Indirect assessment of mucosal surface temperatures in the airways: theory and tests

Abstract

We developed and tested a method, based on conduction heat transfer analysis, to infer airway mucosal temperatures from airstream temperature-time profiles during breath-hold maneuvers. The method assumes that radial conduction of heat from the mucosal wall to inspired air dominates heat exchange during a breath-hold maneuver and uses a simplified conservation of energy analysis to extrapolate wall temperatures from air temperature vs. time profiles. Validation studies were performed by simultaneously measuring air and wall temperatures by use of a retractable basket probe in the upper airways of human volunteers and intrathoracic airways of paralyzed intubated dogs during breath holding. In both protocols, a good correlation was demonstrated between directly measured wall temperatures and those calculated from adjacent airstream temperature vs. time profiles during a breath hold. We then calculated intrathoracic bronchial wall temperatures from breath-hold airstream temperature-time profiles recorded in normal human subjects after cold air hyperpnea at 30 and 80 l/min. The calculations show airway wall temperatures in the upper intrathoracic airways that are below core body temperature during hyperpnea of frigid air and upper thoracic airways that are cooler than more peripheral airways. The data suggest that the magnitude of local intrathoracic heat/water flux is not represented by heat/water loss measurements at the airway opening. Both the magnitude and locus of heat transport during cold gas hyperventilation vary with changes in inspired gas temperature and minute ventilation; both may be important determinants of airway responses.

Effects of the ventilation pattern and pulmonary blood flow on lung heat transfer

“…Previous studies of this heat exchange process have focused on measurements of air temperature or indirect estimates of bronchial surface temperature at steadystate conditions (Eschenbacher and Sheppard 1985;Ferrus et al 1980;Ingenito et al 1987;Primiano et al 1988). Several models have been developed to characterize the conditioning of the inspired air by the bronchial tree (Daviscas et al 1990;Eisner 1989;George et al 1990;Hanna and Scherer 1986;Ingenito et al 1986;Ramm et al 1989;Tsu et al 1988).…”

Spatial Variation in the Healthy Human Lung Microbiome and the Adapted Island Model of Lung Biogeography

“…temperature (14), pH (13), and relative deposition of inhaled particles (15). Thus, if the effects of regional growth conditions on bacterial reproduction strongly impact lung microbiome composition, then significant and consistent differences in community membership should be present at spatially separated sites (1) (e.g., the apices should, on average, harbor a distinct microbiome from the lung bases).…”

Host–microorganism interactions in lung diseases

“…The lower respiratory tract is not a uniform tissue, but is comprised of regions with distinct pH, oxygen level and temperature. From an ecological perspective, these regions could be considered as microhabitats that support the colonization of certain bacterial strains over others 81,82 (FIG. 2).…”