Objectives To determine the regional ventilation characteristics during non-invasive ventilation (NIV) in stable preterm infants. The secondary aim was to explore the relationship between indicators of ventilation homogeneity and other clinical measures of respiratory status.
Design Prospective observational study.
Setting Two tertiary neonatal intensive care units.
Patients Forty stable preterm infants born <30 weeks of gestation receiving either continuous positive airway pressure (n=32) or high-flow nasal cannulae (n=8) at least 24 hours after extubation at time of study.
Interventions Continuous electrical impedance tomography imaging of regional ventilation during 60 min of quiet breathing on clinician-determined non-invasive settings.
Main outcome measures Gravity-dependent and right–left centre of ventilation (CoV), percentage of whole lung tidal volume (VT) by lung region and percentage of lung unventilated were determined for 120 artefact-free breaths/infant (4770 breaths included). Oxygen saturation, heart and respiratory rates were also measured.
Results Ventilation was greater in the right lung (mean 69.1 (SD 14.9)%) total VT and the gravity-non-dependent (ND) lung; ideal–actual CoV 1.4 (4.5)%. The central third of the lung received the most VT, followed by the non-dependent and dependent regions (p<0.0001 repeated-measure analysis of variance). Ventilation inhomogeneity was associated with worse peripheral capillary oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) (p=0.031, r2 0.12; linear regression). In those infants that later developed bronchopulmonary dysplasia (n=25), SpO2/FiO2 was worse and non-dependent ventilation inhomogeneity was greater than in those that did not (both p<0.05, t-test Welch correction).
Conclusions There is high breath-by-breath variability in regional ventilation patterns during NIV in preterm infants. Ventilation favoured the ND lung, with ventilation inhomogeneity associated with worse oxygenation.
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Contributors DGT and LSO developed the concept and experimental design. JT, CMR, EJP and DGT were involved in data acquisition and JT, OF and CMR analysed the data. DGT, PMP-F, LSO and EP supervised the study. All authors participated in data interpretation. JT and DGT drafted the first manuscript and all authors contributed to editing.
Funding This study is supported by the Victorian Government Operational Infrastructure Support Program (Melbourne, Australia). DGT is supported by a National Health and Medical Research Council Clinical Career Development Fellowship (grant ID 1053889). CMR is supported by a Swiss National Science Foundation Early Postdoctoral Mobility fellowship (P2ZHP3_161749) and the Milupa Fellowship Award of the Swiss Society of Neonatology. SenTec AG (Landquart, Switzerland) manufactured custom-built electrical impedance tomography (EIT) belts for infants. All EIT hardware was purchased by Murdoch Children's Research Institute without any restrictions.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval This study was approved by the Royal Children’s Hospital Human Research Ethics Committee (HREC 36159A) and the Royal Women’s Hospital Human Research Ethics Committee (HREC 16–33), in accordance with the National Health and Medical Research Council Statement of Ethical Conduct in Human Research (2007).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Deidentified individual participant data, study protocols and statistical analysis codes are available from 3 months to 23 years following article publication to researchers who provide a methodologically sound proposal, with approval by an independent review committee ('learned intermediary'). Proposals should be directed to firstname.lastname@example.org to gain access. Data requestors will need to sign a data access or material transfer agreement approved by the Murdoch Children's Research Institute.
Author note A preprint version (MEDRXIV/2020/168575) is available at https://doi.org/10.1101/2020.08.04.20168575.
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