Ability ofsingle-breath nitrogen closing volume todetect early airway obstruction

Funahashi, A.,Melville, G.N.,andHamilton, L.H.(1975). Thorax,30,220-224. Ability ofsingle-breath nitrogen closing volumetodetect earlyairwayobstruction. Inorderto determine theability ofsingle-breath nitrogen closing volume(CV)to detectearly airway obstruction, theCV was measuredinpatients witheither minimalobstruction on spirometry or withincreased residual volume(RV).A totalof39subjects was included inthis study. Themean CV was largest inpatients whohadreduced maximum mid-expiratory flowrates(MMF).Therewas no difference inmean CV between smokers andthepatients whohadlarge RV butno airway obstruction, although both groupshadhigher mean CV thanex-smokers. NormalCV was seen infourof11 patients whohadreduced MMF andinfourofseven whohadlarge RV butno airway obstruction. Allex-smokers hadnormalCV whilefive of12smokers hadabnormal CV.The results indicate thatthie closing volumeshouldbeusedto complement spirometry, rather thantoreplace it,forscreening ofearly airway obstruction.