A new class of biophysical models for predicting the probability of decompression sickness in scuba diving

2007 ◽  
Vol 103 (2) ◽  
pp. 484-493 ◽  
Author(s):  
Saul Goldman
Keyword(s):  
Decompression Sickness ◽  
Risk Function ◽  
Central Compartment ◽  
The Body ◽  
Inert Gases ◽  
Inert Gas ◽  
Washout Rate ◽  
Peripheral Compartment ◽  
New Class ◽  
Better Than

Interconnected compartmental models have been used for decades in physiology and medicine to account for the observed multi-exponential washout kinetics of a variety of solutes (including inert gases) both from single tissues and from the body as a whole. They are used here as the basis for a new class of biophysical probabilistic decompression models. These models are characterized by a relatively well-perfused, risk-bearing, central compartment and one or two non-risk-bearing, relatively poorly perfused, peripheral compartment(s). The peripheral compartments affect risk indirectly by diffusive exchange of dissolved inert gas with the central compartment. On the basis of the accuracy of their respective predictions beyond the calibration regime, the three-compartment interconnected models were found to be significantly better than the two-compartment interconnected models. The former, on the basis of a number of criteria, was also better than a two-compartment parallel model used for comparative purposes. In these latter comparisons, the models all had the same number of fitted parameters (four), were based on linear kinetics, had the same risk function, and were calibrated against the same dataset. The interconnected models predict that inert gas washout during decompression is relatively fast, initially, but slows rapidly with time compared with the more uniform washout rate predicted by an independent parallel compartment model. If empirically verified, this may have important implications for diving practice.

Decompression outcome following saturation dives with multiple inert gases in rats

1985 ◽  
Vol 59 (5) ◽  
pp. 1503-1514 ◽  
Author(s):  
R. S. Lillo ◽  
E. T. Flynn ◽  
L. D. Homer
Keyword(s):  
Decompression Sickness ◽  
Equation Model ◽  
Hill Equation ◽  
The Body ◽  
Inert Gases ◽  
Inert Gas ◽  
Albino Rats ◽  
Experimental Conditions ◽  
Decompression Stress ◽  
Relative Potencies

This investigation examined the question of whether gas mixtures containing multiple inert gases provide a decompression advantage over mixtures containing a single inert gas. Unanesthetized male albino rats, Rattus norvegicus, were subjected to 2-h simulated dives at depths ranging from 145 to 220 fsw. At pressure, the rats breathed various He-N2-Ar-O2 mixtures (79.1% inert gas-20.9% O2); they were then decompressed rapidly (within 10 s) to surface pressures. The probability of decompression sickness (DCS), measured either as severe bends symptoms or death, was related to the experimental variables in a Hill equation model incorporating parameters that account for differences in the potencies of the three gases and the weight of the animal. The relative potencies of the three gases, which affect the total dose of decompression stress, were determined as significantly different in the following ascending order of potency: He less than N2 less than Ar; some of these differences were small in magnitude. With mixtures, the degree of decompression stress diminished as either N2 or Ar was replaced by He. No obvious advantage or disadvantage of mixtures over the least potent pure inert gas (He) was evident, although limits to the expectation of possible advantage or disadvantage of mixtures were defined. Also, model analysis did not support the hypothesis that the outcome of decompression with multiple inert gases in rats under these experimental conditions can be explained totally by the volume of gas accumulated in the body during a dive.

Inert gas-exchange theory using an electric analogue

1964 ◽  
Vol 19 (6) ◽  
pp. 1193-1198 ◽  
Author(s):  
W. W. Mapleson
Keyword(s):  
Alveolar Ventilation ◽  
The Body ◽  
Exchange Theory ◽  
Inert Gases ◽  
Inert Gas ◽  
Respiratory Pattern ◽  
Whole Body ◽  
High Solubility ◽  
Systematic Analysis ◽  
Inhaled Anesthetics

When an inert gas of moderate or high solubility in blood is inhaled, the rate at which the alveolar concentration rises toward the inspired concentration increases as the inspired concentration is increased. The only previous systematic analysis of whole-body uptake of inert gases to allow for this effect was restricted to a single, artificial, respiratory pattern and the numerical calculations had to be made on a digital computer. This paper develops the theory for a range of respiratory patterns and shows how the computations may be made on a slightly modified form of a simple electric analogue. It is shown that the rate of saturation of the body increases less markedly with inspired concentration if the inspired alveolar ventilation, rather than the expired alveolar ventilation, is kept constant during the saturation process. Conversely, washout is more rapid with a constant inspired ventilation than with a constant expired ventilation. The theory is extended to show how the uptake of one inert gas may substantially affect the uptake of another, administered simultaneously. uptake, distribution and elimination; induction; recovery; drugs; inhaled anesthetics; nitrous oxide; diethyl ether; halothane; computers; ventilation; concentration effect; alveolar ventilation Submitted on February 13, 1964

