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Michils A, Akset M, Haccuria A, Perez-Bogerd S, Malinovschi A, Van Muylem A. The Impact of Airway Obstruction on Feno Values in Asthma Patients. THE JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY. IN PRACTICE 2024; 12:111-117. [PMID: 37634805 DOI: 10.1016/j.jaip.2023.08.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 07/20/2023] [Accepted: 08/16/2023] [Indexed: 08/29/2023]
Abstract
BACKGROUND Exhaled nitric oxide (Feno) is used as a marker of type-2 airway inflammation in asthma management. Studies with airway challenges demonstrated that a reduction in airway caliber decreases Feno levels. OBJECTIVE To evaluate the impact of airway caliber reduction occurring spontaneously in patients with asthma on Feno values in daily clinical practice. METHODS In this post hoc analysis, Feno, FEV1, and asthma control questionnaire scores were recorded on each visit for 120 (1073 visits) adult patients with asthma. Blood eosinophils were measured intermittently. The intraindividual relationship between Feno and FEV1 was evaluated via a linear mixed model. The determinants of the individual mean Feno were measured by a stepwise multivariate linear model including individual mean FEV1, inhaled corticosteroid dose, asthma control questionnaire score, and blood eosinophils. RESULTS Variations in the negative Feno-FEV1 relationship within individuals at different times were significantly determined by the individual's mean FEV1. This relationship did not hold for individuals above the 75th and below the 25th quartiles. The best explanatory variables for individual mean Feno were FEV1 (+4.3 parts per billion/10%pred) and blood eosinophil count (+1 part per billion per 100 cells/mm3). DISCUSSION In the presence of variable degrees of heterogeneous patterns of airway inflammation, airway caliber is shown to be an independent and significant determinant of Feno when measured in patients with asthma. We would propose a +4-parts-per-billion correction factor to the measured Feno value for each 10% reduction below 100% predicted FEV1. Doing this should improve the rigor of interpretation of Feno as an indicator of type-2 inflammation in patients with low FEV1.
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Affiliation(s)
- Alain Michils
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Maud Akset
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Amaryllis Haccuria
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Silvia Perez-Bogerd
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Andreï Malinovschi
- Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden
| | - Alain Van Muylem
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium.
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Demey L, Van Muylem A, Malinovschi A, Haccuria A, Perez-Bogerd S, Michils A. Exploring the sites and kinetics of bronchodilator response to β-2 agonists in asthma. J Appl Physiol (1985) 2021; 130:1106-1113. [PMID: 33444118 DOI: 10.1152/japplphysiol.00643.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously documented, in patients with asthma, three different profiles of bronchodilation induced by short-acting β-2 mimetics (SABA), characterized by dilation up to central, preacinar, and intra-acinar airways assessed by ventilation distribution tests and associated with no change, increase, and decrease of fractional exhaled nitric oxide concentration (FENO), respectively. To investigate the dynamics of these profiles over the entire SABA action period, assuming that bronchodilation of proximal and peripheral airways could exhibit varying kinetics due to differences in the distribution of β-2 receptors in both the central and peripheral human airways. FENO, forced expired volume in one second (FEV1), and the slope (S) of He and SF6 phase III (single-breath test) were measured in asthma patients before, and up to 6 h after SABA inhalation (salbutamol 400 µg). SHe and SSF6 decrease reflects pre- and intra-acinar obstruction relief, respectively. Thirty patients with asthma (12F/18M, aged 45 ± 18 yr) were divided into groups with positive (NO+, n = 9), negative (NO-, n = 11), and no (NO=, n = 10) FENO acute change. In the NO- group, FEV1 increased for up to 4 h, whereas FENO, SHe, and SF6 decreased in the early phase only. In stark contrast, in the NO+ group, FEV1 increased in the early phase only whereas the FENO increase and the SHe decrease lasted for up to 4 h. This study documents various profiles of SABA-induced bronchodilation in patients with asthma, differing both by sites and dynamics of the bronchodilator process. So, detailed understanding of the bronchodilator effect of β2-agonists in asthma should not solely be limited to studying their impact on FEV1.NEW & NOTEWORTHY FEV1 increase usually observed after the inhalation of short-acting β2-agonists in asthma patients tends to involve peripheral airways. This study shows that the heterogeneity of responses to short-acting β2-agonists in asthma not only involves distinct sites of bronchodilation, but also distinct sequences between these sites. This indicates that a detailed understanding of the bronchodilator effect of β2-agonists in asthma should not be limited to studying its early impact on FEV1.
