Comparison of exhaled nitric oxide analysers

The need for multicomponent gas standards for breath biomarker analysis

Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monitor disease, including infectious disease. Despite significant effort dedicated to biomarker identification in case control studies, very few breath tests are established in practice. In this topical review, we identify how gas standards support breath analysis today and what is needed to support further expansion and translation to practice. We examine forensic and clinical breath tests and discuss how confidence has been built through unambiguous biomarker identification and quantitation supported by gas calibration standards. Based on this discussion, we identify a need for multicomponent gas standards with part-per-trillion to part-per-million concentrations. We highlight National Institute of Standards and Technology (NIST) gas standards developed for atmospheric measurements that are also relevant to breath analysis and describe investigations of long-term stability, chemical reactions, and interactions with gas cylinder wall treatments. An overview of emerging online instruments and their need for gas standards is also presented. This review concludes with a discussion of our ongoing research to examine the feasibility of producing multicomponent gas standards at breath-relevant concentrations. Such standards could be used to investigate interference from ubiquitous endogenous compounds and as a starting point for standards tailored to specific breath tests.

Clinical precision, accuracy, number and durations of exhalations for a novel electrochemical monitor for exhaled nitric oxide

BACKGROUND

Exhaled nitric oxide (FeNO) is a validated marker of eosinophilic inflammation. Fenom Pro^TM is a novel FDA-cleared monitor for FeNO. The American Thoracic Guidelines from 2005 recommend at least 6 s exhalation for adults and in some cases up to 10 s, and 4 s for children, and that the average of the first two valid exhalations is taken as the FeNO value.

METHODS

Clinical precision, 6 versus 10 s exhalations, the first versus the average of the first two valid exhalation methods comparison were evaluated for Fenom Pro^TM, as well as a methods comparison to the NIOX VERO^® monitor.

RESULTS

The intent-to-treat population (n = 126) consisted of 83 adults, and 43 pediatric subjects with 16 subjects under 12 years of age. Clinical precision for 10 s exhalations on Fenom Pro^TM was excellent with a within-subject standard deviation (SD) range of 0.57-3.73 ppb and mean coefficient of variation (CV) range of 4.21% to 9.65%. The clinical precision for the separate adult and pediatric groups as well as for the 6 s exhalations were similar. The 10 and 6 s exhalation comparisons and one versus the average of two valid exhalations showed a high level of agreement. The Fenom Pro^TM and the NIOX VERO^® monitors also demonstrated a high level of agreement with the values from the latter slightly lower (mean bias of -3.2 ppb).

CONCLUSION

Fenom Pro^TM demonstrated eminently acceptable performance supporting its clinical utility. The data suggests that 6 s exhalations can be used in adults and children, and that one exhalation is adequate rather than obtaining the average of two exhalations on Fenom Pro^TM.

Measurement of Fractional Exhaled Nitric Oxide: Comparison of Three Different Analysers

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a surrogate marker for airway inflammation, supporting the diagnostic pathway and treatment decisions for asthma patients.

OBJECTIVES

Aim of this study was to compare the new analyser Vivatmo pro (Bosch, BV) with NIOX VERO (Circassia, CN) and CLD (Ecomedics, EC).

METHODS

In 100 asthmatics (median 53 years [range 20-87], 62% female, 86% on inhaled corticosteroids [mean 1,300 μg beclomethasone dipropionate or equivalent], 35% treated with biologics) 2 FeNO measurements per device were performed. Additionally, the success rate to achieve a valid NO value was evaluated.

RESULTS

Sixty-eight percent of the patients had FeNO values below 50 ppb. Median NO concentrations were 31 ppb (range 6-194) for BV, 33 ppb (9-164) for CN and 31ppb (7-353) for EC. Bland-Altman plots suggested an agreement within the predefined limits of ±5 ppb for all analysers within the therapeutically relevant range (0-70 ppb). The highest agreement in FeNO levels were between BV and EC with mean differences of -0.26 (95% CI -1.48 to 0.95) vs. 1.52 (95% CI 0.4-2.6) ppb for CN and EC. The results indicate an equivalence of the methods (two-one sided t test-equivalence test: p < 0.0001, ±5 ppb margins). Acceptance of the measurements was high for all devices (97%). The highest success rate to obtain 2 valid NO values without failed attempts was achieved with the BV analyser (73 vs. 62% for the CN analyser and 46% for the EC analyser).

