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.     

Tidal off-line exhaled nitric oxide measurements in a pre-school population

Exhaled nitric oxide (ENO) is used as a non-invasive marker of airway inflammation. The aim of this study was to measure ENO in a pre-school population using a relatively novel method, the off-line tidal breathing method, and to investigate differences in ENO between subjects with different presentations of wheezing. ENO was measured in 129 children (median age 4.4 years, quartiles 4.0-4.8 years) through a mouth mask attached to a two-way valve with an expiratory resistance of 5 cm H(2)0. Mean tidal ENO concentration (tENO) was calculated from triplicate measurements. Mean +/- SEM tENO for 89 control subjects was 13+/-0.4 ppb (95%CI 11.8-13.7 ppb); this level was significantly different from tENO in 15 children with a history of recurrent wheezing (18.6+/-1.9 ppb; 95%CI 14.5-22.7 ppb; t-test P<0.0001). Mean tENO in 16 children with a single wheezing episode was 11.4+/-1.0 ppb (95%CI 9.2-13.6 ppb) and thus significantly different from the recurrent wheezing group (t-test P=0.0024). CONCLUSION: The off-line tidal breathing method is a feasible and appealing method for measuring exhaled nitric oxide in pre-school children. With this method, higher tidal exhaled nitric oxide levels were found in children with recurrent wheezing.     

Single breath analysis of endogenous nitric oxide in the newborn

Nitric oxide (NO) is found in the exhaled gas of humans immediately after birth. However, variations of endogenous NO concentration during the breathing cycle have not been studied in newborns. We examined 24 newborns without acute respiratory compromise during spontaneous nasal breathing. Gas was sampled from the tip of a thin nasal catheter placed in the hypopharynx. Endogenous NO concentrations measured by chemiluminescence were assigned to the breathing cycle using synchronized CO2 recording. Exhaled NO could reproducibly be measured at 1.9 +/- 0.2 parts per billion (ppb, mean +/- SEM). Autoinhaled nasal NO peaks during regular breathing were 12.0 +/- 1.7 ppb and reached intermittent maxima of 52.2 +/- 5.8 ppb. During regular breathing 6 infants exhibited sudden decreases of nasal NO peaks to periods with <50% amplitude suggesting transient shortage of autoinhaled nasal NO. We conclude that tidal NO analysis can be used to assess upper and lower airway NO production noninvasively during spontaneous breathing in the newborn.     

Exhaled nitric oxide, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis

Exhaled nitric oxide (eNO) levels are correlated with several markers of atopy and inflammatory activity in the airways, but the relationship between eNO and total serum IgE has not been fully elucidated in the context of allergic sensitization. The aim of this study was to investigate the relationship between eNO, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis. eNO levels, lung function, skin prick tests and total serum IgE were determined in 109 children (mean age, 10.4 yr) with mild intermittent asthma and in 41 children (mean age, 10.1 yr) with allergic rhinitis; 25 healthy non-atopic children were recruited as controls. eNO levels (median) were significantly higher in patients with asthma (22.7 p.p.b.) and in those with allergic rhinitis (15.3 p.p.b.) than in healthy controls (5.9 p.p.b.). Children with allergic asthma had higher eNO levels than children with allergic rhinitis. A significant positive correlation was found between eNO and total serum IgE (asthma, r = 0.42, p < 0.0001; allergic rhinitis, r = 0.31, p < 0.01), and between eNO and the number of positive skin prick tests (asthma, r = 0.31, p < 0.0001; allergic rhinitis, r = 0.39, p < 0.01). eNO levels were better correlated with total IgE than with the number of positive skin prick tests. This correlation was independent of allergic sensitization. High total serum IgE represents a specific and predictive marker of eNO increase in children with asthma or allergic rhinitis. This finding adds further support to the hypothesis that increased serum IgE could be a marker itself of airway inflammation in patients with allergic disease.     

