CBE

So, My professor for fundamentals said that charting by exception means recording or documenting unusual circumstance or finding(s) per patient. I want to understand why this is a charting procedure? what's the importance of it? And based on other charting methods such as focus or soap, the pt's impairment is recorded which will also include an unusual co morbid factor or problem. So please, someone explain to me why this charting is necessary? and if it is necessary is what exact condition is it used please.

Thanks in advance