Forced expiratory volume in one second/Forced expiratory volume in six seconds ratio
forced expiratory volume in one second/forced expiratory volume in six seconds ratio
FEV1 (forced expiratory volume in 1 second)/FEV6 (forced expiratory volume in 6 seconds) ratio
fev1 (forced expiratory volume in 1 second)/fev6 (forced expiratory volume in 6 seconds) ratio