My Mother COPD patient- last 3 years. Under Oxygen therapy at home. Earlier she was told to use bipap at night due to increased Co2 retention but due to positive reports regarding Co2 (37) from last 7 months shes not using that under doctor's guidance. Since it is difficult for her to move out, can she go for VBG test instead of ABG as VBG can be done at home whereas ABG needs visit nearby lab or hospital.