When a covered employee has a permanent impairment, suffers a subsequent accidental personal injury, occupational disease, or compensable hernia resulting in permanent partial or permanent total disability, and otherwise meets the requirements of this subtitle, it is the intent of this subtitle that the total compensation to which the covered employee is entitled equals the amount of compensation that would be payable for the combined effects of:

(1) the previous impairment; and

(2) the subsequent accidental personal injury, occupational disease, or compensable hernia.