Hyperinflation Overview

  • Hyperinflation, specifically emphysema, entails the destruction of airways distal to the terminal bronchioles, resulting in the lungs being overly filled with air.

Radiographic Findings of Hyperinflation

  • Flattening of Hemidiaphragms: The hemidiaphragms appear flattened in hyperinflation due to excessive lung volume.
  • Enlarged Retrosternal Airspace: Increased air volume creates a larger space behind the sternum.
  • Increased Anterior-Posterior (AP) Diameter: This is most evident in lateral radiographs; the chest diameter appears larger than normal.
  • Small Heart Appearance: The heart appears small in hyperinflated lungs due to the large volume of air in the thoracic cavity.
  • Hyperlucency: Areas of excessive blackness on radiographs indicate an abnormally high volume of air.

CT Findings

  • Increased Sensitivity of CT: CT scans can reveal low-density areas in the lungs that may not show up on standard radiographs. These areas often lack normal interstitial walls.

Comparison of Hyperinflated vs. Normal Lungs

  • Diaphragm Shape:
    • Hyperinflated lungs exhibit significantly flatter diaphragms compared to normal lungs.
  • Size of Lungs: Hyperinflated lungs appear larger on radiographs,
  • Thorax Diameter: Lateral views show notable diameter increase in hyperinflated cases; prominence of the aorta and heart apex can also be observed.

Types of Emphysema

  • Centrilobular Emphysema

    • Causes: Primarily caused by cigarette smoking.
    • Affected Regions: Predominantly affects upper lobes within the lungs; leads to centrally positioned lucencies.

  • Paraseptal Emphysema

    • Association: Also linked to cigarette smoking but is the least common type.
    • Locate: Causes peripherally located lucencies that can form bullae, possibly leading to pneumothorax.

  • Panlobular Emphysema

    • Causes: Often associated with alpha-one antitrypsin deficiency.
    • Findings: CT images show diffuse areas of low density throughout the lungs without identifiable normal lung regions.

Bulla and Blebs

  • Definitions:
    • Bulla: Large air-filled spaces (>1 cm). Typically located subpleurally and can be mistaken for pneumothorax due to their lucent nature on radiographs.
    • Blebs: Smaller (typically <1 cm), found along the visceral pleura; they can also lead to pneumothorax.
  • Difference:
    • Bullae indicate the destruction of alveoli, whereas blebs represent intact alveolar structures with air-filled spaces.

Summary of Common Emphysema Findings

  • Recognition of these findings on chest radiographs is vital for understanding and diagnosing emphysema effectively. Further study will encompass more radiographic examples to solidify this foundation.