Feels Like Air Bubbles Trapped in Chest After Breast Implants

This Is perfectly normal and will disappear in the next few weeks. It is from air and fluid (irrigation, local anesthetic, serum, etc) in the pocket which will be naturally absorbed over time.

As Dr. Rand states this is extremely common immediately after surgery. However, it is not commonly present weeks after the surgery and may be considered subcutaneous emphysema which may be an indication of an adverse event

While it is not uncommon to have some air in the pockets early post-op, at four weeks I think it is a bit unusual. I would see my doctor to be evaluated.

Very common post op sequelae. Be patient for these air bubbles or crepatius   to resolve. The body will absorb it.

From MIAMI Dr. B

Normally, our bodies do not contain pockets of fresh air or fluid but surgery changes that. When we lift the tissues and separate them, we allow air to come into the spaces. With Breast Augmentation, some air is trapped in the breast at the time of closure and it is gradually absorbed by the body over the next few weeks. The interface of air, fluid and the implant may give rise to a few funny sounds until the air and fluid are absorbed. From your description, it sounds like this may be what you are dealing with. But to be sure see your surgeon and have him advise you.

It is very common to feel "rice krispies" under the skin especially below the breast after an augmentation but this is usually gone in a few days, not weeks.  Ask your doctor to check you.