Relationship between exhaled air temperature and exhaled nitric oxide in childhood asthma

Validation of the fractional exhaled breath temperature measurement: reference values

Exhaled breath temperature (EBT) is a known biomarker of inflammation and airways blood flow. As opposed to previous studies, we were able to measure temperature of separate fractions of exhaled breath (fEBT) (those from the peripheral and central airways). The aim was to validate the fEBT measurement method to determine the reference values and the influence of endogenous and exogenous factors on fEBT in healthy subjects. This cross-sectional study included 55 healthy adults in whom fEBT was repeatedly measured, two days in a row, using a FractAir^®device. Also, basal metabolic rate, level of physical activity, distance from the main road, outdoor and ambient temperature, air pressure and humidity, haematology and inflammation markers, lung function, cumulative EBT and body temperature at characteristic points on the body were measured. The results showed that fEBT from central airways was lower compared to fEBT from the periphery and that fEBTs were not related to body temperature (p> 0.05 for all). We also showed repeatability of fEBT measurements for two consecutive days. All EBT fractions correlated significantly with ambient temperature (<0.01). No associations of fEBT with other personal and external factors were found using multivariate analysis. At room temperature of 22 °C, the physiological temperature values of the first fraction were 23.481 ± 3.150 °C, the second fraction 26.114 ± 4.024 °C and the third fraction 28.216 ± 3.321 °C. The proposed reference values represent the first part of validation of fEBT as the method for the use in clinical practice.

Medical devices in allergy practice

Medical devices provide people with some health benefits in terms of diagnosis, prevention, treatment, and monitoring of disease processes. Different medical specialties use varieties of medical devices more or less specific for them. Allergology is an interdisciplinary field of medical science and teaches that allergic reactions are of systemic nature but can express themselves at the level of different organs across the life cycle of an individual. Subsequently, medical devices used in allergology could be regarded as: 1) general, servicing the integral diagnostic and management principles and features of allergology, and 2) organ specific, which are shared by organ specific disciplines like pulmonology, otorhinolaryngology, dermatology, and others. The present position paper of the World Allergy Organization (WAO) is meant to be the first integral document providing structured information on medical devices in allergology used in daily routine but also needed for sophisticated diagnostic purposes and modern disease management. It is supposed to contribute to the transformation of the health care system into integrated care pathways for interrelated comorbidities.

Fraction of air coming from conductive airways has the negative balance in heat dissipation after maximal effort exercise-a physiological basis for exercise-induced bronchoconstriction

Exhaled breath temperature (EBT) has recently been used as a tool to assess the level of inflammation in airways. The newest technology can also assess EBT coming from different fractions of exhaled air (fEBT). We aimed to assess the changes in fEBT after a maximal cardio-pulmonary exercise test in healthy athletes. Forty-four healthy professional athletes (two females) were included. Their mean (±SD) age was 22.9 ± 4.8 years. An innovative device (FractAir^®) was used for fEBT measurement, dividing the exhaled air into three fractions (V1, V2 and V3) coming from different parts of the lungs; the large airways (anatomic dead space), conductive airways (functional dead space) and the peripheral part. For V3 an EBT point measured at 1200 ml of exhaled volume was used to obtain the information about the distant parts of the lungs while eliminating the difference in the volume of total exhaled air before and after the exercise. The difference (temperature gain) between the starting and peak EBT for each fraction was also calculated. The peak fEBT values before and after exercise did not differ significantly (p > 0.05 for all three fractions). Temperature gain analysis for each fEBT showed a significant fall after exercise for V2 (1.71 °C ± 0.43 versus 1.38 °C ± 0.50, p < 0.001), but not for the other two fractions (p > 0.05 for both). The lower heat emission from this part of the airway (conductive airway) after exercise could mean that during hyperventilation heat emission is increased in this specific fraction. We can conclude that the changes of fEBT after physical exercise are not linear. They affect different fractions of the lungs in different ways, and the relationship between flow and volume on one side and the temperature of exhaled air on the other can vary significantly.

[Predictive significance of exhaled breath temperature for airway inflammation changes in children with asthma]

OBJECTIVE

To explore the predictive significance of exhaled breath temperature (EBT) for airway inflammation changes in children with asthma.

METHODS

A total of 60 children with asthma who met the inclusion criteria at the first visit were chosen as the asthma group, and 60 healthy children were selected as the control group. The EBT level was measured by the latest third-generation product (X-halo). The Childhood Asthma Control Test (C-ACT) score was recorded. EBT level and C-ACT score were compared between the asthma and control groups. At the subsequent visit one month later, the children were divided into well-controlled, partially-controlled, and uncontrolled groups according to their C-ACT scores. The EBT level and the FeNO level of the three groups were measured. EBT level and C-ACT score were compared among the three groups. The correlation between EBT and FeNO was analyzed. The data of initial diagnosis were reviewed, the EBT level and C-ACT score at the first visit were compared among the three groups, and the differences in EBT level and C-ACT score among the three groups at the second and first visits were evaluated.

RESULTS

At the first visit, the asthma group had a significantly higher EBT and a significantly lower C-ACT score compared with the control group (P<0.05). At the time of the subsequent visit, there was a significant difference in EBT level between the three groups, i.e., uncontrolled group > partially-controlled group > well-controlled group (P<0.05), and there was also a significant difference in C-ACT score between the three groups, i.e., well-controlled group > partially-controlled group > uncontrolled group (P<0.05). There were no significant differences in EBT level and C-ACT score at the first visit between the three groups. From the first visit to the subsequent visit, EBT level was significantly decreased in the well-controlled group (P<0.05), but significantly increased in both partially-controlled group uncontrolled groups (P<0.05); C-ACT score was significantly increased in the well-controlled and partially-controlled groups (P<0.05), but significantly decreased in the uncontrolled group (P<0.05). EBT and FeNO levels at the subsequent visit were positively correlated with each other in the uncontrolled group (P<0.05).

CONCLUSIONS

EBT has predictive significance for the changes in airway inflammation in children with asthma.

Exhaled breath temperature as a tool for monitoring asthma control after an attack in children

BACKGROUND

Exhaled breath temperature (EBT) has been suggested as a non-invasive marker of airway inflammation in asthma. There have been no studies examining longitudinal changes in EBT following asthma attacks.

