why do medics give oxygen if for every breath of the 20% in the atmosphere, we exhale 16% back, meaning we already breath more than we can use?


why do medics give oxygen if for every breath of the 20% in the atmosphere, we exhale 16% back, meaning we already breath more than we can use?

In: Biology

Your body can’t just start using a higher fraction of oxygen by itself. Plus they may be exhaling more than 16%. If someone isn’t getting enough oxygen into their blood, they get supplementary oxygen at a higher concentration. The person may have fluid in their lungs, an irregular heartbeat, narrowing of lung airways, anemia, or other cause of hypoxia (low oxygen).

A person who isn’t breathing very quickly becomes oxygen deprived. Oxygen deprivation can lead to brain damage, so its important to get it in there before that happens or becomes worse.

The numbers you quote are for a NORMAL healthy person.

If a patient is already abnormal, it means they’re not exhaling out 16% as quoted. They’re absorbing less.

So instead you give them higher concentration Oxygen. So even though they’re absorbing less, it’s more total oxygen.

If a normal person absorbs 4% of 21% atmospheric, then giving an abnormal person that’s only absorbing 2% but out of say..35% oxygen. Means they’re actual absorbed about is more, even though it’s still less ratio wise.

If you’re taking normal breaths and breathing 8 liters of air per minute then inhaling 20% oxygen and breathing out 15% oxygen gets you plenty(modified numbers for easy math). That gives you 0.4L of oxygen per minute

But what if you’re sick and injured and aren’t taking full breaths? Well now instead of breathing in 8 liters per minute you’re getting just 3 liters per minute. Now you’re down to just 0.15L of oxygen per minute which isn’t nearly enough. Boosting the oxygen you breath in to 30% can help make up for the reduced lung capacity.

You could also have problems from smoking for years where even though you can pull in the same volume of air, your lungs are damaged so you can’t pull as much oxygen from the air as you used to. Boosting the oxygen concentration will reoxygenate your blood faster with the limited functional lung you currently have.

Things in nature will move from areas of high concentration or pressures to low concentrations or pressures.

For example, when you go to pee, there is a pressure difference between what’s inside your bladder and what’s outside of your body, thus urine flows out.

Oxygen flows from the environment into your body due to a pressure gradient (ie there’s higher pressures of oxygen outside of your body than inside of your body).

Oxygen in the air is 21%, the pressure of the atmosphere is 760mmHg (millimeters of mercury). The pressure that oxygen exerts is thus 159mmHg (21% of 760mmHg)

When the oxygen enters your respiratory tract, it becomes humidified which then dilutes the oxygen which brings the pressure of oxygen down to 149mmHg

Inside the parts of the lung where oxygen goes into your body (ie alveoli), the air is further diluted by the carbon dioxide that your body releases which then produces a pressure of oxygen of 100mmHg.

The pressure of oxygen in the blood is 40mmHg, and so the oxygen can travel rapidly from the environment into your lungs as there is a 60mmHg difference.

At 16%, the pressure of oxygen at the alveolus is 64mmHg, and thus the pressure gradient is a lot lower, which will slow down the rate of which oxygen can enter the body.