Flow dependency and off-line measurement of exhaled NO in children

Levels of exhaled nitric oxide (eNO) are flow-dependent, and the choice of an optimal flow rate for off-line and on-line eNO measurement has raised much debate. Recently, a flow rate of 50 ml/s was recommended, but children younger than 5–6 years are not capable of stabilizing their expiratory flow at low flow rates. The power of off-line eNO values to discriminate between normal and atopic children was therefore evaluated at different exhalation flow rates. At flow rates of both 8.3 ml/s and of 350 ml/s, children (8–12 years) sensitive to house dust mite have two-fold higher eNO values (p < 0.001) as compared with children lacking such a sensitivity. The power of eNO to discriminate between normal and atopic subjects was similar at the two flow rates (no difference in AUC of receiver operation curves, p = 0.89). All children from 4.5 to 5 years of age (n = 29) could perform a single off-line exhalation manoeuvre at high (>350 ml/s) but not at low (8.3 ml/s) flow rates. At high exhalation flow rate, eNO was 7.1 ± 2.4 (mean ± SD) median, 6.5 p.p.b. with a mean variation coefficient of 5.5%. Depending on their developmental level, about half of the younger children (35–46 months of age) could perform an off-line exhalation manoeuvre at high flow rate with good reproducibility (mean variation coefficient of 6.6%). It is concluded that an exhalation flow rate of 350 ml/s is feasible to determine off-line eNO-values in children from 3.5 years of age, and that this high flow rate does not compromise the power of eNO to detect allergic disease.     

Exhaled nitric oxide in healthy children: Variability and a lack of correlation with atopy

Nitric oxide (NO) is a free radical produced by several lung cells via the enzyme nitric oxide synthetase (NOS) and can be easily measured in exhaled air by chemiluminescence analysis. As the iso-enzyme iNOS may be induced by cytokines and endotoxin, NO is elevated in several chronic inflammatory airway diseases. Prior to using exhaled nitric oxide (eNO) as a non-invasive marker of airway inflammation in daily routine, the role of possibly influencing factors such as age, time of the day, smoking exposure and intra-individual variability have to be clarified. NO concentrations were measured in 107 healthy children aged 4–18 years at an expiratory flow of 184 ml/s. Spirometry and a skin-prick test were performed and a questionnaire on family history of atopy, personal symptoms of atopic disease and smoke exposure was completed. For intra-individual variability nitric oxide was measured in six children three times daily on 6 consecutive days. Median eNO concentration was 5.7 p.p.b., and increased significantly with age but did not vary with gender. No correlation was found between eNO and smoke exposure, positive skin-prick test, FEV ₁, MEF₂₅ and time of the day. There was no circadian rhythm found in the six children measured on 6 consecutive days, but the eNO showed an intra-individual coefficient of variation of 25.9%. With the help of a two-compartment model of the lung the alveolar NO concentration was estimated to be 4.1 p.p.b and was shown to be constant with age, whereas the airway part of NO steadily increased with age. When comparing eNO values with standardized measurement techniques, the age of the children and the large intra-subject coefficient of variation have to be taken into account, whereas in healthy children subject-specific factors such as atopic history, gender and skin test reactivity did not affect eNO measurement.     

Methodological aspects of exhaled nitric oxide measurements in infants

Guidelines for the measurement of fractional exhaled nitric oxide (FE(NO)) recommend refraining from lung function tests (LFT) and certain foods and beverages before performing FE(NO) measurements, as they may lead to transiently altered FE(NO) levels. Little is known of such factors in infants. The aim of the present study was to evaluate whether forced expiratory maneuvers, sedation, nasal contamination, and breastfeeding affect FE(NO) values in infants. FE(NO) was measured off-line during tidal breathing by means of a facemask covering nose and mouth. FE(NO) measurements were performed in 45 sedated infants (mean age 12.1 months) who underwent LFT because of airway diseases and in 83 unsedated healthy infants (mean age 4.3 months). In infants with airway diseases, no difference was found in FE(NO) values before and 5 min after LFT (n = 19 infants, p = 0.7) and FE(NO) values before sedation did not differ from FE(NO) values during sedation (n = 10 infants, p = 0.2).Oral FE(NO) values were significantly lower than mixed (nasal + oral) FE(NO) (n = 42 infants, p < 0.001). FE(NO) values before and 5 min after breastfeeding were not different (n = 11 healthy infants, p = 0.57). The short-term reproducibility in healthy infants (n = 54) was satisfactory (intraclass correlation coefficient = 0.94). We conclude that, in infants with airway diseases, LFT prior to FE(NO) measurement did not influence FE(NO) values and FE(NO) values did not change after sedation. Oral FE(NO) values were significantly lower than mixed (oral + nasal) FE(NO), and breastfeeding did not influence FE(NO). Short-term reproducibility in awake healthy infants was good.     

