# CPAP and high-flow nasal oxygen also reduce lung, diaphragm, and accessory muscle injury in experimental self-inflicted lung injury

## TL;DR

This study shows that CPAP and HFNO reduce lung and muscle injury in experimental self-inflicted lung injury in rats.

## Contribution

The study demonstrates that CPAP is most protective for the diaphragm, while mechanical ventilation offers the highest lung injury protection.

## Key findings

- CPAP reduced respiratory rate and prevented loss of lung aeration.
- MV showed the highest injury protection in lungs and accessory muscles.
- CPAP was most protective for the diaphragm compared to HFNO and MV.

## Abstract

Strenuous respiratory effort has been proposed as a second hit, introducing the concepts of “patient self-inflicted lung injury” (P-SILI) and underassistance myotrauma. We investigated the effects of continuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) on inspiratory and expiratory effort, lung injury, and myotrauma of obligatory and accessory respiratory muscles in experimental P-SILI. In rats, lung injury was induced through surfactant depletion, followed by 3 h of standard oxygen therapy (2 L/min, positive control) or supported ventilation (CPAP 6 cmH2O, HFNO 4 L/min, and protective mechanical ventilation [MV, negative control] groups). Subjects were assessed through esophageal manometry, surface electromyography on the abdominal wall, thoracic ultrasound, plasma multiplex analysis, and histology on the lungs, diaphragm, and accessory inspiratory and expiratory muscles. Compared against standard oxygen therapy, the MV and CPAP groups resulted in lower inspiratory and expiratory efforts and diaphragm excursion. Furthermore, intragroup analysis showed that CPAP also reduced respiratory rate and prevented the loss of lung aeration. All support therapies prevented lung, diaphragm, and accessory muscle injuries, but with nuances. In lungs and accessory muscles, MV showed the highest injury protection and HFNO the lowest, while CPAP was the most protective for the diaphragm. Only MV resulted in a lower plasma GRO-α concentration than standard oxygen therapy. Invasive and non-invasive respiratory support therapies are effective in protecting the lungs and respiratory muscles, but the effect is stepped in the lung and varies between obligatory and accessory respiratory muscles.

The online version contains supplementary material available at 10.1038/s41598-026-39564-7.