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PubMed1998

[Study of appropriate expiratory velocity when measuring exhaled nitric oxide (NO) concentration].

We studied the appropriate expiratory velocity when measuring exhaled NO concentration by constant expiratory flow maneuver in relation to height and the required time for measurement, and obtained the following results. 1) There was a significant positive correlation between height and the required time. 2) There was a significant negative correlation between expiratory velocity and the required time. 3) Percent ratios of children who reached the plateau of exhaled NO concentration were significantly higher when expiratory velocity was over 2000 ml/minute. These findings suggest that expiratory velocity of over 2000 ml/minute may be appropriate when measuring exhaled NO concentration.

Adult↗
PubMed2006

Validation of a hand-held exhaled nitric oxide analyzer for use in children.

Measurements of exhaled nitric oxide (FE(NO)) may be useful in the diagnosis and management of asthma in children. A new hand-held device (MINO, Aerocrine) for measuring FE(NO) has been marketed but has not been validated in a pediatric population. The objective is to validate the MINO against the NIOX analyzer. This was a randomized cross-over study where FE(NO) was measured in a single assessment using the MINO and NIOX. Children were recruited from a respiratory clinic and had six attempts to provide a FE(NO) measurement with each analyzer. Fifty-five children were enrolled, 33 boys, median age 9 years. A mean FE(NO) value was obtained in 39 children with MINO and 44 with NIOX. Paired mean FE(NO) values were obtained in 34 children and the values were higher for the NIOX (mean difference 3.9 ppb limits of agreement -1.1, 8.9). The differences between analyzers became greater at higher FE(NO) values. The first FE(NO) value using the MINO was 24 ppb and the mean of all FE(NO) values using the MINO was 27 ppb (difference not significant). Exhaled NO values were comparable between the two analyzers although there was greater consistency at lower values. The findings of the study do not contradict the manufacturer's recommendation that only one FE(NO) value is required with the MINO, however, we suggest that the mean of at least two values should be reported in children.

Adolescent↗
PubMed2004

Exhaled Interleukine-6 and 8-isoprostane in chronic obstructive pulmonary disease: effect of carbocysteine lysine salt monohydrate (SCMC-Lys).

Chronic obstructive pulmonary disease (COPD) is characterized by an airways inflammation and by an enhanced generation of reactive oxygen species. The aim of our study was to assess the inflammation and the oxidative stress in airways of COPD patients with acute exacerbation of disease and in stability. Furthermore, we investigated the anti-inflammatory and antioxidant effects of 6 months treatment with carbocysteine lysine salt monohydrate (SCMC-Lys) in COPD. We studied 30 mild acute COPD, 10 mild stable COPD and 15 healthy subjects. 8-isoprostane and Interleukine-6 were measured in their breath condensate through immunoassay. Significantly higher concentrations of exhaled 8-isoprostane and Interleukine-6 were found in acute COPD patients compared to stable COPD and healthy controls (21.8+/-5.1 vs. 13.2+/-2.0 vs. 4.7+/-1.8 pg/ml and 7.4+/-0.9 vs. 5.8+/-0.2 vs. 2.7+/-0.6 pg/ml, p<0.0001). COPD patients treated with SCMC-Lys showed a marked reduction of exhaled 8-isoprostane and Interleukine-6 (8.9+/-1.5 and 4.6+/-0.8 pg/ml, p<0.0001). These findings suggest that there is an increase of 8-isoprostane and Interleukine-6 concentrations in the breath condensate of COPD patients compared to healthy controls especially during acute exacerbations of the disease. Moreover, we showed an anti-inflammatory and antioxidant effect of short-term administration of SCMC-Lys in COPD, suggesting the importance of a further placebo-controlled study that should evaluate the effects of this drug.

Adult↗
PubMed2005

Exhaled breath condensate cysteinyl leukotrienes are increased in children with exercise-induced bronchoconstriction.

