The math for hyperbaric oxygen can be confusing. I wrote an article for Today’s Wound Clinic about the ethics of off-label hyperbaric oxygen therapy. I said I’d provide the math here.
The earth’s atmosphere weighs down on us with a specific amount of pressure. If you are standing at sea level (let’s say you live in Houston, like me), then you are experiencing 1 “atmosphere” of pressure. Each time you descend into the ocean 33 feet, the additional amount of pressure your body is exposed to is equivalent to another “atmosphere.” By convention, when talking about pressurized environments, we “count” the fact that everyone starts at sea level, so we speak about “atmosphere absolute” (ATA).
Hyperbaric oxygen therapy was born out of the diving industry since chambers were used to recompress divers with “the bends.” In the USA, many gauges read in “feet of sea water” (or at least they used to), which is abbreviated “fsw.” I hope you are still with me. Trust me, this will be fun in a second.
If you dive 33 fsw into the ocean, you are now at 2 ATA (1 atmosphere of the earth + 1 atmosphere of water). Now let’s talk about the gases in the air. There’s another way to measure pressure and that is millimeters of mercury (mmHg). At sea level, the total atmospheric pressure is 760 mmHg. As you may remember from high school science, 21% of that is oxygen. Therefore, you are breathing approximately 160 mmHg of oxygen, and the rest is mostly nitrogen.
“Low pressure hyperbaric oxygen” is being provided at a number of medical spas, and inflatable chambers are even being sold to provide this. Let’s do the math to figure out how much oxygen they provide if pressurized with air.
A portable chamber can be pressurized to 1.3 ATA of pressure or 988 mmHg total pressure. If you pressurize it with air (like pumping up a tire), and are breathing the air inside the chamber, then you are breathing 160 mmHg Oxygen x 1.3 ATA = 208 mmHg. What is that equivalent to?
208 ÷ 760 = .27 or 27% oxygen
In other words, breathing air at 1.3 ATA in an inflatable chamber is equivalent to breathing 27% oxygen a mask, which can be accomplished sitting in my living room in Houston at sea level. You don’t need a chamber for that.
In a randomized controlled trial (RCT) widely cited by advocates of HBOT for autism, 62 young children with autism spectrum disorder (ASD) were treated with 24% oxygen administered at 1.3 ATA in a traditional hard-sided hyperbaric chamber. Their results were compared to a sham group treated with 21% oxygen (room air) in a chamber pressurized to only 1.03 ATA. The authors found that the “HBOT group” significantly improved in their overall functioning, language and social skills, eye contact, and cognitive behavior compared to the control group.
Let’s do the math on the CP study:
760 mmHg x 1.3 ATA = 988 mmHg (total pressure)
988 mmHg x .24 = 237 mmHg O2 breathed by the children in the chamber
237 ÷ 760 = .31 = 31% Oxygen at sea level
The amount of oxygen provided to the children in this autism RCT could have been easily achieved at ground level breathing oxygen from a mask. In other words, the children who were touted as receiving “hyperbaric oxygen therapy,” could have been treated just as easily without going into a chamber. Oxygen breathing at sea level can provide a higher partial pressure of oxygen with less risk of side effects and at much lower cost than “low pressure hyperbaric oxygen” in a hyperbaric chamber.
I am an open-minded skeptic on the use of HBOT for most off-label conditions, but I am a firm believer in math and the physics of gas laws. I kid you not that there is real discussion as to whether the added NITROGEN is beneficial, and there is further discussion about the fact that simply BEING in a chamber seems to help some people with benefits beyond the placebo effect that may have a lot to do with the environment created by the trial. That does NOT change the math.
Dr. Fife is a world renowned wound care physician dedicated to improving patient outcomes through quality driven care. Please visit my blog at CarolineFifeMD.com and my Youtube channel at https://www.youtube.com/c/carolinefifemd/videos
The opinions, comments, and content expressed or implied in my statements are solely my own and do not necessarily reflect the position or views of Intellicure or any of the boards on which I serve.
