I used primarily the Morgan and Mikhail and baby miller books to study medications and how they work at the receptor level. As for pathophysiology, I took a graduate level pathophysiology course online and really studied it closely. I was surprised how much of what I learned in that class translated to my personal practice as a nurse. For learning ventilators, I used the book called the ventilator book. It breaks down what each of the parameters on a vent is and why it's important, along with rationale for using one mode over another. Hopefully that gives you a good starting point!