Tidal Volume question

[nmbugs]

I was reading through this thread viewtopic.php?f=1&t=34491&st=0&sk=t&sd=a&start=30 and it seems my tidal volumes are too low.

Background first: I am in the process of going to National Jewish (go in May) for suspected pulmonary arterial hypertension. I am on oxygen 24/7 along with Resmed S9 autoset, pressures 6-13. After being on the autoset for 45 days my AHIs were still pretty hig, running between 10-13AHI and still desaturating even with oxygen so my doctor suggested I stop my sleeping medicine. Wow what a change, my AHIs dropped to under 4AHIs every night!! Still desaturating but I have to look at the positives whenever I can.

According to the above linked thread my tidal volume (weight x5 then weight x7) should be 585 and 819. However mine are as follows: Min 60 Med 340 95% 480 Max 740. When looking at the chart on sleepyhead it looks like when I go into the 60s I stay there for some time and it comes in big chunks throughout the night (usually in the early morning from 2am-6).The max TV often corresponds when I have my leaks (aka lift my mask to scratch my nose, which always seems to itch once the cpap mask goes on ). Now I know this data has its limits when it comes to accuracy but it at least it gives us something to go on. My new pulse oxy should be here any day and it will be able to stay on all night and record all data (which sleepyhead will be able to read too). Right now I can only track my night time desaturations when I can get the unit from my DME supplier which isn't that often but they use their own software (which didn't give times I desaturated just the lowest to highest and percentage of time spent in those periods) so I couldn't enter the data into my cpap software.

Okay so FINALLY my question is what do these numbers mean? Since I am having fewer apneas I thought my TVs would have gone up but they haven't. My doctors are mainly grumbling and keeping me in the dark, waiting and wanting to see what NJ will do. Anyways I am not worried or panicked over the numbers just curious. I have an okay understanding of peak flow (having asthma since I was 18) and now undergone several PFTs. I am assuming the TV if it isn't affected by my apneas then these are the times I would most likely be desaturating? I know desaturation happens during apnea events too but mine during the sleep study happened during non-apnea events. Perhaps that is when I have very shallow breathing which wouldn't trigger an apnea event but would surely show my TVs low, right? Did I just answer my own question, or is this logic flawed?

Thanks for any and all help. Oh and hello to everyone

[Todzo]

I was reading through this thread viewtopic.php?f=1&t=34491&st=0&sk=t&sd=a&start=30 and it seems my tidal volumes are too low.

Background first: I am in the process of going to National Jewish (go in May) for suspected pulmonary arterial hypertension. I am on oxygen 24/7 along with Resmed S9 autoset, pressures 6-13. After being on the autoset for 45 days my AHIs were still pretty hig, running between 10-13AHI and still desaturating even with oxygen so my doctor suggested I stop my sleeping medicine. Wow what a change, my AHIs dropped to under 4AHIs every night!! Still desaturating but I have to look at the positives whenever I can.

According to the above linked thread my tidal volume (weight x5 then weight x7) should be 585 and 819. However mine are as follows: Min 60 Med 340 95% 480 Max 740. When looking at the chart on sleepyhead it looks like when I go into the 60s I stay there for some time and it comes in big chunks throughout the night (usually in the early morning from 2am-6).The max TV often corresponds when I have my leaks (aka lift my mask to scratch my nose, which always seems to itch once the cpap mask goes on ). Now I know this data has its limits when it comes to accuracy but it at least it gives us something to go on. My new pulse oxy should be here any day and it will be able to stay on all night and record all data (which sleepyhead will be able to read too). Right now I can only track my night time desaturations when I can get the unit from my DME supplier which isn't that often but they use their own software (which didn't give times I desaturated just the lowest to highest and percentage of time spent in those periods) so I couldn't enter the data into my cpap software.

Okay so FINALLY my question is what do these numbers mean? Since I am having fewer apneas I thought my TVs would have gone up but they haven't. My doctors are mainly grumbling and keeping me in the dark, waiting and wanting to see what NJ will do. Anyways I am not worried or panicked over the numbers just curious. I have an okay understanding of peak flow (having asthma since I was 18) and now undergone several PFTs. I am assuming the TV if it isn't affected by my apneas then these are the times I would most likely be desaturating? I know desaturation happens during apnea events too but mine during the sleep study happened during non-apnea events. Perhaps that is when I have very shallow breathing which wouldn't trigger an apnea event but would surely show my TVs low, right? Did I just answer my own question, or is this logic flawed?