BACKGROUND: It is recognized that airway inflammation has a central role in the pathogenesis of asthma, but how it relates to exercise-induced bronchoconstriction (EIB) is not completely understood. OBJECTIVE: The aim of our study was to investigate the relationship between EIB and baseline concentrations of cysteinyl leukotrienes (Cys-LTs) and other inflammatory markers in exhaled breath condensate (EBC). METHODS: EBC was collected, and the fraction of exhaled nitric oxide (FE NO ) was measured in a group of 19 asthmatic children, after which they performed a treadmill exercise test. Fourteen healthy children were enrolled as control subjects. RESULTS: The asthmatic children were divided into the EIB group (decrease in FEV 1 , > or =12%) and the non-EIB group. The EBC was analyzed for the presence of Cys-LTs, leukotriene B 4 , and ammonia. Asthmatic patients with EIB (mean FEV 1 decrease, 23% +/- 3%) had higher Cys-LT concentrations than either asthmatic patients without EIB or control subjects (42.2 pg/mL [median] vs 11.7 pg/mL and 5.8 pg/mL; P < .05 and P < .001, respectively). Ammonia concentrations were lower in both the EIB and non-EIB groups than in control subjects (253.2 microM and 334.6 microM vs 798.4 microM; P < .01 and P < .05, respectively). No difference in EBC leukotriene B 4 levels was found among the 3 groups. Both asthmatic groups had higher FE NO levels than control subjects ( P < .001). EBC Cys-LT ( P < .01; r = 0.7) and FE NO ( P < .05; r = 0.5) values both correlated significantly with the postexercise FEV 1 decrease. CONCLUSION: this study shows that EBC Cys-LT values are higher in asthmatic children with EIB and correlate with the decrease in FEV 1 after exercise. These findings suggest that the pathways of both Cys-LT and nitric oxide are involved in the pathogenesis of EIB.

Acetates↗
PubMed2005

Sensitive and accurate analyses of free 3-nitrotyrosine in exhaled breath condensate by LC-MS/MS.

The quantitative determination of 3-nitro-l-tyrosine, a biological marker for inflammatory processes, in exhaled breath condensate (EBC) is described. The clean-up and preconcentration was performed by solid phase extraction (SPE). After liquid chromatography the specific detection was performed by tandem mass spectrometry using electron spray ionisation and selected reaction monitoring (SRM). 13C9-3-nitrotyrosine was used as an internal standard. For reliability, tests for the precision of the method, the losses during preparation, a test for nitrating artifacts and the comparibility of calibrants in EBC and buffer solution were performed. The calibration of the method was linear over a range of 10-500 pg/mL. The within-run coefficients of variation (CV) of the samples were found to be 8.4% at 25 pg/mL and 8.3% at 250 pg/mL. The day-to-day CV was found to be 11.2%. The limit of quantification was 3.9 pg/mL. The losses during preparation were 15%. The discrepancy between the calibration with EBC and buffer solution was below 10%. No artificial production of 3-nitrotyrosine was observed during the procedure. The application of the method on the EBC samples of healthy smokers (N=10) and non-smokers (N=10) showed no difference between the two groups. The concentration of 3-nitrotyrosine ranged between the limit of quantification and 184 pg/mL and was distinctly lower than data detected by an immunoassay procedure. The procedure was proven to be accurate, sensitive and in contrast to GC methods less elaborate and is recommended for the determination of 3-nitrotyrosine in exhaled breath condensate.

Adult↗
PubMed2005

Selective quantification of free 3-nitrotyrosine in exhaled breath condensate in asthma using gas chromatography/tandem mass spectrometry.

Reactive nitrogen species can cause oxidative modifications of certain amino acid residues in proteins, notably the modification of tyrosine to 3-nitrotyrosine (3-NT), which is a potentially useful marker of oxidative stress. Since lung diseases are associated with airway inflammation and oxidative stress, quantification of 3-NT in exhaled breath condensate (EBC) may provide a non-invasive means for monitoring ongoing inflammatory processes. 3-NT-like immunoreactivity has previously been detected in EBC, but no definitive evidence for the presence of 3-NT in EBC is available. Here, a method based on gas chromatography/negative ion chemical ionization/tandem mass spectrometry was established for the quantification of free 3-NT in EBC. The detection limit was 0.56 pM (corresponding to 3.0 amol microl(-1) sample injected) and the method was found to give linear results (r2 > 0.999) in the concentration range of 0-5.0 nM. The coefficient of variation (CV) for within-day and between-day precision were 11 and 12%, respectively. No artifactual nitration was observed during sample processing. The method was applied to study subjects with asthma (n = 8), and healthy subjects (n = 10), but only a slight non-significant increase in 3-NT levels was found in the former group (median [interquartile ranges]; 99 [50-547] amol s(-1) vs. 75 [35-147] amol s(-1)). No correlation with exhaled nitric oxide (NO), pulmonary function or EBC levels of total protein was observed. The 3-NT levels were much lower compared to previously reported levels, based on immunochemical measurements. The method does not allow the simultaneous quantification of tyrosine in samples.