CONCLUSIONS

For the range between 0 and 70 ppb, FeNO concentrations measured with all 3 devices were statistically equivalent within predefined acceptance criteria and did not differ in a clinically relevant way.

Difference between two exhaled nitric oxide analyzers, NIOX VERO® electrochemical hand-held analyzer and NOA280i® chemiluminescence stationary analyzer

BACKGROUND

Fractional exhaled nitric oxide (FE_NO) is useful for the evaluation of eosinophilic airway inflammation, including that seen in asthma. Although a new electrochemical hand-held FE_NO analyzer, the NIOX VERO^® (Aerocrine AB, Solna, Sweden), is clinically convenient to use, it has not been fully compared with the chemiluminescence stationary electrochemical analyzer NOA280i^® (Sievers Instruments, Boulder, CO, USA) in terms of the level of measured FE_NO. The aim of this study was to determine whether there is a difference between the two analyzers.

METHODS

The FE_NO levels measured with both NIOX VERO^® and NOA280i^® were evaluated in 1,369 adults at Juntendo University Hospital from May 2016 to October 2016.

RESULTS

The median FE_NO level measured with the NIOX VERO^® was significantly lower than that measured with the NOA280i^® (41 ppb, range 5-368 ppb vs. 29 ppb, range 5-251 ppb; p < 0.001). There was a strong positive correlation in the measurement of FE_NO level between the NOA280i^® and the NIOX VERO^® (r = 0.942, p < 0.001). The following conversion equation was calculated: FE_NO (NOA280i^®) = 1.362 (SE, 0.661) + 1.384 (SE, 0.021) × FE_NO (NIOX VERO^®).

CONCLUSIONS

To our best knowledge, we have provided the first report showing that the measured FE_NO level with the NIOX VERO^® was approximately 30% lower than that with the NOA280i^® and that there was a significant correlation between the measurements of these two devices. The correction equation that we provided may help assess the data obtained by these two analyzers. Abbreviations ATS American Thoracic Society BMI Body mass index ERS European Respiratory Society FE_NO Fractional exhaled nitric oxide GINA Global Initiative for Asthma NO Nitric oxide ppb Parts per billion ROC Receiver operating characteristic SD Standard deviation.

Exhaled nitric oxide levels to guide treatment for children with asthma

BACKGROUND

Asthma guidelines aim to guide health practitioners to optimise treatment for patients to minimise symptoms, improve or maintain good lung function, and prevent acute exacerbations. The principle of asthma guidelines is based on a step-up or step-down regimen of asthma medications to maximise health using minimum doses. Fractional exhaled nitric oxide (FeNO) is a marker of eosinophilic inflammation and tailoring asthma medications in accordance to airway eosinophilic levels may improve asthma outcomes such as indices of control or reduce exacerbations, or both.

OBJECTIVES

To evaluate the efficacy of tailoring asthma interventions based on fractional exhaled nitric oxide (FeNO), in comparison to not using FeNO, that is, management based on clinical symptoms (with or without spirometry/peak flow) or asthma guidelines (or both), for asthma-related outcomes in children.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of Trials, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase and reference lists of articles. The last searches were in June 2016.

SELECTION CRITERIA

All randomised controlled trials (RCTs) comparing adjustment of asthma medications based on FeNO levels compared to those not using FeNO, that is, management based on clinical symptoms or asthma guidelines (or both) involving children.

DATA COLLECTION AND ANALYSIS

We reviewed results of searches against predetermined criteria for inclusion. Two review authors independently selected relevant studies, assessed trial quality and extracted data. We contacted study authors for further information with responses provided from three.