OBJECTIVE

To investigate changes in EBT during and after an asthma attack and to relate these changes to changes in respiratory physiological measurements.

METHODS

We evaluated 38 hospitalized children aged 5-18 years diagnosed with an asthma attack. Spirometry was performed upon hospitalization. During hospitalization, EBT, peak expiratory flow rate (PEFR), and asthma score were measured daily. These tests were repeated 1 week and 1 month after discharge. The overall PEFR change, temporal changes in plateau values at the end of expiration, and time-dynamic associations were evaluated using linear mixed models.

RESULTS

FEV₁ was lower at admission than at discharge (63.3 ± 24 vs 99.5 ± 14 percent of predicted, P < 0.001). The EBT was higher at admission than at 1 week after discharge (34.1°C [range: 33.9-34.8°C] vs 33.6°C [range: 33.0-34.2°C], P = 0.007); overall, EBTs decreased over time (P = 0.007). Among individual subjects, decreased EBT was correlated with increased PEFR over time. Furthermore, plateau values at the end of expiration had a time-dependent, dynamic association with the PEFR during hospitalization (P = 0.005) and between asthma attack onset and asthma status stabilization (P = 0.032).

CONCLUSIONS

The EBT was elevated during asthma attacks and gradually decreased until asthma was well controlled. The EBT may be a useful, non-invasive tool for monitoring asthma control in children.

Exhaled biomarkers in childhood asthma: old and new approaches

Background

Asthma is a chronic condition usually characterized by underlying inflammation. The study of asthmatic inflammation is of the utmost importance for both diagnostic and monitoring purposes. The gold standard for investigating airway inflammation is bronchoscopy, with bronchoalveolar lavage and bronchial biopsy, but the invasiveness of such procedures limits their use in children. For this reason, in the last decades there has been a growing interest for the development of noninvasive methods.

Main body

In the present review, we describe the most important non-invasive methods for the study of airway inflammation in children, focusing on the measure of the fractional exhaled nitric oxide (feNO), on the measure of the exhaled breath temperature (EBT) and on the analysis of both exhaled breath condensate (EBC) and exhaled air (Volatile Organic Compounds, VOCs), using targeted and untargeted approaches. We summarize what is currently known on the topic of exhaled biomarkers in childhood asthma, with a special emphasis on emerging approaches, underlining the role of exhaled biomarkers in the diagnosis, management and treatment of asthma, and their potential for the development of personalized treatments.

Conclusion

Among non-invasive methods to study asthma, exhaled breath analysis remains one of the most interesting approaches, feNO and “-omic” sciences seem promising for the purpose of characterizing biomarkers of this disease.

Athletes Do Not Condition Inspired Air More Effectively than Nonathletes during Hyperpnea

Endurance athletes have a high prevalence of airway diseases, some possibly representing adaptive mechanisms to the need of conditioning large volumes of inspired air during high ventilation in specific environments. The aim of this study is to assess the ability to condition (warm and humidify) inspired air in athletes by measuring the difference between inhaled and exhaled air temperature (ΔT) during and after eucapnic voluntary hyperpnea (EVH) test.

METHODS

Twenty-three endurance athletes from various sports, 12 with airway hyperresponsiveness (AHR) and/or exercise-induced bronchoconstriction (EIB) (A+), 11 without AHR and/or EIB (A-), 12 nonathletes with AHR and/or EIB (C+), and 11 nonathletes without AHR and/or EIB (C-) were recruited. All subjects attended the laboratory on three occasions, twice for baseline characterization, including questionnaires, pulmonary function, methacholine bronchoprovocation, allergy skin prick tests, exhaled nitric oxide measurement, and a standard EVH, and once to perform a modified EVH to assess ΔT. Inspired and expired air temperatures were measured with a high-precision probe during EVH and at regular intervals until 30 min after the end of the test.

RESULTS

The global ΔT during the EVH was +5.8°C ± 1.5°C and +4.7°C ± 1.5°C during the 30 min after the EVH. No difference was found between groups for either the ΔT or the slope of ΔT, during and after the EVH.

CONCLUSION

This study shows no evidence of improved capacity to condition inspired air in endurance athletes, which could have suggested an increased bronchial blood flow or another adaptive mechanism. The absence of an adaptive mechanism could therefore contribute to airway damage observed in athletes in allowing colder but mainly dryer air to penetrate deeper in the lung.

A novel modelling approach to energy transport in a respiratory system

In this paper, energy transport in a respiratory tract is modelled using the finite element method for the first time. The upper and lower respiratory tracts are approximated as a 1-dimensional domain with varying cross-sectional and surface areas, and the radial heat conduction in the tissue is approximated using the 1-dimensional cylindrical coordinate system. The governing equations are solved using 1-dimensional linear finite elements with convective and evaporative boundary conditions on the wall. The results obtained for the exhalation temperature of the respiratory system have been compared with the available animal experiments. The study of a full breathing cycle indicates that evaporation is the main mode of heat transfer, and convection plays almost negligible role in the energy transport. This is in-line with the results obtained from animal experiments.

The added value of exhaled breath temperature in respiratory medicine

Recognition of the huge economic burden chronic respiratory diseases pose for society motivated fundamental and clinical research leading to insight into the role of airway inflammation in various disease entities and their phenotypes. However, no easy, cheap and patient-friendly methods to assess it have found a place in routine clinical practice. Measurement of exhaled breath temperature (EBT) has been suggested as a non-invasive method to detect inflammatory processes in the airways as a result of increased blood flow within the airway walls. As EBT values are within a narrow range, the thermometers designed for the purpose of assessing it need to be precise and very sensitive. EBT increases linearly over the pediatric age range and seems to be influenced by gender, but not by height and body weight. In non-smoking individuals with no history of respiratory disease EBT has a natural circadian peak about noon and increases with food intake and physical exercise. When interpreting EBT in subjects with alleged airway pathology, the possibilities of tissue destruction (chronic obstructive pulmonary disease, cystic fibrosis) or excessive bronchial obstruction and air trapping (severe asthma) need to be considered, as these conditions drive (force) EBT down. A prominent advantage of the method is to assess EBT when patients are in a steady state of their disease and to use this 'personal best' to monitor them and guide their treatment. Individual devices outfitted with microprocessors and memory have been created, which can be used for personalized monitoring and disease management by telemedicine.

