Intrapulmonary distribution of alveolar gas exchange during breath-hold diving in humans

1995 ◽  
Vol 78 (2) ◽  
pp. 410-416 ◽  
Author(s):  
M. H. Liner ◽  
D. Linnarsson
Keyword(s):  
Atmospheric Pressure ◽  
Impedance Cardiography ◽  
Ambient Pressure ◽  
Co2 Exchange ◽  
Phase Iii ◽  
Breath Hold ◽  
Pulmonary Perfusion ◽  
Normal Atmospheric Pressure ◽  
Wet Surface ◽  
Alveolar Gas Exchange

Expirograms for CO2 and O2 obtained immediately after 75-s breath holds (BHs) in thermoneutral conditions were studied in 10 subjects. BHs were performed at normal atmospheric pressure in dry condition (dry surface BH), at normal atmospheric pressure submerged (wet surface BH), and during a transient increase of ambient pressure to 3 atmospheres absolute submerged (wet BH dive). Cardiac index was estimated by means of impedance cardiography. Phase III (alveolar plateau) slopes for CO2 expirograms were lowest after wet surface BH. The greater slope observed after dry surface BH was attributed mainly to intrapulmonary perfusion heterogeneity and the greater slope seen after wet BH dive to continuing alveolar CO2 exchange during expiration. Cardiogenic oscillations in phase III (evaluated by spectral analysis) were largest after dry surface BH, much reduced by wet surface BH, and further reduced by wet BH dive. This was attributed to more even distribution of pulmonary perfusion during submersion and compression. Terminal changes of the expirograms (phase IV) revealed a less even interregional pulmonary distribution of CO2 and a more even distribution of O2 after wet BH dive compared with wet surface BH. This difference was attributed to improved apical pulmonary perfusion at depth during the wet BH dives.

Alveolar gas exchange during breath-hold diving

1963 ◽  
Vol 18 (3) ◽  
pp. 471-477 ◽  
Author(s):  
E. H. Lanphier ◽  
H. Rahn
Keyword(s):  
Gas Exchange ◽  
Sea Water ◽  
Ambient Pressure ◽  
Acute Hypoxia ◽  
Normal Subjects ◽  
The Body ◽  
Breath Holding ◽  
Breath Hold ◽  
October 17 ◽  
Alveolar Gas Exchange

Use of a recompression chamber permitted simulation of breath-hold dives to 33 ft of sea water (2 atm abs). Four normal subjects made such dives during rest and mild exertion while delivering alveolar gas samples at frequent intervals by a partial-rebreathing procedure. The course of alveolar gas exchange differed greatly from that in ordinary breath holding. Oxygen uptake remained at near normal levels until ascent owing to the maintenance of alveolar Po2 by increased ambient pressure. Reversal of CO2 transfer occurred during descent, and little CO2 moved in the normal direction until ascent. Greater uptake of oxygen and retention of CO2 in the body led to lower final values of both alveolar Po2 and Pco2 than in comparable breath holding at the surface. Hyperventilation made possible longer dives with harder work, and in these the Po2 reached very low values on ascent. One subject showed a final Po2 of 24 mm Hg with evidence of reversed O2 transfer. Acute hypoxia on ascent is a likely cause of drowning in breath-hold diving. Submitted on October 17, 1962

Tissue oxygen and carbon dioxide stores and breath-hold diving in humans

1994 ◽  
Vol 77 (2) ◽  
pp. 542-547 ◽  
Author(s):  
M. H. Liner ◽  
D. Linnarsson
Keyword(s):  
Carbon Dioxide ◽  
Cardiac Index ◽  
Ambient Pressure ◽  
Venous Blood ◽  
Control Level ◽  
Intrathoracic Pressure ◽  
Breath Hold ◽  
Index Changes ◽  
Venous Blood Volume ◽  
Alveolar Gas Exchange

Alveolar gas exchange was studied in 11 submerged subjects during and after 75-s breath holds with or without a transient increase of ambient pressure to 3 ATA (20 msw). During surface breath holds (SBH), cardiac index fell to 73% of eupneic control but was partially restored at depth to 88% of control during breath-hold dives (BHD). O2 uptake fell to 84% of control during SBH and was restored to control level during BHD. The turnover of O2 stores was much slower during SBH than during the ensuing recovery. Carbon dioxide store dynamics were markedly slowed after BHD. We conclude that SBH and BHD are associated with large shifts in tissue O2 and CO2 stores and that much of these shifts can be explained by primary circulatory events. The changes in turnover rate for tissue O2 and CO2 stores could not be explained by the cardiac index changes alone but were compatible with peripheralization of venous blood volume and preferential peripheral vasoconstriction induced by apnea with elevated intrathoracic pressure during SBH. The transient compression during BHD reversed these central and peripheral circulatory changes by counteracting the increase in intrathoracic pressure.