MAIN RESULTS

The review included nine studies; these studies differed in a variety of ways including definition of asthma exacerbations, FeNO cut-off levels used (12 parts per billion (ppb) to 30 ppb), the way in which FeNO was used to adjust therapy and duration of study (6 to 12 months). Of 1426 children randomised, 1329 completed the studies. The inclusion criteria for the participants in each study varied but all had a diagnosis of asthma. There was a significant difference in the number of children having one or more asthma exacerbations over the study period, they were significantly lower in the FeNO group in comparison to the control group (odds ratio (OR) 0.58, 95% confidence interval (CI) 0.45 to 0.75; 1279 participants; 8 studies). The number needed to treat for an additional beneficial outcome (NNTB) over 52 weeks was 9 (95% CI 6 to 15). There was no difference between the groups when comparing exacerbation rates (mean difference (MD) -0.37, 95% CI -0.8 to 0.06; 736 participants; 4 studies; I² = 67%). The number of children in the FeNO group requiring oral corticosteroid courses was lower in comparison to the children in the control group (OR 0.63, 95% CI 0.48 to 0.83; 1169 participants; 7 studies; I² = 0%). There was no statistically significant difference between the groups for exacerbations requiring hospitalisation (OR 0.75, 95% CI 0.41 to 1.36; 1110 participants; 6 studies; I² = 0%). There were no significant differences between the groups for any of the secondary outcomes (forced expiratory volume in one second (FEV₁), FeNO levels, symptom scores or inhaled corticosteroid doses at final visit). The included studies recorded no adverse events.Three studies had inadequate blinding and were thus considered to have a high risk of bias. However, when these studies were removed in subgroup analysis, the difference between the groups for the primary outcome (exacerbations) remained statistically significant. The GRADE quality of the evidence ranged from moderate (for the outcome 'Number of participants who had one or more exacerbations over the study period') to very low (for the outcome 'Exacerbation rates'), based on lack of blinding, statistical heterogeneity and imprecision.

AUTHORS' CONCLUSIONS

In this updated review with five new included studies, tailoring asthma medications based on FeNO levels (in comparison with primarily guideline management) significantly decreased the number of children who had one or more exacerbations over the study period but did not impact on the day-to-day clinical symptoms or inhaled corticosteroid doses. Therefore, the use of FeNO to guide asthma therapy in children may be beneficial in a subset of children, it cannot be universally recommended for all children with asthma.Further RCTs need to be conducted and these should encompass different asthma severities, different settings including primary care and less affluent settings, and consider different FeNO cut-offs.

Exhaled nitric oxide levels to guide treatment for adults with asthma

BACKGROUND

Asthma guidelines aim to guide health practitioners to optimise treatment for patients so as to minimise symptoms, improve or maintain good lung function, and prevent acute exacerbations or flare-ups. The principle of asthma guidelines is based on a step-up or step-down regimen of asthma medications to maximise good health outcomes using minimum medications. Asthma maintenance therapies reduce airway inflammation that is usually eosinophilic. Tailoring asthma medications in accordance with airway eosinophilic levels may improve asthma outcomes such as indices of control or reduce exacerbations or both. Fractional exhaled nitric oxide (FeNO) is a marker of eosinophilic inflammation, and as it is easy to measure, has an advantage over other measurements of eosinophilic inflammation (for example sputum eosinophils).

OBJECTIVES

To evaluate the efficacy of tailoring asthma interventions based on exhaled nitric oxide (FeNO), in comparison to not using FeNO, that is management based on clinical symptoms (with or without spirometry/peak flow) or asthma guidelines or both, for asthma-related outcomes in adults.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of Trials, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and reference lists of articles. The last searches were undertaken in June 2016.

SELECTION CRITERIA

All randomised controlled trials (RCTs) comparing adjustment of asthma medications based on exhaled nitric oxide levels compared to not using FeNO, that is management based on clinical symptoms (with or without spirometry/peak flow) or asthma guidelines or both.

DATA COLLECTION AND ANALYSIS

We reviewed results of searches against predetermined criteria for inclusion. We independently selected relevant studies in duplicate. Two review authors independently assessed trial quality and extracted data. We contacted study authors for further information, receiving responses from four.