Effects of montelukast on symptoms and eNO in children with mild to moderate asthma

BACKGROUND: Asthma is a chronic inflammatory airway disease. Exhaled nitric oxide (eNO) is a marker reflecting airway inflammation. This study was conducted to investigate whether montelukast, a leukotriene receptor antagonist, could be used for the management of asthma and how fast the montelukast sodium decreased airway inflammation as demonstrated by eNO levels. METHODS: Twenty children aged 6-14 years (mean age: 9.2 +/- 2.4 years; mean weight 30 +/- 4.6 kg) with mild to moderate asthma were recruited for the study. They received montelukast plus an inhaled short-acting beta2 agonist as open and uncontrolled therapy. Asthma score (AS) and peak expiratory flow rate (PEFR) and eNO concentrations were measured at pretreatment (0 week) and post-treatment (1 and 2 weeks) as well as 2 weeks after withdrawal of therapy. RESULTS: In one week, the eNO levels (33.3 +/- 15.5 p.p.b. vs 14.8 +/- 8.6 p.p.b.; P < 0.05), and AS (4.2 +/- 1.3 vs 1.8 +/- 1.3; P < 0.05) decreased rapidly, and PEFR (206.9 +/- 69.7 L/min vs 236.2 +/- 69.8 L/min; P < 0.05) increased. Concurrent beta2 agonist use decreased from a mean +/- SD of 2.2 +/- 0.4-1.3 +/- 0.3 puffs per weeks (P < 0.05). After the withdrawal of treatment for 2 weeks, the eNO levels (29.2 +/- 16.1 p.p.b) rebounded again, although the improvements in AS (1.1 +/- 1.3) and PEFR (245.0 +/- 91.3 L/min) persisted. CONCLUSION: Oral montelukast sodium treatment of these children with mild to moderate asthma effectively improved asthmatic symptoms and suppressed airway inflammation in 1 week, suggesting that this leukotriene antagonist combined with short-acting beta2 agonists may provide effective treatment option in mild to moderate childhood asthma. Larger, controlled, and double-blinded studies are needed to confirm these preliminary open uncontrolled observations.     

Additive effect of eosinophilia and atopy on exhaled nitric oxide levels in children with or without a history of respiratory symptoms

Although atopy and blood eosinophilia both influence exhaled nitric oxide (eNO) measurements, no study has quantified their single or combined effect. We assessed the combined effect of atopy and blood eosinophilia on eNO in unselected schoolchildren. In 356 schoolchildren (boys/girls: 168/188) aged 9.0-11.5 yr, we determined eNO, total serum IgE, blood eosinophil counts and did skin prick tests (SPT) and spirometry. Parents completed a questionnaire on their children's current or past respiratory symptoms. Atopy was defined by a SPT >3 mm and eosinophilia by a blood cell count above the 80th percentile (>310 cells/ml). eNO levels were about twofold higher in atopic-eosinophilic subjects than in atopic subjects with low blood eosinophils [24.3 p.p.b. (parts per billion) vs. 14.1 p.p.b.] and than non-atopic subjects with high or low blood eosinophils (24.3 p.p.b. vs. 12.2 p.p.b. and 10.9 p.p.b.) (p <0.001 for both comparisons). The additive effect of atopy and high eosinophil count on eNO levels remained unchanged when subjects were analyzed separately by sex or by a positive history of wheeze (n=60), respiratory symptoms other than wheeze (n=107) or without respiratory symptoms (n=189). The frequency of sensitization to Dermatophagoides (Dpt or Dpf) was similar in atopic children with and without eosinophilia (66.2% and 67.4%, respectively); eosinophilia significantly increased eNO levels in Dp-sensitized children as well in children sensitized to other allergens. In a multiple linear regression analysis, eNO levels were mainly explained by the sum of positive SPT wheals and a high blood eosinophil count (t=4.8 and 4.3, p=0.000), but also by the presence of respiratory symptoms (especially wheeze) and male sex (t=2.6 and 2.0, p=0.009 and 0.045, respectively). Measuring eNO could be a simple, non-invasive method for identifying subjects at risk of asthma in unselected school populations.     

