Exhaled nitric oxide

Fractional exhaled NO in a metalworking occupational cohort

PURPOSE

Secondary metalworking carries exposure to relatively heavy levels of respirable particulate. We investigated the extent to which metalworking is associated with increased exhaled nitric oxide (FeNO), an established inflammatory biomarker.

METHODS

We studied 80 metalworking factory employees in Kazakhstan. Informed by industrial hygiene data, we categorized them into three groups: (1) machine operators (41%); (2) welders or assemblers (33%); and (3) all others, including administrative and ancillary staff (26%). Participants completed questionnaires covering occupational history, smoking, home particulate sources, respiratory symptoms, and comorbidities. We measured exhaled carbon monoxide (CO), exhaled fractional nitric oxide (FeNO), and spirometric function. We used mixed-effects modeling to test the associations of occupational group with FeNO, adjusted for covariates.

RESULTS

The median age was 51.5 (interquartile range 20.5) years; 7% were women. Occupational group (p < 0.01), daily current cigarette smoking intensity (p < 0.05), and age (p < 0.05), each was statistically associated with FeNO. Welders, or assemblers (Group 2), who had intermediate particulate exposure, manifested significantly higher exhaled FeNO compared to machinists (Group 1, with the highest particulate exposure) and all others (Groups 3, the lowest particulate): adjusted Group 2 mean 44.8 ppb (95% confidence interval (CI) 33.8-55.9) vs. Group 1 24.6 ppb (95% 20.5-28.7) and Group 3, 24.3 ppb (95% CI 17.7-30.9). Secondhand smoking and height were not associated with FeNO.

CONCLUSION

In a metalworking industrial cohort, welders/assemblers manifested significantly higher levels of FeNO. This may reflect respiratory tract inflammation associated with airborne exposures specific to this group.

Exhaled nitric oxide in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis

Background

Fractional exhaled nitric oxide (FENO) is a useful and noninvasive biomarker for eosinophilic airway inflammation, particularly in asthma. However, its utility in chronic obstructive pulmonary disease (COPD) remains controversial. In this study, we performed a systematic review and meta-analysis to evaluate FENO levels in COPD.

Methods

A search of PubMed, Embase, Cochrane Library, and clinical trial registry was conducted from inception to January 2018. Studies were included if they reported FENO levels in patients with COPD and healthy controls. We then extracted relevant information and analyzed data. Standard mean difference (SMD) with 95% confidence interval (CI) was applied in this meta-analysis.

Results

A total of 2,073 studies were reviewed for eligibility, with 24 studies pooled for analysis. The FENO levels in patients with COPD were elevated mildly compared with healthy controls (SMD 1.28, 95% CI 0.60-1.96). A similar result was also observed in stable COPD, with an SMD of 1.21 (95% CI 0.47-1.96). On the other hand, we found no association between FENO levels and exacerbated COPD. Additionally, for patients with COPD, ex-smokers had higher levels of FENO than current smokers (SMD 2.05, 95% CI 1.13-2.97).

Conclusion

Our studies demonstrated a mild elevation of FENO in COPD, and the association between exacerbated COPD and FENO levels needs to be further explored. The potential mechanism is still unknown and conflicting.

Endotoxin, dust and exhaled nitrogen oxide among hand pickers of coffee; a cross-sectional study

BACKGROUND

Primary coffee processing takes place in countries where coffee is grown, and may include hand picking of coffee to remove low quality beans. Hand picking is mostly performed by women. No previous studies on dust and respiratory health have been performed in this occupational group, although studies indicate respiratory problems among other coffee production workers.

FINDINGS

Our aim was to assess dust and endotoxin exposure among hand pickers in a coffee factory and compare the levels with limit values. In addition we wanted to examine the fraction of exhaled nitric oxide (FeNO) as a possible inflammatory marker in the airways among the hand pickers and evaluate the association between FeNO and years of hand picking. All hand pickers in a factory were examined during 1 week. The response was 100 %; 69 participated. FeNO was measured using an electrochemistry-based NIOX MINO device. Nine out of 69 workers (13 %) had levels of FeNO above 25 ppb, indicating presence of respiratory inflammation. A significant positive association was found between increasing FeNO and years of hand picking. Nine personal samples of total dust and endotoxin were taken. None of the dust samples exceeded the occupational limit value for total organic dust of 5 mg/m(3). Three samples of endotoxin (33 %) were above the recommended value of 90 EU/m(3).

CONCLUSIONS

Levels of endotoxin were higher than recommended standards among hand pickers, and there was a positive association between the level of exhaled nitrogen oxide and years of work with hand picking coffee.