MAIN RESULTS

We included seven adult studies; these studies differed in a variety of ways including definition of asthma exacerbations, FeNO cutoff levels used (15 to 35 ppb), the way in which FeNO was used to adjust therapy, and duration of study (4 to 12 months). Of 1700 randomised participants, 1546 completed the trials. The mean ages of the participants ranged from 28 to 54 years old. The inclusion criteria for the participants in each study varied, but all had a diagnosis of asthma and required asthma medications. In the meta-analysis, there was a significant difference in the primary outcome of asthma exacerbations between the groups, favouring the FeNO group. The number of people having one or more asthma exacerbations was significantly lower in the FeNO group compared to the control group (odds ratio (OR) 0.60, 95% confidence interval (CI) 0.43 to 0.84). The number needed to treat to benefit (NNTB) over 52 weeks was 12 (95% CI 8 to 32). Those in the FeNO group were also significantly more likely to have a lower exacerbation rate than the controls (rate ratio 0.59, 95% CI 0.45 to 0.77). However, we did not find a difference between the groups for exacerbations requiring hospitalisation (OR 0.14, 95% CI 0.01 to 2.67) or rescue oral corticosteroids (OR 0.86, 95% CI 0.50 to 1.48). There was also no significant difference between groups for any of the secondary outcomes (FEV1, FeNO levels, symptoms scores, or inhaled corticosteroid doses at final visit).We considered three included studies that had inadequate blinding to have a high risk of bias. However, when these studies were excluded from the meta-analysis, the difference between the groups for the primary outcomes (exacerbations) remained statistically significant. The GRADE quality of the evidence ranged from moderate (for the outcome 'exacerbations') to very low (for the outcome 'inhaled corticosteroid dose at final visit') based on the lack of blinding and statistical heterogeneity. Six of the seven studies were industry supported, but the company had no role in the study design or data analyses.

AUTHORS' CONCLUSIONS

With new studies included since the last version of this review, which included adults and children, this updated meta-analysis in adults with asthma showed that tailoring asthma medications based on FeNO levels (compared with primarily on clinical symptoms) decreased the frequency of asthma exacerbations but did not impact on day-to-day clinical symptoms, end-of-study FeNO levels, or inhaled corticosteroid dose. Thus, the universal use of FeNO to help guide therapy in adults with asthma cannot be advocated. As the main benefit shown in the studies in this review was a reduction in asthma exacerbations, the intervention may be most useful in adults who have frequent exacerbations. Further RCTs encompassing different asthma severity, ethnic groups in less affluent settings, and taking into account different FeNO cutoffs are required.

Fractional exhaled nitric oxide-measuring devices: technology update

The measurement of exhaled nitric oxide (NO) has been employed in the diagnosis of specific types of airway inflammation, guiding treatment monitoring by predicting and assessing response to anti-inflammatory therapy and monitoring for compliance and detecting relapse. Various techniques are currently used to analyze exhaled NO concentrations under a range of conditions for both health and disease. These include chemiluminescence and electrochemical sensor devices. The cost effectiveness and ability to achieve adequate flexibility in sensitivity and selectivity of NO measurement for these methods are evaluated alongside the potential for use of laser-based technology. This review explores the technologies involved in the measurement of exhaled NO.

Comparison of two exhaled nitric oxide analyzers: the NIOX MINO hand-held electrochemical analyzer and the NOA280i stationary chemiluminescence analyzer

BACKGROUND AND OBJECTIVE

Measurement of the fraction of nitric oxide (FeNO) in exhaled air is useful in the management of asthma. A new hand-held nitric oxide (NO) analyzer, the NIOX MINO, is simple and easy to use in clinical practice. In this study, FeNO values measured using the NIOX MINO were compared with those obtained using a stationary chemiluminescence analyzer, the Sievers NOA280i.

METHODS

FeNO was measured in 100 adults, using both the NIOX MINO and the NOA280i. Nine (9.0%) of these subjects had asthma. The first acceptable measurement with the NIOX MINO and the mean of two acceptable measurements with the NOA280i were compared.