Evaluation of exhaled breath temperature (EBT) as a marker and predictor of asthma exacerbation in children and adolescents

INTRODUCTION

Noninvasive and easy-to-use tools to monitor airway inflammation in asthma are needed to maintain disease control, particularly in pediatric population. The aim of the study was to evaluate exhaled breath temperature (EBT) in pediatric respiratory clinic setting.

METHODS

We evaluated 37 children and adolescents with asthma (5-17 years; median: 11 years). The patients were followed up in stable condition and during exacerbations (paired observations in n = 19 subjects). We evaluated medication use, EBT, fractional exhaled nitric oxide (FeNO), spirometry and atopic status of patients.

RESULTS

EBT was significantly higher in children with asthma exacerbation {entire group: median [interquartile range (IQR)]: 32.3 [1.1]°C vs. 33.8 [1.7]°C; p < 0.001 and mean ± SD: 33.1 ± 1.0°C vs. 33.6 ± 1.1°C; p = 0.038 for paired observations}. Significant correlation was observed between EBT and FeNO in the entire group (r = 0.22; p = 0.03). No difference was observed in EBT median values in atopic and non-atopic subjects in the entire group (median [IQR]: 32.6 [1.6] vs. 32.7 [2.0]; p = 0.88) and in subgroups. There was no difference in EBT values in patients receiving systemic or inhaled glucocorticosteroids (p = 0.45 and 0.83). There was no significant correlation between EBT and body or room temperature. The only significant predictor of exacerbation in logistic regression model was EBT {aOR = 2.4; 95% [confidence interval (CI)]: 1.4-4.1}. ROC analysis demonstrated applicability of EBT as a marker of asthma exacerbation in children (AUC = 0.748; p < 0.001; cut-off = 33.3°C; sensitivity: 64.3%; specificity: 82.1%).

CONCLUSIONS

We suggest that EBT may serve as marker and predictor of asthma exacerbation in children. EBT follow-up may be useful in asthma monitoring in children and adolescents.

Is the Exhaled Breath Temperature Sensitive to Cigarette Smoking?

The smoking habit is accompanied by an acute inflammatory response which follows tissue injury. It would be desirable to find a non-invasive inflammatory marker that would simplify the task of studying and monitoring smokers more simply and allow us to identify populations at risk of contracting Chronic Obstructive Pulmonary Disease (COPD). Today's expectations regarding research focus on issues ranging from inflammatory markers to those of exhaled breath temperature (EBT) are considerable. That said, although the EBT has been largely studied in asthma and COPD, there have not been any studies thus far that have analysed the effect of cigarette smoking on the EBT.  Bearing this in mind, in this longitudinal study we aim to analyse the EBT in current smokers, monitor the effects both of cigarette smoking on EBT and of what happens after smoking cessation. Twenty-five (25) smokers (59.5 ± 3.1 yrs, 12 M) who participated in a multi-disciplinary smoking cessation programme and 25 healthy never-smokers (58.7 ± 2.9, 13 M) underwent EBT measurement. EBT values were higher in smokers before smoking (T0) than in never-smokers [34.6 (34.2-35) vs 33.2 (32.4-33.7)°C, p < 0.001. The smokers repeated measurement 5 minutes after smoking a cigarette (T1) and 2 hours after (T2). They repeated EBC measurement after 1 week (T3) and then after 3 months (T4) from smoking cessation. EBT is higher in smokers compared to controls. EBT increases after cigarette smoking and progressively decreases with the increase of time from when the last cigarette was smoked.  Thus, we can conclude that EBT is increased in smokers and also sensitive to the acute effect of cigarette smoke.

Exhaled breath temperature measurement and asthma control in children prescribed inhaled corticosteroids: A cross sectional study

BACKGROUND

Exhaled breath temperature (EBT) reflects airways (both eosinophilic and neutrophilic) inflammation in asthma and thus may aid the management of children with asthma that are treated with anti-inflammatory drugs. A new EBT monitor has become available that is cheap and easy to use and may be a suitable monitoring device for airways inflammation. Little is known about how EBT relates to asthma treatment decisions, disease control, lung function, or other non-invasive measures of airways inflammation, such as exhaled nitric oxide (ENO).

OBJECTIVE

To determine the relationships between EBT and asthma treatment decision, current control, pulmonary function, and ENO.

METHODS

Cross-sectional prospective study on 159 children aged 5-16 years attending a pediatric respiratory clinic. EBT was compared with the clinician's decision regarding treatment (decrease, no change, increase), asthma control assessment (controlled, partial, uncontrolled), level of current treatment (according to British Thoracic Society guideline, BTS step), ENO, and spirometry.

RESULTS

EBT measurement was feasible in the majority of children (25 of 159 could not perform the test) and correlated weakly with age (R = 0.33, P = <0.01). EBT did not differ significantly between the three clinician decision groups (P = 0.42), the three asthma control assessment groups (P = 0.9), or the current asthma treatment BTS step (P = 0.57).

CONCLUSIONS & CLINICAL IMPLICATIONS

EBT measurement was not related to measures of asthma control determined at the clinic. The routine intermittent monitoring of EBT in children prescribed inhaled corticosteroids who attend asthma clinics cannot be recommended for adjusting anti-inflammatory asthma therapy.

Exhaled breath temperature in elite swimmers: The effects of a training session in adolescents with or without asthma

BACKGROUND

Cooling of the airways and inflammation have been pointed as possible mechanisms for exercise-induced asthma (EIA). We aimed to investigate the effect of training and asthma on exhaled breath temperature (EBT) of elite swimmers.

METHODS

Elite swimmers annually screened (skin prick tests, spirometry before and after salbutamol inhalation, induced sputum cell counts, and methacholine bronchial challenge) at our department (n = 27) were invited to this prospective study. Swimmers who agreed to participate in the present study (n = 22, 10 with asthma) had axillary temperature and EBT measured (X-halo(®) ) before and after a swimming training session (aerobic/non-aerobic). Linear regression models were used to assess the effect of asthma and other possible explanatory variables (demographics, PD20 , baseline EBT, training intensity, axillary temperature, and the number of hours trained in that week) on EBT change.

