A two-compartment model of pulmonary nitric oxide exchange dynamics

Determination of the two-compartment model parameters of exhaled HCN by fast negative photoionization mass spectrometry

Breath exhaled hydrogen cyanide (HCN) has been identified to be associated with several respiratory diseases. Accurately distinguishing the concentration and release rate of different HCN sources is of great value in clinical research. However, there are still significant challenges due to the high adsorption and low concentration characteristics of exhaled HCN. In this study, a two-compartment kinetic model method based on negative photoionization mass spectrometry was developed to simultaneously determine the kinetic parameters including concentrations and release rates in the airways and alveoli. The influences of the sampling line diameter, length, and temperature on the response time of the sampling system were studied and optimized, achieving a response time of 0.2 s. The negative influence of oral cavity-released HCN was reduced by employing a strategy based on anatomical lung volume calculation. The calibration for HCN in the dynamic range of 0.5-100 ppbv and limit of detection (LOD) at 0.3 ppbv were achieved. Subsequently, the experiments of smoking, short-term passive smoking, and intake of bitter almonds were performed to examine the influences of endogenous and exogenous factors on the dynamic parameters of the model method. The results indicate that compared with steady-state concentration measurements, the kinetic parameters obtained using this model method can accurately and significantly reflect the changes in different HCN sources, highlighting its potential for HCN-related disease research.

Alveolar nitric oxide concentration plays an important role in identifying cough variant asthma and assessing asthma control in children

OBJECTIVE

To study the value of alveolar nitric oxide concentration (CaNO) in the identification and disease control of cough variant asthma.

METHODS

A retrospective study was conducted on cough variant asthma (CVA-Group), nonasthmatic cough (NAC-Group) and healthy control children (C-Group) aged 5-12 years. The exhaled nitric oxide and spirometry test results of the three groups were collected and compared.

RESULTS

A total of 410 children were included in this study, including 190 in the CVA-Group, 183 in the NAC-Group, and 37 in the C-Group. The CaNO values of the CVA-Group [11.40 ppb (8.48-14.25)] were significantly higher than those of the NAC-Group and C-Group (all p values <.05). The MMEF %pred values of the CVA-Group [63.65 (56.28-73.58)] were significantly lower than those of the NAC-Group and C-Group (all p values <.05). FeNO50, JawNO and other spirometry indices (FVC %pred, FEV1%pred, FEV1/FVC %pred) showed no significant difference among the three groups. ROC curve analysis showed that the optimal cutoff point value of CaNO was 9.45 ppb, corresponding to 0.816 sensitivity and 0.736 specificity. Spearman correlation analysis showed a significant negative correlation between the CaNO measurement and CVA control score.

CONCLUSIONS

CaNO can not only help identify CVA early in children aged 5-12 years with chronic cough but is also significantly negatively correlated with the CVA control score.

Simultaneous real-time detection of fractional exhaled nitric oxide and end-tidal carbon dioxide by quantum cascade laser absorption spectroscopy

The simultaneous detection of fractional exhaled nitric oxide (FeNO) and end-tidal carbon dioxide (ETCO2) is of great importance for the distinguishing and diagnosis of asthma and chronic obstructive pulmonary disease (COPD), providing more comprehensive information on respiratory disorders. This work demonstrates a simultaneous ETCO2 and FeNO detection system based on quantum cascade laser absorption spectroscopy (QCLAS) technology was presented. The system employs wavelength modulation spectroscopy (WMS) technology and the Herriott multi-pass cell, achieving a detection limit of 2.82 ppb for nitric oxide (NO) and 0.05 % for carbon dioxide (CO2). Real-time exhalation measurements were performed on volunteers with varying ETCO2 and FeNO levels, and the results of the test can accurately distinguish whether the corresponding volunteer was healthy, had asthma or COPD. The effect of exhalation flow rate on the concentration of the two gases was explored. A range of expiratory flow rates were tested in the flow rate interval from 1 to 4 L/min, and there was always an inverse relationship between expiratory flow rate and FeNO concentration, but flow rate changes did not affect ETCO2 concentration. The results indicate that this detection system can simultaneously and effectively measure ETCO2 and FeNO concentrations in real-time.

Associations between fine particulate air pollution with small-airway inflammation: A nationwide analysis in 122 Chinese cities

Alveolar nitric oxide is a non-invasive indicator of small-airway inflammation, a key pathophysiologic mechanism underlying lower respiratory diseases. However, no epidemiological studies have investigated the impact of fine particulate matter (PM2.5) exposure on the concentration of alveolar nitric oxide (CANO). To explore the associations between PM2.5 exposure in multiple periods and CANO, we conducted a nationwide cross-sectional study in 122 Chinese cities between 2019 and 2021. Utilizing a satellite-based model with a spatial resolution of 1 × 1 km, we matched long-term, mid-term, and short-term PM2.5 exposure for 28,399 individuals based on their home addresses. Multivariable linear regression models were applied to estimate the associations between PM2.5 at multiple exposure windows and CANO. Stratified analyses were also performed to identify potentially vulnerable subgroups. We found that per interquartile range (IQR) unit higher in 1-year average, 1-month average, and 7-day average PM2.5 concentration was significantly associated with increments of 17.78% [95% confidence interval (95%CI): 12.54%, 23.26%], 8.76% (95%CI: 7.35%, 10.19%), and 4.00% (95%CI: 2.81%, 5.20%) increment in CANO, respectively. The exposure-response relationship curves consistently increased with the slope becoming statistically significant beyond 20 μg/m3. Males, children, smokers, individuals with respiratory symptoms or using inhaled corticosteroids, and those living in Southern China were more vulnerable to PM2.5 exposure. In conclusion, our study provided novel evidence that PM2.5 exposure in long-term, mid-term, and short-term periods could significantly elevate small-airway inflammation represented by CANO. Our results highlight the significance of CANO measurement as a non-invasive tool for early screening in the management of PM2.5-related inflammatory respiratory diseases.

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

Lung Involvement in Patients with Ulcerative Colitis: Relationship between Exhaled Nitric Oxide and Lung Function

Ulcerative colitis (UC) is characterized by immune system dysregulation with frequent extraintestinal manifestations, including airway involvement. A reduction in CO diffusing capacity and functional alterations in small airways have been described. An extended analysis of fractional exhaled nitric oxide (FeNO) may distinguish the sites of production, and the presence of small airway inflammation may be a useful, non-invasive marker for patient follow-up. The aim of our study was to compare the PFTs as well as FeNO and CANO values of UC patients with different clinical disease activities and healthy subjects to reveal lung function abnormalities and the presence of subclinical airway inflammation. We enrolled 42 adult outpatients at different clinical activity stages of UC (39 ± 13 years) and a healthy control group of 41 subjects (29 ± 3 years). C-reactive protein (CRP) and FeNO values at different flows (50,100, and 200 mL/s) were collected. All patients performed pulmonary function tests (PFTs) with static volumes and diffusing capacity (DLCO). FeNO and CANO values were significantly increased in UC patients when compared with controls (p = 0.0008 and p < 0.0001, respectively) and were proportional to disease activity (FeNO class 3: 28.1 ppb vs. classes 1-2: 7.7 ppb; CANO values class 3: 8.6 ppb vs. classes 1-2: 2.7 ppb (p < 0.0001)). TLC and DLCO were significantly reduced in severe (Mayo 3) UC patients (p = 0.010 and p = 0.003, respectively). The results of this study show significant lung functional abnormalities in UC patients and suggest the presence of airway inflammation directly correlated with disease activity, suggesting the need for an integrated approach in routine assessment.

Role of alveolar nitric oxide in gastroesophageal reflux-associated cough: prospective observational study

BACKGROUND

Fractional exhaled nitric oxide (FeNO) measured at multiple exhalation flow rates can be used as a biomarker to differentiate central and peripheral airway inflammation. However, the role of alveolar nitric oxide (CaNO) indicating peripheral airway inflammation remains unclear in gastroesophageal reflux-associated cough (GERC).

OBJECTIVES

We aimed to characterize the changes in alveolar nitric oxide (CaNO) and determine its clinical implication in GERC.

DESIGN

This is a single-center prospective observational study.

