M5 Equations Flashcards

1
Q

Alveolar Gas Equation

A

PAO2 = FIO2 (PATM – PH2O )– PaCO2 / RQ

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2
Q

Dead Space (Bohr Equation)

A

VD/VT = (PaCO2 –PECO2) / (Pa CO2)

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3
Q

Ohm’s Law

A

Pressure Gradient = Air Flow x Airway Resistance

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4
Q

Airway Resistance for Laminar Flow (Poiseuille’s Law)

A

Laminar Flow Resistance = (8 Length • Viscosity of gas) / (πRadius^4 )

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5
Q

Reynold’s Number

A

R = (Velocity x Density x Diameter) / (Viscosity)

> 2000 consistent with turbulent flow

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6
Q

Static Compliance

A

Static compliance = Volume/Pressure = (Tidal volume delivered) / (Plateau pressure – PEEP)

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7
Q

Dynamic Compliance

A

Dynamic compliance = Volume/Pressure = (Tidal volume delivered) / (Peak pressure – PEEP)

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8
Q

Law of LaPlace

A

Pressure = (2 • Wall Tension) / (Radius)

Note: wall thickness is typically not considered for alveoli

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9
Q

Transpulmonary Pressure

A

Transpulmonary pressure = Alveolar pressure – Pleural pressure

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10
Q

Transthoracic Pressure

A

Transthoracic pressure = Pleural pressure – Atmospheric pressure

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11
Q

Predicted PaO2 by Age

A

Predicted PaO2 = 110-(age • 0.4)

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12
Q

Boyle’s Law

A

Pressure1 • Volume1 = Pressure2 • Volume2

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13
Q

Ohm’s Law

A

Pressure = Cardiac Output • Resistance

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14
Q

Myocardial Perfusion Pressure

A

MPP = Aortic diastolic pressure – LVEDP

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15
Q

LaPlace Law

A

Tension = (Pressure • Radius)/(2 • Wall Thickness)

Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved for wall tension

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16
Q

Poiseuille’s Law

A

Flow Rate = (π • Pressure • radius4)/(8 • viscosity • length)

Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved for flow.

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17
Q

Fick Principle

A

CO = VO2/(CaO2 – CmvO2)

VO2 = Oxygen consumption
CaO2 = Arterial content of oxygen
CmvO2 = Mixed venous content of oxygen
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18
Q

Consumption of Oxygen

A

VO2 = Hb • (Sata - Satmv) X 1.34 • CO

Rearranged: Satmv = Sata – [VO2/ (Hb • 1.34 • CO)]

19
Q

Arterial Content of Oxygen

A

CaO2 = [Hb • Sata • 1.34] + 0.003 • PaO2

20
Q

Respiratory Quotient

A

RQ = VCO2/VO2

VCO2 = Elimination of CO2
VO2 = Oxygen consumption
21
Q

Oxygen Delivery

A

DO2 = CaO2 • CO

CaO2 = Arterial content of oxygen

22
Q

Oxygen Extraction Ratio

A

ER = VO2/DO2

23
Q

Pulmonary Vascular Resistance

A

PVR = [(PAP-Wedge)/CO] • 80

PAP = Pulmonary Arterial Mean Pressure

24
Q

Stroke Work

A

SW = Stroke volume • mean arterial pressure

25
Q

Cardiac Index

A

CI = CO/BSA

26
Q

Systemic Vascular Resistance

A

SVR = [(MAP-CVP)/CO] • 80

27
Q

Starling Equation

A

Q = kA X [(Pc – Pi) + σ(πi-πc)]

Q = Net Fluid Filtration
k = Capillary Filtration Coefficient (of water)
A = Area of the Membrane
σ = Reflection Coefficient (of albumin)
Pc = Capillary Hydrostatic Pressure
Pi = Interstitial Hydrostatic Pressure
πi = Interstitial Colloid Osmotic Pressure
πc = Capillary Colloid Osmotic Pressure.
28
Q

Allowable Blood Loss

A

ABL = EBV X [(Hb – Minimum allowable Hb)/Hb]

EBV = Estimated Blood Volume

29
Q

Cerebral Perfusion Pressure

A

CPP = MAP – ICP

30
Q

Perfusion Pressure

A

PP = MAP – Venous Presure

31
Q

Volume of Distribution

A

VD = Dose / Concentration

32
Q

Half Life

A

Half-life = Volume of distribution / Rate of clearance

33
Q

Clearance

A

Clearance = dose / area under time concentration curve

Clearance = (Urine concentration x Urine flow) / (Plasma concentration)

34
Q

Opioid Conversions

A

Drug IV Oral

Morphine 10 mg 30 mg
Hydromorphone 1.5 mg 7.5 mg
Fentanyl 100 mcg NA
Codeine N/A 200 mg
Hydrocodone NA 30 mg
Oxycodone NA 20-30 mg

35
Q

Gas Tanks (E)

A

Gas Volume Pressure

Oxygen 625 L 2200 psig
Nitrous Oxide 1590 L 745 psig

36
Q

Incidence & Prevalence

A

Incidence = Number of occurrences / Sum of person-time at risk

Prevalence = Number of cases/ Number of individuals sampled

37
Q

Measure of Effect

A

Absolute measure of effect = Rate Difference = Rate of risk exposed – Rate of risk not exposed

Relative measure of effect = Rate Ratio = Rate of risk exposed /Rate of risk not exposed

38
Q

Sensitivity

A

Sensitivity = TP/ (TP + FN)

39
Q

Specificity

A

Specificity = TN/ (TN + FP)

40
Q

PPV

A

Positive Predictive Value = TP/ (TP + FP)

41
Q

NPV

A

Negative Predictive Value = TN/ (TN + FN)

42
Q

Odds Ratio

A

Odds Ratio = AD/BC

43
Q

Relative Risk

A

Relative Risk = [A/(A+B)] / [C/(C+D)]

44
Q

Number needed to Treat

A

NNT = 1 / ARR