous studies have demonstrated that HFCWO enhances mucous mobilization and airway clearance. We hypothesize that the therapeutic efficacy of HFCWO exceeds that of chest physiotherapy (CPT) for airway clearance, potentially leading to greater improvements in local lung ventilation in patients. This study aims to compare the effects of HFCWO and CPT on lung aeration, measured using electrical impedance tomography (EIT). Methods: This study was a single-center randomized crossover trial approved by the Internal Review Board of Chang Gung Memorial Hospital. We enrolled patients aged 18 years and older who were intubated due to respiratory failure, subsequently admitted to a medical ICU, and displayed infiltrations on chest x-ray within 48 h. HFCWO and CPT were administered twice daily for two consecutive days in random order, with the treatment modality switched on the following day. HFCWO was administered for 15 min, while CPT was combined with postural drainage and percussion for 10 min on each side of the lung. On both days, EIT monitoring was conducted in the afternoon session before HFCWO/CPT treatment to establish a baseline (T0). Measurements included tidal impedance variation, change in end-expiratory lung impedance, global inhomogeneity index, center of ventilation, and non-ventilated areas. EIT data were recorded for 10 min each session at the end of the treatment (T1) and subsequently at 1 (T2) and 2 h (T3) post-treatment. Statistical analyses were performed using the Mann-Whitney test to compare between groups and the Friedman test to compare different time points within each group. Results: Thirty patients were recruited for the study, with twenty-three completing the protocol for final analysis. The figure displays comparisons of each measurement at different time points. Interestingly, while no significant differences were observed in all EIT data between the two treatments, differences in tidal impedance variance were noted within the HFCWO, indicating a reduced volume after 2 h of treatment. The non-ventilated region was lower at baseline but increased after HFCWO. Conclusions: The study found that airway clearance therapy with HFCWO or CPT resulted in similar therapeutic effects in terms of lung volume changes.Comparisons of EIT paramters between two treatments