Effects of physical properties of the breathing gas on decompression-sickness bubbles

1995 ◽  
Vol 79 (5) ◽  
pp. 1828-1836 ◽  
Author(s):  
M. E. Burkard ◽  
H. D. Van Liew
Keyword(s):  
Partition Coefficient ◽  
Physical Properties ◽  
Numerical Simulations ◽  
Bubble Growth ◽  
Decompression Sickness ◽  
Inert Gases ◽  
Inert Gas ◽  
Half Time ◽  
Bubble Density ◽  
Mathematical Relationships

To explore the relative dangers of different inert gases, we developed mathematical relationships concerned with bubble growth, using equations that separate gas properties from other variables. Predictions for saturation exposures were as follows. 1) Peak volume of a bubble is proportional to solubility in tissue when bubble density is high and to the 3/2 power of the ratio of the permeation coefficient to the partition coefficient when density is low. 2) Bubble duration is inversely proportional to the partition coefficient for the inert gas. 3). Sizes and durations of bubbles for one inert gas relative to another depend on whether the tissue is aqueous or lipid but are independent of the magnitude of the decompression and tissue half time. 4). He should give smaller bubbles than N2, except in aqueous tissue with low bubble density; our prediction correlates qualitatively with relative dangers observed with animals but seems to overestimate the safety afforded by He. Numerical simulations illustrate how nonsaturation dives are less predictable because more variables are involved.

VARIATION SIMULATION OF RADON CONCENTRATION IN THE TISSUES AND ORGANS OF THE BODY BY AN ELECTRICAL CIRCUIT

2019 ◽  
Vol 187 (3) ◽  
pp. 390-401
Author(s):  
Milad Pirmoradi ◽  
Ali Negarestani ◽  
Amin Baghizadeh
Keyword(s):  
Cardiac Output ◽  
Human Body ◽  
Absorbed Dose ◽  
Electrical Circuit ◽  
The Body ◽  
Inert Gases ◽  
Inert Gas ◽  
Voltage Source ◽  
Red Marrow ◽  
Inhalation Rate

Abstract In this study, a new model based on electric circuit theory has been introduced to simulate the dynamics of radioactive chemically inert gases in the human body. For this manner, it is assumed that inert gas is transported through the body to various organs via the blood stream. In this simulation, a voltage source is equivalent to gas generation in the atmosphere, the conductivity is equivalent to the cardiac output of the organ, the capacitor capacitance is equivalent to the volume of blood or tissue and voltage across a capacitor is equivalent to the gas concentration in air or blood or a tissue. This simulation can be used to study the dynamics of any inert gas whose partition coefficients are known. We use this simulation to study the dynamics of radon in human body. The physiologically based pharmacokinetic (PBPK) model that describes the fate of radon in systemic tissue has been used for this simulation. Using this simulation, the effective dose equivalent resulting from inhalation of radon has been estimated. The calculated values agree with the previously reported value. Also, using the model, it has been shown that after inhalation of radon gas, absorbed dose has been decreased in different tissues by increasing the inhalation rate without radon. So that, by doubling the inhalation rate and the rate of cardiac output, the value of the absorbed dose has been decreased 11.88% in the adipose tissue, 25.49% in the red marrow tissue and 20.3% in the liver organ.

scholarly journals Dysbarism: An Overview of an Unusual Medical Emergency

Medicina ◽  
2022 ◽  
Vol 58 (1) ◽  
pp. 104
Author(s):  
Gabriele Savioli ◽  
Claudia Alfano ◽  
Christian Zanza ◽  
Gaia Bavestrello Piccini ◽  
Angelica Varesi ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Decompression Sickness ◽  
Clinical Manifestations ◽  
Oxygen Toxicity ◽  
Signs And Symptoms ◽  
General Term ◽  
The Body ◽  
Inert Gas ◽  
Medical Emergency ◽  
Clinical Pictures

Dysbarism is a general term which includes the signs and symptoms that can manifest when the body is subject to an increase or a decrease in the atmospheric pressure which occurs either at a rate or duration exceeding the capacity of the body to adapt safely. In the following review, we take dysbarisms into account for our analysis. Starting from the underlying physical laws, we will deal with the pathologies that can develop in the most frequently affected areas of the body, as the atmospheric pressure varies when acclimatization fails. Manifestations of dysbarism range from itching and minor pain to neurological symptoms, cardiac collapse, and death. Overall, four clinical pictures can occur: decompression illness, barotrauma, inert gas narcosis, and oxygen toxicity. We will then review the clinical manifestations and illustrate some hints of therapy. We will first introduce the two forms of decompression sickness. In the next part, we will review the barotrauma, compression, and decompression. The last three parts will be dedicated to gas embolism, inert gas narcosis, and oxygen toxicity. Such an approach is critical for the effective treatment of patients in a hostile environment, or treatment in the emergency room after exposure to extreme physical or environmental factors.

