Special issue on Human Breath Analysis IEEE Sensors Journal 2010, 10 (1)

Editorial The Future of Sensors and Instrumentation for Human Breath Analysis Davis, C. E. Frank, M. Mizaikoff, B. Oser, H.

What is Normal Breath? Challenge and Opportunity Solga, S. F. Risby, T. H.

Breath Analyzer for Alcolocks and Screening Devices Hok, B. Pettersson, H. Kaisdotter Andersson, A. Haasl, S. Akerlund, P. Abstract Alcolocks and alcohol screening devices are becoming commonplace, and their use is expected to grow rapidly with cost reduction and improved usability. A new breath analyzer prototype is demonstrated, with the prospects of eliminating the mouthpiece, reducing expiration time and volume, improving long-term stability, and reducing life cycle cost. Simultaneous ${hbox {CO}}_{2}$ measurements compensate for the sample dilution and unsaturated expiration. Infrared transmission spectroscopy is used for both the alcohol and ${hbox {CO}}_{2}$ measurement, yet the entire system is contained within a small handheld unit. Experimental results are reported on the device sensitivity, linearity, resolution, and influence from varying measuring distance. The correlation between early and full-time sampling was established in 60 subjects. Basic concept verification was obtained, whereas resolution and selectivity still needs to be improved. Further improvements are expected by system optimization and integration.

A Novel MEMS Respiratory Flow Sensor Wei, C.-L. Lin, C.-F. Tseng, I.-T. Abstract A novel CMOS-process-compatible MEMS sensor for monitoring respiration is presented. This resistive flow sensor was manufactured by the TSMC 0.35 $mu{hbox {m}}$ CMOS/MEMS mixed-signal 2P4M Polycide process. The sensor was demonstrated to be sensitive enough to detect the respiratory flow rate, and the relationship between flow rate and sensed voltage is quite linear. If one can integrate the sensor with its sensing circuit into a single chip, the cost of a pneumotach system can be greatly reduced. Moreover, the proposed sensor is useful in both invasive and noninvasive applications.

Effect of Exhalation Variables on the Current Response of an Enzymatic Breath Acetone Sensing Device Landini, B. E. Bravard, S. T. Abstract The effect of simulated breath flow rate, vapor temperature, and flow duration on the linearity and variation in the current response of an enzymatic electrochemical breath acetone sensor was examined. Variable simulated flow rate and vapor temperature only slightly increased the variation in the overall sensor current response to vapor acetone, while the response remained linear with acetone concentration. This increased variation was measured by a slightly decreased linear ${R}^{2}$ compared to simulated breath under constant control conditions. Simulated variable flow duration increased the variation in sensor response, especially for blow times less than 5 s at vapor acetone concentrations less than 1 ppm (v/v). This trend with flow duration was reflected in data produced during human breath testing. In all cases, the sensor current response remained linear with vapor acetone concentration. In a clinical test, the sensor current displayed a linear dependence on human breath acetone concentrations ranging from 0.2 to 17 ppm (v/v), as measured by gas chromatography. The linear ${R}^{2}$ across 201 direct human breath measurements was 0.949.

Spirometric Measurement Postprocessing: Expiration Data Recovery Lay-Ekuakille, A. Vendramin, G. Trotta, A. Abstract Spirometry deals with finding and predicting respiratory system pathologies through instrumentation that mainly carries out measurements on the volume and the air flow expired from lungs. In many cases, during spirometric and pneumotachographic trials in hospital, there are people who are not able to begin or to complete their tests because of diverse difficulties due to presumable pathologies. Hence, these trials may be lost if they are not recovered and postprocessed in adequately, at least to display the expiration trend and step. This paper presents rapid techniques of helping physiopathologists to extract information from a noncomplete expiration curve as spirometric postprocessing. The two techniques are based on work of breath (WOB) and controlled genetic algorithm (CGA), respectively. A comparison is performed between the two techniques; the WOB is calculated by assuming classes of fixed resistance R according to the age, to the sex, to the previous pathologies, etc., while the CGA technique provides a strict monitoring of GA steps in order to reduce uncertainty of final results.

