Exhaled nitric oxide - circadian variations in healthy subjects

Phenotyping the Responses to Systemic Corticosteroids in the Management of Asthma Attacks (PRISMA): protocol for an observational and translational pilot study

INTRODUCTION

Asthma and its associated exacerbation are heterogeneous. Although severe asthma attacks are systematically prescribed corticosteroids and often antibiotics, little is known about the variability of response to these therapies. Blood eosinophils and fractional exhaled nitric oxide (FeNO) are type 2 inflammation biomarkers that have established mechanistic, prognostic and theragnostic values in chronic asthma, but their utility in acute asthma is unclear. We speculate that the clinical and biological response to those treatments varies according to inflammometry and microbiological test results.

METHODS AND ANALYSIS

An observational longitudinal pilot study with multimodal clinical and translational assessments will be performed on 50 physician-diagnosed ≥12-year-old asthmatics presenting with an asthma attack and 12 healthy controls, including blood eosinophil count (venous and point-of-care (POC) capillary blood), FeNO and testing for airway infection (sputum cultures and POC nasopharyngeal swabs). People with asthma will be assessed on day 0 and after a 7-day corticosteroid course, with home monitoring performed in between. The primary analysis will be the change in the forced expiratory volume in 1 s according to type 2 inflammatory status (blood eosinophils ≥0.15×109/L and/or FeNO ≥25 ppb) after treatment. Key secondary analyses will compare changes in symptom scores and the proportion of patients achieving a minimal clinically important difference. Exploratory analyses will assess the relationship between clinical, lung function, inflammatory and microbiome parameters; satisfaction plus reliability indices of POC tests; and sex-gender variability in treatment response. Ultimately, this pilot study will serve to plan a larger trial comparing the clinical and biological response to systemic corticosteroids according to inflammatory biomarkers, offering valuable guidance for more personalised therapeutic strategies in asthma attacks.

ETHICS AND DISSEMINATION

The protocol has been approved by the Research Ethics Committee of the CIUSSS de l'Estrie-CHUS, Sherbrooke, Quebec, Canada (#2023-4687). Results will be communicated in an international meeting and submitted to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT05870215).

Nitric oxide: To be or not to be an endocrine hormone?

Nitric oxide (NO), a highly reactive gasotransmitter, is critical for a number of cellular processes and has multiple biological functions. Due to its limited lifetime and diffusion distance, NO has been mainly believed to act in autocrine/paracrine fashion. The increasingly recognized effects of pharmacologically delivered and endogenous NO at a distant site have changed the conventional wisdom and introduced NO as an endocrine signalling molecule. The notion is greatly supported by the detection of a number of NO adducts and their circulatory cycles, which in turn contribute to the transport and delivery of NO bioactivity, remote from the sites of its synthesis. The existence of endocrine sites of synthesis, negative feedback regulation of biosynthesis, integrated storage and transport systems, having an exclusive receptor, that is, soluble guanylyl cyclase (sGC), and organized circadian rhythmicity make NO something beyond a simple autocrine/paracrine signalling molecule that could qualify for being an endocrine signalling molecule. Here, we discuss hormonal features of NO from the classical endocrine point of view and review available knowledge supporting NO as a true endocrine hormone. This new insight can provide a new framework within which to reinterpret NO biology and its clinical applications.

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.

Occupational exposure to trichloramine and trihalomethanes: adverse health effects among personnel in habilitation and rehabilitation swimming pools

Personnel in swimming pool facilities typically experience ocular, nasal, and respiratory symptoms due to water chlorination and consequent exposure to disinfection by-products in the air. The aim of the study was to investigate exposure to trichloramine and trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) from the perspective of adverse health effects on the personnel at Swedish habilitation and rehabilitation swimming pools. The study included 10 habilitation and rehabilitation swimming pool facilities in nine Swedish cities. The study population comprised 24 exposed swimming pool workers and 50 unexposed office workers. Personal and stationary measurements of trichloramine and trihalomethanes in air were performed at all the facilities. Questionnaires were distributed to exposed workers and referents. Spirometry, fraction of exhaled nitric oxide (FE_NO), and peak expiratory flow (PEF) were measured. Personal and stationary measurements yielded trichloramine levels of 1-76 µg/m³ (average: 19 µg/m³) and 1-140 µg/m³ (average: 23 µg/m³), respectively. A slightly higher, but not significant, prevalence of reported eye- and throat-related symptoms occurred among the exposed workers than among the referents. A significantly increased risk of at least one ocular symptom was attributed to trichloramine exposure above the median (20 µg/m³). Lung function (FVC and FEV1) was in the normal range according to the Swedish reference materials, and no significant change in lung function before and after shift could be established between the groups. Average FE_NO values were in the normal range in both groups, but the difference in the values between the exposed workers and referents showed a significant increase after shift. Hourly registered PEF values during the day of the investigation did not show any unusual individual variability. In conclusion, the increased risk of developing at least one ocular symptom at personal trichloramine concentrations over 20 µg/m³ combined with an increase in the difference in FE_NO during the work shift of the exposed workers should not be neglected as an increased risk of respiratory inflammation in the habilitation and rehabilitation swimming pool environment.

