Emphysema by huanghengdong

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									Emphysema: this disease is defined in anatomical terms as a condition characterized by
abnormal, permanent enlargement of the airspaces (acinus & respiratory bronchioles, or
parenchyma of the lung) beyond the terminal bronchiole, accompanied by the destruction of the
walls of the airspace (loss of the A-C membrane and parenchymal elastic structure) without
fibrosis. The absence of fibrosis and the destruction of the parenchyma mean that the lung does
not become noncompliant (stiff). Emphysema is a part of the spectrum of chronic obstructive
lung disease (COPD), and often coexists with some degree of chronic bronchitis, and/or asthma.

Pathophysiology: Emphysema is the pathologic result of three major causes (and anatomical
presentations):
    1. Cigarette smoking may account for as much as 80-90% of all COPD-related deaths
        (anatomical presentation: Centrilobular; most often in fast time-constant lung units).
    2. A genetic problem: α-antitrypsin (AAT) deficiency (anatomical presentation: Panlobular;
        dependent lung zones where there is the most blood flow).
    3. Normal aging of the lung (anatomical presentation: the apices of the lungs).

Clinical manifestations or Symptoms and Signs:
   1. Dyspnea (high work of breathing, high oxygen cost-of-breathing)
   2. Hypoxemia (related to loss of A-C membrane)
   3. Reduced diffusion capacity (DLCO) (related to loss of A-C membrane)
   4. Hyperinflation by CXR, suggesting air trapping (related to loss of A-C membrane).
   5. Reduced expiratory flow rates (FEV1, FEV1/FVC)
   6. Increased lung volumes by PFT (increased TLC, FRC, and RV).
   7. Hypercapnia is a sign of very advanced emphysema or more often when it is in
       combination with chronic bronchitis.
   8. Patients with pure emphysema (little to no chronic bronchitis) are often very thin, reddish
       complexion, using “pursed-lip breathing”; and are therefore referred to as “pink
       puffers”.(2)

Methods of diagnosis:
  1. History and Physical: “Chief Complaint” at presentation in the doctor’s office or ER is
     most often Dyspnea or Cough.
  2. Hypoxemia by SpO2 first, and then ABG.
         a. Initial interpretation is most often “acute (early) or chronic (advanced disease
             stage) respiratory alkalosis with moderate (to severe) hypoxemia”
         b. Late-stage ABG may be “acute-on-chronic respiratory failure with severe
             hypoxemia requiring moderately high FiO2’s to correct”.
  3. Pulmonary Function tests including lung volumes, flowrates, diffusion studies, and
     before-and-after bronchodilator studies.
  4. Chest Radiographs, and CT studies.

Management & Treatment:(1,2)
  1. Establish the diagnosis, monitor progress and response to treatment.
  2. Treat hypoxemia with oxygen therapy 24 hrs/day (see NOTT study), goal to keep PaO2
     >55 torr.
  3. Treat bronchospasm, follow GOLD guidelines. [See Egan’s page 509.]
   4. Maximize the patient’s functional status (keep them performing their daily activities and
      out of the hospital).
   5. Smoking cessation is key to reducing the progression of the disease.
   6. Avoid other respiratory irritants and infections; keep up on immunizations for flu.
   7. There are a limited number of patients that qualify for surgical intervention: Lung
      transplantation for selected patients, or lung reduction surgery.
   8. Inhaled steroids and antibiotics are used as needed.
   9. Exercise or rehab mostly improves the quality of life, but does not necessarily prolong
      life.

Prognosis. COPD is now the 4th leading cause of death in the US, and is a major cause of
hospitalizations and homecare costs.(1) Centrilobular emphysema usually takes decades to
become evident, so it is seen mostly in patients in their sixth or seventh decade, or sooner
depending on their smoking habits and co-morbidity issues. Panlobular (AAT) typically presents
in the fourth or fifth decade.(2) The “BODE” assessment provides interesting information
regarding the severity of the symptoms:
      B: Body mass index. As the patient looses weight their prognosis worsens.
      O: Airflow limitation (obstruction).
      B: Breathlessness (dyspnea index).
      E: Exercise capacity.

   The GOLD and BODE emphysema staging systems provide slightly different information,
summarized as follows:
    More than 80% of people with mild emphysema are alive after four years.
    60% to 70% of people with moderate emphysema are alive after four years.
    Among people with severe emphysema (FEV1< 35% normal), about 50% are alive after
       four years.
    People with the worst possible emphysema symptoms (such as inability to walk through
       the house and severe weight loss) have the shortest life expectancy.
Remember that emphysema life expectancy varies widely, even between people with the same
pulmonary function tests and BODE index scores. Even with the most severe emphysema, the
odds of surviving one year are higher than 90%. (4)

References:
   1. Dweik R. and Stoller JK. Chapter 23. Egan’s Fundamentals of Respiratory Care. 9th Ed.
       Wilkins RL, Stoller JK, Kacmarek RM. Mosby/Elsevier. 2009.
   2. Des Jardins TD, Burton GG. Clinical Manifestations & Assessment of Respiratory
       Disease. 6th Ed. Mosby/Elsevier. 2011.
   3. Wikipedia. Emphysema. Accessed Through Google: July 29, 2011.
   4. WebMD. Emphysema. Accessed Through Google: July 29, 2011.
   5. MayoClinic.com. Accessed Through Google: July 29, 2011.
   6. Cedars-Sinai.com. Accessed Through Google: July 29, 2011.
Wikipedia images accessed: July 29, 2011.




Figure 1: Lateral CXR showing         Figure 2: Computerized tomography (CT)
barrel chest also known as            showing multiple bullae. Smaller bullae are
increased anteroposterior chest       called blebs. The presence of these enlarged air
dimension. Note the depressed         spaces creates a risk of spontaneous
(flattened) diaphragm and anterior    pneumothorax.
air space (retrosternal space).




Gross section of the apical lung showing Centrilobular destruction
of the lung. (ref. 3)

								
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