1 Enhancement of Ethanol Sensing Properties by Impregnating Platinum on Surface of ZnO Tetrapods Hongsith, N. Choopun, S. Abstract ZnO tetrapods with a cross-sectional size of about 200–1000 nm were synthesized via an oxidation reaction technique. The sensors based on ZnO tetrapods and platinum impregnated ZnO tetrapods were fabricated and investigated for ethanol sensing properties. The gas sensing properties of the sensors were investigated for ethanol concentration of 50–1000 ppm at different operating temperatures. It was found that the sensitivities of platinum impregnated ZnO tetrapod sensors were higher than that of pure ZnO tetrapod sensors. The enhancement of sensitivity due to platinum impregnation to ZnO tetrapods may be explained either by an increase of adsorbed oxygen density or an increase of reaction rate coefficient in a rate equation for an ethanol adsorption reaction on the ZnO surface. Also, the slope value of the plot between $log(S-1)$ and $log C$ suggested that adsorbed oxygen ion species at the surface of the platinum impregnated ZnO tetrapods was $O^{2-}$ which was the same as pure ZnO tetrapods. Finally, these results have an important implication for a development of ethanol sensors based on metal oxide semiconductors for alcohol breath analyzers.

Enhancement of Ethanol Sensing Properties by Alloying ${rm TiO}_{2}$ With ZnO Tetrapods Santhaveesuk, T. Wongratanaphisan, D. Choopun, S. Abstract The ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ tetrapods were synthesized using simple thermal oxidation method from Zn and ${rm TiO}_{2}$ mixture. The tetrapods exhibited single crystalline hexagonal wurtzite structure with the prefer growth direction of $[0002]$ along the legs. The sensors based on ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ tetrapods were fabricated and investigated the ethanol sensing properties. The FE-SEM, HRTEM, SAED, XRD, and RS results suggested that ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ alloy was formed with a slightly decrease of c-axis lattice parameter. The decrease of sensor resistance under ethanol atmosphere was observed and suggested that the ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ tetrapods possessed n-type property of semiconductor similar to ZnO. The ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ tetrapod sensors exhibited higher sensitivity than that of pure ZnO tetrapod sensors for entire ethanol concentration with optimum operating temperature of 300 $^{circ}{rm C}$. Thus, the enhancement of sensitivity due to alloying ${rm TiO}_{2}$ with the ZnO tetrapods was observed and maybe explained by an increase of adsorbed oxygen ions due to substitution of Ti atom into Zn atom. Also, the slope value of the plot between $log (S-1)$ and $log C$ suggested that adsorbed oxygen ion species at the surface of the ${rm Ti}_{x} {rm Zn}_{1-x}{rm O}$ tetrapods was ${rm O}^{2-}$ which was same as pure ZnO tetrapods. Finally, these results have an important implication for a development of ethanol sensors based on metal oxide semiconductors for alcohol breath analyzer.

Daily Monitoring of Asthmatics by Means of Individual Devices for Exhaled Breath Temperature Measurement Popov, T. A. Kralimarkova, T. Z. Lazarova, C. T. Tzachev, C. T. Dimitrov, V. D. Gill, J. Abstract It has been suggested that inflamed airways may increase the exhaled breath temperature (EBT). We designed a simple instrument for EBT measurement and proven its precision, reproducibility and validity in asthma. Now we tested its utility as individual device to detect changes indicative of the control of asthma. We followed up 14 patients (9 female, age range 29–68 years) with uncontrolled asthma for 3 weeks after stepping up their anti- inflammatory treatment. Subjects were assessed upon inclusion in the study (visit 1, V1), after 1 (V2) and 3 weeks of treatment (V3) by visual-analogue scale (VAS), spirometry, blood and sputum eosinophils (Eos) and EBT. They also kept diaries with symptom scores (SS), peak expiratory flow (PEF) and EBT. Compared with V1, EBT decreased significantly at V2 and V3: from 35, 20 $^{circ}{rm C}$ [ $34 , 36div 35 , 56$] (median [$25div 75$ interquartile range]) to 34, 70$^{circ}{rm C}$ [$34 , 48div 34 , 95$] and 34,50 $^{circ}{rm C}$ [ $33 , 94div 34 , 91$] respectively, ${rm p}=0.017$. These changes paralleled the alteration in the other indices of asthma control. The mean weekly EBT and SS significantly decreased between week 1 and week 3 ( ${rm p}=0.035$ and 0.003 respectively), while PEF increased ( ${rm p}=0.027$). In conclusion, EBT is a useful indicator of- asthma control to be used by physicians, but also by individual subjects at home.

