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8/17/2019 M5 Equations
1/15
M5 BOARD REVIEW Equations
www.m5boardreview.com
Respiratory
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Comprehensive Anesthesiology Question Bank
PAO2= FI
O2P ATM
– P H 2O
( ) – PaCO2 / RQ
Alveolar Gas Equation
PAO2
PaCO2
FI O2
P ATM
P H 2O
RQ
==
=
=
=
=
Alveolar partial pressure of oxygen
Arterial partial pressure of CO2
Inspired O2
Atmospheric pressure
Saturated vapor pressure
Respiratory Quotient
Respiratory Physiology: Q14
Basic Pulmonary Physiology: Q7 Q’s
Dead Space (Bohr Equation)
==
Arterial partial pressure of oxygen
Partial pressure of CO2 from all
expired gases
Basic Pulmonary Physiology: Q14 Q’s
Shunt Equation
=
=
=
Post-capillary blood oxygen content
(typically assumed to be the
Saturation of haemoglobin utilizing
the PAO2 • haemoglobin
concentration • 1.34)
Arterial Hbsat • Hb • 1.34
Mixed venous Hbsat • Hb • 1.34
Basic Pulmonary Physiology: Q17 Q’s
Ventilation/Perfusion Index (ratio)
Basic Pulmonary Physiology: Q17 Q’s
V D
V T
=
Pa CO2
– P E CO2
Pa CO2
Pa CO2
P E CO2
Qshunt
Q total =
(Cc’O2 - CaO2 )
(Cc’O2 - CmvO2)
Cc’O2
CaO2
CmvO2
VQI =1– Arterial Hbsat( )
1– Mixed Venous Hbsat( )
Ohm’s Law
Basic Pulmonary Physiology: Q17 Q’s
Pressure Gradient = Air Flow Airway Resistance
p1
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Respiratory
Comprehensive Anesthesiology Question Bank
Airway Resistance for Laminar Flow(Poiseuille’s Law)
Respiratory Physiology: Q7 Basic Pulmonary Physiology: Q5 Q’s
Law of LaPlace
Wall thickness is typically notconsidered for alveoli
Basic Pulmonary Physiology: Q5 Q’s
Reynold’s Number
>2000 consistent with turbulent flow
Respiratory Physiology: Q7 Respiratory Physiology: Q8 Basic Pulmonary Physiology: Q4
Q’s
Time Constant
Basic Pulmonary Physiology: Q5 Q’s
Note:
Laminar FlowResistance
=8 Length • Viscosity of gas( )
Radius4( )
R =Velocity Density Diameter( )
Viscosity
Pressure =Radius
TC = Compliance Resistance
Static Compliance
Basic Pulmonary Physiology: Q33 Q’s
Static compliance =Volume
Pressure =
Tidal volume delivered
Plateau pressure – PEEP( )
Dynamic Compliance
Basic Pulmonary Physiology: Q33 Q’s
Dynamic compliance =Volume
Pressure =
Tidal volume delivered
Peak pressure – PEEP( )
2 • Wall Tension
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Respiratory
Comprehensive Anesthesiology Question Bank
Transpulmonary Pressure
ICU: Advanced Cardiopulmonary: Q1Q’s
Transpulmonary pressure Alveolar pressure – Pleural pressure=
Transthoracic Pressure
ICU: Advanced Cardiopulmonary: Q1Q’s
Transthoracic pressure Pleural pressure – Atmospheric pressure=
Predicted PaO2 by Age
Special Situations: Q12 Respiratory Physiology: Q6
Q’s
Predicted PaO2 = 110-(age • 0.4)
Boyle’s Law
Basic Cardiac Physiology: Q12 Q’s
Pressure1 • Volume1 = Pressure2 • Volume2
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Respiratory
Comprehensive Anesthesiology Question Bank
Henry’s Law
Partial Pressure = k • C
Henderson-Hasselbach
pH = pK + log[HCO3-/ (0.03 • PaCO2)]
k = Henry’s Law Constant
C = Concentration of dissolved gas
Ohm’s Law
Pressure = Cardiac Output • Resistance
Cardiac Physiology: Q14 Q’s
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Cardiac
Comprehensive Anesthesiology Question Bank
Myocardial Perfusion Pressure
MPP = Aortic diastolic pressure – LVEDP
Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved
for wall tension
LaPlace Law
Tension = (Pressure • Radius)/(2 • Wall Thickness)
Basic Cardiac Physiology: Q12 Q’s
Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved for flow.
