Upka tukimasining zichlashish sindromi upka tukimasining ma'lum kismida havo mikdoning kamayishi yoki butunlay yukolishi (segment, bulak, bir necha bulak). Sabablari: yalliglanish infiltratsiyasi (uchokli zotiljam, sil infiltrati); tromboemboliya yoki maxalliy tomir trombozi natijasida kelib chikadigan upka infarkti, atelektaz (obturatsion, kompressiyon) yoki gipoventilatsiya (fibroz tukima, bronkopulmonal limfa tugunlari hisobiga bronch utkazuv yullarining torayishi); upka usmasi; dimlanishi hisobiga yurak etishmovchiligi