Exhaled Breath Temperature Measurement Research Articles

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.

Measurement of exhaled breath temperature in patients under general anesthesia: A feasibility study.

The aim of the present study was to investigate the respiratory parameters that influence the exhaled breath temperature (EBT) and the feasibility of using the latter to monitor the core temperature under general endotracheal anesthesia. A total of 20 patients undergoing abdominal surgery were included in the present study. At the first stage of the experiment, the respiratory rate was adjusted, while the other respiratory parameters [tidal volume, inspiratory and expiratory time ratio (TI:TE), and positive end expiratory pressure (PEEP)] were maintained at a constant level. At the second stage, the tidal volume was adjusted, while the other respiratory parameters were maintained at a constant level. At the third stage, the TI:TE was adjusted, while the other parameters were maintained at a constant level. At the fourth stage, PEEP was adjusted, while the other parameters were maintained at a constant level. In each experiment, the EBT, the maximum temperature of exhaled air in each min, the inhaled air temperature and the nasopharyngeal temperature (T nose) were recorded every min. During the first stage of the experiment, no significant difference was noted in the EBT at different levels of respiratory rate. During the second, third and fourth stage, no significant difference was noted in the EBT at different tidal volumes, TI:TE and PEEP, respectively. The EBT was significantly correlated with the T nose. Overall, the present study demonstrated that the EBT of patients undergoing abdominal surgery under general endotracheal anesthesia was not affected by the examined respiratory parameters and that it could be considered a feasible method of monitoring core temperature.

Exhaled Breath Temperature Home Monitoring to Detect NSCLC Relapse: Results from a Pilot Study.

Background Exhaled breath temperature (EBT) has been shown to reflect airway inflammation as well as increased vascularization, both involved in the pathogenesis of lung cancer. The aim of this study was to look for evidence that continuous EBT monitoring by such a device may help the early detection of relapse of lung cancer in patients with NSCLC who have been subjected to surgery with radical intent. Case Series. We included 11 subjects, who had been subjected to lung resection with radical intent for NSCLC in a prospective observational study. All patients received individual devices for EBT measurement and used them daily for 24 months after surgery. Subjects were also followed up by means of regular standard-of-care clinical and radiologic monitoring for lung cancer at four intervals separated by 6 months (T0, T1, T2, T3, and T4). In 5 patients, relapse of lung cancer was documented by means of lung biopsies. All of them recorded an elevation of their EBT at least one-time interval (T1), corresponding to 6 months, before the relapse was diagnosed at T4. The individual EBT graphs over time differed among these patients, and their mean EBT variability increased by +4% towards the end of 24 months of monitoring. By contrast, patients without a relapse did not document an elevation of their EBT and their variability decreased by -1.4%. Conclusions Our pilot study provided evidence that continuous EBT monitoring can help in the early detection of lung cancer relapse.

Fractional exhaled breath temperature in patients with asthma, chronic obstructive pulmonary disease, or systemic sclerosis compared to healthy controls

ABSTRACT Exhaled breath temperature has been suggested to reflect airway inflammation, and it would be plausible to measure the peripheral airway temperature as a correlate to peripheral airway inflammation. This study aims to explore the relative peripheral airway temperature in patients with asthma, chronic obstructive pulmonary disease (COPD) or systemic sclerosis (SSc) compared to healthy controls, and relate to lung function and exhaled nitric oxide. Sixty-five subjects (16 asthmatics, 18 COPD patients, 17 SSc patients and 14 healthy subjects) performed fractional exhaled breath temperature measurements using a novel device, fractional exhaled NO measurements, spirometry, impulse oscillometry, body plethysmography and CO-diffusion capacity test. A significant overall difference among all the patient groups was seen in both the Tmax (= peak values of the entire exhalation) and T3max (= peak value of the last fraction of the exhaled volume). A significant difference in T3/T1 ratio (= the ratio of peripheral versus central air temperature) was found between asthmatic subjects and those with COPD or SSc. In addition, T1max (= temperature in the central), T3max (= peripheral airways) and the T3/T1ratio related to several volumetric measurements (both in absolute values and as percent predicted), such as vital capacity, total lung capacity, forced expiratory volume in 1 s, and diffusion capacity. The temperature ratio of the peripheral versus central airways was lower in patients with COPD or SSc compared to asthmatics, who in turn presented similar levels as the controls. There was also a large overlap between the groups. Overall, the airway temperatures were related to absolute lung volumes, and specifically, the peripheral temperature was related to the gas diffusion capacity (% predicted), suggesting a link to the vascular component.

