Orally exhaled nitric oxide levels are related to the degree of blood eosinophilia in atopic children with mild-intermittent asthma

Increased levels of nitric oxide have been found in expired air of patients with asthma, and these are thought to be related to the airway inflammatory events that characterize this disorder. Since, in adults, bronchial inflammatory changes are present even in mild disease, the present study was designed to evaluate whether a significant proportion of children with mild-intermittent asthma could have increased exhaled air NO concentrations. Twenty-two atopic children (aged 11.1+/-0.8 yrs) with mild-intermittent asthma, treated only with inhaled beta2-adrenoreceptor agonists on demand and 22 age-matched controls were studied. NO concentrations in orally exhaled air, measured by chemiluminescence, were significantly higher in asthmatics, as compared to controls (19.4+/-3.3 parts per billion (ppb) and 4.0+/-0.5 ppb, respectively; p<0.01). Interestingly, 14 out of 22 asthmatic children had NO levels >8.8 ppb (i.e. >2 standard deviations of the mean in controls). In asthmatic patients, but not in control subjects, statistically significant correlations were found between exhaled NO levels and absolute number or percentage of blood eosinophils (r=0.63 and 0.56, respectively; p<0.01, each comparison). In contrast, exhaled NO levels were not correlated with forced expiratory volume in one second (FEV1) or forced expiratory flows at 25-75% of vital capacity (FEF25-75%) or forced vital capacity (FVC), either in control subjects, or in asthmatic patients (p>0.1, each correlation). These results suggest that a significant proportion of children with mild-intermittent asthma may have airway inflammation, as shown by the presence of elevated levels of nitric oxide in the exhaled air. The clinical relevance of this observation remains to be established.

Dissociation between exhaled nitric oxide and hyperresponsiveness in children with mild intermittent asthma

BACKGROUND

Bronchial hyperresponsiveness and airway inflammation are distinctive features of asthma. Evaluation of nitric oxide (NO) levels in expired air have been proposed as a reliable method for assessing the airway inflammatory events in asthmatic subjects. A study was undertaken to evaluate whether airway hyperresponsiveness is related to levels of exhaled NO.

METHODS

Thirty two steroid-naive atopic children with mild intermittent asthma of mean (SD) age 11.8 (2.3) years and 28 age matched healthy controls were studied to investigate whether baseline lung function or airway hyperresponsiveness is related to levels of exhaled NO. Airway responsiveness was assessed as the dose of methacholine causing a 20% decrease in forced expiratory volume in one second (FEV(1)) from control (PD(20) methacholine) and exhaled NO levels were measured by chemiluminescence analysis of exhaled air.

RESULTS

At baseline asthmatic children had significantly higher NO levels than controls (mean difference 25.87 ppb (95% CI 18.91 to 32.83); p<0.0001) but there were no significant differences in lung function parameters (forced vital capacity (FVC), FEV(1) (% pred), and forced expiratory flows at 25-75% of vital capacity (FEF(25-75%))). In the asthmatic group exhaled NO levels were not significantly correlated with baseline lung function values or PD(20) methacholine.

CONCLUSIONS

These results suggest that levels of exhaled NO are not accurate predictors of the degree of airway responsiveness to inhaled methacholine in children with mild intermittent asthma.

Exhaled nitric oxide levels in non-allergic and allergic mono- or polysensitised children with asthma

BACKGROUND

Increased fractional exhaled NO concentrations (FENO) and blood/tissue eosinophilia are frequently reported in allergic children with mild asthma and are thought to reflect the intensity of the inflammation characterising the disease. The aim of this study was to investigate possible differences in FENO levels or in the intensity of the blood eosinophilia in allergic and non-allergic asthmatic children.

METHODS

112 children with stable, mild, intermittent asthma with a positive bronchial challenge to methacholine were consecutively enrolled in the study; 56 were skin prick test and RAST negative (non-sensitised) while 56 were sensitised to house dust mites (23 only to house dust mites (monosensitised) and 33 were sensitised to mites and at least another class of allergens (pollens, pet danders, or moulds)). Nineteen sex and age matched healthy children formed a control group.