RESULTS

EBT significantly increased after training independently of lung function, airway responsiveness, and inflammation in all swimmers (mean ± SD: 0.32 ± 0.57; p = 0.016). No differences were observed between asthmatic swimmers and others. A significant correlation was observed between baseline and post-exercise EBTs (r = 0.827, p < 0.001). Asthma was not a predictor of ΔEBT after adjusting for confounders; baseline EBT was the variable most strongly associated with ΔEBT, explaining by itself alone 46% of the outcome (r(2) = 0.464).

CONCLUSION

Although these are preliminary data, a relationship between airway's inflammation and respiratory heat loss during exercise could not be confirmed, suggesting that the increase in exhaled breath temperature is a physiologic rather than a pathological response to exercise.

Usefulness of the Exhaled Breath Temperature Plateau in Asthma Patients

BACKGROUND

Exhaled breath temperature (EBT) has recently been proposed as a noninvasive marker of bronchial inflammation in patients with asthma. However, the usefulness of EBT in everyday clinical practice is not well established. Results to date are contradictory and are mainly derived from small, pediatric populations. A comparison of results is further complicated by the use of different equipment and measurements.

OBJECTIVE

We performed a comprehensive study to determine whether EBT is related to asthma control, disease severity, bronchial obstruction, or bronchial inflammation.

METHODS

Sixty-nine patients on maintenance treatment for asthma were included in a cross-sectional study. At the same visit, we measured the EBT plateau (EBTp) using an X-halo Breath Thermometer (Delmedica, Singapore), the fraction of exhaled nitric oxide (FeNO), spirometry, and inflammatory cell count in induced sputum, and we administered the Asthma Control Test questionnaire.

RESULTS

No significant differences were found between EBTp measurements and the level of asthma control, disease severity, bronchial obstruction, FeNO levels, or inflammatory asthma phenotypes. We found a significant difference between EBTp and gender. The EBTp was 34.07°C (SD 0.74) in women and 34.38°C (0.46) in men (p = 0.038). We also found a significant correlation between EBTp measurements and the induced sputum eosinophil count (R = -0.348, p = 0.003).

CONCLUSIONS

The results of this study do not support the usefulness of the EBTp in asthma management in routine clinical practice. Further research using standardized methods is needed to determine the potential use of the EBTp measurement in asthma management.

Usefulness of noninvasive methods for the study of bronchial inflammation in the control of patients with asthma

Bronchial asthma is one of the most prevalent respiratory conditions. Although it is defined as an inflammatory disease, the current guidelines for both diagnosis and follow-up of patients are based only on clinical and lung function parameters. Current research is focused on finding markers that can accurately predict future risk, and on assessing the ability of these markers to guide medical treatment and thus improve prognosis. The use of noninvasive methods to study airway inflammation is gaining increasing support. The study of eosinophils in induced sputum has proved useful for the diagnosis of asthma; however, its clinical implementation is complex. Some studies have shown that the measurement of exhaled nitric oxide (FeNO) may also be useful to establish disease phenotypes and improve control. Others have found that the measurement of pH and certain markers of oxidative stress, cytokines and prostanoids in exhaled breath condensate (EBC) may also be useful as well as the measurement of the temperature of exhaled breath and the analysis of volatile organic compounds (VOCs). In conclusion, since asthma is an inflammatory disease, it seems appropriate to try to control it through the study of airway inflammation using noninvasive methods. In this regard, the analysis of induced sputum cells has proved very useful, although the clinical implementation of this technique seems difficult. Other techniques such as temperature measurement, the analysis of FeNO, the analysis of the VOCs in exhaled breath, or the study of certain biomarkers in EBC require further study in order to determine their clinical applicability.

Exhaled nitric oxide and other exhaled biomarkers in bronchial challenge with exercise in asthmatic children: current knowledge

The fractional concentration of exhaled nitric oxide (FENO), a known marker of atopic-eosinophilic inflammation, may be used as a surrogate to assess exercise-induced bronchoconstriction (EIB) in asthmatic children. The predictive value of baseline FENO for EIB appears to be influenced by several factors, including age, atopy, current therapy with corticosteroids and measurement technique. Nonetheless, FENO cut-off values appear to be able to rule out EIB. FENO levels decrease during EIB, apparently through neural mechanisms rather than by decreased airway-epithelial surface. Partition of FENO into proximal and peripheral contributions of the respiratory tract may improve our understanding on NO exchange during exercise and help to screen subjects prone to EIB. Other biomarkers of inflammation and oxidative stress contained in exhaled gases and exhaled breath condensate (EBC) may shed light on the pathophysiology of EIB. Exhaled breath temperature is a promising real-time measurement whose routine use for assessing EIB warrants further investigation.

Tidal-breathing measurement of exhaled breath temperature (EBT) in schoolchildren

BACKGROUND

Non-invasive assessment of airway inflammation is particularly useful in children. The exhaled breath temperature (EBT) may reflect inflammatory vasodilation and serve to assess respiratory symptoms and therapy with inhaled corticosteroids (ICs).

AIMS

To compare EBT with other non-invasive measurements in unselected schoolchildren in relation to respiratory symptoms and IC-therapy, as well as to assess reproducibility, and potentially influencing factors.

METHODS

In 298 Italian schoolchildren, we assessed tidal-EBT, FE(NO), spirometry, skin-prick tests, questionnaires on chronic respiratory symptoms, and medication. Subjects were divided as follows: reported wheeze, respiratory symptoms other than wheeze, and without symptoms.

RESULTS

Subjects with reported wheeze (n = 30) more frequently presented atopy, respiratory symptoms, higher FE(NO), lower lung function than subjects with symptoms other than wheeze (n = 141) and those without symptoms (n = 127), but had a similar EBT. IC-treated children (5 wheeze, 9 respiratory symptoms other than wheeze, 4 without chronic symptoms) had lower median (interquartile range) EBT levels than IC-untreated children (n = 280) [EBT: 31.7 (30.1-32.5) vs. 32.6 (31.4-33.4), P = 0.027]. Duplicate EBT measurements were highly reproducible (ICC = 0.94). In a multiple linear-regression model, EBT was explained by age, weight, duration of EBT measurement, FE(NO), and ambient temperature (r = 0.63, P < 0.001).

CONCLUSION

Tidal-EBT measurements are easy to perform, reproducible, though symptom misclassification may affect the results obtained regarding the effect of IC therapy. Factors influencing EBT should be addressed in further epidemiological studies.