A methodology for measurements of nasal nitric oxide in children under 5 yr

Measurements of nasal nitric oxide (nNO) may give insight into respiratory conditions in children aged under 5 yr but no methodology has been described for this age-group. The present study aimed to establish the methodology and reproducibility for measuring nNO during tidal breathing in young children and to relate nNO to allergic conditions. Children and siblings aged under 5 yr attending hospital clinics were enrolled. On-line nNO measurements were obtained during tidal breathing using a chemiluminescence analyser. To establish our methodology, nNO was measured over 3, 5 or 10 s NO plateaus and nNO was also measured from left and right nostrils. nNO was then compared between children with and without allergic conditions. The reproducibility of nNO measurements over 24 h was studied in a separate group of children. Eighty-three children participated in the methodological part of the study and nNO was successfully measured in 57 (69%), mean (s.d.) age 3.4 (1.1) years, 14 with allergic conditions. Neither NO plateau duration nor choice of nostril influenced nNO values. The mean (s.d.) nNO for non-atopic children was 208 (103) parts per billion (ppb) and for atopic children was 284 (122), p = 0.032. Nasal NO values were not related to ambient NO, gender and passive smoke exposure; there was a non-significant trend for nNO to be positively related to age. Nasal NO measurements were reproducible in the 21 children tested, mean difference 9.6 ppb (limits of agreement-127, 146). We report a methodology for nNO measurement in young children. Further work is now required to establish the clinical utility of nNO in this age-group.     

Exhaled nitric oxide in asthmatic and non-asthmatic children: Influence of type of allergen sensitization and exposure to tobacco smoke

Asthmatic bronchial inflammation is associated with increased nitric oxide concentrations in exhaled air (eNO). Recent data suggest that this effect arises from atopy. Our aim in this study was to find out whether atopy and sensitization to particular allergens influences eNO levels. A total of 213 subjects (41 asthmatics and 172 controls) (96 boys and 117 girls, 7.3–14 years of age) were studied. Parents completed a questionnaire that sought information on their children's respiratory symptoms and exposure to tobacco smoke. Subjects underwent skin‐prick tests for the following common allergens: Dermatophagoides pteronyssinus (Dpt), cat fur, Aspergillus fumigatus, Alternaria tenuis, mixed grass, mixed tree pollen, Parietaria officinalis, egg, and cow's milk. eNO was collected in 1‐l mylar bags (exhaled pressure 10 cmH₂O, flow 58 ml/s) and analyzed by using chemiluminescence. Atopic and non‐atopic children without a history of chronic respiratory symptoms had a similar geometric mean eNO (atopics, n = 28, 11.2 p.p.b.; non‐atopics, n = 96, 10.0 p.p.b.; mean ratio 1.1, 95% confidence interval [CI]: 0.7–1.6). Conversely, atopic asthmatic subjects had significantly higher eNO values than non‐atopic asthmatic subjects (atopics, n = 25, 24.8 p.p.b.; non‐atopics, n = 16, 11.4 p.p.b.; mean ratio 2.2, 95% CI: 1.2–3.9, p= 0.000). In children with rhinitis alone (n = 15) and those with lower respiratory symptoms other than asthma (n = 33), eNO increased slightly, but not significantly, with atopy. eNO levels correlated significantly with Dpt wheal size (r = 0.51) as well with the wheal size for cat, mixed grass, and Parietaria officinalis (r = 0.30–0.29), and with the sum of all wheals (r = 0.47) (p= 0.000). Subjects sensitized only for Dpt (but not those subjects sensitized only for grass pollen or other allergens) showed significantly higher eNO levels than non‐atopic subjects (16.4 p.p.b. vs. 10.2 p.p.b., mean ratio 1.6, 95% CI: 1.1–2.3, p= 0.002). In asthmatic subjects, Dpt sensitization markedly increased eNO levels (Dpt‐sensitized subjects: 28.0 p.p.b.; Dpt‐unsensitized subjects: 12.2 p.p.b.; mean ratio 2.3, 95% CI: 1.5–3.5, p= 0.000). Non‐asthmatic Dpt‐sensitized subjects also had significantly higher eNO values than non‐asthmatic, non‐Dpt‐sensitized subjects (14.2 p.p.b. vs. 10.1 p.p.b.; mean ratio 1.4, 95% CI: 1.1–1.9, p= 0.008). No difference was found between eNO levels in asthmatic subjects and control subjects exposed or unexposed to tobacco smoke. In conclusion, eNO concentrations are high in atopic asthmatic children and particularly high in atopic asthmatics who are sensitized to house‐dust mite allergen.     

