Increased exhaled breath temperature in subjects with uncontrolled asthma

Wireless, battery-free, multifunctional integrated bioelectronics for respiratory pathogens monitoring and severity evaluation

The rapid diagnosis of respiratory virus infection through breath and blow remains challenging. Here we develop a wireless, battery-free, multifunctional pathogenic infection diagnosis system (PIDS) for diagnosing SARS-CoV-2 infection and symptom severity by blow and breath within 110 s and 350 s, respectively. The accuracies reach to 100% and 92% for evaluating the infection and symptom severity of 42 participants, respectively. PIDS realizes simultaneous gaseous sample collection, biomarker identification, abnormal physical signs recording and machine learning analysis. We transform PIDS into other miniaturized wearable or portable electronic platforms that may widen the diagnostic modes at home, outdoors and public places. Collectively, we demonstrate a general-purpose technology for rapidly diagnosing respiratory pathogenic infection by breath and blow, alleviating the technical bottleneck of saliva and nasopharyngeal secretions. PIDS may serve as a complementary diagnostic tool for other point-of-care techniques and guide the symptomatic treatment of viral infections.

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.

Requirements for Supporting Diagnostic Equipment of Respiration Process in Humans

There is abundant worldwide research conducted on the subject of the methods of human respiration process examination. However, many of these studies describe methods and present the results while often lacking insight into the hardware and software aspects of the devices used during the research. This paper’s goal is to present new equipment for assessing the parameters of human respiration, which can be easily adopted for daily diagnosis. This work deals with the issue of developing the correct method of obtaining measurement data. The requirements of the acquisition parameters are clearly pointed out and examples of the medical applications of the described device are shown. Statistical analysis of acquired signals proving its usability is also presented. In the examples of selected diseases of the Upper Respiratory Tract (URT), the advantages of the developed apparatus for supporting the diagnosis of URT patency have been proven.

Airflow dynamics and exhaled-breath temperature following cold-water ingestion

INTRODUCTION

Drinking cold water evokes decreases in spirometric indices of lung function. We studied whether this could be explained by changes in exhaled-breath temperature (EBT), airflow dynamics, and spirometer measurement sensitivity.

METHODS

In a randomized/crossover design, 10 healthy adults consumed 1000 mL refrigerated water (2.1 ± 0.64 °C) or water at room temperature (19.4 ± 0.5 °C), with EBT assessed at baseline and at 5, 10, 15 and 30-min post-ingestion. The influence of EBT on pneumotachograph measurement characteristics was modelled using computational fluid dynamics (CFD).

RESULTS

At 5-min post-ingestion, EBT was lower (p < 0.001) following the ingestion of cold water versus water at room-temperature (31.7 ± 1.1 vs. 33.0 ± 0.9 °C), and remained lower until 30-min post-ingestion. At a flow of 8 L s^-1, a decrease in EBT of 2.1 °C (as observed following cold-water ingestion) was modelled to underpredict lung volume by 0.7%.

CONCLUSIONS

Cold water reduces EBT below baseline but effects pneumotachograph measurements only negligibly. Therefore, decreased lung function following cold-water ingestion likely has a physiological explanation which warrants further study.

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

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.

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 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.

The current and future role of biomarkers in type 2 cytokine-mediated asthma management

Assessment and management of asthma is complicated by the heterogeneous pathophysiological mechanisms that underlie its clinical presentation, which are not necessarily reflected in standardized management paradigms and which necessitate an individualized approach to treatment. This is particularly important with the emerging availability of a variety of targeted forms of therapy that may only be appropriate for use in particular patient subgroups. The identification of biomarkers can potentially aid diagnosis and inform prognosis, help guide treatment decisions and allow clinicians to predict and monitor response to treatment. Biomarkers for asthma have been identified from a variety of sources, including airway, exhaled breath and blood. Biomarkers from exhaled breath include fractional exhaled nitric oxide, measurement of which can help identify patients most likely to benefit from inhaled corticosteroids and targeted anti-immunoglobulin E therapy. Biomarkers measured in blood are relatively non-invasive and technically more straightforward than those measured from exhaled breath or directly from the airway. The most well established of these are the blood eosinophil count and serum periostin, both of which have demonstrated utility in identifying patients most likely to benefit from targeted anti-interleukin and anti-immunoglobulin E therapies, and in monitoring subsequent treatment response. For example, serum periostin appears to be a biomarker for responsiveness to inhaled corticosteroid therapy and may help identify patients as suitable candidates for anti-IL-13 treatment. The use of biomarkers can therefore potentially help avoid unnecessary morbidity from high-dose corticosteroid therapy and allow the most appropriate and cost-effective use of targeted therapies. Ongoing clinical trials are helping to further elucidate the role of established biomarkers in routine clinical practice, and a range of other circulating novel potential biomarkers are currently being investigated in the research setting.

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.

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.

Novel biomarkers for asthma stratification and personalized therapy

A stepwise pharmacological treatment is currently recommended for all asthma patients and is personalized mainly on disease severity, aiming for the lowest disease-controlling step. Nevertheless, asthma comprises several related pathologies with similar clinical manifestations resulting from distinct underlying mechanisms. Therefore novel biomarkers could lead to asthma stratification and thus improve upon the current stepwise approach. The aim of this review is to update the reader with regard to different assays proposed in the recent asthma literature for measuring potential biomarkers for patient stratification and treatment personalization. Promising biomarkers are sputum eosinophils, serum periostin and exhaled nitric oxide. Periostin could differentiate between Th2-high and Th2-low asthma (Th2-high patients are more responsive to glucocorticoids) and the less-defined asthma types which often present a therapeutic challenge. Several other biomarkers, mainly cytokines, leukotrienes and exhaled air components, can be quantified in body fluids and exhaled breath and could also be useful for asthma stratification.

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.