Arterial Blood Gases – Laboratory Diagnostics

by Carlo Raj, MD

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    00:00 I was just to continue through using diagnostic stools when it's relevant so that when the tools are then given to you, for example, we went through imaging and we looked at how CT and x-rays should be utilized to your advantage. And here, we'll take a look at labs and as we continue further, we'll get into more of our pulmonary function test, so on and so forth, and everything needs to make sure that when it's given to you that you use it appropriately and that you're not wasting time, precious time, trying to save your patient or trying to save your question.

    00:35 Let's begin. We begin by looking at ABG. What does that mean to you? Arterial is where you are. Stop there. Think. Conceptualize. Arterial side, what does that mean to you? Well, oxygen pO2 here approximately 100. Let's keep things simple. You have now just picked up oxygen from your lungs and you're moving through your pulmonary veins and you're moving in through the left ventricle then through the aorta and then you have a pO2 of approximately 100. Are we clear? I want to keep things simple. I want to get immediately into the aorta. Now, once you get into the aorta, that's the blood that you're going to measure here. You might be looking for your CO2. Your CO2 here will be, well you shouldn't have it being risen, because it's the oxygenated side, what is your pCO2 level? Approximately 40. Are we clear? Maybe you get bicarb. With your bicarb level approximately between 22-26, we'll be using approximately 24-25 for our learning purposes. Let's continue. Measure the pH, measure the pCO2, and measure the pO2, where? On the arterial side. When is it problematic? When the patient might have hypoxia. What is that pO2 level? Good, 60. Now there are 2 types of respiratory failure. I'll keep repeating this as well Type 1 respiratory failure much more common than type 2. In both type 1 or type 2 by definition, your patient is in a state of hypoxia. What's your pO2 on the arterial side? 60. Arterial side.

    02:10 Uses the H-H equation or the Henderson-Hasselbalch to calculate the bicarb and the reason we do this, well we try to measure the bicarb from the basic metabolic panel. So from this panel, we will then tell you how much bicarb is actually being produced through your calculation and of course this is referring to which calculation? The carbonic anhydrase calculation that we have seen in every single system just developed. The differences between the measured bicarb or calculated are sometimes referred to as being your base excess or base deficit. It all depends as to how active the actual respiratory system has been.

    About the Lecture

    The lecture Arterial Blood Gases – Laboratory Diagnostics by Carlo Raj, MD is from the course Pulmonary Diagnostics.

    Included Quiz Questions

    1. HCO3
    2. PO2
    3. PCO2
    4. pH
    5. CO
    1. 60mmHg
    2. 100mmHg
    3. 80mmHg
    4. 120mmHg
    5. 0mmHg

    Author of lecture Arterial Blood Gases – Laboratory Diagnostics

     Carlo Raj, MD

    Carlo Raj, MD

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