Functional and biological characteristics of asthma in cleaning workers

OBJECTIVES

Cleaning workers have an increased risk of asthma but the underlying mechanisms are largely unknown. We studied functional and biological characteristics in asthmatic cleaners and compared these to healthy cleaners.

METHODS

Forty-two cleaners with a history of asthma and/or recent respiratory symptoms and 53 symptom-free controls were identified. Fractional exhaled nitric oxide (FeNO) was measured and forced spirometry with reversibility testing was performed. Total IgE, pulmonary surfactant protein D and the 16 kDa Clara Cell secretory protein were measured in blood serum. Interleukins and other cytokines, growth factors, cys-leukotrienes and 8-isoprostane were measured in exhaled breath condensate. Information on occupational and domestic use of cleaning products was obtained in an interview. Associations between asthma status, specific characteristics and the use of cleaning products were evaluated using multivariable linear and logistic regression analyses.

RESULTS

Asthma was associated with an 8% (95% confidence interval (CI) 1-15%) lower postbronchodilator FEV1, a higher prevalence of atopy (42% vs. 10%) and a 2.9 (CI 1.5-5.6) times higher level of total IgE. Asthma status was not associated with the other respiratory biomarkers. Most irritant products and sprays were more often used by asthmatic cleaners. The use of multiuse products, glass cleaners and polishes at work was associated with higher FeNO, particularly in controls.

CONCLUSIONS

Asthma in cleaning workers is characterised by non-reversible lung function decrement and increased total IgE. Oxidative stress, altered lung permeability and eosinophilic inflammation are unlikely to play an important underlying role, although the latter may be affected by certain irritant cleaning exposures.

The effect of a single dose of acetaminophen on airways response in children with asthma

Accumulating evidence suggests that the use of acetaminophen increases the risk of developing asthma and that its widespread use has contributed to the increasing prevalence of asthma.

STUDY DESIGN

To investigate the immediate effect of a single dose of acetaminophen on airways reactivity and inflammation in asthmatic and controls. A double blind placebo-controlled study was conducted on 42 asthmatic children and 21 healthy age-matched controls. Each participant received one oral dose of acetaminophen (15 mg/kg [160 mg/mL]) and one dose of a volume-matched placebo. Physical examination, spirometry results, and fractional exhaled nitric oxide levels were assessed before and 60 minutes following acetaminophen or placebo ingestion.

RESULTS

None of the studied variables showed any significant change after acetaminophen or placebo ingestion in either the asthmatic or the control groups.

CONCLUSIONS

One single dose of acetaminophen neither evokes a bronchoconstriction response nor an increase in airway inflammation in children with asthma.

Update on exhaled nitric oxide in pulmonary disease

The ability to assess the inflammatory status of a patient's airway using a noninvasive method is the ideal situation for clinicians. Owing in part to the relationship between the levels of exhaled nitric oxide to inflammation and the ease of the technique, the measurement of the fraction of exhaled nitric oxide (F(E)NO) has achieved considerable attention, particularly with respect to asthma. A multitude of studies have shown that when measured in exhaled air, this unique molecule has the potential to have both diagnostic and therapeutic roles in the clinical setting for many pulmonary diseases. The incorporation of F(E)NO into asthma management and treatment algorithms may help shed further insight on the current control and future risk of patients. Research is ongoing to determine the biology and the benefits of the use of F(E)NO in respiratory conditions in addition to asthma. This review will briefly outline the pathophysiology of nitric oxide, the measurement of F(E)NO and the potential clinical uses of F(E)NO in asthma and a number of other respiratory diseases. Despite its promise, until further research is conducted, the use of F(E)NO cannot be recommended for routine clinical management of respiratory diseases at present, but should be considered as an adjuvant to help guide therapy in certain patients with asthma and in those with eosinophilic bronchitis.

[Physiology and physiopathology of the distal airways in asthma]

The small airways are those with an internal diameter of less than 2 mm. The contribution of these airways to total airflow resistance is small in healthy individuals but can represent 50-90 % of total airflow resistance in asthmatics. Suspicion of small airways disease has been based on reduction of midexpiratory and instantaneous flows, although wide variability in their values and the absence of a sufficiently validated cut-off point has limited their clinical application. Static pulmonary volumes can provide indirect evidence of the state of the most distal airways, revealing two effects of their alteration: air trapping and dynamic hyperinflation. While determination of airway resistance by plethysmography and of respiratory system resistance measured by flow interruption are highly non-specific, the forced oscillation technique allows obstruction of the small airways to be distinguished from that of medium-caliber airways. The characteristic pattern of peripheral obstruction includes a decrease in frequency-dependent resistance, reduced reactivity and an increase in resonance frequency. Single-or multiple-breath nitrogen washout can also provide specific information on the small airways, although the apparatus required is less frequently available. Analysis through bicompartmental models of exhaled nitric oxide allows alveolar nitric oxide concentrations to be determined, which seems to provide information on inflammatory activity in the small airways.

