Effect of caffeine ingestion on exhaled nitric oxide measurements in patients with asthma

Urinary caffeine and caffeine metabolites, asthma, and lung function in a nationwide study of U.S. adults

OBJECTIVE

Coffee intake has been inversely associated with asthma in adults. We examined the relation between urinary levels of caffeine or caffeine metabolites and asthma, lung function, and fractional exhaled nitric oxide (FeNO) in adults.

METHODS

Cross-sectional study of 2,832 adults aged 18-79 years in the US National Health and Nutrition Examination Survey (NHANES). Multivariable logistic or linear regression was used for the analysis of urinary levels of caffeine or each of its three major metabolites (paraxanthine, theobromine, and theophylline) and current asthma, lung function, and FeNO.

RESULTS

Subjects with urinary paraxanthine levels in the fourth quartile (Q4) had 53% lower odds of current asthma than those whose urinary paraxanthine levels were in the first quartile (Q1; 95% confidence = 0.22 to 1.00). Among never and former smokers, subjects with urinary theophylline levels above Q1 had 49% lower odds of current asthma than those whose urinary theophylline level was in Q1 (95% CI = 0.31 to 0.85). Among subjects without current asthma, each log₁₀-unit increment in paraxanthine level was associated with a 0.83% increment in percent predicted (%pred) FEV₁ and a 1.27% increment in %pred FVC, while each log₁₀-unit in theophylline was associated with a 1.24% increment in %pred FVC. Neither urinary caffeine nor any urinary caffeine metabolite was associated with bronchodilator response or FeNO.

CONCLUSIONS

Our findings suggest that two caffeine metabolites (theophylline and paraxanthine) may contribute to the previously reported inverse association between coffee intake and asthma in adults.

Exhaled NO: Determinants and Clinical Application in Children With Allergic Airway Disease

Nitric oxide (NO) is endogenously released in the airways, and the fractional concentration of NO in exhaled breath (FeNO) is now recognized as a surrogate marker of eosinophilic airway inflammation that can be measured using a noninvasive technique suitable for young children. Although FeNO levels are affected by several factors, the most important clinical determinants of increased FeNO levels are atopy, asthma, and allergic rhinitis. In addition, air pollution is an environmental determinant of FeNO that may contribute to the high prevalence of allergic disease. In this review, we discuss the mechanism for airway NO production, methods for measuring FeNO, and determinants of FeNO in children, including host and environmental factors such as air pollution. We also discuss the clinical utility of FeNO in children with asthma and allergic rhinitis and further useful directions using FeNO measurement.

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.

The effect of caffeinated coffee on airway response to methacholine and exhaled nitric oxide

BACKGROUND

The bronchoprotective effect of caffeine on histamine challenge testing (HCT) has been studied with equivocal results. Current guidelines for bronchoprovocation testing recommend exclusion of caffeine the day of testing. The effects of caffeine on methacholine challenge testing (MCT), now more commonly performed than histamine challenge, are unknown.

METHODS

Sixteen well-controlled asthmatics with a forced expiratory volume in 1 s (FEV(1)) > 65% predicted and methacholine provocation concentration causing a 20% fall in FEV(1) (PC(20)) ≤ 16 mg/ml participated in a randomized single-blind crossover study. The two treatments included 16 ounces of caffeinated and decaffeinated coffee given on two separate days. The fraction of exhaled nitric oxide (eNO) and FEV(1) were measured before and 1 h after each treatment. One hour post treatment blood was drawn for serum caffeine level and the MCT was done.

RESULTS

Fourteen subjects completed the study; there were no adverse events. No significant bronchodilation was seen between the mean FEV(1) values before and after the caffeinated treatment (3.31 ± 0.75 L and 3.36 ± 0.74 L, respectively). No significant bronchoprotection was seen between the caffeinated and decaffeinated treatment's geometric mean PC(20) values (1.35 mg/ml and 1.36 mg/ml, respectively). Mean eNO values before and after caffeinated treatment were not significantly different (31.2 ± 19.6 ppb and 31.5 ± 20.4 ppb).

CONCLUSION

The amount of caffeine in a normal dietary serving of a 16 oz cup of coffee is not enough to cause significant bronchoprotection, bronchodilation, or decrease eNO values. Registered at http://clinicaltrials.gov: NCT01057875.

Changes to exhaled nitric oxide in asthmatic children after drinking a caffeine-containing cola drink

INTRODUCTION

Exhaled nitric oxide (FE(NO)) may be a biomarker for airway eosinophilia and of use in the management of childhood asthma. Caffeine ingestion has been associated with changes in FE(NO) concentration in adults. The present study tested the hypothesis that ingestion of a caffeine-containing cola drink will increase FE(NO) in asthmatic children.

METHODS

Exhaled NO was measured in children with asthma before, 30 and 60 min after taking a cola drink containing 0.7 mg/kg caffeine. Intrasubject changes in FE(NO) and flow independent NO parameters were determined including bronchial wall NO flux (J'awNO).