Your characterization of being able to achieve the same oxygen availability with oxygen mask “in a living room” ignores a couple of significant factors/benefits from the pressure itself, including:
(1) increase in oxygen uptake transport capacity of the blood under pressure (including plasma carrying oxygen separately from red blood cells)
(2) oxygen saturation through the skin/tissue (not just through lungs),
(3) neurological and metabolic effects as the body senses adjusts to the changes in pressure (including consistently significant drops in glucose levels and inflammation).
There is a significant difference in blood/tissue oxygen saturation under pressure that could not be achieved even with higher oxygen mask supplementation levels even “in the hospital room”. The availability of similarly higher quantity of oxygen can be obtained with a mask, but not the same quality of uptake or impact of that oxygen.
While my basic understanding of this does not come from there, for convenience I include the Wikipedia page’s description regarding point (1) above:
“The therapeutic principle of HBOT lies in its ability to drastically increase partial pressure of oxygen in the tissues of the body. The oxygen partial pressures achievable using HBOT are much higher than those achievable while breathing pure oxygen under normobaric conditions (i.e. at normal atmospheric pressure). This effect is achieved by an increase in the oxygen transport capacity of the blood. At normal atmospheric pressure, oxygen transport is limited by the oxygen binding capacity of hemoglobin in red blood cells and very little oxygen is transported by blood plasma. Because the hemoglobin of the red blood cells is almost saturated with oxygen at atmospheric pressure, this route of transport cannot be exploited any further. Oxygen transport by plasma, however, is significantly increased using HBOT because of the higher solubility of oxygen as pressure increases.”
(1)>increase in oxygen uptake transport capacity of the blood under pressure (including plasma carrying oxygen separately from red blood cells)
You are talking here about the Henri’s law, which states that the concentration of a dissolved gas is proportional to its partial pressure over its solution. In the case of blood plasma, the coefficient is 0.0031 mL of O2 per mmHg of O2 per dL. Read more details here: http://www.umich.edu/~projbnb/cvr/O2transport.pdf
That means that at normal conditions with 21% of O2 in the air and 1 ATA, the partial pressure of O2 is 159 mmHg and the amount of O2 dissolved in 1dL of plasma is 0.49 mL.
At 1.3 ATA, it will be 0.0031*159*1.3=0.64 mL. However, in the case of breathing pure O2 instead of air, we will get 0.0031*760=2.35 mL per dL of plasma at 1ATA.
Now, let’s compare these values to the oxygen carried by hemoglobin (Hb). Hb is almost 100% saturated by O2 already at normal conditions, so it is not possible to increase amount of O2 delivered by Hb by increasing partial pressure of O2 over 159 mmHg (*). The amount of O2 bound to Hb in the lungs is 20 mL/dL. Approximately 20% of this amount, i.e. 4 mL/dL, is released to tissues. Therefore, by breathing air at 1.3 ATA, 4 mL/dL of O2 is delivered by Hb and 0.64 mL/dL by plasma, i.e. 4.64 mL/dL in total. Compare it to 4.49 mL/dL at 1 ATA. Therefore, increasing pressure to 1.3ATA will result in only insignificant 3% increase of O2 delivery relative to normal conditions.
In contrast, by breathing pure O2 at 1 ATA, the total amount of O2 delivered to the tissues will be 4+2.35=6.35 mL/dL, which is 41% increase relative to normal conditions.
In the case of classical hyperbaric therapy, a patient is breathing pure oxygen at increased pressure, typically 2ATA. At this condition there is 0.0031*760*2=4.71 mL/dL of O2 delivered by plasma only. This makes 4+4.71=8.71 mL/dL of O2 by Hb and plasma combined, which is 94% increase relative to normal conditions.
The conclusion is that Dr. Fife is correct. Breathing air in hyperbaric chamber is meaningless. You can achieve much better oxygen delivery by breathing pure oxygen at normal pressure.