METHODS

FeNOs at exhalation flow rates of 50 and 200 ml/s were measured in 102 patients with GERC and 134 patients with other causes of chronic cough (non-GERC). CaNO was calculated based on a two-compartment model and the factors associated with CaNO were analyzed. The effect of anti-reflux therapy on CaNO was examined in 26 GERC patients with elevated CaNO.

RESULTS

CaNO was significantly elevated in GERC compared with that in non-GERC (4.6 ± 4.4 ppb versus 2.8 ± 2.3 ppb, p < 0.001). GERC patients with high CaNO (>5 ppb) had more proximal reflux events (24 ± 15 versus 9 ± 9 episodes, p = 0.001) and a higher level of pepsin (984.8 ± 492.5 versus 634.5 ± 626.4 pg/ml, p = 0.002) in sputum supernatant than those with normal CaNO. More GERC patients with high CaNO required intensified anti-reflux therapy (χ2 = 3.963, p = 0.046), as predicted by a sensitivity of 41.7% and specificity of 83.3%. Cough relief paralleled a significant improvement in CaNO (8.3 ± 3.0 versus 4.8 ± 2.6 ppb, p < 0.001).

CONCLUSION

Peripheral airway inflammation can be assessed by CaNO measurement in GERC. High CaNO indicates potential micro-aspiration and may predict a necessity for intensified anti-reflux therapy.

Markers of Bronchiolitis Obliterans Syndrome after Lung Transplant: Between Old Knowledge and Future Perspective

Bronchiolitis obliterans syndrome (BOS) is the most common form of CLAD and is characterized by airflow limitation and an obstructive spirometric pattern without high-resolution computed tomography (HRCT) evidence of parenchymal opacities. Computed tomography and microCT analysis show abundant small airway obstruction, starting from the fifth generation of airway branching and affecting up to 40-70% of airways. The pathogenesis of BOS remains unclear. It is a multifactorial syndrome that leads to pathological tissue changes and clinical manifestations. Because BOS is associated with the worst long-term survival in LTx patients, many studies are focused on the early identification of BOS. Markers may be useful for diagnosis and for understanding the molecular and immunological mechanisms involved in the onset of BOS. Diagnostic and predictive markers of BOS have also been investigated in various biological materials, such as blood, BAL, lung tissue and extracellular vesicles. The aim of this review was to evaluate the scientific literature on markers of BOS after lung transplant. We performed a systematic review to find all available data on potential prognostic and diagnostic markers of BOS.

The value of fractional exhaled nitric oxide in occupational diseases - a systematic review

Fractional exhaled nitric oxide (FeNO) is a non-invasive biomarker of respiratory tract inflammation, originally designated to identify eosinophilic airway inflammation and to predict steroid response. The main field of application of this biomarker is asthma, but FeNO has also been used for other allergic and non-allergic pulmonary disorders such as chronic obstructive pulmonary disease, hypersensitivity pneumonitis and interstitial lung disease. A substantial part of respiratory diseases are related to work, and FeNO, a safe and easy measure to conduct, is a potential valid examination in an occupational setting.

This systematic review assesses the value of measuring FeNO related to three types of airborne exposures: allergens, irritants, and respiratory particles inhaled during occupational activities. The review covers results from longitudinal and observational clinical studies, and highlights the added value of this biomarker in monitoring effects of exposure and in the diagnostic criteria of occupational diseases. This review also covers the possible significance of FeNO as an indicator of the efficacy of interventions to prevent work-related respiratory diseases.

Initially, 246 articles were identified in PUBMED and SCOPUS. Duplicates and articles which covered results from the general population, symptoms (not disease) related to work, non-occupational diseases, and case reports were excluded. Finally, 39 articles contributed to this review, which led to the following conclusions:

a) For occupational asthma there is no consensus on the significant value of FeNO for diagnosis, or on the magnitude of change needed after specific inhalation test or occupational exposure at the workplace. There is some consensus for the optimal time to measure FeNO after exposure, mainly after 24 h, and FeNO proved to be more sensitive than spirometry in measuring the result of an intervention. b) For other occupational obstructive respiratory diseases, current data suggests performing the measurement after the work shift. c) For interstitial lung disease, the evaluation of the alveolar component of NO is probably the most suitable.

Significance of alveolar nitric oxide concentration in the airway of patients with organizing pneumonia after allogeneic hematopoietic stem cell transplantation

Organizing pneumonia (OP) is a complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and a manifestation of peripheral airway/alveolar inflammation. Recently, alveolar nitric oxide concentration (Calv) has been revealed as a noninvasive marker of peripheral airway inflammation; however, whether Calv levels are associated with OP and peripheral airway in patients after allo-HSCT remains unclear. Herein, we evaluated whether Calv levels could reflect the presence of OP and structural airway changes in patients after allo-HSCT. We measured the eNO levels of 38 patients (6 with OP and 32 without OP) who underwent allo-HSCT. Three-dimensional computed tomography (CT) analysis of the airway was performed in 19 patients. We found that in patients with OP, Calv levels were significantly higher than in those without OP (10.6 vs. 5.5 ppb, p < 0.01). Receiver-operating characteristic analyses revealed a Calv cut-off value for OP detection of 10.2 ppb. No significant differences in the patient characteristics, except for the presence of OP (p < 0.01), were noted between the two groups stratified by the Calv cut-off value. Three-dimensional CT images of the airway revealed gradually increasing positive correlations between Calv levels and airway wall area of the third-, fourth-, and fifth-generation bronchi (r = 0.20, 0.31, 0.38; p = 0.42, 0.19, 0.038, respectively), indicating that Calv levels are strongly correlated with the wall thickness of the distal bronchi. Our results suggest that the Calv level may be a useful noninvasive detectable marker for OP after an allo-HSCT.

Improved prediction of asthma exacerbations by measuring distal airway inflammation

Introduction

Partitioning parameters measured from exhaled nitric oxide, such as the alveolar concentration of nitric oxide (CalvNO), may provide better predictors of future asthma exacerbation than exhaled nitric oxide fraction at an expiratory flow rate of 50 mL·s−1 (FENO50). We aimed to determine whether any partitioned nitric oxide parameters were more closely associated than FENO50 with subsequent asthma exacerbations.

Methods

68 asthmatic children (mean±sd age 9.0±2.4 years) were followed prospectively (134 visits) and exacerbations were recorded. Childhood Asthma Control Test (cACT), spirometry, FENO50, CalvNO, bronchial flux of nitric oxide (JawNO), transfer factor of nitric oxide (DawNO) and airway wall concentration of nitric oxide (CawNO) were measured.

Results

No exacerbation was recorded in 99 visits (Group 1) and an exacerbation was recorded in 35 visits (Group 2). The median (range) FENO50, JawNO, CalvNO, DawNO and CawNO of Group 1 versus Group 2: 12.7 (4–209) versus 13.5 (3.8–149.9) ppb, 715 (10–12 799) versus 438 (40–7457) pL·s−1, 3.4 (0.2–10.8) versus 5.2 (1.7–23.6) ppb, 38.3 (0.2–113.3) versus 38 (1.3–144.5) pL·s−1·ppb−1 and 26.8 (4.1–2163) versus 29.9 (5.5–3054) ppb, respectively. Other than for CalvNO (p<0.001), there was no difference between the two groups. CalvNO >7 ppb predicted asthma exacerbation with specificity 90.9% and positive likelihood ratio (LR) 3.1. Conversely, CalvNO <4 ppb excluded an exacerbation with sensitivity 71.4% and negative LR 0.48. An increase of CalvNO by 0.5 ppb between visits could also predict an exacerbation with sensitivity 92%, specificity 92%, positive LR 11.8 and negative LR 0.08.

Conclusions

Assessment of CalvNO improved prediction of subsequent exacerbation, highlighting the importance of distal inflammation in asthma outcomes in children.