Thanks for any and all help. Oh and hello to everyone

What is happening with your Minute Volumes?

[nmbugs]

What is happening with your Minute Volumes?

Min 2.00 Med 4.38 95% 6.50 Max 9.38

[Todzo]

What is happening with your Minute Volumes?

Min 2.00 Med 4.38 95% 6.50 Max 9.38

Some of the measurements of some 60 years ago found average people breathing 3 liters per minute.

But today and average person uses about 6 liters per minute.

Average weight was about 170 pounds for a male but now runs about 195.

How much air you actually need depends upon your body and it's metabolism at the time. I think your numbers are lower than average.

I think the question for the doctor is "am I often hypercapnic"?

[nmbugs]

Some of the measurements of some 60 years ago found average people breathing 3 liters per minute.

But today and average person uses about 6 liters per minute.

Average weight was about 170 pounds for a male but now runs about 195.

How much air you actually need depends upon your body and it's metabolism at the time. I think your numbers are lower than average.

I think the question for the doctor is "am I often hypercapnic"?

Stupid question, can you still get hypercapnic if you are on 3L of oxygen? I was under the impression the oxygen helped my blood gases. Or because I am still desaturating my gases could be out of whack?

Thanks so much for the help. I see my pulm this week so I am trying to get all my ducks in a row and know what to talk to him about.

[Todzo]

Some of the measurements of some 60 years ago found average people breathing 3 liters per minute.

But today and average person uses about 6 liters per minute.

Average weight was about 170 pounds for a male but now runs about 195.

How much air you actually need depends upon your body and it's metabolism at the time. I think your numbers are lower than average.

I think the question for the doctor is "am I often hypercapnic"?

Stupid question, can you still get hypercapnic if you are on 3L of oxygen? I was under the impression the oxygen helped my blood gases. Or because I am still desaturating my gases could be out of whack?

Thanks so much for the help. I see my pulm this week so I am trying to get all my ducks in a row and know what to talk to him about.

Hypercapnia (too much CO2 in the blood) means that not enough air moved in enough of the active lung space to remove the CO2 in the blood. I tend to have the other problem (Hypocapnea - too little CO2 in the blood) likely due to the fact that I grew up in thin air (about a mile high) and so have more than average active lung space plus the fact that traumatic stress in my life tends high respiratory gain and levels (I tend to breath too much air).

The use of O2 would tend to reduce the ammount of air that you need to breath to meet your oxygen needs. It does not change the ammount of air you need to breath to remove CO2 from your body.

If I were you I would ask your specialist if I need to breath more or less air.

[JDS74]

Does Sleepyhead report breaths per minute? You may be having too shallow breathing (low minute ventilation/low tidal volume) and/or too low a breathing rate. Both would contribute to too high CO2 levels. Both would contribute to desaturations by not moving enough gases in and out. But if the breathing rate were high, then the CO2 levels would be normal or low and a low TV or MV would give you desats.

Do you have some sort of obstructive pulmonary disease that lead to oxygen use?
If you don't get a good number for FEV1 and FEV1/FVC, then not enough of the air in your total lung volume is getting exchanged. Just a thiught.

[nmbugs]

Does Sleepyhead report breaths per minute? You may be having too shallow breathing (low minute ventilation/low tidal volume) and/or too low a breathing rate. Both would contribute to too high CO2 levels. Both would contribute to desaturations by not moving enough gases in and out. But if the breathing rate were high, then the CO2 levels would be normal or low and a low TV or MV would give you desats.

Do you have some sort of obstructive pulmonary disease that lead to oxygen use?
If you don't get a good number for FEV1 and FEV1/FVC, then not enough of the air in your total lung volume is getting exchanged. Just a thiught.

They started me on oxygen because of hypoxia. I would desaturate to my 50s at night and during the day when walking around I would at 94% and then the next second drop to 78% real hard and fast. My pulm artery is expanding, went from 29mm to 32mm in 6 months and my pulmonary mean artery pressures are high. Sadly my cardio left my oxygen on during my heart cath (which he wasn't supposed to do) so my mean pressure was 23 (above normal) but not the 25 needed to do start PAH meds, which is why I am going to Denver. All the specialist are arguing over which is causing what, I have had asthma since I was 18 and my PFTs showed severe obstructive lung defect and restrictive lung defect. During those test "diffusing capacity for carbon monoxide is normal" whatever the heck that means.