RESULTS

There was a significant correlation between FeNO concentrations measured with the two devices (r = 0.876, P < 0.001). A Bland-Altman plot showed a high degree of agreement between the two devices: the mean inter-device difference was 3.3 parts per billion (ppb), and the 95% limits of agreement were -7.0 and 13.6 ppb. In addition, the mean relative difference was 14.5%, with the 95% limits of agreement being -33.7 and 62.7%. The mean value (± standard error of the mean) for FeNO as measured with the NIOX MINO (18.8 ± 0.9 ppb) was significantly lower than that measured with the NOA280i (22.1 ± 1.2 ppb, P < 0.001).

CONCLUSIONS

There was a significant correlation, but only moderate agreement, between FeNO values measured with the NIOX MINO and those measured with the NOA280i, with the NIOX MINO values being significantly lower than the NOA280i values. Significant differences in FeNO values obtained with these two NO analyzers should be considered when interpreting the results of FeNO measurements.

Exhaled nitric oxide (FeNO) as a non-invasive marker of airway inflammation

Nitric oxide (NO), previously very famous for being an environmental pollutant in the field of pulmonary medicine, is now known as the smallest, lightest, and most famed molecule to act as a biological messenger. Furthermore, recent basic researches have revealed the production mechanisms and physiological functions of nitric oxide in the lung, and clinical researches have been clarifying its tight relation to airway inflammation in asthma. On the bases of this knowledge, fractional nitric oxide (FeNO) has now been introduced as one of the most practical tools for the diagnosis and management of bronchial asthma.

Measurement of exhaled nitric oxide in a general population sample: a comparison of the Medisoft HypAir FE(NO) and Aerocrine NIOX analyzers

BACKGROUND AND OBJECTIVE

Measuring the fraction of nitric oxide in exhaled breath (FE(NO)) is increasingly utilized to assess airway inflammation in asthma. The primary aim of this study was to compare exhaled nitric oxide measurements obtained using two devices from different manufacturers, that is, the recently marketed portable and electrochemical-based Medisoft HypAir FE(NO) and the well-established chemiluminescence-based Aerocrine NIOX analyzer, in an unselected population.

METHODS

FE(NO) measurements were conducted in 106 subjects (86 healthy; 20 asthmatic; 56.6% atopic). Atopy and health status were assessed by skin prick tests and questionnaire, respectively.

RESULTS

The two instruments showed strong correlation over a wide range of FE(NO) measurements (8-261.3 ppb with the HypAir, 5.6-156.8 ppb with the NIOX; r = 0.98; p < .0001). This correlation was observed in the population as a whole, as well as in healthy non-atopics, healthy atopics, and atopic asthmatics when considered separately. The measurements on the HypAir FE(NO) were consistently 1.6 times (95% CI 1.11-2.05) higher than those obtained with the NIOX.

CONCLUSIONS

FE(NO) measurements obtained with the HypAir FE(NO) correlated well with the NIOX, but were approximately 1.6 times higher. Therefore, a conversion factor is required if results are to be compared with the NIOX instrument.

Exhaled nitric oxide and influencing factors in a random population sample

The aim of the current study was to determine the impact and interaction of important influencing factors on the fraction of exhaled nitric oxide (FeNO). FeNO was measured in a population-based sample of 1250 middle-aged subjects from the KORA F4 cohort (Augsburg, Germany). Analysis of covariance models was performed including the factors age, height, FVC, FEV(1), sex, current smoking status, recent respiratory tract infection, and respiratory allergy. Geometric mean (SD as factor; 95% confidence interval as factor) FeNO was 13.9 (1.9; 1.033) ppb. FeNO significantly depended on age, height, smoking, infection and allergy. Smoking reduced FeNO by 21%, while infection and allergy led to increases by 9 and 11%, respectively. Increases in age by 10 years and in height by 10 cm were associated with increases of FeNO by 15 and 10%, respectively. Non-smokers demonstrated independent multiplicative superposition of factors affecting FeNO while the effect of allergy was virtually eliminated in smokers without infection. We conclude that in middle-aged non-smokers the effects of infection, age and height can be easily taken into account and do not significantly disturb the effect of respiratory tract allergies on FeNO. In current smokers, however, effects were heterogeneous and information on smoking intensity seems to be useful for better adjustment.

