Equations

Question 1

Oxygen content

Answer 1

CaO2= (Hgb x SaO2 x 1.34) + (PaO2 x 0.003)

= 20mL/dL

Question 2

Oxygen delivery

Answer 2

DO2 = CO x [(Hgb x SaO2 x 1.34) + (PaO2 x 0.003)] x 10

= 1,000 mL

Question 3

Oxygen consumption

Answer 3

VO2 = CO x (CaO2 - CvO2) x 10

= 250mL/min or 3.5mL/kg/min

Question 4

Static compliance

Answer 4

= tidal volume / (PP - PEEP)

Question 5

Dynamic compliance

Answer 5

= tidal volume / (PIP - PEEP)

Question 6

Alveolar gas equation

Answer 6

PAO2 = FiO2 x (Patm - Pvapor) - PaCO2/RQ

Question 7

A-a gradient

Answer 7

= PAO2 - PaO2

= 5-15 mmHg

Question 8

Ejection Fraction

Answer 8

= (EDV - ESV)/ EDV

Question 9

MAP

Answer 9

= 1/3 SBP + 2/3 DBP

Question 10

SVR

Answer 10

= [(MAP - CVP)/ CO] x 80

= 800-1500 dynes/sec/cm-5

Question 11

PVR

Answer 11

= [(PAP - PAOP)/ CO] x 80

= 150-250 dynes/sec/cm-5

Question 12

Coronary perfusion pressure

Answer 12

= AoDBP - LVEDP (or PaOP)

= 60-140 mmHg

Question 13

Max allowable blood loss

Answer 13

= EBV x (starting hct - target hct)/ starting hct

Question 14

Cerebral perfusion pressure

Answer 14

= MAP - ICP (or CVP)

= 50-150 mmHg

Question 15

Anion gap

Answer 15

= [Na] - ([Cl] + [HCO3])

= 8-12 mEq/L

Gap = accumulation of acid
Non-gap= loss of bicarb or ECF dilution

Question 16

Plasma osmolarity=

Answer 16

2Na + 0.055glucose + 0.36BUN

= 280-290 mOsm/L

Question 17

Uncuffed ETT peds

Answer 17

= (age/4) + 4

Question 18

Cuffed ETT peds

Answer 18

(Age/4) + 3.5

Question 19

O2 remaining in cylinder

Answer 19

Step 1: (Tank capacity L/full tank pressure psi) = (contents remaining L/gauge pressure psi)

Step 2: contents remaining / flow rate L/min = min left

Question 20

FiO2

Answer 20

= [(O2 flow rate x 100) + (air flow rate x 21)] / total flow rate

Question 21

Parkland formula

Answer 21

4mL LR x % TBSA burned x kg
• 1/2 in first 8 hrs
• 1/2 in next 16 hrs

Question 22

Modified Brooke formula

Answer 22

2 mL LR x % TBSA burned x kg
• 1/2 first 8 hrs
• 1/2 next 16 hrs

Question 23

Celsius to Fahrenheit

Answer 23

F= (C x 1.8) + 32

Question 24

Fahrenheit to Celsius

Answer 24

C = (F - 32) x 5/9