Comparison of two exhaled biomarkers in children with and without sleep disordered breathing

OBJECTIVE

Airway oxidative stress and inflammation are likely to be involved in sleep disordered breathing (SDB) in children. We aimed to measure concentrations of 8-isoprostane (8-IsoP) in the exhaled breath condensate (EBC) and exhaled nitric oxide (FE_NO) in patients with SBD and healthy children, in order to assess the relationship between these two biomarkers, disease severity, and overnight changes.

METHODS

Patients with SDB (n = 46) and healthy controls (n = 20) aged 4.5-15.1 years (M/F: 36/30) underwent exhaled measurements. Patients with SDB underwent standard polysomnography to define primary snoring (PS: AHI < 1) and obstructive sleep apnea (OSA). Upon awakening the following morning, FE_NO was measured and EBC was collected for the measurement of EBC 8-IsoP.

RESULTS

OSA patients yielded higher awakening levels of 8-IsoP in EBC than PS patients and control subjects. The 8-IsoP levels, though not FE_NO, correlated with AHI (r = 0.40, p = 0.003) and SaO2 (r = -0.50, p = 0.001). Cut-off levels of 8-IsoP predicted OSA with a high AUC value (0.84, p = 0.000). Sensitivity and specificity for 8-IsoP levels above the percentile 50 (33.3 pg/mL) were 76.5% and 78.1%, respectively. 8-IsoP levels did not change from the evening to morning session, whereas morning FE_NO levels rose significantly only in patients with mild OSA (p = 0.03).

CONCLUSION

Levels of 8-IsoP, though not FE_NO, distinguish children with OSA from those with PS or healthy, correlate with disease severity and closely predict OSA in the whole sample.

Clinical Effects, Exhaled Breath Condensate pH and Exhaled Nitric Oxide in Humans After Ethyl Acrylate Exposure

Ethyl acrylate is an irritant known to affect the upper airways and eyes. An increase of the eye blink frequency in humans was observed during exposure to 5 ppm. Studies on the lower airways are scant and our study objective was the evaluation of pH in exhaled breath condensate (EBC-pH) and nitric oxide in exhaled breath (FeNO) as markers of inflammation. Sixteen healthy volunteers were exposed for 4 h to ethyl acrylate at a concentration of 5 ppm and to sham (0.05 ppm) in an exposure laboratory. Clinical irritation symptoms, EBC-pH (at a pCO2 of 5.33 kPa) and FeNO were assessed before and after exposure. Differences after ethyl acrylate exposure were adjusted for those after sham exposure. 5 ppm ethyl acrylate induced clinical signs of local irritation in the nose and eyes, but not in lower airways. Exposure produced a subtle, but statistically significant, decrease in breathing frequency (1 breath/min; p = 0.017) and a lower EBC-pH (by 0.045 units; p = 0.037). Concerning FeNO, we did not observe significant changes compared to sham exposure. We conclude that local effects induced by 5 ppm ethyl acrylate consist of sensory irritation of eyes and nose. In addition, acute ethyl acrylate exposure to 5 ppm resulted in a net decrease of EBC-pH. Whether that can be interpreted in terms of additional lower airway irritation or already inflammatory alterations set in needs further investigations.

Tai-Chi-Chuan Exercise Improves Pulmonary Function and Decreases Exhaled Nitric Oxide Level in Both Asthmatic and Nonasthmatic Children and Improves Quality of Life in Children with Asthma

Tai-Chi-Chuan (TCC) is an exercise of low-to-moderate intensity which is suitable for asthmatic patients. The aim of our study is to investigate improvements of the lung function, airway inflammation, and quality of life of asthmatic children after TCC. Participants included sixty-one elementary school students and they were divided into asthmatic (n = 29) and nonasthmatic (n = 32) groups by the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Among them, 20 asthmatic and 18 nonasthmatic children volunteered to participate in a 60-minute TCC exercise weekly for 12 weeks. Baseline and postintervention assessments included forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak expiratory flow rate (PEFR), fractional exhaled nitric oxide (FeNO) level, and Standardised Pediatric Asthma Quality of Life Questionnaire (PAQLQ(S)). After intervention, the level of FeNO decreased significantly; PEFR and the FEV1/FVC also improved significantly in both asthmatic group and nonasthmatic group after TCC. The asthmatic children also had improved quality of life after TCC. The results indicated that TCC could improve the pulmonary function and decrease airway inflammation in both children with mild asthma and those without asthma. It also improves quality of life in mild asthmatic children. Nevertheless, further studies are required to determine the effect of TCC on children with moderate-to-severe asthma.

