Residual Volume of lungs and OOA

Nigel Hewitt wrote

> If you keep the air in your lungs during an ascent you will not be worried
> about O2. There is no 'designed in' over pressure valve in your lungs and
> holding your breath will probably kill you.

Depends on how deep you are when you start and how much gas is in the lungs
at that point. OOA tends to happen with lungs empty or nearly so. If your
lungs start at about 1/4 full, you can ascend from fairly deep without risk
of expansion injury. Take it from someone that had to do it, it's a lot
better to take advantage of the additional gas you can get from your tanks
than to test your ability to ascend holding your breath.

> Conversely look at freedivers. The most dangerous part of a freedive is
> the last 10m of the ascent where the expanding gas in the lungs has
> exactly the opposite effect as the oxygen partial pressure drops.

Nigel, my friend, I suspect you know better. Shallow water blackout is not
because the gas in the lungs draw O2 from the body. It is because the body
uses up the O2 in the tissues to a point that it drops below a PPO2 of .16
during the ascent, leading to unconsciousness.

> Sorry. This is a non-starter. Blow bubbles all the way to the surface
> just like they teach in every agencies diving 101.

Just goes to show how wrong Diving 101 can be. Your statement is true only
if you have a complete breathing system shut down. If your regulator is
still working and hooked to one or more tanks, you can get a breath or two
on the way up, even from a single tank. The more gas in your lungs and the
deeper you are, the more important it is to ensure you do not close off your
airway, but blowing bubbles is not the only way to do that. It's open when
you're breathing in too.

Lee

Nigel Hewitt wrote

> If you keep the air in your lungs during an ascent you will not be worried
> about O2. There is no 'designed in' over pressure valve in your lungs and
> holding your breath will probably kill you.

Depends on how deep you are when you start and how much gas is in the lungs
at that point. OOA tends to happen with lungs empty or nearly so. If your
lungs start at about 1/4 full, you can ascend from fairly deep without risk
of expansion injury. Take it from someone that had to do it, it's a lot
better to take advantage of the additional gas you can get from your tanks
than to test your ability to ascend holding your breath.

> Conversely look at freedivers. The most dangerous part of a freedive is
> the last 10m of the ascent where the expanding gas in the lungs has
> exactly the opposite effect as the oxygen partial pressure drops.

Nigel, my friend, I suspect you know better. Shallow water blackout is not
because the gas in the lungs draw O2 from the body. It is because the body
uses up the O2 in the tissues to a point that it drops below a PPO2 of .16
during the ascent, leading to unconsciousness.

> Sorry. This is a non-starter. Blow bubbles all the way to the surface
> just like they teach in every agencies diving 101.

Just goes to show how wrong Diving 101 can be. Your statement is true only
if you have a complete breathing system shut down. If your regulator is
still working and hooked to one or more tanks, you can get a breath or two
on the way up, even from a single tank. The more gas in your lungs and the
deeper you are, the more important it is to ensure you do not close off your
airway, but blowing bubbles is not the only way to do that. It's open when
you're breathing in too.

Lee

Nigel Hewitt wrote

> If you keep the air in your lungs during an ascent you will not be worried
> about O2. There is no 'designed in' over pressure valve in your lungs and
> holding your breath will probably kill you.

Depends on how deep you are when you start and how much gas is in the lungs
at that point. OOA tends to happen with lungs empty or nearly so. If your
lungs start at about 1/4 full, you can ascend from fairly deep without risk
of expansion injury. Take it from someone that had to do it, it's a lot
better to take advantage of the additional gas you can get from your tanks
than to test your ability to ascend holding your breath.

> Conversely look at freedivers. The most dangerous part of a freedive is
> the last 10m of the ascent where the expanding gas in the lungs has
> exactly the opposite effect as the oxygen partial pressure drops.

Nigel, my friend, I suspect you know better. Shallow water blackout is not
because the gas in the lungs draw O2 from the body. It is because the body
uses up the O2 in the tissues to a point that it drops below a PPO2 of .16
during the ascent, leading to unconsciousness.

