Feasibility and interpretation of FE(NO) measurements in asthma patients in general practice

Effectiveness of exhaled nitric oxide for the prediction of non-invasive left atrial pressure in older people: a cross-sectional cohort study

BACKGROUND

During left-sided heart failure (HF), left atrial and pulmonary venous pressure increase, which may lead to pulmonary congestion. Previous cohort studies, examining participants with symptomatic HF or rheumatic heart disease, suggest a relationship between increased left atrial pressure (LAP) and fractional exhaled nitric oxide (FeNO).

AIM

To examine the strength of association between FeNO and echocardiographic assessment of LAP by the E/e' ratio, to determine if FeNO could be used to identify those with elevated LAP.

DESIGN & SETTING

This cross-sectional cohort study examined a subset of the OxVALVE cohort aged ≥65 years. Data collection was undertaken in primary care practices in central England.

METHOD

Each participant underwent a focused cardiovascular history and clinical examination. Standard transthoracic echocardiographic (TTE) assessment was performed on all participants, with the E/e' ratio calculated to obtain a validated surrogate of LAP. FeNO was measured in 227 participants.

RESULTS

FeNO was higher in males compared with females and no different in participants with asthma, chronic obstructive pulmonary disease (COPD), or those using inhaled steroids. Participants with a high E/e' (>14) were older, with a higher proportion of females than males. There was no relationship between E/e' and FeNO, either when measured as a continuous variable or in the group with high E/e'.

CONCLUSION

FeNO was not found to be an accurate predictor of elevated LAP in a primary care setting.

Underground salt and potash workers exposed to nitrogen oxides and diesel exhaust: assessment of specific effect biomarkers

Purpose

Occupational exposure limits (OEL) for nitrogen oxides (NO, NO₂) and diesel exhaust (EC-DPM) were reassessed by the German authorities in 2016/2017. We performed a clinical cross-sectional study among salt and potash underground workers exposed to these substances at relatively high levels to examine possible indicators of acute effects on workers’ health.

Methods

We measured post- versus pre-shift differences in cardiovascular, inflammatory, immune, and respiratory effect biomarkers and assessed their associations with personal exposures measured during the same shift. We also compared post- versus pre-shift differences in biomarker levels between exposure groups defined based on work site and job type.

Results

None of the above-ground workers exceeded the OEL for NO₂ and only 5% exceeded the OEL for EC-DPM exposure. Among underground workers, 33% of miners and 7% underground maintenance workers exceeded the OEL for NO₂; the OEL for EC-DPM was exceeded by 56% of miners and 17% of maintenance workers.

Some effect biomarkers (thrombocytes, neutrophils, MPO, TNF-α, IgE, FeNO) showed statistically significant differences between pre- versus post-shift measurements; however, there were no consistent associations between pre- and post-shift differences and exposure group or personal exposure measurements during the shift.

Conclusions

We did not find evidence of associations between workplace exposure to NO, NO₂ or EC-DPM and clinically relevant indicators of acute cardiovascular, inflammatory and immune, or respiratory effects among salt and potash underground workers in Germany.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-022-01876-2.

Correlation between fractional exhaled nitric oxide and Asthma Control Test score and spirometry parameters in on-treatment-asthmatics in Ho Chi Minh City

Background

Although fractional exhaled nitric oxide (FeNO) is a reliable and easily applied marker of airway inflammation in asthma, the relationship between FeNO and indicators of asthma control [Asthma Control Test (ACT) score] and/or severity (spirometry parameters) remains unclear. This study aims to determine possible correlations between FeNO and ACT score; and between FeNO and spirometry parameters.

Methods

A cross-sectional study with convenience sampling was conducted among ambulatory patients in the Asthma & COPD clinic at the University Medical Center, Ho Chi Minh City from March 2016 to March 2017. Using measurement of FeNO, the ACT questionnaire and a spirometry test, correlations were determined between FeNO and the ACT score and spirometry parameters.