Exhaled nitric oxide differentiates airway diseases in the first two years of life

Fractional exhaled nitric oxide (FE(NO)) levels are increased in children and adults with asthma, whereas low levels have been found in cystic fibrosis and primary ciliary dyskinesia. The aim of this study was to investigate whether FE(NO) measurements could distinguish between children below the age of 2 with different airway diseases. FE(NO) measurements were performed in 118 infants aged between 4.6 and 25.2 mo: 74 infants with recurrent wheezing (RW), 24 with bronchopulmonary dysplasia (BPD), and 20 with cystic fibrosis (CF). FE(NO) was measured also in 100 healthy controls aged between 1.1 and 7.7 mo. Geometric mean (95% confidence interval) FE(NO) values were 10.4 (9.1-12.0) parts per billion (ppb) in healthy infants, 18.6 (15.6-22.2) ppb in wheezy infants, 11.7 (8.2-16.8) ppb in BPD infants and 5.9 (3.4-10.1) ppb in CF infants. FE(NO) in wheezers was higher than in controls, BPD, and CF (p = 0.009, p = 0.038, and p < 0.001, respectively). Atopic wheezers showed higher FE(NO) than nonatopic wheezers (p = 0.04). CF infants had lower FE(NO) than healthy controls and BPD infants (p = 0.003 and p = 0.043, respectively). FE(NO) values in BPD and control infants were not different. We conclude that FE(NO) is helpful to differentiate various airway diseases already in the first 2 y of life.     

百日咳样咳嗽婴幼儿的肺功能特点

目的 探讨不同病原体感染的百日咳样咳嗽患儿的肺功能特点。方法 收集95例百日咳样咳嗽住院婴幼儿病原学及潮气呼吸肺功能检测资料,并与67例健康婴幼儿（正常对照组）潮气呼吸肺功能检测资料比较。百日咳样咳嗽患儿按病原体种类不同分为百日咳组（17例）、病毒感染组（23例）、结核感染组（6例）、支原体感染组（9例）、其他细菌感染组（8例）以及病原体未明组（32例）。结果 95例百日咳样咳嗽患儿中,轻度阻塞性通气功能障碍15例（16%）,中度阻塞性通气功能障碍30例（32%）,重度阻塞性通气功能障碍22例（23%）。与正常对照组相比,百日咳样咳嗽患儿吸呼比（tI/tE）、达峰时间比（tPF% tE）和达峰容积比（vPF% vE）均显著降低（均P < 0.05）。结核感染组和支原体感染组潮气量均显著低于正常对照组（均P < 0.05）。除结核感染组外,各病原体感染组tPF% tE和vPF% vE显著低于正常对照组（均P < 0.05）。百日咳组tPF% tE和vPF% vE显著低于其他病原体感染组（均P < 0.05）。结论 百日咳样咳嗽患儿肺功能多有异常;百日咳杆菌感染的患儿肺功能损害最重;潮气呼吸肺功能测试可为百日咳样咳嗽患儿病原体分析提供一定的参考依据。     