Diagnostic significance of nitric oxide concentrations in exhaled air from the airways in allergic rhinitis patients

INTRODUCTION

The effect of nitric oxide (NO) on the human body is very important due its physiological regulation of the following functions of airways: modulation of ciliary movement and maintenance of sterility in sinuses.

AIM

To evaluate the diagnostic significance of NO concentrations in exhaled air from the upper and lower airways in patients diagnosed with allergic rhinitis (AR).

MATERIAL AND METHODS

The subjects included in the study were a group of 30 people diagnosed with sensitivity to environmental allergens and a control group consisting of 30 healthy subjects. The measurement of NO in the air exhaled from the lower and upper airways was performed using an on-line method by means of Restricted Exhaled Breath (REB), as well as using the measurement procedure (chemiluminescence) set out in the guidelines prepared in 2005 by the American Thoracic Society and the European Respiratory Society.

RESULTS

In the late phase of the allergic reaction, higher values of the level of exhaled NO concentration from the lower airways were observed in the groups of subjects up to the threshold values of 25.17 ppb in the group of subjects with year-round allergic rhinitis and 21.78 ppb in the group with diagnosed seasonal allergic rhinitis. The difference in the concentration of NO exhaled from the lungs between the test group and the control group in the 4(th) h of the test was statistically significant (p = 0.045).

CONCLUSIONS

Exhaled NO should be considered as a marker of airway inflammation. It plays an important role in the differential diagnosis of allergy.

Study of Exhaled Nitric Oxide in Subjects with Suspected Obstructive Sleep Apnea: A Pilot Study in Vietnam

Background and Objective. The concentration of exhaled nitric oxide (eNO), reflecting the activity of inducible NO synthase in airway epithelium, has been found to increase in patients with obstructive sleep apnea (OSA). This study aimed to measure eNO concentration in patients with suspected OSA and to correlate different eNO parameters with clinical and sleep apnea characteristics. Methods. In this cross-sectional study, all patients underwent in-lab overnight polysomnography (PSG) and eNO measurement using a method of multiple flow rates before and after PSG (pre- and post-PSG). Results. According to the result of PSG, 82 persons were divided into two groups: control subjects (n = 30; 54 ± 14 years) and patients with OSA defined as apnea-hypopnea index (AHI) ≥ 5/hour (n = 52; 53 ± 12 years). Body mass index (BMI) and neck and abdomen circumferences of OSA patients were significantly higher than those from control subjects. In OSA group, post-PSG alveolar NO concentration (CANO) (5.3 ± 1.9 ppb) was significantly higher than pre-PSG CANO (4.0 ± 1.7 ppb; P < 0.001). Significant correlations have been found between CANO and AHI (P < 0.001) and between CANO and nadir SpO₂ (P < 0.05). The daytime CANO value of more than 4.1 ppb can be used to screen symptomatic subjects for the presence of OSA with a high specificity of 93.3%. Conclusion. Our findings indicate CANO as a surrogate marker for OSA in persons with suggestive symptoms.

Variability of FeNO in healthy subjects at 2240 meters above sea level

Fraction of exhaled nitric oxide (FeNO) is a marker of eosinophilic airway inflammation. Altitude above sea level can affect measurements of this index, but there is only limited information regarding the diurnal variation (ante meridiem vs. post meridiem) and reproducibility of FeNO on consecutive days at moderate altitudes. To evaluate the diurnal variability of FeNO and assess its reproducibility over five consecutive days in healthy individuals living at 2240 m, and to compare the FeNO readings taken with two different analyzers. Healthy non-smoking adults were measured using NIOX MINO(®) or NOA 280i(®) devices. One group (n = 10) had readings taken morning and afternoon for five consecutive days with the NIOX MINO(®) equipment; while the second group (n = 17) was measured on only one morning but by both the electrochemical analyzer (NIOX MINO(®)) and the chemiluminescence method (NOA 280i(®)). The study group consisted of 27 subjects aged 28.7 ± 6 years. Morning and afternoon FeNO measurements were 15.2 ± 7.5 ppb and 15.2 ± 7.9 ppb (p = 0.9), respectively. The coefficient of variation (CV) of these measurements (a.m. vs. p.m.) was 10.7 %, and the coefficient of repeatability (CR), 4.2 ppb. The concordance correlation coefficient (CCC) between the two measures (morning vs. afternoon) was 0.91. The CV and CR of the five morning readings were 15.4 % and 4.3 ppb, respectively; while those of the five afternoon measures were 13.6 % and 3.5 ppb, respectively. The CCC between the NIOX MINO(®) equipment and the NOA-280i(®) device was 0.8, with 95 % limits of agreement of -8.35 to 0.29 ppb. In adults living at 2240 m above sea level, FeNO measurements show minimal diurnal variation, and readings are reproducible (<15 %) over a period of at least five consecutive days; however, the FeNO measurements obtained with the NIOX MINO(®) and NOA 280i(®) devices are not interchangeable due to the wide limits of agreement recorded.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