Results

Four hundred and ten asthmatic patients (mean age 42 years; 65% female) were included and analyzed; their mean time since onset of asthma was 9.5 years. All patients were treated following step 2 to 4 of GINA guidelines. Mean (SD) FeNO was 29.5 (24.4) parts per billion (ppb) and mean (SD) ACT score was 20.5 (40). A significant difference in FeNO values was found among the three groups with different asthma control levels categorized according to the ACT score (P=0.001) but was not found among the three groups with different asthma treatment levels (P=0.425). FeNO was significantly inversely correlated with the ACT score (Spearman’s r =−0.224, P<0.001) and with spirometry parameters indicate airway obstruction such as predicted FEV1, FEV1/FVC, predicted PEF and predicted FEF25–75% with Spearman’s r were −0.187; −0.143; −0.091 and −0.195, respectively (all P<0.05), whereas no correlation between FeNO and FVC—an indicator of airway restriction—was found.

Conclusions

In these asthmatic patients in Vietnam, an inverse correlation was found between FeNO and the ACT score and between FeNO and spirometry indicators of airway obstruction. Therefore, FeNO may be a useful tool in asthma management.

Comparative repeatability of two handheld fractional exhaled nitric oxide monitors

BACKGROUND

The use of portable fractional exhaled nitric oxide (FENO) devices is increasingly common in the diagnosis and management of allergic airways inflammation.

METHODS

We tested two handheld FENO devices, to determine (a) if there was adequate intradevice repeatability to allow the use of single breath testing, and (b) if the devices could be used interchangeably. In a mixed pediatric population, including normal, asthmatic, and children with peanut allergies, 858 paired values were collected from the NIOX-MINO® and/or the NObreath® devices.

RESULTS

The NIOX-MINO® showed excellent repeatability (mean difference of 0.1 with 95% limits of agreement between -7.93 to 7.72 ppb), while the NObreath® showed good repeatability (mean difference of -1.61 with 95% limits of agreement between -14.1 and 10.8 ppb). Intradevice repeatability was good but not adequate and the NIOX-MINO® systematically produced higher results than the NObreath® [mean difference of 7.8 ppb with 95% limits of agreement from -11.55 to 27.52 ppb (-33% to 290%)].

CONCLUSIONS

Our results support the manufacturer's advice that single breath testing is appropriate for the NIOX-MINO®. NObreath® results indicate that the mean of more than one breath should be utilized. The devices cannot be used interchangeably.

Hand-held nitric oxide sensor NIOX MINO® for the monitoring of respiratory disorders

Measurements of exhaled nitric oxide have been proposed as a tool to improve the control of asthma and inflammatory airways disease, including the patient's response to anti-inflammatory treatment and to predict loss of control and to monitor compliance with treatment. Several techniques have been used to assess exhaled nitric oxide gas and the majority of studies have used the chemiluminescence method. More recently, a new hand-held electrochemical sensor NIOX MINO(®) has been developed. Here, we will review the use of the NIOX MINO for the study of respiratory disorders.

Monitoring asthma control in children with allergies by soft computing of lung function and exhaled nitric oxide

BACKGROUND

Asthma control is emphasized by new guidelines but remains poor in many children. Evaluation of control relies on subjective patient recall and may be overestimated by health-care professionals. This study assessed the value of spirometry and fractional exhaled nitric oxide (FeNO) measurements, used alone or in combination, in models developed by a machine learning approach in the objective classification of asthma control according to Global Initiative for Asthma guidelines and tested the model in a second group of children with asthma.

METHODS

Fifty-three children with persistent atopic asthma underwent two to six evaluations of asthma control, including spirometry and FeNO. Soft computing evaluation was performed by means of artificial neural networks and principal component analysis. The model was then tested in a cross-sectional study in an additional 77 children with allergic asthma.

RESULTS

The machine learning method was not able to distinguish different levels of control using either spirometry or FeNO values alone. However, their use in combination modeled by soft computing was able to discriminate levels of asthma control. In particular, the model is able to recognize all children with uncontrolled asthma and correctly identify 99.0% of children with totally controlled asthma. In the cross-sectional study, the model prospectively identified correctly all the uncontrolled children and 79.6% of the controlled children.

CONCLUSIONS

Soft computing analysis of spirometry and FeNO allows objective categorization of asthma control status.

