Drug detection in breath: effects of pulmonary blood flow and cardiac output on propofol exhalation

Breath analysis could offer a non-invasive means of intravenous drug monitoring if robust correlations between drug concentrations in breath and blood can be established. In this study, propofol blood and breath concentrations were determined in an animal model under varying physiological conditions. Propofol concentrations in breath were determined by means of two independently calibrated analytical methods: continuous, real-time proton transfer reaction mass spectrometry (PTR-MS) and discontinuous solid-phase micro-extraction coupled with gas chromatography mass spectrometry (SPME-GC-MS). Blood concentrations were determined by means of SPME-GC-MS. Effects of changes in pulmonary blood flow resulting in a decreased cardiac output (CO) and effects of dobutamine administration resulting in an increased CO on propofol breath concentrations and on the correlation between propofol blood and breath concentrations were investigated in seven acutely instrumented pigs. Discontinuous propofol determination in breath by means of alveolar sampling and SPME-GC-MS showed good agreement (R ² = 0.959) with continuous alveolar real-time measurement by means of PTR-MS. In all investigated animals, increasing cardiac output led to a deterioration of the relationship between breath and blood propofol concentrations (R ² = 0.783 for gas chromatography-mass spectrometry and R ² = 0.795 for PTR-MS). Decreasing pulmonary blood flow and cardiac output through banding of the pulmonary artery did not significantly affect the relationship between propofol breath and blood concentrations (R ² > 0.90). Estimation of propofol blood concentrations from exhaled alveolar concentrations seems possible by means of different analytical methods even when cardiac output is decreased. Increases in cardiac output preclude prediction of blood propofol concentration from exhaled concentrations.     

Time course of expiratory propofol after bolus injection as measured by ion molecule reaction mass spectrometry

Propofol in exhaled breath can be detected and monitored in real time by ion molecule reaction mass spectrometry (IMR-MS). In addition, propofol concentration in exhaled breath is tightly correlated with propofol concentration in plasma. Therefore, real-time monitoring of expiratory propofol could be useful for titrating intravenous anesthesia, but only if concentration changes in plasma can be determined in exhaled breath without significant delay. To evaluate the utility of IMR-MS during non-steady-state conditions, we measured the time course of both expiratory propofol concentration and the processed electroencephalography (EEG) as a surrogate outcome for propofol effect after an IV bolus induction of propofol. Twenty-one patients scheduled for routine surgery were observed after a bolus of 2.5 mg kg⁻¹ propofol for induction of anesthesia. Expiratory propofol was measured using IMR-MS and the cerebral propofol effect was estimated using the bispectral index (BIS). Primary endpoints were time to detection of expiratory propofol and time to onset of propofol’s effect on BIS, and the secondary endpoint was time to peak effect (highest expiratory propofol or lowest BIS). Expiratory propofol and changes in BIS were first detected at 43 ± 21 and 49 ± 11 s after bolus injection, respectively (P = 0.29). Peak propofol concentrations (9.2 ± 2.4 parts-per-billion) and lowest BIS values (23 ± 4) were reached after 208 ± 57 and 219 ± 62 s, respectively (P = 0.57). Expiratory propofol concentrations measured by IMR-MS have similar times to detection and peak concentrations compared with propofol effect as measured by the processed EEG (BIS). This suggests that expiratory propofol concentrations may be useful for titrating intravenous anesthesia.     

Direct and rapid determination of elements in the ambient air and in human exhalation using the electrostatic precipitation of aerosols in the graphite atomizer of a zeeman spectrometer

The use of a new Zeeman spectrometer with the electrostatic precipitation of aerosols in the graphite furnace of the atomizer for the direct and rapid determination of aerosols in the ambient air and in the air exhaled by human beings is presented. The results are given for the comparative determination of elements in laboratory air by electrostatic precipitation and with the filter accumulation of aerosols. A correlation is found between the concentration of Se in the exhaled air and its concentration in the examinee’s blood.     

