▁and ▁cap ill aries ▁due ▁to ▁vis c ous ▁losses ▁of ▁energy . ▁Mean ▁blood ▁pressure ▁dro ps ▁over ▁the ▁whole ▁circul ation , ▁although ▁most ▁of ▁the ▁fall ▁occurs ▁along ▁the ▁small ▁ar ter ies ▁and ▁ar ter i oles . ▁Gra vity ▁affect s ▁blood ▁pressure ▁via ▁hydro static ▁forces ▁( e . g ., ▁during ▁standing ), ▁and ▁val ves ▁in ▁ve ins , ▁breath ing , ▁and ▁p ump ing ▁from ▁contra ction ▁of ▁ske let al ▁mus cles ▁also ▁influence ▁blood ▁pressure ▁in ▁ve ins . ▁ ▁The ▁relationship ▁between ▁pressure , ▁flow , ▁and ▁resistance ▁is ▁expressed ▁in ▁the ▁following ▁equation : ▁ ▁Flow ▁= ▁Press ure / Res istance ▁ ▁When ▁applied ▁to ▁the ▁circul atory ▁system , ▁we ▁get : ▁▁ ▁CO ▁= ▁( MAP ▁– ▁R AP )/ TP R ▁where ▁ ▁CO ▁= ▁card iac ▁output ▁( in ▁L / min ) ▁ ▁M AP ▁= ▁mean ▁ar ter ial ▁pressure ▁( in ▁mm H g ), ▁the ▁average ▁pressure ▁of ▁blood ▁as ▁it ▁leaves ▁the ▁heart ▁ ▁R AP ▁= ▁right ▁at rial ▁pressure ▁( in ▁mm H g ), ▁the ▁average ▁pressure ▁of ▁blood ▁as ▁it ▁returns ▁to ▁the ▁heart ▁ ▁T PR ▁= ▁total ▁peri pher al ▁resistance ▁( in ▁mm H g ▁* ▁min / L ) ▁ ▁A ▁simplified ▁form ▁of ▁this ▁equation ▁assumes ▁right ▁at rial ▁pressure ▁is ▁approximately ▁ 0 : ▁ ▁CO ▁ ≈ ▁M AP / TP R ▁ ▁The ▁ideal ▁blood ▁pressure ▁in