Utility of two-compartment models of exhaled nitric oxide in patients with asthma

Two-compartment models provide more precise information about the contribution of the different portions of the airways to exhaled nitric oxide (NO). Airway wall concentration of NO (Caw,NO) and maximum flux of NO in the airways (J'aw,NO) reflect the tissue production rate of NO and they can be modified by corticosteroids. The airway wall diffusing capacity of NO (Daw,NO) depends on diverse physical and anatomical determinants of the airways, such as gas exchange surface area. Daw,NO can be modified by structural and physiological changes that are characteristic of airway remodeling, which take place over the long term. The alveolar concentration of NO (Calv,NO) represents the degree of small airway inflammation. The persistence of high Calv,NO in patients treated with inhaled corticosteroids could reflect the incapacity of these drugs to reach distal locations due to the heterogeneity of the acinar ventilation. In this review, we evaluate the parameters provided by the compartmentalized analysis of exhaled NO that could be useful in characterizing asthma patients.

Novel biomarkers in asthma: chemokines and chitinase-like proteins

PURPOSE OF REVIEW

Allergic asthma is a frequent lung disease in Western civilizations and is characterized by airway inflammation and tissue remodeling. Without early diagnosis and specific treatment, asthma results in a loss of lung function, impaired quality of life and the risk to die from uncontrolled asthma attacks. Thus, there is a need for specific biomarkers to detect asthma as soon as possible and to initiate the correct clinical treatment.

RECENT FINDINGS

Recent studies have highlighted the potential role of the chemokine (C-C motif) ligand 17 and the chitinase-like protein YKL-40 as novel biomarkers in asthma. Patient studies suggest that these proteins could be useful to identify asthmatics, to characterize disease severity or both in patients with asthma. Functional studies indicate that these molecules are more than correlated epiphenomena and instead contribute in significant ways to asthma pathogenesis.

SUMMARY

Assessments of chemokine (C-C motif) ligand 17 and YKL-40 may allow physicians to more accurately diagnose and predict the course of asthma and thereby allow therapy to be appropriately tailored for a given patient.

Exhaled nitric oxide in pediatric asthma

Exhaled nitric oxide can now be measured in a clinical setting as a noninvasive, reproducible, facile, point-of-service test to measure airway inflammation, a central component of asthma that had not been assessed previously. An excellent surrogate marker of steroid-responsive eosinophilic airway inflammation, it serves to identify steroid-sensitive asthmatic patients and enables clinical monitoring of the response to steroid therapy and titration of the dose. Standardization of methodology and technological advances, such as the recent availability of handheld analyzers, individualized patient cards to store serial test measurements, and the assignment of coding procedural terminology, make this a necessary adjunct to clinical and functional assessment of airway obstruction and hyperresponsiveness in ambulatory pediatric and adult asthma practices.

Nitric oxide metabolites as biomarkers for follow-up after chronic rhinosinusitis surgery

BACKGROUND

Nitric oxide (NO) has a variety of effects on the pathophysiology of the nasal cavity and seems to play an important role in inflammation. It is increased in the common cold but decreased in acute and chronic rhinosinusitis (CRS). Exhaled NO increases after endoscopic sinus surgery in CRS. In our previous study we showed that NO metabolite (nitrate and nitrite) levels are increased in the sinus cavity of CRS patients. We hypothesized that NO metabolite levels are increased to normal in the nasal lavage of CRS patients after endoscopic sinus surgery and NO metabolites in the nasal lavage can be used as indicators of the disease status after surgery.

METHODS

This study was performed on 52 patients with CRS who did not respond to medical therapy and who underwent surgery. NO metabolite levels were measured in nasal lavages of the patients before surgery and 2 months after surgery.

RESULTS

NO metabolite levels (mean +/- SEM) were 18.11 +/- 3.08 micromol/L and 35.97 +/- 4.64 micromol/L in nasal lavages of patients before and after surgery, respectively. The levels of NO metabolites were increased significantly (p < 0.01) after surgery in nasal lavages and patients reported significant improvement based on the visual analog scoring after the operation.

CONCLUSION

NO metabolite levels were decreased in nasal lavages of CRS patients and were increased to normal levels after surgery along with improvement of the disease. NO metabolite levels may be used as an indicator for the follow-up of patients after endoscopic sinus surgery.