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O2 Mask Pressure Revisited  
User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Posted (14 years 5 months 1 week 4 days 13 hours ago) and read 836 times:

Please forgive me for reviving this topic, which was archived about 5 days ago. Unfortunately I missed the last couple of replies which left some questions unanswered.

Koopas asked:

Buff, Tristar,

Are we saying that the donning of oxygen masks at 35,000 ft is useless if oxygen is breathed at THAT same altitude without an emergency descent being performed?


Yes. That is why it is so important for the pilots to not let the cabin depressurize any more than possible. By descending the aircraft quickly from the airplane's altitude, meanwhile the cabin pressure altitude is rising. The two will meet somewhere in the middle. Unless the depressurization was catastrophic. And then the emergency descent becomes even more important.

1/ Are we also saying that the donning of oxygen masks is ONLY useful in the recovery of passengers from unconsciousness once at lower (and more breathable) altitudes?

2/ In other words, do the masks ONLY help at altitudes of less than 14,000?

Two questions - one answer: No and No:

1/ Donning of the pax masks in a timely fashion may prevent unconsciousness.

2/ Each individual has a different threshold at which their bodies absorb oxygen. Certain things can inhibit a body's ability: age, cigarette usage, disease, nutrition to name some. Some individuals practice high altitude breathing to get their body used to reduced oxygen. Remember the Mexico Olympics? Many athletes went to Denver Colorado, a similar elevation, to practice their sport. Over time a body can get used to reduced absorbtion. There are tribes in the Andes of Peru that live at 14,000 foot elevation.

Airliners that do not have automatic drop down oxygen are restricted to 25,000 feet. If you can, try to find an old chart entitled Times Of Useful Consciousness. Maybe it'll give you a better idea of how long you can last at a given altitude prior to passing out.

Once again, apologies for re-awakening a beast.

Best Regards,

Buff

10 replies: All unread, jump to last
 
User currently offlineKoopas From United States of America, joined Oct 1999, 172 posts, RR: 2
Reply 1, posted (14 years 5 months 1 week 4 days 11 hours ago) and read 768 times:

Buff:

I don't want to sound like I am beating a dead horse. You said:

"1/ Donning of the pax masks in a timely fashion may
prevent unconsciousness."

I only see 02 masks as being present to 1) delay passengers from falling into unconsciousness 2) aid in the recovery of passengers from a state of unconsciousness once at lower altitudes. From my understanding, donning of the masks will not prevent unconsciousness if the aircraft does not perform a descent.

Am I wrong?


Alex



User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 2, posted (14 years 5 months 1 week 4 days 11 hours ago) and read 771 times:

I wonder how people survive at the top of everest using only suplemental oxygen.

User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 3, posted (14 years 5 months 1 week 4 days 9 hours ago) and read 767 times:

Everest is 29,000+ feet. Climbers make a dash for the summit after spending years of preparations, and time on oxygen prior to the dash. They make the summit (or they don't), they take their pictures, they leave the summit. Some make it back down, lots don't. This discussion has taken place at 35,000 feet. Modern airliners fly at altitudes up to 41,000 feet. An understanding of the principle of oxygen partial pressures in the human body will aid in the understanding of this topic.

There are a few who have very little understanding of anything.

Pardon me forum readers, and pardon me Mr. Administrator, but Mr. Jetpilot - take a pill. If your attitude on this forum is reflected in your day to day operations, I expect I'll read about you one day.

Once again, my apologies for having raised this topic. Seemed there was a loose thread; had no idea there were loose cannons...


Best Regards,

Buff


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 4, posted (14 years 5 months 1 week 4 days 9 hours ago) and read 766 times:

Everest is 29,000+ feet. Climbers make a dash for the summit after spending years of preparations. Prior to the dash, they are breathing supplemental oxygen. They make the summit (or they don't), they take their pictures, they leave the summit. Some make it back down, lots don't. This discussion has taken place at 35,000 feet. Modern airliners fly at altitudes up to 41,000 feet. An understanding of the principle of oxygen partial pressures in the human body will aid in the understanding of this topic.

Once again, my apologies for having raised this topic. I thought there was a loose thread; had no idea there was a loose cannon...


Best Regards,

Buff


User currently offlinePilot1113 From United States of America, joined Aug 1999, 2333 posts, RR: 12
Reply 5, posted (14 years 5 months 1 week 3 days 23 hours ago) and read 763 times:

Buff--

I agree with you on the call about Everest. BTW, Jetpilot have you seen the OmniMax film, Everest? It explains a lot of what they (the climbers) go through on their ascent to the peak.

