I’ve been trying to figure out how to explain this concept for the better part of a week now, and I’m still not sure I will do a great job without some sort of visual reference – but I’ll give it a go.
One of the things my preceptors have been stressing during my rides is maintaining a high index of suspicion on all calls so you don’t miss an important finding. Maintaining that level of suspicion is often difficult for me, as I said in an earlier post, I am pretty comfortable with the “sick/not sick” decision – by no means is it flawless and by no means 100% accurate – I don’t pretend to know everything… in fact the further I proceed into school the more I realize how little I actually do know.
I had forgotten how as a student you need to verbalize things positive and negative, suspected and not in order to allow your preceptors inside your thought process. I often forget to verbalize things I don’t suspect even though they can’t be ruled out.
Two of the most classic differentials that can’t be ruled out on the ambulance and have such varied presentations they are on almost every list of complaints – MI and PE.
After failing to verbalize them for complaints where I didn’t suspect them, the preceptor explained a concept to me I thought I would pass along – its called Webbing. Named for the medic that came up with it (by him of course), but also something the finished product vaguely represents.
Mastery of this process takes considerable time, especially when you first try one, as you are looking all kinds of stuff up in the textbooks – but after doing a few you can do them in your head.
To start your “web” take a fresh sheet of paper and in the center of it write down a chief complaint – lets say Shortness of Breath. Now think about some of the differential diagnosis you might arrive at that cause SOB and list those in a circle around the CC. It was suggested that we try to find at least 6 – of course you could add as many differentials around that initial CC as you want. In listing those 6 differentials it is important to think of what differentials would be the most life altering for the patient, especially if they were unrecognized.
Here’s where the thinking and reference materials come in – once you have those 6 differentials listed – draw three lines off of each one – the first line is for symptoms – what do you expect your patient to complain of, how do you expect them to answer relevant questions, what kind of history or medications do you expect. If possible try to include things that can help you narrow down your list – for instance the onset of a PE and the onset of pneumonia are typically very different – the answer to your interview questions may help you narrow down your list.
The second line is for signs – what do you expect to find in a typical presentation of that differential – what type of vitals, what are your “machines that go bing” going to say – what type of physical findings are you expecting
The third line is for treatment – how do you need to treat the patient for that differential in order to improve their outcome the most.
Now that you have your foundation laid… you start using the lists to “rule things out” or perhaps the “better, more accurate” way to say that is – make things fall into the less likely to be the problem with my patient though I can’t rule it out category.
As you conduct your physical exam and interview you can mentally cross things off the list to help you find the likelihood of your differential being on the right track
Sudden onset vs gradual, clear lung sounds vs Rhonchi, tenderness and redness in a calf vs none – these things all help you narrow down what you think is wrong and base your treatment decisions on.
You will ultimately be left with a few causes you can’t say are ruled out and maybe one you are fairly sure of – here is where that treatment list comes in – for SOB – MI and PE are two of things you can’t “rule out”
IF those are the problem – how will your intended treatment affect those?
Wheezes… are they cardiac in nature or pulmonary – does it matter ?
Will Albuterol and Atrovent exacerbate the problem or make it better ?
It is a complex process and definitely NOT something you could do on an actual call – but perhaps those times when you are posted under the shade tree “borrowing” WIFI from the hotel across the parking lot…. you might try to work through some of these exercises and see if they help you focus your exams and maintain your level of suspicion – you never know, you might find with practice you can do it mentally and quickly and use the process on those calls when you just aren’t sure what the problem with your patient is.
I hope someone finds it helpful – it seems to be working for me so far.