Respiratory Overview

15/05/2013 by admin | Respiratory

Respiratory function tests

Test Use
Peak Expiratory Flow Rate – ranges:

  1. o Male 440-670L/min
  2. o Female 300-460L/min


Monitoring changes in airflow limitation in asthma (diurnal change) – COPD fixed obstruction.
Spirometry: FEV, FVC, FEV1/FVC Assessment of airflow limitation (constrictive/restrictive). The gold standard.
Flow-volume curves Assessment of flow at lower lung volumes.

Detection of large airway obstruction both intra and extrathoracic

Airways resistance Assessment of airflow limitation
Lung volumes Differentiation between restrictive and obstructive lung disease
Gas transfer Assessment and monitoring of extent of interstitial lung disease and emphysema
Blood gases (ABGs) Assessment of respiratory failure
Pulse oximetry Postoperative, sleep studies and respiratory failure
Exercise tests Practical assessment for disability and effects of therapy
Cardiorespiratory assessment Early detection of lung/heart disease. Fitness assessment.


Typical picture:

Obstructive disease:

  1. o FEV1 reduced: <80% = mild, 50-79% = moderate, 30-49% = severe, <30% = RF!
  2. o FVC raised (due to raised TLC and RV)
  3. o FEV1/FVC will be reduced (~70% of normal) = COPD


Restrictive disease:

  1. o FEV1 reduced
  2. o FVC reduced (TLC <80% and reduced RV)
  3. o Therefore – FEV1/FVC = normal (or even slightly raised) 
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