Pulmonary function tests should be performed on all children with asthma over the age of 5. Children with asthma have more or less changes in their lung function, whether during an attack or in remission, and lung function can reflect the severity of the disease. By understanding the lung function of the child, the doctor can not only help to diagnose some children with asthma of short duration, but also to understand and evaluate the efficacy of the medication, observe the condition of the child, and develop the next treatment plan. Maximal expiratory flow rate is the most common simple pulmonary function test for asthma patients, which mainly reflects the ventilation function of the test subject. Therefore, the maximum expiratory flow rate can be measured to understand the expiratory ventilation of the test subject to reflect the condition. A peak flow meter is a device that measures the speed of airflow exhaling from the lungs. Children can bring their own peak flow meter at home to test the maximum expiratory flow rate, and insist on measuring the maximum expiratory flow rate regularly every day, keeping an asthma diary or drawing a chart, and bringing the monitoring results to the doctor at the follow-up appointment, so that the doctor can help analyze the control of asthma, compare the efficacy of various treatments, and formulate the best treatment plan. How to use the peak flow tachometer: 1.Tighten the slightly thicker end of the transparent interface with the round interface of the peak tachometer; 2.Gently dial the red vernier pointer of the peak tachometer to the lowest part of the scale; 3.Stand up. Open your mouth, breathe in as much as possible, then wrap your lips around the interface, pay attention to the lips around not to leak air, and then in the shortest possible time, exhale all the air at once; 4, at this time, please record the value of the red cursor pointing to the scale; 5, and then repeat the above steps two times, each time to record the number, a total of three times; 6, the three times the highest value measured recorded as the final maximum expiratory flow rate value, with the test 7.After each measurement, the peak velocity meter will be stored properly for reuse.