This problem is not going to be solved by just 1 medicine. This is a long standing Asthma which is now behaving like mild lungs failure and rise in BP of lungs due to low 50/60 oxygen saturation.
Next Steps
Please revisit your Chest Specialist and ask for BiPAP machine for use at home along with other routine medicines. Oxygen is just for support of failing lungs. But, to modify disease you require a BiPAP. Rent it for 1 month to see results and comfort and then decide to purchase.
Health Tips
Till then continue medicines as advised.