Emphysema 1

What is Emphysema? Specifically, two things combined: Now, one thing that should be noted about Emphysema is that it is not, in itself, COPD or Chronic Obstructive Pulmonary Disorder. Emphysema is also not Chronic Bronchitis, but frequently these two diseases are present together. What is Emphysema then? It is, specifically, two things together: Permanent abnormal enlargement of the acini, which are the berry-shaped gas exchange structures found at the distal end of the bronchiole. Acinius, by the way, is Latin for berry. Destruction of the alveolar walls without obvious fibrosis. This criteria of obvious fibrosis is an important point while performing differential diagnosis between things like Emphysema and Asbestosis, another lung disease that caused by long-term heavy exposure to asbestos. In this case, the key difference here is that while Emphysema does not have obvious fibrosis, those who suffer from Asbestosis have signs of extensive interstitial scar tissue formation. Before we go any further, I’d like to mention that there are two main classifications of Emphysema, both with different etiologies or causes. Permanent abnormal enlargement of the acini (acinius, Latin for “berry”) (MedicineNet, 1999) Destruction of alveolar walls without obvious fibrosis (McCance & Huether, 2006) (as opposed to something like Asbestosis: http://en.wikipedia.org/wiki/Asbestosis) Image from www.nucleusinc.com 2

Two kinds of emphysema Primary emphysema Secondary emphysema 1-2% of cases Inherited lack of alpha-1 antitrypsin, a protective protein (inhibits neutrophil elastase) Secondary emphysema Also caused by inability to inhibit proteolytic enzymes in the lungs From inhaled toxins (e.g., cigarette smoke) 20% of smokers at risk (McCance & Huether, 2006) There are two kinds of emphysema, Primary and Secondary, and I think a brief summary of both would be useful here. McCance and Huether’s Pathophysiology text notes that the Primary type makes up 1-2% of the cases of emphysema (other sources say about 3%). This Primary Emphysema is notable in that it is caused by an inherited lack of alpha-1 antitrypsin, a protective protein which inhibits neutrophil elastase. The AlphaOne website notes that approximately 100,000 Americans have this difficiency, with McCance notes that homozygous individuals have a 70-80% chance of having this disorder. Secondary Emphysema, on the other hand, shares similarity in that similar destructive mechanisms are working, namely the decrease in inhibition of proteolytic enzymes. However, this Secondary is different in that it is caused by inhaled toxins, most commonly cigarette smoke. It is estimated that 20% of smokers are at risk from this type of emphysema, and this presentation will focus on this Secondary type. 3

Secondary Emphysema: Pathophysiology In sum, the basic pathophysiology of emphysema follows this pathway: Toxins such as cigarette smoke, cause inflammation of the acini. This causes the infiltration of neutrophils, macrophages and lymphocytes. Inflammatory cytokines that are released trigger increased protease activity, and inhibit normal antiprotease activity from antitrypsin. The end result is alveolar destruction. It should be noted that in healthy people, protease activity in the lungs is part of healthy function, repairing damage to the lungs caused by illness. However, when the balance between the proteases and the antiproteases is upset, you have a serious problem. In the presence of increased proteases, both healthy and unhealthy lung tissue is destroyed, and the elastin necessary for proper alveolar function is broken down. Toxins (smoke) cause inflammation Infiltration of neutrophils, macrophages and lymphocytes Inflammatory cytokines increase protease activity, inhibiting normal antiprotease activity (antitrypsin) Alveoli are destroyed because elastin is being broken down by proteases (McCance & Huether, 2006) 4

Acinius Normal vs. Emphysema Matt is going to go into greater detail about specific spirometric observations of patients with emphysema, but I’ll note here that a serious problem involves an increase in residual volume. It’s obvious that, with the decrease in surface area for gas exchange, there’s going to be a bit of a problem getting that CO2 out. However, another problem happens because we’ve modified the pathway for how this air flows out of the alveoli. McCance notes that because these alveolar structures are no longer intact, the air takes on significantly more turbulent, circular flow characteristics, inhibiting efficient exchange. Healthy alveoli, on the other hand, provide more efficient pathways for air to flow in and out. 5

Emphysema & Normal Alveoli Loss of septa Loss of capillary beds Hyperinflation Loss of elastic recoil & collapse of alveoli Increased residual volume Decreased diffusion (lower SA/Volume ) 6

Bullous Emphesyma “Bullae are large dilated airspaces that bulge out from beneath the pleura.” [Image and quote from http://medlib.med.utah.edu/WebPath/LUNGHTML/LUNG056.html] 7

Centriacinar (centrilobar) Emphysema Respiratory bronchioles in proximal portion of acinus are lost Alveoli distal to terminal bronchiole intact Occurs in smokers with chronic bronchitis Usually in upper lobes 8

Emphysema: Clinical Manifestations Dyspnea Wheezing is minimal Barrel chest, often thin Tachpynea with prolonged expiration Pursed lip breathing Tripod stance Hypoxemia &/or hypercapnia Chronic hypoventilation (later stage) Not much coughing with little sputum (Productive cough with infection) 9

COPD: Chronic Bronchitis & Emphysema 10

Barrel Chest: Increased Anterior/Posterior Diameter 11

Radiograph: Emphysema, Pulmonary hypertension, Cardiomegaly Flattened diaphragm Hyperinflation Translucency of lung Hypertrophy of heart (Hypoxia/ hypercapnea & damage = pulmonary vasoconstriction & hypertension. Later cor pulmonale) 12

Clubbing of the Nails A sign of chronic hypoxia 13

FEV1/VC normally greater than 75% Normal Spirograph FEV1/VC normally greater than 75% (per Walters presentation) Emphysema Spirograph Decreased FEV1/VC Total Lung Capacity normal or increased RV increased 14