fast-and-accurate-exhaled-breath-ammonia-measurement

Fast and Accurate Exhaled Breath Ammonia Measurement

This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that ...

Chronic liver disease is initially occult, has multiple aetiologies, involves complex diagnostic questions, and requires follow-up because progression is likely. Blood tests and biopsies are generally used, but have disadvantages. We have developed a new test for liver disease based on abnormal concentrations of metabolic products detected in exhaled breath. This test can be used, in conjunction with other clinically accepted diagnostic protocols, to detect and classify chronic liver diseases. Samples of breath collected from spontaneously breathing human subjects (86 patients presenting with 13 liver diseases and 109 subjects with normal liver function) were concentrated cryogenically and analysed by wide-bore capillary gas chromatography using various detectors. The concentrations of various molecules in exhaled breath were examined for potential use as biomarkers of liver function. Subjects with chronic liver diseases could be differentiated from those with normal liver function by comparing levels of breath carbonyl sulphide, carbon disulphide and isoprene; these differences were confirmed and correlated by comparing the levels with standard clinical blood markers of liver damage. The presence of chronic liver failure can thus be detected with sensitivity and specificity by quantifying sulphur-containing compounds arising from the abnormal metabolism associated with liver disease. The breath test we have developed appears to distinguish between hepatocellular and biliary tract aetiologies, and allows staging for severity. This approach may provide the clinician with a simple, non-invasive technique for use in the screening of large populations and follow-up for patients with chronic liver disease.

Breath biomarkers for detection of human liver diseases: preliminary study.

Nurses working in the PACU are occupationally exposed to volatile anesthetics that are exhaled by patients. Few studies have quantified this exposure using breath analysis or have characterized biological effects associated with this exposure. Isoflurane is a widely used anesthetic and is a strong respiratory depressant. Exposure to isoflurane has been shown to cause changes in breathing patterns at low doses. However, biological effects of isoflurane exposure have never been addressed in the occupational setting. This study investigates whether occupational exposure to anesthetic gases has a depressive effect on central neural control of breathing. In this study, concentrations of halogenated anesthetics were quantified in pre- and postshift breath samples of nurses working in the PACU on a Friday and the following Monday. After each breath sample was collected, an occlusion pressure measurement was taken as an indicator of central inspiratory drive. Cumulative nitrous oxide and halogenated anesthetics exposure was measured each day using personal sampling monitors placed close to the nurse's mouth. Exposure to nitrous oxide and isoflurane was significantly higher on Monday than on Friday (P <.001). Monday breath isoflurane concentrations (mean +/- SD) increased significantly from 43 +/- 30 parts per billion (ppb) in preshift breath samples to 124 +/- 57 ppb in postshift breath samples (P <.002). On Monday, there was a significant decrease in occlusion pressure from 1.2 +/- 0.37 cm H(2)O in preshift samples to 0.85 +/- 0.43 cm H(2)O in postshift samples (P =.05). There was no statistical difference in pre- versus postbreath isoflurane or occlusion pressure on Friday. These data indicate that after increased exposure to isoflurane, central neurorespiratory activity was depressed.

Phase II collaborative pilot study: preliminary analysis of central neural effects from exposure to volatile anesthetics in the PACU.

Respirable particulate matter generated during incomplete combustion of fossil fuels may principally target the cells found in the distal region of the lung. This study characterizes some of the effects that a model particulate matter has on the induction of heme oxygenase (HO)-1 in macrophages. HO-1 is a highly inducible stress response gene that has been demonstrated to modulate chemical, physical, and environmental stimuli. Cultured macrophages (RAW 264.7 cells) exposed continuously to a well-defined model of particulate matter (benzo[a]pyrene adsorbed onto carbon black) induced HO-1 gene expression in a time-dependent manner. Likewise, the addition of benzo[a]pyrene-1,6-quinone, a redox cycling metabolite of benzo[a]pyrene, to RAW cells also induced HO-1. This particle-induced gene expression of HO-1 was found to correlate with a corresponding increase in protein levels. Gene regulation studies were performed to delineate the transcriptional regulation of HO-1 after exposure to model particulate matter. Deletional analysis of the HO-1 gene and mutational analysis of activator protein (AP)-1 regulatory element on both distal enhancers demonstrated the importance of this transcriptional factor in mediating HO-1 gene transcription in response to model particulate matter. These results were supported by gel shift analysis demonstrating increased AP-1 binding activity after exposure to particulate matter. In summary, this study demonstrates that model particulate matter enhanced the expression of HO-1. This inductive process may be mediated by AP-1 activation of the regulatory elements on both the 5'-distal enhancers.

