Qp-Qs

    Pulmonary to Systemic volumetric blood flow ratio.

    Calculated to assess the significance of shunts (in particular septal defects of the heart).

    Normal ratio is 1:1 (Qp/Qs = 1).

    Qp/Qs >= 2(2:1) may indicate the development of irreversible pulmonary hypertension. According to various authors, Qp/Qs >= 1.5, in combination with other criteria, is considered an indication for surgical treatment (shunt closure).