Subsequently, another prepared catheter was inserted through the right external jugular vein and advanced approximately 25 cm toward the upper hepatic inferior vena cava and fixed. After confirming sufficient reflux blood could be obtained from both catheters, the skin incision was continuously sutured with 5—0 nylon thread. Next, a midline incision of the upper abdomen was made about 30 cm below the xiphoid process, and the abdomen was opened.
The intestinal tract was held to the left to expose the hepatic portal region. An incision was made in the pancreatic vein and a catheter was inserted about 3 cm toward the hepatic portal. The midline incision was closed by continuous suture with 5—0 nylon thread. A median sternum incision was made from the xiphoid process toward the head. At the end of an expiration, the ventilator was removed to stop the animal breathing, and both lungs were manually compressed to mimic maximal forced exhalation by eliminating residual air.
The device contained a coupler consisting of a plug and socket with a built-in valve, so when the plug and socket were separated, the inflow of air into the beach ball was completely blocked. This reflected the manner in which a bag valve mask would be pressed. The H 2 -filled lungs were kept at maximal inspiration for approximately 30 s before the tracheal tube was connected to the ventilator and breathing was resumed.
The ball is expanding with H 2 released from a hydrogen-absorbing alloy in an H 2 filling device. Blood was collected from the three intravascular catheters.
First, blood was collected in the steady-state condition before the breath hold, with the chest open. Next, two sets of experiments were performed per pig. In the first set, blood was collected immediately after the breath hold and at 3, 10, 30, and 60 min after restarting ventilation. In the second set, blood was collected immediately after the breath hold and at 3 and 10 min after restarting ventilation.
A needle was inserted into the rubber lid of a To prevent outgassing, wax was immediately applied to the rubber lid and the injected hole was sealed. H 2 in the blood was released into the air phase in the closed vial.
Some of the air phase 0. Osaka, Japan. A calibration curve was obtained using standard H 2 gas of 0, 5, 50 and ppm. Each sample was measured twice. The concentration of the sample taken before H 2 inhalation was subtracted as background. One-way analysis of variance followed by a Tukey—Kramer multiple comparisons test was used to compare the H 2 concentrations between measurement sites.
All data were analyzed using GraphPad Prism 8. Mammalian cells do not produce H 2 as they lack the hydrogenase activity necessary for its formation. Instead, resident bacteria in the colon produce a considerable amount of H 2 via anaerobic fermentation of unabsorbed carbohydrates. It is generally assumed that H 2 produced by bacterial fermentation in the colon is transferred to the portal circulation and excreted through the breath.
In a previous breath gas analysis we conducted in healthy volunteers, we found that the concentration of H 2 in the breath varies widely 1—56 ppm between individuals [ 11 ]. In the present experiment, we detected minimal H 2 in the carotid artery CA in the steady-state condition in both pigs. We expect that the large difference between the two pigs in PV H 2 concentration is due to differences in H 2 production ability by colonic bacteria.
These results indicate that H 2 produced by bacteria in the colon is carried by the portal circulation, most of it is trapped in the liver, and the remaining H 2 is excreted from the lungs. In the first set of experiments, blood H 2 concentration was tracked until 60 min after breathing was resumed. In the second set, H 2 concentration in the circulating blood was monitored for 10 min. Fig 2A. This indicates that H 2 is not simply diffused, but diffuses while being carried by the bloodstream advection diffusion , and most H 2 is consumed by the tissues.
B Enlarged low-concentration areas from Fig 3A. In A and B, upper and lower graphs in each panel show readings from pig 1 and pig 2, respectively. Duplicate H 2 concentration measurements are overlaid. H 2 concentration decreases rapidly in arterial blood half-life: 92 s but more slowly in venous blood half-life: PV, s; IVC, s Fig 2B.
At 60 min after resuming breathing, H 2 in the CA had almost disappeared 2. These results indicate that H 2 is absorbed in the tissues, then gradually exits the tissues and returns to the heart via venous flow. In other words, a considerable amount of H 2 remains in the tissues throughout the body even 60 min after inhalation of H 2. Individual readings two readings from two animals from each intravascular catheter and means are shown. Data are one reading per animal from each intravascular catheter.
This is the first preclinical study to investigate the kinetics of single-dose inhalation of H 2 in the body. We devised a protocol that allows pigs to inhale H 2 only once. The ventilator was removed from the intubated pig at the end of expiration.
Both lungs were compressed by hand to release the remaining air. We defined this state as the estimated position at maximum exhalation. We kept the H 2 -inflated lungs intact for a while. We modeled the behavior of holding the breath after inhaling as much H 2 as possible using this series of methods. Since many animal experiments [ 12 — 14 ] and clinical studies [ 4 , 5 , 15 ] have been conducted to examine the protective effect of H 2 inhalation on the brain, the CA was chosen as the first blood collection point to prove that the inhaled H 2 can reach the brain efficiently.
The liver has a dual blood supply from the PV and the hepatic artery. Oxygen is supplied by the PV and the hepatic artery in half each.
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Download references. We would like to express our gratitude to Makoto Higuchi and Taiki Goto for their guidance in carrying out our experimental protocol. You can also search for this author in PubMed Google Scholar. All authors reviewed the manuscript. Correspondence to Koichiro Homma.
Reprints and Permissions. Yamamoto, R. Hydrogen gas distribution in organs after inhalation: Real-time monitoring of tissue hydrogen concentration in rat. Sci Rep 9, Download citation. Received : 09 October Accepted : 19 December Published : 04 February Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.
Provided by the Springer Nature SharedIt content-sharing initiative. Neuroscience Bulletin By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Advanced search. Plus water is a lot heavier and thicker than air, so it takes a lot more work to move it around. The main reason why gills work for fish is the fact that fish are cold-blooded, which reduces their oxygen demands.
Warm-blooded animals like whales breath air like people do because it would be hard to extract enough oxygen using gills. Humans cannot breathe underwater because our lungs do not have enough surface area to absorb enough oxygen from water, and the lining in our lungs is adapted to handle air rather than water. However, there have been experiments with humans breathing other liquids, like fluorocarbons. Fluorocarbons can dissolve enough oxygen and our lungs can draw the oxygen out -- see the last link below for some fascinating details!
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