Adult↗
PubMed2004

[The measurement of exhaled nitric oxide, a new tool in the management of asthma?].

A GOOD DIAGNOSTIC TEST FOR ASTHMA: Chronic airway inflammation, main feature of asthma, can be assessed by measuring the exhaled nitric oxide (NO) level. Measurement of NO is standardized, non-invasive and easy to use in both children and adults. Studies have shown that it is a good diagnostic test for asthma when NO is high. However, other conditions or pathologies must be searched for because they may influence the results. ITS PLACE IN TREATMENT: Although exhaled NO helps to characterise the patients with asthma, other studies are required to show that it can help to improve the follow-up of such patients. Nevertheless, this tool has not yet been validated in the daily treatment of asthma and further research is still ongoing.

Adult↗
PubMed2006

Exhaled nitric oxide in single and repetitive prolonged exercise.

This study was performed to determine the influence of single and repetitive exercise on nitric oxide (NO) concentration in the lung. Exhaled NO concentration (FE(NO)) was measured during a constant-flow exhalation manoeuvre (170 ml x s(-1), against a 10 cmH2O resistance) in healthy individuals (a) during and after a 100-min square-wave exercise of between 25 and 60% of maximal power output (n = 18) and (b) before and after five successive prolonged exercises (90-120 min, 75-85% of maximal heart rate) separated by 48 or 24 h (n = 8). The FE(NO0.170) was decreased during and after the 100-min exercise test (mean +/- s(x): 58.5 +/- 3.7% and 76.7 +/- 5.2% of resting value at 90 min of exercise and 15 min post-exercise, respectively; P < 0.05). The five successive exercise sessions induced a similar post-exercise FE(NO0.170) decrement (73.1 +/- 2.9% of resting value 15 min post-exercise), while basal FE(NO0.170) values were not different between the five sessions (P > 0.05). These results suggest that prolonged exercise induces a reduction in NO concentration within the lung that lasts for several minutes after the end of exercise. However, repetitive exercises (at least every 24 h) allow complete NO recovery from one session to another. The implication of such a decrease in NO availability within the lung remains to be clarified.

Adult↗
PubMed2006

Effect of inhaled steroid therapy on exhaled nitric oxide and bronchial responsiveness in children with asthma.

Inhaled steroid therapy is reported to reduce the level of exhaled nitric oxide (eNO), but the effects of inhaled corticosteroids (ICS) on bronchial hyperresponsiveness (BHR) have been controversial. The aim of this study was to determine the effects of ICS on the relationship between eNO and BHR. Twenty-six children with asthma were recruited, including 14 children who were receiving ICS (ICS group) and 12 who were not (ICS-naive group). The fractional exhaled nitric oxide concentration (FE(NO)) was examined by the recommended online method. To evaluate BHR, an acetylcholine challenge test was performed. In the ICS-naive group, FE(NO) was significantly correlated with PC20 (p < 0.05, r = -0.70), but not in the ICS group. In conclusion, FE(NO) was significantly correlated with BHR in the ICS-naive group, but this relationship was not present in the ICS group. Our results suggest that the use of ICS should be taken into consideration when evaluating the relation between BHR and airway inflammation.

Acetylcholine↗
PubMed2005

The relationship of exhaled nitric oxide to airway inflammation and responsiveness in children.

