Humidity and measurement of volatile propofol using MCC-IMS (EDMON).

Area of Science:

• Anesthesiology and Pharmacology
• Analytical Chemistry
• Biomedical Engineering

Background:

• The Exhaled Drug Monitor (EDMON) uses multi-capillary column-ion mobility spectrometry (MCC-IMS) to measure exhaled propofol.
• MCC-IMS technology aims to mitigate humidity's impact on breath gas analysis.
• Preliminary findings indicated significant discrepancies between dry and humid calibration standards for EDMON.

Purpose of the Study:

• To conduct an analytical validation of the EDMON device.
• To quantitatively assess the influence of varying humidity levels on EDMON's measurement performance.
• To determine the accuracy and reliability of EDMON for exhaled propofol monitoring under different humidity conditions.

Main Methods:

• Utilized a calibration gas generator to produce gaseous propofol standards.
• Measured propofol concentrations using an EDMON device at 1.7% and 100% relative humidity (37°C).
• Evaluated EDMON performance parameters including linearity, precision, carry-over, and resolution.

Main Results:

• EDMON measurements underestimated propofol concentration, reading approximately half the actual value at low humidity and half again at 100% relative humidity.
• A strong linear correlation (R²=0.97) was observed between standard concentrations and EDMON values at 100% relative humidity.
• Measurement stability was high (>96% of measurements within 10% variance over 100 min), with low carry-over (5% at 100% RH).
• The impact of humidity on measurements followed a second-order polynomial function (R²≥0.99), peaking around 70% relative humidity.

Conclusions:

• EDMON's exhaled propofol measurements are substantially affected by sample humidity.
• Accurate quantification of exhaled propofol using EDMON necessitates humidity correction algorithms.
• Further research should focus on developing and implementing humidity compensation for reliable clinical application.