Clinical implications of concentration of alveolar nitric oxide in asthmatic and non-asthmatic subacute cough

Asthma is an important cause of subacute cough. The concentration of alveolar nitric oxide (CANO) is a sensitive inflammatory indicator in peripheral airways, and it has received much less attention than the fraction of exhaled nitric oxide (FeNO₅₀). The main objective of this study was to explore the correlation between CANO and clinical parameters in asthmatic and non-asthmatic subacute cough, which might promote understanding of the clinical utility of CANO in these special patient populations. 155 patients with subacute cough were included consecutively, of which 25 were diagnosed as asthmatic. Data for demographic characteristics, FeNO₅₀, CANO, baseline spirometry, bronchial provocation test (or bronchodilation test) and response dose ratio (RDR) were collected. Differences between the asthmatic and non-asthmatic groups were analyzed. Spearman's correlation coefficient (ρ) was used to evaluate the correlation between FeNO₅₀, CANO and other clinical parameters. In patients with subacute cough, baseline CANO values did not differ between asthmatic and non-asthmatic patients (4.4(1.3, 11.4) versus 4.0(2.1, 6.8) ppb,P> 0.05). Besides, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. For asthmatic subacute cough, CANO was inversely correlated with FEV₁/FVC (ρ= -0.69,P< 0.01) and small airway parameters including MEF25 (ρ= -0.47,P< 0.05) and MMEF (ρ= -0.45,P< 0.05). For non-asthmatic subacute cough, CANO was inversely correlated with MEF25 (ρ= -0.19,P< 0.05) and RDR (ρ= -0.21,P< 0.05). In subacute cough, asthmatic and non-asthmatic patients had similar values of baseline CANO. In both asthmatic and non-asthmatic subacute cough, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. A low CANO value in non-asthmatic subacute cough corresponded to a higher value of RDR, which implied a stronger tendency towards airway responsiveness.

IL-17 Promotes Nitric Oxide Production in Non-Small-Cell Lung Cancer

Introduction: Lung cancer is the second most frequent malignancy worldwide, but its aetiology is still unclear. Inflammatory cytokines and Th cells, including Th17, are now emerging as being involved in NSCLC pathways, thus postulating a role of IL-17 in tumour angiogenesis by stimulating the vascular endothelial growth factor and the release of nitric oxide. Despite the fact that many biomarkers are used for chest malignancy diagnosis, data on FeNO levels and inflammatory cytokines in NSCLC are still few. Our study aimed to evaluate the relationship between pulmonary nitric oxide production and VEGF and Th17-related cytokines in the EBC of patients affected by early-stage NSCLC. Methods: FeNO measurement and lung function tests were performed in both patients affected by NCSLC and controls; EBC samples were also taken, and Th1 (IL-1, IL-6, IL-12, IFN-g, TNF-a), Th17 (IL-17, IL-23) and Th2 (IL-4, IL-5, IL-13) related cytokines were measured. Results: Th1 and Th17-related cytokines in EBC, except for IFN-gamma and TNF-alpha, were significantly higher in patients than in healthy controls, whereas no differences were seen for Th2-related cytokines. FeNO at the flow rate of 50 mL/s, JawNO and CalvNO levels were significantly higher in patients affected by NSCLC compared to controls. Significant correlations were found between FeNO 50 mL/s and IL-17, IL-1 and VEGF. JawNO levels positively correlated with IL-6, IL-17 and VEGF. No correlations were found between FeNO and Th2-related cytokines. Conclusion: This is the first report assessing a relationship between FeNO levels and Th17-related cytokines in the EBC of patients affected by early-stage NSCLC. IL-17, which could promote angiogenesis through the VEGF pathway, might be indirectly responsible for the increased lung production of NO in patients with NSCLC.

Hierarchical Bayesian estimation of covariate effects on airway and alveolar nitric oxide

Exhaled breath biomarkers are an important emerging field. The fractional concentration of exhaled nitric oxide (FeNO) is a marker of airway inflammation with clinical and epidemiological applications (e.g., air pollution health effects studies). Systems of differential equations describe FeNO—measured non-invasively at the mouth—as a function of exhalation flow rate and parameters representing airway and alveolar sources of NO in the airway. Traditionally, NO parameters have been estimated separately for each study participant (Stage I) and then related to covariates (Stage II). Statistical properties of these two-step approaches have not been investigated. In simulation studies, we evaluated finite sample properties of existing two-step methods as well as a novel Unified Hierarchical Bayesian (U-HB) model. The U-HB is a one-step estimation method developed with the goal of properly propagating uncertainty as well as increasing power and reducing type I error for estimating associations of covariates with NO parameters. We demonstrated the U-HB method in an analysis of data from the southern California Children’s Health Study relating traffic-related air pollution exposure to airway and alveolar airway inflammation.

Effect of exhalation flow rates and level of nitric oxide output on accuracy of linear approximation of pulmonary nitric oxide dynamics

The method of Tsoukias and George (T and G) is a commonly used linear approximation of pulmonary nitric oxide (NO) dynamics that can be used to calculate bronchial NO output (J_awNO) and alveolar NO concentration (C_ANO). We aimed to investigate how flow rate range in exhaled NO measurements and levels of pulmonary NO parameters affect the accuracy of the T and G method. This study has three parts. (a) A theoretical part demonstrating how different exhalation flow rates and NO parameter levels affect the accuracy of the T and G method, (b) testing how exhalation flow rate range affects the method in a sample of asthmatic and healthy subjects, and (c) a meta-analysis of published literature to test whether minimum flow rate has an association with the NO parameter values. We found that both the chosen exhalation flow rates and magnitude of the pulmonary NO parameters affect the accuracy of the T and G method. Underestimation ofJ_awNO increased with lower flow rates and higher bronchial diffusion factor of NO (D_awNO), while overestimation of C_ANO increased with higher D_awNO and bronchial wall NO concentration (C_awNO) and lower C_ANO. Of the NO parameters, C_ANO was the most prone to bias and high D_awNO was the most significant factor causing the bias. Furthermore, we found that using 40 ml s^-1as the lowest flow rate in our sample and 50 ml s^-1in the meta-analysis compared to 100 ml s^-1resulted in higher C_ANO, but J_awNO was not statistically significantly affected. We have provided objective evidence that not only the flow rates used but also the magnitude of NO output in the test subjects affect the accuracy of the T and G method. We suggest that flow rates below 100 ml s^-1should not be used with the T and G method to maintain accuracy.

High alveolar nitric oxide is associated with steeper lung function decline in foundry workers

Occupational dust exposure induces inflammatory responses that often precede the onset of clinical disease. Inflammation in the peripheral part of the lung can be demonstrated by measuring the alveolar NO concentration (C_ANO) in exhaled breath. The aim of the study was to assess whether cumulative dust exposure affects the change in C_ANO during follow-up and whether baseline C_ANO can predict an impairment in lung function during follow-up in foundry workers. We examined 74 dust-exposed and 42 nonexposed foundry workers and measured C_ANO and lung function at baseline and after 7 years of follow-up. An increase in C_ANO during the follow-up period was positively associated with cumulative dust exposure in foundry work (p= 0.035). Furthermore, a higher baseline C_ANO was associated with an accelerated decline in the forced vital capacity (FVC) during the follow-up period (absolute decrease in FVCp= 0.021, relative decrease in FVCp= 0.017). Higher cumulative dust exposure in foundry work is associated with a greater increase in C_ANO during follow-up, suggesting ongoing pulmonary inflammation in these subjects. Importantly, a high baseline C_ANO is associated with an accelerated decline in lung function, suggesting that C_ANO measurements might serve as a screening tool for high-risk workers.

Clinical Utility of Central and Peripheral Airway Nitric Oxide in Aging Patients with Stable and Acute Exacerbated Chronic Obstructive Pulmonary Disease

Purpose

Exhaled nitric oxide has been used as a marker of airway inflammation. The NO concentration in the central and peripheral airway/alveolar can be measured by a slow and fast exhalation flow rate to evaluate inflammation in different divisions within the respiratory tract. We hypothesized that FeNO₂₀₀ (exhaled NO at a flow rate of 200mL/s) could be used as an evaluation tool for peripheral airway/alveolar inflammation and corticosteroid therapy in chronic obstructive pulmonary disease (COPD) patients.

Methods

We recruited 171 subjects into the study: 73 healthy controls, 59 stable COPD patients, and 39 acute exacerbations of COPD (AECOPD) patients. Exhaled nitric oxide (FeNO₅₀ (exhaled NO at a flow rate of 50mL/s)), FeNO₂₀₀ and CaNO (peripheral concentration of NO/alveolar NO) and clinical variables including pulmonary function, COPD Assessment Test (CAT), C-reactive protein concentration (CRP) and circulating eosinophil count were measured among the recruited participants. FeNO_50, FeNO₂₀₀ and CaNO were repeatedly evaluated in 39 AECOPD patients after corticosteroid treatment.

