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Correspondence |

Exhaled Nitric Oxide Measurements From Different Analyzers FREE TO VIEW

Samatha Sonnappa, MD, PhD; Cristina M. Bastardo, MD; Andrew Bush, MD; Paul Aurora, PhD
Author and Funding Information

From the Portex Unit: Respiratory Medicine and Physiology (Drs Sonnappa, Bastardo, and Aurora), UCL Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust; and the Department of Paediatric Respiratory Medicine (Dr Bush), Royal Brompton Hospital and Imperial College.

Correspondence to: Samatha Sonnappa, MD, PhD, Portex Unit: Respiratory Medicine and Physiology, UCL Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust, 30, Guilford St, London, WC1N 1EH, England; e-mail: s.sonnappa@ich.ucl.ac.uk


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;138(5):1275-1277. doi:10.1378/chest.10-1061
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To the Editor:

Adult studies report differences in the fraction of exhaled nitric oxide (FeNO) measured from different analyzers,1,2 but pediatric data are lacking. FeNO in children and adults measured by a single-breath online technique using NIOX (Aerocrine; Solna, Sweden) and EcoMedics CLD88 (EcoMedics; Duernten, Switzerland) analyzers is reported. Institutional review board approval, patient consent, and parental consent, when appropriate, were obtained.

The analyzers were in adjacent rooms with similar ambience (nitric oxide [NO] <5 ppb) and calibrated according to manufacturers’ instructions. FeNO was measured in subjects who had the ability to maintain an expiratory flow of ~50 mL/s, using the two analyzers within 30 min of each other, in random order. Subjects inhaled NO-free air from a built-in NO filter in the NIOX analyzer and an NO-free air supply (DENOX-88) connected to the EcoMedics analyzer. Pressing a button on the DENOX-88 when inhalation began delivered continuous zero-NO air, which stopped on release of the button when exhalation began. Subjects did not wear nose clips and exhaled within 10% of 50 mL/s for 6 s. Mean FeNO from three measurements within 10% of each other and with valid plateaus was recorded from both analyzers.3 Primary analysis included FeNO from 60 subjects: 30 children, median age (range) 6.6 (4.3-13.6) years, and 30 adults, mean age 34.7 (22.7-51) years. Subanalysis included FeNO from 11 adults while exhaling at ~50 mL/s for 10 s from both analyzers and for 6 s with and without pressing the DENOX-88 button. FeNO values were log-transformed and Bland-Altman plots used to determine limits of agreement (LA) between analyzers.4

All FeNO measurements were higher with NIOX than EcoMedics after 6-s exhalation. With the DENOX-88 button pressed, FeNO in children and adults demonstrated poor agreement between the two analyzers after 6 s (Figs 1A, 1B), but not after 10-s exhalation (Fig 1C). However, when the DENOX-88 button was not pressed, there was good agreement after 6-s exhalation (Fig 1D). Furthermore, the EcoMedics showed lower FeNO values at the preset 2- to 4-s plateau than adjusted 4- to 6-s plateau (mean difference, 16%; 95% LA, 23%, 55%).

Figure Jump LinkFigure 1. Bland-Altman plots showing LA between NIOX and EcoMedics analyzers with different settings. A, 6-s exhalation in children with DENOX-88 button pressed. B, 6-s exhalation in adults with DENOX-88 button pressed. C, 10-s exhalation in adults with DENOX-88 button pressed. D, 6-s exhalation in adults without pressing DENOX-88 button. FeNO = fraction of exhaled nitric oxide; LA = limits of agreement.Grahic Jump Location

FeNO from EcoMedics after 6-s exhalation was significantly lower than FeNO from NIOX. It is likely that residual zero-NO air in the tubing dilutes the FeNO on releasing the DENOX-88 button when exhalation begins, increasing time to stable plateau. Moreover, EcoMedics analyzer is preset to read FeNO at 2- to 4-s plateau for 6-s exhalation, whereas NIOX analyzer is preset to choose the best plateau, which further increases differences.

EcoMedics and NIOX analyzers have built-in NO filters, and if ambient NO is <5 ppb, inhaling continuous zero-NO air is not recommended, particularly in young children in whom the duration of exhalation is shorter. These findings highlight the importance of determining equipment-specific reference ranges and reporting true stable FeNO plateaus.

Müller KC, Jörres RA, Magnussen H, Holz O. Comparison of exhaled nitric oxide analysers. Respir Med. 2005;995:631-637. [CrossRef] [PubMed]
 
Borrill Z, Clough D, Truman N, Morris J, Langley S, Singh D. A comparison of exhaled nitric oxide measurements performed using three different analysers. Respir Med. 2006;1008:1392-1396. [CrossRef] [PubMed]
 
American Thoracic SocietyAmerican Thoracic Society European Respiratory Society European Respiratory Society ATS/ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide, 2005. Am J Respir Crit Care Med. 2005;1718:912-930. [CrossRef] [PubMed]
 
Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;18476:307-310. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1. Bland-Altman plots showing LA between NIOX and EcoMedics analyzers with different settings. A, 6-s exhalation in children with DENOX-88 button pressed. B, 6-s exhalation in adults with DENOX-88 button pressed. C, 10-s exhalation in adults with DENOX-88 button pressed. D, 6-s exhalation in adults without pressing DENOX-88 button. FeNO = fraction of exhaled nitric oxide; LA = limits of agreement.Grahic Jump Location

Tables

References

Müller KC, Jörres RA, Magnussen H, Holz O. Comparison of exhaled nitric oxide analysers. Respir Med. 2005;995:631-637. [CrossRef] [PubMed]
 
Borrill Z, Clough D, Truman N, Morris J, Langley S, Singh D. A comparison of exhaled nitric oxide measurements performed using three different analysers. Respir Med. 2006;1008:1392-1396. [CrossRef] [PubMed]
 
American Thoracic SocietyAmerican Thoracic Society European Respiratory Society European Respiratory Society ATS/ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide, 2005. Am J Respir Crit Care Med. 2005;1718:912-930. [CrossRef] [PubMed]
 
Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;18476:307-310. [CrossRef] [PubMed]
 
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