Application of solid-phase microextraction and gas chromatography-mass spectrometry to the determination of volatile organic compounds in end-exhaled breath samples

Analysis of exhaled air is of particular interest as an indicator of health as well as a tool for the diagnosis of diseases. It is also a very attractive procedure for the biological control of the exposition to hazardous solvents. This kind of analysis presents numerous advantages over other methods, the most important being that it is not an invasive procedure and, therefore, it is well accepted and can be applied to a wide range of compounds. Furthermore, the analysis is simplified since the matrix is less complex that in the case of blood or urine. In spite of these obvious advantages and the good results obtained, analysis of exhaled air is not in daily use, probably due to the fact that there are no normalized systems of sampling, thus making the interpretation of the results difficult. In this paper, a method for the determination of tetrachloroethylene in exhaled air using solid-phase microextraction is presented. This method, which can be applied to other volatile organic compounds, was developed with special emphasis of end-exhaled breath sampling. The sample is collected in a glass tube whose ends are closed once the exhalation is finished. The tube has an orifice sealed with a septum through which the fiber is inserted. Then, the fiber is desorbed in the injector of a gas chromatograph and the analysis is accomplished using mass spectrometry for the identification and quantification of the components. The proposed system avoids the need of complex sampling equipment and allows analysis of the alveolar fraction. Additionally, the system is economical and easy to handle, thus facilitating the development of normalized methods and its routine use in field studies.     

An Evidence-Based Review of Application Devices for Nitric Oxide Concentration Determination from Exhaled Air in the Diagnosis of Inflammation and Treatment Monitoring

The measurement of nitric oxide (NO) in exhaled air is used in diagnostics and monitoring the pathologies not only in the respiratory system but also in the oral cavity. It has shown a huge increase in its level in asthma and diseases of the oral cavity. It seems reasonable to undertake research on the impact of inflammation on the level of NO in exhaled air. The aim of the study is to make an evidence-based review of the application of NO levels in exhaled air in the diagnosis of inflammation and treatment monitoring on the basis of selected measuring devices. Methods and Results: This paper presents an example of the application of NO measurement in exhaled air in individual human systems. Selected measuring devices, their non-invasiveness, and their advantages are described. Discussion: The usefulness of this diagnostic method in pathologies of the oral cavity was noted. Conclusions: Measuring the level of NO in exhaled air seems to be a useful diagnostic method.     

Selected ion flow tube mass spectrometry for on-line trace gas analysis in biology and medicine

Selected ion flow tube mass spectrometry, (SIFT-MS), is a technique for simultaneous real-time quantification of several trace gases in air and exhaled breath. It relies on chemical ionization of the trace gas molecules in air/breath samples introduced into helium carrier gas, using H(3)O(+), NO(+) and O(2)(+) reagent (precursor ions). Reactions between the precursor ions and the trace gas molecules proceed for an accurately defined time, the precursor and product ions being detected and counted by a downstream mass spectrometer. Absolute concentrations of trace gases in single breath exhalation can be determined by SIFT-MS down to parts-per-billion (ppb) levels, obviating sample collection into bags or onto traps. Calibration using chemical standards is not required, as the concentrations are calculated using the known reaction rate constants and measured flow rates and pressures. SIFT-MS has been used for many pilot investigations in several areas of research, especially as a non-invasive breath analysis tool to investigate physiological processes in humans and animals, for clinical diagnosis and for therapeutic monitoring. Examples of the results obtained from several such studies are outlined to demonstrate the potential of SIFT-MS for trace gas analysis of air, exhaled breath and the headspace above liquids.     

Extraction of information attributes from the mass spectrometric signals of air

The paper describes a new method of the extraction of information attributes from the processed signals, generalized spectral analysis in an adapted basis. Studies of the functional structure of mathematical foundations and an adaptable classification system of different signal types, including the quadrupole mass spectra of air, were carried out. Algorithms for the synthesis of basis functions adapted to orthogonal transforms of process signals were developed. The use of the method for analytical instrumentation was demonstrated by the processing of mass spectra recorded on a quadrupole mass spectrometer in the analysis of gases exhaled by humans.     

Direct measurement of the mercury content of exhaled air: a new approach for determination of the mercury dose received

A new rapid technique is presented for determination of the dose of mercury inhaled; it is based on direct measurement of the concentration of mercury in exhaled air by use of a Zeeman mercury spectrometer RA-915+. It has been demonstrated experimentally that the dose received during short-term exposure to mercury vapor is determined more reliably by this method rather than by conventional techniques based on measurement of the mercury content in blood or urine.     

