Altitude diving

[emoreira]

Hi all, I've been reading the book Diving Science by Michael B. Strauss, MD and Igor V. Aksenov, MD PhD.
It mentions that our lungs are capable of handling an oxygen partial pressure from 0.158 to 2 ATAs.
Looking at the table of Atmospheric Pressure as a function of altitude, at 2,350 meters high (7,710 feet) the Atmospheric Pressure is 0.752 ATA and oxygen partial pressure is 0.158 ATA. If we go higher, we are exposed to hypoxia.
I remember to have spent a whole day at an altitude of 4.080 meters, where the Atmospheric Pressure was 0.6 ATA, which corresponds an oxygen partial pressure of 0.126 ATA, and I was OK, no oxygen required.

How long can a human being be at that altitude without the need of additional oxygen supply ?

I think that things are no so linear or easy. I should be missing something.

 

[mala]

maintaining consciousness below 1.6 pp02 is down to physiology and exertion.

you an stay as long as you want -many people live at or above that level.

 

[knotical]

Thank you for raising this question. I have seen knowledgeable, experienced people here on ScubaBoard state that a ppO2 of 0.16 is necessary to sustain life, but as someone who has lived for years at elevations with less than that, I know they're wrong.

I suspect the misunderstanding might come from statements in CPR classes that typical expired air is around .16 and that is sufficient to sustain life. In fact more than sufficient.

In commercial aircraft, typical equivalent effective cabin altitudes (“cabin pressure&#8221 are around 6900 feet, but 8000 feet is acceptable. 6900 feet translates to about 0.16 O2 and 8000 feet to about 0.155. If people aren’t getting sick in droves, then some number significantly below 0.16 is all that is necessary to sustain life.


The USN and NOAA Dive Manuals say
0.14 atm ppO2 – onset of hypoxic symptoms
0.08 atm – death

I wonder where the book got 0.158?

 

[emoreira]

Thank you for raising this question. I have seen knowledgeable, experienced people here on ScubaBoard state that a ppO2 of 0.16 is necessary to sustain life, but as someone who has lived for years at elevations with less than that, I know they're wrong.

I suspect the misunderstanding might come from statements in CPR classes that typical expired air is around .16 and that is sufficient to sustain life. In fact more than sufficient.

In commercial aircraft, typical equivalent effective cabin altitudes (“cabin pressure&#8221 are around 6900 feet, but 8000 feet is acceptable. 6900 feet translates to about 0.16 O2 and 8000 feet to about 0.155. If people aren’t getting sick in droves, then some number significantly below 0.16 is all that is necessary to sustain life.


The USN and NOAA Dive Manuals say
0.14 atm ppO2 – onset of hypoxic symptoms
0.08 atm – death

I wonder where the book got 0.158?

0.158 is the conversion of 120 millimeters of mercury (120 mmHg), which is mentioned as the minimun PPO2 required to sustain life in that book.
I do agree that after a 12 hour fly from South America to Europe, one is exhausted though nothing has been done during the fly except watch a movie, drink, eat and sleep.

 

[Duke Dive Medicine]

Supplemental O2 is typically required above an altitude of about 14,000 feet (4267 meters). 4080 meters is pretty close to that; you probably noticed a significant reduction in your activity tolerance at that altitude.

 

[dmoore19]

Supplemental O2 is typically required above an altitude of about 14,000 feet (4267 meters). 4080 meters is pretty close to that; you probably noticed a significant reduction in your activity tolerance at that altitude.

The body can acclimate to the altitude though. Extended stays at base camp for Everest climbers might be an example of that.

Pike's Peak is 14,110' and people makes the trip to the summit during the summer quite frequently. I know I was there in July one year, 95 deg in Manitou Springs and it was snowing up top.

 

[Duke Dive Medicine]

The body can acclimate to the altitude though. Extended stays at base camp for Everest climbers might be an example of that.

Pike's Peak is 14,110' and people makes the trip to the summit during the summer quite frequently. I know I was there in July one year, 95 deg in Manitou Springs and it was snowing up top.

Very true. Even acclimatized individuals won't perform to their sea-level max though.

One of the researchers who lectures here about once a year runs a high-altitude lab for the Army on Pike's Peak. He's sometimes amazed at the tourists who walk around up there.

 

[mala]

0.158 is the conversion of 120 millimeters of mercury (120 mmHg), which is mentioned as the minimun PPO2 required to sustain life in that book.
I do agree that after a 12 hour fly from South America to Europe, one is exhausted though nothing has been done during the fly except watch a movie, drink, eat and sleep.

to be active and conscious you do need about 16% depending on how fit you are and how active you want to be.

to sustain life underwater you must be conscious or you drown.

the level of 02 required to sustain life is far below 16%

 

[RMAdventure]

Very true. Even acclimatized individuals won't perform to their sea-level max though.

One of the researchers who lectures here about once a year runs a high-altitude lab for the Army on Pike's Peak. He's sometimes amazed at the tourists who walk around up there.

I've climbed several of the 14ers here in Colorado and I definitely notice a drop in my performance as I get closer to the summit.