RESULTS

Eleven children with asthma were recruited, 10 were prescribed inhaled corticosteroids and 9 were skin prick positive. The median [interquartile range, IQR] FE(NO) at baseline was 47 parts per billion [9,64] and this rose to 56 ppb [11, 66] after 30 min and returned to 46 ppb [9, 62] after 60 min, Friedman's test P = 0.003. J'awNO rose from a median [IQR] 2,843 nl/sec [356, 4,247] at baseline to 3,304 nl/sec [479, 4,387] after 30 min and returned to 2,937 nl/sec [356, 4,153] after 60 min, Freidman's test P = 0.003. There was no significant change in other flow independent NO parameters.

CONCLUSIONS

Ingestion of a caffeine-containing cola drink was associated with a modest and transient rise in FE(NO) which is mostly explained by increased NO production in the proximal airways. Ingestion of a caffeine-containing cola drink may result in clinically relevant acute changes in FE(NO) for children with asthma.

Caffeine for asthma

BACKGROUND

Caffeine has a variety of pharmacological effects; it is a weak bronchodilator and it also reduces respiratory muscle fatigue. It is chemically related to the drug theophylline which is used to treat asthma. It has been suggested that caffeine may reduce asthma symptoms and interest has been expressed in its potential role as an asthma treatment. A number of studies have explored the effects of caffeine in asthma, this is the first review to systematically examine and summarise the evidence.

OBJECTIVES

To assess the effects of caffeine on lung function and identify whether there is a need to control for caffeine consumption prior to either lung function or exhaled nitric oxide testing.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and the reference lists of articles (August 2009). We also contacted study authors.

SELECTION CRITERIA

Randomised clinical trials of oral caffeine compared to placebo or coffee compared to decaffeinated coffee in adults with asthma.

DATA COLLECTION AND ANALYSIS

Trial selection, quality assessment and data extraction were done independently by two reviewers.

MAIN RESULTS

Seven trials involving a total of 75 people with mild to moderate asthma were included. The studies were all of cross-over design .Six trials involving 55 people showed that in comparison with placebo, caffeine, even at a 'low dose' (< 5mg/kg body weight), appears to improve lung function for up to two hours after consumption. Forced expiratory volume in one minute showed a small improvement up to two hours after caffeine ingestion (SMD 0.72; 95% CI 0.25 to 1.20), which translates into a 5% mean difference in FEV1. However in two studies the mean differences in FEV1 were 12% and 18% after caffeine. Mid-expiratory flow rates also showed a small improvement with caffeine and this was sustained up to four hours.One trial involving 20 people examined the effect of drinking coffee versus a decaffeinated variety on the exhaled nitric oxide levels in patients with asthma and concluded that there was no significant effect on this outcome.

AUTHORS' CONCLUSIONS

Caffeine appears to improve airways function modestly, for up to four hours, in people with asthma . People may need to avoid caffeine for at least four hours prior to lung function testing, as caffeine ingestion could cause misinterpretation of the results. Drinking caffeinated coffee before taking exhaled nitric oxide measurements does not appear to affect the results of the test, but more studies are needed to confirm this.

Exhaled nitric oxide - circadian variations in healthy subjects

OBJECTIVE

Exhaled nitric oxide (eNO) has been suggested as a marker of airway inflammatory diseases. The level of eNO is influenced by many various factor including age, sex, menstrual cycle, exercise, food, drugs, etc. The aim of our study was to investigate a potential influence of circadian variation on eNO level in healthy subjects.

METHODS

Measurements were performed in 44 women and 10 men, non-smokers, without respiratory tract infection in last 2 weeks. The eNO was detected at 4-hour intervals from 6 a.m. to 10 p.m. using an NIOX analyzer. We followed the ATS/ERS guidelines for eNO measurement and analysis.

RESULTS

Peak of eNO levels were observed at 10 a.m. (11.1 +/- 7.2 ppb), the lowest value was detected at 10 p.m. (10.0 +/- 5.8 ppb). The difference was statistically significant (paired t-test, P<0.001).

CONCLUSIONS

The daily variations in eNO, with the peak in the morning hours, could be of importance in clinical practice regarding the choice of optimal time for monitoring eNO in patients with respiratory disease.

Exhaled nitric oxide in the diagnosis and management of asthma: clinical implications

Exhaled nitric oxide (eNO) used as an aid to the diagnosis and management of lung disease is receiving attention from pulmonary researchers and clinicians alike because it offers a noninvasive means to directly monitor airway inflammation. Research evidence suggests that eNO levels significantly increase in individuals with asthma before diagnosis, decrease with inhaled corticosteroid administration, and correlate with the number of eosinophils in induced sputum. These observations have been used to support an association between eNO levels and airway inflammation. This review presents an update on current opportunities regarding use of eNO in patient care, and more specifically on its potential usage for asthma diagnosis and monitoring. The review will also discuss factors that may complicate use of eNO as a diagnostic tool, including changes in disease severity, symptom response, and technical measurement issues. Regardless of the rapid, convenient, and noninvasive nature of this test, additional well-designed, long-term longitudinal studies are necessary to fully evaluate the clinical utility of eNO in asthma management.

