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Centrilobular emphysema

Image : “Centrilobular emphysema” by Dr. Edwin P. Ewing, Jr.. License: Public Domain

Definition and Background of Emphysema

Emphysema is defined as an unusual enlargement of the airspace that is permanent and distal to the terminal bronchioles, which is combined with the destruction of the airspace walls, without obvious fibrosis.

Normal bronchioles and alveoli look like a cluster of grapes with each alveoli being divided by septae. However, if you have emphysema, you lose your surface area, which means you do not have an effective gas exchange; hence, your diffusing capacity of the lungs for carbon monoxide (DLCO) is reduced.


Image: “Figure A shows the location of the lungs and airways in the body. The inset image shows a detailed cross-section of the bronchioles and alveoli. Figure B shows lungs damaged by COPD. The inset image shows a detailed cross-section of the damaged bronchioles and alveolar walls.” by National Heart Lung and Blood Institute. License: Public Domain

Pathophysiology of Emphysema

The part of the acinus that is affected by destruction or permanent dilation decides the subtype of emphysema, which includes:

1. Centrilobular (proximal acinar) emphysema

Of this type, there is abnormal destruction or dilation of the respiratory bronchiole.

  • Common among chronic smokers and coal workers’ pneumoconiosis
  • The excess amount of neutrophils, due to cigarette smoking, results in the release of huge amounts of elastase into the lung parenchyma, which leads to the inability of alpha-1-antitrypsin (AAT) to maintain the integrity of the tissue.
  • There is a loss of respiratory bronchioles, mainly in the upper and middle lobes.

2. Panacinar emphysema

This type is defined as enlargement or destruction of all parts of the acinus.

  • The mutation of the normal alpha-1-antitrypsin gene (Pi) to PiZZ is one of the most common homozygous genetic mutations seen in Caucasians.
  • It can also be seen in centrilobular emphysema in smokers.

3. Paraseptal (distal acinar) emphysema

This type results in the destruction of the alveolar ducts. It usually results in spontaneous pneumothorax when patients are affected with this type alone. However, it may occur in combination with other types of emphysema.

Epidemiology of Emphysema

United States: 18 cases per 1000 persons suffer from emphysema and 34 cases per 1000 persons suffer from chronic bronchitis.

International: The prevalence of COPD stage II or higher is 10.1%.

Mortality: There are 64.3 deaths from COPD per 100,000 population in adults older than 25 years in the United States.

Gender: It used to be more prevalent among men because of smoking. However, the difference in prevalence between the two genders is decreasing.

Presentation of Emphysema

Symptoms of emphysema

Patients usually ignore their symptoms and adapt themselves to them as they start gradually and progress over the years. These symptoms include:

  • A productive cough worse in the morning with clear-to-white sputum
  • Acute chest illness
  • Dyspnea
  • Wheezing

Signs of emphysema

Observed signs may be different depending on the severity and the stage of the disease. They include:

  • Limitation of expiratory flow with relative preservation of inspiratory flow
  • Tachypnea
  • Dyspnea with mild exertion
  • Increased respiratory rate
  • Use of accessory respiratory muscles
  • Paradoxical contraction of lower intercostal spaces

    barrel chest emphysema

    Image: “A lateral CXR of a person with emphysema. Note the barrel chest and flat diaphragm.” by James Heilman, MD. License: CC BY-SA 3.0

  • Cyanosis
  • Elevated Jugular venous pressure
  • Atrophy of limb musculature
  • Peripheral edema
  • Barrel chest
  • Diffuse or focal wheezing
  • Diminished breath sounds
  • Hyper-resonance upon percussion
  • Prolonged expiration
  • Hyperinflation in chest radiograph

Causes of Emphysema

Different risk factors may increase the risk of developing emphysema, these causes and risk factors include:

Differential Diagnosis of Emphysema

Congestive heart failure: this disorder might produce wheezing and can be difficult to distinguish from emphysema. However, a history of orthopnea and paroxysmal dyspnea that is nocturnal with the existence of fine basal crackles, and typical findings on upper body radiographs, can lead to the diagnosis of congestive heart failure.

Bronchiectasis: patients with bronchiectasis have chronic production of copious sputum that is purulent, coarse crackles, and clubbing upon physical examination. Abnormal findings on upper body radiographs and CT scans will be observed.

