The Impact of High-Flow Nasal Cannula Therapy on Diaphragmatic Function Assessed by Ultrasound: A Pilot Clinical Study.

OBJECTIVES

High-flow nasal cannula is increasingly used in patients with acute hypoxemic respiratory failure. However, its impact on diaphragmatic function remains poorly understood.

DESIGN

Observational crossover pilot study.

SETTING

Single-center ICU.

PATIENTS: Twenty-eight adult ICU patients with a Pa o2 /F io2 ratio less than or equal to 300 mm Hg were enrolled.

INTERVENTIONS: Patients underwent sequential 60-minute phases of noninvasive respiratory support using a Venturi mask, high-flow nasal cannula (40 L/min), and helmet continuous positive airway pressure (CPAP).

MEASUREMENTS AND MAIN

RESULTS

Diaphragmatic function was assessed using ultrasound, while inspiratory effort was evaluated through esophageal pressure swings. Arterial blood gases were also collected. High-flow nasal cannula significantly improved the diaphragmatic thickening fraction compared with the Venturi mask (27% ± 9.9% vs. 20% ± 6%; p = 0.0013). Conversely, diaphragmatic excursion was lower with high-flow nasal cannula than with both the Venturi mask and CPAP (1.1 ± 0.63 cm vs. 1.5 ± 0.95 cm and 1.4 ± 0.59 cm, respectively; p = 0.0002). High-flow nasal cannula also reduced inspiratory effort compared with the Venturi mask. In patients with diaphragmatic dysfunction index greater than 100, both high-flow nasal cannula and CPAP enhanced diaphragmatic thickening and decreased esophageal pressure swings relative to the Venturi mask.

CONCLUSIONS

This study shows that high-flow nasal cannula improves diaphragmatic function compared with Venturi mask oxygen therapy. Larger studies are needed to confirm these findings.