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Affiliation(s)
- Lucas Demey
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Alain Van Muylem
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Andrei Malinovschi
- Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden
| | - Amaryllis Haccuria
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Silvia Perez-Bogerd
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
| | - Alain Michils
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
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Exhaled nitric oxide and its predictive power related to lung function and bronchial inflammation. Biochem Pharmacol 2020; 179:114101. [DOI: 10.1016/j.bcp.2020.114101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 06/11/2020] [Accepted: 06/12/2020] [Indexed: 11/22/2022]
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Pérez-Bogerd S, Michils A, Malinovschi A, Van Muylem A. COPD patients with peripheral airway obstruction reversibility identified by exhaled nitric oxide. J Breath Res 2019; 13:036002. [PMID: 30802891 DOI: 10.1088/1752-7163/ab0a14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
RATIONALE Besides its role as an inflammatory marker in asthma, fractional exhaled nitric oxide (FENO) provides information on the extent of the airway obstruction process through evaluating its change after bronchodilation. OBJECTIVE To investigate whether FENO change after bronchodilation can identify different sites of airway obstruction in COPD patients. METHODS FENO, FEV1 and the slopes (S) of the alveolar plateau of the single breath washout test (SBWT) were measured in 61 stable COPD patients (FEV1 34.5% predicted) before and after the inhalation of 400 μg salbutamol. SBWT used Helium (He), and sulfur-hexafluoride (SF6). Obstruction relief occurring in pre-acinar and intra-acinar small airways is expected to decrease SHe and SSF6, respectively. Indices changes (Δ) after bronchodilation were expressed as a percentage of pre-bronchodilation values. RESULTS FENO stability (∣ΔFENO∣ ≤ 11%) was observed in 19 patients [-2.7(6.7)%] [mean (SD)] (NO = group); ΔFENO > 11% [+37.4(27.7)%] in 20 patients (NO+ group) and ΔFENO < -11% in 22 patients [-31.2(9.8)%] (NO- group). A similar ΔFEV1 (p = 0.583; [+9.4(9.6)%]) was found in the three groups. In NO = and NO+ groups, neither SHe nor SSF6 changed; in NO- both SHe [-12.4(27.5)%, p = 0.007] and SSF6 [-20.2(20.4)%, p < 0.001] significantly decreased. CONCLUSION Different patterns of FENO response to β 2-agonists were observed in COPD most likely depending on the extent of the dilation process. A profile of airway obstruction with an extensive β 2-agonist response down to lung periphery is identified by FENO reduction after acute bronchodilation in 30% of COPD patients. The clinical relevance of this profile requires further investigation.
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Affiliation(s)
- Silvia Pérez-Bogerd
- Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
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Karamaoun C, Haut B, Van Muylem A. A new role for the exhaled nitric oxide as a functional marker of peripheral airway caliber changes: a theoretical study. J Appl Physiol (1985) 2018; 124:1025-1033. [DOI: 10.1152/japplphysiol.00530.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although considered as an inflammation marker, exhaled nitric oxide (FENO) was shown to be sensitive to airway caliber changes to such an extent that it might be considered as a marker of them. It is thus important to understand how these changes and their localization mechanically affect the total NO flux penetrating the airway lumen ( JawNO), and hence FENO, independently from any inflammatory status change. In this work, a new model was used. It simulates NO production, consumption, and diffusion inside the airway epithelium, NO excretion from the epithelial wall into the airway lumen and, finally, its axial transport by diffusion and convection in the airway lumen. This model may also consider the possible presence of a fluid layer coating the epithelial wall. Simulations were performed. They show the great sensitivity of JawNO to peripheral airway caliber changes. Moreover, FENO shows distinct behaviors, depending on the location of the caliber change. Considering a bronchodilation, absence of FENO change was associated with dilation of central airways, FENO increase with dilation down to pre-acinar small airways, and FENO decrease with intra-acinar dilation due to the amplification of the back diffusion flux. The presence of a fluid layer was also shown to play a significant role in FENO changes. Altogether, the present work theoretically supports that specific FENO changes in acute situations are linked to specifically located airway caliber changes in the lung periphery. This opens the way for a new role for FENO as a functional marker of peripheral airway caliber change. NEW & NOTEWORTHY Using a new model of nitric oxide production and transport, allowing realistic simulation of airway caliber change, the present work theoretically supports that specific changes of the molar fraction of nitric oxide in the exhaled air, occurring without any change in the inflammatory status, are linked to specifically located airway caliber changes in the lung periphery. This opens the way for a new role for FENO as a functional marker of peripheral airway caliber change.
