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

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: ͑1͒ ethanol expirograms and ͑2͒ the uptake of seven soluble gases. Then, the model simulated the excretion of ten soluble gases whose blood:air partition coefficient ( b:a ), a measure of blood solubility, ranged over 5 orders of magnitude. We found that gases with b:a Ͻ10 exchange almost solely in the alveoli and gases with b:a Ͼ100 exchange almost exclusively in the airways. Gases with 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 b:a Ͼ10

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

Effect of sedation with detomidine and butorphanol on pulmonary gas exchange in the horse

<p>Abstract</p> <p>Background</p> <p>Sedation with α₂-agonists in the horse is reported to be accompanied by impairment of arterial oxygenation. The present study was undertaken to investigate pulmonary gas exchange using the Multiple Inert Gas Elimination Technique (MIGET), during sedation with the α₂-agonist detomidine alone and in combination with the opioid butorphanol.</p> <p>Methods</p> <p>Seven Standardbred trotter horses aged 3–7 years and weighing 380–520 kg, were studied. The protocol consisted of three consecutive measurements; in the unsedated horse, after intravenous administration of detomidine (0.02 mg/kg) and after subsequent butorphanol administration (0.025 mg/kg). Pulmonary function and haemodynamic effects were investigated. The distribution of ventilation-perfusion ratios (V_A/Q) was estimated with MIGET.</p> <p>Results</p> <p>During detomidine sedation, arterial oxygen tension (PaO₂) decreased (12.8 ± 0.7 to 10.8 ± 1.2 kPa) and arterial carbon dioxide tension (PaCO₂) increased (5.9 ± 0.3 to 6.1 ± 0.2 kPa) compared to measurements in the unsedated horse. Mismatch between ventilation and perfusion in the lungs was evident, but no increase in intrapulmonary shunt could be detected. Respiratory rate and minute ventilation did not change. Heart rate and cardiac output decreased, while pulmonary and systemic blood pressure and vascular resistance increased. Addition of butorphanol resulted in a significant decrease in ventilation and increase in PaCO₂. Alveolar-arterial oxygen content difference P(A-a)O₂remained impaired after butorphanol administration, the V_A/Q distribution improved as the decreased ventilation and persistent low blood flow was well matched. Also after subsequent butorphanol no increase in intrapulmonary shunt was evident.</p> <p>Conclusion</p> <p>The results of the present study suggest that both pulmonary and cardiovascular factors contribute to the impaired pulmonary gas exchange during detomidine and butorphanol sedation in the horse.</p

Twelve-month psychosis-predictive value of the ultra-high risk criteria in children and adolescents

Objective The validity of current ultra-high risk (UHR) criteria is under-examined in help-seeking minors, particularly, in children below the age of 12 years. Thus, the present study investigated predictors of one-year outcome in children and adolescents (CAD) with UHR status. Method Thirty-five children and adolescents (age 9–17 years) meeting UHR criteria according to the Structured Interview for Psychosis-Risk Syndromes were followed-up for 12 months. Regression analyses were employed to detect baseline predictors of conversion to psychosis and of outcome of non-converters (remission and persistence of UHR versus conversion). Results At one-year follow-up, 20% of patients had developed schizophrenia, 25.7% had remitted from their UHR status that, consequently, had persisted in 54.3%. No patient had fully remitted from mental disorders, even if UHR status was not maintained. Conversion was best predicted by any transient psychotic symptom and a disorganized communication score. No prediction model for outcome beyond conversion was identified. Conclusions Our findings provide the first evidence for the predictive utility of UHR criteria in CAD in terms of brief intermittent psychotic symptoms (BIPS) when accompanied by signs of cognitive impairment, i.e. disorganized communication. However, because attenuated psychotic symptoms (APS) related to thought content and perception were indicative of non-conversion at 1-year follow-up, their use in early detection of psychosis in CAD needs further study. Overall, the need for more in-depth studies into developmental peculiarities in the early detection and treatment of psychoses with an onset of illness in childhood and early adolescence was further highlighted

Venous Air Embolism during Surgery, Especially Cesarean Delivery

Venous air embolism (VAE) is the entrapment of air or medical gases into the venous system causing symptoms and signs of pulmonary vessel obstruction. The incidence of VAE during cesarean delivery ranges from 10 to 97% depending on surgical position or diagnostic tools, with a potential for life-threatening events. We reviewed extensive literatures regarding VAE in detail and herein described VAE during surgery including cesarean delivery from background and history to treatment and prevention. It is intended that present work will improve the understanding of VAE during surgery