The use of fraction of exhaled nitric oxide in pulmonary practice

The measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a convenient, noninvasive, point-of-service office test for airway inflammation. The first half of this practice management review presents the methodological, interpretative, and clinical applications of FeNO. The second half discusses practical management issues, including current and future technology, equipment specifications, US Food and Drug Administration regulations, cost, current procedural terminology coding, and reimbursement. The measurement of FeNO is helpful in the diagnosis of asthma. It is predictive of a response to inhaled corticosteroids (ICSs). Monitoring FeNO is useful in maintaining asthma control by allowing the assessment of adherence to medication and dose titration of ICSs. An elevated level of FeNO is predictive of asthma relapse following corticosteroid withdrawal especially in children. The advances in technology, ease of use, and clinical utility will lead to greater availability, acceptance, and routine application in the care of asthma.

Exhaled nitric oxide in childhood asthma: a review

As an 'inflammometer', the fraction of nitric oxide in exhaled air (Fe(NO)) is increasingly used in the management of paediatric asthma. Fe(NO) provides us with valuable, additional information regarding the nature of underlying airway inflammation, and complements lung function testing and measurement of airway hyper-reactivity. This review focuses on clinical applications of Fe(NO) in paediatric asthma. First, Fe(NO) provides us with a practical tool to aid in the diagnosis of asthma and distinguish patients who will benefit from inhaled corticosteroids from those who will not. Second, Fe(NO) is helpful in predicting exacerbations, and predicting successful steroid reduction or withdrawal. In atopic asthmatic children Fe(NO) is beneficial in adjusting steroid doses, discerning those patients who require additional therapy from those whose medication dose could feasibly be reduced. In pre-school children Fe(NO) may be of help in the differential diagnosis of respiratory symptoms, and may potentially allow for better targeting and monitoring of anti-inflammatory treatment.

Markers of lung disease in exhaled breath: nitric oxide

Management of airway inflammation requires proper monitoring and treatment to improve long-term outcomes. However, achieving this goal is difficult, as current methods have limitations. Although nitric oxide (NO) was first identified 200 years ago, its physiological importance was not recognized until the early 1980s. Many studies have established the role of NO as an essential messenger molecule in body systems. In addition, studies have demonstrated a significant relationship between changes in exhaled NO levels and other markers of airway inflammation. The technique used to measure NO in exhaled breath is noninvasive, reproducible, sensitive, and easy to perform. Consequently, there is growing interest in the use of exhaled NO in the management of asthma and other pulmonary conditions. The purpose of this review is to promote a basic understanding of the physiologic actions of NO, measurement techniques, and ways that research findings might translate to future application in clinical practice. Specifically, the article will review the role of exhaled NO in regard to its historical background, mechanisms of action, measurement techniques, and implications for clinical practice and research.

The Effects of Age on Exhaled Breath Nitric Oxide Levels

A variety of factors influence exhaled breath nitric oxide (ENO) but few studies have examined ENO at the extremes of adult age. This investigation explores whether there is a difference in ENO between groups of older and younger individuals. A total of 48 normal subjects consisting of 23 younger (median age - 24 years) and 25 older (median age - 72 years) participants were studied. Carefully defined clinical and spirometric parameters, smoking history, and drug/medication documentation were determined to insure normalcy. Measurements of ENO were made using ATS/ERS recommended methodologies. The older group consistently showed higher ENO concentrations than-the younger subjects; median ENO values were 36.9 and 18.7 ppb, respectively (p < 0.001). The statistical significance held true when adjusting for multiple testing with the Holm method and accounting for outliers and medication usage. ENO levels are significantly higher in a normal older population. Comparing ENO between individuals at the extremes of age may depict differences more decidedly. Whether elevated ENO reflects underlying airway inflammation in older persons remains unanswered. It is possible that the difference in NO concentrations between older and younger groups represents only a marker of past oxidant exposures and holds no clinical significance. Additional investigations are necessary to elucidate the mechanisms and significances of elevated NO levels in the aged.

Time-Dependent Effect of Nitrate-Rich Meals on Exhaled Nitric Oxide in Healthy Subjects

BACKGROUND

Exhaled nitric oxide (eNO) is a convenient noninvasive marker for airway inflammation in several pulmonary diseases. However, external factors such as nitrate-rich nutrition can affect the levels of eNO and thus compromise its diagnostic value.

STUDY OBJECTIVES

The objective of this investigation was to have a better understanding of the time-dependent effect of nitrate-rich meals on eNO in healthy subjects.

STUDY DESIGN

Forty-two healthy, nonsmoking volunteers (age range, 25 to 62 years) were recruited for the study. They had no recent respiratory tract infections and were free of pulmonary history, rhinitis, and atopic disorders. eNO was measured before, and 0.5, 2, 4, 12, 15, and 20 h after the intake of a nitrate-rich meal equivalent to 230 mg of nitrate.

RESULTS

The intake of a nitrate-rich meal increased eNO by 60% 2 h after the meal. Even after 15 h, the mean eNO value was still 22% higher than the baseline value. Only after 20 h did eNO return to the normal baseline level.

CONCLUSION

This finding stresses the importance of advising patients to avoid nitrate-rich nutrition at least 20 h before a scheduled measurement of eNO.