Exhalation Spreading During Nasal High-Flow Therapy at Different Flow Rates

Area of Science:

• Respiratory medicine
• Infectious disease transmission
• Medical engineering

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads via aerosols and droplets.
• Nasal high-flow therapy (NHFT) may enhance the dispersal of patient exhalates.
• Understanding expiratory plume dynamics during NHFT is crucial for infection control.

Purpose of the Study:

• To determine if NHFT alters the range of the expiratory plume compared to spontaneous breathing.
• To quantify the effect of varying NHFT rates on exhalation spread.
• To evaluate the efficacy of surgical masks in mitigating expiratory plume spread during NHFT.

Main Methods:

• An interventional experiment was conducted on a single healthy volunteer in a research laboratory.
• Schlieren optical imaging was used to analyze expiratory plume spread during spontaneous breathing and NHFT at 20, 40, and 60 L/min.
• Expiratory plume range was measured in the sagittal plane.

Main Results:

• Expiratory plume spread increased with NHFT rates, reaching up to 4.1 meters at 60 L/min, compared to 0.99 meters during spontaneous breathing.
• The maximal exhalation spread was 0.99 m (spontaneous breathing), 2.18 m (20 L/min NHFT), 2.92 m (40 L/min NHFT), and 4.1 m (60 L/min NHFT).
• A surgical mask completely blocked expiratory plume spread in the sagittal plane.

Conclusions:

• NHFT significantly extends the range of expiratory airflow, potentially increasing the risk of airborne infectious particle transmission.
• The findings highlight the importance of considering enhanced aerosol dispersal during NHFT.
• Utilizing a surgical mask over the NHFT cannula effectively contains the expiratory airstream, reducing transmission risk.