Bakcground: Delivery of bronchodilators via HFNC has gained great interest in recent years. Clinical studies in stable asthma have demonstrated a positive bronchodilator response combined in-line vibrating mesh nebulisers (VMN) with HFNC. We aimed to measure bronchodilator response by peak expiratory flow (PEF) at baseline and 120 minutes after treatment in adults with moderate-severe asthma exacerbation. Secondary objectives were to assess the impact on clinical variables

Methods: Prospective single-centre study, from March to December 2022, subjects with asthma exacerbation requiring HFNC at admission were enrolled. HFNC was administered via Airvo2 (Fisher & Paykel, New Zealand), flow was set to 30 L/m, temperature to 34°C and FiO2 to SpO2 92%-96%. VMN (Aerogen Solo, Ireland) was placed at the humidifier and Salbutamol (2.5 mg) was administered. They were measured before and after PEF (L/m) bronchodilator treatment. Clinical variables such as respiratory rate (RR), heart rate (HR) and SpO2 at admission, during HFNC and 120 minutes after treatment were also recorded.

Results: Fifteen subjects were included, mean (SD) age was 39 (19.9) years and mean (SD) baseline PEF was 178 (12.9) L/m with a significant improvement to 196 (23.7) L/m (p= 0.009) at 120 minutes post-treatment. RR showed improvement from admission, during HFNC and even 120 minutes (29 rpm vs 19 rpm; p= <0.001; 19 rpm vs 17 rpm; p=0.041). No significant changes in HR and SpO2 were observed at 120 minutes.

Conclusions: In subjects with asthma exacerbation this combined therapy appears to be effective in improving PEF and decreasing RR.