Shunts (Qp/Qs > 1 = L -> R, < 1 = R -> L, shunt > 1.5 = closure)
MVO2 = 3(SVC) + IVC /4
Systemic flow = O2 consumption / 10 * A -V mixed O2 dif
Pulmonary flow = O2 consumption / 10 * PV - PA O2 dif
Normal: SYS = PULM flow
L -> R: PULM = SYS + shunt
R -> L: SYS = PULM + shunt
step up > 7% SVC/IVC -> RA
step up > 5% RA -> RV or RV -> PA
Example L -> R (ASD)
Hgb 13
O2 consumption = 3 * 70 = 210
Sats: Art 92, IVC 68, SVC 70, mid RA 85, low RA 68, PA 83, PV 95
1) Art O2 content = 0.92 * 1.36 * 13 * 10 = 163
2) MV O2 content = 3(.70) + .68 /4 = 0.69 * 1.36 * 13 * 10 = 122
3) PA O2 content = 0.83 * 1.36 * 13 * 10 = 147
4) PV O2 content = 0.95 * 1.36 * 13 * 10 = 168
Qs = 210 / (163 - 122) = 5.12
Qp = 210 / ( 168-147) = 10
Qp/Qs = 10/5.12 = 1.96
Simplified = Arterial O2 - MVO2 / Pulm v O2 - Pulm a O2 = 92-69/95-83 = 1.92 (L -> R > 1)