Oxygen Use

Here's the place to ask all of your medical questions. But don't believe everything you read!

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CharlieTango
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Re: Oxygen Use

Postby CharlieTango » Tue Nov 11, 2014 7:43 pm

SportPilot wrote:
A normally aspirated engine in fact typically loses about 3% of horsepower for every 1000 feet of altitude."


True but the "thinner air' creates less drag.

The two lines intersect at ~7,500' DA, so for us its better performance up to that level.

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Re: Oxygen Use

Postby SportPilot » Tue Nov 11, 2014 7:55 pm

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Last edited by SportPilot on Sun Nov 16, 2014 8:24 pm, edited 1 time in total.

Jack Tyler
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Re: Oxygen Use

Postby Jack Tyler » Tue Nov 11, 2014 8:53 pm

"I don't detect the hypoxia if there is any..."

And yet, how would you know? Hypoxia's effects not only vary by person but also by one's health, how rested one is, how much stress one is under and so forth. I'd respectfully suggest, at the normal altitudes you report you fly, you spend the $40 a cheap pulse oximeter costs and take some readings under different conditions - early in the day, or on a flight after a long work day, or on each leg of a long day of flying. I encourage anyone who flies at altitude to do this; if nothing else it's an interesting experiment we can have with our favorite subject. (g)
Jack
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MrMorden
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Re: Oxygen Use

Postby MrMorden » Wed Nov 12, 2014 9:27 am

I have flown to 10,000ft in my CT. I was not there for long (~10-15min), and I didn't *feel* hypoxic, but again, how would I know? One of the first signs is a euphoric sense of well-being...

I have cruised at 7500-8500 for an hour or two at a time, with no ill effects except maybe feeling more tired at the end of the trip than normal. My most common cruise altitudes for longer trips are 4500-5500ft (~3500-4500AGL), and when just flying around the local patch it's usually 3000ft (~2000AGL).

My rule of thumb is to fly at the lowest altitude that provides safe margins on terrain and obstacle clearance. I recognize the advantages of flying higher, and generally agree overall it's safer in terms of glide distances and time to recover from problems. But the hypoxia issue is always on my mind, especially when considering flying above 7500ft. It does not take much cognitive impairment to affect the outcome of any emergency that might develop.

If I had to take a trip out west that necessitated flights for any significant time at or above 10,000ft, I'd really want to have a small O2 system available for safe travel. I might change my mind if I had more personal experience at those altitudes, but lacking that discretion is the better part of valor...
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CharlieTango
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Re: Oxygen Use

Postby CharlieTango » Wed Nov 12, 2014 9:50 am

MrMorden wrote:...But the hypoxia issue is always on my mind, especially when considering flying above 7500ft. ...


I have lived at 8,000' for 35 years. 36 years ago from 9,000' I hiked to 14,500' and back in a day. I have hiked and skied many peaks above 13,000' and I know my limitations. Mine are not very good but I don't feel impacted much until 13,000'.

O2 is needed for good night vision but otherwise the numbers that concern you guys are kinda low.

The typical tourist comes here from sea level and ski from 8,000' to 11,000' and feel no effects. About 1 in 5 million have a coronary.

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Re: Oxygen Use

Postby Wm.Ince » Wed Nov 12, 2014 10:57 am

MrMorden wrote:I have flown to 10,000ft in my CT. I was not there for long (~10-15min), and I didn't *feel* hypoxic, but again, how would I know? One of the first signs is a euphoric sense of well-being...
Other symptom include loss of color vision, nausia and/or impaired judgement. Those symptoms are not apparent until hypoxia is well underway. Besides those, there are other symptoms also.
Self-induced stressors, like smoking, bring on the symptoms sooner. It's all about lack of oxygen to the brain.

Be careful out there. . . . 8)
Bill Ince
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MrMorden
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Re: Oxygen Use

Postby MrMorden » Wed Nov 12, 2014 11:20 am

CharlieTango wrote:I have lived at 8,000' for 35 years.


That explains a lot of your posts...hypoxia! :lol:
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CTLSi
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Re: Oxygen Use

Postby CTLSi » Wed Nov 12, 2014 11:35 am

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Last edited by CTLSi on Sat Nov 29, 2014 11:01 pm, edited 1 time in total.

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Re: Oxygen Use

Postby MrMorden » Wed Nov 12, 2014 11:49 am

CTLSi wrote:I fly at 10 and 11k routinely. No effect. By the way, I live at 5500 feet. A sea level guy might not be able to do it, or a smoker or ex smoker, but it's no problem for those of us who have the red blood cells accumulated living at altitude.