Transcriptional regulation of the HO-1 gene in cultured macrophages exposed to model airborne particulate matter.

Transkriptionellen Regulation des HO-1-Gens in kultivierten Makrophagen ausgesetzt Modell Feinstaub.

Further discussion on breath condensate analysis.

A computerized system has been developed to monitor tidal volume, respiration rate, mouth pressure, and carbon dioxide during breath collection. This system was used to investigate variability in the production of breath biomarkers over an 8-h period. Hyperventilation occurred when breath was collected from spontaneously breathing study subjects (n = 8). Therefore, breath samples were collected from study subjects whose breathing were paced at a respiration rate of 10 breaths/min and whose tidal volumes were gauged according to body mass. In this "paced breathing" group (n = 16), end-tidal concentrations of isoprene and ethane correlated with end-tidal carbon dioxide levels [Spearman's rank correlation test (r(s)) = 0.64, P = 0.008 and r(s) = 0.50, P = 0.05, respectively]. Ethane also correlated with heart rate (r(s) = 0.52, P < 0.05). There was an inverse correlation between transcutaneous pulse oximetry and exhaled carbon monoxide (r(s) = -0.64, P = 0.008). Significant differences were identified between men (n = 8) and women (n = 8) in the concentrations of carbon monoxide (4 parts per million in men vs. 3 parts per million in women; P = 0.01) and volatile sulfur-containing compounds (134 parts per billion in men vs. 95 parts per billion in women; P = 0.016). There was a peak in ethanol concentration directly after food consumption and a significant decrease in ethanol concentration 2 h later (P = 0.01; n = 16). Sulfur-containing molecules increased linearly throughout the study period (beta = 7.4, P < 0.003). Ventilation patterns strongly influence quantification of volatile analytes in exhaled breath and thus, accordingly, the breathing pattern should be controlled to ensure representative analyses.

Effects of ventilation on the collection of exhaled breath in humans.

This study investigates anecdotal reports that have suggested adverse health effects associated with acute or chronic exposure to jet fuel.

Human exposure to the jet fuel, JP-8.

Cavity-enhanced tunable diode laser absorption spectroscopy is an attractive method for measuring small concentrations of gaseous species. Ethane is a breath biomarker of lipid peroxidation initiated by reactive oxygen species. A noninvasive means of quickly quantifying oxidative stress status has the potential for broad clinical application. We present a simple, compact system using off-axis integrated cavity output spectroscopy with an interband cascade laser and demonstrate its use in real-time measurements of breath ethane. We demonstrate a detection sensitivity of 0.48 ppb/Hz(1/2).

Off-axis integrated cavity output spectroscopy with a mid-infrared interband cascade laser for real-time breath ethane measurements.

Reactive oxygen species are associated with tissue inflammation and injury. Our laboratory has demonstrated that ethane, a stable product of lipid peroxidation, in exhaled breath can be used to measure total body oxidative stress. Herein patients were studied who underwent outpatient surgery, laproscopic bilateral tubal ligation (BTL, n = 10) and anterior cruciate ligament (ACL, n = 10) repair of the knee. These surgical procedures were expected to involve mild degrees of ischemia and reperfusion. In each of these cases propofol, an intravenous anesthetic with antioxidant properties, was used. Breath ethane was measured as a biomarker of oxidative stress that occurred at reperfusion of ischemic tissue. Data were analyzed by one-way analysis of variance. Clinically relevant concentrations of propofol were unable to completely block the increase in oxidative stress following reperfusion in either of these minor surgeries. Breath ethane increased significantly after reperfusion in both the BTL (p = 0.03) and the ACL (p = 0.005) patients. Also, the increase in oxidative stress was related to the time of ischemia.

Changes in oxidative stress during outpatient surgery.

