# Diaphragm Thickness and Contraction During Non-Invasive Ventilation: An Ultrasound Study

## TL;DR

This study uses ultrasound to track changes in diaphragm thickness and contraction in preterm infants receiving non-invasive ventilation for respiratory distress syndrome.

## Contribution

The study provides novel insights into diaphragm behavior during non-invasive ventilation in preterm infants and its association with ventilation discontinuation failure.

## Key findings

- Diaphragm thickness increased over time during non-invasive ventilation, while contractility decreased.
- NIV discontinuation failure was associated with thicker diaphragms at the start of treatment and reduced diaphragm trophism over time.
- No significant predictors of NIV failure were identified, and neonatal outcomes were similar between success and failure groups.

## Abstract

Objectives: Non-invasive ventilation (NIV) is a widely used treatment for neonatal respiratory distress syndrome (RDS). Data on diaphragm contractility and thickness during NIV is scarce. We aimed to describe changes in diaphragm thickness/contractility during NIV and to explore associations with NIV discontinuation failure. Methods: This is a single-center prospective study. Diaphragmatic ultrasound was performed weekly during NIV, then within 7 days from NIV discontinuation. Diaphragm thickness was measured at end-inspiration (DTI) and end-expiration (DTE). Diaphragm thickening fraction (DTF) was calculated as (DTI-DTE/DTE). The clinical characteristics of patients and NIV discontinuation failure were recorded. Univariate analysis, logistic regression and linear regression were performed to describe diaphragm features during NIV and associations with NIV discontinuation failure. Results: We studied 17 NIV cycles (median duration 21 days). Median DTE increased from 0.12 cm (SD 0.05) at the start of NIV to 0.15 cm (SD 0.04) at NIV discontinuation. The mean DTF decreased from 32.8 (SD 16.8) at the start of NIV to 25.6 (SD 8.9) at NIV discontinuation. NIV discontinuation failure occurred in 23.5% of infants and was associated with higher DTI and DTE at the start of NIV and with a more pronounced decrease in DTI and DTE over the NIV cycle, compared to infants with NIV discontinuation success. There were no differences in neonatal outcomes between the infants with NIV discontinuation failure vs. success. We did not find any significant predictors of NIV failure. Conclusions: Diaphragm thickness increased, whereas DTF decreased over time on NIV in preterm infants with RDS. NIV duration was not associated with changes in diaphragm trophism. NIV discontinuation failure was associated with thicker diaphragm at the start of NIV, as well as with a reduction in diaphragm trophism over the NIV cycle.