RESULTS

Compared with non-allergic patients, allergic children had a significantly higher rate of blood eosinophilia (p=0.0001) with no differences between mono- and polysensitised individuals. Forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), forced expiratory flow at 25-75% of vital capacity (FEF(25-75%)), and the degree of bronchial reactivity to methacholine were similar in non-atopic and atopic children, with no differences between mono- and polysensitised individuals. FENO levels measured by chemiluminescence analyser were higher in asthmatic children (15.9 (14.3) ppb) than in the control group (7.6 (1.6) ppb, p=0.04) and higher in allergic patients (23.9 (2.1) ppb) than in non-allergic patients (7.9 (0.8) ppb, p=0.0001), but there were no differences between mono- and polysensitised individuals (p>0.1). Significant correlations between blood eosinophilia and FENO levels were seen only in allergic (r=0.35, p<0.01) and in polysensitised individuals (r=0.45, p<0.05).

CONCLUSIONS

In children with mild asthma, a similar degree of functional disease severity may be associated with a higher inflammatory component in allergic than in non-allergic subjects.

LFA-1 expression by blood eosinophils is increased in atopic asthmatic children and is involved in eosinophil locomotion

Allergic asthma is characterized by eosinophil migration in the airways, which is strictly dependent on the expression of adhesion molecules. This study investigated whether the expression of adhesion molecules on eosinophils is increased and associated with disease activity in allergic asthma. Twenty atopic asthmatic (AA) subjects and nine controls were studied and the expression of lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18), Mac-1 (CD11b/CD18) and very late antigen-4 (VLA-4; CD49d/CD29) on blood eosinophils was evaluated by specific monoclonal antibody (Mab) staining and flow-cytometric analysis. Compared with controls, eosinophils from AA showed increased expression of LFA-1 (p<0.005), but not of Mac-1 or VLA-4 (p>0.1). In addition, LFA-1 expression correlated positively with blood eosinophil number (r=0.792, p<0.05), while no correlations were observed between Mac-1 or VLA-4 expression and blood eosinophil number. The migration of eosinophils through human umbilical vein endothelial cells with or without anti-LFA-1, Mac-1 and VLA-4-blocking Mab was studied. Compared with controls, eosinophils from AA showed increased migration toward C5a (p<0.01). Cell migration was totally inhibited by preincubating eosinophils with anti-LFA-1 (p<0.05), while anti-Mac-1 had no effect (p>0.1). Thus, the expression of lymphocyte function-associated antigen-1 by blood eosinophils is increased in atopic asthmatics and seems to modulate the enhanced eosinophil migration observed in allergic asthma.

Stimulation of eosinophil IgE low-affinity receptor leads to increased adhesion molecule expression and cell migration

Immunoglobulin binding on eosinophil surface receptors results in activation of these cells. Evaluating blood eosinophils from atopic subjects, it was investigated whether ligation of immunoglobulin E low-affinity receptor (FcepsilonRII/ CD23) with specific monoclonal antibodies (Mabs) resulted in enhanced eosinophil migration and adhesion molecule expression. Eosinophils from 20 subjects with allergic asthma (atopic individuals) and nine nonatopic normal individuals (controls) were purified using Percoll gradients. The effect of antihuman CD23 Mabs on: 1) eosinophil migration through human umbilical vein endothelial cells (HUVECs); and 2) eosinophil expression of the adhesion molecules leukocyte function-associated antigen-1 (LFA-1, CD11a/CD18), macrophage antigen-1 (Mac-1, CD11b/CD18) and very late activation antigen-1 (VLA-4, CD49d/CD29) was evaluated by specific Mab staining and flow cytometric analysis. As compared to controls, freshly isolated eosinophils from atopic individuals showed enhanced migration through HUVECs (p<0.05) and increased LFA-1 expression (p<0.01), but similar Mac-1 and VLA-4 expression (p>0.1 for both). In both controls and atopic individuals, eosinophil incubation with antihuman CD23 Mabs induced a dose-dependent increase in cell migration through HUVECs, significant at antihuman CD23 Mab concentrations of 5 microg x mL(-1) (p>0.05 for all). Similarly, incubation of the cells with antihuman CD23 Mabs induced dose-dependent upregulation of LFA-1 and Mac-1 expression, whereas no changes in VLA-4 expression were observed (p>0.1). Finally, the enhanced eosinophil migration induced by antihuman CD23 Mab stimulation was significantly inhibited by antihuman LFA-1 (84+/-14% (mean+/-SEM); p<0.01) and VLA-4 Mabs (47+/-15%; p<0.05) but not by antihuman Mac-1 Mabs (p>0.1). In both atopic and control subjects, immunoglobulin E, low-affinity receptor stimulation induces functional changes in eosinophils characterized by increased eosinophil migration associated with enhanced late function antigen-1 and Mac-1 expression.

