Spirometry can help interpret lung function and diagnose obstructive and restrictive lung disease. A spirometric device works by measuring the airflow into and out of the lungs. The medical device is used to diagnose conditions like asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing. The article explains the ideal index pattern of the airflow in the device. 

Empey’s index [1]

It shows a relationship between PEF and FEV1 and that a disproportionately low PEF should alert the clinician to the possibility of upper airway obstruction. Empey’s index is the ratio of forced expiratory volume in 1s (FEV1) in ml and peak expiratory flow (PEF) in L/min.

FEF50/FIF50 [2]

(FEF50 is forced expiratory flow at 50% or mid expiration, and FIF50 is forced inspiratory flow at 50% or mid inspiration)

Types of flow-volume loops

This article was originally published on 22 July 2021.

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