Nanosensor and Breath Analyzer for Ammonia Detection in Exhaled Human Breath Gouma, P. Kalyanasundaram, K. Yun, X. Stanacevic, M. Wang, L. Abstract The detection and monitoring of gases in exhaled human breath up to date has been limited by the lack of appropriate materials and technologies which could rapidly and selectively identify the presence and monitor the concentration of trace levels of specific analytes-biomarkers. We present a metal oxide-based nanosensor that is highly specific to ammonia gas in breath-simulating environments at low part-per-billion concentrations. The design of a handheld breath analyzer for gas detection in exhaled human breath is described. Semiconducting ceramics are presented as suitable sensor materials for easy and affordable noninvasive diagnostics.

2 A Study on Breath Acetone in Diabetic Patients Using a Cavity Ringdown Breath Analyzer: Exploring Correlations of Breath Acetone With Blood Glucose and Glycohemoglobin A1C Wang, C. Mbi, A. Shepherd, M. Abstract Acetone is qualitatively known as a biomarker of diabetes; however, the quantitative information on acetone concentration in diabetic breath is incomplete, and the knowledge of correlations of breath acetone with diabetic diagnostic parameters, namely, blood glucose (BG) and glycohemoglobin A1C (A1C), are unknown. We utilized a pilot-scale breath acetone analyzer based on the cavity ringdown spectroscopy (CRDS) technique to conduct breath tests with 34 Type 1 diabetic (T1D), ten Type 2 diabetic (T2D) patients, and 15 apparently healthy individuals. Relations between breath acetone and BG, A1C, and several other bio indices, such as the type of diabetes, onset-time, gender, age, and weight were investigated. Our observations show that a linear correlation between the mean group acetone and the mean group BG level does exist $({rm R} = 0.98, {rm P} ≪ 0.02)$ when all the T1D subjects tested are grouped by different BG levels, 40–100, 101–150, 151–200, and 201–419 mg/dL. Similarly, among the T1D subjects studied, when their A1C's are grouped by $≪ $7, 7–9.9, and 10–13, a linear correlation between the mean group A1C and the mean group acetone concentration is observed $({rm R} = 0.99, {rm P} ≪ 0.02)$. No strong correlations are observed when the BG and A1C numbers are not grouped. The mean breath acetone concentration in the T1D subjects studied in this work is determined to be 2.19 ppmv (parts per million by volume), which is higher than the mean breath acetone concentration, 0.48 ppmv, in the 15 healthy people tested.

Wireless Detection System for Glucose and pH Sensing in Exhaled Breath Condensate Using AlGaN/GaN High Electron Mobility Transistors Chu, B. H. Kang, B. S. Chang, C. Y. Ren, F. Goh, A. Sciullo, A. Wu, W. Lin, J. Gila, B. P. Pearton, S. J. Johnson, J. W. Piner, E. L. Linthicum, K. J. Abstract Peltier element cooling of ungated AlGaN/GaN high electron mobility transistors (HEMTs) is shown to be an effective method for condensing exhaled breath, enabling the measurement of the pH and glucose of the exhaled breath condensate (EBC). By comparison with standard solutions, the current change measured in the HEMTs with EBC shows that the sensitivity of the glucose detection is lower than the glucose concentration in the EBC of healthy human subjects and the pH of the condensate from the exhaled breath is within the range of 7–8, typical of that for human blood. The HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. Details of the transmitter and receiver design for the transmission system are given. Our work demonstrates the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology without the need for clinical visits.

Distinguishing Methicillin-Resistant and Sensitive Staphylococcus aureus Using Volatile Headspace Metabolites Jia, B. Sohnlein, B. Mortelmans, K. Coggiola, M. Oser, H. Abstract This proof-of-concept study used solid-phase microextraction fibers (SPME) to collect headspace vapors from a methicillin sensitive Staphylococcus aureus (MSSA) and a methicillin-resistant Staphylococcus aureus (MRSA) strain grown in vitro in liquid growth medium. The collected molecules were separated and identified using gas chromatography and mass spectrometry (GC/MS). Preliminary results distinguished these two strains and provide a foundation for a biomarker library that could one day serve as a diagnostic tool for identifying specific bacterial infections.