Reactive oxygen species are associated with tissue inflammation and injury. Our laboratory has demonstrated that ethane, a stable product of lipid peroxidation, in exhaled breath can be used to measure total body oxidative stress. An ischemia-reperfusion model of lung injury in sheep has been studied in which pulmonary and bronchial lung perfusion could be interrupted and restored. The goal of this study was to investigate whether two commercial formulations of propofol and the individual components of the commercial formulations attenuated the oxidative stress produced in this model. Breath ethane and breath carbon monoxide were measured as biomarkers of oxidative stress that occur at reperfusion of ischemic tissue. Data were analyzed by a standard least-squares-fit model. One of the formulations for propofol, which contained the preservative ethylenediaminetetraacetic acid (EDTA), was found to decrease the overall level of oxidative stress in sheep. Furthermore, while several models of severe lung injury demonstrate additional production of reactive oxygen species, our model of ischemia/reperfusion of lung tissue did not.

Propofol and in vivo oxidative stress: effects of preservative.

Reaktive Sauerstoffspezies sind mit Gewebe Entz&uuml;ndungen und Verletzungen. Unser Labor hat gezeigt, dass Ethan, ein stabiles Produkt der Lipidperoxidation in ausgeatmete Atem kann verwendet werden, total K&ouml;rper oxidativen Stress zu messen. Ein Isch&auml;mie-Reperfusion-Modell der Respiratory Distress Syndrome bei Schafen ist studiert worden, in der Lunge und Bronchien Lunge Perfusion unterbrochen und wiederhergestellt werden konnte. Ziel dieser Studie war es zu untersuchen, ob zwei kommerzielle Formulierungen von Propofol und die einzelnen Komponenten der kommerziellen Formulierungen den oxidativen Stress in diesem Modell produziert abgeschw&auml;cht. Atem Ethan und Atem Kohlenmonoxid wurden als Biomarker f&uuml;r oxidativen Stress gemessen, die zur Reperfusion der isch&auml;mischen Gewebe auftreten. Daten wurden durch ein Standardmodell am wenigsten-Quadrate-Fit analysiert. Eine der Formulierungen f&uuml;r Propofol, die die S&auml;ure Konservierungsmittel Ethylendiamintetraessigs&auml;ure (EDTA) enthalten, wurde gefunden, um das Gesamtniveau der oxidativen Stress bei Schafen zu verringern. Dar&uuml;ber hinaus w&auml;hrend mehrere Modelle des schweren Lungeninsuffizienz zus&auml;tzliche Produktion von reaktiven Sauerstoffspezies demonstrieren, nicht unser Modell der Isch&auml;mie/Reperfusion von Lungengewebe.

Propofol und in-vivo oxidativer Stress: Auswirkungen der Konservierungsmittel.

Breath analysis--past, present and future: a special issue in honour of Michael Phillips' 70th birthday.

Volatile organic compounds (VOCs) in exhaled breath originate from current or previous environmental exposures (exogenous compounds) and internal metabolic (anabolic and catabolic) production (endogenous compounds). The origins of certain VOCs in breath presumed to be endogenous have been proposed to be useful as preclinical biomarkers of various undiagnosed diseases including lung cancer, breast cancer, and cardio-pulmonary disease. The usual approach is to develop difference algorithms comparing VOC profiles from nominally healthy controls to cohorts of patients presenting with a documented disease, and then to apply the resulting rules to breath profiles of subjects with unknown disease status. This approach to diagnosis has a progression of sophistication; at the most rudimentary level, all measurable VOCs are included in the model. The next level corrects exhaled VOC concentrations for current inspired air concentrations. At the highest level, VOCs exhibiting discriminatory value also require a plausible biochemical pathway for their production before inclusion. Although these approaches have all shown some level of success, there is concern that pattern recognition is prone to error from environmental contamination and between-subject variance. In this paper, we explore the underlying assumptions for the interpretation and assignment of endogenous compounds with probative value for assessing changes. Specifically, we investigate the influence of previous exposures, elimination mechanisms and partitioning of exogenous compounds as confounders of true endogenous compounds. We provide specific examples based on a simple classical pharmacokinetic approach to identify potential misinterpretations of breath data and propose some remedies.

Clinical breath analysis: discriminating between human endogenous compounds and exogenous (environmental) chemical confounders.

