Modeling Soluble Gas Exchange in the Airways and Alveoli

Abstract

A mathematical model of heat, water and soluble gas exchange in the airways and alveoli was used to predict the location of soluble gas exchange in the lung. A previously published model of heat, water and soluble gas exchange in the airways was improved by incorporating anatomical data on the airway wall to better describe the bronchial circulation and expanding the model to include a time varying description of soluble gas concentration in the alveoli. Next, the model was validated using two experimental data sets from the literature: (1) ethanol expirograms and (2) the uptake of seven soluble gases. Then, the model simulated the excretion of ten soluble gases whose blood:air partition coefficient (lambda(b:a)), a measure of blood solubility, ranged over 5 orders of magnitude. We found that gases with lambda(b:a) < 10 exchange almost solely in the alveoli and gases with lambda(b:a) > 100 exchange almost exclusively in the airways. Gases with lambda(b:a) between 10 and 100 have significant interaction with the airways and alveoli. These results suggest that the airways play a larger role in pulmonary gas exchange than previously assumed and may require a reevaluation of pulmonary tests that involve exhaled samples of gases with lambda(b:a) > 10.

Background levels and diurnal variations of hydrogen cyanide in breath and emitted from skin

“…It cannot be excluded that HCN is to some extent filtered in the nasal mucosa. In general, since hydrogen cyanide is a hydrophilic species (water air partition coefficient of 320), the gas exchange might take place not only at the alveolar interface but also in the mucosa of the lungs and airways [36]. Hence, one cannot expect a simple correlation between end-tidal breath, alveolar breath and blood HCN levels.…”

The Impact of Breathing Pattern and Lung Size on the Alcohol Breath Test

“…It has recently been shown that EEAC is less than AAC due to the exchange of alcohol in the airways during both inspiration and expiration. 2,3,8 Earlier studies have examined the assumption of equality between end-exhaled and AAC by comparing ABT values with blood measurements and found a considerable amount of variation in the ratio of EEAC to BAC. For further evidence regarding the lack of end-exhaled and alveolar equality, two studies 10,13 have shown that EEAC is approximately 15-20% lower than AAC on average (obtained using isothermal rebreathing).…”

Physiological Modeling for Analysis of Exhaled Breath

“…Hydrophilic compounds such as acetone have been demonstrated to interact with the water-like mucus membrane lining the conductive airways, an effect which has become known as wash-in/washout behavior. Extensive details can be found, e.g., in [54,55,7,8].…”