Results

FeNO₂₀₀ was significantly higher in stable COPD and AECOPD patients than in healthy controls. Nevertheless, CaNO could not differentiate COPD from healthy controls. No correlation was found between circulating eosinophil counts or FEV1 and exhaled nitric oxide (FeNO_50, FeNO₂₀₀, CaNO) in COPD patients. For AECOPD patients, 64% of patients had eosinophil counts >100 cells/µL; 59% of patients had FeNO₂₀₀ >10 ppb; only 31% of patients had FeNO₅₀ > 25 ppb. Among AECOPD patients, the high FeNO₅₀ and FeNO₂₀₀ groups’ levels were significantly lower than their baseline levels, and significant improvements in CAT were seen in the two groups after corticosteroid treatment. These implied a good corticosteroid response in AECOPD patients with FeNO₂₀₀>10ppb.

Conclusion

FeNO₂₀₀ is a straightforward and feasible method to evaluate the peripheral NO concentration in COPD. FeNO200 can be a type 2 inflammation biomarker and a useful tool for predicting corticosteroid therapy in COPD.

Clinical Values of Nitric Oxide Parameters from the Respiratory System

BACKGROUND

Fractional exhaled nitric oxide (FENO) concentration reliably reflects central airway inflammation, but it is not sensitive to changes in the NO dynamics in the lung periphery. By measuring FENO at several different flow rates one can estimate alveolar NO concentration (C_ANO), bronchial NO flux (J_awNO), bronchial wall NO concentration (C_awNO) and the bronchial diffusivity of NO (D_awNO).

OBJECTIVE

We aimed to describe the current knowledge and clinical relevance of NO parameters in different pulmonary diseases.

METHODS

We conducted a systematic literature search to identify publications reporting NO parameters in subjects with pulmonary or systemic diseases affecting the respiratory tract. A narrative review was created for those with clinical relevance.

RESULTS

Estimation of pulmonary NO parameters allows for differentiation between central and peripheral inflammation and a more precise analysis of central airway NO output. C_ANO seems to be a promising marker of parenchymal inflammation in interstitial lung diseases and also a marker of tissue damage and altered gas diffusion in chronic obstructive pulmonary disease and systemic diseases affecting the lung. In asthma, C_ANO can detect small airway involvement left undetected by ordinary FENO measurement. Additionally, C_awNO and D_awNO can be used in asthma to assess if FENO is increased due to enhanced inflammatory activity (increased C_awNO) or tissue changes related to bronchial remodelling (altered D_awNO).

CONCLUSION

NO parameters may be useful for diagnosis, prediction of disease progression and prediction of treatment responses in different parenchymal lung and airway diseases. Formal trials to test the added clinical value of NO parameters are needed.

Small airways in asthma: from bench-to-bedside

INTRODUCTION

Historically, asthma was considered a disease predominantly of the large airways, but gradually small airways have been recognized as the major site of airflow obstruction. Small airway dysfunction (SAD) significantly contributes to the pathophysiology of asthma and it is present across all asthma severities. Promising pre-clinical findings documented enhanced beneficial effects of combination therapies on small airways compared to monocomponents, thus it was questioned whether this could translate into further clinical implications from bench-to-bedside. The aim of this review was to systematically assess the state of the art of small airway involvement in asthma, especially in response to different pharmacological treatments acting on the respiratory system.

EVIDENCE ACQUISITION

A comprehensive literature search was performed in MEDLINE for randomized controlled trials (RCTs) characterizing the impact on small airways of different pharmacological treatments acting on the respiratory system. The results were extracted and reported via qualitative synthesis.

EVIDENCE SYNTHESIS

Overall, 63 studies were identified from the literature search, whereas 23 RCTs met the inclusion criteria. Evidence confirms that both drug particle size and the type of inhalation devices represent two of the most important variables for an effective peripheral lung distribution.

CONCLUSIONS

Despite the numerous methodological tools to detect SAD, there is still no gold standard diagnostic method to assess small airways, especially in severe asthma. Further research should be directed to improve primary and secondary prevention strategies by supporting the combined approach of different non-invasive techniques for an early detection of peripheral abnormalities and optimization of asthma therapy.

Monitoring of endogenous nitric oxide exhaled by pig lungs during ex-vivo lung perfusion

In the context of organ shortage for transplantation, new criteria for better organ evaluation should be investigated. Ex-Vivo Lung Perfusion (EVLP) allows extra-corporal lung re-conditioning and evaluation, under controlled parameters of the organ reperfusion and mechanical ventilation. This work reports on the interest of exhaled gas analysis during the EVLP procedure. After a one-hour cold ischemia, the endogenous gas production by an isolated lung of nitric oxide and carbon monoxide is simultaneously monitored in real time. The exhaled gas is analysed with two very sensitive and selective laser spectrometers developed upon the technique of optical-feedback cavity-enhanced absorption spectroscopy. Exhaled gas concentration measured for an ex-vivo lung is compared to the corresponding production by the whole living pig, measured before euthanasia. On-line measurements of the fraction of nitric oxide in exhaled gas (FENO) in isolated lungs are reported here for the first time, allowing to resolve the respiratory cycles. In this study, performed on 9 animals, FENO by isolated lungs range from 3.3 to 10.6 ppb with a median value of 4.4 ppb. Pairing ex-vivo lung and pig measurements allows to demonstrate a systematic increase of FENO in the ex-vivo lung as compared to the living animal, by a factor of 3 ± 1.2. Measurements of the fraction of carbon monoxide in exhaled gas (FECO) confirm levels recorded during previous studies driven to evaluate FECO as a potential marker of ischemia reperfusion injuries. FECO production by ex-vivo lungs ranges from 0.31 to 2.3 ppm with a median value of 0.8 ppm. As expected, these FECO values are lower than the production by the corresponding whole pig body, by a factor of 6.9 ± 2.7.

Modeling of the Transport and Exchange of a Gas Species in Lungs With an Asymmetric Branching Pattern. Application to Nitric Oxide

Over the years, various studies have been dedicated to the mathematical modeling of gas transport and exchange in the lungs. Indeed, the access to the distal region of the lungs with direct measurements is limited and, therefore, models are valuable tools to interpret clinical data and to give more insights into the phenomena taking place in the deepest part of the lungs. In this work, a new computational model of the transport and exchange of a gas species in the human lungs is proposed. It includes (i) a method to generate a lung geometry characterized by an asymmetric branching pattern, based on the values of several parameters that have to be given by the model user, and a method to possibly alter this geometry to mimic lung diseases, (ii) the calculation of the gas flow distribution in this geometry during inspiration or expiration (taking into account the increased resistance to the flow in airways where the flow is non-established), (iii) the evaluation of the exchange fluxes of the gaseous species of interest between the tissues composing the lungs and the lumen, and (iv) the computation of the concentration profile of the exchanged species in the lumen of the tracheobronchial tree. Even if the model is developed in a general framework, a particular attention is given to nitric oxide, as it is not only a gas species of clinical interest, but also a gas species that is both produced in the walls of the airways and consumed within the alveolar region of the lungs. First, the model is presented. Then, several features of the model, applied to lung geometry, gas flow and NO exchange and transport, are discussed, compared to existing works and notably used to give new insights into experimental data available in the literature, regarding diseases, such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease.

Extended nitric oxide analysis in patients with chronic rhinosinusitis with nasal polyps, with or without associated asthma

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex inflammatory disease highly impacting patient's quality of life, and associated with lower airway inflammation often evolving into asthma. Exhaled nitric oxide (FE_NO) is a non-invasive tool to assess Type 2 airway inflammation and its extended analysis allows to differentiate between alveolar concentration (CalvNO) and bronchial output (JawNO). It is also possible to assess the sino-nasal production of nitric oxide (nNO). We studied extended nitric oxide production in patients with CRSwNP with or without associated asthma. Consecutive adult patients with CRSwNP, with or without asthma, and 15 healthy controls were enrolled. Exclusion criteria were: smoking, uncontrolled asthma, recent upper or lower airway infections and oral corticosteroid therapy in the 4 weeks preceding clinical evaluation. Patients' demographic and clinical data were collected; patients underwent pulmonary function tests and extended nitric oxide analysis including nasal nNO assessment. A total of 125 subjects were enrolled (15 healthy controls; 69 with CRSwNP and asthma, and 41 with CRSwNP only). FE_NO, JawNO and CalvNO values were higher, while nNO was lower, in all patients with CRSwNP compared to healthy controls; no difference was found in CalvNO between patients with concomitant asthma and non-asthmatic subjects; in asthmatic patients, FE_NO and JawNO were significantly higher, while nNO values was lower, compared to patients with CRSwNP only. These results suggest that CRSwNP could be the first manifestation of a more complex systemic inflammatory pathology driven by Type 2 inflammation. An 'inflammatory gradient' hypothesis could describe a pattern of inflammation in CRSwNP patients that starts distally in the alveoli. Finally, our study indirectly reinforces the concept that novel biological drugs could become valid therapeutic options for nasal polyposis.

