Delivered oxygen concentrations using low-flow and high-flow nasal cannulas

Area of Science:

• Respiratory physiology
• Medical device engineering
• Clinical oxygen therapy

Background:

• Nasal cannulas are widely used for oxygen delivery in various clinical settings.
• Limited data exist on the actual delivered fraction of inspired oxygen (F(IO(2))) from nasal cannulas.
• Understanding F(IO(2)) is crucial for effective oxygen therapy.

Purpose of the Study:

• To quantify the delivered F(IO(2)) using both low-flow and high-flow nasal cannulas in human subjects.
• To investigate the impact of mouth-open versus mouth-closed breathing on delivered F(IO(2)).

Main Methods:

• Pharyngeal F(IO(2)) was measured in 10 healthy adults using nasal cannulas at flow rates from 1-15 L/min.
• Measurements were taken during resting and rapid breathing conditions.
• Gas samples were collected via a nasal catheter positioned behind the uvula.
• Statistical analysis compared F(IO(2)) during mouth-open and mouth-closed breathing.

Main Results:

• Delivered F(IO(2)) increased with higher flow rates for both low-flow (0.26-0.54) and high-flow (0.54-0.75) cannulas at rest.
• During rapid breathing, F(IO(2)) ranged from 0.24-0.45 (low-flow) to 0.49-0.72 (high-flow).
• Significant variability in F(IO(2)) was observed within and between subjects.
• Mouth-open breathing resulted in significantly higher F(IO(2)) compared to mouth-closed breathing (p < 0.05).

Conclusions:

• Oxygen delivery via nasal cannulas is flow-dependent, with higher flow rates yielding increased F(IO(2)).
• Breathing pattern significantly influences F(IO(2)), with open-mouth breathing enhancing oxygen delivery.
• These findings highlight the importance of considering patient breathing patterns for optimizing nasal cannula oxygen therapy.