Multicomponent Breath Analysis With Infrared Absorption Using Room- Temperature Quantum Cascade Lasers Shorter, J. H. Nelson, D. D. McManus, J. B. Zahniser, M. S. Milton, D. K. Abstract Breath analysis is a powerful noninvasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO) and carbon monoxide (CO) are markers of airway inflammation and can indicate the extent of respiratory diseases. We have developed a compact fast response laser system for analysis of multiple gases by infrared absorption. The instrument uses room temperature quantum cascade lasers to simultaneously measure NO, CO, carbon dioxide $({hbox {CO}}_{2})$ and nitrous oxide $({hbox {N}}_{2}{hbox {O}})$ in exhaled breath. Four breath flow rates are employed to explore their exchange dynamics in the lungs and airways. We obtain 1-s detection precisions of 0.5-0.8 parts- per-billion (ppb) for NO, CO, and ${hbox {N}}_{2}{hbox {O}}$ with an instrument response time of less than 1 s. The breath analysis system has been demonstrated in a preliminary study of volunteers. It is currently deployed in a trial clinical study. 3 Analysis of Breath and Skin Gases Emanating During Exercise Using an Original Biogas Sampling System Connected to an Atmospheric Pressure Ionization Mass Spectrometer Shimouchi, A. Nose, K. Shirai, M. Abstract Cardiopulmonary exercise testing is widely used in the field of sports and clinical medicine. Among the indices for evaluating exercise capacity, the anaerobic threshold is one of the most important parameters, often represented by the ventilatory threshold. The threshold, however, is sometimes not easy to determine. Yet, while more than several thousands kinds of chemical have been detected in human breath, there have been relatively few reports about the chemicals released within skin gas. In the present paper, we examined human breath and skin gas mass spectra data to explore the chemical compounds associated with anaerobic metabolism during exercise. Six healthy men, breathing purified artificial air via a two-way valve mouth piece and performing incremental bicycle ergometer exercises, were studied. Their breath was continuously analyzed using an atmospheric pressure ionization mass spectrometer (APIMS). On separate experimental days, skin gas from the palms of five subjects during the same exercise routine was monitored by an originally developed skin gas sampling system connected to the APIMS. The API mass spectra (represented by ion intensities at ${m}/{z} = {3} - {200}$ ) indicated numerous changing patterns between subject rest, warm up, ramp exercise and recovery periods. The exercise states caused remarkable increases to ion intensity. This was to within 7 and 6 kinds of m/z for breath and skin gas respectively. During recovery, by contrast, ion intensities gradually decreased. The changing ion intensity patterns displayed some similarity to oxygen consumption patterns.

Application of Similarity Coefficients to Predict Disease Using Volatile Organic Compounds Smith, S. White, P. Redding, J. Ratcliffe, N. M. Probert, C. S. J. Abstract Measures of similarity are used to provide evidence in support of the conjecture that the presence and absence profile of a subset of volatile organic compounds found in urine differ between healthy (non-prostate cancer) male donors and prostate cancer donors.

Non-Imaging Optical Method for Multi-Sensing of Gases Based on Porous Silicon Hutter, T. Ruschin, S. Abstract We demonstrate an optical sensor for the detection of ammonia in gaseous phase under a changing humidity environment. The sensor is based on a sectioned nano-structured porous silicon (PSi) device in which the parts react distinctly to ammonia and water vapor. The distinct sensing is necessary since most ammonia indicators' sensitivities are highly dependent on the ambient relative humidity. The sensor is interrogated with a single white- light beam, and changes in the reflectivity sensor are monitored. The combined interference pattern from both PSi sections is observed and measured under various concentrations of ammonia and water vapor. The structure is designed to frequency encode the reflectivity spectrum and Fourier-transform data-analysis is applied in order to enable simple discrimination between different ammonia and water vapor concentrations. The method allows remote and distance-insensitive analysis of gases in breath and other gaseous environments.