(*) However, there is one assumption in these calculations. We assumed that since Hb is almost 100% saturated by oxygen even at normal conditions (i.e. 159 mmHg O2), it is not possible to increase the amount of O2 delivered by Hb by changing the partial pressure of O2 or the total pressure. In simple words we excluded the effect of pressure on oxygen delivery by Hb and considered only changes in oxygen concentration in the plasma according to the Henri’s law. Partially this assumption is correct, because it is surely not possible to increase the uptake of O2 by Hb in the lungs. However, I don’t know whether, and how, the increased hydrostatic pressure affects the release of oxygen from Hb in the tissues. It can have either positive or negative impact. I suppose, that it has negative impact, because O2 should be released from Hb to the plasma, and we already have higher concentration of O2 in the plasma at higher pressure. From the other hand higher hydrostatic pressure may facilitate conformation of Hb molecule to its “tense” state and facilitate O2 release. I doubt that the hydrostatic pressure increase above 1ATA can significantly influence the release of O2 by Hb, but it is certainly an interesting question to answer. If you have some information about this then please share.
Question(s) for you or anyone.
1. So 1.3ata offers little transfer of Oxygen from blood to tissue etc. based on gas law/math. yet 2.0ata passes significant amounts. So where does things start to change from the little of 1.3 to the significant. of 2.0??… at 1.5??? 1.7???
2. What about TIME? does the little benefits of 1.3 build up over time? Example if one used near 100% oxygen at 1.3 ata but stayed in the mHBOT 6 hours (slept over night for example) would there be an accumulating benefit? If so how much? As in would the build up total be near that of 2.0ata at the common 90min treatment… or half that oorrr??
thanx for insights anyone might can offer.
Do not sleep in the chamber for more than two hours at a time and leave at least 4 1/2 hours between treatments. Remember that hemoglobin is made by the body based on need. If you sleep in a chamber for long periods of time each day, you will not be making hemoglobin during that time. The cumulative effect over time will build up until your hemoglobin count will go down. The maximum O2 level that can be reached in the chamber at 2ata is reached in about 1hour. At 3 hours and 23 minutes, breathing pure oxygen, most people will go into a grand mall seizure. Please study before making assumptions about HBOT.
She’s not saying 3ATA 100% O2 can be achieved with a mask in your living room.
She’s just doing the math of Dalton’s Law: Breathing air at 1.3 ATA is equivalent in terms of oxygen delivery to tissues to breathing 27% oxygen at 1ATA.
The trial treating children with 24% oxygen administered at 1.3 ATA is looking primarily at the effect of putting a child in a tank, not the effect of increasing oxygen delivery.
Dr Fife did not include using a o2 concertrator at 10L face mask. Each liter of o2 increases plasma carrying capacity by 4 percent, let’s do the math. 10 liters/min 02 times 4 =fio2 inspired at 40 percent NOT 21. .4 times 988(1.3 ata) =395. Significant difference than 237. Almost Double o2 Respect the numbers. Hyperoxic Hypoxic paradox is what is important in body’s regenertion./ mitochondrial renewal. Too invloved to dx here.
what do you think about EWOL with prefilled bags (50 lpm+ delivery) vs sedentary hyperbaric? EWOL systems also include low oxgyen delivery for high altitude simulation where you get the contrast you mentioned. I’m trying to decide between the two systems. 1.5 inflatable or EWOL. This was prompted by the two recent studios in Israel around telomeres and cognitive performance, though they are using 2.0 ata
Yes agreed, I too am trying to compare methods of O2 delivery for high concentration. EWOL vs concentrator 10L to see if it can deliver same or close as HBOT 2ata.
Indeed. Breathing air at 2ATA will result in increased O2 levels by a factor of 3, because you are now storing it in the plasma and the lymphatic fluid. Your hemoglobin was already saturated when you got into the chamber, most likely.
Bit confusing for a few seconds when you were talking higher percentages of O2 at depth when in actual fact it is PPO2 your talking about.( The percentage is still 21% unless you injected O2 in the chambef)
But I get it.
You seem to know your stuff. Maybe you can help me. I have a mild hyperbaric chamber and every time I use it, the LPM on my oxygen concentrator lowers significantly because of the pressure in the hyperbaric chamber. How do you fix this problem?
