Exhaled breath temperature as a marker of airway remodelling in asthma: a preliminary study

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.

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 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 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.

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.

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.

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.

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.

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.

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 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.

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.

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.