Respiratory Equations

Question 1

Cardiac Output (CO)

Answer 1

CO = HR*SV = L/min
SV/1000 = L/min

Question 2

Cardiac Index (CI)

Answer 2

CI = CO/BSA
Units: %

Question 3

Mean Arterial Pressure (MAP)

Answer 3

MAP = SBP + 2(DBP)/3
Units: mmHg

Question 4

Alveolar Oxygen Tension (PAO2)

Answer 4

PAO2 = (Pb-PH2O)FiO2 - (PaCO2*1.25)
Units: mmHg
Barometric Pressure Pb(norm): 760
Water Vapor PH20 (Constant): 47

Question 5

Alveolar-Arterial Oxygen Tension Gradient (PAaO2)

Answer 5

PAaO2 = PAO2-PaO2
Units: mmHg

Question 6

Arterial Oxygen Content (CaO2)

Answer 6

CaO2 = (Hb1.34SaO2) + (PaO2*.003)
Units: mL/dL

Question 7

Mixed Venous Oxygen Content (CvO2)

Answer 7

CvO2 = (Hb1.34SvO2) + (PvO2*.003)
Units: mL/dL

Question 8

Arterial-Mixed Venous Oxygen Content Gradient (Ca-vO2)

Answer 8

Ca-vO2 = CaO2-CvO2
Units: mL/dL

Question 9

End-Capillary Oxygen Content (CcO2)

Answer 9

CcO2 = (Hb1.34) + (PAO2.003)
Units: mL/dL

Question 10

Pulmonary Vascular Resistance (PVR)

Answer 10

PVR = (MPAP-PCWP)80/CO
Units: Dynes/Sec/cm^5

Question 11

Systemic Vascular Resistance (SVR)

Answer 11

SVR = (MAP-CVP)80/CO
Units: Dynes/Sec/cm^5

Question 11

Oxygen Delivery (DO2)

Answer 11

DO2 = (CaO2*CO)10
Units: mL/min

Question 12

Deadspace-to-Tidal Volume Ratio (VD/Vt)

Answer 12

VD/Vt = PaCO2-PeCO2/PaCO2
Units: %

Question 13

Shunt Equation (Qs/Qt)

Answer 13

Qs/Qt = CcO2-CaO2/CcO2-CvO2
Units: Vol%

Question 14

Stroke Volume (SV)

Answer 14

SV = CO/HR
Units: mL/beat
CO*1000 = mL

Question 15

Minute Volume (VE)

Answer 15

VE = f*Vt
Units: L/min

Question 16

Tidal Volume (Vt)

Answer 16

Vt = VE/f
Units: mL/breath

Question 17

Oxygen Index (OI)

Answer 17

OI = ((PAWFiO2)/PaO2)100
Units: %

Question 18

Oxygen Extraction Ratio (O2ER)

Answer 18

O2ER = CaO2-CvO2/CaO2
Units: %