This report proposes a potentially sensitive and simple physiological method to detect early changes and to follow disease progression in obstructive pulmonary disease (COPD) based upon the usual pulmonary function test. Pulmonary function testing is a simple, although relatively insensitive, method to detect and follow COPD. As a proof-of-concept, we have examined the slope of the plateau for carbon dioxide during forced expiratory capnography in healthy (n = 10) and COPD subjects (n = 10). We compared the change in the rate of exhalation of carbon dioxide over time as a marker of heterogeneous ventilation of the lung. All subjects underwent pulmonary function testing, body-plethysmography, and forced exhalation capnography. The subjects with COPD also underwent high-resolution computed tomography of the chest. Regression lines were fitted to the slopes of the forced exhalation capnogram curves. There was no difference in the mean levels of exhaled carbon dioxide between the COPD and the healthy groups (p > 0.48). We found a significant difference in the mean slope of the forced exhalation capnogram for the COPD subjects compared to the healthy subjects (p = 0.01). Most important, for the COPD subjects, there was a significant positive correlation between the slope of the forced exhaled capnogram and a defined radiodensity measurement of the lung by high-resolution computed tomography (r(2) = 0.49, p = 0.02). The slope of the forced exhalation capnogram may be a simple way to determine physiological changes in the lungs in patients with COPD that are not obtainable with standard pulmonary function tests. Forced exhalation capnography would be of great clinical benefit if it can identify early disease changes and at-risk individuals.

Forced expiratory capnography and chronic obstructive pulmonary disease (COPD).

Amongst volatile compounds (VCs) present in exhaled breath, ammonia has held great promise and yet it has confounded researchers due to its inherent reactivity. Herein we have evaluated various factors in both breath instrumentation and the breath collection process in an effort to reduce variability. We found that the temperature of breath sampler and breath sensor, mouth rinse pH, and mode of breathing to be important factors. The influence of the rinses is heavily dependent upon the pH of the rinse. The basic rinse (pH 8.0) caused a mean increase of the ammonia concentration by 410 ± 221 ppb. The neutral rinse (pH 7.0), slightly acidic rinse (pH 5.8), and acidic rinse (pH 2.5) caused a mean decrease of the ammonia concentration by 498 ± 355 ppb, 527 ± 198 ppb, and 596 ± 385 ppb, respectively. Mode of breathing (mouth-open versus mouth-closed) demonstrated itself to have a large impact on the rate of recovery of breath ammonia after a water rinse. Within 30 min, breath ammonia returned to 98 ± 16% that of the baseline with mouth open breathing, while mouth closed breathing allowed breath ammonia to return to 53 ± 14% of baseline. These results contribute to a growing body of literature that will improve reproducibly in ammonia and other VCs.

Article	Year
Breath biomarkers for detection of human liver diseases: preliminary study. Biomarkers : biochemical indicators of exposure, response, and susceptibility to chemicals\| PubMed ID: 12101636	2002
Phase II collaborative pilot study: preliminary analysis of central neural effects from exposure to volatile anesthetics in the PACU. Journal of perianesthesia nursing : official journal of the American Society of PeriAnesthesia Nurses / American Society of PeriAnesthesia Nurses\| PubMed ID: 12173155	2002
Transcriptional regulation of the HO-1 gene in cultured macrophages exposed to model airborne particulate matter. American journal of physiology. Lung cellular and molecular physiology\| PubMed ID: 12456389	2003
Further discussion on breath condensate analysis. American journal of respiratory and critical care medicine\| PubMed ID: 12738595	2003
Effects of ventilation on the collection of exhaled breath in humans. Journal of applied physiology (Bethesda, Md. : 1985)\| PubMed ID: 14672964	2004
Human exposure to the jet fuel, JP-8. Aviation, space, and environmental medicine\| PubMed ID: 14736133	2004
Off-axis integrated cavity output spectroscopy with a mid-infrared interband cascade laser for real-time breath ethane measurements. Applied optics\| PubMed ID: 19183584	2009
Changes in oxidative stress during outpatient surgery. Journal of breath research\| PubMed ID: 21383450	2009
Propofol and in vivo oxidative stress: effects of preservative. Journal of breath research\| PubMed ID: 21383451	2009
Breath analysis--past, present and future: a special issue in honour of Michael Phillips' 70th birthday. Journal of breath research\| PubMed ID: 23445558	2013
Clinical breath analysis: discriminating between human endogenous compounds and exogenous (environmental) chemical confounders. Journal of breath research\| PubMed ID: 23445880	2013
Forced expiratory capnography and chronic obstructive pulmonary disease (COPD). Journal of breath research\| PubMed ID: 23445906	2013
Factors influencing breath ammonia determination. Journal of breath research\| PubMed ID: 23774041	2013

Terence H. Risby

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