Emotional blackmail is wrong and if your parents are using this as a way to manipulate you, don’t accept it. You are no longer that child who has to do as you are told. Help your parents out because you want to not because you feel a duty to. Your parents had a duty to care for you when you were young but it doesn’t necessarily follow that you have to return the favour when your are an adult and they are frail and vulnerable.
Your parents are responsible for themselves and any kind considerate acts you wish to engage in, should be out of the goodness of your own heart, not because the old family dynamic is at play. Parents who have brought their children up in a balanced way will tend to enjoy more from their adult children. Justice will be served in one way or another to parents who abused their position of power with their young children. A sad lesson that many parents do not learn until it is too late.