Time-dependent changes in orally exhaled nitric oxide and pulmonary functions induced by inhaled corticosteroids in childhood asthma

Exhaled nitric oxide levels are elevated in asthmatic children and decrease after inhaled steroid treatment. We evaluated the time-dependent changes in fractional exhaled nitric oxide concentration (FENO) and pulmonary function parameters following inhaled steroid therapy. Thirty-nine steroid-naive atopic patients (age 11.92+/-0.48 years) with mild intermittent asthma and 22 age-matched healthy controls were enrolled in the study; pulmonary functions and FE(NO) levels were measured. Low doses of inhaled steroids were prescribed to all asthmatic patients who were reevaluated in a second visit (between 10 and 40 days after the beginning of the treatment). At the enrolment, asthmatic patients had similar forced expiratory volume in 1 sec (FEV1) and forced vital capacity (FVC) values (p > 0.05) but reduced forced expiratory flows at 25-75% of the vital capacity (FEF(25-75%)) values, as compared to controls (p < 0.05). In addition, FE(NO) levels were significantly higher in asthmatics with respect to control subjects (30.8+/-3.0 and 4.0+/-0.5 ppb, respectively; p < 0.01). All asthmatics had FE(NO) levels higher than 8.8 ppb (i.e., > 2 standard deviations of the mean in controls). After steroid treatment, patients showed significant improvement of FEV1, FVC, and FEF(25-75%) (p = 0.0001; each comparison) and a reduction of FE(NO) levels (p = 0.0001). A weak significant correlation was found between percent decrease in FE(NO) levels and percent increase in FEV1 (r = 0.33, p = 0.04) or in FEF(25-75%) (r = 0.4, p = 0.01) after treatment. When changes in FE(NO) levels and in pulmonary function parameters were corrected for days of treatment, significant correlations were still present between percent decrease in FE(NO) levels and percent increase in FEV1 (r = 0.57, p = 0.0004) or percent increase in FEF(25-75%) (r = 0.45, p = 0.006). Sixteen of the 39 asthmatic patients were evaluated on two occasions after the beginning of treatment, at days 10 and 40. The significant reduction in FE(NO) levels (p < 0.01) and the significant increase in FEV1 and FEF(25-75%) values observed (p < 0.05) after 10 days did not further improve at day 40. These data show that it is possible to demonstrate early effects of low-dose inhaled steroids in asthmatic children using objective measurements of airway caliber and inflammation.

In allergic asthma experimental exposure to allergens is associated with depletion of blood eosinophils overexpressing LFA-1

BACKGROUND

In atopic individuals, exposure to allergens is followed by recruitment of blood eosinophils in the target tissue. We investigated whether allergen inhalation challenge could result in depletion of blood eosinophils overexpressing adhesion molecules involved in eosinophil migration.

METHODS

Blood eosinophils were isolated from seven atopic asthmatic patients and seven control subjects and the "at baseline" expression of lymphocyte function-associated antigen-1 (LFA-1), macrophage antigen-1 (Mac-1) and very late antigen-4 (VLA-4) was assessed by monoclonal antibody staining and flow cytometry analysis. Asthmatic patients underwent allergen challenge and the expression of LFA-1, Mac-1 and VLA-4 by blood eosinophils was again evaluated 3 h and 24 h after allergen challenge.