Exhaled nitric oxide (eNO) is a potential tool in epidemiological studies of asthma. It was hypothesized that in a cross-sectional survey of asthma in adolescent children, eNO may contribute to the detection of this disease. A cohort of Australian school children in two educational years (n = 107, aged 14.7 +/- 2.3 years, 42.9% female) were surveyed in terms of exhaled nitric oxide (eNO), which was compared with other indicators of asthma: asthma symptoms, atopy [skin prick tests (SPT)], hypertonic saline bronchial reactivity, sputum inflammatory cells and eosinophilic cationic protein. Significant positive correlations were found with eNO and number of positive skin prick tests (p = 0.001; n = 98), symptoms (p = 0.05; n = 107), sputum eosinophils (p = 0.025; n = 83), and sputum eosinophilic cationic protein (p = 0.009; n = 83). There was no significant relationship with airway hyperresponsiveness (p = 0.3; n = 15). eNO had a negative predictive value for asthma of 83%, and a positive predictive value of 54%, which is comparable with most current tests for diagnosing asthma. eNO appears to be a useful indicator of atopy and airway inflammation, but in this population it was not closely related to airway hyperresponsiveness.

Adolescent↗
PubMed2005

Exhaled nitric oxide predicts airway hyper-responsiveness to hypertonic saline in children that wheeze.

BACKGROUND: Exhaled nitric oxide (eNO) has shown good validity for the assessment of airway inflammation in asthmatic children. In large-scale epidemiological studies, this method would be preferred above airway challenge tests, because it is a quick and easy applicable tool. OBJECTIVE: In this study, we aimed to assess the discriminatory capacity of eNO, and prechallenge FEV1 for airway hyper-responsiveness (AHR) in 8-13-year old schoolchildren. MATERIALS AND METHODS: Parents completed the ISAAC questionnaire, and children were tested for atopy, AHR to hypertonic (4.5%) saline (HS), and eNO. Diagnostic value was assessed by the area under the receiver operating curves (ROC), and calculation of positive and negative predicted values at different cut-off points for eNO and prechallenge FEV1. RESULTS: Areas under the ROC-curves of AHR were 0.65 for eNO and 0.62 for FEV1. Values increased to 0.71 and respectively 0.75 for a combined occurrence of AHR and current wheeze. Highest sensitivity and specificity were obtained at a cut-off value of 43 ppb for eNO and 103% predicted for FEV1. At these cut-off values, the positive predictive values for the presence of AHR in symptomatic children were respectively 83% (eNO) and 33% (FEV1), and negative predictive values in asymptomatic children were, respectively, 90 (eNO) and 80% (FEV1). CONCLUSION: Exhaled nitric oxide is a valid screening tool for AHR to HS in children that present with current wheeze, and it outperforms FEV1 as a predictor of AHR.

Adolescent↗
PubMed2005

Measurement of exhaled nitric oxide in young children during tidal breathing through a facemask.

Measurement of exhaled nitric oxide (eNO) offers a non-invasive means for assessment of airway inflammation. The currently available methods are difficult to apply in preschool children. We evaluated four methods potentially applicable for eNO measurement during tidal breathing in young children. eNO was assessed during tidal breathing in 24 children, 2-7 yr old, using a facemask which separated nasal and oral airflow. Facemasks with and without a one-way valve allowing exhalation through the nose were used. Expiratory flow control was not attempted. Measurements of eNO were performed both on-line and off-line. In 11 children, 8-12 yr old, measurements were compared with the standard single breath on-line method. eNO was significantly lower applying the one-way valve in on-line and off-line measurements in comparison with measurements without the valve [4.6 and 3.9 parts per billion (ppb) vs. 6.9 ppb and 6.5 ppb]. The mean within subject coefficient of variation (CV) was significantly lower in on-line measurements with the one-way valve (9.6%) compared with the other three methods (18.8, 27.7 and 29.3% respectively). Measurements with a facemask fitted with a one-way valve yielded similar eNO levels as the standard single breath method (7.0 ppb vs. 6.9 ppb) and reproducibility (9.8% vs. 7.1%). In conclusion, reproducible measurements of eNO can be obtained without control of expiration flow using a facemask fitted with a one-way valve on the nasal compartment. The likely explanation to this is that the one-way valve reduces the admixture of nasal NO, thereby improving the reliability of eNO measurements.

Asthma↗
PubMed2005

Relationship between exhaled nitric oxide and atopy in Asian young adults.

