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JłKtructiye Lung Disease

RESPIRATORY PHYSIOLOGY

Masimum Expiratorv Flow-Volume Curves

Figurę 5.26 Obstructive Lung Disease

_>bstructive pulmonary disease refers to a group ot conditions (eg. -mphyscma, chronic bronchitis. and asthmal, all of whith cau.se shori--Kss of breath and obstruction of airtlow. Shown here is the effcr.l of v.ere emjłhysema on |>ulnK)nary function. In emphysema, inflamma-ptocesses destroy the connective tissue of the lung, and in particu-. • the elastic fibers that help maintain the patency ot the airways (i.e., v*tic recoil). Tl ter Horę, lung compliance is increased. The decreased -wstic recoil results in collapse of airways during expiration (a process termed dynamie compression; see Figurę 3.12) and air trappmg. The trapped air results in an inereaso in RC and FRC as a result nf a largp inerease in KV. In addition. dynamie compression of the airway pro-longs the forced expiratory yokime in the first second (FEV,>. as woli as the lorce expiratory flow ratę measured over the młddle hali of exjxra-tion (FEF_JVrrs.)- Because the VC (measured as forced vital capaaty |FVC|) is nnły dightły deaeasrd, or even normal. the rado of FEV,/FVC is typically less than 75%.

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