• Diagnose or manage asthma
  • Detect respiratory disease in patients presenting with symptoms of breathlessness, and to distinguish respiratory from cardiac disease as the cause Measure bronchial responsiveness in patients suspected of having asthma
  • Diagnose and differentiate between obstructive lung disease and restrictive lung disease
  • Follow the natural history of disease in respiratory conditions
  • Assess of impairment from occupational asthma
  • Identify those at risk from pulmonary barotrauma while scuba diving
  • Conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery
  • Measure response to treatment of conditions which spirometry detects
  • Diagnose the vocal cord dysfunction.
  • Forced expiratory maneuvers may aggravate some medical conditions.
  • Spirometry should not be performed when the individual presents with:
  • Hemoptysis of unknown origin
  • Pneumothorax
  • Unstable cardiovascular status (angina, recent myocardial infarction, etc.)
  • Thoracic, abdominal, or cerebral aneurysms
  • Cataracts or recent eye surgery
  • Recent thoracic or abdominal surgery
  • Nausea, vomiting, or acute illness
  • Recent or current viral infection
  • Undiagnosed hypertension
  • The basic forced volume vital capacity (FVC) test varies slightly depending on the equipment used.
  • Generally, the patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, for as long as possible, preferably at least 6 seconds. It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction. Sometimes, the test will be preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the rapid breath in (forced inspiratory part) will come before the forced exhalation.
  • During the test, soft nose clips may be used to prevent air escaping through the nose. Filter mouthpieces may be used to prevent the spread of microorganisms.

FEV1 80% to 120%
FVC 80% to 120%
Absolute FEV1 /FVC ratio Within 5% of the predicted ratio
TLC 80% to 120%
FRC 75% to 120%
RV 75% to 120%
DLCO > 60% to < 120%
DLCO = diffusing capacity of lung for carbon monoxide.
ERV is measured by the device, Bellow's spirometer

Exam Question
  • Spirometry measures Tidal volume, IRV,Vital capacity & FEV
  • Residual volume Cannot be measured directly with a spirometer
  • ERV is measured by the device, Bellow's spirometer
Don't Forget to Solve all the previous Year Question asked on Spirometry