Onset of action of inhaled glucocorticoids on bronchial and alveolar nitric oxide output

Fractional exhaled nitric oxide (F_ENO) is a marker of airway inflammation. Measuring F_ENO at multiple flow rates enables calculation of NO parameters: bronchial NO output (J _awNO), bronchial wall (C _awNO) and alveolar (C _ANO) NO concentrations, and bronchial diffusion factor of NO (D _awNO). F_ENO is known to rapidly reduce after the commencement of inhaled corticosteroid (ICS) treatment. However, little is known on the effect of ICS on the other NO parameters. We assessed (1) the onset of action of ICS treatment on the NO parameters and (2) whether the changes in bronchial NO output are due to changes in bronchial wall NO concentration or diffusion factor. F_ENO and other NO parameters were measured at baseline and after 1, 3 and 7 d of treatment with inhaled fluticasone propionate 250 μg b.i.d. in 23 allergic children with a history of asthma-like symptoms. There was a decrease in J _awNO (from 680 (244/1791) (median (1st/3rd quartile)) to 357 (165/753) pl s^-1, p < 0.001) and F_ENO₅₀( from 13.8 (7.5/35) to 8.3 (5.36/17.0) ppb, p < 0.001) in 3 d from the first dose of ICS. Also, C _awNO seemed to reduce after 3 d (from 171 (89/328) to 79 (54/157) ppb, p = 0.041), while D _awNO remained unchanged. Furthermore, C _ANO reduced during the 7 d treatment (from 3.0 (2.0/5.0) to 2.3 (1.9/2.6) ppb, p = 0.004). ICS treatment reduced F_ENO₅₀ and J _awNO rapidly and the decline was caused by decreased bronchial wall NO concentration while bronchial NO diffusion factor remained unchanged. These findings suggest that C _awNO could be a more specific marker of airway inflammation and treatment response than J _awNO or F_ENO₅₀, which are both determined also by D _awNO that seems to be resistant to the treatment with ICS.

Occupation versus environmental factors in hypersensitivity pneumonitis: population attributable fraction

Background

Despite well-documented case series of hypersensitivity pneumonitis (HP), epidemiological data delineating relative contributions of risk factors are sparse. To address this, we estimated HP risk in a case-referent study of occupational and nonoccupational exposures.

Methods

We recruited cases of HP by ICD-9 codes from an integrated healthcare delivery system (IHCDS) and a tertiary medical care centre. We drew referents, matched for age and sex, from the IHCDS. Participants underwent comprehensive, structured telephone interviews eliciting details of occupational and home environmental exposures. We employed a hierarchical analytic approach for data reduction based on the false discovery rate method within clusters of exposures. We measured lung function and selected biomarkers in a subset of participants. We used multivariate logistic regression to estimate exposure-associated odds ratios (ORs) and population attributable fractions (PAFs) for HP.

Results

We analysed data for 192 HP cases (148 IHCDS; 44 tertiary care) and 229 referents. Occupational exposures combined more than doubled the odds of developing HP (OR 2.67; 95% CI 1.73–4.14) with a PAF of 34% (95% CI 21–46%); nonoccupational bird exposure also doubled the HP odds (OR 2.02; 95% CI 1.13–3.60), with a PAF of 12% (3–21%). Lung function and selected biomarkers did not substantively modify the risk estimates on the basis of questionnaire data alone.

Discussion

In a case-referent approach evaluating HP risk, identifiable exposures accounted, on an epidemiological basis, for approximately two in three cases of disease; conversely, for one in three, the risk factors for disease remained elusive.

Occupational and environmental factors account for two in three cases of HP. The contributions of risk factors vary markedly depending on case referral source. This could affect clinical ascertainment of cause and the implementation of preventative actions.https://bit.ly/3feAa6P

Extended Exhaled Nitric Oxide Analysis in Interstitial Lung Diseases: A Systematic Review

Fractional exhaled nitric oxide (FeNO) is a well-known and widely accepted biomarker of airways inflammation that can be useful in the therapeutic management, and adherence to inhalation therapy control, in asthmatic patients. However, the multiple-flows assessment of FeNO can provide a reliable measurement of bronchial and alveolar production of NO, supporting its potential value as biomarker also in peripheral lung diseases, such as interstitial lung diseases (ILD). In this review, we first discuss the role of NO in the pathobiology of lung fibrosis and the technique currently approved for the measurement of maximum bronchial flux of NO (J'awNO) and alveolar concentration of NO (CaNO). We systematically report the published evidence regarding extended FeNO analysis in the management of patients with different ILDs, focusing on its potential role in differential diagnosis, prognostic evaluation and severity assessment of disease. The few available data concerning extended FeNO analysis, and the most common comorbidities of ILD, are explored too. In conclusion, multiple-flows FeNO analysis, and CaNO in particular, appears to be a promising tool to be implemented in the diagnostic and prognostic pathways of patients affected with ILDs.

Accurate real-time FENO expirograms using complementary optical sensors

The fraction of exhaled nitric oxide (F_ENO) is an important biomarker for the diagnosis and management of asthma and other pulmonary diseases associated with airway inflammation. In this study we report on a novel method for accurate, highly time-resolved, real time detection of F_ENO at the mouth. The experimental arrangement is based on a combination of optical sensors for the determination of the temporal profile of exhaled NO and CO₂ concentrations. Breath CO₂ and exhalation flow are measured at the mouth using diode laser absorption spectroscopy (at 2 μm) and differential pressure sensing, respectively. NO is determined in a sidestream configuration using a quantum cascade laser based, cavity-enhanced absorption cell (at 5.2 μm) which simultaneously measures sidestream CO₂. The at-mouth and sidestream CO₂ measurements are used to enable the deconvolution of the sidestream NO measurement back to the at-mouth location. All measurements have a time resolution of 0.1 s, limited by the requirement of a reasonable limit of detection for the NO measurement, which on this timescale is 4.7 ppb (2 σ). Using this methodology, NO expirograms (F_ENOgrams) were measured and compared for eight healthy volunteers. The F_ENOgrams appear to differ qualitatively between individuals and the hope is that the dynamic information encoded in these F_ENOgrams will provide valuable additional insight into the location of the inflammation in the airways and potentially predict a response to therapy. A validation of the measurements at low-time resolution is provided by checking that results from previous studies that used a two-compartment model of NO production can be reproduced using our technology.

Fractional exhaled breath temperature in patients with asthma, chronic obstructive pulmonary disease, or systemic sclerosis compared to healthy controls

Exhaled breath temperature has been suggested to reflect airway inflammation, and it would be plausible to measure the peripheral airway temperature as a correlate to peripheral airway inflammation. This study aims to explore the relative peripheral airway temperature in patients with asthma, chronic obstructive pulmonary disease (COPD) or systemic sclerosis (SSc) compared to healthy controls, and relate to lung function and exhaled nitric oxide.

Sixty-five subjects (16 asthmatics, 18 COPD patients, 17 SSc patients and 14 healthy subjects) performed fractional exhaled breath temperature measurements using a novel device, fractional exhaled NO measurements, spirometry, impulse oscillometry, body plethysmography and CO-diffusion capacity test.

A significant overall difference among all the patient groups was seen in both the Tmax (= peak values of the entire exhalation) and T3max (= peak value of the last fraction of the exhaled volume). A significant difference in T3/T1 ratio (= the ratio of peripheral versus central air temperature) was found between asthmatic subjects and those with COPD or SSc. In addition, T1max (= temperature in the central), T3max (= peripheral airways) and the T3/T1ratio related to several volumetric measurements (both in absolute values and as percent predicted), such as vital capacity, total lung capacity, forced expiratory volume in 1 s, and diffusion capacity.

