Clinically, equal flow volume measurement is often used to detect small airway lesions early, to determine whether small airway obstruction is reversible and obstruction. Scope of application: 1 early small airway function changes, such as pulmonary edema, bronchiolitis and so on. 2 judgment of airway obstruction in bronchial asthma patients. 3 Identification of upper airway obstruction and peripheral small airway obstruction.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

Applicable gender: whether men and women apply fasting: not fasting

Tips: Actively cooperate with doctors. Normal value

(1) Breathing He-O2 mixture is higher than breathing air, and Vmax increases at higher lung capacity.

(2) VisoV/VC ≤ 25%, that is, the equal flow volume is small.

Clinical significance

Clinical use:

(1) The upper airway airflow is a vortex, and its flow rate is greatly affected by the gas density. If a low-density gas such as a He-O2 mixture is breathed, the airway resistance is significantly lowered. Vmax increased significantly at higher lung volumes, indicating upper airway obstruction; conversely, peripheral small airway airflow was predominantly laminar and was less affected by gas density. Airway resistance does not change much when breathing He-O2 gas, even in the low lung volume stage, Vmax does not change much.

(2) In small airway lesions, due to the increase of airway resistance, the rate of decrease from the surrounding airway to the oral pressure is faster than that of normal people during exhalation, and small peripheral airway collapse occurs in the higher lung volume. The flow volume point is advanced and the equal flow volume is increased.

(3) After breathing He-O2 mixture, if the △Vmax50 of the higher lung volume level is >20%, it can be considered to react to the low-density gas, indicating that the airway obstruction is in the atmospheric channel; otherwise, if △Vmax50<20% There is no change, no response, indicating that the obstruction is in the small airway.

Scope of application:

1 early small airway function changes, such as pulmonary edema, bronchiolitis and so on.

2 judgment of airway obstruction in bronchial asthma patients.

3 Identification of upper airway obstruction and peripheral small airway obstruction.

High results may be diseases: obstructive emphysema, emphysema, bronchial asthma precautions

(1) The operator is required to patiently explain the measurement process to the subject in advance to achieve a good fit.

(2) The accuracy of the He-O2 mixture concentration ratio for the test must be guaranteed.

(3) The MEFV curve should be drawn after the subject did breathe the He-O2 mixture for 3 min.

(4) Guarantee MEFVHe-O2 and MEFVair. The starting and ending points of the two curves are completely or substantially identical, that is, the FVC differs by <5%.

Inspection process

Inhalation of low density gas is measured by the MEFV method. Since the He-O2 mixed gas has a lower density than air, the viscosity is larger than that of air. The MEFV curve after inhalation of He-O2 mixture is in the high lung capacity (mainly eddy current), V is higher than the air curve, and the low lung capacity (laminar flow) V coincides with the air curve, or is lower than the air curve. flow. Calculate the volume of the intersection of the two curves to the RV position, and increase the value to suggest small airway dysfunction.

Not suitable for the crowd

If you have a serious cardiopulmonary disease, you should consult your doctor before doing this check.

Adverse reactions and risks

Generally no complications and harm.