High frequency percussive ventilation increases alveolar recruitment in early acute respiratory distress syndrome: an experimental, physiological and CT scan study

Abstract

Background: High frequency percussive ventilation (HFPV) combines diffusive (high frequency mini-bursts) and convective ventilation patterns. Benefits include enhanced oxygenation and hemodynamics, and alveolar recruitment, while providing hypothetic lung-protective ventilation. No study has investigated HFPV-induced changes in lung aeration in patients with early acute respiratory distress syndrome (ARDS).

Methods: Eight patients with early non-focal ARDS were enrolled and five swine with early non-focal ARDS were studied in prospective computed tomography (CT) scan and animal studies, in a university-hospital tertiary ICU and an animal laboratory. Patients were optimized under conventional "open-lung" ventilation. Lung CT was performed using an end-expiratory hold (Conv) to assess lung morphology. HFPV was applied for 1 hour to all patients before new CT scans were performed with end-expiratory (HFPV EE) and end-inspiratory (HFPV EI) holds. Lung volumes were determined after software analysis. At specified time points, blood gases and hemodynamic data were collected. Recruitment was defined as a change in non-aerated lung volumes between Conv, HFPV EE and HFPV EI. The main objective was to verify whether HFPV increases alveolar recruitment without lung hyperinflation. Correlation between pleural, upper airways and HFPV-derived pressures was assessed in an ARDS swine-based model.

Results: One-hour HFPV significantly improved oxygenation and hemodynamics. Lung recruitment significantly rose by 12.0% (8.5-18.0%), P = 0.05 (Conv-HFPV EE) and 12.5% (9.3-16.8%), P = 0.003 (Conv-HFPV EI). Hyperinflation tended to increase by 2.0% (0.5-2.5%), P = 0.89 (Conv-HFPV EE) and 3.0% (2.5-4.0%), P = 0.27 (Conv-HFPV EI). HFPV hyperinflation correlated with hyperinflated and normally-aerated lung volumes at baseline: r = 0.79, P = 0.05 and r = 0.79, P = 0.05, respectively (Conv-HFPV EE); and only hyperinflated lung volumes at baseline: r = 0.88, P = 0.01 (Conv-HFPV EI). HFPV CT-determined tidal volumes reached 5.7 (1.1-8.1) mL.kg-1 of ideal body weight (IBW). Correlations between pleural and HFPV-monitored pressures were acceptable and end-inspiratory pleural pressures remained below 25cmH20.

Conclusions: HFPV improves alveolar recruitment, gas exchanges and hemodynamics of patients with early non-focal ARDS without relevant hyperinflation. HFPV-derived pressures correlate with corresponding pleural or upper airways pressures.

Trial registration: ClinicalTrials.gov, NCT02510105 . Registered on 1 June 2015. The trial was retrospectively registered.

Keywords: Acute respiratory distress syndrome; Alveolar hyperinflation; Alveolar recruitment; High frequency percussive ventilation; Lung morphology; Mechanical ventilation.

Conflict of interest statement

Ethics approval and consent to participate

Our institutional review board approved the protocol (CPP Sud-Est VI, approval number AU 1138). All participants or their next-of-kin provided written consent to participate in this study. The clinical trial is registered at http://www.clinicaltrials.gov (NCT 02510105).

This study was approved by the National Ethics Committee on animal research (approval number 01505.01), and was carried out in accordance with the International Guiding Principles for Biomedical Research Involving Animals.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Evolution of arterial oxygen tension (PaO2) to inspiratory oxygen fraction (FiO2) ratio and arterial carbon dioxide tension (PaCO2) (upper graphs) and hemodynamic parameters (lower graphs): Mean arterial pressure (MAP) and Norepinephrine doses during the experimental procedure. *P < 0.05 versus time 0 (T0). HFPV high frequency percussive ventilation

Fig. 2

UCLA color encoding of lung computed tomography (CT) attenuation in a patient with non-focal acute respiratory distress syndrome (ARDS) phenotype. Direct visualization of lung aeration was performed after processing CT scan images with CT attenuation color-encoding. In this patient with non-focal ARDS, high frequency percussive ventilation (HFPV) resulted in an important recruitment of non-aerated (red) lung zones, and increasing normally aerated (blue) ones. HFPV allowed large alveolar recruitment and was associated with almost no concomitant hyperinflation (white) of aerated lung regions. Consecutive images were recorded using: (1) an end-expiratory hold during conventional mechanical ventilation, (2) an end-expiratory hold or (3) an end-inspiratory hold during HFPV. Color encoding of CT attenuation: hyperinflation (white), normal aeration (blue), poor aeration (green) and absent aeration (red). CMV conventional mechanical ventilation

Fig. 3

Correlation and Bland and Altman bias between maximal end-inspiratory pleural pressure and high frequency percussive ventilation (HFPV) mean pressures considering all pairs of measurements performed during the study. aN = 58, red line: 95% confidence ellipsis; bN = 58, lines: bias (black dotted) and +2SD/-2SD limits of agreement (red dotted). SD standard deviation

Fig. 4

Evolution of lung volumes under conventional ventilation and high frequency percussive ventilation (HFPV). Abbreviations: conv conventional ventilation, expi expiratory hold during HFPV, inspi inspiratory hold during HFPV, Non non-aerated lung volume, Norm normally aerated lung volume, Over overdistended lung volume, Poor poorly aerated lung volume. Data are presented as percentages of total lung volume. *P < 0.05 versus conventional ventilation