There is not "no effect". There is no effect that you have perceived. Since perceptions are affected by hypoxia, the statement is dangerously flawed. I would bet money that every single human being on Earth has measurably worse performance in some regard at 10,000 feet MSL than at sea level.

In any case, flying higher is safer than flying lower.


Sure, until it's not. Is flying at 18,000ft AGL with no supplemental oxygen safer than flying at 1000ft AGL?

There are few absolutes here. Hypoxia can be just as deadly as flying into the ground. There is some point at which hypoxia risk outweighs those risks associated with lower altitude flight, and that point is different for each and every person. Unless you've done a hyperbaric chamber run with cognitive testing, there is no way to know what that point is in advance.
Andy Walker
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Jack Tyler
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Re: Oxygen Use

Postby Jack Tyler » Wed Nov 12, 2014 11:49 am

The issue isn't a coronary but impairment. I've seen many a skier who managed to consume a full bota bag of wine while skiing without a casualty, but that's not an endorsement on wine + skiing. I'm sure Charlie Tango is correct when suggesting the population at large manages to cope with high altitudes...but that isn't an observation that suits everyone equally nor does it necessarily suit a pilot who's flying, perhaps with passengers.

Just to offer a perspective: We recently were flying in company with a Navy NFO piloting his a/c, between 9,000 and 11,000 MSL. Coincidently, he'd just finished his 5-year hyperbaric chamber retraining at NAS Jax, was in his 30's and in excellent health. He began feeling hypoxic - for him, it was tingling in his arms - and treated it as an emergency, coordinating a quick descent with ATC. He did that because he has learned the onset of additional symptoms, at least for him, is rapid. At those altitudes, this was abnormal for him...but we'd been under-wing camping the previous two nights and he might not have been fully rested (just a guess on my part). I don't mean to lecture others about this, just making the observation that while most folks don't have problems most of the time, that leaves little wedges of opportunity that you might want to think about. A pulse oximeter is a simple way to buy both insurance and learn a bit about the variability of your body's performance...and it's cheap even by non-aviation standards. If you fly higher on occasion, it seems like a prudent thing to have along and routinely use.
Jack
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CharlieTango
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Re: Oxygen Use

Postby CharlieTango » Wed Nov 12, 2014 12:11 pm

Before I restricted my flying to unusually low altitudes i.e. below 11,000' I would confirm the need with a Pulse Oximeter. Pressurized air craft use 8,000' right?

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Re: Oxygen Use

Postby Merlinspop » Wed Nov 12, 2014 2:29 pm

CTLSi wrote:In any case, flying higher is safer than flying lower.

No, no it's not.

http://en.wikipedia.org/wiki/Coffin_cor ... ynamics%29
- Bruce

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Re: Oxygen Use

Postby CTLSi » Wed Nov 12, 2014 2:47 pm

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MrMorden
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Re: Oxygen Use

Postby MrMorden » Wed Nov 12, 2014 3:18 pm

CharlieTango wrote:Before I restricted my flying to unusually low altitudes i.e. below 11,000' I would confirm the need with a Pulse Oximeter. Pressurized air craft use 8,000' right?


That's a good idea, but I don't know if that really tells the full picture. One individual might show obvious signs of hypoxia at 92%, which is considered a "safe" reading, while another might not show visible signs at 88%, a "dangerous" reading.

I think individual experience is the best predictor. It's reasonable that you feel safe at the higher levels where you fly all the time, but as a flatlander I think caution would be warranted at those altitudes, even though I'm younger than you. I just don't have enough previous experience to know my limits.
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CharlieTango
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Re: Oxygen Use

Postby CharlieTango » Wed Nov 12, 2014 3:45 pm

Experience speaks to the past. My current and future limitations are diminished. If you have concerns the PO is the way to go.

You have no experience but you have concerns, this sets you up to fall victim to your imagination. Start with a PO and shorter duration at lower altitudes and build up over time.

Reasonable starting points are safe readings from your PO and the FARs

Sec. 91.211 — Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry—
(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and

(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.

(b) Pressurized cabin aircraft. (1) No person may operate a civil aircraft of U.S. registry with a pressurized cabin—

(i) At flight altitudes above flight level 250 unless at least a 10-minute supply of supplemental oxygen, in addition to any oxygen required to satisfy paragraph (a) of this section, is available for each occupant of the aircraft for use in the event that a descent is necessitated by loss of cabin pressurization; and

(ii) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.

(2) Notwithstanding paragraph (b)(1)(ii) of this section, if for any reason at any time it is necessary for one pilot to leave the controls of the aircraft when operating at flight altitudes above flight level 350, the remaining pilot at the controls shall put on and use an oxygen mask until the other pilot has returned to that crewmember's station.


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