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Affiliation(s)
- Cyril Karamaoun
- Ecole polytechnique de Bruxelles, Transfers Interfaces and Processes, Université libre de Bruxelles, Brussels, Belgium
| | - Benoit Haut
- Ecole polytechnique de Bruxelles, Transfers Interfaces and Processes, Université libre de Bruxelles, Brussels, Belgium
| | - Alain Van Muylem
- Chest Department, Erasme University Hospital, Université libre de Bruxelles, Brussels, Belgium
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Haccuria A, Van Muylem A, Malinovschi A, Doan V, Michils A. Small airways dysfunction: the link between allergic rhinitis and allergic asthma. Eur Respir J 2018; 51:51/2/1701749. [PMID: 29467201 DOI: 10.1183/13993003.01749-2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 12/07/2017] [Indexed: 11/05/2022]
Abstract
Abnormal airway reactivity and overproduction of nitric oxide (NO) occurring in small airways have been found in asthma. If the "one airway, one disease" concept is consistent, such dysfunctions should also be detected in the peripheral airways of patients suffering from allergic rhinitis.We investigated whether peripheral airway reactivity and NO overproduction could be documented in distal airways in patients with allergic rhinitis. Exhaled NO fraction (FeNO) and the slope (S) of phase III of the single-breath washout test (SBWT) of helium (He) and sulfur hexafluoride (SF6) were measured in 31 patients with allergic asthma, 23 allergic rhinitis patients and 24 controls, before and after sputum induction. SBWT is sensitive to airway calibre change occurring in the lung periphery.The FeNO decrease was more significant in asthma and rhinitis than in controls (-55.1% and -50.0%, respectively, versus -40.8%) (p=0.007 and p=0.029, respectively). SSF6 and SHe increased in all groups. Change in SHe (ΔSHe) > ΔSSF6 was observed in rhinitis (p=0.004) and asthma (p<0.001), whereas ΔSSF6 = ΔSHe in controls (p=0.431).This study provides evidence of peripheral airway dysfunction in patients with allergic rhinitis quite similar to that described in asthma. Furthermore, a large proportion of the increased NO production reported in allergic rhinitis appears to originate in the peripheral airways.
