O2 Level in the blood and question related to the blood quiz from thursday

[Frackingawesome]

The Quiz from Thursday got me thinking and i would like some help understanding something.

We breath and atmospheric gas gets dissolved into our blood(the liquid/water part) according to Henry’s Law and Dalton’s Law. But this is just the liquid part of the blood.

Do the red blood cells and in particular Hemoglobin cary more O2? i mean in addition to the 21% that is dissolved in the liquid part of the blood at 1 atm? If so mow much more?

Does the Hemoglobin get the O2 that it carries from the Liquid part of the blood? or from the air in our lungs directly?

Basically how does this work more then we breath and get O2 in our blood?

 

[BrackaFish]

The Quiz from Thursday got me thinking and i would like some help understanding something.

We breath and atmospheric gas gets dissolved into our blood(the liquid/water part) according to Henry’s Law and Dalton’s Law. But this is just the liquid part of the blood.

Do the red blood cells and in particular Hemoglobin cary more O2? i mean in addition to the 21% that is dissolved in the liquid part of the blood at 1 atm? If so mow much more?

Does the Hemoglobin get the O2 that it carries from the Liquid part of the blood? or from the air in our lungs directly?

Basically how does this work more then we breath and get O2 in our blood?

O2 content in the blood is in two parts, dissolved and bonded to hemoglobin. When you have blood drawn in an ABG or arterial blood gas the blood is drawn post lungs from an artery. This gives you an idea of how well the lungs are working. A good value for the dissolved O2 would be 80-100. By far the vast majority of O2 is carried by the hemoglobin. You can keep someone alive without using any hemoglobin, but that would require a hyperbaric chamber.

 

[Frackingawesome]

if the hemoglobin carries x amount of O2 at 1 ATM does it cary 2x at 2 atm? or is that just the dissolved gas

 

[BrackaFish]

if the hemoglobin carries x amount of O2 at 1 ATM does it cary 2x at 2 atm? or is that just the dissolved gas

ATM only works with the dissolved part of the equation. If I remember correctly each hemoglobin has four points for O2 molecules to bind with. Unless there is an issue such as smoking, CO poisoning, etc by the time your ABG PO2 is 80-100mmhg, your hemoglobin is bonded with O2 about 94%-99%. After passing through your tissues the dissolved O2 has dropped to about 45-65mmHg and the hemoglobin has unloaded a bit less that half it’s O2. This of course is on room air in a “Normal “ situation.

 

[bubblemonkey2]

The topic of oxygen levels in the blood is particularly interesting this year, with SARS-Covid19 sufferers exhibiting reduced oxygen saturation due to effects on the respiratory and circulatory systems. Patients are seen to have blood oxygen levels far below what is expected, sometimes lower than is considered typical for conscious, normally behaving people. (Evidently those clinical boundary numbers may warrant revision, due to new evidence...)

A couple of other settings in which hypoxia is a concern are altitude mountaineering and of course, diving.

Climbers on Everest exhibit oxygen saturation levels as low as 50%, due to a reduced ambient oxygen pressure at altitude. Only 33% of sea level pressure up there--the oxygen partial pressure equivalent would be like breathing a 7% oxygen mix at sea level:
https://www.nejm.org/doi/full/10.1056/NEJMoa0801581

Divers subjected to recent hypoxic performance tests also survived oxygen saturation levels as low as 50%, under supervision of medical staff. They did not appear to improve in their ability to recognize or respond to dangerously hypoxic status, nor did they seem to remember a decline in performance or consciousness during the experiment. That is consistent with failures to monitor ppO2 in rebreather accidents, as well the risk in open-circuit diving of switching to the wrong hypoxic gas at insufficient ambient pressure.
https://dhmjournal.com/images/IndividArticles/49June/Mitchell_Hypoxia_2018-73(496).pdf

Competitive freedivers are also referenced briefly in the Everest study. They too obviously test and cross the boundary of what is survivable for blood oxygen levels, as evidenced by numerous blackout dives in which the diver goes for deeper and deeper goals until eventually passing upon surfacing from a dive.

 

[GJC]

The Quiz from Thursday got me thinking and i would like some help understanding something.

We breath and atmospheric gas gets dissolved into our blood(the liquid/water part) according to Henry’s Law and Dalton’s Law. But this is just the liquid part of the blood.

Do the red blood cells and in particular Hemoglobin cary more O2? i mean in addition to the 21% that is dissolved in the liquid part of the blood at 1 atm? If so mow much more?

Does the Hemoglobin get the O2 that it carries from the Liquid part of the blood? or from the air in our lungs directly?

Basically how does this work more then we breath and get O2 in our blood?

O2 moves from places where the concentration and pressure is higher to areas that have a lower concentration and pressure.

The O2 in air in your lungs moves across the alveolar membrane and capillary wall into the plasma (liquid part of blood) and then into red blood cells where it binds with hemoglobin.

Plasma only has about 3% of the O2 in your blood. 97% of the O2 in your blood is bound to hemoglobin inside the red blood cells.