New method for determination of trihalomethanes in exhaled breath: Applications to swimming pool and bath environments

A method for the estimation of the human intake of trihalomethanes (THMs), namely chloroform, bromodichloromethane, dibromochloromethane and bromoform, during showering and bathing is reported. The method is based on the determination of these compounds in exhaled breath that is collected by solid adsorption on Tenax using a device specifically designed for this purpose. Instrumental measurements were performed by automatic thermal desorption coupled to gas chromatography with electron capture detection. THMs in exhaled breath samples were determined during showering and swimming pool attendance. The levels of these compounds in indoor air and water were also determined as reference for interpretation of the exhaled breath results. The THM concentrations in exhaled breath of the volunteers measured before the exposure experiments showed a close correspondence with the THMs levels in indoor air where the sampler was located. Limits of detection in exhaled breath were dependent on THM analytes and experimental sites. They ranged between 170 and 710 ng m⁻³ in the swimming pool studies and between 97 and 460 ng m⁻³ in the showering studies. Application of this method to THMs determination during showering and swimming pool activities revealed statistically significant increases in THMs concentrations when comparing exhaled breath before and after exposure.     

Detection of characteristic clusters in IMS-Spectrograms of exhaled air polluted with environmental contaminants

Detection of special disease markers in exhaled breath is a method becoming more and more relevant in medical diagnostic. The test environment plays a big role in the analysis of exhaled air when using ion mobility spectrometry (IMS). Environmental contaminants appear also in exhaled air of test persons, potentially even in other forms then in the ambient air. Different ways to deal with these environmental factors will be discussed and our method of choice will be presented. It was possible to identify specific fingerprints for dedicated features of probands as well as for specific environmental pollution. By using statistical evaluation it was also possible to identify characteristic features of probands notwithstanding the environmental burden for correct assignment into specific groups, reaching correct classification rates above 0.85.     

Quantification of hydrogen cyanide in humid air by selected ion flow tube mass spectrometry

Following our recent observation that Pseudomonas bacteria in vitro emit hydrogen cyanide, we have found it necessary to investigate the ion chemistry of this compound and to extend the kinetics database for selected ion flow tube mass spectrometry (SIFT-MS) to allow the accurate quantification of HCN in moist air samples, including exhaled breath. Because of the proximity of the proton affinities of HCN and H2O molecules, the presence of water vapour can significantly distort HCN analysis in the presence of water vapour and a more sophisticated analytical procedure has to be developed. Thus, the reactions of H3O+(H2O)0,1,2,3 ions with HCN molecules have been studied in the presence of varying concentrations of water vapour, reactions on which SIFT-MS analysis of HCN relies. The results of these experiments have allowed an analytical procedure to be developed which has extended the kinetics database of SIFT-MS, such that HCN can now be quantified in humid air and in exhaled breath.     

Human breath analysis: methods for sample collection and reduction of localized background effects

Solid-phase microextraction (SPME) was applied, in conjunction with gas chromatography–mass spectrometry, to the analysis of volatile organic compounds (VOCs) in human breath samples without requiring exhaled breath condensate collection. A new procedure, exhaled breath vapor (EBV) collection, involving the active sampling and preconcentration of a breath sample with a SPME fiber fitted inside a modified commercial breath-collection device, the RTube™, is described. Immediately after sample collection, compounds are desorbed from the SPME fiber at 250 °C in the GC-MS injector. Experiments were performed using EBV collected at −80 °C and at room temperature, and the results compared to the traditional method of collecting exhaled breath condensate at −80 °C followed by passive SPME sampling of the collected condensate. Methods are compared in terms of portability, ease-of-use, speed of analysis, and detection limits. The need for a clean air supply for the study subjects is demonstrated using several localized sources of VOC contaminants including nail polish, lemonade, and gasoline. Various simple methods to supply clean inhaled air to a subject are presented. Chemical exposures are used to demonstrate the importance of providing cleaned air (organic vapor respirator) or an external air source (tubing stretched to a separate room). These techniques allow for facile data interpretation by minimizing background contaminants. It is demonstrated herein that this active SPME breath-sampling device provides advantages in the forms of faster sample collection and data analysis, apparatus portability and avoidance of power or cooling requirements, and performance for sample collection in a contaminated environment.      