Sleepyhead does resp rate. Mine are Min 4.00 Med. 11.60 95% 17.40 Max 23.00

Hypercapnia (too much CO2 in the blood) means that not enough air moved in enough of the active lung space to remove the CO2 in the blood. I tend to have the other problem (Hypocapnea - too little CO2 in the blood) likely due to the fact that I grew up in thin air (about a mile high) and so have more than average active lung space plus the fact that traumatic stress in my life tends high respiratory gain and levels (I tend to breath too much air).

The use of O2 would tend to reduce the ammount of air that you need to breath to meet your oxygen needs. It does not change the ammount of air you need to breath to remove CO2 from your body.

If I were you I would ask your specialist if I need to breath more or less air.

Thanks so much for explaining that to me!! I really need to learn more about the lungs since that is what is failing me now. I just tend to hide from it thinking if I don't know about it will go away/avoid me (which btw doesn't work )

I have been living at 4,500ft for about 10yrs. Huge change from growing up in Fl but I really didn't notice much difference when we moved here. When I go up to the mountains here now I notice a HUGE difference and have to increase my oxygen, so needless to say I avoid the mountains as much as possible

[JDS74]

Look at the COPD videos and others linked to my previous post for a good explanation of CO perfusion.

viewtopic/t96613/OT--Medical-Education- ... D-etc.html

[Sludge]

According to the above linked thread my tidal volume (weight x5 then weight x7) should be 585 and 819.

Only if you're 7 foot 7 inches tall.

Beware the GEs!

[JDS74]

I was reading through this thread viewtopic.php?f=1&t=34491&st=0&sk=t&sd=a&start=30 and it seems my tidal volumes are too low.

According to the above linked thread my tidal volume (weight x5 then weight x7) should be 585 and 819. However mine are as follows: Min 60 Med 340 95% 480 Max 740.

Tidal volume calculation using body weight is suspect. Using height is a better way to estimate.
Here is a link to an on-line Tidal Volume calculator that uses height to estimate tidal volume.

Tidal Volume Calculator for ARDS Protocol
http://www.tidalvolumecalculator.com/ca ... calculator

Increases in weight do nothing to increase lung size while increases/decreases in height are correlated with lung length and hence lung volume.

Given your numbers, are you perhaps about 5' 8" tall? That would get you to your reported tidal volumes.

[Sludge]

Here is a link to an on-line Tidal Volume calculator that uses height to estimate tidal volume.

Tidal Volume Calculator for ARDS Protocol
http://www.tidalvolumecalculator.com/ca ... calculator

That's for the ARDS protocol.

You have NFI what you're talking about.

[nmbugs]

I was reading through this thread viewtopic.php?f=1&t=34491&st=0&sk=t&sd=a&start=30 and it seems my tidal volumes are too low.

According to the above linked thread my tidal volume (weight x5 then weight x7) should be 585 and 819. However mine are as follows: Min 60 Med 340 95% 480 Max 740.

Tidal volume calculation using body weight is suspect. Using height is a better way to estimate.
Here is a link to an on-line Tidal Volume calculator that uses height to estimate tidal volume.

Tidal Volume Calculator for ARDS Protocol
http://www.tidalvolumecalculator.com/ca ... calculator

Increases in weight do nothing to increase lung size while increases/decreases in height are correlated with lung length and hence lung volume.

Given your numbers, are you perhaps about 5' 8" tall? That would get you to your reported tidal volumes.

No 5'2", so then my TV numbers are normal?

[NameGoesHere]

That's for the ARDS protocol.

You have NFI what you're talking about.

how about educating us?

[JDS74]

A different method of calculating tidal volume based on weight depends, not on your actual weight but on your "ideal body weight".
In your case, with a height of 5' 2", your ideal body weight would be about 125 pounds or 58 kg disregarding rounding errors.

The calculation gives a range of a minimum of 6mL/kg to a max of 10mL/kg.
That works out to be a range of 350mL to 580mL.

Those numbers are not too different from what you are seeing.

That being said, if you have concerns, please ask your doctor about your specific numbers.

Edit: Sorry about the typo on the units.