RESULTS

As compared to controls, eosinophils from atopics showed at baseline enhanced LFA-1 expression (P=0.0012), but similar Mac-1 or VLA-4 expression (P > 0.1, each comparison). In atopics, the percentage and absolute number of blood eosinophils were significantly decreased 3 h after allergen challenge (P=0.001 and P=0.022, respectively) but returned to similar values to prechallenge values after an additional 21 h (P > 0.1). Allergen challenge was also followed by a significant decrease in LFA-1 expression by eosinophils, at 3 h (P=0.002) and at 24 h (P=0.038), while no changes in Mac-1 and VLA-4 were observed. A significant correlation between postchallenge decrease in LFA-1 expression and in blood eosinophilia, both expressed as percentage (r=0.88; P < 0.01) or absolute number (r=0.87; P < 0.01) was demonstrated at 3 h (r=0.88; P < 0.01) but not at 24 h (r=0.64, P > 0.05 and r=0.11; P > 0.05, respectively).

CONCLUSION

In allergic asthma, an early recruitment of blood eosinophils overexpressing LFA-1 occurs in the first hours after allergen challenge.

Modulation of HLA-DR antigen and ICAM-1 molecule expression on airway epithelial cells by sodium nedocromil

OBJECTIVE

To test in vitro and in vivo the hypothesis that sodium nedocromil could modulate the expression of surface molecules on airway epithelial cells.

METHODS

Human bronchial epithelial cells, obtained from surgically resected bronchi, were cultured and stimulated with recombinant IFN-gamma in the presence of sodium nedocromil. The intensity of the expression of surface molecules HLA-DR and ICAM-1 molecules on bronchial epithelial cells in vitro, was quantified by specific antibody staining and flow-cytometry analysis. Furthermore, we studied the effect of the drug on airway inflammation in vivo and on allergic rhinitis patients sensitized to house dust mites. Nasal epithelial cells were collected by brushing, at baseline and 2 to 3 weeks after treatment with sodium nedocromil. The expression of HLA-DR and ICAM-1 molecules was measured by flow-cytometry, and the proportions of neutrophils and eosinophils "contaminating" the epithelial cells evaluated by light microscopy examination of nasal brushings.

RESULTS

The enhanced HLA-DR and ICAM-1 expression, induced by IFN-gamma, was effectively downregulated, in a dose-dependent manner, by sodium nedocromil. At all the concentrations tested (10(-9) to 10(-4) M), the inhibitory activity of the drug was stronger on HLA-DR than on ICAM-1 expression (P<.05, all comparisons). As compared with healthy subjects, patients with allergic rhinitis had a higher expression of HLA-DR (P<.05) but not of ICAM-1 molecules (P>.05) on nasal epithelial cells, and higher proportions of nasal eosinophils (P<.05). Treatment with sodium nedocromil downregulated the expression of HLA-DR (P<.05), but not of ICAM-1 (P>.05), and induced a mild, but not statistically significant, decrease of nasal eosinophilia (P>.05).

CONCLUSION

These data demonstrate that the antiinflammatory activity of sodium nedocromil may include modulation of surface molecule expression on airway epithelial cells.

A rapid response magnitude scale for timely assessment of the high frequency seismic radiation

In this work the scaling of seismic moment (M0) and radiated energy (Er) is investigated for almost 800 earthquakes of the 2016-17 Amatrice-Norcia sequences in Italy, ranging in moment magnitude (Mw) from 2.5 to 6.5. The analysis of the M0-to-Er scaling highlights a breaking of the source self-similarity, with higher stress drops for larger events. Our results show the limitation of using M0, and in turn Mw, to capture the variability of the high frequency ground motion. Since the observed seismicity does not agree with the assumptions on stress drop in the definition of Mw, we exploit the availability of both Er and M0 to modify the definition of Mw and introduce a rapid response magnitude (Mr), which accounts for the dynamic properties of rupture. The new Mr scale allows us to improve the prediction of the earthquake shaking potential, as shown by the reduction of the between-event residuals computed for the peak ground velocity. The procedure we propose is therefore a significant step towards a quick assessment of earthquakes damage potential and timely implementation of emergency plans.

