RCIS Formula Sheet
Every calculation the RCIS exam expects you to know — output, pressures, resistances, valve area, shunts, oxygen, and QTc — on one printable page.
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<a href="https://rcispracticetest.com/cheat-sheets/rcis-formulas.html">RCIS Formula Sheet — RCIS Practice Test</a>Educational use only — not medical advice. Values are standard adult references; always confirm against current guidelines and your institution’s protocols.
Cardiac output & flow
| Quantity | Formula |
|---|---|
| Fick cardiac output | CO = VO₂ ÷ (1.36 × Hgb × 10 × (SaO₂ − SvO₂)) |
| Cardiac index | CI = CO ÷ BSA |
| Stroke volume | SV = (CO × 1000) ÷ HR |
| Stroke volume index | SVI = SV ÷ BSA |
| Ejection fraction | EF = (EDV − ESV) ÷ EDV × 100 |
Pressures
| Quantity | Formula |
|---|---|
| Mean arterial pressure | MAP = DBP + ⅓ (SBP − DBP) |
| Pulse pressure | PP = SBP − DBP |
| Coronary perfusion pressure | CPP = aortic DBP − PCWP (or LVEDP) |
| Rate-pressure product | RPP = HR × SBP |
Vascular resistance
| Quantity | Formula |
|---|---|
| Systemic vascular resistance | SVR = (MAP − CVP) ÷ CO × 80 |
| Pulmonary vascular resistance | PVR = (mPAP − PCWP) ÷ CO × 80 |
| PVR in Wood units | PVR = (mPAP − PCWP) ÷ CO |
Valve area
| Quantity | Formula |
|---|---|
| Gorlin (aortic valve area) | AVA = flow ÷ (44.3 × √mean gradient), flow = CO(mL/min) ÷ (SEP × HR) |
| Hakki (quick estimate) | AVA ≈ CO ÷ √(peak gradient) |
| Mitral valve area (pressure half-time) | MVA ≈ 220 ÷ PHT |
Shunt
| Quantity | Formula |
|---|---|
| Qp:Qs (shunt ratio) | (SaO₂ − MvO₂) ÷ (PvO₂ − PaO₂) |
SaO₂ = systemic arterial, MvO₂ = mixed venous, PvO₂ = pulmonary vein, PaO₂ = pulmonary artery. A ratio > 1.5–2.0 is significant.
Oxygen
| Quantity | Formula |
|---|---|
| Arterial O₂ content | CaO₂ = (1.34 × Hgb × SaO₂) + (0.003 × PaO₂) |
| Oxygen delivery | DO₂ = CO × CaO₂ × 10 |
| Oxygen extraction ratio | (SaO₂ − SvO₂) ÷ SaO₂ × 100 |
| Oxygen consumption (reverse Fick) | VO₂ = CO × (CaO₂ − CvO₂) × 10 |
ECG & other
| Quantity | Formula |
|---|---|
| QTc (Bazett) | QTc = QT ÷ √RR |
| QTc (Fridericia) | QTc = QT ÷ ∛RR |
| Heart rate (regular) | 300 ÷ large boxes, or 1500 ÷ small boxes |
| Heart rate (irregular) | QRS complexes in 6 s × 10 |
| Body surface area (Mosteller) | BSA = √(height cm × weight kg ÷ 3600) |
| Wall stress (Laplace) | σ = (P × r) ÷ (2 × h) |
Practise applying these under time pressure with the free calculations question bank, or check your work with the QTc calculator and hemodynamic calculator.
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Practise Calculations →Frequently asked questions
What is the Fick formula for cardiac output?
CO = VO₂ ÷ (1.36 × Hgb × 10 × (SaO₂ − SvO₂)). It divides oxygen consumption by the arteriovenous oxygen difference.
How do you calculate SVR?
SVR = (MAP − CVP) ÷ CO × 80, giving dynes·s·cm⁻⁵ (normal 800–1200). Drop the ×80 for Wood units.
What is the difference between the Gorlin and Hakki formulas?
Both estimate valve area. Gorlin is the full hemodynamic formula using flow and mean gradient; Hakki (CO ÷ √peak gradient) is a quick bedside approximation.
Can I print this RCIS formula sheet?
Yes — use the 'Print / Save as PDF' button at the top for a clean one-page copy.
Sources & further reading
- Cardiovascular Credentialing International (CCI)
- American College of Cardiology
- American Heart Association
- MedlinePlus (U.S. National Library of Medicine)
External links are provided for reference; always confirm current details with the official source.