Exhaled Breath Temperature Measurement in Allergic Respiratory Disease

En los ultimos anos, se ha planteado la hipotesis de que el nivel de temperatura de la respiracion exhalada (EBT) esta relacionado con el grado de inflamacion / remodelacion de las vias respiratorias. El proposito de este estudio fue evaluar la EBT en pacientes con enfermedad respiratoria alergica (asma y / o rinitis alergica) y controles sanos.

Exhaled Nitric Oxide and Exhaled Breath Temperature as Potential Biomarkers in Patients with Pulmonary Hypertension.

Background Pulmonary hypertension (PH) is a progressive fatal disease thus, noninvasive prognostic tools are needed to follow these patients. The aim of our study was to evaluate fractional exhaled nitric oxide (FeNO) and exhaled breath temperature (EBT) values in patients with PH from different causes and to correlate them with respiratory functional data. Methods Twenty-four PH patients underwent spirometry, carbon monoxide diffusion (DLCO) test, transthoracic echocardiography, right-heart catheterization, and FeNO and EBT measurements. Results We studied 3 groups according to the type of PH: 10 patients with pulmonary arterial hypertension (PAH) (group A), 11 patients with PH due to chronic obstructive pulmonary disease (COPD) (group B), and 3 patients with PH associated with left heart disease (group C). Mean FeNO values tend to be higher in group B (15.0 ± 9.3ppb) compared with other groups (respectively, 9.9 ± 5.7 and 8.5 ± 5.2 ppb in groups A and C; p = 0.271) but no statistical significance has been reached. Mean values of alveolar NO concentration (CANO) were higher in groups A and B compared to group C (respectively, 16.9 ± 12.6; 13.9 ± 6.8; and 6.7 ± 2.0 ppb) (p = 0.045). EBT mean values were significantly lower in group C when compared with other groups (group C: 29.0 +- 1.3°C, groups A and B: 30.9 ± 1.3 and 31.2 ± 1.2°C, respectively: p = 0.041). EBT levels were inversely correlated to mean pulmonary artery pressure (PAPm) levels (Spearman coefficient -0.481; p = 0.017). Conclusions eNO, CANO, and EBT have been evaluated in three groups of PH patients. Interestingly EBT reduction was correlated with PAPm increase, whereas FeNO was higher in COPD patients and CANO in PAH and COPD groups. Further studies are needed to clarify EBT, FeNO, and CANO roles as biomarkers in the monitoring of patients with PH.

Exhaled breath temperature in optimally treated asthmatics: severity and underlying mechanisms

Introduction. Increased vascularity may lead to loss of heat in the airways and may modulate exhaled breath temperature (EBT). Increased EBT has been associated with uncontrolled asthma. Aim. We wanted to determine whether the measurement of EBT in optimally treated asthmatic patients is influenced by the increased vascular permeability and whether Vascular endothelial growth factor (VEGF) is implicated in the above process. Furthermore, to assess the impact of asthma severity on EBT values. The diagnostic performance of EBT for the identification of inflammatory profiles in induced sputum was also assessed. Methods. 88 stable asthmatic patients optimally treated for at least 6 months were studied (46 with Severe Refractory Asthma, SRA). EBT was measured with the X-halo device. All patients underwent spirometry, sputum induction for the measurement of % inflammatory cells and for the assessment of both VEGF and albumin in sputum supernatant. The airway vascular permeability index was calculated as the ratio of albumin concentrations in induced sputum and serum. Results. EBT (°C) was significantly higher in patients with SRA compared to those with mild to moderate asthma (median IQR 34.2 [32.4–34.6] versus 31.8 [26.3–34.1], p = 0.001). EBT was significantly associated with VEGF levels in sputum supernatant, while SRA was recognized as a significant co-variate. No other significant associations were observed. Finally, in ROC analysis, the diagnostic performance of EBT for the pure eosinophilic or/and neutrophilic profile did not reach statistical significance. Conclusion. EBT is increasing in severe asthma and is significantly modulated by VEGF levels. Despite the above results its performance for predicting cellular profiles is of limited value.

