Pulmonary Clinical Anatomy: Respiratory Zone

by Carlo Raj, MD

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    00:01 Let's continue forward. As you move forward and get into our respiratory zone, and as we move forward here, you have less cilia. That is not necessary because now the conducting zone, hopefully has done its job properly as it gotten rid of those antigens and such and gone it is, but now, down here, we start getting our true air and as we go through this, I would like to point out a few things physiologically. You have heard of dead space, haven’t you? Yes. Well, dead space, what does that mean to you? It means that it is air that is getting into the divisions or the bronchial tree and however, it does'nt participate in gas exchange. Now, we will only talk about dead space where it is relevant to us in pathology, but it is imperative that from physiology that you have understood the definition of dead space. For example, if it is anatomical dead space, there are anatomical holes, I shouldn’t say holes, but there are anatomical existence or anatomical type of crevices that exist in which it accumulates the air as one is breathing in. But, guess what? That air that gets anatomically trapped, maybe up in the respiratory zone, will not participate in gas exchange because it does not make it into the alveoli. So, what I wish for you to do is clearly see the picture of an alveolar sac, air coming in, but then, it gets trapped anatomically. You don’t have to know exactly where those spots are. Well, if it gets trapped, guess what? That air is not going to participate in gas exchange because it didn’t make it down into the alveoli. Now, something else that we will do, as we move forward, very much go through our alveolar gas formula. It's important that you understand what is known as A-A gradient clinically, as we move forward.

    01:50 Now, the last little portion here distally, we will go into more detail and a couple of things that I wish to point out here that students tend to get confused, but you will be clear after our discussion. Infections, in blue, once again.

    02:02 First, I would like to point out number 4 which is your typical pneumonia and by typical pneumonia, yes, there is going to productive cough. There is going to be quite a bit of fever and that productive cough is then going to show you maybe different types of sputum.

    02:13 May be it's rust colored and by that, we mean that there is blood-tinged type of sputum. Maybe it's yellow or golden, that to you, may be, indicates staph aureus. Maybe it's green and we talked about pseudomonas and pyocyanine, get my point. Or maybe it's mucoid, very mucoid and what was the type of pneumonia that is quite common in elderly and also in alcoholics? That was Klebsiella pneumonia. So, keep that in mind as we go through typical pneumonia in which the fevers are quite high. You expect the sputum to be quite productive. Isn’t that typical? Of course, it is and then maybe perhaps you bring in issues such as lobar consolidation or broncho. Both of those will be typical. Is that clear? Now, you will notice with number 4 and I wish to point out this to you, otherwise you might get confused. This will be involvement of the alveoli. So therefore, the type of sputum that you are going to then aspirate is going to be alveolar, isn’t it? The alveolar type of sputum so that you can definitely be able to culture that organism versus number 3.

    03:19 Number 3 in blue here represents a pneumonia, but this is atypical pneumonia. What does that mean? Take a look at the name here. The description is interstitial organisms. Understand the significance of that. Is the interstitium the alveoli? No. The interstitium, it’s outside the alveoli by definition. So, what is the most common type of organism that is going to cause disease of the interstitium but most likely would spare your alveoli? Good. Mycoplasma pneumonia. It's the most common type of atypical pneumonia. Why do we say atypical? That number 3 represents pneumonia of the interstitium, not the alveoli. It is outside of it. Number 1.

    04:04 Number 2, we say atypical because the patient’s fever is not going to be high. It will be a low-grade fever. Is that understood? Number 3, on chest x-ray, if we have interstitium of the lung that's affected, do you think that you might find markings on x-ray, chest x-ray? Sure, you will. So, this is called what on chest x-ray? Reticuloid nodules or reticular pattern.

    04:28 What does reticular mean? It means mesh work. So literally interstitial, you are going to find all this mesh work. So therefore, the chest x-ray and its findings is going to be far worse than what the actual patient is feeling. We call this what kind of pneumonia? Atypical. Now, if the same type of chest x-ray or image, instead of an x-ray, you were doing a CT. On CT, well that reticular pattern that you would refer to is now called what? Ground glass, type appearance. Think about what ground glass looks like? It looks rather opaque-ish, doesn’t it? What is this? Atypical pneumonia. We will be spending time with this.

