The authors acknowledge financial support from a National Science Foundation (NSF) grant EEC-0540832 entitled &#8220;Mid-Infrared Technologies for Health and the Environment (MIRTHE)&#8221;

1. Preparation of Instruments
<ol>
	<li>Turn on the external power supply to the ammonia optical sensor platform, laser diode controller, a custom built control electronics unit (CEU), the breath sampler, air pump, and laptop.</li>
	<li>Check that both the exhaust and cooling fans of the ammonia sensor are operating. NOTE: One is located in the rear of the sensor, the second is found within the sensor, which is easily accessible.</li>
	<li>Ensure the acoustic detection module and needle valve temperature are at 38.0 &#...

<ol>
	<li>Adeva, M. M., Souto, G., Blanco, N., Donapetry, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ammonium+metabolism+in+humans.">Ammonium metabolism in humans.</a> Metabolism: clinical and experimental. 61 (11), 1495-1511 (2012).</li><li>Auron, A., Brophy, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperammonemia+in+review:+pathophysiology,+diagnosis,+and+treatment.">Hyperammonemia in review: pathophysiology, diagnosis, and treatment.</a> Pediatric nephrology. 27 (2), 207-222 (2012).</li><li>Blanco Vela, C. I., Bosques Padilla, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+ammonia+concentrations+in+cirrhosis+patients-still+confusing+after+all+these+years.">Determination of ammonia concentrations in cirrhosis patients-still confusing after all these years.</a> Annals of hepatology. 10 Suppl 2, (2011).</li><li>Mpabanzi, L., Ol de Damink, S. W. M., van de Poll, M. C. G., Soeters, P. B., Jalan, R., Dejong, C. H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=To+pee+or+not+to+pee:+ammonia+hypothesis+of+hepatic+encephalopathy+revisited.">To pee or not to pee: ammonia hypothesis of hepatic encephalopathy revisited.</a> European journal of gastroenterology &amp; hepatology. 23 (6), 449-454 (2011).</li><li>Goggs, R., Serrano, S., Szladovits, B., Keir, I., Ong, R., Hughes, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+investigation+of+a+point-of-care+blood+ammonia+analyzer.">Clinical investigation of a point-of-care blood ammonia analyzer.</a> Veterinary clinical pathology / American Society for Veterinary Clinical Pathology. 37 (2), 198-206 (2008).</li><li>Huizenga, J. R., Tangerman, A., Gips, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+ammonia+in+biological+fluids.">Determination of ammonia in biological fluids.</a> Annals of clinical biochemistry. 31 (Pt 6), 529-543 (1994).</li><li>Lewicki, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real+time+ammonia+detection+in+exhaled+human+breath+with+a+quantum+cascade+laser+based+sensor.">Real time ammonia detection in exhaled human breath with a quantum cascade laser based sensor.</a> 2009 Conference on Lasers and ElectroOptics and 2009 Conference on Quantum electronics and Laser Science Conference. 1, (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=American+Thoracic+Society.+European+Respiratory+Society.+Recommendations+for+Standardized+Procedures+for+the+Online+and+Offline+Measurement+of+Exhaled+Lower+Respiratory+Nitric+Oxide+and+Nasal+Nitric+Oxide.">American Thoracic Society. European Respiratory Society. Recommendations for Standardized Procedures for the Online and Offline Measurement of Exhaled Lower Respiratory Nitric Oxide and Nasal Nitric Oxide.</a> American journal of respiratory and critical care medicine. 171 (8), 912-930 (2005).</li><li>Solga, S. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+influencing+breath+ammonia+determination.">Factors influencing breath ammonia determination.</a> Journal of breath research. 7 (3), (2013).</li><li>Schmidt, F. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ammonia+in+breath+and+emitted+from+skin.">Ammonia in breath and emitted from skin.</a> Journal of breath research. 7 (1), (2013).</li><li>Span&#283;l, P., Dryahina, K., Smith, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+study+of+the+influence+of+inhaled+compounds+on+their+concentrations+in+exhaled+breath.">A quantitative study of the influence of inhaled compounds on their concentrations in exhaled breath.</a> Journal of breath research. 7 (1), (2013).</li><li>Boots, A. W., van Berkel, J. J. B. N., Dallinga, J. W., Smolinska, A., Wouters, E. F., van Schooten, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+versatile+use+of+exhaled+volatile+organic+compounds+in+human+health+and+disease.">The versatile use of exhaled volatile organic compounds in human health and disease.</a> Journal of breath research. 6 (2), (2012).</li><li>Hibbard, T., Killard, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Breath+ammonia+levels+in+a+normal+human+population+study+as+determined+by+photoacoustic+laser+spectroscopy.">Breath ammonia levels in a normal human population study as determined by photoacoustic laser spectroscopy.</a> Journal of breath research. 5 (3), (2011).</li><li>Wang, T., Pysanenko, A., Dryahina, K., Span&#283;l, P., Smith, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+breath,+exhaled+via+the+mouth+and+nose,+and+the+air+in+the+oral+cavity.">Analysis of breath, exhaled via the mouth and nose, and the air in the oral cavity.</a> Journal of breath research. 2 (3), (2008).</li><li>Amann, A., Smith, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Volatile Biomarkers. 1st Edition. , (2013).</li></ol>

