She is overly controlling of him and his response is smoke. Mom is basically in bed most of the day, getting up for a short time to cook or eat. She takes anxiety medication daily. Dad has COPD and uses a Nebulizer no oxygen yet because he still smokes and they wouldn't suggest bring the tanks that can explode into the house. Constantly bickering.
Unfortunately, I don't have a solution for you any more than I had a solution for my own situation years ago. I would call my mom during the brief time frame I knew she'd be out of bed and I would go and visit my dad and he'd be sitting at the kitchen table with his book while my mom was in bed.
I begged my mom to get out of bed because I knew how detrimental to her health it was to lay in bed all day but short of dragging her out myself there was nothing I could do about it. My dad didn't want to go up against her either.
I never could understand how they had reached the point they were at. These were the same parents who took us on vacations and gave us a wonderful family in which to grow up.
There wasn't much I could do about their situation if they weren't willing to change and maybe they didn't know how to change, I don't know. Or maybe making a change seemed to difficult for them. The elderly couple they evolved into were not the same people they once were. I'm sure they weren't happy but I think they were powerless to change.
All I can suggest is that you try to convince your mom to stay out of bed but if she refuses don't make yourself crazy over it like I did. It did no good and just got me so stressed out that I thought I was having a heart attack one evening.
Your dad knows smoking is bad for him and will exacerbate his COPD, maybe he just doesn't care at this point. Don't nag him about it. Again, it will do no good and will only serve to frustrate you.
The patterns and routines your parents are exhibiting have been years, even decades, in the making. All you can do at this point is change how you approach it. You shouldn't be working harder than them on changing their behavior. We can't change the behavior of others. Your parents would have to want to change and if they don't want to change work on accepting that.
I think that when you visit, make an announcement One Time, right when you arrive, something like "I hope you 2 aren't going to bicker the whole time I'm here, or I'm going to have to leave, I'm here for a nice visit and cant handle the stress right now" and leave it at that and then Do Leave, if they start up! This way, it takes the focus off of them, and they MAY come to the realization that you too, have other things going on in YOUR life, and it isn't always about them!
I know that my husband and I bicker when there is tension in the house, but not in front of others! Its often what long term couples do, unfortunately! 31 years and counting, I Love him, but sometimes I want to kill him, Lol!