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Physics & Equations Flashcards

1
Q

Alveolar Oxygen Equation

A 
PAO2 = FIO2 (PB-PAH2O) - (PACO2/R)
-
PAO2 = Alveolar Pressure of Oxygen
FIO2 = 21% or 0.21
PB = 760mmHg
PH2O = 47mmHg
PACO2 = 40mmHg
R = Quotient = 0.8
-
Always assume STP unless otherwise stated
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2
Q

Oxygen Consumption

A

(0.07) 7% consumption * 5,000mL/min = 350mL/min
-
Avg. for a 70K patient is about 250 mL a minute

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3
Q

Minute Ventilation

A

VE = VT * f

Minute Ventilation = Tidal Volume * Breaths Per Minute

VE = Minute Ventilation
VT = Tidal Volume
f = Flow
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4
Q

Oxygen Content Equation (CaO2)

A

CaO2 = 1.36 x Hb x Sat. + .0031 x PaO2

Sat. = %/100
PaO2 = variable provided in question
Hb = variable provided in question
CaO2 normal values are between 16 - 22 mlO2/dl

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5
Q

Lung, Thorax Compliance Calculation

A

CLT = Delta V / Delta PAW

CLT - Compliance of the Lung and Thorax in ml/cmH2O
Delta V - Change in volume of Thorax
Delta PAW - Change in airway pressure
Normal Compliance is 200 for each CL and CT

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6
Q

Individual Compliances

A

1/CLT = 1/CL + 1/CT

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7
Q

Metabolic Jumping Off Point (oxygen consumption)

A

VO2 = Weight in Kg^0.75 * 10

10 is the assumed RR

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8
Q

Respiratory Quotient

A

R = VCO2/VO2

VCO2 = VO2 * R

R = 0.8 for a metabolically normal euthermic patient
VCO2 = 250ml/min in an euthermic patient
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9
Q

Fractional Concentration

A

Fx = Px / Ptot

Fx = Fraction of Concentration
Px = Partial Pressure
Ptot = Pressure Total
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10
Q

Ideal Alveolar Pressure for CO2 in a eucapnic patient

A

40mmHg

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11
Q

Pressure of all gases in the Alveoli under dry conditions

A

Ptot = Pbar (dry)

737mmHg (Bar, Atlanta) - 47mmHg (PH2O @ 37°C)

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12
Q

Alveolar Ventilation

A 
Px/Ptot = Vx/Vtot
or
Paco2/Pbar = Vaco2/Va
Partial Alveolar (CO2)/Pressure Total (atm) = Vol (CO2)/Vol total
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13
Q

Pressure

A

P = F/a

F = Force
a = area (pi * r^2)
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14
Q

1 mmHg is equal to

A

1.36 cmH2O

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15
Q

760 mmHg is equal to

A

101.33 Kpa
1013.3 mbar
1033.6 cmH2O
14.7 psi
1 atm

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16
Q

1 atm is equal to

A

101.33 Kpa
1013.3 mbar
760 mmHg
1033.6 cmH2O
14.7 psi

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17
Q

101.33 Kpa is equal to

A 
1013.3 mbar
760 mmHg
1033.6 cmH2O
14.7 psi
1 atm
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18
Q

14.7 psi is equal to

A 
760 mmHg
101.33 Kpa
1013.3 mbar
1 atm
1033.6 cmH2O
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19
Q

1033.6 cmH2O is equal to

A 
1 atm
760 mmHg
101.33 Kpa
1013.3 mbar
14.7 psi
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20
Q

Pressure in a tube (Laplace)

A

Ptube = T/r

T = Tension
r = radius
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21
Q

Pressure in a sphere (Laplace)

A

Psphere = 2T/r

T = Tension
r = radius
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22
Q

Equation for Flow

Equation for Resistance

A

F = Q/t

Q = Quantity (volume or mass)
t = time

Flow is directly proportional to pressure. The ratio of pressure to flow is resistance, R = P/Q