Influence of blood flow on cutaneous permeability to inert gas

1984 ◽  
Vol 57 (4) ◽  
pp. 1167-1172 ◽  
Author(s):  
Y. C. Lin ◽  
N. Kakitsuba ◽  
D. K. Watanabe ◽  
G. W. Mack
Keyword(s):  
Blood Flow ◽  
Ambient Temperature ◽  
Gas Diffusion ◽  
The Body ◽  
Inert Gases ◽  
Inert Gas ◽  
Human Hand ◽  
Cutaneous Blood Flow ◽  
Diffusion Distance ◽  
Cutaneous Blood

A thermally regulated Plexiglas chamber was designed for investigation of transcutaneous diffusion of N2 and helium (He) in the human hand. Influence of cutaneous blood flow in this process was studied simultaneously with gas diffusion measurements. Changes in cutaneous blood flow (Q, in ml X min-1 X 100 ml tissue-1) were effected by altering ambient temperature (T) from 20 to 40 degrees C (Q = 0.08 X 100.07T). We found that the rate of inert gas diffusion through human skin, expressed as conductance (G, in ml STPD X h-1 X m-2 X atm-1), increases exponentially as a function of blood flow, and was indistinguishable between He and N2 (G = 21.19 X 100.0124Q). The permeability, diffusion coefficient per unit diffusion distance (D/h, in cm/h), also rose exponentially as a function of blood flow. But permeability for He (D/h = 0.1748 X 100.0203Q) was greater than that for N2 (D/h = 0.1678 X 100.0114Q). As cutaneous blood flow rises, because of increased temperature, the apparent diffusion distance falls linearly for both N2 and He. The change is more prominent for He than for N2 diffusion. Estimated replacement time for the body stores of N2 by transcutaneous diffusion alone was shortened from 26.8 h at 31 degrees C to 15.1 h at 37 degrees C. It is suggested from this study that beneficial results may be derived during decompression procedure 1) by maintaining an appropriate transcutaneous pressure gradient of inert gases, and 2) by elevating ambient temperature.

scholarly journals An analytics-based heuristic decomposition of a bilevel multiple-follower cutting stock problem

OR Spectrum ◽  
2021 ◽  
Author(s):  
Adejuyigbe O. Fajemisin ◽  
Laura Climent ◽  
Steven D. Prestwich
Keyword(s):  
Real Life ◽  
Forest Harvesting ◽  
Cutting Stock Problem ◽  
Cutting Stock ◽  
Decomposition Approach ◽  
New Class ◽  
Bilevel Problem ◽  
Programming Techniques ◽  
Bilevel Problems ◽  
Better Than

AbstractThis paper presents a new class of multiple-follower bilevel problems and a heuristic approach to solving them. In this new class of problems, the followers may be nonlinear, do not share constraints or variables, and are at most weakly constrained. This allows the leader variables to be partitioned among the followers. We show that current approaches for solving multiple-follower problems are unsuitable for our new class of problems and instead we propose a novel analytics-based heuristic decomposition approach. This approach uses Monte Carlo simulation and k-medoids clustering to reduce the bilevel problem to a single level, which can then be solved using integer programming techniques. The examples presented show that our approach produces better solutions and scales up better than the other approaches in the literature. Furthermore, for large problems, we combine our approach with the use of self-organising maps in place of k-medoids clustering, which significantly reduces the clustering times. Finally, we apply our approach to a real-life cutting stock problem. Here a forest harvesting problem is reformulated as a multiple-follower bilevel problem and solved using our approach.

scholarly journals Decompression sickness risk in rats by microbial removal of dissolved gas

1998 ◽  
Vol 275 (3) ◽  
pp. R677-R682 ◽  
Author(s):  
Susan R. Kayar ◽  
Terry L. Miller ◽  
Meyer J. Wolin ◽  
Eugenia O. Aukhert ◽  
Milton J. Axley ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
High Pressures ◽  
Decompression Sickness ◽  
Body Burden ◽  
The Body ◽  
Dissolved Gas ◽  
Hyperbaric Chamber ◽  
Methanobrevibacter Smithii ◽  
Water Rate ◽  
Microbial Removal

