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Flashcards in Equations Deck (26)
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1
Q

Sensitivity

A

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

TP= true positive; FN = false negative

2
Q

Specificity

A

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

3
Q

Positive Predictive Value

A

PPV = TP/(TP+FP)

4
Q

Negative Predictive Value

A

NPV=TN/(TN+FN)

5
Q

Relative Risk

A

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

6
Q

Attributable Risk

A

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
Q

Number needed to treat =

A

1/absolute risk reduction

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

8
Q

Number needed to harm =

A

1/attributable risk

9
Q

Hardy-Weinberg equilibrium =

A

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
Q

Henderson-Hasselbach equation =

A

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

11
Q

Volume of distribution

A

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

12
Q

Clearance

A

CL = rate of elimination of drug/plasma drug concentration

13
Q

Half-Life

A

t1/2 = (0.7XVd)/CL

14
Q

Loading dose

A

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
Q

Maintenance dose

A

MD = Cp X (CL/F)

16
Q

Cardiac output

A

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

-AND-

CO = stroke volume X heart rate

17
Q

Mean Arterial Pressure

A

MAP = CO X total peripheral resistance

-AND-

MAP = 1/3 systolic + 2/3 diastolic

18
Q

`Stroke Volume

A

SV = end diastolic volume - end systolic volume

19
Q

Ejection Fraction

A

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

20
Q

Resistance

A

R = driving pressure / flow

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

21
Q

Net filtration pressure

A

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
Q

Glomerular filtration rate

A

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
Q

Effective renal plasma flow

A

ERPF = Upah X (V/Ppah) = Cpah

24
Q

Renal blood flow

A

RBF = RPF / (1-Hct)

25
Q

Filtration fraction

A

FF = GFR / RPF

26
Q

physiologic dead space

A

VD = VT X (PaCO2 - PeCO2)/PaCO2