Healthcare & Clinical
Systemic & Pulmonary Vascular Resistance (SVR & PVR in dyn·s·cm⁻⁵)
Calculate ICU hemodynamic Systemic Vascular Resistance SVR = 80 * (MAP - CVP) / CO and Pulmonary Vascular Resistance PVR = 80 * (mPAP - PCWP) / CO in dyn·s·cm⁻⁵ and Wood units.
Differentiate distributive vasodilatory shock from cardiogenic and hypovolemic shock!
Applying Darcy-Ohm's law to human circulation divides trans-bed pressure drop (in mmHg) by Cardiac Output CO (in L/min) to give resistance in Hybrid Reference ("Wood") Units (mmHg·min/L), and multiplying by 79.99 (~80) converts directly into CGS metric resistance units dyn·s·cm^-5! Normal adult Systemic Vascular Resistance SVR = 80 * (MAP - CVP) / CO spans 800 to 1,200 dyn·s·cm^-5 (10–15 Wood units).
Across the right-heart circuit, Pulmonary Vascular Resistance PVR = 80 * (mPAP - PCWP) / CO measures precapillary pulmonary arterial tone between Mean Pulmonary Artery Pressure (mPAP) and Pulmonary Capillary Wedge Pressure (PCWP): normal PVR lies below 160–240 dyn·s·cm^-5 (< 2–3 Wood units), whereas PVR > 240 dyn·s·cm^-5 (> 3 Wood units) defines precapillary pulmonary arterial hypertension!
| ICU Hemodynamic Profile | Pressures (mmHg) & CO (L/min) | SVR / PVR (dyn·s·cm^-5) | Shock / Vascular Phenotype |
|---|---|---|---|
| Distributive / Septic Shock | MAP = 65, CVP = 10, CO = 7.5 | 586.7 dyn·s·cm^-5 (< 800) | Pathologic Vasodilation |
| Cardiogenic Shock | MAP = 75, CVP = 15, CO = 2.5 | 1,920.0 dyn·s·cm^-5 (> 1200) | Compensatory Vasoconstriction |
| Pulmonary Arterial Hypertension | mPAP = 32, PCWP = 12, CO = 5.0 | 320.0 dyn·s·cm^-5 (4.0 Wood U) | Precapillary PAH (> 3 Wood U) |
Systemic Vascular Resistance SVR = 80 * (MAP - CVP) / CO (dyn·s·cm⁻⁵)
Evaluates SVR from Mean Arterial Pressure B2 (mmHg), Central Venous Pressure B3 (mmHg), and Cardiac Output B4 (L/min).
=IF(OR(B4 <= 0, B2 <= B3), "Invalid CO or Pressure Gradient", ROUND((80 * (B2 - B3)) / B4, 1))Pulmonary Vascular Resistance PVR (dyn·s·cm⁻⁵ & Wood Units)
Evaluates PVR = 80 * (mPAP - PCWP) / CO from Mean PAP B5 and Wedge Pressure B6 (divide by 80 for Wood units).
=IF(OR(B4 <= 0, B5 <= B6), "Invalid CO or Pulmonary Gradient", ROUND((80 * (B5 - B6)) / B4, 1))Try the example
Use the original values or change them to test your understanding.