08-07-2021, 07:29 PM
RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
"Sam, how can I be 100% certain that my very own gently used and meticulously maintained PR DreamStation or System One is shedding particles that I will surely inhale deeply into my lungs because I can't block them all reliably with an AB filter?"
The above quote is from my recent post # 1,014 on page 102 of this long discussion. The reason why the certainty of exposure to particles is 100% is that Philips finally explained what is happening on July 8 when they gave "Supplemental clinical information for physicians and providers for specific CPAP, Bi-Level PAP, and mechanical ventilator devices".
Philips wrote, "1. Foam degradation: Despite a low complaint rate of 0.03% (i.e. 3 in 10,000) in 2020 [1], Philips has determined from user reports and lab testing that the PE-PUR foam may slowly degrade - through a process called hydrolysis - and produce particulates which may enter the device’s air pathway where they could be ingested or inhaled by the user of impacted Continuous Positive Airway Pressure (CPAP), Bi-Level Positive Airway Pressure (Bi-Level PAP) and mechanical ventilator devices."
First some terminology, then some basic science to make Philips' admission above more user friendly. When Philips writes, "foam degradation" they are referring specifically to the issue of particles. The phrase they use for the off-gas problem is "chemical emissions". Hydrolysis is the ordinary term for any chemical reaction in which a molecule of water breaks one or more chemical bonds.
In order for any chemical reaction to occur, molecules must bump into each other. How are molecules of water able to contact your machine's foam? The water molecules are in the air, and we know them as humidity. If the relative humidity where you have your xPAP is above 0 (trust me, it is) then your foam is exposed to water molecules. Bumping occurs, and the foam degrades resulting in the infamous particles. Philips says so.
Philips wrote that the foam "may slowly degrade". They get away with writing such vague phrases because it is impossible to test every xPAP model under every combination of temperature, relative humidity and machine settings. They don't admit it, but the foam also may rapidly degrade.
What is useful about this Philips admission is that we have clues for assessing, in a relative way, our personal risk. Common sense tells us that:
1. The higher the room's humidity, the more water molecules, the more bumping, the more reactions, the more foam particles.
2. The more air passing through the device, the more water molecules pass through and touch the foam, the more chemical reactions, and you know the rest. My 950P produces a continuous 9.0 cm of H2O. I would have less exposure if the setting was lower, and more exposure if the setting was higher.
Temperature is another variable in your personal assessment of your relative risk. The hotter the environment, the faster the molecules move, the more bumping they do, etc. The rule of thumb is that a chemical reaction's rate doubles with every 10° C (about 18° F) increase of temperature. The relevant temperature is the temperature inside your xPAP's blower unit, which likely is warmer than the temperature inside the room. You may ask, "Doesn't the air flowing through the unit keep it cooled?" That's a great question. I don't have all the data.
Underneath your System One or DreamStation you'll probably find a sticker that says something like "12V - 5.0A" which means the machine operates at 12 volts and normally (assuming no electrical short) draws a maximum of 5 amps of electrical current. 5 amps of 12 volt electrical current is 5 X 12 = 60 watts of electrical power. Exactly the same energy use as an old school 60 watt incandescent light bulb. However, much of the xPAP's maximum power demand is from the humidifier. I have a watt meter, so I know that my 950P's power supply draws 0.27 watts. I don't use the humidifier. When the blower unit is turned off (including no display on the LCD), the unit's power use fluctuates around 2.23 watts. When the unit is delivering continuous 9.0 pressure to the mask the power consumption is about 3 watts when I exhale, 13 watts when I inhale, and 6 watts when I'm not breathing. On average I figure about 7.5 watts. Regardless of the electrical device, 3.412 BTUs (British Thermal Unit) of heat is produced per hour by one watt. One BTU is enough heat to raise the temperature of 1 pound of water by 1° F. The blower unit's case is plastic which is a great insulator and a lousy conductor of heat. Moreover, the enclosure is very small. The heat accumulating inside tends to stay there when the blower motor isn't running. The blower motor is the source of most of the heat. The second law of thermodynamics tell us that heat inside the xPAP blower unit will always move from the warm blower to the cooler foam until both are at the same temperature.
I like to think that it doesn't get terribly hot inside my 950P, but I won't know until I insert a temperature probe. When the unit is first turned off the blower motor is not instantly cool. With no air moving the temperature inside will climb.
Back to the personal assessment, for most of us there is more exposure to particles in the summer than there is in the winter when homes typically are a few degrees cooler. Homes tend to be more humid in the summer also. The higher the setting the harder the blower motor works and the more heat it produces. There's a double whammy with the higher pressure setting causing both more heat and more water molecules touching the foam.
The final variable is time. The more hours of xPAP you get, the more exposure you get.
DreamStation users, your device does the same physical work as the older System One equivalent model, and DreamStation I assume has a richer feature set. So DreamStation likely draws comparable power and produces comparable heat, maybe a little bit more.
Back to our $20 science word, hydrolysis. PE-PUR foam has been in commercial use since about 1957. I've found proof that researchers knew as long ago as 1993 that hydrolysis causes PE-PUR foam to degrade. We don't know yet what Philips knew in 2009 when they selected PE-PUR foam. But we know for a fact that they could have known about PE-PUR foam degradation and arguably should have researched the material's known life cycle.
