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. 2021 Jun 10:12:683316.
doi: 10.3389/fphys.2021.683316. eCollection 2021.

Nasal High Flow at 25 L/min or Expiratory Resistive Load Do Not Improve Regional Lung Function in Patients With COPD: A Functional CT Imaging Study

Julien G Cohen  1   2 , Ludovic Broche  3 , Mohammed Machichi  4 , Gilbert R Ferretti  1 , Renaud Tamisier  5   6 , Jean-Louis Pépin  5   6 , Sam Bayat  4   6
Affiliations

Nasal High Flow at 25 L/min or Expiratory Resistive Load Do Not Improve Regional Lung Function in Patients With COPD: A Functional CT Imaging Study

Julien G Cohen et al. Front Physiol. .

Abstract

Background: Nasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable chronic obstructive pulmonary disease (COPD) patients.

Methods: In this study, we used non-rigid registration of computed tomography (CT) images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Parametric response maps (Galban et al., 2012) were also computed in each experimental condition. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).

Results: ΔHU was: BL (median, IQR): 85 (67.2, 102.8); NHF: 90.7 (57.4, 97.6); ERL: 74.6 (46.4, 89.6) HU (p = 0.531); and LD: 27.8 (22.3, 39.3); 17.6 (15.4, 27.9); and 20.4 (16.6, 23.6) mm (p = 0.120) in the 3 conditions, respectively. No significant difference in trapping was observed. Respiratory rate significantly decreased with both treatments [BL: 17.3 (16.4, 18.9); NHF: 13.7; ERL: 11.4 (9.6, 13.2) bpm; and p < 0.001].

Conclusion: Neither NHF at 25 L/min nor ERL significantly improved the regional lung ventilation of stable COPD patients with gas trapping, based on functional lung CT imaging. Further study including more subjects is needed to assess the potential effect of NHF on regional lung function at higher flow rates.

Clinical trial registration: www.clinicaltrials.gov/under, identifier NCT03821311.

Keywords: COPD; computed tomography; expiratory resistive loading; image processing; nasal high flow cannula.

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Conflict of interest statement

J-LP has received grants and research funds for other studies from: Air Liquide Foundation, Agiradom, AstraZeneca, Fisher & Paykel, Mutualia, Philips, Resmed, Vitalaire, Boehringer Ingelheim, Jazz Pharmaceuticals, Night Balance, and Sefam. SB received funding from Fisher & Paykel for this study. The funder was involved in the study design, but not the collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. 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.

Figures

FIGURE 1
FIGURE 1
Image processing workflow. Inspiratory and expiratory CT images were segmented using a region growing algorithm. The segmented expiratory image is warped using elastic image registration software to match the inspiratory image. The indices of regional lung ventilation are computed based on the registered and inspiratory images.
FIGURE 2
FIGURE 2
3D rendering of computed regional lung function indices in a sample COPD patient. PRM, parametric response maps; ΔHU, regional attenuation changes from maximal expiration to maximal inspiration; LD, lung displacement; NHF, nasal high flow; and ERL, expiratory resistive loading.
FIGURE 3
FIGURE 3
Respiratory rate in each of 8 COPD patients; BL, baseline; NHF, nasal high flow cannula; and ERL, expiratory resistive loading. *p < 0.05 vs. BL, #p < 0.05 vs. NHF.
See this image and copyright information in PMC

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