Long term performance characteristics of an electrochemical nitric oxide analyser

BACKGROUND

The NIOX MINO(®) is a nitric oxide (FE(NO)) analyser based on electrochemical technology. It includes a replaceable sensor. Quality control procedures are recommended, but regular calibration is not possible. We aimed to evaluate the performance characteristics of the NIOX MINO(®) to identify if reproducibility changed over time, or with different sensors. Also, there are reports that reproducibility of FE(NO) may be reduced in patients with high FE(NO): our secondary aim was to address this issue.

METHODS

Reproducibility in 24 separate sensor-analyser units was calculated on three occasions over two months in 17 patients. These included 9 patients whose FE(NO) was high (mean 80 ppb) and 8 in whom FE(NO) was low (mean 16 ppb).

RESULTS

One device failed quality control testing. For the remaining 23 sensor-analyser combinations, the mean coefficient of variation was 4.0% (range 1.2-7.2%) at baseline, 3.6% (range 2.0-7.0) at one month, and 3.6% (range 1.6-7.6%) at two months. The 95% C.I. for the mean limits of agreement for FE(NO) was ± 4.2 ppb (range 0.9-9.6 ppb), ± 3.8 ppb (range 1.6-6.9 ppb) and ± 3.2 ppb (range 1.2-6.8 ppb) respectively (NS). The limits of agreement exceeded the manufacturer's specifications (± 5 ppb) in 0 devices at baseline, 3 (13%) at one month, and 5 (22%) at two months.

CONCLUSIONS

Reproducibility of FE(NO) using the NIOX MINO(®) was within clinically acceptable limits (± 10 ppb) and was generally stable. However, with time, a proportion of individual sensor-analyser combinations yielded variability outside the manufacturer's specifications.

Reference values and determinants of exhaled nitric oxide in healthy Korean adults

BACKGROUND

Measuring fractional exhaled nitric oxide (FeNO) provides an indication of airway inflammation and is used as an inflammatory marker for asthma management. However, reference values and determinants of FeNO levels are not well defined in healthy Asian adults. This study aimed to establish FeNO reference values in nonsmoking, healthy Asian adults and to determine the factors related to FeNO levels.

METHODS

The authors measured FeNO in 166 nonsmoking, healthy Korean adults and collected data regarding factors possibly associated with FeNO, including age, height, weight, and respiratory symptoms. Lung function was measured using spirometry, and atopic status was determined based on the skin-prick test.

RESULTS

In a multivariate linear regression analysis, FeNO levels were positively associated with male gender (p = .008) and atopy (p = .044) after adjusting for age, height, weight, forced expiratory volume in one second (FEV(1)), and chronic rhinitis. Reference values were presented according to gender and atopic status, and the mean FeNO value was highest in male atopic subjects (37.3 +/- 12.1 ppb), followed by nonatopic males (33.9 +/- 14.3 ppb), atopic females (28.6 +/- 17.7 ppb), and nonatopic females (24.1 +/- 10.6 ppb). In healthy Korean adults, FeNO levels showed a significant and independent association with male gender and atopy.

CONCLUSIONS

We believe that the presented FeNO reference values and the determining factors could be useful for research and clinical practice in the adult Asian population.

Fractional exhaled nitric oxide in asthma: an update

In asthma, clinical symptoms and lung function are insensitive in reflecting the underlying airway inflammation, and monitoring of this process has only recently become available. Fractional exhaled nitric oxide (Fe(NO)) is now recognized as a reliable surrogate marker of eosinophilic airway inflammation and offers the advantage of being completely non-invasive and very easy to obtain. This review summarizes the clinical use of Fe(NO) in asthma. It covers the relationship between Fe(NO) and the underlying eosinophilic inflammation, the pathophysiology and production of Fe(NO), technical aspects of Fe(NO) measurement and potential confounding factors in interpreting levels. Fe(NO) reference values and the role of Fe(NO) in asthma assessment, diagnosis and management are also discussed.