Measurement of fractional exhaled nitric oxide by a new portable device: comparison with the standard technique

BACKGROUND

Fractional exhaled nitric oxide (FeNO) measurement is a reliable, noninvasive marker of airway inflammation. The use of portable FeNO analyzers may enable the assessment of airway inflammation in primary care.

OBJECTIVE

The authors compared FeNO values obtained by a new portable device (NObreath, Bedfont, UK) to those of the standard stationary analyzer (NIOX, Aerocrine, Sweden) in a large cohort of asthmatic patients.

METHODS

One hundred and fifty-four (age range: 14-83 years, forced expiratory volume in one second [FEV(1)] range: 48-134% predicted, asthma control test [ACT] range: 7-25) out of 168 recruited patients completed the study. Each patient performed at least two valid FeNO measurements at a constant flow rate of 50 ml/s on each of the two analyzers.

RESULTS

A significant relationship between the FeNO values obtained by the two devices (r = .95, p < .001) was found. Altman-Bland plot confirmed this agreement. Within-patient repeatability was excellent in both devices. Intraclass correlation coefficients for NIOX and NObreath values were .925 and .967, respectively. By means of receiver operating characteristic curve analysis, the FeNO cutoff points that better identified patients with ACT ≥ 20 were 15 ppb (0.84 sensitivity and 0.42 specificity) by NIOX and 25 ppb (0.53 sensitivity and 0.69 specificity) by NObreath. Easiness to use of both devices, assessed by visual analogue scale was not different.

CONCLUSION

FeNO measurements obtained by the new portable FeNO analyzer are reliable because they are directly comparable with those obtained by the stationary standard device. The use of portable instruments may facilitate the FeNO measurement in primary care.

Comparison of eNO and histamine hyperresponsiveness in diagnosing asthma in new referrals

The mainstay of the diagnosis of asthma is the presence of reversible airway obstruction. Exhaled NO levels are increased in asthma, in close relationship with the amount of airway inflammation, and may be used for monitoring the disease and adjusting therapy. In this study we investigated the role of eNO as a diagnostic for asthma, compared with the FEV1-reversibility and the PC20 (20% decrease of the FEV1 in the bronchial histamine provocation test), in two independent centers, on an unselected population. ENO measurements were performed with chemoluminesence technique in one center and with an electrochemical device in the other. Only after correction for so-called nuisance factors (allergy, use of inhaled steroids, recent infection, smoking, sex and the use of nitrate food) the eNO appeared as a diagnostic with equal power as the FEV1-reversibility and the PC20. Therefore, screening for asthma in our study population, with the eNO measurement, is a simple, fast and safe strategy.

Childhood Asthma Control Test and airway inflammation evaluation in asthmatic children

BACKGROUND

The Childhood Asthma Control Test (C-ACT) has been proposed as a tool in assessing the level of disease control in asthmatic children. To evaluate the position of C-ACT in the clinical management of asthmatic children, in relationship to the level of airway inflammation as assessed by fractional exhaled nitric oxide (FeNO) and with lung function.

METHODS

A total of 200 asthmatic children were included in the study: 47 children with newly diagnosed asthma ('New') and without any regular controller therapy; and 153 children with previously diagnosed asthma, treated according to GINA guidelines, and evaluated during a scheduled follow-up visit ('Follow-up'). Childhood Asthma Control Test, FeNO and lung function [forced expiratory volume 1 (FEV1) and forced vital capacity (FVC)] were evaluated.

RESULTS

In New vs Follow-up participants, C-ACT score (P < 0.001), FVC (P < 0.005) and FEV1 (P < 0.05) were significantly lower, and FeNO (P = 0.011) were significantly higher. In New, but not in Follow-up participants, significant correlations were observed between C-ACT score and FeNO (r = -0.51; P < 0.001), FEV1 (r = 0.34; P = 0.022) and FEV1/FVC (r = 0.32; P = 0.03). This lack of correlation in Follow-up visits seemed attributable to dissociation between inadequately controlled asthma by C-ACT ratings with normalization of other measures such as FeNO levels.

