RE: Experience with Provent?
Essentially, it pointed out the testing methods for Provent seemed flawed, early results from local trials shown to me indicated that except for people with a low SA rating it would be ineffective or of limited effect, and after some give and take I opined that as a full on therapy method it would not replace CPAP, but it might be useful for vacations or other short term uses for some patients, but not for those who have shown severe AHI prior to treatment. This was then backed up by a patient from the UK trials, who confirmed the flawed method for testing in the trial he participated in. In the initial US 3 month trials the authors claimed a 40 percent reduction for patients with an AHI of 14 or so to 6 (a relatively mild apnoea) out of a median AHI over the entire study group of 12, compared to the 10 percent reduction on the placebo devices. That there could be any reduction on a placebo device is to me already curious and a little alarming. In a later follow up study, published in Journal Clinical of Sleep Medicine, the authors cherry picked the the 34 most compliant patients from the 127 patients of the the initial 3 month study, which skewed the data further. There the sustained improvement was said to be from 16 to 5 in median AHI. Given that many on this forum have AHI in the 30 and above range before treatment, the question of if this could be useful for forum members is a bit doubtful. Disclosure: Both studies were funded by Ventus Medical, partially conducted at private sleep centers, and all three authors report receiving financial payments from Ventus Medical. There is no data on cardiovascular outcomes from the use of Provent from these studies, so no conclusion can be drawn on that.
Since I was basing my initial opinion on raw data from a local study while the study was still in progress, and not the final data, I cannot comment further as to the eventual results of the study, which were not given to me, but I can say that in the data I did see, non placebo patients did not fare significantly better than placebo patients if they had started out with high AHI levels - this is to be seen in the light that "significant" would mean a large reduction to near sub clinical levels, which was never achieved in patients with high AHI, although low AHI patients did have reductions to or near sub-clinical levels in some cases. I did opine that data published by Provent seemed cherry-picked to emphasise the latter group's results, and the selection of patients weighted in favour of supporting their claims. However I stress that that is my opinion and not a proven fact. Provent was and is welcome at any time to make all raw data from the studies available for independent perusal at any time for a better opinion. Or better yet, to make production devices available for better controlled study after a fashion I shall discuss briefly further on. I should point out that all of the studies I had seen, independent of the raw data I mentioned from the local study, were funded by the people who made Provent. Independent studies may exist, but I had not seen details on such studies at the time of my posting. It is not known to me if the study leader in the local study received financial consideration from Ventus Medical.
I questioned the need for placebo patients in such a study, as there is no psychosomatic effect in SA at all, so far as we can see - the problem is mechanical and cannot be influenced by attitude or belief. As such, any reduction in AHI by a placebo device warrants further study and a close examination of the nature of the placebo device. While the study was called a double-blind study, one patient witnessed a phone call from the UK study to the study director in Zurich who decided which group the patient should belong to, thus violating the nature of a double blind study completely and invalidating that particular result.
My posting the above on this forum resulted in some trouble for me, and as such I prefer not to go into any greater detail on the efficacy Provent, save to say that I am of the opinion that if it works for long term treatment, it works on patients that are just above clinical levels of SA and not on those who's AHI rises to a level that many on the forum have. I cannot comment on whether it would be more effective for OA patients than CA patients - the scope of the Provent testing and their own marketing does not allow for that distinction to be made. However, Provent and EPAP as a whole is thought to be for OSA rather than CA.
There is an over the counter version called Theravent.
As to how EPAP works, it is to be noted that upper airway collapse has its origins at the end of expiration, when the pressure in the airway is at or near zero. It has been demonstrated that the upper airway cross sectional area progressively decreases in the four breaths prior to an obstructive apnea, with this area being smallest at the end of expiration, and as such creates a collapse at the next in-breath. EPAP is thought to create increased expiratory pressures which are maintained through the end of expiration and until the start of the subsequent inspiration, thus maintaining enough positive pressure to prevent collapse. However, the exact mechanism of how this might work is unclear, although several theories are prevalent. It is also important to note that patients who are CPAP compliant consistently, in studies, do far better with CPAP than with EPAP and achieve better relief of symptom. It may be that EPAP strips such as Provent or Theravent might be useful for non CPAP compliant patients, but I rather suspect that it would be better to use them to train such patients up to CPAP, as it is proven far more effective, and year on year use of EPAP strips is still not proven as clinically effective. It is also to be noted that in all trials, evaluation of effectiveness was made using in-lab PSG (polysomnography) rather than nightly home monitoring using recording pulse oxymeters. As such, there is no overall record of each nightly level of sO2sat desaturations to measure the actual effectiveness of nightly use. Instead the methods used for evaluation provide a limited picture rather than a fluid one and may skew the data set. Since wrist recording pulse oxymeters are comfortable and relatively inexpensive for the purposes of such testing, and the simplest way to gather effective data for the determination of apnoea events via sO2sat levels, I find the results to be at best relative and not conclusive. The use of placebo devices and flawed single and double blind studies to me obfuscates the possible results and is, in this sort of treatment, a magician's trick of misdirection, as it actually focuses the attention away from total efficacy sampling when larger samples using the entire test group would have provided a more complete picture.
Nightly EKG and EEG testing is not needed, but certainly the easiest and simplest method to measure the effectiveness remains sO2sat levels over the course of a night, something each of these studies could have done. The devices are cheap and easy for the patient to use and gather the data on their computers to either e-mail in or bring in at the end of the run for evaluation, and software exists to quickly scan such results and build a picture of the entire test run, which when combined with spot checked PSG would give a better and more complete picture. As it is, each study relied on no more than a few PSGs, one before, one during and one at end of study to build their picture of the effectiveness of treatment and in some studies the odd PSG in between. Experienced CPAPers can readily attest to how incomplete such a picture would be, given the wide variance of AHI levels most CPAPers experience over the course of three months under treatment. In such a study, the simple criterion would be: desat to 88% or below = SA, stable sO2sat levels in acceptable parameters (91-98%) indicates effectiveness of treatment. There is no need to measure snore levels or sleep quality levels other than in spot checks, although snore levels are easy to monitor nightly at home. iPhones can do it these days.
So, that is it in a nutshell. Draw what conclusions you will from it. I make the opinion that it may be effective in some cases, there is no strong evidence for long term use safety or effectiveness in more severe OSA cases, and none for complex apnoea, and if you are given a choice between CPAP and EPAP, and can comply with CPAP (which is increasingly easy as machines get quieter and masks get more comfortable), choose CPAP and save EPAP for vacations. Also, consider the cost - at (at the time of Provent's original market roll-out) $75 per month, over a 5 year period it quickly overtakes and exceed CPAP in cost and was not at that time covered by insurance plans. I do not know if it is now.
(This post was last modified: 01-04-2015 08:59 PM by DocWils.)