Breathing Rhythm Variations during Wash-In Do Not Influence Exhaled Volatile Organic Compound Profile Analyzed by an Electronic Nose

E-noses are innovative tools used for exhaled volatile organic compound (VOC) analysis, which have shown their potential in several diseases. Before obtaining a full validation of these instruments in clinical settings, a number of methodological issues still have to be established. We aimed to assess whether variations in breathing rhythm during wash-in with VOC-filtered air before exhaled air collection reflect changes in the exhaled VOC profile when analyzed by an e-nose (Cyranose 320). We enrolled 20 normal subjects and randomly collected their exhaled breath at three different breathing rhythms during wash-in: (a) normal rhythm (respiratory rate (RR) between 12 and 18/min), (b) fast rhythm (RR > 25/min) and (c) slow rhythm (RR < 10/min). Exhaled breath was collected by a previously validated method (Dragonieri et al., J. Bras. Pneumol. 2016) and analyzed by the e-nose. Using principal component analysis (PCA), no significant variations in the exhaled VOC profile were shown among the three breathing rhythms. Subsequent linear discriminant analysis (LDA) confirmed the above findings, with a cross-validated accuracy of 45% (p = ns). We concluded that the exhaled VOC profile, analyzed by an e-nose, is not influenced by variations in breathing rhythm during wash-in.     

多批次肝衰竭患者呼出气体的电喷雾萃取电离质谱检测及代谢组学数据分析

采用高分辨电喷雾萃取电离质谱(EESI-MS)技术对肝衰竭患者和健康志愿者呼出气体样本进行快速检测, 结合多块偏最小二乘分析(MB-PLS)方法, 对多批次获取的呼出气体代谢数据进行统计建模分析, 并与传统的PLS方法进行比较. 结果表明, MB-PLS方法能有效消除批次差异对统计建模的影响. 此外, 利用MB-PLS模型变量VIP值对变量进行筛选, 可降低数据的冗余, 消除无关变量对模型的影响, 从而有效提高了模型的性能.     

The influence of blood sample storage time on the propofol concentration in plasma and solid blood elements

In order to describe the changes of propofol concentration in whole blood and in its components during the blood storage we examined venous blood samples collected from patients anaesthetized either with or without propofol. Blood samples from patients anaesthetized without propofol were spike with propofol 45 min before analysis. Propofol concentration was examined in whole blood, plasma, rinsed formed elements and rinsed and lysed formed blood elements by means of HPLC after 1, 4, 7, 13, 21, 25 and 28 days of storage. There was significant decrease in plasma concentration of propofol during the first few days of sample storage followed by its increase during subsequent days. The opposite phenomenon was observed for formed blood elements. The findings support the hypothesis that propofol distribution between blood components changes in time.     

Investigation of acetone,butanol and carbon dioxide as new breath biomarkers for convenient and noninvasive diagnosis of obstructive sleep apnea syndrome

The objective of the present study was to investigate whether analysis of carbon dioxide, acetone and/or butanol present in human breath can be used as a simple and noninvasive diagnosis method for obstructive sleep apnea syndrome (OSAS). For this purpose, overnight changes in the concentrations of these breath molecules were measured before and after sleep in 10 patients who underwent polysomnography and were diagnosed with OSAS, and were compared with the levels of these biomarkers determined after sleep in 10 healthy subjects. The concentrations of exhaled carbon dioxide were measured using external cavity laser‐based off‐axis cavity enhanced absorption spectroscopy, whereas the levels of exhaled acetone and butanol were determined using thermal desorption gas chromatography mass spectrometry. We observed no significant changes in the levels of exhaled acetone and carbon dioxide in OSAS patients after sleep compared with pre‐sleep values and compared with those in healthy control subjects. However, for the first time, to our knowledge, analyses of expired air showed an increased concentration of butanol after sleep compared with that before sleep and compared with that in healthy subjects. These results suggest that butanol can be established as a potential biomarker to enable the convenient and noninvasive diagnosis of OSAS in the future.     

