Airway exchange of highly soluble gases

Hlastala MP, Powell FL, Anderson JC. Airway exchange of highly soluble gases. J Appl Physiol 114: [675][676][677][678][679][680] 2013. First published January 10, 2013; doi:10.1152/japplphysiol.01291.2012.-Highly blood soluble gases exchange with the bronchial circulation in the airways. On inhalation, air absorbs highly soluble gases from the airway mucosa and equilibrates with the blood before reaching the alveoli. Highly soluble gas partial pressure is identical throughout all alveoli. At the end of exhalation the partial pressure of a highly soluble gas decreases from the alveolar level in the terminal bronchioles to the end-exhaled partial pressure at the mouth. A mathematical model simulated the airway exchange of four gases (methyl isobutyl ketone, acetone, ethanol, and propylene glycol monomethyl ether) that have high water and blood solubility. The impact of solubility on the relative distribution of airway exchange was studied. We conclude that an increase in water solubility shifts the distribution of gas exchange toward the mouth. Of the four gases studied, ethanol had the greatest decrease in partial pressure from the alveolus to the mouth at end exhalation. Single exhalation breath tests are inappropriate for estimating alveolar levels of highly soluble gases, particularly for ethanol. gas exchange; bronchial circulation; alcohol; diffusion; high blood soluble gases; high water soluble gases IT IS GENERALLY ACCEPTED that the exchange of respiratory gases between the blood and the air in the lungs occurs in the alveoli of the lungs. The relevant gas exchange features of lung anatomy are the very large surface area (ϳ70 m 2 ) and the thin diffusion barrier (ϳ0.10 m) between the blood and alveolar gas. However, the lungs have two circulations: bronchial (bringing nutrients to the airway tissue) and pulmonary (bringing deoxygenated blood to the alveolus for oxygenation and elimination of carbon dioxide). This paper addresses the role of the bronchial circulation in the exchange of highly soluble gases by the lungs. Interest in highly soluble gas interaction with the airways first developed around the events of World War II (11). Further development has continued since that time Pulmonary airways are perfused by the bronchial circulation (13). Gas exchange between the respired air and the bronchial circulation was recognized by Wanner et al. Several studies have used mathematical modeling to demonstrate that highly soluble gases exchange within the lung airways (7, 10, 18, 20, 22, 29 -31, 38 -40, 46). Airway exchange models have been developed to study the uptake of soluble inhaled toxic gases as well as the elimination properties of soluble inert gases. The models are based on physicochemical principles of gases and show the feasibility of airway exchange of highly soluble gases. Fick's Law quantifies diffusion across both the airway and alveolar gas exchange barriers. The amount that diffuses across a barrier is directly related to the product of the solubility of the gas in the barrier and the diffusivity of that gas in the barrier. In the case of alveolar gas exchange with the pulmonary circulation, the alveolocapillary membrane is ϳ0.10 m thick. We have been unable to find any publications with measurements of the diffusion distance between airway lumen and bronchial vasculature in humans. For sheep, an animal of similar size to the human, the diffusion distance varies based on axial position from ϳ50 m to 130 m (4). In addition to the thick tissue barrier, a thin (Յ10 m) mucus layer composed predominantly of water is interposed between the tissue and lumen. Because of this liquid layer's intimate contact with air, the exchange across the airway wall is primarily governed by the solubility of a gas in water ( w:a : water to air partition coefficient). In most cases, gases with high b:a also have a high w:a . However, some gases with high b:a are not as soluble in water and have a relatively low w:a (5), presumably because solubility in lipids and other biological substances ma

An evidence map of psychosocial interventions for the earliest stages of bipolar disorder.

Depression, schizophrenia, and bipolar disorder are three of the four most burdensome problems in people aged under 25 years. In psychosis and depression, psychological interventions are effective, low-risk, and high-benefit approaches for patients at high risk of first-episode or early-onset disorders. We review the use of psychological interventions for early-stage bipolar disorder in patients aged 15-25 years. Because previous systematic reviews had struggled to identify information about this emerging sphere of research, we used evidence mapping to help us identify the extent, distribution, and methodological quality of evidence because the gold standard approaches were only slightly informative or appropriate. This strategy identified 29 studies in three target groups: ten studies in populations at high risk for bipolar disorder, five studies in patients with a first episode, and 14 studies in patients with early-onset bipolar disorder. Of the 20 completed studies, eight studies were randomised trials, but only two had sample sizes of more than 100 individuals. The main interventions used were family, cognitive behavioural, and interpersonal therapies. Only behavioural family therapies were tested across all of our three target groups. Although the available interventions were well adapted to the level of maturity and social environment of young people, few interventions target specific developmental psychological or physiological processes (eg, ruminative response style or delayed sleep phase), or offer detailed strategies for the management of substance use or physical health

The role of mathematical modeling in VOC analysis using isoprene as a prototypic example

Isoprene is one of the most abundant endogenous volatile organic compounds (VOCs) contained in human breath and is considered to be a potentially useful biomarker for diagnostic and monitoring purposes. However, neither the exact biochemical origin of isoprene nor its physiological role are understood in sufficient depth, thus hindering the validation of breath isoprene tests in clinical routine. Exhaled isoprene concentrations are reported to change under different clinical and physiological conditions, especially in response to enhanced cardiovascular and respiratory activity. Investigating isoprene exhalation kinetics under dynamical exercise helps to gather the relevant experimental information for understanding the gas exchange phenomena associated with this important VOC. A first model for isoprene in exhaled breath has been developed by our research group. In the present paper, we aim at giving a concise overview of this model and describe its role in providing supportive evidence for a peripheral (extrahepatic) source of isoprene. In this sense, the results presented here may enable a new perspective on the biochemical processes governing isoprene formation in the human body.Comment: 17 page