Equations and Numbers Flashcards
Oxygen content
CaO2= (O2Sat x Hg x 1.34) + (PaO2 x 0.003)
SvO2
SvO2= SaO2 - [VO2/(CO x Hb x 13)]
Shunt fraction
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
LaPlace equation
T= 1/2 PR
Hagen-Poiseuille
Flow (v) = (pi* r^4 * change in pressure) / 8L*viscosity
Dead space formula
Vd/Vt = (PaCO2 - PECO2) / PaCO2
PaO2 formula
PaO2 = (Pb - 47)FiO2 - (PaCO2 /R)
Oxygen delivery formula
DO2 = Cardiac index x CaO2
Acute normovolemic hemodilution
volume to be removed = EBV x (Initial hg - final hg)/ (average of initial and final hg)
Cerebral blood flow
50 ml/100g tissue/min
Critically low CBF
20ml/100g tissue/min
Lowest level of CBF for cellular survival
10 ml/100g tissue/ min
PVR
PVR (dyne*sec/cm^2)= [(Mean PA - PCWP)/CO] x 80
Formula for power (statistics)
1 - beta
Sensitivity
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)
Specificity
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
Positive predictive value
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
Negative predictive value
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
Hypothesis testing for categorical data
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
Hypothesis testing for numerical data
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
Further analyses for regression methods
Correlation: correlation coefficients, pearson’s, spearman’s
Regression: Simple multiple logistic modelling
Further analyses on Longitudinal studies
Repeated measures
time series
survival analyses
MAC for volatiles: Halothane Isoflurane NO2 Desflurane Sevoflurane
Halothane 0.75 Isoflurane 1.15 NO2 105 Desflurane 5.7 Sevoflurane 2.0
B/G Solubility
Halothane Isoflurane NO2 Desflurane Sevoflurane
- 3 Halothane
- 4 Isoflurane
- 47 NO2
- 42 Desflurane
- 6 Sevoflurane
Vapor pressure
Halothane Isoflurane NO2 Desflurane Sevoflurane
Halothane 240 Isoflurane 238 NO2 --- Desflurane 665 Sevoflurane 160-200
How do you calculate amount of nitrous left in a tank?
You must weigh it. 44g/mole, 22.4 L/mole
Formula for time constant, and what does it represent?
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.