Respiratory Equations

Question 1

Cardiac Output (CO)

Answer 1

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

Question 2

Stroke Volume (SV)

Answer 2

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

Question 3

Cardiac Index (CI)

Answer 3

CI = CO/BSA
Units: %

Question 4

Oxygen Delivery (DO2)

Answer 4

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

Question 5

Mean Arterial Pressure (MAP)

Answer 5

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

Question 6

Alveolar Oxygen Tension (PAO2)

Answer 6

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

Question 7

Alveolar-Arterial Oxygen Tension Gradient (PAaO2)

Answer 7

PAaO2 = PAO2-PaO2
Units: mmHg

Question 8

Arterial Oxygen Content (CaO2)

Answer 8

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

Question 9

Mixed Venous Oxygen Content (CvO2)

Answer 9

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

Question 10

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

Answer 10

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

Question 11

End-Capillary Oxygen Content (CcO2)

Answer 11

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

Question 12

Oxygen Extraction Ratio (O2ER)

Answer 12

O2ER = CaO2-CvO2/CaO2
Units: %

Question 13

Pulmonary Vascular Resistance (PVR)

Answer 13

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

Question 14

Systemic Vascular Resistance (SVR)

Answer 14

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

Question 15

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

Answer 15

VD/Vt = (PaCO2-PeCO2/PaCO2)*100
Units: %

Question 16

Shunt Equation (Qs/Qt)

Answer 16

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

Question 17

Minute Volume (VE)

Answer 17

VE = f*Vt
Units: L/min

Question 18

Tidal Volume (Vt)

Answer 18

Vt = VE/f
Units: mL/breath

Question 19

Rapid Shallow Breathing Index (RSBI)

Answer 19

RSBI = RR/Vt
Units: Breaths/Min/L (BPM/L)

Question 20

Static Compliance (Cs)

Answer 20

Cs = Vt/Plat-PEEP
Units: mL/cmH2O

Question 21

Dynamic Compliance (Cd)

Answer 21

Cd = Vt/PIP-PEEP
Units: mL/cmH2O

Question 22

Resistance Airway (RAW)

Answer 22

RAW = PIP-Pplat/Flow
Units: L/sec
Will need to convert Flow from L/min to L/sec

Question 23

Calculate needed RR to get desired PaCO2

Answer 23

Desired RR (f) = Known PaCO2 x Known RR (f)/Desired PaCO2
Units: Breaths/min

Question 24

Calculate needed VE to get desired PaCO2

Answer 24

Desired VE = Known PaCO2 x Known VE/Desired PaCO2
Units: L/min

Question 25

Calculate needed fiO2 to get desired PaO2

Answer 25

Desired fiO2 = Desired PaO2 x (Known fiO2/Known PaO2)
Units: % or .

Question 26

Oxygen Index (OI)

Answer 26

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