Clinical implication of exhaled breath temperature measurement in pediatric asthma

Purpose: Exhaled breath temperature (EBT) has been suggested as a noninvasive marker of airway inflammation in asthma. The aim of this study was to determine its clinical implication in children with asthma. Methods: A total of 233 children were enrolled in this study. Among them, 116 were asthmatic children and 117 were healthy chil dren. Spirometry, bronchodilator response (BDR) test, methacholine challenge test, and skin prick test were performed. EBT, frac- tional exhaled nitric oxide (FeNO), blood eosinophils, and total IgE levels were measured. EBT was measured by using X-halo. Results: EBT was significantly higher in the asthma group than in the control group (median [interquartile range], 32.1°C [30.0°C- 33.9°C] vs. 29.7°C [29.0°C-31.3°C], P<0.001). EBT was significantly higher in poorly or partly controlled asthmatic children than well-controlled asthmatic children (33.5°C [31.0°C-34.4°C] vs. 30.3°C [29.3°C-32.9°C], P<0.0001). Among total subjects, EBT was signifi cantly higher in the atopic group than in the nonatopic group (32.4°C [30.3°C-34.0°C] vs. 29.8°C [29.0°C-30.3°C], P<0.001). There were neither significant associations between EBT and BDR (r=0.109, P=0.241) nor between EBT and PC20 (provocation concentra -tion causing a 20% fall in FEV1) in total subjects (r=0.127, P=0.316). EBT did not show any association with FeNO (r=0.353, P=0.071). Conclusion: Our study suggests that EBT might play a role as an ancillary marker for allergic airway inflammation and the degree of control in pediatric asthma patients. Additional studies are required to explore the value of EBT in detail. (Allergy Asthma Respir Dis 2017;5:147-152)

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.

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). To determine the relationships between EBT and asthma treatment decision, current control, pulmonary function, and ENO. 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. 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). 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 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, r2 = 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.

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.

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

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). 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. 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. 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). 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.

Measurement of exhaled breath temperature in science and clinical practice

Educational aims To review the link between inflammation and increased vascularity and blood flow of the airways, and exhaled breath temperature. To position exhaled breath temperature (EBT) as a physiological characteristic differing from core temperature measured at other body sites. To review the existing experience about measuring EBT in different disease states of the respiratory system. To emphasise the influence of airway remodeling/destruction in modulating EBT. Summary Evaluation of the exhaled breath temperature (EBT) has been suggested as a new method to detect and monitor pathological processes in the respiratory system. The putative mechanism of this approach is based upon changes in the blood flow in the conducting airways that are characteristic of different disease states, which influence the temperature of the exhaled gases. The first attempts to prove this concept were made in conjunction with measurement of exhaled nitric oxide fraction ( F eNO ) about a decade ago. They made use of an open-circuit, single-breath method in a closed indoor environment, and demonstrated associations between EBT on the one hand, and bronchial blood flow, F eNO and sputum cellular content on the other. These findings have been further extended to practical applicability with the introduction of multiple-breath, portable hand-held devices. Measurement of EBT using these is less dependent on the ambient environment and easier to perform. Studies have been conducted to explore the relationship between EBT and different physiological characteristics, and to assess possible confounding influences in the process of measurement. The value of the method has been explored in the diagnosis and monitoring of asthma, chronic obstructive pulmonary disease and other respiratory diseases. While initially, emphasis focused on airway inflammation as the primary process to be captured by this method, it was subsequently realised that destructive and other remodelling processes reducing the integral contact surface of the conducting airways and/or damaging their vasculature would also affect the end result by shifting EBT downwards. As obstructive airway disease is, in most cases, a combination of airway inflammation and remodelling/destruction, EBT should be viewed as an individual characteristic indicating fluctuating changes in the balance of these processes. Hence, an important potential application of the method is in monitoring airway diseases. EBT measurement has emerged as an attractive noninvasive new approach in respiratory and, possibly, other diseases. Systematic research will determine its place in clinical practice.