> Sorry. This is a non-starter. Blow bubbles all the way to the surface
> just like they teach in every agencies diving 101.

Just goes to show how wrong Diving 101 can be. Your statement is true only
if you have a complete breathing system shut down. If your regulator is
still working and hooked to one or more tanks, you can get a breath or two
on the way up, even from a single tank. The more gas in your lungs and the
deeper you are, the more important it is to ensure you do not close off your
airway, but blowing bubbles is not the only way to do that. It's open when
you're breathing in too.

Lee

Nigel Hewitt wrote

> If you keep the air in your lungs during an ascent you will not be worried
> about O2. There is no 'designed in' over pressure valve in your lungs and
> holding your breath will probably kill you.

Depends on how deep you are when you start and how much gas is in the lungs
at that point. OOA tends to happen with lungs empty or nearly so. If your
lungs start at about 1/4 full, you can ascend from fairly deep without risk
of expansion injury. Take it from someone that had to do it, it's a lot
better to take advantage of the additional gas you can get from your tanks
than to test your ability to ascend holding your breath.

> Conversely look at freedivers. The most dangerous part of a freedive is
> the last 10m of the ascent where the expanding gas in the lungs has
> exactly the opposite effect as the oxygen partial pressure drops.

Nigel, my friend, I suspect you know better. Shallow water blackout is not
because the gas in the lungs draw O2 from the body. It is because the body
uses up the O2 in the tissues to a point that it drops below a PPO2 of .16
during the ascent, leading to unconsciousness.

> Sorry. This is a non-starter. Blow bubbles all the way to the surface
> just like they teach in every agencies diving 101.

Just goes to show how wrong Diving 101 can be. Your statement is true only
if you have a complete breathing system shut down. If your regulator is
still working and hooked to one or more tanks, you can get a breath or two
on the way up, even from a single tank. The more gas in your lungs and the
deeper you are, the more important it is to ensure you do not close off your
airway, but blowing bubbles is not the only way to do that. It's open when
you're breathing in too.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee

Ken wrote

> First, in such an ascent you must NEVER hold your breath and in fact
> breathe out continuously. As you ascend the volume of gas in your lungs
> would increase so as to pressure-equilibrate with the water surrounding
> you, which pressure is decreasing all the time. Hold your breath and the
> pressure in your lungs may well cause an alveolar rupture which would give
> to a pneumothorax or a gas embolus. Neither is pretty, both are capable of
> killing you.

> As you ascend (and take the example of breathing air at 30m) . . .

Good depth to discuss. Most divers find out they are OOA when they have
breathed out, not when they have a lung full of gas. Without getting into
the question of tidal flow and minimum percentage content of the lungs,
assume for a second that your lungs are only 1/4 full when you discover you
are out of gas at 30 meters. As you note, you are at a absolute pressure of
4 atmospheres. At the surface, the gas in your lungs will have expanded all
the way up to, you got it, one lung full of gas.

This is not suggesting it's a good idea to hold your breath while ascending.
It is only to point out that the degree of risk is not normally as severe as
taught. You should never ascend very far with the airways closed, but
breathing out is not the only way to keep them open. They're open when you
are inhaling too. As you ascend from our proposed 30 meters, the amount of
gas available from the tank benefits from the lowering of pressure. From
the 30 meter dive to the surface, you can actually get extra gas equal to 3
times the internal volume of your tanks. One ata stays in the tank. The
other two can be used. So figure out what the internal volume of your tanks
is, multiply it by 3 and divide it by whatever you figure the tidal volume
of your lungs is. That's how many additional breaths you get on your way to
the surface. Rather than exhale all the way, something you do only if you
have absolutely no other option, take advantage of the additional gas and
make a successful ascent a lot more likely.

> However as you ascend it is the case that there is sufficient oxygen in
> the mass of gas in your lungs so that you need never become hypoxic during
> such an ascent, so you need not fear for that.

That is not something you can depend on. There are too many variables.
Shallow water blackout is caused by the combination of O2 used by the body
tissues and reduced pressure that combine to bring the PPO2 to less than .16
ATA, the level normally considered necessary to maintain consciousness.

Lee