This is actually a very nice example of the importance of grammar. A typical novice English learner, even if they can look up all the words from the dictionary

This is actually a very nice example of the importance of grammar. A typical novice English learner, even if they can look up all the words from the dictionary, would go on like this: "Hmm, Jacuzzis is clearly a noun, so it must be the subject. So Jacuzzis found "effective"... wait, that doesn't make sense. "Effective" is not a company, how does one found "effective"? Oh, it must be the past tense of "find". OK, so these Jacuzzis found... effective? How does one find "effective"? And why was effective hiding in "treating phlebitis"? OK, whatever, maybe I could decipher this if I understand "treating phlebitis"... So it is a kind of disease that is... treating someone (or something)? How could a disease treat anyone? This sentence makes no sense!!" If you think "Duh, that's ridiculous, nobody thinks like that", then you obviously never met a struggling English learner.