Hi, I had gone through your query and understand your concerns.
I would like to know whether your mother was receiving morphine throughout. in cases of sleep apnea, respiratory depression that can cause accumulation of Carbondioxide in the body causing secondary
cardiac arrest owing to hypoxia(lack of oxygen in the body).
another possibility, may be fat embolism in the
pulmonary artery , but, this usually occurs in fracture of long bones.
in cases of prolonged period of immobilization, swelling of the legs due to
deep vein thrombosis may also lead to
pulmonary embolism. but, in cases of pulmonary embolism, a patient will have profound breathing difficulty and will collapse(
cardiogenic shock) before dying.
all these are possibilities. other drugs like Metoprolol 50 mg, ibuprofen 800mg, & amatodine should not be responsible for sudden cardiac arrest.only an autopsy could have confirmed the actual cause of death.