Small airways in chronic obstructive pulmonary disease: why ignore them on spirometry report?/As pequenas vias aereas na doenca pulmonar obstrutiva cronica: por que ignora-las no laudo de espirometria?

According to World Health Organization the chronic obstructive pulmonary disease (COPD) was the fourth cause of death worldwide in 2012. The disorder of small airways is an important element in COPD. Narrowing of small airways is the major cause of increased airflow resistance in COPD, and there is evidence that small airway disorders occur early in the natural history of COPD. Thus, it is important that spirometry and other tests such as impulse oscillometry are used for the diagnosis of small airway disorders. In spirometry report, measurements of maximal mid expiratory flow or forced expiratory flow at 25%-75% of forced vital capacity ([MMEF.sub.75%-25%] or [FEF.25%-75%]) should be considered after the absence of obstruction are determined using the primary variables. If the [FEV.sub.1]/ FVC% ratio is borderline, a reduction in [MMEF.sub.75%-25%] or other terminal flows corrected for forced vital capacity, or elevated forced expiratory time, diagnose obstruction on small airways in symptomatic respiratory subjects. Keywords: Pulmonary disease, chronic obstructive; Oscillometry; Spirometry. De acordo com a Organizacao Mundial da Saude, a doenca pulmonar obstrutiva cronica (DPOC) foi a quarta causa de morte em todo o mundo em 2012. O disturbio das pequenas vias aereas e um elemento importante na DPOC. O estreitamento das pequenas vias aereas e a causa principal de aumento da resistencia do fluxo de ar na DPOC. Ha evidencias que lesoes das vias aereas pequenas ocorrem no inicio da historia natural da DPOC. Assim, e importante que a espirometria e outros testes, como a oscilometria de impulso, sejam usados para o diagnostico de doencas das pequenas vias aereas. No laudo de espirometria, as medidas do fluxo expiratorio medio maximo ([MMEF.sub.25%-75%] ou [FEF.sub.25%-75%) devem ser consideradas usando as variaveis primarias, apos diagnosticada ausencia de obstrucao. Se a relacao [VEF.sub.1] / CVF% for limitrofe, uma reducao no [MMEF.sub.25%-75%] ou outros fluxos terminais corrigidos para a capacidade vital forcada ou tambem o tempo expiratorio forcado elevado, diagnosticam a obstrucao do fluxo em pequenas vias aereas em individuos respiratorios sintomaticos. Descritores: Doenca pulmonar obstrutiva cronica; Oscilometria; Espirometria.