Determination of Blood Glucose Level-Based Breath Analysis by a Quartz Crystal Microbalance Sensor Array Saraoglu, H. M. Kocan, M. Abstract This paper aims to determine human blood glucose levels through analyzing the acetone present in exhaled breath as a noninvasive method with the help of an electronic nose system based on quartz crystal microbalance (QCM) sensors. The amount of acetone vapor which is the marker of blood glucose is 0.1–10 ppm in human expiration. In order for the QCM sensors to sense low levels of acetone concentration, a condenser containing zeolite absorbent ingredients is used in the experiment mechanism. The QCM sensor data obtained from breath is compared with blood glucose value. A data set of 40 volunteers with blood glucose values ranging from 84.83 mg/dl to 334 mg/dl was examined in this paper. An artificial neural network (ANN) trained using the Levenberg–Marquardt (LMNN) algorithm was developed. Data from 31 of the volunteers was used for training the ANN and data from nine volunteers was reserved for testing. Eventually, result of the study has an error of 20.13%.

4 Development of an Individual Device for Exhaled Breath Temperature Measurement Popov, T. A. Kralimarkova, T. Z. Tzachev, C. T. Dunev, S. S. Dimitrov, V. D. Gill, J. Abstract Different thermometers have been constructed over the decades to measure the temperature of the body to help detect and monitor morbid states. They yield slightly different estimates of the core body temperature depending on the proximity of the measurement site to the internal milieu of the organism, the principle of temperature assessment, and the specific characteristics of the gauging devices. Evaluation of the exhaled breath temperature (EBT) has been recently suggested as a new method to detect inflammatory processes in the conducting airways due to changes in the blood flow perfusion of their walls and adjacent structures. While the first reported EBT experiments required sealed laboratory environment and sophisticated equipment, we designed a simple handheld instrument for EBT measurement and proven its precision, reproducibility and validity in subjects with asthma. We now describe the construction principles of our instrument, the procedure to test the fitness for purpose of the separate units and the novel features of the newest prototypes outfitted with microprocessor and memory. We also outline the potential clinical applications of an individual device for EBT measurement.

Analysis of Volatile and Non-Volatile Biomarkers in Human Breath Using Differential Mobility Spectrometry (DMS) Davis, C. E. Bogan, M. J. Sankaran, S. Molina, M. A. Loyola, B. R. Zhao, W. Benner, W. H. Schivo, M. Farquar, G. R. Kenyon, N. J. Frank, M. Abstract Exhaled human breath contains thousands of chemicals that are potential biomarkers of disease or chemical exposure. Although many bench-top analytical instruments could measure concentrations of these chemicals, small and portable systems have the best advantage of being used in a clinical point-of-care environment or in a field setting. Here, we demonstrate coupling a miniature differential mobility spectrometer (DMS) with both a gas chromatograph (GC) and separately an electrospray ionization (ESI) module to analyze exhaled breath condensate. Our combined GC/DMS and ESI/DMS instrument systems are capable of measuring an extremely large number of chemical analytes contained in exhaled breath condensate. We have established methodologies for detecting single compounds and approximate the limits of detection for our systems. The detection limit and analytical power are clinically relevant for many potential biomarkers, and suggests our device may have many applications for disease diagnostics in human breath analysis.

