pulmonary function test (PFT)

Classification

• spirometry used to assess airflow obstruction
• flow-volume loop
  • can help identify anatomy of airway obstruction
• lung volume
  • total lung capacity
  • vital capacity
  • functional residual capacity
  • expiratory reserve volume
  • residual volume
• diffusion capacity of carbon monoxide (DLCO)
  • evaluates gas transport across the alveolar membrane

Indications

• dyspnea
• classification of lung disease
  • obstructive lung disease
    • chronic obstructive lung disease
    • asthma
    • bronichiectasis
  • restrictive lung disease
  • interstitial lung disease
• assessment of lung disease severity

Contraindications

• spirometry alone is insufficient to rule out lung disease in smokers & former smokers

Clinical significance

• obstructive lung disease
  • indicated by decrease in FEV1, FEV1/FVC & FEF[25-75]
  • FEV1/FVC of < 70%
  • asthma, bronchitis, emphysema
    • residual volume increased with emphysema
  • resistance to expiratory airflow causes air trapping leading to elevated intrathoracic pressure (auto-PEEP)
• asthma
  • obstruction to airflow during inspiration & expiration
  • provocation inhalation challenge test
• reversible airway disease (asthma, bronchitis)
  • indicated by increase in flow rate (FEV1 or FVC) of > 12-20% & > 200 mL from baseline after bronchodilator therapy*
• restrictive lung disease
  • limitation of full expansion of the lungs
    • lung parenchymal disease
    • chest wall or diaphragm dysfunction
  • volumes FEV1 & FVC are similarly diminished (includes pneumonectomy)
  • total lung capacity < 80%
  • flow rates are normal
• combination of restrictive & obstructive
  • COPD; smokers may have interstitial lung changes along with emphysema
  • pulmonary fibrosis
• neuromuscular disease
  • restrictive lung disease pattern
    • vital capacity < 50% of predicted
  • decreased maximal voluntary ventilation (MVV)
    • arterial pCO2 > 45 mm Hg
  • normal flow rates
    • minimal inspiratory pressure: -60 cm H2O
    • maximal expiratory pressure: +40 cm H2O
  • DLCO is normal
• upper airway obstruction shows inspiratory abnormalities in flow loop
• no obstruction & no restriction
  • isolated low DLCO is consistent with
    • anemia
    • pulmonary embolism
    • pulmonary hypertension
  • isolated high DLCO is consistent with
    • pulmonary hemorrhage
    • obesity
    • left-to-right cardiac shunt
    • polycythemia
  • nonspecific pattern
    • normal total lung capacity
    • normal FEV1/FVC
    • low FEV1 or FVC (or both)
    • generally does not evolve into obstructive lung disease or restrictive lung disease
  • preserved ratio impaired spirometry
    • associated with increased risk for mortality & adverse cardiovascular & respiratory outcomes

* in a large cohort, bronchodilator responsiveness failed to distinguish asthma & COPD

Procedure

• spirometry is used to measure airflow
• DLCO is a measurement of gas exchange

Interpretation

• results below 80% of predicted indicate impairment
• race-based corrections not useful for predicting adverse respiratory events

More general terms

• clinical procedure

More specific terms

• cardiopulmonary exercise testing
• diffusion capacity of carbon monoxide (DLCO)
• flow-volume loop
• forced expiratory flow
• forced expiratory flow (FEF[25-75])
• forced expiratory volume in 1 second (FEV1)
• forced vital capacity (FVC)
• fraction of exhaled nitric oxide (FeNo)
• maximal voluntary ventilation (MVV)
• nitrogen washout
• peak expiratory flow rate (PEFR, PER)
• pneumogram
• preserved ratio impaired spirometry
• provocation inhalation challenge test; methacholine challenge test
• respiratory residual volume
• static lung volume
• total lung capacity (TLC)

Additional terms

• age-associated changes in pulmonary function
• dyspnea (shortness of breath {SOB})
• lung
• lung disease
• pulmonary