Blood eosinophil counts and arterial oxygen tension in acute asthma

OBJECTIVE

To investigate whether during acute asthma episodes a decrease in blood eosinophil count could correlate with the severity of the disease.

DESIGN

Prospective study on paediatric asthmatic patients admitted for acute asthma exacerbation between January 1992 and August 1993. All patients were regularly followed up in an outpatient clinic and had had a complete clinical evaluation < 1 month before admission.

SETTING

Pulmonary division of the G Gaslini paediatric research institute, Genoa, Italy.

SUBJECTS

21 asthmatic patients, 59 (SEM 9) months of age, admitted for acute asthma exacerbation. On the basis of clinical evaluation and the results of blood and microbiological tests performed during acute asthma exacerbations, patients were divided into two subgroups: infected (n = 13) and non-infected (n = 8).

RESULTS

All but one of the patients showed a marked decrease in blood eosinophil count during the acute asthma episode, in comparison with recent count (< 1 month before admission) obtained in clinically stable conditions: 662 (116) v 210 (54) eosinophils/mm3, p < 0.0003. The decrease in the eosinophil count was more pronounced in the infected patients than in the non-infected patients, but the difference was not statistically significant (p > 0.05). Similarly, transcutaneous arterial oxygen pressure (PaO2) values measured during acute asthma exacerbations tended to be lower in infected patients, without, however, reaching statistical significance: 8.6 (0.7) v 10.1 (0.9) kPa, p > 0.05). The correlation between the decrease in blood eosinophil count and PaO2 during the acute asthma exacerbations was significant in all the patients (r2 = 0.235, p = 0.022) and in the non-infected patients (r2 = 0.653, p = 0.015), but not in infected patients. In this latter subgroup, a significant negative correlation was found between blood neutrophil counts during acute asthma exacerbations and PaO2 (r2 = 349, p = 0.026).

CONCLUSIONS

During acute asthma exacerbations in atopic patients without clinical evidence of infection, the decrease in blood eosinophil count correlates significantly with the decrease in PaO2, further supporting the role of eosinophils in allergic asthma.

In childhood asthma the degree of allergen-induced T-lymphocyte proliferation is related to serum IgE levels and to blood eosinophilia

OBJECTIVE

To investigate whether the state of activation of circulating T-cells in childhood asthma could be related to serum IgE levels and/or to blood eosinophilia.

METHODS

Seventeen atopic asthmatic children, sensitized to Dermatophagoides pteronyssinus (Der p), in stable condition at the time of the study and 15 sex-matched and age-matched controls were studied. The expression of activation surface markers (HLA-DR and CD25) on peripheral blood mononuclear cells (PBMCs) was tested by monoclonal antibodies and FACS analysis, while the PBMC proliferative response to Der p antigens was measured by tritiated thymidine (3HTdR) incorporation.

RESULTS

As compared to controls, atopic children showed higher eosinophil counts (P < .01), similar lymphocyte counts (P > .1, each comparison) but higher proportion of HLA-DR+ and CD25+ T-lymphocytes (P < .05, each comparison). A significant Der p allergen-induced PBMC proliferation was observed in atopic children (P < .01) but not in controls (P > .1). Both in controls and in atopic children, no correlations were found between lymphocyte counts and eosinophil counts or total or allergen-specific IgE levels (P > .1, each comparison). In contrast, weak correlations were detected between the degree of allergen-induced PBMC proliferation and: a) allergen-specific IgE levels in serum (P < .05) and b) eosinophil counts (P < .05).

CONCLUSION

These data support the concept that the degree of activation of allergen-specific T-lymphocytes in blood may reflect the intensity of allergic sensitization in childhood asthma.

