Methods of NO detection in exhaled breath

Abstract

There is still an unexplored potential for exhaled nitric oxide (NO) in many clinical applications. This study presents an overview of the currently available methods for monitoring NO in exhaled breath and the use of the modelling of NO production and transport in the lung in clinical practice. Three technologies are described, namely chemiluminescence, electrochemical sensing and laser-based detection with their advantages and limitations. Comparisons are made in terms of sensitivity, time response, size, costs and suitability for clinical purposes. The importance of the flow rate for NO sampling is discussed from the perspective of the recent recommendations for standardized procedures for online and offline NO measurement. The measurement of NO at one flow rate, such as 50 ml s(-1), can neither determine the alveolar site/peripheral contribution nor quantify the difference in NO diffusion from the airways walls. The use of NO modelling (linear or non-linear approach) can solve this problem and provide useful information about the source of NO. This is of great value in diagnostic procedures of respiratory diseases and in treatment with anti-inflammatory drugs.

Exhaled NO: Determinants and Clinical Application in Children With Allergic Airway Disease

“…Chemiluminescence analyzers determine NO concentrations by measuring the light generated by a chemical reaction of NO with ozone. 4 This technique has high sensitivity, and NO can be accurately measured in the parts per billion (ppb) range. 5 Several FeNO analyzers have been commercially available, such as NIOX (Aerocrine, Stockholm, Sweden), NOA 280i (Sievers, GE Analytical Instruments, Boulder, CO, USA), and CLD 88 (Eco Medics, Duernten, Switzerland).…”

“…Fast flow rates reduce the contribution from airway wall diffusion, resulting in lower FeNO levels, while slow rates increase FeNO. 4 According to the ATS/ERS recommendation, the standard expiratory flow rate for FeNO measurement is 50 mL/s. 5 Subjects should sit in an upright position, exhale to residual volume, insert a mouth piece, inhale to total lung capacity−preferably using NO free air−and then exhale immediately against a standard backpressure to close the velum for 10 seconds at a constant flow rate of 50 mL/s.…”

Laser spectroscopy for breath analysis: towards clinical implementation

“…This article is part of the topical collection "Mid-infrared and THz Laser Sources and Applications" guest edited by Wei Ren, Paolo De Natale and Gerard Wysocki. from normal body metabolism [1][2][3][4]. Human breath also contains exogenous compounds that originate from food and beverages or from current or previous environmental exposures [5].…”

Measurement of Exhaled Nitric Oxide Using End Tidal Value during Normal Breathing

“…Furthermore, the guidelines have justifiably influenced the industry and some companies have manufactured NO analyzers narrowly based on the guidelines, potentially hindering the development of better methods for NO measurement. While some clinicians remain skeptical about using NO measurement [16][17][18][19], others believe the measurement is very useful and helps with the management of asthma [6,[20][21][22]. More importantly, the changes in NO concentration in exhaled air in lung diseases can be small and subtle and can be easily overshadowed by methodological errors, such variations as in flow rate or patient's cooperation.…”