Introduction Non-invasive high-frequency oscillatory ventilation (nHFOV) is an extension of nasal continuous positive airway pressure (nCPAP) support in neonates. We aimed to compare global and regional distribution of lung volumes during nHFOV versus nCPAP.
Methods In 30 preterm infants enrolled in a randomised crossover trial comparing nHFOV with nCPAP, electrical impedance tomography data were recorded in prone position. For each mode of respiratory support, four episodes of artefact-free tidal ventilation, each comprising 30 consecutive breaths, were extracted. Tidal volumes (VT) in 36 horizontal slices, indicators of ventilation homogeneity and end-expiratory lung impedance (EELI) for the whole lung and for four horizontal regions of interest (non-gravity-dependent to gravity-dependent; EELINGD, EELImidNGD, EELImidGD, EELIGD) were compared between nHFOV and nCPAP. Aeration homogeneity ratio (AHR) was determined by dividing aeration in non-gravity-dependent parts of the lung through gravity-dependent regions.
Main results Overall, 228 recordings were analysed. Relative VT was greater in all but the six most gravity-dependent lung slices during nCPAP (all p<0.05). Indicators of ventilation homogeneity were similar between nHFOV and nCPAP (all p>0.05). Aeration was increased during nHFOV (mean difference (95% CI)=0.4 (0.2 to 0.6) arbitrary units per kilogram (AU/kg), p=0.013), mainly due to an increase in non-gravity-dependent regions of the lung (∆EELINGD=6.9 (0.0 to 13.8) AU/kg, p=0.028; ∆EELImidNGD=6.8 (1.2 to 12.4) AU/kg, p=0.009). Aeration was more homogeneous during nHFOV compared with nCPAP (mean difference (95% CI) in AHR=0.01 (0.00 to 0.02), p=0.0014).
Conclusion Although regional ventilation was similar between nHFOV and nCPAP, end-expiratory lung volume was higher and aeration homogeneity was slightly improved during nHFOV. The aeration difference was greatest in non-gravity dependent regions, possibly due to the oscillatory pressure waveform. The clinical importance of these findings is still unclear.
- intensive care units
Data availability statement
Data are available upon request.
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Contributors PGD, DB, LS, DGT and CMR developed the concept and design of the initial study. VDG, ADW and CMR conceptualised and designed this post-hoc analysis. LS, JT and CMR were involved in patient recruitment and conducted the electrical impedance tomography (EIT) measurements. ADW developed the EIT analysis software. VDG, ADW and CMR performed EIT data analysis. All authors participated in data interpretation. VDG and CMR wrote the first draft and all authors contributed to redrafting the manuscript and revising it for intellectual input. CMR is acting as the guarantor of the overall content.
Funding Supported by the Victorian Government Operational Infrastructure Support Programme (Melbourne, Australia); the National Health and Medical Research Council (Practitioner Fellowship GNT 1059111 (to PGD)); the German Research Society (DFG-grant number: LO 2162/1-1 (to LS)); the TÜFF Habilitation Program (TÜFF 2459-0-0 (to LS)); Career Development Fellowships GNT 11123859 and 1057514 (to DGT)); the Swiss National Science Foundation (Early Postdoctoral Mobility fellowship P2ZHP3_161749 (to CMR)); the Swiss Society of Neonatology (Milupa Fellowship Award (to CMR)); and the Endeavour Research Fellowship by the Australian Government (ERF_RDDH_5276_2016 (to VDG)).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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