Should we judge a mask by its cover?

Area of Science:

• Respiratory Medicine
• Biomedical Engineering

Background:

• Oxygen mask packaging often provides tables for inspired oxygen delivery at specific flow rates.
• A new multipurpose oxygen mask designed for use with or without Venturi attachments was evaluated for emergency applications.

Purpose of the Study:

• To assess the accuracy of inspired oxygen concentration delivered by a new multipurpose oxygen mask.
• To compare delivered oxygen concentrations with manufacturer-stated values and evaluate the effect of Venturi attachments.

Main Methods:

• Inspired oxygen concentrations were measured in 12 healthy subjects at rest and 26 breaths/min using a mass spectrometer.
• Oxygen and carbon dioxide levels were recorded at the lips, and inspired oxygen was calculated using the alveolar gas equation.
• Measurements were taken with the mask alone and with 24% and 28% Venturi attachments at various oxygen flow rates.

Main Results:

• Without Venturi attachments, the mask delivered 8-10% higher oxygen concentrations than labeled at 2, 4, and 6 L/min.
• Some individuals received up to 30% more oxygen than expected without the Venturi attachment.
• With Venturi attachments, delivered concentrations were within 2% of the intended 24% and 28%.

Conclusions:

• Labeling on oxygen masks may be inaccurate, potentially leading to incorrect oxygen therapy, especially by non-experts.
• Careful selection of multipurpose masks is essential for emergency use, particularly when precise low oxygen concentrations are required.