this video will include an introduction to winters formula as well as one example of it being used which is formulas used in times of metabolic acidosis which is to refresh your memory is when the arterial pH is less than seven point three five and the arterial bicarbonate level is less than twenty two million quids per litre some of these values may vary depend on what institution working with but for the purposes of this video these are the values we'll be using now the purpose of winters formula is to determine the answer this question is the respiratory system properly compensating for the ongoing metabolic acidosis so normally we have a metabolic acidosis meaning you have too much acid or the pH is too low in your blood stream your respiratory system tries to blow off carbon dioxide thus lowering the acidity when this formula is this the expected partial pressure of carbon dioxide in the bloodstream should be within the range of one point five times the bicarbonate level plus eight and this gives you a range plus or minus two so whatever numbers this formula spits out you want to add or subtract two from that to give you a range and it's also important lease for this video's sake that we will be using values given from arterial blood grass not the venous blood gas should be a bit different so as we want an example we have a patient who has been experiencing diarrhea and thus their bicarbonate levels are low I listed up at the top here a low bicarbonate an acidic pH and with the patient's actual or from the arterial blood gas partial pressure of co2 here we use winters formula to determine the expected range of what that co2 should be if it's properly compensated so you can see I input the 14 for the bicarbonate level here into the equation the expected partial pressure of carbon dioxide is 1.5 times 14 plus 8 plus or minus 2 that simplified is 29 plus or minus 2 or gives us a range of 27 to 31 now you can clearly see that our actual co2 is not within that range and then down here I summarize that the actual pco2 of 20 is not in the range which means that there's improper compensation or the respiratory system is not properly compensating for the ongoing metabolic acidosis caused by that diarrhea now what can be going on if you have improper compensation it could be a lot of different things but basically there's some other ongoing process besides just that initial insult of diarrhea causing the metabolic acidosis if the partial pressure of carbon dioxide is below the range which is in our case you have an ongoing primary respiratory alkalosis so you have a metabolic acidosis and a respiratory alkalosis this can be caused by a lot of different things the patient can be really jacked up we're really excited or really nervous or really worried thus causing the hyperventilate a bit which will bring that co2 level down that could be on different kinds of drugs have a fever or that could be climate izing to a higher altitude and then conversely if the partial pressure of co2 is above the range which was not the our case you would have two types of acidosis occurring metabolic from the diarrhea and a respiratory from one of these causes or several other and that is an instruction to winters form