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23
Q

Mean Blood Pressure

A

(S-D)/3 + D

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24
Q

Body Surface Area

A

Height^0.725 * Weight^0.425 * 0.007184

Height in cm
Weight in Kg
BSA in m^2

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25
Q

How is viscosity is measured

A

Pascal Seconds

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26
Q

How to calculate flow with viscosity variable

A

Q = [(pi)(r^4) (delta P)] / 8nL

Delta P = Pressure Loss
n = viscosity
Q = volumetric flow rate
L = Length of pipe

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27
Q

How to calculate pressure with viscosity variable

A

Delta P = 8QnL / (pi)(r^4)

Delta P = Pressure Loss
n = viscosity
Q = volumetric flow rate
L = Length of pipe

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28
Q

Reynolds Number

A

R = vpd / n

v = velocity
p (rho) = density
d = diameter
n = viscosity

If the Reynolds number is greater than 2000 turbulent flow is more likely to occur. Below 2000 results in more laminar flow.

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29
Q

Entrainment Ratio

A

Entrained Flow / Driving Flow

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30
Q

Calculate FiO2 w/ Entrainment Ratio of 9:1 with 2L O2

A

FiO2 = [1 * 2 liters of O2 + .21 * 18 liters of air] / 20

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31
Q

FiO2 Equation

A

FiO2 = [1 * liters of O2 + .21 * liters of air] / total flow

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32
Q

What units are used to measure Tension?

A

newtons per square meter

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33
Q

Volume of Conducting Airways (Deadspace)

A

2.2 mL/Kg (or) 1 mL/lb

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34
Q

Ventilation of Anatomic Deadspace

A

Ventilation = Volume * f

f = respiratory rate

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35
Q

Minute Ventilation

A

MV = (Alveolar Ventilation) + (Deadspace Ventilation)

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36
Q

1 inch is equal to

A

2.54 cm

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37
Q

Charles’ Law of Gas Constants

A

PV = nRT
(or)
V/T = nR/P ===> V1/T1 = V2/T2

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38
Q

Don’s Law (barf)

A

P1/T1 = P2/T2

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39
Q

STP

A

Standard Temperature and Pressure

T = 273 K, 0°C
P = 760 mmHg
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40
Q

RTP

A

Room Temperature and Pressure

T = 293 K, 20°C
P = 760 mmHg
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41
Q

BTP

A

Body Temperature and Pressure

T = 310 K, 37°C
P = 760 mmHg
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42
Q

Volume and Pressure and Color of an O2 E-Cylinder

A 
Volume = 660
Pressure = 2000psi
Color = Green
43
Q

Volume and Pressure and Color of an N2O E-Cylinder

A 
Volume = 1590
Pressure = 750
Color = Blue
44
Q

Volume and Pressure Color of an Air E-Cylinder

A 
Volume = 625
Pressure = 1800
Color = Yellow
45
Q

Boyle’s Law of Gas Constants

A

P1V1 = P2V2

Used to determine the remaining gas in a tank

46
Q

Flow

Time Constants

A

Volume/Time

Volume/Flow

47
Q

Hematocrit

A

Red Cell Volume/Blood Volume

Hematocrit of 40 means that 40% of the blood is red blood cells

48
Q

Estimated Blood Volume (EBV) Constants

A

80-90 mL/Kg for Infants
70-75 mL/Kg for Males
60-65 mL/Kg for Females

49
Q

Estimated Red Cell Volume (ERCVi)

A

= Estimated Blood Volume (EBV) x Hematocrit Initial (Hct(i))

50
Q

Estimated Red Cell Volume Accepted (ERCVa)

A

= Estimated Blood Volume (EBV) x Hematocrit accepted (Hcta)

51
Q

How to calculate Red Cell Volume Loss (RCVL)

A

ERCVi - ERCVa

52
Q

How to calculate the Estimated Blood Loss Accepted (EBLa)