OBJECTIVES: The relationship between exhaled nitric oxide and atopy is controversial. The aim of this study was to determine the relationship between exhaled nitric oxide (FE(NO)) and atopy in Asian young adults. METHODOLOGY: Subjects were assessed by: (i) the International Study of Asthma and Allergies in Childhood questionnaire to differentiate asthmatic from nonasthmatic and rhinitis from non-rhinitis subjects; (ii) skin prick testing to 10 allergens; and (iii) FE(NO) measurements performed online at a flow rate of 50 mL/s. RESULTS: Complete results were available for 84 subjects. FE(NO) values were highest in atopic asthmatics (n = 34; median FE(NO), 59.8 p.p.b.; interquartile range, 30.4-85.5 p.p.b), followed by atopic nonasthmatics (n = 34; median, 38.4 p.p.b.; range, 16.7-49.3 p.p.b), nonatopic asthmatics (n = 5; median, 19.1 p.p.b.; range, 17.9-33.4 p.p.b), and lowest in nonatopic nonasthmatics (n = 11; median, 15.7 p.p.b.; range, 11.5-21.7 p.p.b). FE(NO) values were significantly higher in atopic (n = 68; median, 44.7 p.p.b.; range, 27.3-75.2 p.p.b) compared to nonatopic subjects (n = 16; median, 17.0 p.p.b.; range, 11.7-23.8 p.p.b.; P < 0.0001), regardless of asthma and rhinitis status. FE(NO) levels correlated with the severity of atopy (wheal size) for both asthmatic (r = 0.44, P = 0.005) and nonasthmatic subjects (r = 0.48, P = 0.001). There was no significant difference in FE(NO) levels between nonatopic asthmatics and nonatopic nonasthmatic subjects (P = 0.25). CONCLUSIONS: Increased FE(NO) levels are more reflective of atopy rather than asthma, and increased nitric oxide production may be predominantly a feature of atopy in asthmatics.

Adolescent↗
PubMed2006

Simulation of four-dimensional CT images from deformable registration between inhale and exhale breath-hold CT scans.

PURPOSE: We propose to simulate an artificial four-dimensional (4-D) CT image of the thorax during breathing. It is performed by deformable registration of two CT scans acquired at inhale and exhale breath-hold. MATERIALS AND METHODS: Breath-hold images were acquired with the ABC (Active Breathing Coordinator) system. Dense deformable registrations were performed. The method was a minimization of the sum of squared differences (SSD) using an approximated second-order gradient. Gaussian and linear-elastic vector field regularizations were compared. A new preprocessing step, called a priori lung density modification (APLDM), was proposed to take into account lung density changes due to inspiration. It consisted of modulating the lung densities in one image according to the densities in the other, in order to make them comparable. Simulated 4-D images were then built by vector field interpolation and image resampling of the two initial CT images. A variation in the lung density was taken into account to generate intermediate artificial CT images. The Jacobian of the deformation was used to compute voxel values in Hounsfield units. The accuracy of the deformable registration was assessed by the spatial correspondence of anatomic landmarks located by experts. RESULTS: APLDM produced statistically significantly better results than the reference method (registration without APLDM preprocessing). The mean (and standard deviation) of distances between automatically found landmark positions and landmarks set by experts were 2.7(1.1) mm with APLDM, and 6.3(3.8) mm without. Interexpert variability was 2.3(1.2) mm. The differences between Gaussian and linear elastic regularizations were not statistically significant. In the second experiment using 4-D images, the mean difference between automatic and manual landmark positions for intermediate CT images was 2.6(2.0) mm. CONCLUSION: The generation of 4-D CT images by deformable registration of inhale and exhale CT images is feasible. This can lower the dose needed for 4-D CT acquisitions or can help to correct 4-D acquisition artifacts. The 4-D CT model can be used to propagate contours, to compute a 4-D dose map, or to simulate CT acquisitions with an irregular breathing signal. It could serve as a basis for 4-D radiation therapy planning. Further work is needed to make the simulation more realistic by taking into account hysteresis and more complex voxel trajectories.

Algorithms↗
PubMed2003

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

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.

Adult↗
PubMedDate not supplied

Concentration of carbon dioxide in exhaled air in fluent and non-fluent speech.

