▁principal ▁determin ant ▁to ▁control ▁resistance . ▁Comp ared ▁to ▁other ▁smaller ▁vessels ▁in ▁the ▁body , ▁the ▁ar tery ▁has ▁a ▁much ▁bigger ▁diameter ▁( 4   ▁mm ), ▁therefore ▁the ▁resistance ▁is ▁low . ▁ ▁The ▁arm – leg ▁( blo od ▁pressure ) ▁gradient ▁is ▁the ▁difference ▁between ▁the ▁blood ▁pressure ▁measured ▁in ▁the ▁arms ▁and ▁that ▁measured ▁in ▁the ▁legs . ▁It ▁is ▁normally ▁less ▁than ▁ 1 0   mm ▁H g , ▁but ▁may ▁be ▁increased ▁in ▁e . g . ▁co arct ation ▁of ▁the ▁a ort a . ▁ ▁C lin ical ▁significance ▁ ▁Press ure ▁monitoring ▁ ▁Hem od ynamic ▁monitoring ▁is ▁the ▁observation ▁of ▁hem od ynamic ▁parameters ▁over ▁time , ▁such ▁as ▁blood ▁pressure ▁and ▁heart ▁rate . ▁Blood ▁pressure ▁can ▁be ▁monitor ed ▁either ▁invas ively ▁through ▁an ▁inserted ▁blood ▁pressure ▁trans du cer ▁assembly ▁( prov iding ▁continuous ▁monitoring ), ▁or ▁non in vas ively ▁by ▁repeatedly ▁meas uring ▁the ▁blood ▁pressure ▁with ▁an ▁infl atable ▁blood ▁pressure ▁cu ff . ▁ ▁Rem ote , ▁indirect ▁monitoring ▁of ▁blood ▁flow ▁by ▁las er ▁Do pp ler ▁ ▁Non in vas ive ▁hem od ynamic ▁monitoring ▁of ▁eye ▁fund us ▁vessels ▁can ▁be ▁performed ▁by ▁Las er ▁Do pp ler ▁h olog raph y , ▁with ▁near ▁inf ra red ▁light . ▁The ▁eye ▁offers ▁a ▁unique ▁opportunity ▁for ▁the ▁non - in vas ive ▁expl oration ▁of ▁card i ov asc ular ▁dise ases . ▁Las er ▁Do pp ler