The above quote is from my recent post # 1,014 on page 102 of this long discussion. The reason why the certainty of exposure to particles is 100% is that Philips finally explained what is happening on July 8 when they gave "Supplemental clinical information for physicians and providers for specific CPAP, Bi-Level PAP, and mechanical ventilator devices".
Philips wrote, "1. Foam degradation: Despite a low complaint rate of 0.03% (i.e. 3 in 10,000) in 2020 [1], Philips has determined from user reports and lab testing that the PE-PUR foam may slowly degrade - through a process called hydrolysis - and produce particulates which may enter the device’s air pathway where they could be ingested or inhaled by the user of impacted Continuous Positive Airway Pressure (CPAP), Bi-Level Positive Airway Pressure (Bi-Level PAP) and mechanical ventilator devices."
First some terminology, then some basic science to make Philips' admission above more user friendly. When Philips writes, "foam degradation" they are referring specifically to the issue of particles. The phrase they use for the off-gas problem is "chemical emissions". Hydrolysis is the ordinary term for any chemical reaction in which a molecule of water breaks one or more chemical bonds.
In order for any chemical reaction to occur, molecules must bump into each other. How are molecules of water able to contact your machine's foam? The water molecules are in the air, and we know them as humidity. If the relative humidity where you have your xPAP is above 0 (trust me, it is) then your foam is exposed to water molecules. Bumping occurs, and the foam degrades resulting in the infamous particles. Philips says so.
Philips wrote that the foam "may slowly degrade". They get away with writing such vague phrases because it is impossible to test every xPAP model under every combination of temperature, relative humidity and machine settings. They don't admit it, but the foam also may rapidly degrade.
What is useful about this Philips admission is that we have clues for assessing, in a relative way, our personal risk. Common sense tells us that:
1. The higher the room's humidity, the more water molecules, the more bumping, the more reactions, the more foam particles.
2. The more air passing through the device, the more water molecules pass through and touch the foam, the more chemical reactions, and you know the rest. My 950P produces a continuous 9.0 cm of H2O. I would have less exposure if the setting was lower, and more exposure if the setting was higher.
Temperature is another variable in your personal assessment of your relative risk. The hotter the environment, the faster the molecules move, the more bumping they do, etc. The rule of thumb is that a chemical reaction's rate doubles with every 10° C (about 18° F) increase of temperature. The relevant temperature is the temperature inside your xPAP's blower unit, which likely is warmer than the temperature inside the room. You may ask, "Doesn't the air flowing through the unit keep it cooled?" That's a great question. I don't have all the data.
Underneath your System One or DreamStation you'll probably find a sticker that says something like "12V - 5.0A" which means the machine operates at 12 volts and normally (assuming no electrical short) draws a maximum of 5 amps of electrical current. 5 amps of 12 volt electrical current is 5 X 12 = 60 watts of electrical power. Exactly the same energy use as an old school 60 watt incandescent light bulb. However, much of the xPAP's maximum power demand is from the humidifier. I have a watt meter, so I know that my 950P's power supply draws 0.27 watts. I don't use the humidifier. When the blower unit is turned off (including no display on the LCD), the unit's power use fluctuates around 2.23 watts. When the unit is delivering continuous 9.0 pressure to the mask the power consumption is about 3 watts when I exhale, 13 watts when I inhale, and 6 watts when I'm not breathing. On average I figure about 7.5 watts. Regardless of the electrical device, 3.412 BTUs (British Thermal Unit) of heat is produced per hour by one watt. One BTU is enough heat to raise the temperature of 1 pound of water by 1° F. The blower unit's case is plastic which is a great insulator and a lousy conductor of heat. Moreover, the enclosure is very small. The heat accumulating inside tends to stay there when the blower motor isn't running. The blower motor is the source of most of the heat. The second law of thermodynamics tell us that heat inside the xPAP blower unit will always move from the warm blower to the cooler foam until both are at the same temperature.
I like to think that it doesn't get terribly hot inside my 950P, but I won't know until I insert a temperature probe. When the unit is first turned off the blower motor is not instantly cool. With no air moving the temperature inside will climb.
Back to the personal assessment, for most of us there is more exposure to particles in the summer than there is in the winter when homes typically are a few degrees cooler. Homes tend to be more humid in the summer also. The higher the setting the harder the blower motor works and the more heat it produces. There's a double whammy with the higher pressure setting causing both more heat and more water molecules touching the foam.
The final variable is time. The more hours of xPAP you get, the more exposure you get.
DreamStation users, your device does the same physical work as the older System One equivalent model, and DreamStation I assume has a richer feature set. So DreamStation likely draws comparable power and produces comparable heat, maybe a little bit more.
Back to our $20 science word, hydrolysis. PE-PUR foam has been in commercial use since about 1957. I've found proof that researchers knew as long ago as 1993 that hydrolysis causes PE-PUR foam to degrade. We don't know yet what Philips knew in 2009 when they selected PE-PUR foam. But we know for a fact that they could have known about PE-PUR foam degradation and arguably should have researched the material's known life cycle.
