The added value of exhaled breath temperature in respiratory medicine

Abstract

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.

Tracking tidal volume noninvasively in volunteers using a tightly controlled temperature‐based device: A proof of concept paper

“…The notion that a temperature-based instrument could track indices of respiration is not novel, [21][22][23] but previous attempts to develop such an instrument failed for several reasons. First, rapidly responding, inexpensive thermistors integrated into a thermal balance electronic circuit were not exploited in the past, thus limiting the ability of investigators to detect minute changes in temperature during the respiratory cycle.…”

Dynamics of exhaled breath temperature after smoking a cigarette and its association with lung function changes predictive of COPD risk in smokers: a cross-sectional study

“…We measured multiple expirations, with the device signalling the end of measurement when EBT reached thermal equilibrium. Details about the measurement have been described elsewhere (3). In short, patients inhaled through the nose and exhaled into the device in a tidal breathing pattern through the mouth.…”

“…One of the methods showing potential in that respect is exhaled breath temperature (EBT) measurement. It has recently been introduced as a new, non-invasive marker of inflammation of the respiratory tract in patients with respiratory diseases (asthma, COPD, cystic fibrosis, bronchial carcinoma), as it was consistently and significantly higher than in healthy controls (3,4). As a biomarker of inflammation and vascularity of the airways it can be used alone or in combination with other inflammatory biomarkers like leukocyte and eosinophil counts, exhaled nitric oxide (FeNO), C-reactive protein, and club cell secretory protein (3,4).…”

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

“…An increase in measured exhaled breath temperature (EBT) has been hypothesized to reflect the extra heat that is produced from the underlying airway inflammation in asthma . Therefore, EBT measurements have been suggested as a non‐invasive method of detecting and monitoring airway inflammation . However, no investigations monitoring the longitudinal changes in EBT that occur relative to the asthma status have been performed to date.…”

“…6 Therefore, EBT measurements have been suggested as a non-invasive method of detecting and monitoring airway inflammation. [7][8][9] However, no investigations monitoring the longitudinal changes in EBT that occur relative to the asthma status have been performed to date.…”