Residual Volume of lungs and OOA

Nigel Hewitt wrote

> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious.

Why complicate the words to make things more difficult. 1/4 means 1/4 full
whether it's in tha alvioli or in open spaces or wherever. Of course gas
can be trapped in the alvioli, but that's a completely separate issue. It's
a good reason for ascending slowly, but that's about it.

> A full breath at the surface does not leave me enough volume to even let
> me
> clear my ears with a normal scuba mask freediving to 30meters.

You freedive to 30 meters? You're better than I am, or ever was.

> I relish I will exhale on any ascent that involved breathing compressed
> air at depth.

One more time. All that is necessary is for the airway to be open.
Breathing in, breathing out, or neither as long as the airway is open,
excess pressure will adjust.

Lee

Nigel Hewitt wrote

> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious.

Why complicate the words to make things more difficult. 1/4 means 1/4 full
whether it's in tha alvioli or in open spaces or wherever. Of course gas
can be trapped in the alvioli, but that's a completely separate issue. It's
a good reason for ascending slowly, but that's about it.

> A full breath at the surface does not leave me enough volume to even let
> me
> clear my ears with a normal scuba mask freediving to 30meters.

You freedive to 30 meters? You're better than I am, or ever was.

> I relish I will exhale on any ascent that involved breathing compressed
> air at depth.

One more time. All that is necessary is for the airway to be open.
Breathing in, breathing out, or neither as long as the airway is open,
excess pressure will adjust.

Lee

Nigel Hewitt wrote

> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious.

Why complicate the words to make things more difficult. 1/4 means 1/4 full
whether it's in tha alvioli or in open spaces or wherever. Of course gas
can be trapped in the alvioli, but that's a completely separate issue. It's
a good reason for ascending slowly, but that's about it.

> A full breath at the surface does not leave me enough volume to even let
> me
> clear my ears with a normal scuba mask freediving to 30meters.

You freedive to 30 meters? You're better than I am, or ever was.

> I relish I will exhale on any ascent that involved breathing compressed
> air at depth.

One more time. All that is necessary is for the airway to be open.
Breathing in, breathing out, or neither as long as the airway is open,
excess pressure will adjust.

Lee

Nigel Hewitt wrote

> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious.

Why complicate the words to make things more difficult. 1/4 means 1/4 full
whether it's in tha alvioli or in open spaces or wherever. Of course gas
can be trapped in the alvioli, but that's a completely separate issue. It's
a good reason for ascending slowly, but that's about it.

> A full breath at the surface does not leave me enough volume to even let
> me
> clear my ears with a normal scuba mask freediving to 30meters.

You freedive to 30 meters? You're better than I am, or ever was.

> I relish I will exhale on any ascent that involved breathing compressed
> air at depth.

One more time. All that is necessary is for the airway to be open.
Breathing in, breathing out, or neither as long as the airway is open,
excess pressure will adjust.

Lee

On Mar 28, 12:47 am, Doh <D...@microsoft.com> wrote:
> judith.le...@googlemail.com wrote:
> > On Mar 25, 9:53 pm, "Eddie" <edd...@gmail.com> wrote:
> >> Hi guys,
> >> I have a query that I thought someone here may be able to help me
> >> with. I was in a conversation about lung capacities etc, and my friend
> >> was of the opinion that during a free ascent in an out of air
> >> situation, the expansion of the residual air in the lungs would cause
> >> more O2 to diffuse into the blood and 'buy more time' as it were. I
> >> would have thought that this wouldn't happen, as the PO2 in the lungs
> >> would decrease on the ascent and perhaps the reverse would happen
> >> (i.e. some of the bloods O2 would diffuse into the lungs, further
> >> lowering the PO2 in the blood). What would be more likely?
> >> Thanks,
> >> Eddie
>
> > Eddie, you will get a pneumothorax, on a free ascent, if you do not
> > breathe out all the way up. The residual air, using Boyles Law alone,
> > will dohule when you reach a depth of 10 metres from the surface.
>
> > Judith
>
> Ye, but the arguement was if he only started with (in this case) a half
> lungs full, he would be ok if he didn't breathe out at all.
> (Half lungs at ten metres becomes a lung full at 0M)- Hide quoted text -
>
> - Show quoted text -

I see what you mean, then I can't answer his orginal question.

Judith

Doh <Doh@microsoft.com> wrote:

> Ye, but the arguement was if he only started with (in this case) a half
> lungs full, he would be ok if he didn't breathe out at all.
> (Half lungs at ten metres becomes a lung full at 0M)

I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
flatten out so what 'a quarter full' might represent is dubious. A full
breath at the surface does not leave me enough volume to even let me
clear my ears with a normal scuba mask freediving to 30meters.