Endogenous Levels of Five Fatty Acid Metabolites in Exhaled Breath Condensate to Monitor Asthma by High-Performance Liquid Chromatography: Electrospray Tandem Mass Spectrometry Nording, M. L. Yang, J. Hegedus, C. M. Bhushan, A. Kenyon, N. J. Davis, C. E. Hammock, B. D. Abstract Airway inflammation characterizing asthma and other airway diseases may be monitored through biomarker analysis of exhaled breath condensate (EBC). In an attempt to discover novel EBC biomarkers, a high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method was used to analyze EBC from ten control non-asthmatics and one asthmatic individual for five fatty acid metabolites: 9,12,13-trihydroxyoctadecenoic acid (9,12,13-TriHOME), 9,10,13-TriHOME, 12,13- dihydroxyoctadecenoic acid (12,13-DiHOME), 12-hydroxyeicosatetraenoic acid (12-HETE), and 12(13)- epoxyoctadecenoic acid (12(13)-EpOME). The method was shown to be sensitive, with an on-column limit of quatitation (LOQ) in the pg range (corresponding to pM concentrations in EBC), and linear over several orders of magnitude for each analyte in the calibrated range. Analysis of EBC spiked with the five fatty acid metabolites was within 81%–119% with only a few exceptions. Endogenous levels in EBC exhibited intra- and inter-assay precision of 10%–22%, and 12%–36%, respectively. EBC from the healthy subjects contained average analyte levels between 15 and 180 pM with 12-HETE present above the LOQ in only one of the subjects at a concentration of 240 pM. Exposure of the asthmatic subject to allergen led to increased EBC concentrations of 9,12,13-TriHOME, 9,10,13-TriHOME, 12,13-DiHOME, and 12(13)-EpOME when compared to levels in EBC collected prior to allergen exposure (${rm range}=$40–510 pM). 12,13-DiHOME was significantly increased (Student's t-test, $p≪0.05$ ). In conclusion, we have developed a new HPLC-ESI-MS/MS method for the analysis of five fatty acid metabolites in EBC, which are potential biomarkers for asthma monitoring and diagnosis.

Design and Development of a Breath Acetone MOS Sensor for Ketogenic Diets Control Neri, G. Bonavita, A. Micali, G. Donato, N. Abstract The design of a handy and noninvasive measurement of acetone in the human breath, which is useful for ketosis monitoring and control, by means of MOS sensors is reported. For this aim, highly sensitive resistive sensors in thick film configuration, fabricated depositing sensing layers of ${{hbox {In}}}_{2}{hbox {O}} _{3}$ and Pt-${{hbox {In}}}_{2}{hbox {O}} _{3}$ nanopowders by screen-printing, have been developed. The devices were calibrated using standard gases in the laboratory, showing high sensitivity and a linear response in the range of acetone 5 concentration investigated (1–100 ppm). The results obtained indicate that MOS sensors based on Pt-${{hbox {In}}}_{2}{hbox {O}} _{3}$ nanopowders are promising as fast and quantifiable means of determining acetone in the breath, posing the advantages of real time measurements and low costs devices for the control of ketogenic diets.

Microsensors in Dynamic Backgrounds: Toward Real-Time Breath Monitoring Benkstein, K. D. Raman, B. Montgomery, C. B. Martinez, C. J. Semancik, S. Abstract We evaluated a microelectromechanical systems (MEMS) microsensor array with temperature-controlled chemi- resistive elements for use as a noninvasive clinical diagnostic tool to detect the presence or absence of trace amounts of disease biomarkers in simulated breath samples. The microsensor environment was periodically altered between air (78% ${hbox {N}}_{2}$, 21% ${hbox {O}}_{2}$ by volume, 20% relative humidity) and simulated breath (77% ${hbox {N}}_{2}$, 16% ${hbox {O}}_{2}$, 4% ${hbox {CO}}_{2}$ by volume, 80% relative humidity) samples creating a dynamic background. Acetone, a disease marker for diabetes, was spiked into select simulated breath samples at relevant concentrations ( $0.5~mu{hbox {mol/mol}}$ to $8~mu{hbox {mol/mol}}$) to pose a diagnostic problem for the sensor array. Using standard statistical dimensionality reduction and classification algorithms, we compared the ability of a variety of sensing materials to detect and recognize the disease marker. Our analyses indicate that the porous, doped nanoparticle materials (${hbox {Sb}}$:${hbox {SnO}}_{2}$ microshell films and ${hbox {Nb}}$ :${hbox {TiO}}_{2}$ nanoparticle films) are best for the recognition problem (acetone present versus absent), but that ${hbox {WO}}_{3}$ and ${hbox {SnO}}_{2}$ films are better at the quantification task (high versus low concentrations of acetone).