Exhaled nitric oxide in a population-based study of southern California schoolchildren

Background

Determinants of exhaled nitric oxide (FeNO) need to be understood better to maximize the value of FeNO measurement in clinical practice and research. Our aim was to identify significant predictors of FeNO in an initial cross-sectional survey of southern California schoolchildren, part of a larger longitudinal study of asthma incidence.

Methods

During one school year, we measured FeNO at 100 ml/sec flow, using a validated offline technique, in 2568 children of age 7–10 yr. We estimated online (50 ml/sec flow) FeNO using a prediction equation from a separate smaller study with adjustment for offline measurement artifacts, and analyzed its relationship to clinical and demographic characteristics.

Results

FeNO was lognormally distributed with geometric means ranging from 11 ppb in children without atopy or asthma to 16 ppb in children with allergic asthma. Although effects of atopy and asthma were highly significant, ranges of FeNO for children with and without those conditions overlapped substantially. FeNO was significantly higher in subjects aged > 9, compared to younger subjects. Asian-American boys showed significantly higher FeNO than children of all other sex/ethnic groups; Hispanics and African-Americans of both sexes averaged slightly higher than non-Hispanic whites. Increasing height-for-age had no significant effect, but increasing weight-for-height was associated with decreasing FeNO.

Conclusion

FeNO measured offline is a useful biomarker for airway inflammation in large population-based studies. Further investigation of age, ethnicity, body-size, and genetic influences is needed, since they may contribute to substantial variation in FeNO.

Comparison of exhaled nitric oxide measurements between NIOX MINO electrochemical and Ecomedics chemiluminescence analyzer

BACKGROUND

Exhaled nitric oxide (eNO) is an established, noninvasive biomarker of active airway inflammation in (atopic) asthma. Treatment with anti-inflammatory therapy, such as inhaled corticosteroids, effectively decreases eNO levels. The NIOX MINO (MINO) is a hand-held, relatively inexpensive, electrochemical device that has been shown to yield comparable eNO measurements to the NIOX stationary unit.

AIM

To compare measurements of MINO with another widely used and validated stationary chemiluminescence analyzer, the Ecomedics (ECO).

METHODS

We performed subsequent eNO measurements on ECO and MINO in 50 subjects (19 healthy volunteers, 18 healthy smokers and 13 non-smoking, atopic asthmatics, not on controller therapy) on two visits 4-10 days apart. The mean of three acceptable measurements by ECO and the first acceptable measurement with the MINO were used for analysis.

RESULTS

Both devices yielded reproducible eNO values for all subjects on both visits, with an overall CV of 22.7% (ECO) and 18.3% (MINO). A significant correlation was found between both devices (r=0.97, p<0.0001). Bland-Altman plots showed a high degree of agreement for the entire study population (mean difference MINO vs ECO=-10%; 95% limit of agreement were -36% and +28%) and in the three individual subgroups.

CONCLUSIONS

Exhaled NO values measured with the MINO are reproducible and in agreement with the ECO. Our results add further evidence to the reliability of the MINO and warrant its applicability in research and clinical practice.

Exhaled nitric oxide: independent effects of atopy, smoking, respiratory tract infection, gender and height

Measurement of exhaled nitric oxide is widely used in respiratory research and clinical practice, especially in patients with asthma. However, interpretation is often difficult, due to common interfering factors, and little is known about interactions between factors. We assessed the influences and interactions of factors such as smoking, respiratory tract infections and respiratory allergy concerning exhaled nitric oxide values, with the aim to derive a scheme for adjustment. We studied 897 subjects (514 females, 383 males; mean age+/-standard deviation 34.5+/-13.0 years) with and without respiratory allergy (allergic rhinitis and/or asthma), smoking and respiratory tract infection. Logarithmic nitric oxide levels were described by an additive model comprising respiratory allergy, smoking, respiratory tract infection, gender and height (p0.001 each), without significant interaction terms. Geometric mean was 17.5ppb in a healthy female non smoker of height 170cm, whereby respiratory allergy corresponded to a change by factor 1.50, smoking 0.63, infection 1.24, male gender 1.17, and each 10cm increase (decrease) in height to 1.11 (0.90). Factors were virtually identical when excluding asthma and using the category allergic rhinitis instead of respiratory allergy (n=863). Within each category formed by combinations of these different predictors, the range of residual variation was approximately constant. We conclude that the factors influencing exhaled nitric oxide, which we analyzed, act independently of each other. Thus, circumstances such as smoking and respiratory tract infection do not appear to affect the usefulness of exhaled nitric oxide, provided that appropriate factors for adjustment are applied.