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Affiliation(s)
- Amaryllis Haccuria
- Chest Dept, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Alain Van Muylem
- Chest Dept, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Andrei Malinovschi
- Dept of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden
| | - Vi Doan
- Chest Dept, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Alain Michils
- Chest Dept, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
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Different patterns of exhaled nitric oxide response to β2-agonists in asthmatic patients according to the site of bronchodilation. J Allergy Clin Immunol 2015; 137:806-12. [PMID: 26688519 DOI: 10.1016/j.jaci.2015.09.054] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 09/18/2015] [Accepted: 09/24/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND In asthmatic patients undergoing airway challenge, fraction of exhaled nitric oxide (FENO) levels decrease after bronchoconstriction. In contrast, model simulations have predicted both decreased and increased FENO levels after bronchodilation, depending on the site of airway obstruction relief. OBJECTIVE We sought to investigate whether β2-agonists might induce divergent effects on FENO values in asthmatic patients as a result of airway obstruction relief occurring at different lung depths. METHODS FENO, FEV1, and the slope of phase III of the single-breath washout test (S) of He (S(He)) and sulfur hexafluoride (S(SF6)) were measured in 68 asthmatic patients before and after salbutamol inhalation. S(He) and S(SF6) decreases reflected preacinar and intra-acinar obstruction relief, respectively. Changes (Δ) were expressed as a percentage from the baseline. RESULTS No FENO change (|ΔFENO| ≤ 10%) was found in 16 patients (mean [SD]: 2.5% [5.2%]; ie, FENO= group); a ΔFENO value of greater than 10% was found in 23 patients (31.7% [20.3%]; ie, the FENO+ group); and a ΔFENO value of less than -10% was found in 29 patients (-31.5% [17.3%]; ie, the FENO- group). All groups had similar ΔFEV1 values. In the FENO= group neither S(He) nor S(SF6) changed, in the FENO+ group only S(He) decreased significantly (-21.8% [SD 28.5%], P = .03), and in the FENO- group both S(He) (-29.8% [24.0%], P < .001) and S(SF6) (-27.2% [23.3%], P < .001) decreased. DISCUSSION Three FENO behaviors were observed in response to β2-agonists: a decrease likely caused by relief of an intra-acinar airway obstruction that we propose reflects amplification of nitric oxide back-diffusion, an increase likely associated with a predominant dilation up to the preacinar airways, and FENO stability when obstruction relief involved predominantly the central airways. In combination, these results suggest a new role for FENO in identifying the site of airway obstruction in asthmatic patients.
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Usmani OS. Small airways dysfunction in asthma: evaluation and management to improve asthma control. ALLERGY, ASTHMA & IMMUNOLOGY RESEARCH 2014; 6:376-88. [PMID: 25228994 PMCID: PMC4161678 DOI: 10.4168/aair.2014.6.5.376] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/01/2014] [Indexed: 01/24/2023]
Abstract
The small airways have been neglected for many years, but interest in the topic has been rekindled with recent advances in measurement techniques to assess this region and also the ability to deliver therapeutics to the distal airways. Current levels of disease control in asthmatic patients remain poor and there are several contributory factors including; poor treatment compliance, heterogeneity of asthma phenotypes and associated comorbidities. However, the proposition that we may not be targeting all the inflammation that is present throughout the whole respiratory tree may also be an important factor. Indeed decades ago, pathologists and physiologists clearly identified the importance of small airways dysfunction in asthmatic patients. With improved inhaler technology to deliver drug to target the whole respiratory tree and more sensitive measures to assess the distal airways, we should certainly give greater consideration to treating the small airway region when seeing our asthmatic patients in clinic. The aim of this review is to address the relevance of small airways dysfunction in the daily clinical management of patients with asthma. In particular the role of small particle aerosols in the management of patients with asthma will be explored.
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Affiliation(s)
- Omar S Usmani
- Airway Disease Section, National Heart and Lung Institute, Imperial College London & Royal Brompton Hospital, London, UK
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Roos AB, Mori M, Grönneberg R, Österlund C, Claesson HE, Wahlström J, Grunewald J, Eklund A, Erjefält JS, Lundberg JO, Nord M. Elevated exhaled nitric oxide in allergen-provoked asthma is associated with airway epithelial iNOS. PLoS One 2014; 9:e90018. [PMID: 24587191 PMCID: PMC3938593 DOI: 10.1371/journal.pone.0090018] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 12/03/2013] [Indexed: 01/01/2023] Open
Abstract
Background Fractional exhaled nitric oxide is elevated in allergen-provoked asthma. The cellular and molecular source of the elevated fractional exhaled nitric oxide is, however, uncertain. Objective To investigate whether fractional exhaled nitric oxide is associated with increased airway epithelial inducible nitric oxide synthase (iNOS) in allergen-provoked asthma. Methods Fractional exhaled nitric oxide was measured in healthy controls (n = 14) and allergic asthmatics (n = 12), before and after bronchial provocation to birch pollen out of season. Bronchoscopy was performed before and 24 hours after allergen provocation. Bronchial biopsies and brush biopsies were processed for nitric oxide synthase activity staining with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), iNOS immunostaining, or gene expression analysis of iNOS by real-time PCR. NADPH-d and iNOS staining were quantified using automated morphometric analysis. Results Fractional exhaled nitric oxide and expression of iNOS mRNA were significantly higher in un-provoked asthmatics, compared to healthy controls. Allergic asthmatics exhibited a significant elevation of fractional exhaled nitric oxide after allergen provocation, as well as an accumulation of airway eosinophils. Moreover, nitric oxide synthase activity and expression of iNOS was significantly increased in the bronchial epithelium of asthmatics following allergen provocation. Fractional exhaled nitric oxide correlated with eosinophils and iNOS expression. Conclusion Higher fractional exhaled nitric oxide concentration among asthmatics is associated with elevated iNOS mRNA in the bronchial epithelium. Furthermore, our data demonstrates for the first time increased expression and activity of iNOS in the bronchial epithelium after allergen provocation, and thus provide a mechanistic explanation for elevated fractional exhaled nitric oxide in allergen-provoked asthma.
