Benefits of secretion clearance with high frequency percussive ventilation in tracheostomized critically ill patients: a pilot study

Abstract

Clearance of secretions remains a challenge in ventilated patients. Despite high-frequency percussive ventilation (HFPV) showing benefits in patients with cystic fibrosis and neuromuscular disorders, very little is known about its effects on other patient categories. Therefore, we designed a physiological pilot study investigating the effects on lung aeration and gas exchange of short HFPV cycles in tracheostomized patients undergoing mechanical ventilation. Electrical impedance tomography (EIT) was recorded at baseline (T0) by a belt wrapped around the patient's chest, followed by the HFPV cycle lasting 10 min. EIT data was collected again after the HFPV cycle (T1) as well as after 1 h (T2) and 3 h (T3) from T0. Variation from baseline of end-expiratory lung impedance (∆EELI), tidal variation (TIV) and global inhomogeneity index (GI) were computed. Arterial blood was also taken for gas analysis. HFPV cycle significantly improved the ∆EELI at T1, T2 and T3 when compared to baseline (p < 0.05 for all comparisons). The ratio between arterial partial pressure and inspired fraction of oxygen (PaO₂/FiO₂) also increased after the treatment (p < 0.001 for all comparison) whereas TIV (p = 0.132) and GI (p = 0.114) remained unchanged. Short cycles of HFPV superimposed to mechanical ventilation promoted alveolar recruitment, as suggested by improved ∆EELI, and improved oxygenation in tracheostomized patients with high load of secretion.Trial Registration Prospectively registered on www.clinicaltrials.gov (NCT05200507; dated 6th January 2022).

Keywords: Acute respiratory failure; Chest physiotherapy; Cough; Electrical impedance tomography; High-frequency percussive ventilation; Lung aeration.

Fig. 1

EIT images from one representative patient. Examples of EIT images collected from one representative patient; ∆EELI, TIV and GI are shown at baseline (T0), T1, T2 and T3. Yellow and blue codes indicate EELI loss and increase, respectively. A blue scale code indicates tidal variation, whereas pink scale code indicates lung inhomogeneity. The darker is blue or pink, the highest are the tidal variation or inhomogeneity, respectively. Of note, at T3 purple code represents a not-ventilated area (i.e. the heart). In this patient, EELI significantly increased at T1 (60 mL), T2 (148 mL) and T3 (193 mL). TIV and GI did not significantly change throughout the study protocol. ∆EELI changes from baseline (T0) of end-expiratory lung impedance, TIV tidal impedance variation, GI global inhomogeneity index

Fig. 2

Arterial blood gases. Data (left to the right) in the box (plots) show the pH, the arterial partial pressure of carbon dioxide (PaCO₂) and the ratio between arterial partial pressure to inspired fraction of oxygen (PaO₂/FiO₂) at each time frame of the study protocol. The bottom and top of the box indicate the 25th and 75th percentiles, respectively. The horizontal band close to the middle of the box represents the median, whereas the ends of the whiskers represent the 10th and 90th percentiles. Statistically significant p values are also reported. *p < 0.001 in comparison with T0

Fig. 3

Association for repeated measures between ∆EELI and ∆PaO₂/FiO₂. The relationship between the changes in end-expiratory lung impedance (∆EELI) and difference of PaO₂/FiO₂ from baseline (∆PaO₂/FiO₂) are depicted (R_rm = 0.53, 95%CI (0.222, 0.747); p = 0.002). Every single dot represents one measurement for every patient, whereas every single line represents the association between variables within each patient