Temperatura do ar exalado, um novo biomarcador no controle da asma: um estudo piloto

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

Exhaled Breath Temperature Increases during Mild Exacerbations in Children with Virus-Induced Asthma

Background: Exhaled breath temperature (EBT) has been suggested as a non-invasive surrogate marker of airway inflammation in asthma. The aim of the study was to evaluate differences in EBT between periods of controlled disease and during exacerbations in children with virus-induced asthma. Methods: Twenty-nine children (aged 6–14 years) with a history of intermittent, virus-induced asthma were included in this case-control study. Cases presented with a common cold and/or mild exacerbation of asthma, while controls were free of asthmatic or common cold symptoms during the previous 6 weeks. A baseline questionnaire was obtained. Atopy assessment, central temperature and a spirometric measurement were recorded. EBT was measured with a new device (Delmedica, Singapore). A nasal wash (for identification of common respiratory viruses) was obtained. Results: Twenty-four children (12 from each group) completed the study. Groups were homogeneous with respect to baseline characteristics. PCR revealed the presence of a virus in 3 out of 17 controls and 10 out of 12 cases (17.6 and 83.3%, respectively, p = 0.002). The most commonly identified virus was rhinovirus (3/3 controls and 7/10 cases, p = 0.02). EBT values were significantly higher for cases (34.91 ± 0.62°C) compared to controls (34.18 ± 1.1°C, p = 0.032). No important differences were observed in the increase rate of EBT (Δe°T) between groups. Conclusions: Changes in airway inflammation during virus-induced asthma exacerbations are reflected in EBT changes. These preliminary data suggest a possible role of EBT measurements in the assessment of airway inflammation in children with virus-induced asthma.

Daily Monitoring of Asthmatics by Means of Individual Devices for Exhaled Breath Temperature Measurement

It has been suggested that inflamed airways may increase the exhaled breath temperature (EBT). We designed a simple instrument for EBT measurement and proven its precision, reproducibility and validity in asthma. Now we tested its utility as individual device to detect changes indicative of the control of asthma. We followed up 14 patients (9 female, age range 29-68 years) with uncontrolled asthma for 3 weeks after stepping up their anti-inflammatory treatment. Subjects were assessed upon inclusion in the study (visit 1, V1), after 1 (V2) and 3 weeks of treatment (V3) by visual-analogue scale (VAS), spirometry, blood and sputum eosinophils (Eos) and EBT. They also kept diaries with symptom scores (SS), peak expiratory flow (PEF) and EBT. Compared with V1, EBT decreased significantly at V2 and V3: from 35, 20°C [ 34 , 36÷35 , 56] (median [25 ÷ 75 interquartile range]) to 34, 70°C [34 , 48 ÷ 34 , 95] and 34,50°C [ 33 , 94 ÷ 34 , 91] respectively, p = 0.017. These changes paralleled the alteration in the other indices of asthma control. The mean weekly EBT and SS significantly decreased between week 1 and week 3 (p = 0.035 and 0.003 respectively), while PEF increased (p = 0.027). In conclusion, EBT is a useful indicator of asthma control to be used by physicians, but also by individual subjects at home.

Development of an Individual Device for Exhaled Breath Temperature Measurement

Different thermometers have been constructed over the decades to measure the temperature of the body to help detect and monitor morbid states. They yield slightly different estimates of the core body temperature depending on the proximity of the measurement site to the internal milieu of the organism, the principle of temperature assessment, and the specific characteristics of the gauging devices. Evaluation of the exhaled breath temperature (EBT) has been recently suggested as a new method to detect inflammatory processes in the conducting airways due to changes in the blood flow perfusion of their walls and adjacent structures. While the first reported EBT experiments required sealed laboratory environment and sophisticated equipment, we designed a simple handheld instrument for EBT measurement and proven its precision, reproducibility and validity in subjects with asthma. We now describe the construction principles of our instrument, the procedure to test the fitness for purpose of the separate units and the novel features of the newest prototypes outfitted with microprocessor and memory. We also outline the potential clinical applications of an individual device for EBT measurement.

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

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. 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. 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. 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.

Performance Characteristics of a New Device for Assessment of Asthmatic Inflammation by Measurement of Exhaled Breath Temperature, the Dunev Thermometer, a Unique Tool for Asthma Management

Performance Characteristics of a New Device for Assessment of Asthmatic Inflammation by Measurement of Exhaled Breath Temperature, the Dunev Thermometer, a Unique Tool for Asthma Management