The temperature ratio of the peripheral versus central airways was lower in patients with COPD or SSc compared to asthmatics, who in turn presented similar levels as the controls. There was also a large overlap between the groups. Overall, the airway temperatures were related to absolute lung volumes, and specifically, the peripheral temperature was related to the gas diffusion capacity (% predicted), suggesting a link to the vascular component.

A Role for Alveolar Exhaled Nitric Oxide Measurement in the Diagnosis of Hepatopulmonary Syndrome

GOALS

The authors sought to characterize predominantly alveolar exhaled nitric oxide (eNO) in hepatopulmonary syndrome (HPS) compared with non-HPS, changes after liver transplantation, and diagnostic properties.

BACKGROUND

HPS is defined by liver disease, intrapulmonary vascular dilatations (IPVDs), and hypoxemia. Rat models and small human studies suggest that NO overproduction may cause IPVDs.

STUDY

A retrospective review of the Canadian HPS Database (2007 to 2017) and prospective eNO measurement (main outcome) in healthy controls (measurement expiratory flow, 200 mL/s). HPS was defined as: (1) liver disease; (2) contrast echocardiography consistent with IPVDs; and (3) partial pressure of arterial oxygen <70 mm Hg with alveolar-arterial gradient >20 mm Hg; subclinical HPS as criteria (1) and (2) only; and no HPS as criterion (1) only. Current smokers and subjects with asthma or pulmonary hypertension were excluded. A linear mixed effects model was used to compare eNO between groups and before and after transplantation.

RESULTS

eNO was 10.4±0.7 ppb in HPS (n=26); 8.3±0.6 ppb in subclinical HPS (n=38); 7.1±1.0 ppb in no HPS (n=15); and 5.6±0.7 ppb in controls (n=30) (P<0.001). eNO decreased from 10.9±0.8 ppb preliver to 6.3±0.8 ppb postliver transplant (n=6 HPS, 6 subclinical HPS) (P<0.001). eNO <6 ppb was 84.4% (73.1% to 92.2%) sensitive and ≥12 ppb was 78.1% (69.4% to 85.3%) specific for HPS (vs. subclinical HPS).

CONCLUSIONS

HPS subjects have higher alveolar eNO than non-HPS subjects, levels normalize with liver transplantation. Applying eNO cutoff values may aid in HPS diagnosis.

Repeatability and variation of the flow independent nitric oxide parameters

INTRODUCTION

Fractional exhaled nitric oxide (F_ENO) is a non-invasive marker of airway inflammation. Measuring F_ENO at several flow rates enables the calculation of flow independent NO-parameters (alveolar NO concentration (C_ANO), bronchial flux of NO (J_awNO), bronchial mucosal NO concentration (C_awNO) and bronchial wall NO diffusion capacity (D_awNO)) that are capable of partitioning the source and release mechanism of NO from the lower respiratory tract. However, the current literature on repeatability and normal variation of the NO-parameters is deficient, and this information is needed to develop the method towards clinical use.

METHODS

We calculated NO-parameters in 28 healthy subjects using two different mathematical methods and used three different study protocols to investigate: (i) repeatability of two consecutive measurements of NO-parameters, (ii) within-day variation of the NO-parameters over one working day and (iii) day-to-day variation of the NO-parameters between consecutive days during course of a working week.

RESULTS

J_awNO was the most repeatable among the NO-parameters, whereas D_awNO and C_awNO were notably least repeatable. C_ANO was higher during the second consecutive measurement (1.22 versus 1.57 ppb, p = 0.017). Both investigated mathematical methods yielded equally repeatable results. J_awNO was slightly higher in the afternoon compared to morning (716 versus 881 pl/s, p = 0.01), but other parameters showed no diurnal variation. Upper 95% limit for the day-to-day difference in the parameters in healthy subjects was about 1.2 ppb in C_ANO, 400 pl/s in J_awNO, 92 ppb in C_awNO and 16 pl/s/ppb in D_awNO.

CONCLUSIONS

This is the first study assessing short-time repeatability of the NO-parameters. Repeatability of the NO-parameters was good and day-to-day variation in NO-parameters was quite low. We recommend scheduling F_ENO-measurements at the same time of day, if possible, and in clinical use variation in NO-parameters above the normal limits found in this study suggest changes in the disease's activity.

Impact of different fixed flow sampling protocols on flow-independent exhaled nitric oxide parameter estimates using the Bayesian dynamic two-compartment model

Exhaled nitric oxide (FeNO) is an established respiratory biomarker with clinical applications in the diagnosis and management of asthma. Because FeNO depends strongly on the flow (exhalation) rate, early protocols specified that measurements should be taken when subjects exhaled at a fixed rate of 50 ml/s. Subsequently, multiple flow (or "extended") protocols were introduced which measure FeNO across a range of fixed flow rates, allowing estimation of parameters including Caw NO and CA NO which partition the physiological sources of NO into proximal airway wall tissue and distal alveolar regions (respectively). A recently developed dynamic model of FeNO uses flow-concentration data from the entire exhalation maneuver rather than plateau means, permitting estimation of Caw NO and CA NO from a wide variety of protocols. In this paper, we use a simulation study to compare Caw NO and CA NO estimation from a variety of fixed flow protocols, including: single maneuvers (30, 50,100, or 300 ml/s) and three established multiple maneuver protocols. We quantify the improved precision with multiple maneuvers and the importance of low flow maneuvers in estimating Caw NO. We conclude by applying the dynamic model to FeNO data from 100 participants of the Southern California Children's Health Study, establishing the feasibility of using the dynamic method to reanalyze archived online FeNO data and extract new information on Caw NO and CA NO in situations where these estimates would have been impossible to obtain using traditional steady-state two compartment model estimation methods.

Serum chitinase-like protein YKL-40 is linked to small airway function in children with asthmatic symptoms

BACKGROUND

Lung function impairment among asthmatic children begins in early life, and biomarkers for identifying this impairment are needed. The chitinase-like protein YKL-40 has been associated with asthma and lung function in adults, but studies in children have yielded conflicting results. We evaluated the potential of YKL-40 and other systemic biomarkers for identifying lung function deficits in children with asthmatic symptoms.

METHODS

We determined the levels of serum YKL-40, periostin, and high-sensitivity C-reactive protein (hs-CRP) from the blood samples of 49 children with asthmatic symptoms. Lung function was assessed with impulse oscillometry (IOS) and spirometry, combined with an exercise challenge and a bronchodilator test. Fractional exhaled nitric oxide was measured at multiple flow rates.

RESULTS

Serum levels of YKL-40 showed significant correlations with most IOS indices at baseline (P = .008-.039), but there was no association between YKL-40 and spirometry parameters. Neither periostin nor hs-CRP were associated with baseline lung function. Children with a significant response in either the exercise challenge or the bronchodilator test had increased serum levels of YKL-40 (P = .003) and periostin (P = .035). YKL-40 correlated significantly with the blood neutrophil count (r_s  = .397, P = .005) but was not associated with biomarkers of eosinophilic inflammation.

CONCLUSION

Serum YKL-40 is a potential biomarker for lung function deficits in children with asthmatic symptoms. These deficits appear to be focused on small airways and may remain undetected with spirometry.

Urinary and exhaled biomarkers of exercise-induced bronchoconstriction in atopic asthmatic children

BACKGROUND

Exercise-induced bronchoconstriction (EIB) reflects poor asthma control. Assessing noninvasive biomarkers associated with EIB could help to monitor patients in the pediatric age.

AIMS

To test exhaled and urinary biomarkers for assessing EIB in atopic asthmatic children.

METHODS

In 45 atopic patients (11.1 ± 1.8 years, 25 males) we measured the fractional exhaled nitric oxide (FE_NO ), its alveolar (CaNO), and bronchial (J'awNO) components corrected for the trumpet shape of the airways and axial NO diffusion (TMAD), concentrations of urinary adenosine and 8-hydroxy-2'-deoxyguanosine (8-OxodG), blood eosinophils count, total immunoglobulin E , skin prick tests, and baseline spirometry before a treadmill exercise challenge. Forty healthy control subjects participated solely to baseline measurements.