Dr. Fife or Turkevych, I find your notes informative and insightful. Do your thoughts change if an o2 concentrator is added. My concentrator is rated at 93% o2 purity at 10 lpm. Will adding a concentrator to a 1.3 chamber increase o2 presence in blood or otherwise internally? Would a 1.4 chamber increase it much more? Using the math you provided it seems these combinations greatly increase o2 presence. I’m just not sure how to apply Heri’s law. Please share your thoughts.
Randel
Your concentrator has to be able to pump air at a rate higher or equal to the pressure inside the vessel. Some say that many common home concentrators will not but I am just a novice reading up on all this
Randel YES!, i posted regarding your question.
How significant is the pressure element between the different chambers? Is a 1.5 ATA chamber sufficient or do we need to go over the 2 ATA to get results? I cant find any research comparing different clinical results with different pressures.
Anyone come across any?
Seems the difference is not significant
https://www.portchiro.com/blog/article/2020/5/18/hyperbaric-oxygen-therapy-1-3-atm-room-temperature-just-effective-100-oxygen-2-4-atm-evidenced-research/
Try this . It is a recent Israeli experiment in AGING Journal Vol 12. Issue 22
‘Hyperbaric oxygen therapy increases telomere length and decreases immunosenescence in isolated blood cells: a prospective trial
Several HBOT studies come out every week and they consistently find improved wound healing and reduced inflammation. If scientists believed that increased oxygen was the driver they’d be testing oxygen masks, not pressurized tanks. The effect is from pressurization.
I live 30 mins away from Salton sea, which is 233 feet below sea level. If I used a 02 concentrator at the Salton sea would that be like being in a hyperbaric chamber? And if so, what level o2 would i set the concentrator to?
There are great differences between pure physics out side a biological unit made up of 50 trillion cells. The laws of physics and straight math will definitely altered by cellular biological effects, cellular signaling, HIF, the effect of stem cells and their numbers. Think about cold survival mechanisms.
More and more research is pointing to the cell signaling more than the O2 uptake as the root cause as to why HBOT is working so well. The body is responding from an internal relative HYPOXIA after the HBOT session ends with vasodilation, increases in SOD to regulate sugar in the body, and to improve epigenetic responses that improve angiogenesis and stem cell enhancement. Studies that show no difference between O2 levels are just confirming that it is cell signaling not O2 in the plasma as the main mechanism of action.
Wow, this whole thing is way off. Way off.
Who uses a 1.3 atm chamber with no supplemental oxygen? I suppose it’s possible. Typically a 20 psi back pressure 10 lpm oxygen source is used with a cannula. So they are now getting 93% oxygen as supplied. If a cannula vs mask then there is a cannula dilution factor. With a face mask that 93% oxygen might actually still be a pretty high number like 80%. So take 80% oxygen and add the 1.3 atm if at sea level.
Now try that with a cannula and your living room couch! Won’t even get anywhere close at all.
Agree 100% with Anon above. An oxygen concentrator would obviously be used inside the chamber bringing the oxygen partial pressure inside of the 1.33 ATA to about 6X normal ambient conditions. I’m quite surprised the author chose to exclude this info. Perhaps she’s on a payroll for the hard sided chamber industry. When will someone do the study to show the plasma (not hemoglobin) oxygen concentrations at various HBOT conditions???
Thank you Dr. Fife for posting this topic. I agree with the others that reviewed the math and it does check out. However, there is more to HBOT than just the delivery of oxygen. By definition, Hyperbaric oxygen therapy is both the delivery of pressure (greater than 1 ATA) and oxygen (greater than 21%). The delivery of 27% oxygen under normobaric conditions will provide the same amount of oxygen in the blood plasma as breathing normal air at 1.3 ATA. However the therapies are not identical. The effect of the pressure does provide an additional therapeutic benefit. Certainly, more studies are needed, but this study is often cited when discussing this topic of normobaric vs hyperbaric hyperoxia treatments:
https://pubmed.ncbi.nlm.nih.gov/19852540/
Conclusions of the study:
Intracranial pressure was significantly lower after HBO2 until the next treatment session (p or = 200 mm Hg.
This study demonstrates that when an individual is in a hyperbaric environment there is a significant decrease in intracranial pressure. Perhaps this decrease intracranial pressure provides some added benefit to the children in the study you cited. This study was done at 1.5 ATA and not 1.3 ATA and the hyperbaric group was also provided increased oxygen. Nonetheless, it seems to be the pressure and not the oxygen alone that decreases intracranial pressure.
