Winter's formula is an equation used to calculate a patient's expected partial pressure of carbon dioxide based on their arterial blood gas results the formula is used to evaluate respiratory compensation in response to metabolic acidosis in this video we're going to break down Winter's formula in a way that's easy to learn and understand as we will walk you through each part of the equation so that you'll learn exactly what each parameter means not to mention we included step-by-step examples with real patient data to show you exactly how to use Winter's formula so if you're ready let's get into it as previously mentioned Winter's formula is used to calculate a patient's predicted pac2 based on their ABG results the formula uses the following equation expected pac2 is equal to 1.5 * the bicarb Plus 8 plus or minus 2 the patient's bicarbonate value is obtained by collecting and analyzing a sample of arterial blood then you can use Winter's formula to determine the expected P2 simply by inserting the bicarb value into the equation now let's talk about how to use Winter's formula as I said you can estimate a patient's pac2 simply by inserting the measured B carb value into the equation then you can compare the estimated pac2 value to the patient's actual measured pac2 this can result in three possible scenarios the measured pac2 is equal to the estimated pac2 or the measured pac2 is greater than or less than the estimated pac2 now let's talk more about each type first let's discuss if the measured value is equal to the estimated value if the patient's P2 is within the expected P2 range it indicates that respiratory compensation is taking place this is considered to be pure metabolic acidosis however if the patient's pac2 is not within the expected range it means that a mixed disorder is present next up let's talk about when the measured P2 is greater than the estimated value if the patient measure measured value is greater than the estimated P2 it indicates that the patient has respiratory acidosis in addition to metabolic acidosis this is because the patient's respiratory system is not compensating enough for metabolic acidosis resulting in an increased P2 and the final possibility is when the measured value is less than the estimated value if the patient's measured pac2 is less than the estimated P2 it indicates that the patient has respiratory alkalosis in addition to metabolic acidosis I know this could be confusing but this occurs because the patient's respiratory system is overcompensating for metabolic acidosis resulting in a decreased P2 now we need to go into more detail about the parts of Winter's formula equation in other words let's take a closer look at each part of the equation to better understand how to use this formula again the formula is as follows expected P2 is equal to 1.5 * the bicarb + 8 plus orus 2 as you can see the equation includes the following parts the expected P2 bicarb 1.5 constant the eight constant and the plus or minus 2 constant first let's discuss the expected pac2 as previously mentioned pac2 stands for partial pressure of carbon dioxide in arterial blood this represents how much CO2 is dissolved in the blood and how well the lungs are exchanging gases the primary purpose of Winter's formula is to calculate the patient's expected pac2 this is helpful because it allows you to see if respiratory compensation is taking place if the patient's actual P2 is is within the expected range it means that respiratory compensation is working as it should next up is H3 which stands for bicarbonate or bicarb for short this is a measure of the acid base balance in the blood and is measured by collecting and analyzing an arterial blood gas sample from the patient the byar value is the only piece of information needed to calculate the expected pac2 using Winter's formul next up is the 1.5 constant which is a fixed value in the equation that does not change it is multiplied by the bicarb value in order to help calculate the expected P2 range and then there is the eight constant this is another fixed value in the equation that does not change after the byar value has been multiplied by 1.5 the eight constant is added to help calculate the expected pac2 and finally we have the plus or minus 2 constant which in the equation represents the standard deviation of the expected pac2 therefore the expected pac2 range is plus or minus two from the result calculated with Winter's formula if the measured P2 is within the range it confirms respiratory compensation and pure metabolic acidosis which leads to the next topic the types of acid-based disorder orders there are actually four different types including metabolic acidosis metabolic alkalosis respiratory acidosis and respiratory alkalosis each type of disorder is caused by a different problem for example metabolic disorders are caused by an imbalance in the body's ability to maintain proper pH levels respiratory disorders on the other hand occur when the lungs remove too much or too little CO2 due to problems with ventilation now let's talk a bit more about each type first we have metabolic acidosis which is a condition where the blood pH is decreased the pH CO2 is normal and the bicarb is also decreased this occurs when the body produces