07-02-2017, 01:25 AM
Rebreathing causing Hypercapnia (CO2 – Carbon Dioxide Poisoning)
Rebreathing causing Hypercapnia (CO2 – Carbon Dioxide Poisoning)
From what I have read, plus the advice received from Sleep Physicians and CPAP Technicians, getting acclimatised to CPAP is often a difficult process that everyone goes through and patience, tolerance and perseverance is needed. I am currently going through that process and it is very tough for many reasons.
Over the period of a couple of weeks the fatigue increased to a point where, when I got up from a sleep period with the CPAP equipment, I was suffering fatigue like I have never experienced before and sometimes had a headache. It became dangerous to drive and I could not work. I would dispense with the CPAP equipment and go back to bed until lunchtime. I became concerned there was more going on than just acclimatisation?
Equipment: RESMED S9 with H5i Humidifier and P10 Nasal mask
I noted that I was waking up during the night with a higher respiration rate. Initially I thought it was just agro with the hose, mask head straps, noise etc. However, I also noted that there was venting out of the P10 Mast when breathing in but either very little or none, when breathing out! When I squeezed the tube on the exhale, it was very hard to breath out, upon releasing the tube it was easy to breath out. This lead me to concerns about re-breathing causing hypercapnia (carbon dioxide poisoning).
Being a SCUBA diver/snorkeler/swimmer, trained for work in high CO2 environments, Breathing Apparatus and enclosed spaces, I am both conscious and subconscious alert to the actions of the non-return regulator valves and the volume of the exhaled air which are both positive and often quite noisy.
I note that RESMED has decided to:-
1) dispense with non-return valve(s) and instead use the back pressures of the CPAP and the mask’s diffuser.
2) use a high-tech mask diffuser to reduce the noise and effect of the flow.
So, with a diffuser such as this, the air volume and pressure become critical factors. Due to the shape and design of the vent holes, as the volume and pressure increase the back-pressure increases at a greater rate. This occurs due to turbulence as the air is forced through the vent holes faster than they want to allow.
This is easily tested by blocking the hose and breathing out slowly a lung-full of air. It is reasonably easy. Do the same and breath out quickly. There is a lot of resistance.
However, the P10 Manual states:
“The mask contains passive venting to protect against rebreathing. As a result of manufacturing variations, the vent flow rate may vary.”
[img]blob:http://www.apneaboard.com/4f42aa40-3f3a-49d7-b501-a09daf6b0947[/img]
A recent Spirometry Test revealed I could exhale up to a rate of 635 litre/min. This is way off this scale.
Another test that can be done;
WARNING: - DON’T DO THIS FOR MORE THAN A COUPLE OF BREATHS AS IT WILL CAUSE HYPERCAPNIA (Carbon Dioxide Poisoning).
Block the exhaust vents on the mask (just put fingers over them) on the exhale and compare the back pressure to when using the mask with the vents uncovered. If it is about the same or less, the back pressure in the supply tube is less than the back pressure from the vents so some (or all?) of your exhaled breath will be going down the supply tube, i.e. re-breathing. This test also reveals if there is a non-return valve anywhere in the system.
Whatever the result of the debate above it is a simple fact, in a system where there is no non-return valve, to avoid expiration going back down the tube and being re-breathed, the pressure provided by the CPAP machine must be always higher than the back pressure from the mask vent.
I assume that this is going to vary considerably from person to person and be dependent on the stage of sleep?
So, getting the pressure balance correct is problematic?
Is this one of the reasons why Sleep Physicians and Technicians don’t like the users adjusting their own machines?
The dangers of Hypercapnia (Carbon Dioxide Poisoning) are well known and researched. I go back to the days of having the regulator on the SCUBA tanks.
Re-breathing is now prevented by having the regulator on the mouthpiece.
Consequently, I assume that RESMED has put considerable time and research into preventing this happening?
However, there does not appear to be any advice to Consumers, Physicians or Technicians.
So far, the only advice I have seen is:
P10 – User Guide: “As with all masks, some rebreathing may occur at low CPAP pressures.”
I have emailed RESMED for some tips and advice to get the settings correct, but have not received any response.
As the user is locked out of the settings of the machine by the restrictions of the Sleep Physician’s Prescription and the enabling of the ‘S9 essentials’, the Patient is very much in the hands of the Sleep Physician and the Technicians.
If there is a risk of Hypercapnia, that needs to be closely monitored and managed. Will the data measuring of the ‘leakage’ during expiration, measure/reveal the level of re-breathing?
While I applaud RESMED for engineering such fine equipment. (They certainly did a much better job than the people who put Darth Vader back together!) I am concerned about the absence of information they are providing to Consumers, Physicians and Technicians.
In systems where there is no non-return in the supply line, should there be warnings about re-breathing causing Hypercapnia (Carbon Dioxide Poisoning)?
Should there be monitoring and measuring in place to ensure re-breathing is not occurring?
There was a marked change for the worse when the settings were changed from ‘Auto with EPR on’ to ‘fixed pressure (10) with EPR on’.
Currently, we are trialling turning off the EPR (Expiratory Pressure Relief). So far, this has resulted in a dramatic improvement.
Is it the solution? I don’t know as, in the absence of information I have tried to work this out from basic theory without access to the massive volumes of research that has been done.
If it is the EPR allowing the pressure in the supply tube to drop below the back pressure of the mask vents, should there be a warning about using it with masks that have no non-return valve in the supply line?
Has anyone had similar experiences?