A

[(Hcti - Hcta)/Hct avg] * EBVi = EBLa

53
Q

Blood Loss Replacement Values

A

Whole Blood, FFPs, RBCs = 1:1

Colloids [Albumin, Hydroxyethyl starch (Hespan, Hextend)] = 1:1

Crystalloids (NS, LR, D5W, Plasmalyte, etc.) = 3:1

54
Q

Values for Time Constants

A

Each time constant will reduce the remaining amount to 36.78% of the previous value. After 2 time constants there will be a remainder of 13.52% of the initial value.

e^3 = 4.98% remaining or 95.02% complete
e^4 = 1.83% remaining or 98.17% complete
e^5 = 0.7% remaining or 99.3% complete
55
Q

Circulatory Time Constants

A

Based on the fact that the heart can circulate TBV in 1 minute (blood volume/cardiac output) = 1, time constants can be represented in intervals of 1 minute

56
Q

Pulmonary Time Constants

A

Pulmonary time constants are also 1 minute based on the fact that you are dividing the total volume by the minute ventilation, which comes out to 6/6 = 1

57
Q

Circuit Time Constants

A

Circuit Volume = 5L
Time constant = Volume / Flow

At 1 L/min, time constant is 5/1 = 5 minutes
At 2 L/min, time constant is 5/2 = 2.5 minutes

Increasing sevo from 2% to 3% will give you a concentration of 2.63% of sevo in the circuit after 1 time constant

58
Q

Pulmonary time constants with “wash in” curve function

A

1 - e^-x = 1 - (1/e^x)

59
Q

Definition of Diffusion

A

The process by which the molecules of a substance transfer through a layer or area such as the surface of a solution. Diffusion can also refer to the spreading of gas molecules to evenly fill a space or container.

60
Q

Fick’s Law of Diffusion

A

States that the rate of diffusion of a substance across unit area (such as a surface or membrane) is proportional to the concentration gradient..

(larger gradient = faster diffusion)

61
Q

Examples of conditions where the use of N2O might be hazardous

A 
Air Embolism
Pneumothorax
Acute Intestinal obstruction
Intracranial Air
Pulmonary Air Cysts
Intraocular Air Bubbles
Tympanic Membrane Grafting
62
Q

Graham’s Law

A

States that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.

Smaller molecular weight compounds diffuse faster
Larger molecular weight compounds diffuse slower

63
Q

Henry’s Law

A

States that at a particular temperature, the amount of a given gas dissolved in a given liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid.

64
Q

Effect of Temperature on Solubility

A

As temperature increases, solubility decreases

65
Q

Bunsen Solubility Coefficient

A

The volume of gas, corrected to STP, which dissolves 1 unit volume of the liquid at the temperature concerned, where the partial pressure of the gas above the liquid is 1 standard atmosphere pressure.

66
Q

Ostwald Solubility Coefficient

A

The volume of gas which dissolves in 1 unit volume of the liquid at the temperature concerned.

This is independent of pressure, unlike the Bunsen coefficient

67
Q

Vapor pressure in mmHG of agents at 20°C

A 
Nitrous Oxide = 38517
Halothane = 243
Isoflurane = 238
Desflurane = 664
Sevoflurane = 160
68
Q

Vapor concentration in volume % of agents at 20°C

A 
Nitrous Oxide = ( )
Halothane = 32
Isoflurane = 31
Desflurane = 87
Sevoflurane = 21
69
Q

MAC of agents in 100% O2

A 
Nitrous Oxide = 105
Halothane = 0.75
Isoflurane = 1.15
Desflurane = 6.0 - 7.25
Sevoflurane = 1.6 - 2.6
70
Q

MAC Pressures

A

Take the MAC % and divide by 100, then multiply by 760

71
Q

Blood/Gas Coefficients

A 
Nitrous Oxide = 0.47
Halothane = 2.4
Isoflurane = 1.4
Desflurane = 0.42
Sevoflurane = 0.65
72
Q

Three factors affecting anesthetic uptake in lungs

A

Solubility of agent in blood
Alveolar Blood Flow/Cardiac Output
Difference in partial pressure between venous blood and alveolar gas

73
Q

Ways to increase the rate of induction

A

Increase concentration of agent

Augmented inflow effect (second gas effect)

74
Q

Potency

A

Potency is directly related to the fat/gas coefficient, however MAC% is also a relative indication of potency. The lower the MAC% the higher the potency will be.

