Gas flow at 50% of forced expiration/Gas flow at 50% of forced inspiration^pre bronchodilation:RelVRat:Pt:Respiratory system:Qn
gas flow at 50% of forced expiration/gas flow at 50% of forced inspiration^pre bronchodilation:relvrat:pt:respiratory system:qn
FEF 50%/FIV 50% --pre bronchodilation
fef 50%/fiv 50% --pre bronchodilation