Equations and Numbers

Question 1

Oxygen content

Answer 1

CaO2= (O2Sat x Hg x 1.34) + (PaO2 x 0.003)

Question 2

SvO2

Answer 2

SvO2= SaO2 - [VO2/(CO x Hb x 13)]

Question 3

Shunt fraction

Answer 3

Qs/Qt = (CcO2 - CaO2)/ (CcO2- CvO2)

CcO2 - content pulm capillary blood
CaO2 = content arterial blood
CvO2 = content mixed venous blood
normal shunt fraction is 0.1

Question 4

LaPlace equation

Answer 4

T= 1/2 PR

Question 5

Hagen-Poiseuille

Answer 5

Flow (v) = (pi* r^4 * change in pressure) / 8L*viscosity

Question 6

Dead space formula

Answer 6

Vd/Vt = (PaCO2 - PECO2) / PaCO2

Question 7

PaO2 formula

Answer 7

PaO2 = (Pb - 47)FiO2 - (PaCO2 /R)

Question 8

Oxygen delivery formula

Answer 8

DO2 = Cardiac index x CaO2

Question 9

Acute normovolemic hemodilution

Answer 9

volume to be removed = EBV x (Initial hg - final hg)/ (average of initial and final hg)

Question 10

Cerebral blood flow

Answer 10

50 ml/100g tissue/min

Question 11

Critically low CBF

Answer 11

20ml/100g tissue/min

Question 12

Lowest level of CBF for cellular survival

Answer 12

10 ml/100g tissue/ min

Question 13

PVR

Answer 13

PVR (dyne*sec/cm^2)= [(Mean PA - PCWP)/CO] x 80

Question 14

Formula for power (statistics)

Answer 14

1 - beta

Question 15

Sensitivity

Answer 15

The probability that if a disease is present, the test will be positive.

           disease / no disease pos test    a               b neg test    c                d

a/ (a+c)

Question 16

Specificity

Answer 16

The probability that if the disease is absent, the test will be negative.

d/ (b+d)
pos test neg test
disease a b
no disease c d

Question 17

Positive predictive value

Answer 17

The probability that if the test is positive, the disease is present.

a /( a+b)
Disease no disease
test positive a b
test negative c d

Question 18

Negative predictive value

Answer 18

The probability that if the test is negative, the disease is absent

d/ (c+d)

           disease  no disease test pos    a             b test neg    c             d

Question 19

Hypothesis testing for categorical data

Answer 19

2 categories, 1 group: z test
2 categories, 2 groups, paired McNemar’s
2 categories, 2 groups, independent: Chi square, or Fisher’s exact
More than 2 groups, or more than two categories: Chi-squared

Question 20

Hypothesis testing for numerical data

Answer 20

1 group: one sample t test, sign test
2 groups, paired: Paired t-test, wilcoxon signed ranks test, sign test
2 groups, independent: unpaired t-test, wilcoxon rank sum test
More than 2 groups: One way ANOVA, Kruskal- Wallis test

Question 21

Further analyses for regression methods

Answer 21

Correlation: correlation coefficients, pearson’s, spearman’s
Regression: Simple multiple logistic modelling

Question 22

Further analyses on Longitudinal studies

Answer 22

Repeated measures
time series
survival analyses

Question 23

MAC for volatiles:
Halothane
Isoflurane
NO2
Desflurane 
Sevoflurane

Answer 23

Halothane 0.75
Isoflurane 1.15
NO2 105
Desflurane 5.7
Sevoflurane 2.0

Question 24

B/G Solubility

Halothane
Isoflurane
NO2
Desflurane 
Sevoflurane

Answer 24

2. 3 Halothane
3. 4 Isoflurane
4. 47 NO2
5. 42 Desflurane
6. 6 Sevoflurane

Question 25

Vapor pressure

Halothane
Isoflurane
NO2
Desflurane 
Sevoflurane

Answer 25

Halothane 240
Isoflurane 238
NO2 ---
Desflurane 665 
Sevoflurane 160-200

Question 26

How do you calculate amount of nitrous left in a tank?

Answer 26

You must weigh it. 44g/mole, 22.4 L/mole

Question 27

Formula for time constant, and what does it represent?

Answer 27

From the standpoint of the circuit, Volume/flow. From the standpoint of the lungs, FRC/ minute ventilation. It takes 3 time constants to achieve a 95% change in volatile concentration.