Potential and Challenges for Mid-Infrared Sensors in Breath Diagnostics Kim, S.-S. Young, C. Vidakovic, B. Gabram-Mendola, S. G. A. Bayer, C. W. Mizaikoff, B. Abstract Exhaled breath contains more than 1000 constituents at trace level concentrations, with a wide variety of these compounds potentially serving as biomarkers for specific diseases, physiologic status, or therapeutic progress. Some of the compounds in exhaled breath (EB) are well studied, and their relationship with disease pathologies is well established. However, molecularly specific analysis of such biomarkers in EB at clinically relevant levels remains an analytical and practical challenge due to the low levels of such biomarkers frequently below the ppb (v/v) range in EB. In this contribution, mid-infrared (MIR) spectroscopic sensing techniques are reviewed for potential application in breath diagnostics. While the spectral regime from 3–20 $mu{rm m}$ has already been utilized for fundamental studies on breath analysis, significant further improvements are in demand for substantiating MIR spectroscopy and sensing techniques as a suitable candidate for clinically deployable breath analyzers. Several advantageous features including inherent molecular selectivity, real-time monitoring capability, comparable ease of operation, potentially low costs, and a compact device footprint promise reliable optical diagnostics in the MIR. Hence, while the application of MIR spectroscopy and sensing systems to breath analysis yet appear in their infancy, recent progress on advanced MIR light sources, waveguides, and device concepts forecasts next-generation optical sensing platforms suitable for addressing the challenges of in situ breath diagnostics.

DNA-Coated Nanosensors for Breath Analysis Johnson, A. T. C. Khamis, S. M. Preti, G. Kwak, J. Gelperin, A. Abstract The analysis of breath and body odors can provide valuable information relevant to disease detection, diagnosis and treatment. A variety of technical developments are being pursued to develop electronic devices intended to analyze volatile components of breath and body odors with the sensitivity, selectivity, and learning ability of high- end mammalian olfactory systems. Here, we describe a new sensor technology that has the potential to supply a large set of diverse and sensitive odorant sensors with electronic readout to provide information-rich odorant- elicited signals for analysis by pattern recognition algorithms. In addition, we demonstrate that these sensors can provide discrimination of odorant homologues consisting of aldehydes and organic acids commonly found in human breath and other body emanations over a range of concentrations.

Membrane Extraction With a Sorbent Interface and Gas Chromatography for the Characterization of Ethylene in Human Breath Morley, M. Pawliszyn, J. Abstract Membrane extraction with a sorbent interface (MESI) is a sample preparation technique with a rugged and simple design allowing for solvent-free, on-line performance. When coupled to gas chromatography (GC), MESI is extremely promising for the analysis of volatile organic compounds (VOCs), as it is selective and sensitive enough to detect trace levels of analytes. A new calibration method for the MESI technique is presented herein. The aim of this study was to characterize and quantify the breath biomarker ethylene in human subjects. The dominant calibration method was proven true using standard ethylene to verify changes in mass transfer trends, with variations in flow and temperature. Finally, the dominant calibration method was used to determine ethylene levels in real human breath samples from healthy and smoking volunteers. Results were consistent with those reported in

6 literature. These findings suggest that the dominant calibration technique is a useful tool for monitoring ethylene in human breath.

The Effect on the Gas Selectivity of CNT-Based Gas Sensors by Binder in SWNT/Silane Sol Solution Kim, S. J. Abstract We investigated that CNT-based gas sensors could be sensitized selectively by changing binders contained in SWNTs/silane sol solution. To do this, we fabricated CNT-based gas sensors that consisted of a SWNTs/silane hybrid thin film deposited by multiple spray-coating, and we examined the electrical response for alcohol vapor gas from the sensor which is applicable to an alcohol breath analyzer. Generally, silane binders are mixed in CNT solution to adhere CNTs to substrates well, and they can be easily functionalized to each group on the surface of CNTs after they are hardened by way of the hydrolysis reaction. Therefore, the response property to a special gas will be changed if the binder in the solution is different. Here, we compared the effect of TEOS with MTMS as a binder. As a result, we observed that the resistance in the sensors using TEOS decreased dramatically while it decreased scarcely in the sensors using MTMS for increasing alcohol concentrations.

