Residual Volume of lungs and OOA

"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

"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

Ken wrote:
> "Nigel Hewitt" wrote in message

>> 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?

I think you'll find Lee is deliberately vague on that point. He is not
doing maths and he has done it in the water which counts for more
than our armchair diving. I agree with him that an open airway is enough
but it took me a long time to learn to consciously control the valve
in my head that switches neither/mouth/nose/both and I'd hate
my life to hang on it. Moving gas, I hum rather than the PADI
'blow bubbles', makes it much more sure to be open.

>> 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.

Wooo. Haemoglobin only ever gas transfers with the plasma that
surrounds it. As the ppO2 in the lungs drops as you ascent the
gas transfer in the Alveoli may reverse and hence haemoglobin
also under certain circumstances. There is no magic one way valve,
just basic physics, at work here. Consider the Freediver's Samba.
This always occurs shallow and I've been grabbed returning from a
rather slow 22m dive where I remembered it right to the surface but
was then told I sambered as I stated to breath down.

nigelH

Ken wrote:
> "Nigel Hewitt" wrote in message

>> 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?

I think you'll find Lee is deliberately vague on that point. He is not
doing maths and he has done it in the water which counts for more
than our armchair diving. I agree with him that an open airway is enough
but it took me a long time to learn to consciously control the valve
in my head that switches neither/mouth/nose/both and I'd hate
my life to hang on it. Moving gas, I hum rather than the PADI
'blow bubbles', makes it much more sure to be open.

>> 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.

Wooo. Haemoglobin only ever gas transfers with the plasma that
surrounds it. As the ppO2 in the lungs drops as you ascent the
gas transfer in the Alveoli may reverse and hence haemoglobin
also under certain circumstances. There is no magic one way valve,
just basic physics, at work here. Consider the Freediver's Samba.
This always occurs shallow and I've been grabbed returning from a
rather slow 22m dive where I remembered it right to the surface but
was then told I sambered as I stated to breath down.

nigelH

Ken wrote:
> "Nigel Hewitt" wrote in message

>> 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?

I think you'll find Lee is deliberately vague on that point. He is not
doing maths and he has done it in the water which counts for more
than our armchair diving. I agree with him that an open airway is enough
but it took me a long time to learn to consciously control the valve
in my head that switches neither/mouth/nose/both and I'd hate
my life to hang on it. Moving gas, I hum rather than the PADI
'blow bubbles', makes it much more sure to be open.

>> 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.

Wooo. Haemoglobin only ever gas transfers with the plasma that
surrounds it. As the ppO2 in the lungs drops as you ascent the
gas transfer in the Alveoli may reverse and hence haemoglobin
also under certain circumstances. There is no magic one way valve,
just basic physics, at work here. Consider the Freediver's Samba.
This always occurs shallow and I've been grabbed returning from a
rather slow 22m dive where I remembered it right to the surface but
was then told I sambered as I stated to breath down.

nigelH

Ken wrote:
> "Nigel Hewitt" wrote in message

>> 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?

I think you'll find Lee is deliberately vague on that point. He is not
doing maths and he has done it in the water which counts for more
than our armchair diving. I agree with him that an open airway is enough
but it took me a long time to learn to consciously control the valve
in my head that switches neither/mouth/nose/both and I'd hate
my life to hang on it. Moving gas, I hum rather than the PADI
'blow bubbles', makes it much more sure to be open.

>> 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.

Wooo. Haemoglobin only ever gas transfers with the plasma that
surrounds it. As the ppO2 in the lungs drops as you ascent the
gas transfer in the Alveoli may reverse and hence haemoglobin
also under certain circumstances. There is no magic one way valve,
just basic physics, at work here. Consider the Freediver's Samba.
This always occurs shallow and I've been grabbed returning from a
rather slow 22m dive where I remembered it right to the surface but
was then told I sambered as I stated to breath down.

nigelH