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The spirometry test is performed using a device called a spirometer, [2] which comes in several different varieties. Most spirometers display the following graphs, called spirograms: a volume-time curve, showing volume (litres) along the Y-axis and time (seconds) along the X-axis
The amount of He in the spirometer is known at the beginning of the test (concentration × volume = amount). The patient is then asked to breathe (normal breaths) in the mixture starting from FRC (functional residual capacity), which is the gas volume in the lung after a normal breath out. The spirometer measures helium concentration.
Pulmonary function testing (PFT) is a complete evaluation of the respiratory system including patient history, physical examinations, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity of pulmonary impairment. [1]
A spirometer is the main piece of equipment used for basic Pulmonary Function Tests (PFTs). Lung diseases such as asthma, bronchitis, and emphysema may be ruled out from the tests.
An initial spirometry is performed to assess the patient's native respiratory status. The patient will be asked to take a deep breath and then blow into the mouthpiece of the spirometer as hard as you can.
This test involves measuring the partial pressure difference between inspired and expired carbon monoxide. It relies on the strong affinity and large absorption capacity of red blood cells for carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent on cardiac output . [ 3 ]
Output of a spirometer. Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inhalation.It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
[1] [2] It cannot be estimated through spirometry, since it includes the residual volume. In order to measure RV precisely, one would need to perform a test such as nitrogen washout, helium dilution or body plethysmography. [3] Positioning plays a significant role in altering FRC.