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Affiliation(s)
- Abraham B. Roos
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail:
| | - Michiko Mori
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Reidar Grönneberg
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
| | - Christina Österlund
- Department of Medicine, Division of Hematology, Karolinska Institutet, Stockholm, Sweden
| | - Hans-Erik Claesson
- Department of Medicine, Division of Hematology, Karolinska Institutet, Stockholm, Sweden
| | - Jan Wahlström
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
| | - Johan Grunewald
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
| | - Anders Eklund
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
| | - Jonas S. Erjefält
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Jon O. Lundberg
- Department of Physiology and Pharmacology, Section of Pharmacological Nitric Oxide Research, Karolinska Institutet, Stockholm, Sweden
| | - Magnus Nord
- Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden
- Safety Science, Global Regulatory Affairs & Patient Safety, AstraZeneca Global Medicines Development, Mölndal, Sweden
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Haccuria A, Michils A, Michiels S, Van Muylem A. Exhaled nitric oxide: a biomarker integrating both lung function and airway inflammation changes. J Allergy Clin Immunol 2014; 134:554-9. [PMID: 24522091 DOI: 10.1016/j.jaci.2013.12.1070] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 11/28/2013] [Accepted: 12/10/2013] [Indexed: 10/25/2022]
Abstract
BACKGROUND The increased fraction of exhaled nitric oxide (Feno) values observed in asthmatic patients are thought to reflect increased airway inflammation. However, Feno values can be affected by airway caliber reduction, representing a bias when using Feno values to assess asthma control. OBJECTIVE We sought to determine the effect of changes in both airway caliber and inflammation on Feno values using the allergen challenge model. METHODS FEV1 and Feno values were measured during early airway responses (EARs) and late airway responses after challenge with house dust mite allergens in 15 patients with mild allergic asthma. Helium and sulfur hexafluoride (SF6) phase III expired concentration slopes (SHe and SSF6, respectively) from single-breath washout tests were measured to identify sites of airway constriction. RESULTS In EARs, FEV1 and Feno value decreases reached 36.8% and 22%, respectively (P < .001). ΔSHe was greater than ΔSSF6 (+189.4% vs +82.2%, P = .001). In late airway responses FEV1 and Feno value decreases reached 31.7% and 28.7%, respectively (P < .001), with the same ΔSHe and ΔSSF6 pattern (+155.8% vs +76%, P = .001). Eight hours after the EAR, FEV1 was still decreased (P < .001), whereas Feno values had returned to baseline. At 24 hours, FEV1 had returned to baseline, with Feno values increased by 38.7% (P = .04). CONCLUSION In patients with mild allergic asthma, airway caliber changes modulate changes in Feno values resulting from airway inflammation. Therefore Feno should no longer be considered solely an inflammation biomarker but rather a biomarker that integrates both airway inflammation and lung function changes. Furthermore, early and late phases resulting from allergen exposure were shown to involve similar lung regions.
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Affiliation(s)
- Amaryllis Haccuria
- Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium; Chest Department, Centre Hospitalier Régional de Namur, Namur, Belgium
| | - Alain Michils
- Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Sébastien Michiels
- Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Alain Van Muylem
- Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium.
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