Exhaled breath temperature in patients with stable and exacerbated COPD

The measurement of the peak exhaled breath temperature (EBT) during multiple tidal breaths offers an easy, non-invasive tool for monitoring airway inflammation. Chronic obstructive pulmonary disease (COPD) is linked to airway inflammation, which is further aggravated by exacerbations of the disease. However, the peak EBT has not been studied in patients with COPD. The breath temperature was measured (X-halo, Delmedica Investments) in 19 control non-smoking subjects (age: 28  ±  11 years, mean ± standard deviation), 19 control smoking/ex-smoking subjects (53  ±  9 years), 20 patients with stable COPD (66  ±  8 years), and 17 patients with COPD at onset and also after recovery from an acute exacerbation (AECOPD; 65  ±  10 years). Spontaneous sputa were collected in AECOPD. The intra-class correlation coefficient of the repeated EBT measurements in non-smokers was 0.87 (95% confidence interval: 0.70-0.95). The peak EBT was different between the subject groups (Kruskal-Wallis test, p = 0.02), with lower values in the patients with stable COPD (34.00/33.35-34.34/°C; median /interquartile range/) than in the smoking/ex-smoking control subjects (34.51/34.20-34.68/°C, p < 0.05). The EBT was higher at the onset of AECOPD (34.58/34.12-34.99/°C, p < 0.05) compared to in a stable condition, and positively correlated with the sputum leukocyte count (p = 0.049, r2 = 0.30; Spearman test) and neutrophil percentage (p = 0.03, r(2) = 0.36). The breath temperature decreased after recovery from AECOPD (34.10/33.72-34.43/°C, p = 0.008; Wilcoxon test). The peak exhaled breath temperature, recorded during multiple tidal breaths, increases with an acute exacerbation of COPD, and may be related to accelerated airway inflammation. The application of exhaled breath temperature measurements when monitoring the activity of COPD should be further assessed in longitudinal studies.

Objective approach for fending off the sublingual immunotherapy placebo effect in subjects with pollenosis: double-blinded, placebo-controlled trial

BACKGROUND

Symptom scoring for the assessment of allergen immunotherapy is associated with a substantial placebo effect.

OBJECTIVE

To assess the ability of exhaled breath temperature (EBT), a putative marker of airway inflammation, to evaluate objectively the efficacy of grass pollen sublingual immunotherapy in a proof-of-concept study.

METHODS

This was a double-blinded, placebo-controlled clinical trial in 56 subjects (mean ± SD 30 ± 12 years old, 33 men) sensitized to grass pollen. The objective measurements were EBT, spirometry, and periostin and high-sensitivity C-reactive protein in blood. Overall discomfort scored on a visual analog scale was used as a proxy for subjective symptoms. Evaluations were performed before, during, and after the grass pollen season.

RESULTS

Fifty-one subjects (25 and 26 in the active treatment and placebo groups, respectively) were assessed before and during the pollen season. The mean pre- vs in-season increase in EBT was significantly smaller (by 59.1%) in the active treatment than in the placebo group (P = .030). Of the other objective markers, only the blood periostin level increased significantly during the pollen season (P = .047), but without intergroup differences. Subjectively, the mean pre- vs in-season increase in the visual analog scale score was 32.3% smaller in the active treatment than in the placebo group, although this difference did not reach statistical significance (P = .116).

CONCLUSION

These results suggest that the efficacy of grass pollen sublingual immunotherapy can be assessed by EBT, a putative quantitative measurement of airway inflammation, which is superior in its power to discriminate between active and placebo treatment than a subjective assessment of symptoms assessed on a visual analog scale.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01785394.

Exhaled breath temperature in children: reproducibility and influencing factors

OBJECTIVE

This study will investigate the reproducibility and influencing factors of exhaled breath temperature measured with the tidal breathing technique in asthmatic patients and healthy children.

METHODS

Exhaled breath temperature, fractional exhaled nitric oxide, and spirometry were assessed in 124 children (63 healthy and 61 asthmatic), aged 11.2 ± 2.5 year, M/F 73/51. A modified version of the American Thoracic Society questionnaire on the child's present and past respiratory history was obtained from parents. Parents were also asked to provide detailed information on their child's medication use during the previous 4 weeks. Ear temperature, ambient temperature, and relative-ambient humidity were also recorded.

RESULTS

Exhaled breath temperature measurements were highly reproducible; the second measurement was higher than the first measurement, consistent with a test-retest situation. In 13 subjects, between-session within-day reproducibility of exhaled breath temperature was still high. Exhaled breath temperature increased with age and relative-ambient humidity. Exhaled breath temperature was comparable in healthy and asthmatic children; when adjusted for potential confounders (i.e. ambient conditions and subject characteristics), thermal values of asthmatic patients exceeded those of the healthy children by 1.1 °C. Normalized exhaled breath temperature, by subtracting ambient temperature, was lower in asthmatic patients treated with inhaled corticosteroids than in those who were corticosteroid-naive.

CONCLUSION

Measurements of exhaled breath temperature are highly reproducible, yet influenced by several factors. Corrected values, i.e. normalized exhaled breath temperature, could help us to assess the effect of therapy with inhaled corticosteroids. More studies are needed to improve the usefulness of the exhaled breath temperature measured with the tidal breathing technique in children.

Neutrophil elastase-mediated increase in airway temperature during inflammation

BACKGROUND

How elevated temperature is generated during airway infections represents a hitherto unresolved physiological question. We hypothesized that innate immune defence mechanisms would increase luminal airway temperature during pulmonary infection.

METHODS

We determined the temperature in the exhaled air of cystic fibrosis (CF) patients. To further test our hypothesis, a pouch inflammatory model using neutrophil elastase-deficient mice was employed. Next, the impact of temperature changes on the dominant CF pathogen Pseudomonas aeruginosa growth was tested by plating method and RNAseq.

RESULTS

Here we show a temperature of ~38°C in neutrophil-dominated mucus plugs of chronically infected CF patients and implicate neutrophil elastase:α1-proteinase inhibitor complex formation as a relevant mechanism for the local temperature rise. Gene expression of the main pathogen in CF, P. aeruginosa, under anaerobic conditions at 38°C vs 30°C revealed increased virulence traits and characteristic cell wall changes.

CONCLUSION

Neutrophil elastase mediates increase in airway temperature, which may contribute to P. aeruginosa selection during the course of chronic infection in CF.