Poiseuille’s Law
Flow Rate = (π • Pressure • radius4)/(8 • viscosity • length)
Basic Cardiac Physiology: Q12 Q’s
Cardiac Physiology: Q23 Q’s
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Cardiac
Comprehensive Anesthesiology Question Bank
Fick Principle
CO = VO2/(CaO2 – CmvO2)
CO = Cardiac Output
VO2 = Oxygen consumption
Sata = Arterial saturation of haemoglobin
Satmv = Mixed venous saturation of haemoglobin
Hb = Haemoglobin
CO = Cardiac Output
VO2 = Oxygen consumption
CaO2 = Arterial content of oxygen
CmvO2 = Mixed venous content of oxygen
Consumption of Oxygen (not including O2 dissolved in blood for simplicity)
VO2 = Hb • (Sata - Satmv) X 1.34 • CO
Rearranged : Satmv = Sata – [VO2/ (Hb • 1.34 • CO)]
ICU Principles: Q1ICU Principles: Q2 ICU Principles: Q19
Q’s
ICU Principles: Q1Q’s
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Cardiac
Comprehensive Anesthesiology Question Bank
Arterial Content of Oxygen
CaO2 = [Hb • Sata • 1.34] + 0.003 • PaO2
CaO2 = Arterial content of oxygen
CO = Cardiac Output
Sata = Arterial saturation of haemoglobin
Pa O2 = Partial pressure of oxygen in arterial blood
Oxygen Delivery
DO2 = CaO2 • CO
ICU Principles: Q1Q’s
SatmvCO2 = CO2 saturation in mixed venous blood
Elimination of CO2
VCO2 = Hb X SatmvCO2 • CO
ICU Principles: Q1Q’s
VCO2 = Elimination of CO2
VO2 = Oxygen consumption
Respiratory Quotient
RQ = VCO2/VO2
ICU Principles: Q15 Q’s
ICU Principles: Q1Q’s
Oxygen Extraction Ratio
ER = VO2/DO2
VO2 = Oxygen consumption
DO2 = Delivery of oxygen
ICU Principles: Q1ICU Principles: Q3 Q’s
Cardiac Output
CO = Stroke Volume • Heart Rate
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Cardiac
Comprehensive Anesthesiology Question Bank
Stroke Volume
SV = End-diastolic volume – End-systolic volume
MAP = Mean Arterial Pressure
CVP = Central Venous Pressure
CO = Cardiac output
Systemic Vascular Resistance
SVR = [(MAP-CVP)/CO] • 80
Basic Cardiac Physiology: Q13 Q’s
PAP = Pulmonary Arterial Mean Mressure
CO = Cardiac Output
Pulmonary Vascular Resistance
PVR = [(PAP-Wedge)/CO] • 80
ICU Principles: Q6 Q’s
Stroke Work
SW = Stroke volume • mean arterial pressure
Basic Cardiac Physiology: Q29 Q’s
Basic Cardiac Physiology: Q29 Q’s
Cardiac Index
CI = CO/BSA
CO = Cardiac Output
BSA = Body Surface Area
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Cardiac
Comprehensive Anesthesiology Question Bank
Perfusion Pressure
PP = MAP – Venous Presure
Allowable Blood Loss
ABL = EBV X [(Hb – Minimum allowable Hb)/Hb]
MAP = Mean arterial pressure
ICP = Intracranial pressure
Cerebral Perfusion Pressure
CPP = MAP – ICP
Clinical Neurophysiology: Q2 Clinical Neurophysiology: Q3 Q’s
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.
Starling Equation
Q = kA X [(Pc – Pi) + σ(πi-πc)]
Basic Cardiac Physiology: Q30 Q’s
EBV = Estimated Blood Volume
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Equipment
Comprehensive Anesthesiology Question Bank
Endotracheal Size (for children)
Size = 4 + (Age/4)
Endotracheal Depth
Depth = 12 + (Age/2), or 3 • ETT size
Pediatrics: Q4 Q’s
Gas Tanks (E)
Gas Volume Pressure
Oxygen 625 L (US) 2200 psig
Nitrous Oxide 1590 L 745 psig
Equipment: Q1Equipment: Q2 Q’s
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Statistics
Comprehensive Anesthesiology Question Bank
Incidence = Number of occurrences / Sum of person-time at risk
Prevalence = Number of cases/ Number of individuals sampled
Incidence & Prevalence
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
Measure of Effect
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Statistics
Comprehensive Anesthesiology Question Bank
Sensitivity = TP/ (TP + FN)
Specificity = TN/ (TN + FP)
Positive Predictive Value = TP/ (TP + FP)
Negative Predictive Value = TN/ (TN + FN)
Disease Screening
Statistics: Q17 Statistics: Q18 Q’s
Has Disease No Disease
Positive Test True Positive (TP) False Positive (FP)
Negative Test False Negative (FN) True Negative (TN)
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Statistics
Comprehensive Anesthesiology Question Bank
Odds Ratio = AD/BC
Relative Risk = [A/(A+B)] / [C/(C+D)]
Disease Screening
Statistics: Q16 Q’s
Has Disease No Disease
Exposed A B
Not Exposed C D
ARR = Absolute Risk Reduction = Control event rate – Experimental event rate
Number needed to Treat
NNT = 1 / ARR
Statistics: Q19 Q’s