Pulmonary Function Tests (PFT’s)

Flow-Volume Loop

  • Variable Extrathoracic Upper Airway Obstruction: adversely affects predominantly inspiratory flow (as inspiratory negative intraluminal pressures exacerbate the inspiratory airway narrowing, while expiratory positive intraluminal pressures splints the obstruction open)
    • Example: vocal cord paralysis -> inspiratory stridor with no expiratory obstruction
  • Variable Intrathoracic Upper Airway Obstruction: adversely affects predominantly expiratory flow (as inspiratory negative pressures decrease the inspiratory airway narrowing, while expiratory positive intrapleural pressures exacerbate the airway obstruction)
    • Example: tracheomalacia -> expiratory worsening of airway obstruction
  • Fixed Upper Airway Obstruction: adversely affects both inspiratory and expiratory flows

Spirometry

  • xxx

Lung Volumes

  • xxx

Diffusion Capacity for Carbon Monoxide (DLCO)

Increased DLCO

Etiology

  • Diffuse Alveolar Hemorrhage (DAH) (see Diffuse Alveolar Hemorrhage, [[Diffuse Alveolar Hemorrhage]])
  • Asthma (see Asthma, [[Asthma]]): due to increased pulm capillary blood volume

Decreased DLCO

Etiology


Restriction

Etiology -> P-A-I-N-T-O-P-P-M

Pleural Disease

  • Examples
  • PFT Features
    • Variable lung volumes

Alveolar Filling Process

  • Examples
  • PFT Features
    • Proportional decrease in TLC, FRC, RV, and VC

Interstitial Lung Disease (ILD)

  • Examples
  • PFT Features
    • Decreased TLC
    • Decreased FRC
    • Decreased VC
    • Small decrease in RV

Neuromuscular Disease

  • Examples
  • PFT Features
    • Decreased TLC in pure inspiratory weakness, but not in pure expiratory muscle weakness (this is one of the cases where restriction can be diagnosed in setting of a normal TLC)
    • No change in FRC in cases with both inspiratory and expiratory muscle weakness

Thoracic Cage Abnormality

  • Examples
    • Ankylosing Spondylitis (see Ankylosing Spondylitis, [[Ankylosing Spondylitis]]): due to costovertebral spondylosis
    • Ascites (see Ascites, [[Ascites]])
    • Kyphoscoliosis (see Kyphoscoliosis, [[Kyphoscoliosis]])
    • Polydermatomyositis (see Polydermatomyositis, [[Polydermatomyositis]]): extensive soft tissue chest wall calcification
    • Pregnancy (see Pregnancy, [[Pregnancy]])
    • Scleroderma (see Scleroderma, [[Scleroderma]]): skin tightness over chest may restrict thoracic cage expansion
  • PFT Features
    • Decreased TLC
    • Decrease in VC
    • Small decrease in FRC (normal-slightly increased in Ankylosing Spondylitis cases with restricted thoracic cage expansion)

Obesity

  • PFT Features
    • xxxx

Pulmonary Hypertension

  • Associated Disorders
  • PFT Features
    • Generally mild restriction

Poor Cooperation

  • PFT Features
    • xxxx

Miscellaneous

  • Beta Thalassemia Major (see Thalassemias, [[Thalassemias]]): restriction may occur (for unclear reasons)
    • Pulmonary function test (PFT) defects correct with transfusion and do not correlate with the iron burden, blood counts, or degree of hemolysis

References

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