*Sorry in advance for the novel*
I have to say that nicotine is the culprit in this situation. Whereas carbon monoxide is given a terrible reputation, it needs to be understood that it is also a natural product of the human body, is a neurotransmitter, anti-inflammitory agent, vasodialator, and signaling chemical. Therefore, the body will actually make use of the CO that you have absorbed, provided the levels are below those of traditional toxicity (still not a good thing).
You are basically claiming to vape around 100-110 mg of nicotine a day. So let's assume with all the inefficiencies accounted for from
tank to blood, of that you are taking in about 40% of the starting census via inhalation. That puts you at roughly the equivalent of 2 - 2 1/4 packs of smokes a day, assuming the accepted standard of approx. 1mg absorbed per analog. I don't know about you, but I never smoked half of that in my heaviest of days, and if I did it, I would be a mess.
Increasing the power of your device will infact increase the amount of liquid that can become superheated per firing of your device. Since heat of the coil is a function of the resistance and applied power (wattage, derived via [E/R]*E), and the amount of vapor production is a function the heat at the coil, liquid composition, and air flow (cubic inches, derived abstractly from the temperature of the liquid compared to the vaporization point of said liquid, multiplied by the air volume provided to create an aerosol vapor) and nicotine delivey is a function of the nicotine concentration of the liquid and the amount of liquid rendered into aerosol (derived from Volume * Concentration), the issue becomes interesting.
By increasing the power to your coil, you are hitting yourself twice. First, you are increasing the volume of nicotine present in your lungs. Secondly, you are increasing the rate at which the nicotine is made available to your blood. Since nicotine metabolizes out of a body at a set rate (depending on your rate of metabolism), you may be on a non-reduction curve. Simply put, you may be taking in more nicotine than your body can metabolize out. This means that in a given day, the lowest point of nicotine concentration you have may be the moment you wake up, and it will continue to climb from there, only dropping when you go to sleep. This could be the equivalent of having an IV drip of nicotine or caffine; your heart finds it harder to cope with as the day goes on.
To determine what effect true replacement has on your body, vape until you feel like you have no urge to smoke / vape at that moment, wait 30 minutes, and then test your BP. The nicotine will be at a nominal level in your blood at that point, and you will get an accurate snapshot. The main reason that using a BP monitor in a store is misleading is that ideally, you should have been at rest for at least 10 minutes, and preferrably half an hour to get your resting BP and pulse, which is the important number. Check this value 5-10 time throughout the day to start to get a true profile of your resting BP levels.
I would advise that you reduce your nic level in a primary
tank to the 6mg level and use it for chainvape, which puts you at a pack a day levels. Keep a second
tank or atty device around for cravings, and use your 18mg in that, and never for more than 5 minutes at a time, preferrably never less than 1 hour apart. See what happens at these levels and let us know. I think once the nic level is reduced to a less novel amount, you will see a tremendous difference. Remember, when looking for causes of a bodily issue the order is pathogenic, chemical, metabolic, hormonal, mental, extra-physical, psychological. Start with the horses and only hunt for zebras if the horses aren't to blame, so to speak.