Equations

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Contents

1 Body Surface Area
2 Endocrinology
3 Respiratory
- 3.1 ABG

Body Surface Area

BSA (m²) = ( [Height(cm) x Weight(kg) ]/ 3600 )½ e.g. BSA = SQRT( (cm*kg)/3600

Endocrinology

Corrected Calcium = (40 - albumin)x0.02 + total Calcium

Respiratory

ABG

Total O₂ blood content = Bound to Hb + Dissolved
- $Total\ Blood\ O_2 = \left ( 1.36 ml/g\ Hb \times %\ Hb\ sat \times Hb \right ) + \left ( 0.03 ml\ O_2/L\ torr \times pO_2 \right )$

PAO₂
- $PAO_2 = \left ( F_iO_2 \times Pressure \right ) - \left ( \frac{PaCO_2}{0.8} \right )$
- No pathology, at sea level: F_iO₂ = 0.21, Pressure = ATM (760) - Vapor (47), PaCO₂ = 40
AaDO₂
- $A a D O 2 = P A O 2 - P a O 2$
- If this is greater than 15 on room air, or greater than 100 on 100% O₂, suggests intrinsic lung disease

- where V_T = tidal volume, RR = respiratory rate, V_E = minute ventilation
- Calculation for minute ventilation, which must be constant to maintain adequate gas exchange

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