The benefits of a non-invasive procedure capable of detecting trace metabolites in real time are obvious. However, the field of breath research has struggled to fulfill this potential. Breath measurement is a dynamic process vulnerable to many confounding factors. Our approach has important strengths: specifically, the sensitivity and speed of the Rice QEPAS based ammonia monitor coupled to the breath sampler have enabled us to evaluate and identify breath collection factors germane to accurate measurement. This approach...

Ammonia is a ubiquitous byproduct of protein metabolism1. Ammonia measurement can therefore help clinicians assess various disease and wellness states2. However, ammonia is difficult to measure accurately, via blood or breath, because it is very reactive. Though commonly used, blood assays have numerous drawbacks, including basic concerns about accuracy3. But the major problem with blood assays is the reality that they only ever collected episodically. This is important because ammonia physiology, much like blood glucose and many other metabolic processes, are fluid and ever changing4. In contrast, breath assays are fully non-invasive and quick, thereby easily enabling repeated measures. Thus, breath ammonia measurement is attractive because it may address a serious unmet need in a unique way.
Breath collection, however, presents unique concerns. Whereas phlebotomy inherently carries the jeopardy of error in several unpredictable ways (e.g., tourniquet time, sweat contamination, blood cell hemolysis, delay in laboratory measurement, etc5), breath measurement researchers must contend with a different group of novel challenges: variability in breathing, contamination with oral mucosal or bacterial ammonia, influence of ambient air and apparatus humidity and temperature, etc6. Indeed, it is unwise to underestimate the task in connecting experimental equipment to humans using experimental procedures to discover unknown biology. In part due to these obstacles, breath ammonia has not yet met its potential.
Herein, we present our breath ammonia measurement protocol for fast and accurate results. Our protocol has strength in three areas: the monitor, the interface sampler, and attention to the human influences. The monitor was built by colleagues at Rice University as previously described7. The basis of the measurement is a quartz enhanced photoacoustic spectroscopy (QEPAS) technique that employs a piezoelectric quartz tuning fork as an acoustic transducer. Photoacoustic effect occurs when acoustic waves are produced by the absorption of modulated laser radiation by target trace gas species. The trace gas is detected using an acoustic cell that is acoustically resonant to the modulated frequency. An absorption wavelength for ammonia was selected that is free from spectral interferences from interfering species in breath. For the purposes of human exhaled breath measurement, the main features of the monitor include a wide measurement range (from ~50 parts per billion, ppb to at least 5,000 ppb) and speed (1&#160;sec&#160;measurements). The speed of the monitor enables time resolution throughout the breath cycle.
The monitor is coupled to a specially designed breath sampler. The sampler consists of a pressure sensor and capnograph. It displays and archives real time measurements of mouth pressure and carbon dioxide as well as the ammonia concentrations determined by the sensor. This sampler, therefore, enables the technician to evaluate the quality of the breath effort as the breath is collected. This enables us to exceed the recommendations for analyzing breath nitric oxide (FeNO) proposed by Task Force of the American Thoracic Society/European Respiratory Society (ATS/ERS)8. For all breath sampling, a disposable one-way in-line valve was used on the mouth port of the breath sampler.
Because of the speed of the monitor and the quality controls provided by the sampler, we were able to carefully evaluate human influences9. Most subjects, for example, initially hyperventilate when instructed to breathe. Other important influences, such as oral pH and mouth rinses, temperatures of the sampler, monitor and all associated tubing, and mode of breathing, were then studied, and are the basis for the illustrative experiments below.
Finally, and perhaps most significantly, it must be emphasized that multiple highly experienced groups are measuring breath ammonia using entirely different sensors and measurement procedures. These may have important advantages and validity. A complete comparison is beyond the scope of the present work10,11,12.

