Equation Review

Question 1

Sensitivity

Answer 1

TP/(TP+FN)

A/(A+C)

1- false negative rate

Question 2

Specificity

Answer 2

TN/(TN+FP)

D/(B+D)

1- false positive rate

Question 3

Positive predictive value

Answer 3

TP/(TP+FP)

A/(A+B)

Question 4

Negative predictive value

Answer 4

TN/(FN+TN)

D/(C+D)

Question 5

Odds ratio (for case control studies)

Answer 5

(a/c)/(b/d) = ad/bc

Question 6

Relative risk

Answer 6

(a/[a+b])/(c/[c+d])

Question 7

Attributable risk

Answer 7

(a/(a+b)) - (c/(c+d))

Question 8

Number needed to treat

Answer 8

1/absolute risk reduction

Question 9

Number needed harm

Answer 9

1/attributable risk

Question 10

Hardy-Weinberg equilibrium

Answer 10

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

Question 11

Volume of distribution

Answer 11

Vd = amount of drug in the body/plasma drug concentration

Question 12

Half-life

Answer 12

(0.693 x Vd)/CL

Question 13

Drug clearance

Answer 13

CL = rate of elimination of drug/plasma drug concentration = Vd x Ke (elimination constant)

Question 14

Loading dose

Answer 14

LD = (Cp x Vd)/F

Question 15

Maintenance dose

Answer 15

D = (Cp x CL x t)/F … t = dosing interval

Question 16

Cardiac output

Answer 16

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

Question 17

Mean arterial pressure

Answer 17

MAP = COxTPR … MAP = 2/3(diastolic)+1/3(systolic)

Question 18

Stroke volume

Answer 18

EDV-ESV

Question 19

Ejection fraction

Answer 19

EF = SV/EDV = (EDV-ESV)/EDV

Question 20

Resistance

Answer 20

driving pressure (ΔP)/flow (Q) = (8η x length)/πr^4

Question 21

Net filtration pressure

Answer 21

Pnet = [(Pc-Pi) - (πc-πi)] …. Jv = net fluid flow = (Kf)(Pnet)

Question 22

Renal clearance

Answer 22

Cx = UxV/Px

Question 23

Glomerular filtration rate

Answer 23

GFR = Uinulin x V/Pinulin = Cinulin … GFR = Kf[(Pg - Pb)-(πg - πb)]

Normal: 100 ml/min

Question 24

Effective renal plasma flow

Answer 24

ERPF = Upah x (V/Ppah) = Cpah

Underestimates true renal plasma flow by 10%

Question 25

Renal blood flow

Answer 25

RBF = RPF/(1-Hct)

Question 26

Filtration fraction

Answer 26

FF = GFR/RPF

Normal: 20%

Question 27

Henderson-Hasselbach equation (for extracellular pH)

Answer 27

pH = 6.1 + log ([HCO^3-)/0.03PCO2)

Question 28

Winters formula

Answer 28

PCO2 = 1.5[HCO^3-] + 8 +/- 2

Predicted resp compensation for a simple metabolic acidosis.

If measured PCO2 differs significantly from the predicted, then a mixed acid base disorder is likely present.

Question 29

Physiologic dead space

Answer 29

Vd = Vt x (PaCO2 - PECO2)/PaCo2

Question 30

Pulmonary vascular resistance

Answer 30

PVR = (Ppulm artery - Pleft atrium)/CO

Question 31

Alveolar gas equation

Answer 31

PAO2 = PIO2 - (PaCO2/R)

Question 32

Attributable Risk Percent

Answer 32

Measure of impact of risk factor

(RR-1)/RR

Question 33

Absolute Risk Reduction

Answer 33

Event Rate (Control)-Event Rate (Treatment)