Effect ofDifferent Inspiratory Maneuvers on FEVi inPatients WithCystic Fibrosis

Thetimecourse ofinspiration hasbeenshown tohave asignificant influence on thesubsequent maximal expiratory flows andtimed forced expiratory volumes inhealthy adults andthose with COPD.Thepurpose ofthisstudy was toevaluate theeffect oftwodifferent inspiratory maneuvers on thespirogram in15patients withcystic fibrosis, aged 13to35years, whohadmild tomoderate airway obstruction. Patients performed a forced expiratory maneuver either after arapid inspira¬ tionwithout an end-inspiratory pause or after a slowinspiration with a 4-send-inspiratory pause. Flow-time andvolume-time curves were measured by apneumotachograph. Themean values of FVC,FEVi, andpeak expiratory flow were significantly larger by11%,13%, and26%,respectively, after therapid inspiration without an end-inspiratory pausecompared totheslowinspiration with theend-inspiratory pause. Thisdiscrepancy probably reflects differences ineffective elastic recoil pressure between thetwomaneuvers. Although thenatureofthisphenomenon isnotfully under¬ stood, our results showthat forspirometry inpatients withcystic fibrosis, thepreceding inspiratory maneuver influences theresults. Animportant corollary isthat this inspiratory maneuver should be standardized. (CHEST 1996; 110:642-47)