Across-shift changes of exhaled nitric oxide and spirometric indices among cotton textile workers

OBJECTIVES

For the purpose of evaluation of exhaled NO as an index of airway inflammation, we assessed changes in fractional exhaled NO (FeNO) across a work shift and its relationship with respiratory complaints.

MATERIAL AND METHODS

Chronic and work-aggravated respiratory complaints were assessed using a questionnaire in 89 male textile workers. FeNO and spirometry were performed before and after a work shift and all the changes were registered.

RESULTS

A significant increase in FeNO after a work shift was observed. Post-shift FeNO was significantly higher among the subjects with chronic respiratory complaints. There was an obvious decrease in FVC, and FEV1 after a work shift; however, we couldn't find a significant relationship between changes in respiratory parameters and concentration of inhalable dusts.

CONCLUSIONS

FeNO increase after a work shift along with pulmonary function decrement and higher post-shift FeNO among subjects with respiratory complaints makes across-shift FeNO a non-invasive test for assessment of airway hyper-responsiveness in textile workers.

Factors influencing the levels of exhaled carbon monoxide in asthmatic children

OBJECTIVE

Bronchial asthma is characterised by chronic airway inflammation commonly associated with increased oxidative stress. Exhaled carbon monoxide (eCO) levels could act as markers of both oxidative stress and allergic inflammation. We aimed to study eCO levels in asthmatics and detect the possible factors influencing them.

METHODS

We studied 241 asthmatic children and 75 healthy children. The differences in eCO levels among various asthmatic phenotypes and the correlations between eCO and other measured parameters (spirometric indices, Asthma Control Test score, exhaled nitric oxide, total IgE, blood eosinophils and marker of oxidative damage of proteins) were analysed.

RESULTS

Levels of eCO widely differed according to the selected characteristics of asthma. Asthmatics showed higher eCO concentrations than controls (1.44 ± 0.12 ppm vs. 0.91 ± 0.11 ppm, p < 0.001). Acute exacerbation of asthma was accompanied by a significant increase in eCO compared to the clinically controlled stage (2.17 ± 0.36 ppm vs. 1.33 ± 0.13 ppm, p < 0.001). Atopic, non-atopic asthma and asthma associated with allergic rhinitis (AR) showed elevated levels of eCO. The levels of eCO negatively correlated with the marker of protein oxidation in asthmatics, especially in atopic form and during acute exacerbation.

CONCLUSIONS

In a population of asthmatic children, eCO levels could be considered as a marker of both allergic inflammation and oxidative stress in the airways. Concomitant AR and asthma control were the most important factors affecting the levels of eCO in asthmatic children. However, our results do not support the use of routine eCO in the clinical practice.

Reference values and factors associated with exhaled nitric oxide: U.S. youth and adults

BACKGROUND

Normative values for fractional exhaled nitric oxide (FeNO) and the associated co-factors are important in understanding the role of FeNO as a biomarker in airway disease. The objective of this study is to establish reference FeNO values for youth and adult asymptomatic, lifetime nonsmokers in the United States, and to describe the factors affecting these levels.

METHODS

Cross-sectional analyses of the National Health and Nutrition Examination Survey from 2007 to 2010. The analytic sample consisted of 4718 youth and adults, ages 6-79 years, who were lifelong nonsmokers, and free of asthma, and other respiratory conditions and symptoms. Loge FeNO values were used as dependent variables to test associations of demographic and health related-covariates. Multivariable regression models were used to assess the independent effect and covariate-adjusted contribution of the factors.

RESULTS

The geometric mean FeNO level was 8.3, 12.1, and 16.2 ppb for males 6-11, 12-19, and 20-79 years, and 8.4, 10.9, and 12.6 ppb for females in the corresponding age groups. Overall, FeNO levels increased with increasing age (p < 0.001), and height (p < 0.001). In all age groups, FeNO levels were positively associated with eosinophil counts, and with testing in the morning. Among youths 6-11 and 12-19 years, non-Hispanics whites had lower FeNO values than non-Hispanic blacks and Hispanic youths. No race-ethnic difference in FeNO levels was evident for adults 20-79 years. Among adolescents and adults, FeNO levels were higher for males than for females, controlling for all other factors.

CONCLUSIONS

These reference values and associated attributes in youths and adults are useful in evaluating the role of FeNO in airway diseases.