Consistently high levels of exhaled nitric oxide in children with asthma

Background: Exhaled nitric oxide (eNO) levels in children are unstable because they are regulated by many potent factors. The purpose of the current study was to evaluate the reliability of eNO levels between a long interval and other lung functions in normal and asthmatic children. Methods: Eighty‐three elementary school children (aged 11–12 years; male : female, 39 : 44) participated in this study. Lung function, airway resistance and eNO levels were measured twice: the first measurement was in autumn 2007, and the second was one year later. Results: There were 62 non‐asthmatic control children (male : female, 31 : 31) and 21 asthmatic children (male : female, 8 : 13). In both the first and the second examination, the levels of eNO in children with asthma were higher than those in children without asthma. The parameters of lung function and the respiratory resistance in children without asthma showed a good correlation between the results of the first and second examinations. The eNO level in non‐asthmatic children showed a good correlation between the two. On the other hand, the peripheral airway parameters of lung function and the respiratory resistance in children with asthma were not correlated between the first and the second examinations. The eNO level in these patients was well correlated between the two examinations. Conclusions: These data suggest that the eNO level showed good reproducibility in children with and without asthma. The eNO level is therefore considered to be a useful marker for reproducibly evaluating a subject's airway condition.     

Faecal elastase-1 test is superior to faecal lipase test in the assessment of exocrine pancreatic function in cystic fibrosis

BACKGROUND AND AIMS: Direct tests are characterized by the highest sensitivity and specificity. However, their practical use, especially in children, is limited. Among the indirect tests, the highest sensitivity and specificity was documented for faecal elastase-1 test, yet the value of faecal lipase test in cystic fibrosis (CF) has not been defined. Therefore, the aim of the present study was to compare the sensitivity and the specificity of the faecal lipase test to the faecal elastase-1 test in the assessment of exocrine pancreatic function in children with CF. METHODS: The study comprised 90 CF patients and 95 healthy subjects (HS). In all subjects, faecal elastase-1 concentrations (ELISA) and lipase activities (ELISA) were measured. The presence of pancreatic insufficiency was documented by the determination of faecal fat excretion in 78 pancreatic insufficient and by the secretin-cholecystokinin test in 12 CF patients without steatorrhoea. Sensitivity and specificity of the faecal elastase-1 test and faecal lipase test were analysed and, in 50 HS, sample-to-sample and day-to-day variations were determined. RESULTS: With cut-off levels providing the same specificity for both tests (95.8%), the sensitivity of the faecal elastase-1 test (91.1%) was significantly higher (p < 0.0036) than that of the faecal lipase test (76.7%). Sample-to-sample (mean +/- SEM: 13.2 +/- 1.2% vs 23.4 +/- 2.2%) and day-to-day variations (mean +/- SEM: 16.3 +/- 1.2% vs 32.5 +/- 2.6%) were significantly lower (p < 0.0001) for elastase-1 than for lipase measurements. CONCLUSION: Among indirect tests, faecal elastase-1 test is superior to faecal lipase test in the assessment of exocrine pancreatic function in cystic fibrosis.     

Exhaled carbon monoxide in childhood asthma.

OBJECTIVES: Oxidative stress and inflammation induce the expression of heme oxygenase-1, which produces carbon monoxide (CO), and nitric oxide synthase, which produces nitric oxide (NO). Exhaled CO and NO levels are elevated in asthmatic patients and are decreased after corticosteroid treatment, suggesting that they may be useful as noninvasive markers of airway inflammation. STUDY DESIGN: We measured forced expiratory volume in the first second, PC(20), and exhaled CO and NO levels in 29 children (18 boys, mean age 11.5 +/- 0.53 years) with asthma of different severity and 40 nonsmoking children without asthma (21 boys, mean age 8.1 +/- 0.35 years). We also studied whether upper respiratory tract infections were associated with elevated exhaled CO. RESULTS: Exhaled CO levels (ppm) were significantly higher (2.17 +/- 0.21) in children with persistent asthma compared with those in children with infrequent episodic asthma (1.39 +/- 0.18, P <.05) and healthy children (1.01 +/- 0.12, P <.001). The CO levels in children with infrequent episodic asthma and the normal control group, however, were not different. In contrast, exhaled NO levels (ppb) were higher in children with persistent asthma (24.2 +/- 5.9, P <.001) and infrequent episodic asthma (14.5 +/- 3.73, P <.05) than in normal subjects (5.1 +/- 0.24), but no significant difference was seen between the 2 asthmatic groups. In healthy children with upper respiratory tract infections (n = 12), exhaled CO concentrations were significantly elevated (2.16 +/- 0.33) during the acute symptomatic phase. No correlation was found between exhaled CO and forced expiratory volume in the first second or PC(20). CONCLUSIONS: Noninvasive measurement of exhaled CO may provide complementary data for assessment of asthma control in children. However, elevated CO levels are nonspecific and may be found in association with an acute viral illness.     