Exhaled breath temperature in asthmatics and controls after eucapnic voluntary hyperventilation and a methacholine challenge test

BACKGROUND

It has been suggested that exhaled breath temperature (EBT) is increased in asthmatic subjects.

OBJECTIVES

Our aim was to investigate EBT in asthmatics compared to healthy controls before and after eucapnic voluntary hyperventilation (EVH) and a methacholine challenge test (MCT).

METHODS

A total of 26 asthmatics and 29 healthy controls were included. Forced expiratory volume in 1 s (FEV1), EBT and oral, axillary and auricular temperatures were measured before and after EVH and MCT.

RESULTS

FEV1 % predicted (%p) was significantly lower in asthmatic subjects compared to healthy controls at all time points. EBT was significantly increased in all subjects 15-30 min after EVH and 5-45 min after MCT. Oral temperature displayed a similar pattern of increase, in contrast to axillary and auricular temperature, and correlated with EBT before and after both of the challenge tests. EBT after 5 min correlated with the largest drop in FEV1%p after EVH in asthmatic subjects. No significant differences or changes in EBT were found when comparing asthmatics to healthy controls before or after any of the tests.

CONCLUSIONS

EBT is increased after both EVH and MCT, possibly reflecting a vascular response. This is related to both the fall in FEV1 and to oral temperature, suggesting an effect on the whole respiratory tract including the oral cavity. No differences in EBT are seen between asthmatics and healthy controls, indicating that the increase in EBT is mainly physiological rather than pathophysiological.

Extreme temperatures and emergency department admissions for childhood asthma in Brisbane, Australia

OBJECTIVES

To examine the effect of extreme temperatures on emergency department admissions (EDAs) for childhood asthma.

METHODS

An ecological design was used in this study. A Poisson linear regression model combined with a distributed lag non-linear model was used to quantify the effect of temperature on EDAs for asthma among children aged 0-14 years in Brisbane, Australia, during January 2003-December 2009, while controlling for air pollution, relative humidity, day of the week, season and long-term trends. The model residuals were checked to identify whether there was an added effect due to heat waves or cold spells.

RESULTS

There were 13 324 EDAs for childhood asthma during the study period. Both hot and cold temperatures were associated with increases in EDAs for childhood asthma, and their effects both appeared to be acute. An added effect of heat waves on EDAs for childhood asthma was observed, but no added effect of cold spells was found. Male children and children aged 0-4 years were most vulnerable to heat effects, while children aged 10-14 years were most vulnerable to cold effects.

CONCLUSIONS

Both hot and cold temperatures seemed to affect EDAs for childhood asthma. As climate change continues, children aged 0-4 years are at particular risk for asthma.

Diffusion lung capacity of carbon monoxide: A novel marker of airways remodeling in asthmatic children?

Asthma is universally considered a chronic inflammatory disorder of the airways. Several noninvasive markers, such as exhaled nitric oxide (FeNO) and exhaled breath temperature (PletM), have been proposed to evaluate the degree of airway inflammation and remodeling in asthmatic children. The aim of this study was to evaluate the relationship between diffusion lung capacity of carbon monoxide (DLCO) and these inflammatory markers in asthmatic children. We compared data of FeNO, PletM, and DLCO collected in 35 asthmatic children at admission (T0) and discharge (T1) after a period spent in a dust-mite-free environment (Misurina, Italian Dolomites, 1756 m). PletM showed a reduction from 29.48°C at T0 to 29.13°C at T1 (p = 0.17); DLCO passed from 93 to 102 (p = 0.085). FeNO mean value was 29.7 ppb at admission and 18.9 ppb at discharge (p = 0.014). Eosinophil mean count in induced sputum was 4 at T0 and 2 at T1 (p = 0.004). Spearman standardization coefficient beta was 0.414 between eosinophils and FeNO and -0.278 between eosinophils and DLCO. Pearson's correlation index between DLCO and PletM was -0.456 (p = 0.019). A negative correlation between DLCO and PletM was found. However, DLCO did not show a significant correlation with FeNO and eosinophils in the airways. Additional studies are needed to clarify the role of DLCO as a potential tool in monitoring childhood asthma.

Nasal mucosa temperature as a marker of disease in children with allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is a symptomatic disorder of the nose induced after allergen exposure by an IgE-mediated inflammation of the nasal mucosa. This study was designed to investigate the role of nasal mucosa temperature in AR.

METHODS

We investigated the relationship between eosinophilic infiltration, nasal obstruction, and nasal mucosa temperature in 35 children with rhinitis aged 6-12 years.

RESULTS

A significant relationship was shown between nasal temperature values and eosinophil infiltration at nasal cytology (p < 0.01). Nasal temperature was also significantly associated with nasal obstruction, assessed in terms of nasal volume (Vol [2-5 cm]; p < 0.05) and minimum cross-sectional area (p < 0.01). No significant correlation emerged between the degree of nasal obstruction and presence of eosinophils at nasal cytology (p > 0.05).

CONCLUSION

These results suggest a relationship between nasal temperature and nasal mucosa inflammation and obstruction.

Exhaled breath temperature and exercise-induced bronchoconstriction in asthmatic children

It has been hypothesized that exhaled breath temperature (EBT) is related to the degree of airway inflammation/remodeling in asthma. The purpose of this study was to evaluate the relationship between the level of airway response to exercise and EBT in a group of controlled or partly controlled asthmatic children. Fifty asthmatic children underwent measurements of EBT before and after a standardized exercise test. EBT was 32.92 ± 1.13 and 33.35 ± 0.95°C before and after exercise, respectively (P < 0.001). The % decrease in FEV(1) was significantly correlated with the increase in EBT (r = 0.44, P = 0.0013), being r = 0.49 (P < 0.005) in the children who were not receiving regular inhaled corticosteroids (ICS) and 0.37 (n.s.) in those who were. This study further supports the hypothesis that EBT can be considered a potential composite tool for monitoring asthma.

Exhaled breath temperature increases after exercise in asthmatics and controls

BACKGROUND

Exhaled breath temperature (EBT) has been suggested as a marker of airway inflammation in asthma.

OBJECTIVES

The aim of the present study was to investigate EBT in asthmatic subjects compared to healthy controls after an exercise challenge test, and in subjects with exercise-induced bronchoconstriction compared to subjects without, and to compare with body temperatures.