The results of dynamic measurements of carbon dioxide (CO2, in %) in exhaled air during speech are presented. Fourteen stuttering persons and 14 persons with fluent speech took part in a test that involved independent speaking and echo-assisted speaking (delayed auditory feedback). A statistical comparative analysis of average levels of CO2 concentration registered during speech and resting respiration immediately before speaking indicated significant differences in non-fluent speech and insignificant differences in fluent speech. It was determined that the average concentration of CO2 in exhaled air while stuttering was 1/5 lower than the concentration of CO2 registered during fluent speaking.

Adolescent↗
PubMed2004

Exhaled nitric oxide levels and airway responsiveness to adenosine 5'-monophosphate in subjects with nasal polyposis.

BACKGROUND: It is widely appreciated that asthma is an inflammatory disease of the airways associated with airway hyperresponsiveness, and that nasal polyposis and asthma are related diseases. The objective of this study was to determine differences in exhaled nitric oxide (ENO) levels and airway responsiveness to adenosine 5'-monophosphate (AMP) between nonasthmatic patients with nasal polyposis and healthy controls. METHODS: Twenty patients without asthma with nasal polyposis and 16 healthy control subjects were enrolled in the study. Participants were challenged with increasing concentrations of AMP and methacholine. ENO was measured with the single-exhalation method. RESULTS: Bronchoconstriction in response to AMP was detected in 7 (35%) subjects with nasal polyposis. The geometric mean (95% CI) of ENO for subjects with nasal polyposis was 33.1 parts per billion (ppb) (24.0-45.7 ppb) compared with 12.3 ppb (8.5-18.2 ppb) for the healthy controls (p = 0.0002). ENO values were significantly higher in atopic than in nonatopic subjects with nasal polyposis [51.3 ppb (32.3-83.2 ppb) vs. 24.5 ppb (16.2-37.1 ppb), p = 0.02]. Nonatopic subjects with nasal polyposis also had higher concentrations of ENO than healthy control subjects (p = 0.016). CONCLUSIONS: Inhaled AMP causes airway narrowing in a significantly higher proportion of nonasthmatic subjects with nasal polyposis than in healthy controls. Furthermore, increased concentrations of ENO are detected in atopic and nonatopic subjects with nasal polyposis. These results suggest that bronchial inflammation is present in nonasthmatic subjects with nasal polyposis.

Adenosine Monophosphate↗
PubMed2005

Validation of nitrite and nitrate measurements in exhaled breath condensate.

BACKGROUND: Inflammatory markers in exhaled breath condensate (EBC) are investigated as a non-invasive approach to monitoring of inflammation in the respiratory tract. EBC concentrations of nitrite and nitrate, the stable end products of oxidative metabolism of nitric oxide, are increased in patients with asthma, especially during acute exacerbations. OBJECTIVES: To examine methodological aspects of nitrite and nitrate measurements in EBC such as sample collection, storage and analysis. METHODS: In a randomized study, EBC was collected twice within 1 h (with and without a nose clip) in 20 healthy adults and 20 patients with well-controlled asthma and no symptoms of allergic rhinitis. Nitrite and nitrate were assayed by ionex chromatography and fluorimetrically after derivatization with diaminonaphthalene. RESULTS: The geometric mean [exp (mean +/- SD)] EBC levels of nitrite and nitrate in healthy subjects [4.3 (3.0-6.1) and 11.0 (5.3-22.7) micromol/l] and patients [4.6 (2.6-7.3) and 8.7 (3.2-23.8) micromol/l] did not differ (p = 0.13). Wearing a nose clip (p = 0.3) did not influence nitrite and nitrate concentrations. The mean intra-subject %CVs of EBC concentrations of nitrite were 26 and 21% in healthy subjects and patients, while those of nitrate achieved 49 and 88%, respectively. CONCLUSIONS: Ionex chromatography of nitrite and nitrate requires no sample pretreatment and provides comparable results as a more laborious diaminonaphthalene method. EBC samples should be kept cold (8 degrees C) and analyzed for nitrite and nitrate within 24 h of collection or stored in the freezer and thawed preferably only once. Wearing a nose clip during EBC collection has no influence on nitrite and nitrate concentrations. Short-term repeatability of nitrite and nitrate measurements was worse compared to published data on exhaled nitric oxide.

Adult↗