▁in ▁the ▁right ▁vent ric le ▁causes ▁the ▁pul mon ic ▁val ve ▁to ▁stay ▁open ▁longer ▁during ▁vent ric ular ▁syst ole . ▁ ▁This ▁causes ▁a ▁normal ▁delay ▁in ▁the ▁P 2 ▁component ▁of ▁S 2 . ▁ ▁During ▁exp iration , ▁the ▁positive ▁intr ath or ac ic ▁pressure ▁causes ▁decre ased ▁blood ▁return ▁to ▁the ▁right ▁side ▁of ▁the ▁heart . ▁ ▁The ▁reduced ▁volume ▁in ▁the ▁right ▁vent ric le ▁allows ▁the ▁pul mon ic ▁val ve ▁to ▁close ▁earlier ▁at ▁the ▁end ▁of ▁vent ric ular ▁syst ole , ▁causing ▁P 2 ▁to ▁occur ▁earlier . ▁ ▁In ▁individuals ▁with ▁an ▁AS D , ▁ ▁a ▁fixed ▁splitting ▁of ▁S 2 ▁occurs ▁because ▁the ▁extra ▁blood ▁return ▁during ▁insp iration ▁gets ▁equal ized ▁between ▁the ▁left ▁and ▁right ▁at ria ▁due ▁to ▁the ▁communication ▁that ▁exists ▁between ▁the ▁at ria ▁in ▁individuals ▁with ▁AS D . ▁ ▁The ▁right ▁vent ric le ▁can ▁be ▁thought ▁of ▁as ▁continu ously ▁over loaded ▁because ▁of ▁the ▁left - to - right ▁sh unt , ▁producing ▁a ▁widely ▁split ▁S 2 . ▁Because ▁the ▁at ria ▁are ▁linked ▁via ▁the ▁at rial ▁sept al ▁defect , ▁insp iration ▁produces ▁no ▁net ▁pressure ▁change ▁between ▁them , ▁and ▁has ▁no ▁effect ▁on ▁the ▁splitting ▁of ▁S 2 . ▁Thus , ▁S 2 ▁is ▁split ▁to ▁the ▁same ▁degree ▁during ▁insp iration ▁as ▁exp iration , ▁and ▁is ▁said ▁to ▁be ▁“ fixed ”. ▁ ▁E ch oc ardi ography ▁ ▁In