Comparison of breath-hold and free-breathing quantitative pulmonary perfusion MRI

Pneumologie ◽  
2012 ◽  
Vol 66 (06) ◽  
Author(s):  
D Maxien ◽  
M Ingrisch ◽  
F Meinel ◽  
S Thieme ◽  
MF Reiser ◽  
...  
Keyword(s):  
Free Breathing ◽  
Perfusion Mri ◽  
Breath Hold ◽  
Pulmonary Perfusion

scholarly journals Interactive Effects in Two-Droplets Combustion of RP-3 Kerosene under Sub-Atmospheric Pressure

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1229
Author(s):  
Hongtao Zhang ◽  
Zhihua Wang ◽  
Yong He ◽  
Jie Huang ◽  
Kefa Cen
Keyword(s):  
Burning Rate ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Ambient Pressure ◽  
Interactive Effects ◽  
Propagation Time ◽  
High Speed Camera ◽  
Single Droplet ◽  
Fuel Droplets ◽  
Spacing Distance

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was recorded by a high-speed camera and a mirrorless camera. The results showed that the flame propagation time from burning droplet to unburned droplet was proportional to the normalised spacing distance between droplets and the ambient pressure. Meanwhile, the maximum normalised spacing distance from which the left droplet can be ignited has been investigated under different ambient pressure. The burning rate was evaluated and found to have the same trend as the single droplet combustion, which decreased with the reduction in the pressure. For every experiment, the interactive coefficient was less than one owing to the oxygen competition, except for the experiment at L/D0 = 2.5 and P = 1.0 bar. During the interactive combustion, puffing and microexplosion were found to have a significant impact on secondary atomization, ignition and extinction.

scholarly journals Effects of Ambient Pressure on the Instability of a Liquid Boiling Explosively at the Superheat Limit

1986 ◽  
Vol 108 (2) ◽  
pp. 418-424 ◽  
Author(s):  
D. Frost ◽  
B. Sturtevant
Keyword(s):  
Atmospheric Pressure ◽  
Bubble Growth ◽  
Absolute Stability ◽  
Pressure Field ◽  
Ambient Pressure ◽  
Small Temperature ◽  
Instability Theory ◽  
Two Stages ◽  
Single Droplets ◽  
Superheat Limit

The effect of ambient pressure on the intrinsic instability of rapid vaporization in single droplets boiling explosively at the limit of superheat has been studied experimentally and theoretically. The instability that distorts the evaporating interface and substantially enhances the mass flux at atmospheric pressure is suppressed at high pressure. The radiated pressure field is two orders of magnitude smaller from stabilized bubbles than from unstable. At intermediate pressures bubble growth occurs in two stages, first stable, then unstable. The Landau–Darrieus instability theory predicts absolute stability at atmospheric pressure for a spherical bubble, whereas the theory for planar interfaces yields results in general agreement with observation. The sensitivity of the instability to temperature suggests that small temperature nonuniformities may be responsible for quantitative departures of the behavior from predictions.

Research of Water Damage Resistance Performance of CAM in Low Temperature Condition

2013 ◽  
Vol 723 ◽  
pp. 157-162
Author(s):  
Jian Li ◽  
Qu Chao ◽  
He Ping
Keyword(s):  
Low Temperature ◽  
Atmospheric Pressure ◽  
Asphalt Pavement ◽  
Natural World ◽  
Chloride Salt ◽  
The Road ◽  
Normal Atmospheric Pressure ◽  
Water Damage ◽  
Resistance Performance ◽  
Complex Polymer

Under normal atmospheric pressure conditions, volume suddenly increases about 11% when the water freezes and decreased when the ice melts. The pressure can reach up to 2500 times of atmospheric pressure in the closed space when the water freezing. This is a very important characteristic of the natural world and the industrial. In low temperature condition, the snow on the pavement is easy to melt and freeze, and it will affect the road safety, increase the cracking of the road and accelerate asphalt pavement water damage. Bitumen is a mixture consisting of some extremely complex polymer hydrocarbons and hydrocarbon derivatives of non-metallic (oxygen, sulfur, nitrogen). Deicing salt is used to prevent freezing in that area, chloride salt is its main ingredient. When the water melting point reduced, it is not easy to icing but to penetrate the asphalt pavement. If the temperature is continued to reduce, salt solution will still freezing. At last, the pavement will form water damage in repeated freeze-thaw cycles conditions.

scholarly journals The influence of argon gas flow in the killing of staphylococcus epidermidis bacteria

2018 ◽  
Vol 16 (36) ◽  
pp. 134-139
Author(s):  
Ahmed Mahmoud Shihab
Keyword(s):  
Staphylococcus Epidermidis ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Biotechnological Applications ◽  
Plasma System ◽  
Argon Gas ◽  
Killing Rate ◽  
Normal Atmospheric Pressure ◽  
Non Thermal Plasma

In this research, non-thermal plasma system of argon gas is designed to work at normal atmospheric pressure and suitable for work in medical and biotechnological applications. This technique is applied in the treatment of the Staphylococcus epidermidis bacteria and show the role of the flow rate of Argon gas on the killing rate of bacteria, and it obtained a 100 % killing rate during the time of 5 minutes at the flow Argon gas of 5 liters/ min.

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