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.

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.

Effect of oxygen breathing and perfluorocarbon emulsion treatment on air bubbles in adipose tissue during decompression sickness

2009 ◽  
Vol 107 (6) ◽  
pp. 1857-1863 ◽  
Author(s):  
T. Randsoe ◽  
O. Hyldegaard
Keyword(s):  
Adipose Tissue ◽  
Bubble Growth ◽  
Decompression Sickness ◽  
Combined Effect ◽  
Inert Gases ◽  
Air Bubbles ◽  
Transport Capacity ◽  
Normobaric Oxygen ◽  
Oxygen Breathing ◽  
Effect Of Oxygen

Decompression sickness (DCS) after air diving has been treated with success by means of combined normobaric oxygen breathing and intravascular perfluorocarbon (PFC) emulsions causing increased survival rate and faster bubble clearance from the intravascular compartment. The beneficial PFC effect has been explained by the increased transport capacity of oxygen and inert gases in blood. However, previous reports have shown that extravascular bubbles in lipid tissue of rats suffering from DCS will initially grow during oxygen breathing at normobaric conditions. We hypothesize that the combined effect of normobaric oxygen breathing and intravascular PFC infusion could lead to either enhanced extravascular bubble growth on decompression due to the increased oxygen supply, or that PFC infusion could lead to faster bubble elimination due to the increased solubility and transport capacity in blood for nitrogen causing faster nitrogen tissue desaturation. In anesthetized rats decompressed from a 60-min hyperbaric exposure breathing air at 385 kPa, we visually followed the resolution of micro-air bubbles injected into abdominal adipose tissue while the rats breathed either air, oxygen, or oxygen breathing combined with PFC infusion. All bubble observations were done at 101.3 kPa pressure. During oxygen breathing with or without combined PFC infusion, bubbles disappeared faster compared with air breathing. Combined oxygen breathing and PFC infusion caused faster bubble disappearance compared with oxygen breathing. The combined effect of oxygen breathing and PFC infusion neither prevented nor increased transient bubble growth time, rate, or growth ratio compared with oxygen breathing alone. We conclude that oxygen breathing in combination with PFC infusion causes faster bubble disappearance and does not exacerbate transient bubble growth. PFC infusion may be a valuable adjunct therapy during the first-aid treatment of DCS at normobaric conditions.

Numerical Simulations of Electric Field Driven Self-Assembly of Monolayers of Mixtures of Nanoparticles

2017 ◽  
Author(s):  
E. Amah ◽  
N. Musunuri ◽  
Ian S. Fischer ◽  
Pushpendra Singh
Keyword(s):  
Electric Field ◽  
Physical Properties ◽  
Numerical Simulations ◽  
Self Assembly ◽  
Composite Particle ◽  
Critical Value ◽  
Direct Numerical Simulations ◽  
Composite Particles ◽  
Liquid Interfaces ◽  
Induced Dipole

We numerically study the process of self-assembly of particle mixtures on fluid-liquid interfaces when an electric field is applied in the direction normal to the interface. The force law for the dependence of the electric field induced dipole-dipole and capillary forces on the distance between the particles and their physical properties obtained in an earlier study by performing direct numerical simulations is used for conducting simulations. The inter-particle forces cause mixtures of nanoparticles to self-assemble into molecular-like hierarchical arrangements consisting of composite particles which are organized in a pattern. However, there is a critical electric intensity value below which particles move under the influence of Brownian forces and do not self-assemble. Above the critical value, when the particles sizes differed by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles forming a ring around it. Approximately same sized particles, when their concentrations are approximately equal, form binary particles or chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate, but when their concentrations differ the particles whose concentration is larger form rings around the particles with smaller concentration.

Role of oxygen in the production of human decompression sickness

1987 ◽  
Vol 63 (6) ◽  
pp. 2380-2387 ◽  
Author(s):  
P. K. Weathersby ◽  
B. L. Hart ◽  
E. T. Flynn ◽  
W. F. Walker
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Decompression Sickness ◽  
Animal Experiments ◽  
Inert Gases ◽  
Relative Risks ◽  
Data Variability ◽  
Increase Risk ◽  
High O2

In the calculation of decompression schedules, it is commonly assumed that only the inert gas needs to be considered; all inspired O2 is ignored. Animal experiments have shown that high O2 can increase risk of serious decompression sickness (DCS). A trial was performed to assess the relative risks of O2 and N2 in human no-decompression dives. Controlled dives (477) of 30- to 240-min duration were performed with subjects breathing mixtures with low (0.21–0.38 ATA) or high (1.0–1.5 ATA) Po2. Depths were chosen by a sequential dose-response format. Only 11 cases of DCS and 18 cases of marginal symptoms were recorded despite exceeding the presently accepted no-decompression limits by greater than 20%. Analysis by maximum likelihood showed a shallow dose-response curve for increasing depth. O2 was estimated to have zero influence on DCS risk, although data variability still allows a slight chance that O2 could be 40% as effective as N2 in producing a risk of DCS. Consideration of only inert gases is thus justified in calculating human decompression tables.

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

scholarly journals Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3396
Author(s):  
Luboš Běhálek ◽  
Jan Novák ◽  
Pavel Brdlík ◽  
Martin Borůvka ◽  
Jiří Habr ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
Structural Changes ◽  
The Other ◽  
Half Time ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Melt Crystallisation ◽  
Kinetics Of ◽  
Crystallisation Rate

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

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