Bronchiolitis obliterans: it is observed in younger persons who do not smoke and in persons with collagen-vascular diseases. A CT scan characteristically shows regions of mosaic attenuation without proof of generalized emphysema.

Chronic asthma: the delayed onset of severe asthma may be hard to distinguish in older patients, but the main difference is the response to bronchodilators and normal diffusion on pulmonary function tests.

Diagnosis of Emphysema

Laboratory studies

  • Arterial blood gas analysis: COPD patients have mild-to-moderate hypoxemia with no associated hypercapnia. However, hypercapnia may develop, and the
    hypoxemia worsens as the disease progresses.
  • Hematocrit: polycythemia may result from chronic hypoxemia. A hematocrit
    result in more than 47% of female and more than 52% of males indicates
  • Serum bicarbonate: serum bicarbonate levels are useful in the follow-up of the
    disease progression.
  • Serum alpha-1-antitrypsin: when the serum levels fall below the protective
    threshold value, which is 3 to 7 mmol/L, the diagnosis of alpha-1-antitrypsin
    deficiency is confirmed.
  • Sputum evaluation: the sputum is mucoid with macrophages as the
    predominant cells. The sputum becomes purulent with exacerbation and includes excessive neutrophils and a mixture of organisms visualized through Gram staining.

Imaging studies


Image: “Patient with Severe Emphysema.” by James Heilman, MD. License: CC BY-SA 3.0

Chest radiograph:

Signs of hyperinflation, such as diaphragm flattening, increased retrosternal air space, and a long narrow heart shadow will be revealed on frontal and lateral chest x- rays. Other signs of emphysema include the hyperlucency of the lungs and rapid tapering vascular shadows. If the disease was complicated with pulmonary hypertension, the hilar vascular shadows become obvious and prominent. You may also notice opacity in the lower retrosternal air space and right ventricular enlargement.

emphasema CT

Image: “Bullus emphysema as seen on CT” by James Heilman, MD. License: CC BY-SA 3.0

CT scan:

High-resolution CT scans are also used in the diagnosis of emphysema as they are more sensitive than chest x-rays. It is highly specific, and it makes bullae visible and clear, which are usually hard to see on chest x-rays. CT scans are not always done for emphysema patients; however, they are indicated for patients considered for surgical intervention.

Staging of Emphysema

COPD is divided into different stages depending on FEV1. The widely used staging system is the Global Initiative for Chronic Obstructive Lung Disease staging system, which is

  • Stage I (mild): FEV1 more than or equal to 80% of the predicted value.
  • Stage II (moderate): FEV1 more than or equal to 50% and less than 80% of the predicted value.
  • Stage III (severe): FEV1 more than or equal to 30% and less than 50% of the predicted value.
  • Stage IV (very severe): FEV1 less than 50% of the predicted value with
    chronic respiratory failure; or FEV1 less than 30% of the predicted value.

Definition of respiratory failure: PaO2 less than 60 mm Hg (kPa 8.0) or a PaCO2 higher
than 50 mm Hg (kPa 6.7).

Management of Emphysema

  • Smoking cessation: it is the most important factor in the management of COPD patients.
  • Bronchodilators: both short and long-acting bronchodilators can be used in the management of COPD, and they work by dilating airways, resulting in decreased airflow resistance.
  • Phosphodiesterase inhibitors: they work by increasing intracellular cAMP, which results in bronchodilation.
  • Anti-inflammatory therapy: inflammation is one of the important factors in the pathogenesis of COPD, therefore oral and inhaled corticosteroids are used to manage this inflammation.
  • Antibiotics: chronic infection and colonization of the lower airways by bacteria may occur in COPD patients, which require the use of antibiotics.
  • Mucolytic agents: they improve secretion clearance and reduce sputum viscosity.
  • Proton pump inhibitors: studies showed that proton pump inhibitors reduce the incidence of the common cold in patients with COPD.
  • Oxygen therapy: chronic hypoxemia may develop in COPD patients, which requires the use of oxygen therapy.

Surgical intervention

  • Bullectomy: this has been the standard procedure in selected patients for many years; it involves the removal of giant bullae.
  • Lung volume reduction surgery: in this procedure, the most diseased parts of the lung are surgically resected to decrease hyperinflation.
  • Endobronchial valve placement: it is still under investigation as a replacement for lung volume reduction surgery.
  • Lung transplantation: most people who undergo lung transplantation are COPD patients.
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