How is it done?

The mouth piece is to be held tightly between lips to prevent any air leak.(a nose clip is put on to prevent extra air entering.).

Patient has to inhale & exhale normally 4-5 times. Then the patient is required to take a deep breath in, hold it for a while, and then exhale forcefully and completely, emptying his lungs as much as he can. This has to be repeated a few times as required.

The second step is to inhale and exhale normally 4-5 times. Then, the patient has to take a deep breath in, and exhale normally & completely, expelling as much air as possible from his lungs.

The last step is to continuously inhale & exhale forcefully for 30 seconds this process is called Hyperventilation.The tracings of all volume displacement against time are recorded.