RESULTS

Patients yielded higher FE_NO and urinary adenosine concentrations than healthy controls. After the challenge, 18 patients (40%) had EIB; these patients had higher levels of CaNO, CaNO TMAD, and urinary adenosine than patients without EIB. Baseline spirometry, FE _NO , JawNO, JawNO TMAD, urinary 8-OxodG, allergy, and blood eosinophil counts were found similar in both groups. In multiple linear regression, the fall in FEV ₁ was explained by CaNO TMAD, urinary adenosine and blood eosinophil count, whereas the fall in FEF _25-75 was explained by CaNO TMAD and blood eosinophil count. Both CaNO TMAD ≥10.5 ppb and urinary adenosine ≥406 nmol/mmol Cr predicted a fall in FEV ₁ ≥10%, while only CaNO TMAD ≥10.5 ppb predicted a fall in FEF _25-75 ≥26%.

CONCLUSION

Concentrations of peripheral airway NO are complementary with urinary adenosine for assessing EIB and promising tools of asthma control in pediatric patients with the atopic phenotype.

Converting FENO by different flows to standard flow FENO

In clinical practice, assessment of expiratory nitric oxide (FENO ) may reveal eosinophilic airway inflammation in asthmatic and other pulmonary diseases. Currently, measuring of FENO is standardized to exhaled flow level of 50 ml s-1 , since the expiratory flow rate affects the FENO results. To enable the comparison of FENO measured with different expiratory flows, we firstly aimed to establish a conversion model to estimate FENO at the standard flow level, and secondly, validate it in five external populations. FENO measurements were obtained from 30 volunteers (mixed adult population) at the following multiple expiratory flow rates: 50, 30, 100 and 300 ml s-1 , after different mouthwash settings, and a conversion model was developed. We tested the conversion model in five populations: healthy adults, healthy children, and patients with COPD, asthma and alveolitis. FENO conversions in the mixed adult population, in healthy adults and in children, showed the lowest deviation between estimatedF ^ ENO from 100 ml s-1 and measured FENO at 50 mL s-1 : -0·28 ppb, -0·44 ppb and 0·27 ppb, respectively. In patients with COPD, asthma and alveolitis, the deviation was -1·16 ppb, -1·68 ppb and 1·47 ppb, respectively. We proposed a valid model to convert FENO in healthy or mixed populations, as well as in subjects with obstructive pulmonary diseases and found it suitable for converting FENO measured with different expiratory flows to the standard flow in large epidemiological data, but not on individual level. In conclusion, a model to convert FENO from different flows to the standard flow was established and validated.

Flow-independent nitric oxide parameters in asthma: a systematic review and meta-analysis

INTRODUCTION

Fractional exhaled nitric oxide (F_ENO) has been proposed as a non-invasive marker of inflammation in the lungs. Measuring F_ENO at several flow rates enables the calculation of flow independent NO-parameters that describe the NO-exchange dynamics of the lungs more precisely. The purpose of this study was to compare the NO-parameters between asthmatics and healthy subjects in a systematic review and meta-analysis.

METHODS

A systematic search was performed in Ovid Medline, Web of Science, Scopus and Cochrane Library databases. All studies with asthmatic and healthy control groups with at least one NO-parameter calculated were included.

RESULTS

From 1137 identified studies, 33 were included in the meta-analysis. All NO-parameters (alveolar NO concentration (C_ANO), bronchial flux of NO (J_awNO), bronchial mucosal NO concentration (C_awNO) and bronchial wall NO diffusion capacity (D_awNO)) were found increased in glucocorticoid-treated and glucocorticoid-naïve asthma. J_awNO and C_ANO were most notably increased in both study groups. Elevation of D_awNO and C_awNO seemed less prominent in both asthma groups.

DISCUSSION

We found that all the NO-parameters are elevated in asthma as compared to healthy subjects. However, results were highly heterogenous and the evidence on C_awNO and D_awNO is still quite feeble due to only few studies reporting them. To gain more knowledge on the NO-parameters in asthma, nonlinear methods and standardized study protocols should be used in future studies.

Elevated Levels of Alveolar Nitric Oxide May Indicate Presence of Small Airway Inflammation in Patients with Inflammatory Bowel Disease

INTRODUCTION

Pulmonary manifestations of inflammatory bowel disease (IBD), albeit not rare, are largely overlooked in clinical practice. The role of exhaled nitric oxide (eNO) as an established biological marker of airway inflammation compels us to use it as a tool to investigate the exact nature of these manifestations.

METHODS

Fractional eNO (FeNO) was measured in multiple flows, and with the use of a mathematical model, alveolar concentration of NO (C_ANO) and bronchial flux of NO (J_awNO) were assessed in 27 patients with IBD [17 with Crohn's disease (CD) and 10 with ulcerative colitis (UC)] and in 39 healthy controls. Carefully selected criteria were used to exclude patients or healthy controls that presented factors considered to be correlated with eNO measurements. Disease activity was measured in Crohn's patients using the CD activity index (CDAI) score and in UC using the partial Mayo score.

RESULTS

C_ANO was significantly higher in the IBD group, compared to the control group (p < 0.0001). FeNO was significantly increased in patients with IBD (p = 0.023), while there was no statistical significance found regarding levels of J_awNO in patients with IBD (p = 0.106), both compared to controls. There was no significant correlation between any eNO component and markers of disease activity.

CONCLUSIONS

Alveolar concentration of NO is elevated in patients with IBD, regardless of disease activity. This may suggest that subclinical small airway inflammation is present in patients with IBD, even those with mild or inactive disease.

Recent Advances in Inflammation and Treatment of Small Airways in Asthma

Small airways were historically considered to be almost irrelevant in the development and control of pulmonary chronic diseases but, as a matter of fact, in the past few years we have learned that they are not so "silent". Asthma is still a worldwide health issue due to the great share of patients being far from optimal management. Several studies have shown that the deeper lung inflammation plays a critical role in asthma pathogenesis, mostly in these not well-controlled subjects. Therefore, assessing the degree of small airways inflammation and impairment appears to be a pivotal step in the asthmatic patient's management. It is now possible to evaluate them through direct and indirect measurements, even if some obstacles still affect their clinical application. The success of any treatment obviously depends on several factors but reaching the deeper lung has become a priority and, for inhaled drugs, this is strictly connected to the molecule's size. The aim of the present review is to summarize the recent evidence concerning the small airway involvement in asthma, its physiopathological characteristics and how it can be evaluated in order to undertake a personalized pharmacological treatment and achieve a better disease control.

Comparison of inducible nitric oxide synthase mRNA expression in different airway portions and association with nitric oxide parameters from patients with asthma

Background

Fractional exhaled nitric oxide concentration (FeNO) is widely used to support diagnosis and monitoring of bronchial asthma (BA). Tsoukias and George proposed a two‐compartment model (2CM) for assessing the alveolar concentration of NO, referred to as CANO(2CM), while Condorelli et al proposed a model based on the trumpet shape of the airway tree and axial diffusion (TMAD), referred to as CANO(TMAD). In addition, Högman et al proposed non‐linear model, referred to as CANO(non‐linear).

Objective

We examined associations between the expression of inducible nitric oxide synthase (iNOS) mRNA in airway cells (ACs) by bronchoscopy and NO‐parameters calculated by the three methods and identified which of them accurately reflected expression of iNOSmRNA from different airway portions.

Methods

We retrospectively analysed data of 18 patients with stable, mild‐moderate asthma, including 10 steroid‐naïve BA (snBA) patients. Samples were obtained from airway brushings and bronchoalveolar lavage (BAL). Expressions of iNOS protein in tissue samples were evaluated by immunostaining. The iNOSmRNA in ACs was measured by qPCR. NO‐parameters calculated by the three methods above and evaluated whether they were associated with iNOSmRNA in ACs derived from proximal (2nd carina), distal (10‐15th) airways and alveolar regions.

Results

Immunostaining revealed expression of iNOS proteins mainly in epithelial cells in the airways, while it was mainly expressed in macrophages in the alveolar region in the snBA group. The iNOSmRNA expression was increased in both proximal and distal ACs in the snBA group compared with steroid‐treated BA group (stBA). CANO(2CM) negatively associated with FEV₁ (%predicted) and also associated with iNOSmRNA in distal ACs significantly. However, CANO(TMAD) and CANO(non‐linear) showed no correlation with lung function nor iNOSmRNA expression in any portions of ACs.

