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

Development and validation of a novel UV-TOF MS method for real-time exhaled propofol analysis in Beagles

Propofol, a fast-acting anesthetic, requires precise titration to minimize adverse effects. While plasma-based monitoring is slow, exhaled propofol offers a real-time, non-invasive alternative, though its clinical application remains limited. This study evaluates ultraviolet time-of-flight mass spectrometry (UV-TOF MS) for real-time monitoring, presenting its calibration and validation in Beagle dogs. Calibration showed excellent linearity (R2 = 0.9939) over 3.23-46.13 ppbv. The intra-day imprecision at propofol concentrations of 4.61 and 23.06 ppbv was below 5.83% and 7.75%, respectively, while the inter-day imprecision was 9.69% and 9.75%, respectively. Carry-over effects were minimal, with signal recovery within 40-60 s, measuring 8.7%, 9.1%, and 4.7% at 4.61, 9.30, and 23.06 ppbv, respectively. In Beagle dogs, Cexhaled exhibited a moderately strong linear correlation with Cplasma (R2 = 0.7950) and a moderate correlation with sedative effects, as indicated by the bispectral index (R2 = 0.5501) after a single bolus injection. Pharmacokinetic (PK) analysis revealed a delay in peak concentration (Tmax) for Cexhaled (2.00 ± 0.21 min) compared to Cplasma (1.00 ± 0.00 min). While AUC values were not directly comparable, both exhibited R_AUC > 80%, indicating reliable drug kinetic reflection. Mean residence time (MRT) and elimination rate constants (λz) showed no significant differences. These results suggest that exhaled breath analysis provides pharmacokinetic insights comparable to plasma, with a slight delay in peak concentration. UV-TOF MS proved to be an efficient method for detecting exhaled propofol, offering potential for real-time anesthesia monitoring in clinical settings.

Online monitoring of propofol concentrations in exhaled breath

Propofol, a widely used intravenous anesthetic agent, requires accurate monitoring to ensure therapeutic efficacy and prevent oversedation. Recent developments in modern analytical instrumentation have led to significant breakthroughs in on-line analysis of exhaled breath. This review discusses several sophisticated analytical methods that have been explored for noninvasive, real-time monitoring of propofol concentrations, including proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry, ion mobility spectrometry, and gas chromatography coupled to surface acoustic wave sensors. These techniques have demonstrated good correlations between plasma and exhaled propofol concentrations and between exhaled propofol concentrations and its cerebral effects. Despite these advances, the use of these technologies in clinical settings is hampered by challenges such as equipment noise, bulkiness, and high cost, as well as limitations related to endotracheal intubation, strong adsorption of propofol to components of the respiratory circuit, variability in respiratory patterns, susceptibility to changes in pulmonary ventilation and blood flow, inconsistencies in calibration methods, and the influence of other drugs and temperature fluctuations on measurement accuracy. Overcoming these technical and procedural challenges is critical to advancing the clinical application of breath analysis for propofol monitoring. This article reviews published studies and summarizes the progress and ongoing challenges in the field.

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

The correlation between propofol concentration in exhaled breath (CE) and plasma (CP) has been well-established, but its applicability for estimating the concentration in brain tissues (CB) remains unknown. Given the impracticality of directly sampling human brain tissues, rats are commonly used as a pharmacokinetic model due to their similar drug-metabolizing processes to humans. In this study, we measuredCE,CP, andCBin mechanically ventilated rats injected with propofol. Exhaled breath samples from the rats were collected every 20 s and analyzed using our team's developed vacuum ultraviolet time-of-flight mass spectrometry. Additionally, femoral artery blood samples and brain tissue samples at different time points were collected and measured using high-performance liquid chromatography mass spectrometry. The results demonstrated that propofol concentration in exhaled breath exhibited stronger correlations with that in brain tissues compared to plasma levels, suggesting its potential suitability for reflecting anesthetic action sites' concentrations and anesthesia titration. Our study provides valuable animal data supporting future clinical applications.

