What is mid-expiratory flow?
The mid maximum expiratory flow (MMEF) is obtained by drawing the chord across the middle half of the vital capacity and dividing the volume by the time. It may be related to the tangent to the curve at 50 per cent point which is V ˙ 50 (see text)
What does MMEF mean?
Maximal mid-expiratory flow (MMEF), forced expiratory volume in 1 s (FEV1), ratio of FEV1/forced vital capacity (FVC), health status, presence of emphysema (computed tomography (CT) densitometry) and subsequent decline in FEV1 were assessed in 196 AATD patients.
What affects PEFR?
Many factors will influence PEFR including a patient’s age, gender and height. Pulmonary problems such as asthma and chronic obstructive pulmonary disease will result in a reduction in flow. Muscle mass will also play a key role in determining PEFR.
What is maximal mid-expiratory flow rate?
Background. The maximal expiratory flow at 50 % of the forced vital capacity (MEF50) is the flow where half of forced vital capacity (FVC) remains to be exhaled . It corresponds to the forced expiratory flow at 50 % (FEF50) and correlates highly with the maximum mid-expiratory flow (FEF25-75 %) .
What is forced expiratory flow?
Forced expiratory flow (FEF) is the flow (or speed) of air coming out of the lung during the middle portion of a forced expiration. It can be given at discrete times, generally defined by what fraction of the forced vital capacity (FVC) has been exhaled.
What stage of the expiratory cycle is peak expiratory flow rate maximal?
The peak expiratory flow (PEF) is the maximum flow obtained within the first 200 milliseconds of a forced expiratory maneuver after inhalation to total lung capacity (TLC). PEF meters are portable, inexpensive, and easily used.
Why is peak expiratory flow important?
Peak flow measurement using a peak flow meter is useful for people with asthma. During an asthma flare-up, the large airways in the lungs slowly begin to narrow. This slows the speed of air moving through the lungs. A peak flow meter can help show the narrowing of the airways well before an asthma attack happens.
What is normal forced expiratory flow rate?
Forced expiratory volume in 1 second (FEV1) Values of between 80% and 120% of the average value are considered normal.
What is the normal range for PEF?
In men, readings up to 100 L/min lower than predicted are within normal limits. For women, the equivalent figure is 85 L/min. Values are derived from Caucasian populations. Normal PEF values in children correlate best with height; with increasing age, larger differences occur between the sexes.
What is FEV Test?
Forced expiratory volume (FEV) measures how much air a person can exhale during a forced breath. The amount of air exhaled may be measured during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath. Forced vital capacity (FVC) is the total amount of air exhaled during the FEV test.