Fraction of Inspired Oxygen With Low-Flow Versus High-Flow Devices: A Simulation Study

Area of Science:

• Respiratory Physiology
• Medical Device Engineering

Background:

• Fraction of inspired oxygen (FiO2) is a critical parameter in respiratory care, reflecting alveolar oxygen concentration.
• Accurate measurement of FiO2 is essential for effective oxygen therapy and patient management.

Purpose of the Study:

• To compare the fractions of inspired oxygen (FiO2) delivered by various oxygen delivery devices.
• To evaluate the impact of different oxygen delivery systems on respiratory physiology.

Main Methods:

• Utilized a simulation model of spontaneous respiration.
• Measured FiO2 from low-flow nasal cannulas, high-flow nasal cannulas, and simple oxygen masks.
• Recorded FiO2 every second for 30 seconds post 120 seconds of oxygen administration, with three repetitions per condition.

Main Results:

• Low-flow nasal cannulas showed reduced intratracheal and extraoral oxygen concentrations, suggesting rebreathing during exhalation may increase FiO2.
• High-flow nasal cannulas achieved a high FiO2 at a flow rate of 10 L/min.
• Estimating FiO2 with low-flow nasal cannulas and simple oxygen masks may be challenging in clinical practice.

Conclusions:

• Oxygen administration during expiratory flow can increase oxygen concentration in anatomical dead space, potentially elevating FiO2.
• Appropriate flow rate selection is vital for optimizing oxygen therapy, considering patient-specific conditions beyond just FiO2 values.
• Clinical estimation of FiO2 may be unreliable with low-flow nasal cannulas and simple oxygen masks.