CONCLUSIONS

This study confirms and expands the concept that C-ACT is complementary to, but not a substitute for, other markers of disease control in asthmatic children, especially in the context of follow-up visits.

Microgravity decreases and hypergravity increases exhaled nitric oxide

Inhalation of toxic dust during planetary space missions may cause airway inflammation, which can be monitored with exhaled nitric oxide (NO). Gravity will differ from earth, and we hypothesized that gravity changes would influence exhaled NO by altering lung diffusing capacity and alveolar uptake of NO. Five subjects were studied during microgravity aboard the International Space Station, and 10 subjects were studied during hypergravity in a human centrifuge. Exhaled NO concentrations were measured during flows of 50 (all gravity conditions), 100, 200, and 500 ml/s (hypergravity). During microgravity, exhaled NO fell from a ground control value of 12.3 ± 4.7 parts/billion (mean ± SD) to 6.6 ± 4.4 parts/billion ( P = 0.016). In the centrifuge experiments and at the same flow, exhaled NO values were 16.0 ± 4.3, 19.5 ± 5.1, and 18.6 ± 4.7 parts/billion at one, two, and three times normal gravity, where exhaled NO in hypergravity was significantly elevated compared with normal gravity ( P ≤ 0.011 for all flows). Estimated alveolar NO was 2.3 ± 1.1 parts/billion in normal gravity and increased significantly to 3.9 ± 1.4 and 3.8 ± 0.8 parts/billion at two and three times normal gravity ( P < 0.002). The findings of decreased exhaled NO in microgravity and increased exhaled and estimated alveolar NO values in hypergravity suggest that gravity-induced changes in alveolar-to-lung capillary gas transfer modify exhaled NO.

[Feasibility of FeNO measurement in asthmatic children in the primary care setting. CANON Study]

AIM

Asses the feasibility of exhaled nitric oxide (FeNO) measurement in asthmatic children using a hand-held device in the primary care setting.

METHODS

Multicentre study performed in the paediatric clinics in seven Spanish primary health care centres. Each centre consecutively included 6-14 year-old children with doctor-diagnosed asthma. Children were asked to obtain two valid measurements of FeNO with the hand-held device NIOX MINO (Aerocrine AB, Solna, Sweden). Feasibility analysis included: (a) percentage of children able to perform the manoeuvre, (b) time required to obtain a successful determination, (c) number of attempts needed, and (d) acceptability of the technical procedure by clinical personnel involved in their guidance.

RESULTS

The Study enrolled 151 children. A total of 149 (98.7%) were able to perform the FeNO manoeuvre. The majority (55%) of children had previous experience of using the hand-held device. The Overall median (and Interquartile Range, IQR) of attempts needed to reach a first valid measurement was 2 (1-3) and median (IQR) of time taken was 4 min (3-5). Nurses considered the overall procedure was very easy or easy in 87.8% (teaching) and 86.5% (performing) of children. Children with previous experience performed the manoeuvre in less attempts, less time and more easily than children without experience.

CONCLUSIONS

Measurement of FeNO using NIOX MINO device is technically feasible and acceptable for children and staff in the clinical context of asthma management in primary health care. Previous experience had a positive, learning effect, in teaching and performing the FeNO manoeuvre.

Why is effective treatment of asthma so difficult? An integrated systems biology hypothesis of asthma

A hypothesis is presented that asthma is not only an airway disease, but that the disease involves the entire lung, and that the chronicity of asthma and asthma exacerbations can perhaps be explained if one considers asthma as a systemic disease. Increased lung-not only airway-vascularity may be the result of the action of angiogenesis factors, such as vascular endothelial growth factor (VEGF) and sphingosine-1-phosphate (S1P). A bone-marrow lung axis can be postulated as one element of the systemic nature of the asthma syndrome, in which the inflamed lung emits chemotactic signals, which the bone marrow responds to by releasing cells that contribute to lung angiogenesis. A molecular model of the pathobiology of asthma can be built by connecting hypoxia-inducible transcription factor-1 alpha, VEGF S1P, and bone-marrow precursor cell mobilization and acknowledging that angiogenesis is part of the inflammatory response.