Performance of an exhaled nitric oxide and carbon dioxide sensor using quantum cascade laser-based integrated cavity output spectroscopy

Exhaled nitric oxide (NO) is an important biomarker in asthma and other respiratory disorders. The optical performance of a NOCO(2) sensor employing integrated cavity output spectroscopy (ICOS) with a quantum cascade laser operating at 5.22 microm capable of real-time NO and CO(2) measurements in a single breath cycle is reported. A NO noise-equivalent concentration of 0.4 ppb within a 1-sec integration time is achieved. The off-axis ICOS sensor performance is compared to a chemiluminescent NO analyzer and a nondispersive infrared (NDIR) CO(2) absorption capnograph. Differences between the gas analyzers are assessed by the Bland-Altman method to estimate the expected variability between the gas sensors. The off-axis ICOS sensor measurements are in good agreement with the data acquired with the two commercial gas analyzers. This work demonstrates the performance characteristics and merits of mid-infrared spectroscopy for exhaled breath analysis.

Reference values for exhaled nitric oxide (reveno) study

Background

Despite the widespread use of fractional exhaled nitric oxide (FE_NO) as a biomarker of airways inflammation, there are no published papers describing normal FE_NO values in a large group of healthy adults.

Objective

The aim of this study was to establish adult FE_NO reference values according to the international guidelines.

Methods

FE_NO was measured in 204 healthy, non-smoking adults with normal spirometry values using the on-line single-breath technique, and the results were analysed chemiluminescently.

Results

The main result of the study was the significant difference in FE_NO values between men and women, thus indicating that gender-based reference FE_NO values are necessary. The FE_NO levels obtained at expiratory flows of 50 ml/s ranged from 2.6 to 28.8 ppb in men, and from 1.6 to 21.5 ppb in women.

Conclusion

We propose reference FE_NO values for healthy adult men and women that could be used for clinical and research purposes.

A comparison of exhaled nitric oxide measurements performed using three different analysers

INTRODUCTION

Exhaled nitric oxide (NO) is an established technique for monitoring airway inflammation. We have compared exhaled NO measurements from 3 different analysers; Ecomedics (E), Niox (N) and Logan (L).

METHODS

Thirty subjects (10 non-smoking healthy subjects, 10 non-smoking patients with asthma and 10 ex-smoking COPD patients) performed 3 repeated measurements of exhaled NO at a flow rate of 50 ml/s on each of the 3 analysers. Within analyser variability was determined by calculating the repeatability coefficient for each analyser. Differences between analysers were assessed by (1) the differences between group means and (2) the Bland Altman method to estimate the variability expected for an individual using the 3 analysers.

RESULTS

The repeatability coefficients (expressed as ratios) were 1.12, 1.19 and 1.19 for N, E and L, respectively. There were significant differences (P<0.05) between analysers; the Logan analyser gave the highest group mean values and Ecomedics gave the lowest group mean values. Differences between analysers were observed in all subject groups (healthy, asthma, COPD). Similar results were obtained in the 3 groups when analysed separately. Bland Altman analysis gave the following ratios [data are mean ratio (95% limits of agreement)]; N:E 1.59 (1.02-2.50), L:N 1.23 (0.72-2.13), L:E 1.96 (1.09-3.57).

CONCLUSION

Our findings indicate that exhaled NO measurements in healthy subjects and patients with airways disease differ according to the type of analyser used.