Capnographic Analysis of Minimum Mandatory Flow Rate for Hudson Face Mask: A Randomized Double-blind Study

Area of Science:

• Anesthesiology
• Respiratory Physiology

Background:

• Hudson masks are common for oxygen delivery in perioperative settings.
• These masks carry a risk of rebreathing, especially in spontaneously breathing patients.
• Limited data exists on rebreathing using capnography with Hudson masks.

Purpose of the Study:

• To analyze the impact of different oxygen flow rates via Hudson mask on fractional inspired carbon dioxide (FiCO2).
• To assess rebreathing risk in spontaneously breathing patients using capnography.

Main Methods:

• Forty patients undergoing monitored anesthesia care were divided into four groups receiving 3, 4, 5, or 6 L/min oxygen via Hudson mask.
• Respiratory rate, end-tidal carbon dioxide (EtCO2), and FiCO2 were monitored for ten minutes.
• Statistical analysis included ANOVA, Kruskal-Wallis, and Pearson correlation.

Main Results:

• No significant differences in end-tidal carbon dioxide (EtCO2) or FiCO2 were observed across the flow rate groups.
• A strong positive correlation between respiratory rate and FiCO2 was noted at 3 L/min.
• Negative correlations between respiratory rate and FiCO2 were found at higher flow rates.

Conclusions:

• Fractional inspired carbon dioxide (FiCO2) levels are consistent across tested flow rates with Hudson masks.
• Increased respiratory rate can elevate FiCO2 at lower flow rates, but remains physiologically acceptable.