Miniaturized Wireless Sensing System for Real-Time Breath Activity Recording Andre, N. Druart, S. Gerard, P. Pampin, R. Moreno-Hagelsieb, L. Kezai, T. Francis, L. A. Flandre, D. Raskin, J.-P. Abstract A portable, non-invasive and easy to operate wireless system has been developed for monitoring the breathing activity of patient. The system is composed of a capacitive microsensor (airflow-humidity sensor) integrated on a silicon chip and of a Negative Temperature Coefficient thermistor; both are connected to a wireless network to allow efficient healthcare at home as well as in hospitals. The capacitive sensitive part of the microsensor is an array of interdigitated metallic electrodes covered by 100-nm-thick dense anodized aluminum oxide layer. The breath water vapor is adsorbed over the interdigitated electrodes and changes the sensor characteristic capacitance by up to two orders of magnitude. This modulated signal is then digitized and either stored in a memory or directly transmitted to a monitor through a short distance radio frequency (RF) link. Results show that the wireless platform can be powered by two AAA batteries and deployed in a mesh or star configuration as wireless sensor network. Full size of the microsensor is less than 1 ${rm cm}^{2}$ and is conveniently implemented in a classical adhesive bandage or in nasal prongs. This microsystem is proposed for monitoring sleep-disordered breathing as well as breathing rhythm of athletes during effort.

Evidence for Cancer Biomarkers in Exhaled Breath Szulejko, J. E. McCulloch, M. Jackson, J. McKee, D. L. Walker, J. C. Solouki, T. Abstract A Review: Cancer cell growth releases molecular biomarkers into blood that can be useful in diagnostic tests, e.g., serum biomarkers. The use of serum biomarkers involves an invasive sample collection procedure. Human exhaled breath is potentially a noninvasive source of cancer biomarker compounds. A few breath analysis studies have reported sensitivities $>$ 90% and specificities $>$ 80% using a suite of exhaled breath biomarkers to differentiate cancer subjects from controls. A significant challenge for establishing breath analysis as a feasible cancer diagnostic procedure is the lack of validated diagnostic procedure. We found over 2000 breath-related studies published since circa 1900 reporting on a wide variety of breath chemical analysis methods and diagnostic findings; only a small fraction of these studies were directly related to cancer molecular biomarkers in breath. Compared to other detectors and separation techniques, mass spectrometry and gas chromatography are most suitable techniques for breath analysis. Compounds detectable in exhaled breath, with potential diagnostic utility in cancer detection, include small gaseous molecules, volatile organic compounds, proteins, and DNA. The types of cancers previously investigated using chemical analysis of exhaled breath was breast, colon, liver, lung, ovarian, and stomach cancers. Lack of multiple studies using the same breath analysis method(s) precluded meta-analysis. Our review covers the reported methods on breath analysis and assumed exhaled biomarkers. This review makes available to other researchers a catalog of published data on breath analysis for cancer detection. We make recommendations to standardize methods for more accurate breath tests in cancer detection.

Construction and Evaluation of a Versatile ${hbox {CO}}_{2}$ Controlled Breath Collection Device Miekisch, W. Hengstenberg, A. Kischkel, S. Beckmann, U. Mieth, M. Schubert, J. K. Abstract Breath gas analysis offers fascinating new opportunities as it is completely noninvasive and provides a unique window to various biochemical processes in the organism. Requirements for clinical application of this innovative technique include on site and point of care applicability. As most analytical methods like sensors are often not fast enough to realize breath-to-breath sampling additional effort is necessary to provide breath samples of well defined and reproducible composition. For that purpose, we built an automatic ${hbox {CO}}_{2}$ controlled device from

7 standard industrial components that enables adjustable breath sampling in any phase of expiration. Control of sampling was realized by fast responding infrared ${hbox {CO}}_{2}$ sensors. The electrical signal of these sensors was used to trigger a micro pump and a valve. In order to render the device as versatile as possible direct coupling with sensors as well as continuous or discrete sampling via a sample loop or traps was possible. ${hbox {CO}}_{2}$ concentrations, gas flow, and sample volumes were continuously recorded. Reliability and reproducibility of the device were evaluated and compared with an already established and validated manual sampling method. Alveolar concentrations of selected volatile organic compounds (VOCs) were determined in the corresponding samples taken in rest and during treadmill exercise. Substance concentrations of breath biomarkers in the automatically and manually collected alveolar samples were identical. Reliable sampling was possible with the automatic device up to respiratory rates of 40/min. Controlled and versatile alveolar sampling represents an indispensable requirement of application of most analytical methods and sensor technology in breath analysis.

8