<table border="0" cellpadding="0" cellspacing="0" width="666">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Rice Ammonia Monitor System</td>
			<td style="width:171px;">N/A</td>
			<td style="width:119px;">N/A</td>
			<td style="width:167px;">Not available for commercial purchase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Loccioni Breath Sampler</td>
			<td style="width:171px;">Loccioni Humancare</td>
			<td style="width:119px;">N/A</td>
			<td>Single breath version</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Disposable Mouth Piece</td>
			<td style="width:171px;">WestPrime Healthcare</td>
			<td style="width:119px;">G011-200</td>
			<td>Manufacturer is AlcoQuant</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Laptop</td>
			<td style="width:171px;">Lenovo</td>
			<td style="width:119px;">N/A</td>
			<td>Old model no longer sold by manufacturer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Acid Rinse</td>
			<td style="width:171px;">N/A</td>
			<td style="width:119px;">N/A</td>
			<td>Household acidic drink (coffee, soft drink, citrus juices, etc)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Base Rinse</td>
			<td style="width:171px;">N/A</td>
			<td style="width:119px;">N/A</td>
			<td>Water mixed with a nonexact amount of sodium bicarbonate (Arm &#38; Hammer Baking Soda)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Neutral Rinse</td>
			<td style="width:171px;">N/A</td>
			<td style="width:119px;">N/A</td>
			<td>Water</td>
		</tr>
	</tbody>
</table>

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 uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels. 
Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive. 
The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations.

Subjects can be expected to produce a wide range of baseline breath ammonia levels. Healthy individuals may begin the day with a breath ammonia measurement of 100-1,000 ppb. Rinsing the mouth out with any fluid immediately changes the amount of detectable breath ammonia. Neutral and acidic fluids typically cut the amount of observable ammonia by more than half. These levels then return to baseline as the effects of the rinse wears off. The effects of water seem to dissipate within 15 min, while an acid can keep detectabl...

Watch this Scientific Journal Video about Fast and Accurate Exhaled Breath Ammonia Measurement at JoVE.com

Fast and Accurate Exhaled Breath Ammonia Measurement

Ammonia is an important physiologic metabolite relevant to various disease and wellness states. It is also a difficult molecule to measure in breath, which demands particular precautions be taken to obtain accurate results. Not all factors influencing ammonia are known, but progress can be difficult without accounting for these factors.

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

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13.1K 조회수.  St. Luke's University Hospital. Ammonia is an important physiologic metabolite relevant to various disease and wellness states. It is also a difficult molecule to measure in breath, which demands particular precautions be taken to obtain accurate results. Not all factors influencing ammonia are known, but progress can be difficult without accounting for these factors.