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

Abstract

The bedside Exhaled Drug MONitor – EDMON measures exhaled propofol in ppbv every minute based on multi-capillary column – ion mobility spectrometry (MCC-IMS). The MCC pre-separates gas samples, thereby reducing the influence of the high humidity in human breath. However, preliminary analyses identified substantial measurement deviations between dry and humid calibration standards. We therefore performed an analytical validation of the EDMON to evaluate the influence of humidity on measurement performance. A calibration gas generator was used to generate gaseous propofol standards measured by an EDMON device to assess linearity, precision, carry-over, resolution, and the influence of different levels of humidity at 100% and 1.7% (without additional) relative humidity (reference temperature: 37°C). EDMON measurements were roughly half the actual concentration without additional humidity and roughly halved again at 100% relative humidity. Standard concentrations and EDMON values correlated linearly at 100% relative humidity (R²=0.97). The measured values were stable over 100min with a variance ≤ 10% in over 96% of the measurements. Carry-over effects were low with 5% at 100% relative humidity after 5min of equilibration. EDMON measurement resolution at 100% relative humidity was 0.4 and 0.6 ppbv for standard concentrations of 3 ppbv and 41 ppbv. The influence of humidity on measurement performance was best described by a second-order polynomial function (R²≥0.99) with influence reaching a maximum at about 70% relative humidity. We conclude that EDMON measurements are strongly influenced by humidity and should therefore be corrected for sample humidity to obtain accurate estimates of exhaled propofol concentrations.

Exhaled breath is found to be better than blood samples for determining propofol concentrations in the brain tissues of rats

“…This VUV TOF-MS achieved a limit of quantification at 0.12 ppbv, satisfying the requirements for measuring exhaled propofol concentration in humans. Compared with the device of Edmon, our apparatus experiences less interference from water resulting in more stable output results [9]. Our pilot study demonstrated its capability to simultaneously determine the concentrations of various anesthetics, including propofol, ciprofol [18,19], fos-propofol, sevoflurane, and desflurane.…”

“…However, these instruments still have disadvantages such as loud noise and large volume [6]. Although devices based on ion mobility spectrometry (IMS) are small in size [7,8], such as Edmon, a product based on multi-capillary column-IMS (MCC-IMS) launched in 2017, its sensitivity can be easily affected by moisture [9].…”

Calibration and validation of ultraviolet time-of-flight mass spectrometry for online measurement of exhaled ciprofol

“…17 The performance of IMS is easily disturbed by humidity, which is high in exhaled breath. 18 Using UV-TOFMS, gas samples can be analysed online without pre-separation. The sensitivity of UV-TOFMS can reach the pptv level and it is insensitive to humidity, which meets the requirements for the detection of trace volatile organic compounds in exhaled breath.…”