Spirometry

Introduction

Spirometry is one of the most commonly performed tests to evaluate the respiratory function, in children above 5 years of age. It is the measurement of the rate of change of lung volume during forced breathing maneuvers. The instrument is called the spirometer and the tracing that is generated is called the spirogram.

Test

The child’s torso and head should be erect. The mouthpiece is held with the lips pressed firmly to form an air- tight seal. Nose clips may be used to yield better results. First the child makes a quick, full inhalation. This is then followed by a rapid, forced expiration, which almost empties the lungs, without coughing or quitting the procedure. The rise from inspiration to TLC should be rapid ( 2 seconds). Expiration is continued for as long as possible or until a plateau in exhaled volume is reached. This is followed by a long inspiration without a pause. At least three separate flow – volume curves are obtained which appear similar in spirogram and with FVCs within 5% or 150 ml (100 ml if FVC 1 L), whichever is less. If your pulmonologist advices a pre and post bronchodilator spirometry can be performed.