    05:04 There is number 3 and number 4. Make sure you understand the significance of typical, number 4. Number 3, atypical. Remember the diseases.

    05:14 Here, way down in the distal portion, what zone are we in now? The respiratory zone.

    05:18 Involvement in gas exchange. Emphysema. With emphysema, there will be a lot to talk about.

    05:24 Here once again, I recommend that you go back and take a look at pulmonary physiology so that you are completely clear about what sea level ambient air is in terms of pressure, barometric is 760 mmHg. When you get this air into the trachea, it is going to then get humidified. That value is 47. Are we clear? So, 760 minus 47, then what do you do? Anywhere that you are on planet Earth, I don’t care if it is sea level and I don’t care if you are at Mount Everest, the oxygen concentration, your fractional oxygen on planet earth is how much? 0.21. Now, for simplicity purposes, say that you have taken an exam, taken your boards and what not. Then you can use 0, you will be perfectly fine. What is 0.2 mean to you in terms of percentage? It means 20%. I said planet Earth. What about planet hospital? Well, planet hospital depends. So in a hospital, they can change it, because we as human beings, love to manipulate things. And so therefore, you are manipulating the oxygen that you are receiving and instead of 20% or may be your patient requires 40%, requires maybe even 100%. So, please do not use 0, maybe use 0.4 representing 40% or 100% would be 1.0.

    06:43 Are we clear? I am just going to take as far as that right now, but as I said, this is all learnt in physiology. It would behoove you to make sure that you are comfortable with the material before moving in, especially when I start getting into A-A gradient. That's the second time, that I have made such a reference. Now, we have adenocarcinoma here, number 5.

    07:03 Now, adenocarcinoma is rather interesting. First and foremost, does'nt have to be a non-smoker. And its preponderance could also be found in females, scary. Number 1 since 1980's in the United States as being the number 1 lung cancer. Is squamous and small up there? They are up there, but understand, number 1 is adenocarcinoma. So, we will walk through adenocarcinoma in great detail. Don’t you worry.

    07:29 Next, adenocarcinoma, also on chest x-ray, becomes important to us because we then refer to this being peripheral. All these come under what kind of lung cancer? Bronchogenic type of lung cancer. Obviously, we did not refer to a bronchial carcinoid because that is non-bronchogenic and we do not refer to a mesothelioma because that is non-bronchogeneic.

    About the Lecture

    The lecture Pulmonary Clinical Anatomy: Respiratory Zone by Carlo Raj, MD is from the course Introduction to Pulmonary Pathology.

    Included Quiz Questions

    1. Areas of the pulmonary tree that are ventilated, but not perfused
    2. A pathologic area of the lung where perfusion occurs without ventilation
    3. Areas of air trapping in the pulmonary tree
    4. Areas of ischemic necrosis that can no longer participate in gas exchange
    5. Areas of thickened, fibrotic membranes in the lung that no longer expand
    1. H. influenzae
    2. Respiratory syncytial virus
    3. M. pneumoniae
    4. L. pneumophila
    5. C. pneumoniae
    1. M. pneumoniae
    2. L. pneumophila
    3. C. pneumoniae
    4. Respiratory syncytial virus
    5. S. aureus
    1. Ground glass opacity
    2. Coin lesion
    3. Lobar infiltrates
    4. Air-fluid level
    5. Hilar lymphadenopathy
    1. Requires a previous diagnosis of emphysema
    2. Seen peripherally on chest x-ray
    3. Most common lung cancer
    4. Commonly seen in non-smokers
    5. Occurs in the ventilated portion of the pulmonary tree

    Author of lecture Pulmonary Clinical Anatomy: Respiratory Zone

     Carlo Raj, MD

    Carlo Raj, MD

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