ChatGPTs opinion: Critique and Incorrect Points:
Misinterpretation of Effectiveness:
Claim: “In other words, breathing air at 1.3 ATA in an inflatable chamber is equivalent to breathing 27% oxygen… You don’t need a chamber for that.”
Issue: The article misses an important distinction between the effects of pressurizing a chamber and just breathing supplemental oxygen at sea level. While it is true that increasing pressure can increase the partial pressure of oxygen, the overall effect on tissue oxygenation is not just a function of oxygen concentration but also pressure. The article overlooks how increased pressure helps oxygen dissolve in the plasma, making it available to tissues even when hemoglobin is saturated. This is the key therapeutic benefit of HBOT, which does not occur when you are simply breathing air at sea level, regardless of the oxygen concentration. So, the effectiveness of the chamber environment is not just about oxygen concentration—pressure plays a critical role.
Oxygen Concentration and Nitrogen:
Claim: “The amount of oxygen provided to the children in this autism RCT could have been easily achieved at ground level breathing oxygen from a mask.”
Issue: While the article correctly calculates the partial pressure of oxygen in the chamber, it fails to recognize that hyperbaric oxygen therapy has effects beyond just increasing oxygen concentration. The pressure in the chamber can enhance oxygen diffusion into tissues and support the oxygenation of hypoxic areas, which would not occur simply by breathing oxygen at sea level, even if the concentration were similar.
Additionally, nitrogen’s role in HBOT is complex and not fully understood. It’s true that nitrogen has no direct therapeutic effect in most HBOT protocols. However, it is part of the gas mixture and can have indirect effects such as promoting vasodilation and reducing inflammation. The article oversimplifies the role of nitrogen and dismisses it too easily.
Misleading Claim About Hyperbaric Oxygen vs. Oxygen at Sea Level:
Claim: The article suggests that providing supplemental oxygen at sea level is equivalent to using a hyperbaric chamber at 1.3 ATA.
Issue: This comparison is misleading because it disregards the differential effects of pressure. While oxygen concentration can be similar at 1.3 ATA and using a high-flow oxygen mask, the hyperbaric chamber allows for a greater dissolved oxygen in the plasma, which is what helps with wound healing, tissue regeneration, and other therapeutic effects.
Overlooking the Therapeutic Benefits of Pressurized Environments:
Claim: The article downplays the value of being in a pressurized environment, suggesting that the results could be achieved with just a high-flow oxygen mask.
Issue: The pressurized environment of the hyperbaric chamber is critical because it increases the overall oxygenation capacity by allowing dissolved oxygen to be absorbed directly into the plasma. This is a key mechanism that is not achieved by simply breathing oxygen at sea level. In HBOT, oxygen can reach tissues that are often less oxygenated in normal conditions, which is particularly useful in treating wounds, infections, or conditions like ischemia. This benefit is distinct from just the concentration of oxygen.
Other Considerations:
Ethics and Off-Label Use: The author raises concerns about off-label uses of HBOT, which is a valid discussion, especially since there is often limited evidence supporting some of these off-label treatments. However, the critique about the math should be balanced with an understanding that scientific studies and clinical outcomes often depend on more than just raw oxygen concentration and pressure, such as how oxygen is used at the tissue level.
Conclusion:
While the article does a decent job explaining some of the basic physics of gas laws, it ultimately oversimplifies the efficacy of hyperbaric oxygen therapy by missing critical aspects like the physiological impact of increased pressure and the dissolution of oxygen in the plasma, which is a key mechanism of HBOT’s therapeutic effects. It also downplays the role of the pressurized environment and nitrogen’s possible effects. The math is accurate, but the interpretation of that math with respect to the clinical efficacy of HBOT is misleading.
Math is correct. Interpretation wrong. Key mechanism of HBOT therapeutic effects is the physiological impact of increased pressure and dissolution of oxygen into plasma.
You are regurgitating basic junior year high school level physics. This is common knowledge.