What does NFL stand for?

The negative expiratory pressure technique (NEP) method is based on the principle that the increase in pressure caused by NEP should result in increased expiratory flow. By contrast, in flow-limited subjects, application of NEP should not change the expiratory flow (Koulouris et al 1995). For technical details we refer the reader elsewhere. This method does not require FVC maneuvers, collaboration on the part of the patient, or use of a body plethysmograph, and can be used during spontaneously breathing subjects during exercise (Calverley and Koulouris 2005).