I am 200 lbs and 43 years old.
My normal working SAC is very consistently .65 cfm / 18.4 lpm in doubles and a dry suit in cold water.
I use a normal scuba breathing pattern (slow reasonably deep inhale followed by 2-3 second pause and then a slow exhale). I make no effort to try to stretch things to improve my SAC rate.
Some things that help improve air consumption are:
1. Use a deep inhale and exhale as it reduces the percentage of dead air space (mouth and throat) in a given breath.
2. Avoid any wasted movement. This includes not only arm movement but also any torso/trunk movement or tension as those are very large muscles that burn lots of O2.
3. Relax
4. Be properly weighted and develop excellent buoyancy skills. Being over weighted increases the workload needed to maintain precision buoyancy. Finning up or down to maintain depth is very inefficient.
5. Develop good horizontal trim as it will greatly reduce the drag encountered in swimming. Being as little as 20 degrees off horizontal can easily double frontal area and drag.
6. Streamline your equipment as much as posisble. More drag requires more power which uses more O2 and creates more CO2, increasing your respiration rate.
7. Don't swim too fast in an attempt to get more miles per tank. Swimming twice as fast results in 4 times the drag and requires 4 times the power. Consequently going just a little faster requires a lot more O2 than you would expect and does not conserve your gas supply.
8. Pausing with full lungs for a few seconds (being careful not to close your airway) is fine, but longer pauses (skip breathing) only serve to increase CO2 retention which in turn causes elevated CO2 levels and exacerbates both narcosis and oxygen toxcity, so don't be tempted to artificially lower respiration to improve SAC. Nitrox won't make a difference as you produce the same amount of CO2 from the O2 you metabolize regardless of the O2 percentage of the mix and you have to exhale to eliminate the CO2.
My normal working SAC is very consistently .65 cfm / 18.4 lpm in doubles and a dry suit in cold water.
I use a normal scuba breathing pattern (slow reasonably deep inhale followed by 2-3 second pause and then a slow exhale). I make no effort to try to stretch things to improve my SAC rate.
Some things that help improve air consumption are:
1. Use a deep inhale and exhale as it reduces the percentage of dead air space (mouth and throat) in a given breath.
2. Avoid any wasted movement. This includes not only arm movement but also any torso/trunk movement or tension as those are very large muscles that burn lots of O2.
3. Relax
4. Be properly weighted and develop excellent buoyancy skills. Being over weighted increases the workload needed to maintain precision buoyancy. Finning up or down to maintain depth is very inefficient.
5. Develop good horizontal trim as it will greatly reduce the drag encountered in swimming. Being as little as 20 degrees off horizontal can easily double frontal area and drag.
6. Streamline your equipment as much as posisble. More drag requires more power which uses more O2 and creates more CO2, increasing your respiration rate.
7. Don't swim too fast in an attempt to get more miles per tank. Swimming twice as fast results in 4 times the drag and requires 4 times the power. Consequently going just a little faster requires a lot more O2 than you would expect and does not conserve your gas supply.
8. Pausing with full lungs for a few seconds (being careful not to close your airway) is fine, but longer pauses (skip breathing) only serve to increase CO2 retention which in turn causes elevated CO2 levels and exacerbates both narcosis and oxygen toxcity, so don't be tempted to artificially lower respiration to improve SAC. Nitrox won't make a difference as you produce the same amount of CO2 from the O2 you metabolize regardless of the O2 percentage of the mix and you have to exhale to eliminate the CO2.
very good.
