Hierarchy, being a chain of command in which an individual above, privvy to more information, gives you instructions to follow. This includes military organizations, but is just as applicable to a doctor-patient relationship.
Coercion, meaning the threat of retaliation, through physical force, revoking of freedoms or privileges, or denial of resources.
Voluntary, meaning of one’s own means, with no coercion or realization of coercion, with the clear option to opt out being present whenever possible.
This does not leave things in question, I believe. Currently, we all operate within hierarchies at work with explicit threats of destitution being held over our heads, through the denial of currency. Meanwhile, there is no coercion from your physician despite it still being hierarchical in nature, because the hierarchy is entirely based on trust and is voluntary.