too much acid or when the kidneys are not able to remove enough acid from the blood when metabolic acidosis is present it forces the lungs to work harder to Exhale more Co 2 this helps to offset the acidosis in order to bring the pH back within the normal range which is known as respiratory compensation next we have metabolic alkalosis which is a condition where the blood pH is increased the P2 is normal and the bicarb is also increased this occurs when there is an excess of bicarbonate in the blood some of the most common causes of metabolic alkalosis include a loss of stomach acid diuretic medications and hypokalemia next up is respiratory alkalosis it's a condition where the blood pH is increased pH CO2 is decreased and the bicarb is normal this occurs when there is too much CO2 being removed from the blood by the lungs respiratory alkalosis is caused by hyperventilation which occurs due to factors such as anxiety pain or fever and finally we have respiratory acidosis which is a condition where the blood pH is decreased the pH CO2 is increased and the bicarb is normal this occurs when there is too little CO2 being removed from the blood by the lungs respiratory acidosis is caused by hypoventilation which occurs due to factors such as lung disorders obesity and sleep apnea I touched on this earlier but now let's talk more about respiratory compens ation respiratory compensation is the body's way of trying to maintain a normal pH level when a metabolic acid based disorder is present in order to do this the lungs will either remove more CO2 from the blood in the case of metabolic acidosis or less CO2 from the blood in the case of metabolic alkalosis this helps to offset the acid base imbalance and bring the pH level back into the normal range so now that you know the basics let's go through a few examples this is helpful because one of the most effective ways to learn how to use Winter's formula is to practice inserting patient data into the equation so let's say a patient has the following ABG results pH of 7.34 pH CO2 of 28 and a bicarb of 14 the pH is slightly decreased and Falls outside of the normal range the PA CO2 and bard are both decreased as well therefore this ABG can be interpreted as partially compensated metabolic acidosis in other words the patient has a metabolic issue which is causing the lungs to work harder in order to compensate and raise the ph back to normal now let's calculate the expected P2 using Winter's formula again the formula is expected pac2 is equal to 1.5 5 * the B carb + 8 plus or - 2 now we can simply plug the numbers in which would look like this expected P2 is equal to 1.5 * 14 + 8 plus or- 2 which is 29 plus or minus 2 therefore the patient's expected pac2 range should be between 27 and 31 as you can see the patient's measured pac2 of 28 Falls Within in the expected range therefore by using Winter's formula you can confirm that this patient has pure metabolic acidosis with appropriate respiratory compensation and no primary lung disorders are you still with me if so let's go through another example let's say a patient has the following ABG results pH of 7.3 P2 of 43 and a bicarb of 18 as you can see the pH is decreased and outside of the normal range the PH2 is normal while the bicarb is also decreased therefore this ABG can be interpreted as acute or uncompensated metabolic acidosis in other words the patient has a metabolic issue but the lungs have not yet had a chance to compensate and raise the ph back to normal now let's calculate the expected p CO2 using Winter's formula when we plug the numbers in it looks like this expected P2 is equal to 1.5 * 18 + 8+ or - 2 which gets you to 35 + or - 2 therefore the patient's expected pac2 range should be between 33 and 37 and this case the patient's measured pac2 of 42 is higher than the expected PA a CO2 range as previously mentioned this indicates that the patient has primary respiratory acidosis in addition to metabolic acidosis okay fine you taught me into it let's go through one more example let's say a patient has the following ABG results pH of 7.32 P2 of 27 and a bicarb of 16 again the pH is low and outside of the normal range while the pac2 and bicarb are both decreased this ABG can be interpreted as partially compensated metabolic acidosis now let's calculate the expected P2 using Winter's formula so when we plug the numbers in the expected pac2 is equal to 1.5 * 16 + 8 plus orus 2 which gets you to 32 plus orus 2 therefore this patient's expected P2 range should be between 30 and 34 in this case the patient's measured pac2 of 27 is lower than the expected P2 range this indicates that the patient has primary respiratory alkalosis in addition to metabolic acidosis I know this can be confusing but hopefully this has helped you develop a better understanding of Winter's formula and how it can be used to calculate a patient's expected p a O2 if you want to support the channel be sure to like And subscribe I would greatly appreciate it and there should be some other helpful videos popping up on your screen right about now that I think you will enjoy just a quick reminder we are not doctors this video is for informational purposes only thank you so much for watching have a blessed day and as always bre easy my friend