The big danger is there is nothing in our evolutionary environment that
could provide lung over pressure so we have no built in protection
against it. You can hold your breath against a pressure that will kill
you. If we had an over-pressure valve built in I'd say hang onto
everything you've got but as drowning in my own blood is not a prospect
I relish I will exhale on any ascent that involved breathing compressed
air at depth. Actually you have been breathing raised O2 levels (air at
10m = 0.42bar) so you can go a little bit longer and there are tricks
to stave off the discomfort from CO2. I don't think you will gain anything
O2 wize by holding a breath on the ascent as the O2 has already been taken
when the ppO2 was high and as it falls your lungs might actually take
oxygen back from your blood.

nigelH



--
Posted via a free Usenet account from http://www.teranews.com

Nigel Hewitt wrote

> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious.

Why complicate the words to make things more difficult. 1/4 means 1/4 full
whether it's in tha alvioli or in open spaces or wherever. Of course gas
can be trapped in the alvioli, but that's a completely separate issue. It's
a good reason for ascending slowly, but that's about it.

> A full breath at the surface does not leave me enough volume to even let
> me
> clear my ears with a normal scuba mask freediving to 30meters.

You freedive to 30 meters? You're better than I am, or ever was.

> I relish I will exhale on any ascent that involved breathing compressed
> air at depth.

One more time. All that is necessary is for the airway to be open.
Breathing in, breathing out, or neither as long as the airway is open,
excess pressure will adjust.

Lee

"Nigel Hewitt" <nigelhewitt@hotmail.co.uk> wrote in message
news:460a31d2$0$16341$88260bb3@free.teranews.com.. .
> Doh <Doh@microsoft.com> wrote:
>
>> Ye, but the arguement was if he only started with (in this case) a half
>> lungs full, he would be ok if he didn't breathe out at all.
>> (Half lungs at ten metres becomes a lung full at 0M)
>
> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious. A full
> breath at the surface does not leave me enough volume to even let me
> clear my ears with a normal scuba mask freediving to 30meters.

Exactly my point in my discussion with Lee Bell. What do you mean by 1/4
full given that they never empty, and 1/4 full from what point of reference?

In any case, suppose your maths is correct - half full at 10m = full at 0m,
therefore no need to breathe out. Tell me - how accurate is your
"lungfullometer"? Do you want to risk a pneumothorax / gas embolus, or do
you fancy doing the safe thing nd just breathe out anyway? Which is the
strategy with lower risk?



>
> The big danger is there is nothing in our evolutionary environment that
> could provide lung over pressure so we have no built in protection
> against it. You can hold your breath against a pressure that will kill
> you. If we had an over-pressure valve built in I'd say hang onto
> everything you've got but as drowning in my own blood is not a prospect
> I relish I will exhale on any ascent that involved breathing compressed
> air at depth. Actually you have been breathing raised O2 levels (air at
> 10m = 0.42bar) so you can go a little bit longer and there are tricks
> to stave off the discomfort from CO2. I don't think you will gain anything
> O2 wize by holding a breath on the ascent as the O2 has already been taken
> when the ppO2 was high and as it falls your lungs might actually take
> oxygen back from your blood.

While diffusion back from the blood to the lungs is a reality, it is a
reality of no importance. The haemoglobin dissociation curve is such that no
desaturation of haemoglobin will occur, and the only oxygen that will
diffuse back from the blood into the gas spaces of the lungs is that oxygen
which is in solution in the plasma.

The amount of oxygen contained in blood is proportional to the haemoglobin
concentration, but roughly speaking on average (as all our haemoglobin concs
differ (hopefully!) within the normal range there is no ONE correct figure)
100ml of arterial blood holds 20ml O2 at BTP, of which around 0.3ml is in
solution. In other words, 19.7 ml is bound to haemoglobin and will not
diffuse back into the air spaces at these pressures.

(BTP - analogous to STP, used by human physiologists, Body Temp + Pressure
where Body temp = 310K (37ºC) and Press = 1ATA)

Ken

"Nigel Hewitt" <nigelhewitt@hotmail.co.uk> wrote in message
news:460a31d2$0$16341$88260bb3@free.teranews.com.. .
> Doh <Doh@microsoft.com> wrote:
>
>> Ye, but the arguement was if he only started with (in this case) a half
>> lungs full, he would be ok if he didn't breathe out at all.
>> (Half lungs at ten metres becomes a lung full at 0M)
>
> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious. A full
> breath at the surface does not leave me enough volume to even let me
> clear my ears with a normal scuba mask freediving to 30meters.