75
Q

MAC awake

A

0.3 - 0.4 MAC

76
Q

MAC Bar (blocks adrenergic response)

A

1.5 - 2 MAC

77
Q

MAC 1.3

A

ED95, which means that it will prevent response to stimuli in 95% of all patients in relation to volatiles

78
Q

MAC (minimum alveolar concentration)

A

The alveolar concentration that prevents movement in 50% of patients (ED50) in response to a standardized stimulus (eg, surgical incision).

79
Q

Water weight % at birth and 1 year

A

75% at birth

65% after 1 year

80
Q

Water weight % of adult men and women

A 
Men = 60%
Women = 50%

The higher fat content in females decreases water content. For the same reason, obesity and advanced age further decrease water content.

81
Q

Adult daily water intake and output

A

Intake matches output
Intake = 2500 mL
Output = 1500 mL urine, 400 mL skin evaporation, 400 mL respiration, 100 mL sweat, 100 mL feces

82
Q

Body fluid storage

A

Intracellular fluid = 40%

Extracellular fluid = 20% (interstitial = 15%, Intravascular = 5%)

83
Q

Exchange of fluid between compartments depends on

A

Permeability of that substance
Concentration gradient
Pressure difference
Electrical potential for charged substances

84
Q

BMI

A

Weight in KG / Height in m^2

85
Q

Scalar

A

Representable by position on a scale or line and only having magnitude

86
Q

Vector

A

A quantity possessing both magnitude and direction, represented by an arrow. The arrow indicates the direction of the quantity. The length of the arrow is proportional to the magnitude.

87
Q

Acceleration

A

delta V / delta T

Change in velocity over change in time

88
Q

(Devine) Ideal Body Weight Male

A

W = 50 + (H (in) - 60) x 2.3

89
Q

(Devine) Ideal Body Weight Female

A

W = 45.5 + (H (in) -60) x 2.3

90
Q

(Broca) Ideal Body Weight

A

Height in cm - 100

91
Q

Volume of a cylinder

A

pi * r^2 * length

92
Q

Volts, Amps, Ohms

A 
Volts = Unit of measure for driving force of electrons
Amps = Unit of measure for flow of electrons
Ohms = Unit of measure for resistance to flow of electrons
93
Q

Ohms Law

A

V = I * R

94
Q

Power

A

Measured in Watts

P = I * V = Watts

95
Q

Cardiac Output

A

CO = Stroke Volume * Heart Rate

96
Q

FiO2 with supplemental oxygen

A

0.21 + 3% per liter/min of supplemental oxygen

97
Q

Half Life

A

equal to 0.69th of a time constant

half life = 50% wash out
time constant = 63% wash out

98
Q

Pressure

A

P = Flow / Resistance

similarly, V = I * R (current * resistance)

99
Q

Resistance

A

R = Pressure/Flow = Pressure/ (Volume/Time) = PT/V

100
Q

Time Constant

A

Equal to volume undergoing washout / flow of perfusing fluid

101
Q

BMI Classifications

A 
Severe Starvation = less than 16
Under Weight = 16 - 18.49
Normal = 18.5 - 25
Over Weight = greater than 25 - 30
Obese = greater than 30 - 40
Morbidly Obese = greater than 40
102
Q

Functional Residual Capacity (FRC)

A

35 ml/kg

103
Q

I to E ratio calculations

A

Divide seconds in a minute (60) by breaths per minute to obtain the seconds per breath. Add the total units of the ratio (1:2 –> 1+2=3). Divide seconds per breath by the total of units to obtain the inspiration time. Multiply this value by the expiration ratio to get the expiration time.

104
Q

Pleural Pressure equation

A

Pleural Pressure = AW pressure x CL/(CL + CT)

Equations (1 decks)

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