In Vitro Model of Prepacked Carbon Dioxide Absorber Use: Development and Testing

Area of Science:

• Anesthesiology
• Respiratory Physiology
• Medical Device Engineering

Background:

• Carbon dioxide (CO2) absorbers are crucial for anesthesia, allowing reduced fresh gas flow (FGF) below minute ventilation (V˙E).
• Accurate performance prediction of CO2 absorbers is essential for safe and efficient anesthetic gas delivery.
• Variability in CO2 load (V˙CO2), FGF, V˙E, and workstation type impacts absorber performance.

Purpose of the Study:

• To develop and validate in vitro models for quantifying CO2 absorber performance.
• To establish a linear relationship between FGF and fractional canister usage (FCU0.5).
• To assess the influence of V˙CO2 and V˙E on CO2 absorber efficiency.

Main Methods:

• Derived a linear relationship between FGF and FCU0.5 based on first principles.
• Developed two basic models and extended them with an empirical workstation factor.
• Tested hypotheses regarding the proportionality of FCU0.5 intercept with V˙CO2 and independence from V˙E.
• Compared measured FCU values against model predictions using Varvel's performance criteria.

Main Results:

• FCU0.5 was found to be proportional to V˙CO2 and independent of V˙E adjustments (P = 0.962) at a fixed FGF of 0.3 L/min.
• The hypothesized parallel shift in the FGF-FCU0.5 relationship was confirmed under varying V˙CO2 and V˙E.
• Both extended models demonstrated good predictive capabilities for canister performance.

Conclusions:

• The developed models effectively predict prepacked CO2 canister performance in vitro.
• These models are applicable across a range of V˙E, FGF, and V˙CO2 encountered in clinical practice.
• Further in vivo validation is recommended to confirm clinical utility.