Exactly my point in my discussion with Lee Bell. What do you mean by 1/4
full given that they never empty, and 1/4 full from what point of reference?

In any case, suppose your maths is correct - half full at 10m = full at 0m,
therefore no need to breathe out. Tell me - how accurate is your
"lungfullometer"? Do you want to risk a pneumothorax / gas embolus, or do
you fancy doing the safe thing nd just breathe out anyway? Which is the
strategy with lower risk?



>
> The big danger is there is nothing in our evolutionary environment that
> could provide lung over pressure so we have no built in protection
> against it. You can hold your breath against a pressure that will kill
> you. If we had an over-pressure valve built in I'd say hang onto
> everything you've got but as drowning in my own blood is not a prospect
> I relish I will exhale on any ascent that involved breathing compressed
> air at depth. Actually you have been breathing raised O2 levels (air at
> 10m = 0.42bar) so you can go a little bit longer and there are tricks
> to stave off the discomfort from CO2. I don't think you will gain anything
> O2 wize by holding a breath on the ascent as the O2 has already been taken
> when the ppO2 was high and as it falls your lungs might actually take
> oxygen back from your blood.

While diffusion back from the blood to the lungs is a reality, it is a
reality of no importance. The haemoglobin dissociation curve is such that no
desaturation of haemoglobin will occur, and the only oxygen that will
diffuse back from the blood into the gas spaces of the lungs is that oxygen
which is in solution in the plasma.

The amount of oxygen contained in blood is proportional to the haemoglobin
concentration, but roughly speaking on average (as all our haemoglobin concs
differ (hopefully!) within the normal range there is no ONE correct figure)
100ml of arterial blood holds 20ml O2 at BTP, of which around 0.3ml is in
solution. In other words, 19.7 ml is bound to haemoglobin and will not
diffuse back into the air spaces at these pressures.

(BTP - analogous to STP, used by human physiologists, Body Temp + Pressure
where Body temp = 310K (37ºC) and Press = 1ATA)

Ken

"Nigel Hewitt" <nigelhewitt@hotmail.co.uk> wrote in message
news:460a31d2$0$16341$88260bb3@free.teranews.com.. .
> Doh <Doh@microsoft.com> wrote:
>
>> Ye, but the arguement was if he only started with (in this case) a half
>> lungs full, he would be ok if he didn't breathe out at all.
>> (Half lungs at ten metres becomes a lung full at 0M)
>
> I'm not sure lungs work like that. Even 'fully' exhaled the alveoli don't
> flatten out so what 'a quarter full' might represent is dubious. A full
> breath at the surface does not leave me enough volume to even let me
> clear my ears with a normal scuba mask freediving to 30meters.

Exactly my point in my discussion with Lee Bell. What do you mean by 1/4
full given that they never empty, and 1/4 full from what point of reference?

In any case, suppose your maths is correct - half full at 10m = full at 0m,
therefore no need to breathe out. Tell me - how accurate is your
"lungfullometer"? Do you want to risk a pneumothorax / gas embolus, or do
you fancy doing the safe thing nd just breathe out anyway? Which is the
strategy with lower risk?



>
> The big danger is there is nothing in our evolutionary environment that
> could provide lung over pressure so we have no built in protection
> against it. You can hold your breath against a pressure that will kill
> you. If we had an over-pressure valve built in I'd say hang onto
> everything you've got but as drowning in my own blood is not a prospect
> I relish I will exhale on any ascent that involved breathing compressed
> air at depth. Actually you have been breathing raised O2 levels (air at
> 10m = 0.42bar) so you can go a little bit longer and there are tricks
> to stave off the discomfort from CO2. I don't think you will gain anything
> O2 wize by holding a breath on the ascent as the O2 has already been taken
> when the ppO2 was high and as it falls your lungs might actually take
> oxygen back from your blood.

While diffusion back from the blood to the lungs is a reality, it is a
reality of no importance. The haemoglobin dissociation curve is such that no
desaturation of haemoglobin will occur, and the only oxygen that will
diffuse back from the blood into the gas spaces of the lungs is that oxygen
which is in solution in the plasma.

The amount of oxygen contained in blood is proportional to the haemoglobin
concentration, but roughly speaking on average (as all our haemoglobin concs
differ (hopefully!) within the normal range there is no ONE correct figure)
100ml of arterial blood holds 20ml O2 at BTP, of which around 0.3ml is in
solution. In other words, 19.7 ml is bound to haemoglobin and will not
diffuse back into the air spaces at these pressures.

(BTP - analogous to STP, used by human physiologists, Body Temp + Pressure
where Body temp = 310K (37ºC) and Press = 1ATA)

Ken