Nasal brushing: a clinically useful procedure in pediatric patients with rhinosinusitis?

Sinusitis is a common complication of non-allergic and allergic rhinitis, and can trigger lower respiratory diseases, such as bronchitis and asthma. Standard radiography is unable to give any data about the underlying pathological mechanisms (infectious or allergic) involved and infectious rhinosinusitis is very common in pediatric age, even in allergic patients. We investigated the possibility of obtaining more useful diagnostic information, performing nasal brushing (NB) on 117 children with recurrent respiratory symptoms. The following hypothesis were evaluated: (1) whether NB neutrophil/eosinophil percentages and/or NB culture could predict the radiological evidence of maxillary sinusitis; and (2) whether differences between nonallergic and allergic patients could be detected. In the total patient group and in the nonallergic group, the comparison of NB neutrophil percentages in patients with and without maxillary sinusitis showed a statistically significant difference (median 2 and 18%, respectively; P < 0.001). In the nonallergic group, a NB neutrophil rate > or = 5% was chosen as a cut-off between positive and negative NB diagnosis of rhinosinusitis and NB data were compared with radiological investigations. The results obtained showed that NB was fairly sensitive (91%) and predictive (84%). In allergic patients, neither neutrophil nor eosinophil percentages significantly correlated with the presence of sinusitis. Microbiological studies showed that, even if the presence of bacteria in NB resulted associated with sinusitis, a negative culture was not predictive of the absence of the disease. We therefore suggest that NB describes the present inflammatory status of the upper airways, hence, it is more suitable to describe the inflammation related to ongoing upper respiratory tract infections rather than chronic inflammation due to allergic rhinitis, characterized by relapsing episodes of acute inflammation. In conclusion, we propose to consider NB a reliable tool in the diagnosis of rhinosinusitis, particularly in nonallergic pediatric patients. Compared to standard radiological techniques, NB makes it possible to avoid radiation exposure and gives information about the pathological mechanisms involved in the single patient.

Blood eosinophilia and degree of sensitization to house dust mites in preschool and school children with asthma

In allergic asthma, there is convincing evidence that changes in eosinophil and lymphocyte state of activation in blood may reflect disease activity. We evaluated whether simple blood eosinophil or lymphocyte counts in atopic children with asthma could reflect the degree of allergic sensitization. Seventy-six asthmatic children, sensitized to house dust mites (HDM), in stable conditions at the time of the study, and 53 sex- and age-matched controls (CTR) were studied. As compared to CTR, allergic patients showed higher eosinophil numbers and percentages (p < 0.001) but similar lymphocyte numbers and proportions (p > 0.1). Both in CTR and in allergic patients, eosinophil counts did not correlate with lymphocyte counts (p > 0.05; each comparison) but positive correlations were observed between eosinophil numbers and percentages and paper radio immunosorbent test (PRIST) levels or radio-allergo sorbent test (RAST) classes (p < 0.001; each comparison). When allergic asthmatic individuals were subdivided according to their age into two subgroups (Gr), no differences were found in eosinophil and lymphocyte counts and in PRIST levels and RAST values between Gr1 (< or =5 years old [preschool children]) and Gr2 (>5 years old [school children]) (p > 0.05; each comparison). Interestingly, although positive correlations between eosinophil counts and PRIST levels were found in both subgroups (p < 0.05; each comparison), only in Gr2 did eosinophil counts correlate positively with RAST classes (p < 0.001). No correlations between lymphocyte counts and PRIST levels or RAST classes were demonstrated (p > 0.05; each comparison). These data suggest that although blood eosinophilia was similar in preschool and in allergic asthmatic school children sensitized to HDM, only in the oldest children did blood eosinophil counts appear to be related to the degree of HDM-specific sensitization.

e-NO peak versus e-NO plateau values in evaluating e-NO production in steroid-naive and in steroid-treated asthmatic children and in detecting response to inhaled steroid treatment

