Lung Volume Changes in Stable Preterm Infants Weaned From Nasal CPAP to High Flow

Abstract

Background

Weaning preterm infants off nasal CPAP (nCPAP) using nasal high-flow therapy has gained popularity. The effects of such a weaning strategy on lung volumes are unclear.

Research Question

How does the transition from nCPAP to high flow and varying flow levels affect lung volumes in stable preterm infants?

Study Design and Methods

This was a prospective cohort study in infants 30 to 35 weeks’ postmenstrual age. After a baseline period on nCPAP 5 cm H₂O, infants were switched to high flow 8 L/min for 30 minutes. The flow level was reduced by 2 L/min every 30 minutes to a minimum of 2 L/min and subsequently increased to the initial level of 8 L/min, followed by another nCPAP period. Using electrical impedance tomography, end-expiratory lung impedance as a proxy for end-expiratory lung volume (EELV) and cardiorespiratory parameters were recorded at each flow level and compared with baseline.

Results

Overall, 8,438 breaths from 19 infants were analyzed. EELV changed significantly during the study (P = .002), which was mainly attributable to a loss of EELV when high flow was reduced to 6 and 4 L/min and re-escalated to 4, 6, and 8 L/min. Apart from a reduction in minute ventilation (P = .004), no other significant changes were found in electrical impedance tomography ventilation parameters. Alterations in lung volume were accompanied by an increase in heart rate (P = .02) and a decrease in peripheral oxygen saturation/Fio₂ ratio (P < .001).

Interpretation

The results of this study indicate that the transition from nCPAP to high flow is likely to result in a reduced EELV, accompanied by physiological responses in heart rate and oxygenation. Despite a stepwise escalation to preweaning flow levels, we found that only partial recovery of lung volume losses was achievable with high flow.

Clinical Trial Registration

ClinicalTrials.gov; No.: NCT05237622; URL: www.clinicaltrials.gov