METHODS

A total of 21 healthy controls and 20 asthmatics were included. Forced expiratory volume in 1 s (FEV(1)), EBT and oral, axillary and auricular temperatures were measured before and after an exercise challenge test.

RESULTS

FEV(1) % predicted (%p) was significantly lower in asthmatic subjects compared to healthy controls at all time points after exercise. The largest drop in FEV(1)%p correlated with EBT after 5 min. EBT increased markedly 5 min after exercise and remained high for at least 60 min. In asthmatics whose FEV(1) dropped by >10%, EBT was higher after 60 min compared to the remaining asthmatics. EBT correlated with oral temperature at all time points after exercise, with axillary temperature only at 15, 30 and 60 min, and not at all with auricular temperature.

CONCLUSIONS

EBT is increased after exercise, and elevated EBT correlated with a drop in FEV(1)%p. The immediate increase in EBT did not differ between asthmatics and controls but remained elevated in the asthmatics whose FEV(1) dropped by >10%, indicating a different vascular response.

Exhaled breath temperature in healthy children is influenced by room temperature and lung volume

BACKGROUND

Exhaled breath temperature (EBT) has been proposed for the non-invasive assessment of airway inflammation. Previous studies have not examined the influence of room temperature or lung size on the EBT.

OBJECTIVE

This study aimed to address these issues in healthy children.

METHODS

We assessed the effects of room temperature and lung volume in 60 healthy children aged 9-11 years (mean age 10.3 years, 33 male). Static lung volumes were assessed using multiple breath nitrogen washout. Questionnaire and skin prick tests were also used to establish respiratory health in the children. We obtained the EBT parameters of slope, end plateau temperature (PLET) and normalized plateau temperature (nPLET; plateau temperature minus inspired air temperature), and ascertained physiological factors influencing EBT.

RESULTS

End plateau temperature was shown to be proportionally affected by room temperature (r = 0.532, P < 0.001) whereas slope and nPLET decreased with increasing room temperature (r = -0.392 P < 0.02 and r = -0.507 P = 0.002). After adjusting for room temperature, height and age, the total lung capacity (r(2)  = 0.435, P = 0.006) and slow vital capacity (SVC; r(2)  = 0.44, P = 0.005) were found to be the strongest predictors of end PLET in healthy children. When all factors were included in a multiple regression model, SVC and room temperature were the only predictors of plateau and nPLET. Slope was only influenced by room temperature.

CONCLUSIONS

Exhaled breath temperature measurements are highly feasible in children with a 95% success rate in this healthy population. Room temperature and SVC significantly influence EBT variables in healthy children. Further studies are required to investigate the ability of EBT to assess airway inflammation in children with respiratory disease. Pediatr. Pulmonol. 2011; 46:1062-1068. © 2011 Wiley Periodicals, Inc.

Exhaled breath temperature, a new biomarker in asthma control: a pilot study

OBJECTIVE

To evaluate whether the exhaled breath temperature (EBT), measured by a noninvasive method, is an effective means of monitoring patients with uncontrolled asthma.

METHODS

A pilot study comprising nine patients (seven women and two men; mean age: 39 years) diagnosed with asthma at least one year prior to the beginning of the study and not having been under maintenance therapy for the last three months. In the first visit, the patients underwent spirometry and measurement of EBT. The patients were then instructed to use inhaled budesonide/formoterol (200/6 µg) every 12 h for six weeks. In addition, the patients with severe asthma (FEV1 < 60% of predicted) were instructed to use oral prednisolone (40 mg/day) for five days. After six weeks, the patients underwent the same tests.

RESULTS

All of the patients reported an improvement in the symptoms of asthma, as confirmed by a statistically significant increase in FEV1 from the first to the second visit (mean, 56.1% vs. 88.7% of predicted; p < 0.05). Five patients used oral prednisolone for the first five days of the treatment period. Six patients used additional doses of inhaled budesonide/formoterol (mean duration, 2.5 weeks). The EBT decreased significantly from the first to the second visit (mean EBT: 35.1 ºC vs. 34.1 ºC; p < 0.05).

CONCLUSIONS

Uncontrolled asthma, especially during exacerbations, is followed by an increase in EBT, which decreases after appropriate asthma control, as demonstrated by an increase in FEV1 and an improvement of the reported symptoms. These preliminary results suggest that EBT can be used as a parameter for the assessment of asthma control.

Human exhaled breath analysis

OBJECTIVE

To review the fast-developing topic of assessment of exhaled breath components to improve the diagnosis and monitoring of respiratory and systemic diseases.

DATA SOURCES

Review of the literature available in monographs and journals.

STUDY SELECTION

Articles and overviews on the broad spectrum of existing experimental and routinely applied methods to assess different aspects of human exhaled breath analysis were selected for presentation in this review.

RESULTS

Exhaled breath constitutes more than 3,500 components, the bulk of which are volatile organic compounds in miniature quantities. Many of these characterize the functioning of the organism as a whole (systemic biomarkers), but some are related to processes taking place in the respiratory system and the airways in particular (lung biomarkers). Assessment of lung biomarkers has proven useful in airway inflammatory diseases. It involves direct measurement of gases such as nitric oxide and inflammatory indicators in exhaled breath condensate such as oxidative stress markers (eg, hydrogen peroxide and isoprostanes), nitric oxide derivatives (eg, nitrate and nitrates), arachidonic acid metabolites (eg, prostanoids, leukotrienes, and epoxides), adenosine, and cytokines. Integral approaches have also been suggested, such as exhaled breath temperature measurement and devices of the "electronic nose" type, which enable the capture of approaches have also been suggested, such as exhaled breath temperature measurementexhaled molecular fingerprints (breath prints). Technical factors related to standardization of the different techniques need to be resolved to reach the stage of routine applicability.

CONCLUSIONS

Examination of exhaled breath has the potential to change the existing routine approaches in human medicine. The rapidly developing new analytical and computer technologies along with novel, unorthodox ideas are prerequisites for future advances in this field.

Exhaled air temperature in children with bronchopulmonary dysplasia

BACKGROUND

Because they have similar functional and clinical profiles, bronchopulmonary dysplasia (BPD) survivors are often treated as asthmatic patients. In truth, very little is known about the possible biochemical and inflammatory mechanisms playing a part in BPD survivors' lungs. The aim of this study was to measure exhaled breath temperature in BPD survivors by comparison with asthmatic cases and healthy controls.

