Hello Lucy,
The verapamil at 160 is too low to have much beneficial effect...at least as reported here over the years. The sweet spot seems to be 480 mg/dy in divided doses...immediate release type vs extended release. Some...like myself, went WAY higher...to over 1000 mg/dy. Also had some success timing doses to expected hit times. When stepping up the dosage it should be in stages and an initial ECG taken then compared to later ECG's at higher doses (verapamil can effect heart rate....which is reversible upon discontinuation.) If you do increase dosage...be sure to eat lots of fiber and mucho water (which is a good idea anyway) as it can be constipating ....
Good on reducing the pred...you really should eliminate entirely...the long term effects are nasty squared. It is intended....in typical protocol...to break a cycle with a 2 week taper...while the verapamil takes effect....
A Doctor that would insist on O2 seems to have it together...many of us had to FIGHT with ours to get an O2 script....lots of wailing and gnashing of teeth...and firing of incompetents. Which causes me puzzlement re the continued pred AND the LOW verapamil....that's not standard. Perhaps your overall health or blood pressure preclude?
Have you read the Oxygen thread on the left of the screen (yellow highlight) Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

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I used to get hit 8 times per night (once per hr). Had best results by setting up O2 rig right next to bed....one turn of the regulator and slap on(what I hope you have) the clustermask available here (a Godsend). Lights OFF, eyes CLOSED, no thoughts other than BREATH...slow and deeply and rhythmically...no anger or thrashing or swearing...remained as close to still asleep as possible. When the hit was over (usually only 5-10 min to abort) I could be back to sleep in seconds. On the way to work instead of anger at lost sleep would rejoice in the 4-6 hrs I got (previously much less than that).
This is one of the crueler aspects of CH....sorry you have to go through it.............
and you should consider the vitamin D3 regimen. (I will try to attach link later)
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

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it's a bit intimidating...start at the end and work your way back...hoping batch or someone will direct you to a more user friendly thread....
Best
Jon