Indeed as Buff states, it takes years to prepare and make the climb. This climb isn't done in one day, nor is it done in one month. The climbers slowly ascend and once they make it to a certain point, they stop for a period of 3 weeks so that the red blood cells can reach a certain level to compensate for the lack of oxygen. The increase in red blood cells allows the climbers to use supplimental oxygen. It's also important to note that they don't use the oxygen all the time. This is also factored in the training; they must learn to climb without the oxygen. Once they make it to the peak, they take same amount of time coming down. They again stop at the designed point and altitude and allow the red blood cell count to lower. Then they continue their slow descent down.

Jetpilot, besides the training the climbers go through, they also take their sweet time getting to summit. This is a luxury that pilots and passengers don't have in a rapid decompression situation.

For a good novel on the training and the actual climb up Everst, read "Into Thin Air." I don't remember the author.

I hope this clears things up!

- Neil Harrison



User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 6, posted (14 years 5 months 1 week 3 days 21 hours ago) and read 761 times:

I need to remember I am dealing with someone who thinks the purpose of a SID is for lost communication procedures.

One who argues with an idiot may be mistaken for one also.


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 7, posted (14 years 5 months 1 week 3 days 20 hours ago) and read 760 times:

First, I fully realize this is an internet forum, and that "facts" & opinions must be taken at face value. Hence my continuing suggestion of not taking what I have posted as gospel - with regards my "facts", go look them up. I tend to research things before I let my name get attached to them. On occasion, I make a mistake or a typo. I like to think that when I err, I can acknowledge the error in good spirit, and thank the person who brought it to my attention. It has been my experience though that when a mistake is pointed out, name calling and sniping are insufficient grounds to make an individual recognize/acknowledge his/her error. Usually a rebuttal of substance works.

Second, if someone has an opinion, to me it doesn't make sense to say an opinion is wrong. Opinions are conclusions brought about in an individual's mind as a result of his/her knowledge. Now perhaps the opinion is founded upon knowledge that is faulty. In which case, questionning of the opinion holder may reveal the faulty knowledge, then step one above can be engaged. Subsequently perhaps the opinion will change based on updated knowledge. Isn't that what constitutes a discussion? Isn't that what forums like this are for?

A: "I think this."
B: "Oh, did you know about that?"
A: "You're right! Guess I will revise what I think, and now it's something else." etc etc

I have also observed on this particular forum, as is more common on others, many contributors withhold particulars about their identity and qualifications, as is their right. Others, and many more on this forum than others, have allowed their particulars including name and e-mail address to be viewed in the User Info section provided by the administration. Perhaps some of the bios are fake, but they probably are not. That is one thing that keeps me viewing this particular forum, that and the internationality of the contributors. There is world-wide representation here, and that is fantastic.


Best Regards,

Buff


User currently offlinePilot1113 From United States of America, joined Aug 1999, 2333 posts, RR: 12
Reply 8, posted (14 years 5 months 1 week 3 days 19 hours ago) and read 761 times:

I am not trying to start an arguement here, rather just to point things out. I just want to say that the way that you come off on your posts, it seems you have a 'macho' disposition. I think this persona makes it hard for you to take into consideration others' inputs. I get the feeling that you think that you have all the answers, of which you don't. Even I don't have the answers.

I still 'suffer' from this type of disposition too. I have been through failure after failure after failure. It seems that no matter what I put my hands to, I ALWAYS fail at it. However, even though I fail at it I keep going until I succeed. It took me two tries to get my drivers' license. (Please... I'm begging you not to say anything about this).

Now, to the point... all these failures have taken a toll on my ego and my outlook; I've become somewhat pessismistic. To protect myself I have become egotistical, pessismistic, and have taken the same 'macho' disposition. I am working to be a better person and I'm trying to resolve these issues.

I just hope you're not like this in the cockpit...

- Neil Harrison


User currently offlineMarrty From , joined Dec 1969, posts, RR:
Reply 9, posted (14 years 5 months 1 week 3 days 2 hours ago) and read 758 times:

Most of us have admiration and a great deal of respect for those who give us the factual and often detailed answers to the questions we ask. Sometimes, those with different opinions are looking for an argument.

Thanks Buff, the time and interest taken by a professional is appreciated by most of us who visit this forum.




User currently offlinePilot1113 From United States of America, joined Aug 1999, 2333 posts, RR: 12
Reply 10, posted (14 years 5 months 1 week 3 days 1 hour ago) and read 754 times:

Marty--

Well put indeed, old chap! I agree totally!

Thank you again for all the time and effort you have spent emailing me, Buff!

- Neil Harrison


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