We present a method for reducing the risk of decompression sickness (DCS) in rats exposed to high pressures of H2. Suspensions of the human colonic microbe Methanobrevibacter smithii were introduced via a colonic cannula into the large intestines of the rats. While the rats breathed H2in a hyperbaric chamber, the microbe metabolized some of the H2diffusing into the intestine, converting H2and CO2to methane and water. Rate of release of methane from the rats, which was monitored by gas chromatography, varied with chamber H2pressure. This rate was higher during decompression than during compression, suggesting that during decompression the microbe was metabolizing H2stored in the rats’ tissues. Rats treated with M. smithii had a 25% (5 of 20) incidence of DCS, which was significantly lower ( P < 0.01) than the 56% (28 of 50) incidence of untreated controls, brought on by a standardized compression and decompression sequence. Thus using a microbe in the intestine to remove an estimated 5% of the body burden of H2reduced DCS risk by more than one-half. This method of biochemical decompression may potentially facilitate human diving.

scholarly journals “ALL IN ONE OR (W)HOLE IN ONE REPAIR” for Adult Total Brachial Plexus Palsy

2021 ◽  
Author(s):  
V. Purushothaman ◽  
K. Vinoth Kumar ◽  
Sabari Girish Ambat ◽  
R. Venkataswami
Keyword(s):  
Brachial Plexus ◽  
Hand Function ◽  
The Body ◽  
Salvage Procedure ◽  
Brachial Plexus Palsy ◽  
Nerve Reconstruction ◽  
Muscle Transfer ◽  
Young Males ◽  
Elbow Function ◽  
Better Than

Abstract Background Total brachial plexus palsy (TBPP) accounts for nearly 50% of all brachial plexus injuries. Since achieving a good functional hand was almost impossible, the aim was settled to get a good shoulder and elbow function. It was Gu, who popularized the concept of utilizing contralateral C7 (CC7) with vascularized ulnar nerve graft (VUNG) to get some hand function. We have modified it to suit our patients by conducting it as a single-stage procedure, thereby trying to get a functional upper limb. Methods From 2009 to 2014, we had 20 TBPP patients. We feel nerve reconstruction is always better than any other salvage procedure, including free muscle transfer. We modified Gu's concept and present our concept of total nerve reconstruction as “ALL IN ONE OR (W)HOLE IN ONE REPAIR.” Results All patients able to move their reconstructed limbs independently or with the help of contralateral limbs. Three patients developed hook grip and one patient was able to incorporate limbs to do bimanual jobs. One important observation is that all the reconstructed limbs regain the bulk, and to a certain extent, the attitude and appearance looks normal, as patients no longer hide it or hang it in a sling. Conclusion Adult brachial plexus injury itself is a devastating injury affecting young males. By doing this procedure, the affected limb is not dissociated from the rest of the body and rehabilitation can be aimed to get a supportive limb.

scholarly journals Epigenetic Regulation of Cannabinoid-Mediated Attenuation of Inflammation and Its Impact on the Use of Cannabinoids to Treat Autoimmune Diseases

2021 ◽  
Vol 22 (14) ◽  
pp. 7302
Author(s):  
Bryan Latrell Holloman ◽  
Mitzi Nagarkatti ◽  
Prakash Nagarkatti
Keyword(s):  
Autoimmune Diseases ◽  
Chronic Inflammation ◽  
Cannabinoid Receptors ◽  
T Regulatory Cells ◽  
Neurological Diseases ◽  
Suppressor Cells ◽  
The Body ◽  
New Class ◽  
Wide Range ◽  
Clinical Disorders

Chronic inflammation is considered to be a silent killer because it is the underlying cause of a wide range of clinical disorders, from cardiovascular to neurological diseases, and from cancer to obesity. In addition, there are over 80 different types of debilitating autoimmune diseases for which there are no cure. Currently, the drugs that are available to suppress chronic inflammation are either ineffective or overtly suppress the inflammation, thereby causing increased susceptibility to infections and cancer. Thus, the development of a new class of drugs that can suppress chronic inflammation is imperative. Cannabinoids are a group of compounds produced in the body (endocannabinoids) or found in cannabis (phytocannabinoids) that act through cannabinoid receptors and various other receptors expressed widely in the brain and immune system. In the last decade, cannabinoids have been well established experimentally to mediate anti-inflammatory properties. Research has shown that they suppress inflammation through multiple pathways, including apoptosis and inducing immunosuppressive T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Interestingly, cannabinoids also mediate epigenetic alterations in genes that regulate inflammation. In the current review, we highlight how the epigenetic modulations caused by cannabinoids lead to the suppression of inflammation and help identify novel pathways that can be used to target autoimmune diseases.

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