A preclinical study on online monitoring of exhaled ciprofol concentration by the ultraviolet time-of-flight spectrometer and prediction of anesthesia depth in beagles

BACKGROUND

Exhaled air has been demonstrated as a reliable medium for monitoring propofol concentration. However, online monitoring of exhaled ciprofol have not been reported.

METHODS

Thirty-six beagles undergoing mechanical ventilation were divided into 6 groups, including bolus injection of low (Group BL, n = 6), medium (Group BM, n = 6), and high dose of ciprofol (Group BH, n = 6) groups; as well as 1 h continuous infusion of low (Group IL, n = 6), medium (Group IM, n = 6), and high dose of ciprofol (Group IH, n = 6) groups. The ciprofol concentration in exhaled air (CE) was determined by the ultraviolet time-of-flight mass spectrometer (UV-TOFMS). The correlations of CE and plasma concentration (Cp), CE and the bispectral index (BIS) were explored. Additionally, the pharmacokinetics (PK) models of CE and Cp, the pharmacodynamics (PD) models of CE and BIS were also established.

RESULTS

Online monitoring of exhaled ciprofol can be achieved with the UV-TOFMS instrument. The CE of ciprofol in beagles was found at parts per billion by volume (ppbv) level. The linear correlation of CE and Cp was weak in bolus injection groups (R2 = 0.01) nonetheless moderate in continuous infusion groups (R2 = 0.53). The i.v. bolus PK model of CE and Cp can be fitted with the non-compartment models. Additionally, the the PD models of CE and BIS can be well fitted with the inhibitory sigmoid Emax model with the estimate values of IC50 = 0.05 ± 0.01 ppbv, γ = 4.74 ± 1.51, E0 = 81.40 ± 3.75, Imax = 16.35 ± 4.27 in bolus injection groups; and IC50 = 0.05 ± 0.01 ppbv, γ = 6.92 ± 1.30, E0 = 83.08 ± 1.62, Imax = 12.58 ± 1.65 in continuous infusion groups.

CONCLUSIONS

Online monitoring of exhaled ciprofol concentration in beagles can be achieved with the UV-TOFMS instrument. Good correlations can be observed between exhaled ciprofol concentration and its cerebral effects reflected by the BIS value, demonstrating the potential of exhaled ciprofol monitoring for titrating depth of anesthesia in future clinical setting.

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

Ciprofol (HSK 3486, C14H20O), a novel 2,6-disubstituted phenol derivative similar to propofol, is a new type of intravenous general anaesthetic. We found that the exhaled ciprofol concentration could be measured online by ultraviolet time-of-flight mass spectrometry (UV-TOFMS), which could be used to predict the plasma concentration and anaesthetic effects of ciprofol. In this study, we present the calibration method and validation results of UV-TOFMS for the quantification of ciprofol gas. Using a self-developed gas generator to prepare different concentrations of ciprofol calibration gas, we found a linear correlation between the concentration and intensity of ciprofol from 0 parts per trillion by level (pptv) to 485.85 pptv (R2 = 0.9987). The limit of quantification was 48.59 pptv and the limit of detection was 7.83 pptv. The imprecision was 12.44% at 97.17 pptv and was 8.96% at 485.85 pptv. The carry-over duration was 120 seconds. In addition, we performed a continuous infusion of ciprofol in beagles, measured the exhaled concentration of ciprofol by UV-TOFMS, determined the plasma concentration by high-performance liquid chromatography, and monitored the anaesthetic effects as reflected by the bispectral index value. The results showed that the exhaled and plasma concentrations of ciprofol were linearly correlated. The exhaled ciprofol concentration correlated well with the anaesthetic effect. The study showed that we could use UV-TOFMS to provide a continuous measurement of gaseous ciprofol concentration at 20 second intervals.