Peak Expiratory Flow RatePeak Expiratory Flow Rate(PEFR)(PEFR) Measures how fast a person can exhale air Requires a peak expiratory flow monitorOmronMini-Wright AM2 Plus
PEFR VariabilityPEFR VariabilityAsthma Diagnostic Clues:• PEF Variability > 20%(basis: home monitoring 2-4x/dayfor 1-2 weeks)• Improvement in baseline PEF by20% after a 2-week therapeutictrialPEFmax - PEFminPEFave(pm, post-bd) (am, pre-bd)% Variability = X 1000501001502002503003501 2 3 4 5 6 7DaysPEFR(L/min)pm PEFRam PEFR
SpirometrySpirometry Recommended for the initial assessment of allasthma suspects!
> 15% increase in FEV1.0after ß-2 inhalationHallmark of Asthma: Reversibility!Spirometry
Types of FlowVolume CurvesNormal ObstructiveLiterspersecondConcavityAsthmaConcavitypre-bronchodilatorImprovedpost-bronchodilator
Good MeasurementsGood Measurementsare Essential!are Essential!AcceptableLoopUnacceptableLoop
Is it Asthma?Determine that the patient isexperiencing episodic symptomsof airflow obstructionDemonstrate that theobstruction is at least partiallyreversibleExclude alternate diagnoses
AsthmawheezingLung Disease OverlapChronicBronchitiscough+sputumEmphysemabreathlessnessAirway Remodeling inAsthmaDenudation of the airwayepitheliumCollagen depositionbeneath the basementmembraneEdemaMast cell activationInflammatory cellinfiltrationCOPD