METHODS

Three groups of age-matched adolescents (n = 17 each), that is, BPD survivors (gestational ages <31 weeks, birth weights <1,500 g), asthmatic subjects and healthy controls, underwent exhaled breath temperature and exhaled nitric oxide measurements, and spirometry.

RESULTS

Exhaled breath temperature was significantly lower in the BPD survivors (26.72°C [25.11-27.57]) than in the asthmatic patients (29.60°C [29.20-30.02], P < 0.001), while no significant difference emerged by comparison with healthy controls (26.97°C [26.58-27.38]). Considering the whole study population, a significant correlation was found between exhaled breath temperatures and exhaled nitric oxide concentrations (R = 0.42, P = 0.004). Spirometry revealed an obstructive lung function pattern in both the asthmatic cases and the BPD survivors, with lower parameters in the latter.

CONCLUSIONS

Exhaled breath temperatures and exhaled nitric oxide concentrations are significantly lower in BPD survivors than in asthmatic cases, suggesting that different pathogenetic mechanisms characterize these two chronic obstructive lung diseases.

Exhaled air temperature in asthmatic children: a mathematical evaluation

Recently, the exhaled breath temperature has been proposed as a potential marker for the evaluation of airway inflammation in asthma. The purpose of this study was to verify the ability to distinguish asthmatics from normal controls by a dedicated detailed mathematical evaluation of the exhaled air curve. Analysis was performed in the different phases of the curve of exhaled temperature, i.e. the rate of temperature increase (Delta e degrees T) and the mean plateau value. Principal components analysis (PCA) and artificial neural networks (ANNs) were used for the evaluation of the data in 90 asthmatic children and in 33 healthy age-matched controls. Both PCA and ANNs showed that a separation between patients and controls can be obtained only by the evaluation of the plateau phase of the curve, which better reflects the periphery of the airway.

Exhaled air temperature in asthma: methods and relationship with markers of disease

BACKGROUND

Exhaled breath temperature has been proposed as a surrogate marker for the evaluation of airway inflammation in asthmatic patients.

OBJECTIVE

The aim of the present study was to extend the investigation of exhaled air temperature as a means for the evaluation of airway inflammation using a professionally developed instrument.

METHODS

Fifty-seven children, 41 allergic mild asthmatics and 16 healthy controls have been evaluated. They underwent exhaled air temperature and lung function measurement. The asthmatic children also underwent exhaled nitric oxide measurement, and hypertonic saline sputum induction for the evaluation of eosinophil (EOS) percentage.

RESULTS

The level of exhaled temperature was significantly higher in asthmatics than in controls, being 30.18+/-0.14 degrees C vs. 27.47+/-0.24 degrees C (P<0.001). In asthmatic children, a positive relationship was observed between exhaled air temperature and both exhaled nitric oxide (r=0.39; P=0.01) and EOS percentage in samples from induced sputum (rho=0.53; P=0.04).

CONCLUSION

The data from the present study support the hypotheses that exhaled breath temperature is related to the degree of airway inflammation in asthma.

Evaluation of a simple, potentially individual device for exhaled breath temperature measurement

RATIONALE

Inflammation is a universal pathological reaction and is characterized among other things by increased heat production. The question stays whether the contribution of the inflamed lung tissues to the overall exhaled breath temperature (EBT) can be reliably detected and used in everyday clinical practice.

METHODS

We have designed a simple device for assessment of EBT and explored its performance under standard indoor conditions. We made our measurements in the morning hours, documenting the ambient conditions (room temperature, humidity, atmospheric pressure), and physiological characteristics of the tested subjects (heart rate, blood pressure, otic and axillary temperature). We assessed its day-to-day reproducibility in 17 healthy volunteers and its ability to discriminate between the same subjects without respiratory disease and uncontrolled asthmatics (n=14). We also compared the EBT of the 14 asthmatics before and after anti-inflammatory treatment.

RESULTS

No association was found between EBT and any of the ambient conditions: room temperature, atmospheric pressure and humidity. While otic and axillary temperatures, which were measured in parallel, maintained high correlation between each other (Spearman's rho=0.71, p<0.01), EBT did not show meaningful association with any of them. The EBT (degrees C) of asthmatics (median 35.45, range 34.12-36.09) was higher than that of controls (34.84, 32.29-35.84), (p=0.009, Mann-Whitney U test). Anti-inflammatory treatment brought down the EBT of the asthmatics (34.78, 33.23-36.06), (p=0.001, Wilcoxon Signed Ranks test), while significantly improving their spirometry too.

CONCLUSIONS

Measurements of EBT with the device we constructed are not significantly influenced by changes within the accepted range of a standard indoor environment. EBT represents a different characteristic of the human organism than otic and axillary temperatures. EBT is increased in uncontrolled asthmatics and decreases under anti-inflammatory treatment.

Analysis of expired air for oxidation products

Chronic inflammation is a critical feature of chronic obstructive pulmonary disease, cystic fibrosis, and asthma. This inflammation is associated with the increased production of reactive oxygen species or oxidative stress in the lungs. Oxidative stress may have several adverse effects and may amplify the inflammatory process; however, monitoring oxidative stress is difficult and may not be reflected by changes in blood markers. We have therefore developed several noninvasive markers in the exhaled breath that may indicate oxidative stress in the lungs, and we studied these in relationship to the severity of chronic inflammatory lung diseases. We analyzed the exhaled breath for the content of nitric oxide as a marker of inflammation, carbon monoxide as a marker of oxidative stress, and ethane, which is one of the end products of lipid peroxidation. In addition, we measured the concentration of markers of oxidative stress such as isoprostanes in exhaled breath condensate. Our results confirm that there are increased inflammation, oxidative stress, and lipid peroxidation in lung disease, as shown by elevated levels of nitric oxide, carbon monoxide, and ethane, respectively. The finding of lower levels of these gases in patients on steroid treatment and of higher levels in those with more severe lung disease, as assessed by lung function tests and clinical symptoms, reinforces the hypothesis that the noninvasive measurement of exhaled gases maybe useful in monitoring the underlying pathologic pathways of lung disease. Longitudinal studies are required to assess the clinical usefulness of these measurements in the monitoring of chronic inflammatory lung disease.