Flashcards in Equations Deck (26)

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1

## Sensitivity

###
sensitivity = TP/(TP + FN) = 1 - FN rate

(TP= true positive; FN = false negative)

2

## Specificity

### specificity = TN/(TN + FP) = 1 - FP rate

3

## Positive Predictive Value

### PPV = TP/(TP+FP)

4

## Negative Predictive Value

### NPV=TN/(TN+FN)

5

## Relative Risk

### R=[a/(a+b)]/[c/(c+d)]

6

## Attributable Risk

###
AR=[a/(a+b)] - [c/(c+d)]

*AR - difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure (ie smoking causes 1/3rd of cases of pneumonia)

7

## Number needed to treat =

###
1/absolute risk reduction

*Absolute risk reduction - reduction in risk associated with a treatment compared to a placebo

8

## Number needed to harm =

### 1/attributable risk

9

## Hardy-Weinberg equilibrium =

###
p^2 + 2pq + q^2 = 1

p+q = 1

*p^2 - frequency of homozygosity for allele p

*q^2 - frequence of homozygosity for allele q

*2pq - frequency of heterozygosity (carrier frequency)

10

## Henderson-Hasselbach equation =

### pH = pKa + log [HCO3-]/(0.3XPCO2)

11

## Volume of distribution

### Vd= (amount of drug in body)/(plasma drug concentration)

12

## Clearance

### CL = rate of elimination of drug/plasma drug concentration

13

## Half-Life

### t1/2 = (0.7XVd)/CL

14

## Loading dose

###
LD = Cp X (Vd/F)

*Cp=target plasma concentration

*F=Bioavailability = fraction of administered drug that reaches circulation (if IV, F=100%; if oral, F=% that survives first pass in liver or gut)

15

## Maintenance dose

### MD = Cp X (CL/F)

16

## Cardiac output

###
CO = rate of O2 consumption/ (arterial O2 content - venous O2 content)

-AND-

CO = stroke volume X heart rate

17

## Mean Arterial Pressure

###
MAP = CO X total peripheral resistance

-AND-

MAP = 1/3 systolic + 2/3 diastolic

18

## `Stroke Volume

### SV = end diastolic volume - end systolic volume

19

## Ejection Fraction

### EF = (Stroke volume/End diastolic volume) X 100

20

## Resistance

###
R = driving pressure / flow

= (8 X viscosity X length) / (pi X r^4)

21

## Net filtration pressure

###
Pnet = [(Pc-Pi) - (rc - ri)]

*Pc=capillary pressure --> pushes fluid out of capillary

*Pi=interstitial fluid pressure --> pushes fluid into capillary

*rc= (r should be sigma) plasma colloid osmotic pressure --> pushes fluid into capillary

*ri= interstitial fluid colloid osmotic pressure --> pushes fluid out of capillary

22

## Glomerular filtration rate

###
GFR= Uinulin X (V/Pinulin) = Cinulin

= (urine concentration X urine flow) / Plasma concentration

*Uinulin = urine inulin

*Pinulin = plasma inulin

*Cinulin = clearance of inulin

*V = urine flow rate

-AND-

GFR = Kf [(PGC - PBS) - (rGC - rBS)]

*GC = glomerular capillary

*BS = Bowman's space

*rBS - normally equals 0

*** Normal GFR = 100 mL/min

23

## Effective renal plasma flow

### ERPF = Upah X (V/Ppah) = Cpah

24

## Renal blood flow

### RBF = RPF / (1-Hct)

25

## Filtration fraction

### FF = GFR / RPF

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