 

[GJC]

O2 content in the blood is in two parts, dissolved and bonded to hemoglobin. When you have blood drawn in an ABG or arterial blood gas the blood is drawn post lungs from an artery. This gives you an idea of how well the lungs are working. A good value for the dissolved O2 would be 80-100. By far the vast majority of O2 is carried by the hemoglobin. You can keep someone alive without using any hemoglobin, but that would require a hyperbaric chamber.

You can carry more O2 in plasma under pressure, but you would probably die from oxygen toxicity from the pressure that would be required to dissolve enough O2 in the plasma to meet your body's needs.

 

[GJC]

if the hemoglobin carries x amount of O2 at 1 ATM does it cary 2x at 2 atm? or is that just the dissolved gas

Your plasma would carry twice the O2 molecules at twice the pressure.

The number of O2 molecules carried by hemoglobin does not change under pressure. To carry more O2 attached to hemoglobin, you would have to have more hemoglobin.

 

[BrackaFish]

You can carry more O2 in plasma under pressure, but you would probably die from oxygen toxicity from the pressure that would be required to dissolve enough O2 in the plasma to meet your body's needs.

You need around 3 ATM of 100%O2 for it to work. I have only heard of a couple of cases years ago of it being tried, both times for CO poisonings. Most hospitals now that can do cardiac surgery can put these patients on ECMO (heart/lung) bypass which is quite a bit easier to do, however it is mostly a last ditch effort.

The topic of oxygen levels in the blood is particularly interesting this year, with SARS-Covid19 sufferers exhibiting reduced oxygen saturation due to effects on the respiratory and circulatory systems. Patients are seen to have blood oxygen levels far below what is expected, sometimes lower than is considered typical for conscious, normally behaving people. (Evidently those clinical boundary numbers may warrant revision, due to new evidence...)

A couple of other settings in which hypoxia is a concern are altitude mountaineering and of course, diving.

Climbers on Everest exhibit oxygen saturation levels as low as 50%, due to a reduced ambient oxygen pressure at altitude. Only 33% of sea level pressure up there--the oxygen partial pressure equivalent would be like breathing a 7% oxygen mix at sea level:
https://www.nejm.org/doi/full/10.1056/NEJMoa0801581

Divers subjected to recent hypoxic performance tests also survived oxygen saturation levels as low as 50%, under supervision of medical staff. They did not appear to improve in their ability to recognize or respond to dangerously hypoxic status, nor did they seem to remember a decline in performance or consciousness during the experiment. That is consistent with failures to monitor ppO2 in rebreather accidents, as well the risk in open-circuit diving of switching to the wrong hypoxic gas at insufficient ambient pressure.
https://dhmjournal.com/images/IndividArticles/49June/Mitchell_Hypoxia_2018-73(496).pdf

Competitive freedivers are also referenced briefly in the Everest study. They too obviously test and cross the boundary of what is survivable for blood oxygen levels, as evidenced by numerous blackout dives in which the diver goes for deeper and deeper goals until eventually passing upon surfacing from a dive.

@bubblemonkey2 is correct about hemoglobin content. If your hemoglobin is low for whatever reason, bleeding etc you could get into trouble. The flip side is also true. When flat landers head into the mountains, they are usually short of breath. Over several days to weeks your body adapts by becoming more efficient and producing more hemoglobin. That is why quite a few endurance athletes train at altitude or in high altitude simulators. That is also one of the reasons the Sherpas can run rings around most of their clients in the mountains.

 

[Brett Hatch]

The Quiz from Thursday got me thinking and i would like some help understanding something.

We breath and atmospheric gas gets dissolved into our blood(the liquid/water part) according to Henry’s Law and Dalton’s Law. But this is just the liquid part of the blood.

Do the red blood cells and in particular Hemoglobin cary more O2? i mean in addition to the 21% that is dissolved in the liquid part of the blood at 1 atm? If so mow much more?

Does the Hemoglobin get the O2 that it carries from the Liquid part of the blood? or from the air in our lungs directly?

Basically how does this work more then we breath and get O2 in our blood?

Mark Powell's book Deco For Divers covers this question pretty well. I don't have the book in front of me, but my recollection of this area is that: 1) the plasma is governed by fluid dynamics, 2) the hemoglobin is governed by chemical bonds, 3) the hemoglobin is typically around 97% saturation at the surface.

So breathing air under 2 atm, yes the plasma will eventually become saturated to .42 PPO2, as expected by fluid dynamics (specifically, diffusion and perfusion). The approach will be asymptotic, ie quick at first and then slowing down as saturation is approached.

However, since the hemoglobin is already nearly at saturation (~97%), doubling the pressure will NOT double the amount of O2 attached to hemoglobin. At the very most it could increase to 100% saturation, an increase of about 3%. Not quite the zero change posted by @GJC. But a small enough change that to my knowledge, the physiological effects are negligible, so it's not unreasonable to just call it zero for our purposes.

Speaking of course not as a doctor (I didn't even study biology in college), and not a scuba instructor, just a guy who read Powell's book a few months back. Great book by the way, I highly recommend it if you are interested in these kinds of questions: its whole goal is to discuss the anatomy and physiology of the diver's body, and the target audience is an average layperson diver.