Very likely I will get downvotes for this but: I suspect we will find there was far less quackery in some of the eastern medicine practices than we thought.
I'm not taking a position on that question, as I haven't studied it sufficiently (though acupuncture, for example, seems more compelling that reiki).
The issue I've had with Eastern medicine along with other folk remedies is the methodology and fact that they are not truly applying the scientific method in the way Western medicine does.
That said, I would not at all be surprised to find that many things in medicine, Eastern, Western, folk medicine, etc. that were previously unproven (by Western medicine standards) suddenly start having testable, verifiable reasons for why they work.
I have read that some points of acupuncture have been shown to have the effect they claim, and how it works can be explained. Some other points have been shown to have no measurable effect. And some point have been shown to have effects, but cannot be explained.
I'd be shocked if a concept so widely believed in like that had not gone under insane scrutiny by Western practitioners.
In later and current periods of Chinese history it's usually considered to mean air or breath, but also vital energy or life force, this latter sense being the sense in which it is deployed for traditional medicinal techniques such as 'Qigong' - 氣功 （traditional) or 气功 (simplified) - which is literally '[getting positive results from] [the energy]'. However, not many people are aware that initially it was used to refer to 'sickening vapors that rise from a corpse' (an early concept for bacterial/airborne illness, a concept later repurposed in premodern Chinese medicinal thinking to describe the acquisition of malaria and similar illnesses in tropical areas).
Qi today is basically a catch-all word for energy flowing (possibly 'in a manner roughly like vapor') and could be reasonably roughly seen, from a medical perspective, to refer to the combined effect of circulatory, lymphatic and respiratory systems.
Being such a vague term, approaching it from a western perspective seems difficult. You would perhaps get further looking for western studies of the health benefits of Qigong practice.
The interaction of the CNS and the immune system has been more recently studied over the past 10 years. This field is known as neuroimmunology. The most recent and obvious clinical application of neuroimmunology are vagal nerve implants, where stimulation of the vagus nerve can help improve vagal tone and reduce inflammation. Meditation is another well known method of improving vagal tone; however, we live in a society of quick fixes.