There's three areas that I'm aware of. Certificates of Need, which some states require before you can offer certain services (like MRI/CT scanning). Supply contracts, where a hospital has a pre-set price for consumables like IV solutions, scalpels, and bandages with a supplier. And advertising.
The Certificate reduces competition because they impose geographical exclusivity. If you want to buy a MRI machine for your clinic, you cannot if the state determines if your area already has enough of them. And if you file a Certificate with the state intending to buy one, your nearby competitors are likely to place objections to your purchase. This is because the machines are expensive and the other clinics want to ensure their investment gets paid for. But this process also ensures they're expensive because the machines aren't able to be built in volumes large enough to result in a cost reduction.
The supply contracts make things easier for the hospital, as they only have to deal with one supplier for an item or class of item. The price is known up front for the duration of the contract. But this also means that the hospital cannot change suppliers if another one has a lower price for the same item midway through the contract period, reducing competition. They also restrict choice by the doctors at the hospital - doctors have strong preferences for items like gloves because of sizing & fit, and the way they transmit feeling through them (thinness, texture, etc). If a hospital changes suppliers to one that doesn't carry their favorite glove, they aren't able to perform as well. And they can't bring their own into the operating room because of liability.
I don't know how many advertisements you see in Chile for medicine, but here in the US I would guess that a quarter of advertisements on TV are for them. All those ads cost a lot of money, and they're not being targeted at doctors, but patients: "Ask your doctor if {brand} is right for you"