The advantages of cell lysis before blood sample preparation by extraction for HPLC propofol analysis

Propofol (2,6-diisopropylphenol) is a short-acting drug with a large volume of distribution and high body clearance. It is suitable both for the induction of anaesthesia by bolus injection and the maintenance of anaesthesia by repeated injections or a continuous infusion. Examining the drug concentration its analysis in whole blood is recommended. This results from the fact that propofol molecules strongly bind with plasma proteins and cellular blood constituents and blood composition variations are observed between individuals or in different disease states or resulting from transfusion etc. In most cases the HPLC analysis follows the extraction of samples. The degree of propofol binding with blood cells can be different, depending on the blood type, and it can change in time, which may affect the results of the analysis. The paper discusses and shows the necessity of blood cell lysis before the extraction procedure. The cell lysis makes possible to determine the total amount of propofol in blood independently of the degree of propofol binding with cellular blood constituents and its changes.     

Direct, rapid quantitative analyses of BVOCs using SIFT-MS and PTR-MS obviating sample collection

The purpose of this short review is to describe the origins and the principles of operation of selected-ion flow-tube mass spectrometry (SIFT-MS) and proton-transfer-reaction mass spectrometry (PTR-MS), and their application to the analysis of biogenic volatile organic compounds (BVOCs) in ambient air, the humid air (headspace) above biological samples, and other samples. We briefly review the ion chemistry that underpins these analytical methods, which allows accurate analyses. We pay attention to the inherently uncomplicated sampling methodologies that allow on-line, real-time analyses, obviating sample collection into bags or onto traps, which can compromise samples.Whilst these techniques have been applied successfully to the analysis of a wide variety of media, we give just a few examples of data, including for the analysis of BVOCs that are present in tropospheric air and those emitted by plants, in exhaled breath and in the headspace above cell and bacterial cultures (which assist clinical diagnosis and therapeutic monitoring), and the products of combustion. The very wide dynamic ranges of real-time analyses of BVOCs in air achieved by SIFT-MS and PTR-MS - from sub-ppbv to tens of ppmv - ensure that these analytical methods will be applied to many other media, especially when combined with gas-chromatography methods, as recently trialed.     

HPLC investigation of free and bound propofol in human plasma and cerebrospinal fluid

The paper compares the total propofol concentration in the cerebrospinal fluid (CSF) with the free drug concentration in plasma measured in 35 humans scheduled for elective neurosurgical procedures during propofol anaesthesia. The concentrations of total and free propofol in the blood and CSF samples were measured by means of HPLC using liquid-liquid extraction and ultrafiltration in the sample preparation procedure. The arterial blood and CSF samples (collected from intraventricular drainage) were taken at the same time. According to the obtained results, the usually expected equality between free drug concentration in plasma and its total concentration in CSF is not valid for propofol: the unbound propofol concentration in plasma is not equal to its total concentration in CSF (p < 0.05). This difference suggests a substantial contribution of active transport in propofol transfer from blood into CSF. Moreover, the paper shows the presence of bound propofol in CSF, which is a novel finding.     

Time course of ethanol and propofol exhalation after bolus injection using ion molecule reaction–mass spectrometry

The transit of ethanol from blood to breath gas is well characterised. It is used for intraoperative monitoring and in forensic investigations. A further substance, which can be measured in breath gas, is the phenol propofol. After a simultaneous bolus injection, the signals (time course and amplitude) of ethanol and propofol in breath gas were detected by ion molecule reaction–mass spectrometry (IMR-MS) and compared. After approval by the regional authorities, eight pigs were endotracheally intubated after a propofol-free induction with etomidate. Boluses of ethanol (16 μg/kg) and propofol (4 or 2 mg/kg) were infused alone and in combination. For both substances, breath gas concentrations were continuously measured by IMR-MS; the delay time, time to peak and amplitude were determined and compared using non-parametric statistic tests. IMR-MS allows a simultaneous continuous measurement of both substances in breath gas. Ethanol appeared (median delay time, 12 vs 29.5 s) and reached its peak concentration (median time to peak, 45.5 vs 112 s) significantly earlier than propofol. Time courses of ethanol and propofol in breath gas can be simultaneously described with IMR-MS. Differing pharmacological and physicochemical properties of the two substances can explain the earlier appearance and time to peak of ethanol in breath gas compared with propofol.