健康儿童呼出气体一氧化氮水平及其与肺功能相关性研究

目的 测定健康儿童呼出气体一氧化氮(eNO)浓度及其与肺功能的相关性.方法 随机测定100名7～8岁健康儿童(男53名;7岁43名)eNO及肺功能,采用SAS(8.2版)软件进行秩相关分析.结果 受试儿童eNO水平[中位数(四分位数间距)为8×10-9[(6～11)×10-9],其中男8×10-9[(6～11)×10-9],女8×10-9[(6～11)×10-9].eNO与肺功能无相关性(复相关系数r=0.22,P=0.32).eNO与身高、体质量有明显的相关性(r=0.22,P=0.03;r=0.23,P=0.02).结论 健康儿童eNO与肺功能无相关性.eNO与肺功能联合检测可全面认识气道炎症和气道高反应性.     

Exhaled nitric oxide in chronically ventilated preterm infants

Exhaled nitric oxide (eNO) levels were measured in eight ventilated infants, mean gestational age 25.8 (SD 1.7) weeks and postnatal age 55 (SD 39) days, before and after three days of dexamethasone treatment. The eNO levels fell from a mean of 6.5 (SD 3.4) to 4.2 (SD 2.6) parts per billion (p = 0.031) and the mean supplementary oxygen levels from 62% to 45% (p = 0.0078).     

Endogenous nitric oxide production in the airways of preterm and term infants

Few studies have measured endogenous nitric oxide exhaled from the respiratory system of newborn infants. We measured exhaled nitric oxide (eNO) in the first 48 h of life in 24 (13 preterm, 11 term) spontaneously breathing (online method) newborns using a chemoluminescence analyzer. There was a significant difference in the eNO concentration between term and preterm healthy infants in the first 2 days of life (repeated measures analysis of variance, p < 0.05). In term infants there is a peak eNO production in the first hours of life, suggesting a potential role in postnatal adaptation, while in preterm infants eNO production is almost absent at birth, and then gradually increases.     

Exhaled nitric oxide measurements in childhood asthma: comparison of two sampling techniques

Nitric oxide (NO) is being increasingly used to assess airway inflammation in childhood. The method recommended by the American Thoracic Society workshop is for a prolonged expiration against a resistance. However, this is very difficult to apply in young children. As a result there have been a number of studies in which mixed expired gas has been collected and analyzed for NO content as this requires very little cooperation. This method has, however, yet to be fully validated. The aims of this study were to compare the two sampling techniques of exhaled NO concentrations in asthmatic and healthy children and to assess the correlation between NO levels and spirometry values in asthmatic children We studied 25 control children, mean age 11.5 y, and 20 asthmatics, mean age 12 y. The exhaled NO was sampled using both the single breath technique (SB) and by measuring the NO content in mixed expired air after 1 min tidal breathing (ME). Forced expiratory volume in 1 s (FEV(1)) and expiratory flow rates at 25%, 50%, and 75% of vital capacity (FEF(25), FEF(50), FEF(75), respectively) were measured by compact II spirometer (best of three) in the 20 asthmatic children. The NO level was significantly higher in the asthmatics versus the control children when measured by SB (p = 0.0015) but not when measured by ME (p = 0.1913). The NO results measured by SB were significantly higher than ME results in the asthmatic children (p = 0.008). The NO levels were negatively correlated to FEV(1), FEF(25), FEF(50), and FEV(75) when measured by SB (p < 0.02) but not when measured by ME. The SB but not the ME method for measuring expired NO discriminates between asthmatic and control children and correlates well with the degree of airway obstruction. The use of the ME technique remains unproven.