Conclusions

These results suggested that CANO(2CM) reflected distal airway inflammation in steroid‐naïve asthma.

Small Airway Dysfunction in Children With Controlled Asthma

INTRODUCTION

Asthma is characterized by chronic inflammation of the central and distal airways. The aim of this study was to assess the small airway (SA) of children with moderate-severe asthma with normal FEV1.

METHODS

This was an open-label, prospective, observational, cross-sectional study with consecutive inclusion of patients with moderate-severe asthma, receiving standard clinical treatment, with normal baseline FEV₁. We determined multiflow FEno (CAno), oscillatory resistance and reactance (R5-R20, X5), forced spirometry (FEV1, FEF_25-75), total body plethysmography (RV/TLC) and bronchodilation test. SA involvement was defined as: CAno>4.5 ppb, R5-R20>0.147kPa/L/s, X5<-0.18kPa/L, FEF_25-75<-1.65 z-score, RV/TLC>33%. Poor asthma control was defined as ≤ 19 points on the ACT questionnaire or ≤ 20 on the c-ACT.

RESULTS

In a cohort of 100 cases, 76 had moderate asthma and 24 had severe asthma; 71 children were classified as poorly controlled and 29 were well-controlled. In total, 77.78% of the group with all the correct determinations (n=72) showed ≥ 1 altered SA parameter and 48.61% ≥ 2 parameters. There were no differences between well-controlled or poorly controlled cases.

CONCLUSIONS

Children with moderate-severe asthma, with normal FEV₁, show a phenotype of dysfunctional SA. In our series, the evaluation of SA using the techniques described above did not provide information on disease control.

Breath biomarkers in idiopathic pulmonary fibrosis: a systematic review

BACKGROUND

Exhaled biomarkers may be related to disease processes in idiopathic pulmonary fibrosis (IPF) however their clinical role remains unclear. We performed a systematic review to investigate whether breath biomarkers discriminate between patients with IPF and healthy controls. We also assessed correlation with lung function, ability to distinguish diagnostic subgroups and change in response to treatment.

METHODS

MEDLINE, EMBASE and Web of Science databases were searched. Study selection was limited to adults with a diagnosis of IPF as per international guidelines.

RESULTS

Of 1014 studies screened, fourteen fulfilled selection criteria and included 257 IPF patients. Twenty individual biomarkers discriminated between IPF and controls and four showed correlation with lung function. Meta-analysis of three studies indicated mean (± SD) alveolar nitric oxide (CalvNO) levels were significantly higher in IPF (8.5 ± 5.5 ppb) than controls (4.4 ± 2.2 ppb). Markers of oxidative stress in exhaled breath condensate, such as hydrogen peroxide and 8-isoprostane, were also discriminatory. Two breathomic studies have isolated discriminative compounds using mass spectrometry. There was a lack of studies assessing relevant treatment and none assessed differences in diagnostic subgroups.

CONCLUSIONS

Evidence suggests CalvNO is higher in IPF, although studies were limited by small sample size. Further breathomic work may identify biomarkers with diagnostic and prognostic potential.

A Dynamic Model of Rescuer Parameters for Optimizing Blood Gas Delivery during Cardiopulmonary Resuscitation

Introduction

The quality of cardiopulmonary resuscitation (CPR) has been shown to impact patient outcomes. However, post-CPR morbidity and mortality remain high, and CPR optimization is an area of active research. One approach to optimizing CPR involves establishing reliable CPR performance measures and then modifying CPR parameters, such as compressions and ventilator breaths, to enhance these measures. We aimed to define a reliable CPR performance measure, optimize the CPR performance based on the defined measure and design a dynamically optimized scheme that varies CPR parameters to optimize CPR performance.

Materials and Methods

We selected total blood gas delivery (systemic oxygen delivery and carbon dioxide delivery to the lungs) as an objective function for maximization. CPR parameters were divided into three categories: rescuer dependent, patient dependent, and constant parameters. Two optimization schemes were developed using simulated annealing method: a global optimization scheme and a sequential optimization scheme.

Results and Discussion

Variations of CPR parameters over CPR sequences (cycles) were analyzed. Across all patient groups, the sequential optimization scheme resulted in significant enhancement in the effectiveness of the CPR procedure when compared to the global optimization scheme.

Conclusions

Our study illustrates the potential benefit of considering dynamic changes in rescuer-dependent parameters during CPR in order to improve performance. The advantage of the sequential optimization technique stemmed from its dynamically adapting effect. Our CPR optimization findings suggest that as CPR progresses, the compression to ventilation ratio should decrease, and the sequential optimization technique can potentially improve CPR performance. Validation in vivo is needed before implementing these changes in actual practice.

Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women

Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justa stoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO).

A suitable protocol for measuring alveolar nitric oxide in asthma with differing severity to assess peripheral airways inflammation

OBJECTIVE

Extended nitric oxide (NO) analysis offers the partitioned monitoring of inflammation in central and peripheral airways. Different mathematical models are used to estimate pulmonary NO dynamics in asthma with variable results and limitations. We aimed to establish a protocol for extended NO analysis in patients with differing asthma severity.

METHODS

Forty patients with stable asthma and 25 matched control subjects were recruited. Exhaled NO was measured at constant flow rates between 10 and 300 mL/s. Twelve controls performed NO measurements weekly for 4 weeks.

RESULTS

The proportions of patients with technically acceptable measurements at 10-30-50-100-150-200-250-300 mL/s exhalation flow rates were 8-58-100-98-98-95-90-80%, respectively. Alveolar NO (CANO) and total flux of NO in the conducting airways (JawNO) were calculated with the linear method from NO values measured at 100-150-200-250 mL/s exhalation flows. The mean intrasubject bias for JawNO and CANO in controls was 0.16 nL/s and 0.85 ppb, respectively. Both JawNO (1.31/0.83-2.97/vs. 0.70/0.54-0.87/nL/s, p < 0.001) and CANO (4.08/2.63-7.16/vs. 2.42/1.83-2.89/ppb, p < 0.001) were increased in patients with asthma compared to controls. In patients, CANO correlated with RV/TLC (r = 0.58, p < 0.001), FEF_25-75% (p = 0.02, r = -0.36) and DL,CO (r = -0.46, p = 0.004). JawNO was not related to lung function parameters.

CONCLUSIONS

Calculation of alveolar NO concentration with the linear method from values obtained at medium flow rates (100-250 mL/s) is feasible even in asthmatic patients with severe airflow limitation and may provide information on small airways dysfunction in asthma.

Influence of mouthwashes on extended exhaled nitric oxide (FENO) analysis

Fractional exhaled nitric oxide (F_ENO) is used to assess eosinophilic inflammation of the airways. F_ENO values are influenced by the expiratory flow rate and orally produced NO. We measured F_ENO at four different expiratory flow levels after two different mouthwashes: tap water and carbonated water. Further, we compared the alveolar NO concentration (C_ANO), maximum airway NO flux (J'_awNO) and airway NO diffusion (D_awNO) after these two mouthwashes. F_ENO was measured in 30 volunteers (healthy or asthmatic) with a chemiluminescence NO-analyser at flow rates of 30, 50, 100 and 300 mL/s. A mouthwash was performed before the measurement at every flow rate. The carbonated water mouthwash significantly reduced F_ENO compared to the tap water mouthwash at all expiratory flows: 50 mL/s (p < .001), 30 mL/s (p = .001), 100 mL/s (p < .001) and 300 mL/s (p = .004). J'_awNO was also significantly reduced (p = .017), however, there were no significant differences in C_ANO and D_awNO. In conclusion, a carbonated water mouthwash can significantly reduce oropharyngeal NO compared to a tap water mouthwash at expiratory flows of 30-300 mL/s without affecting the C_ANO and D_awNO. Therefore, mouthwashes need to be taken into account when comparing F_ENO results.

Exhaled Nitric Oxide: An Update

Fractional concentration of exhaled nitric oxide (FENO) is a biomarker used to identify allergic airway inflammation. Because it is noninvasive and easy to obtain, its utility has been studied in the diagnosis and management of several respiratory diseases. Much of the research has been done in asthma, and many studies support the use of FENO in aiding diagnosing asthma, predicting steroid responsiveness, and preventing exacerbations by guiding medication dosage and assessing adherence.