SUMMARY. Airway nitric oxide (NO) production can be measured by chemiluminescence analyzer in children able to perform a single low exhalation. The aim of the present study was to evaluate whether exhaled NO (e-NO) peaks (first part of the exhalation) were as useful as e-NO plateaus (last part of the exhalation) in evaluating e-NO production in asthmatic children and in detecting responses to inhaled steroid treatment. E-NO peak, plateau, and rate of production values were measured in 100 atopic asthmatic children using a chemiluminescence analyser. Thirty-seven patients (mean age, 11.1 +/- 0.7 years) were receiving inhaled steroids (flunisolide, 0.8-1 mg daily) or beclomethasone (0.2-0.4 mg daily), while the remaining 63 (mean age, 12.0 +/- 0.4 yrs) were-steroid naive and treated only with inhaled beta(2)-agonists on an as-needed basis. Fifteen out of the 63 steroid-naive patients were reevaluated after a short course (3 weeks) of inhaled corticosteroid treatment (flunisolide, 0.8-1 mg daily, or beclomethasone, 0.2-0.4 mg daily). Regardless of the type of data analysis (peak, plateau, or rate of production), the e-NO values of the steroid-naive patients were significantly higher than those of inhaled steroid-treated patients (P < 0.01, each comparison). Similarly, in the subgroup of steroid-naive patients, the three methods were able to detect a decrease in e-NO levels by inhaled steroid therapy (P < 0.001, each comparison). Plotting the difference between e-NO peak and e-NO plateau values against their average, the peak e-NO concentrations were higher than e-NO plateau values. This difference was independent of the absolute e-NO concentration. The results of the two types of data analysis seems to agree more closely in steroid-naive patients than in steroid treated patients, or in the subgroup of steroid-naive patients who received a short course treatment with inhaled steroids. In steroid-treated subjects, the differences were up to five times higher for peak than plateau e-NO values. These data suggest that both e-NO plateau and e-NO peak values are useful in detecting airway NO production in atopic asthmatic children, but they cannot be used interchangeably. Because of possible nasal contamination in e-NO peak measurement, we prefer e-NO plateau levels for evaluating lower airway e-NO production.

How can we best read exhaled nitric oxide flow curves in asthmatic children?

Orally exhaled nitric oxide (NO) levels are increased in children with asthma and thought to reflect the local inflammatory events in the airways. NO production in the lower respiratory airway is reflected in the plateau values of the NO curve, recorded while the patient is performing a slow vital capacity manoeuvre. In young patients, however, plateau values may be difficult to obtain, because the slow vital capacity manoeuvre is often terminated prematurely. In the present study, 60 steroid-naive atopic asthmatic children and 17 normal age-matched controls were asked to perform a slow vital capacity manoeuvre, during which fractional exhaled NO (FEno) levels were measured and evaluated as: a) FEno plateau levels of last part of exhalation (NO plateau); b) FEno peak values, c) area under the FEno curve (AUC). Thirteen out of the 60 steroidnaive patients were reevaluated after a short course of inhaled corticosteroid treatment. Independently of the type of data analysis, FEno values of asthmatics were significantly higher than those observed in normal controls (P < 0.001, each comparison). In addition, possibly because of upper airway NO contamination, FEno peak values were significantly higher than FEno plateau levels in asthmatic patients and in control subjects (P < 0.001, each comparison). Both in asthmatics and controls, highly positive correlations were observed between: a) FEno plateau and peak values (r > 0.7, P < 0.01, each correlation), b) FEno plateau and AUC values (r > 0.7, P < 0.01, each correlation) and c) FEno peak and AUC values (r > 0.9, P < 0.001, each correlation). In asthmatic patients, the three types of data analysis were equally sensitive in detecting the decrease in FEno levels induced by inhaled steroid therapy (P < 0.05, each comparison), with a good correlation between the three data analyses (r > 0.5, P < 0.05, each correlation). Thus, although quantitatively different, comparable data reflecting airway inflammation can be obtained evaluating FEno plateau, FEno peak, and area under the curve, on account of possible upper airway contamination in FEno peak, FEno plateau should be preferred to measure lower airway NO production.