Do you agree with the above?
From what I have read, plus the advice received from Sleep Physicians and CPAP Technicians, getting acclimatised to CPAP is often a difficult process that everyone goes through and patience, tolerance and perseverance is needed. I am currently going through that process and it is very tough for many reasons.
Over the period of a couple of weeks the fatigue increased to a point where, when I got up from a sleep period with the CPAP equipment, I was suffering fatigue like I have never experienced before and sometimes had a headache. It became dangerous to drive and I could not work. I would dispense with the CPAP equipment and go back to bed until lunchtime. I became concerned there was more going on than just acclimatisation?
Equipment: RESMED S9 with H5i Humidifier and P10 Nasal mask
I noted that I was waking up during the night with a higher respiration rate. Initially I thought it was just agro with the hose, mask head straps, noise etc. However, I also noted that there was venting out of the P10 Mast when breathing in but either very little or none, when breathing out! When I squeezed the tube on the exhale, it was very hard to breath out, upon releasing the tube it was easy to breath out. This lead me to concerns about re-breathing causing hypercapnia (carbon dioxide poisoning).
Being a SCUBA diver/snorkeler/swimmer, trained for work in high CO2 environments, Breathing Apparatus and enclosed spaces, I am both conscious and subconscious alert to the actions of the non-return regulator valves and the volume of the exhaled air which are both positive and often quite noisy.
I note that RESMED has decided to:-
1) dispense with non-return valve(s) and instead use the back pressures of the CPAP and the mask’s diffuser.
2) use a high-tech mask diffuser to reduce the noise and effect of the flow.
So, with a diffuser such as this, the air volume and pressure become critical factors. Due to the shape and design of the vent holes, as the volume and pressure increase the back-pressure increases at a greater rate. This occurs due to turbulence as the air is forced through the vent holes faster than they want to allow.
This is easily tested by blocking the hose and breathing out slowly a lung-full of air. It is reasonably easy. Do the same and breath out quickly. There is a lot of resistance.
However, the P10 Manual states:
“The mask contains passive venting to protect against rebreathing. As a result of manufacturing variations, the vent flow rate may vary.”
[img]blob:http://www.apneaboard.com/4f42aa40-3f3a-49d7-b501-a09daf6b0947[/img]
A recent Spirometry Test revealed I could exhale up to a rate of 635 litre/min. This is way off this scale.
Another test that can be done;
WARNING: - DON’T DO THIS FOR MORE THAN A COUPLE OF BREATHS AS IT WILL CAUSE HYPERCAPNIA (Carbon Dioxide Poisoning).
Block the exhaust vents on the mask (just put fingers over them) on the exhale and compare the back pressure to when using the mask with the vents uncovered. If it is about the same or less, the back pressure in the supply tube is less than the back pressure from the vents so some (or all?) of your exhaled breath will be going down the supply tube, i.e. re-breathing. This test also reveals if there is a non-return valve anywhere in the system.
Whatever the result of the debate above it is a simple fact, in a system where there is no non-return valve, to avoid expiration going back down the tube and being re-breathed, the pressure provided by the CPAP machine must be always higher than the back pressure from the mask vent.
I assume that this is going to vary considerably from person to person and be dependent on the stage of sleep?
So, getting the pressure balance correct is problematic?
Is this one of the reasons why Sleep Physicians and Technicians don’t like the users adjusting their own machines?
The dangers of Hypercapnia (Carbon Dioxide Poisoning) are well known and researched. I go back to the days of having the regulator on the SCUBA tanks.
Re-breathing is now prevented by having the regulator on the mouthpiece.
Consequently, I assume that RESMED has put considerable time and research into preventing this happening?
However, there does not appear to be any advice to Consumers, Physicians or Technicians.
So far, the only advice I have seen is:
P10 – User Guide: “As with all masks, some rebreathing may occur at low CPAP pressures.”
I have emailed RESMED for some tips and advice to get the settings correct, but have not received any response.
As the user is locked out of the settings of the machine by the restrictions of the Sleep Physician’s Prescription and the enabling of the ‘S9 essentials’, the Patient is very much in the hands of the Sleep Physician and the Technicians.
If there is a risk of Hypercapnia, that needs to be closely monitored and managed. Will the data measuring of the ‘leakage’ during expiration, measure/reveal the level of re-breathing?
While I applaud RESMED for engineering such fine equipment. (They certainly did a much better job than the people who put Darth Vader back together!) I am concerned about the absence of information they are providing to Consumers, Physicians and Technicians.
In systems where there is no non-return in the supply line, should there be warnings about re-breathing causing Hypercapnia (Carbon Dioxide Poisoning)?
Should there be monitoring and measuring in place to ensure re-breathing is not occurring?
There was a marked change for the worse when the settings were changed from ‘Auto with EPR on’ to ‘fixed pressure (10) with EPR on’.
Currently, we are trialling turning off the EPR (Expiratory Pressure Relief). So far, this has resulted in a dramatic improvement.
Is it the solution? I don’t know as, in the absence of information I have tried to work this out from basic theory without access to the massive volumes of research that has been done.
If it is the EPR allowing the pressure in the supply tube to drop below the back pressure of the mask vents, should there be a warning about using it with masks that have no non-return valve in the supply line?
Has anyone had similar experiences?
Do you agree with the above?
![[Image: kwbZMu8m.png]](http://i.imgur.com/kwbZMu8m.png)
![[Image: vNQqTcmm.png]](http://i.imgur.com/vNQqTcmm.png)
