Equation Review Flashcards
Specificity
Specificity = TN/(TN+FP)
Sensitivity
Sensitivity = TP/(TP+FN)
Positive predictive value (PPD)
PPD = TP/(TP+FP)
Negative predictive value (NPV)
NPV = TN/(TN+FN)
Odds ratio
Odds ratio = (a/c)/(b/d) = (ad)/(bc)
*For case-control studies
Relative risk
Relative risk = [a/(a+b)]/[c/(c+d)]
Attributable risk
Attributable risk = a/(a+b) - c/(c+d)
Number needed to treat
1/(absolute risk reduction)
Number needed to harm
1/(attributable risk)
Body mass index (BMI)
BMI = (weight in kg)/(height in meters)^2
Hardy-Weinberg equilibrium
p^2 + 2pq + q^2 = 1
p + q = 1
Volume of distribution
Vd = (amount of drug in the body)/(plasma drug concentration)
Half-life
t1/2 = (0.7✖️Vd)/CL
Drug clearance
CL = (rate of elimination of drug)/(plasma drug concentration) = Vd✖️Ke *Ke = elimination constant
Loading dose
LD = Cp✖(️Vd/F)
- Cp = target plasma concentration
- F = bioavailability
Maintenance dose
MD = Cp✖(️CL/F)
- Cp = target plasma concentration
- F = bioavailability
Cardiac output
CO = rate of O2 consumption/(arterial O2 content - venous O2 content) CO = stroke volume✖️heart rate
Mean arterial pressure
MAP = cardiac output✖️total peripheral resistance MAP = (2/3)diastolic + (1/3)systolic
Stroke volume
SV = CO/HR = EDV - ESV
Ejection fraction
EF = SV/EDV = (EDV - ESV)/EDV
Resistance
Resistance = (deltaP)/Q = [8(viscosity)✖️length]/(pi✖️radius^4)
- deltaP = driving pressure
- Q = flow
Net filtration pressure
Pnet = [(Pc - Pi) - (oncotic capillary pressure - oncotic interstitial pressure)]
Jv = net fluid flow = (Kf)(Pnet)
Renal clearance
Cx = (UxV)/Px
Glomerular filtration rate
GFR = (U_inulin✖️V)/P_inulin = C_inulin GFR = Kf[(Hydrostatic pressure of glomerular capillary - hydrostatic pressure of Bowman's space) - (oncotic pressure of glomerular capillary - oncotic pressure of Bowman's space)]
Effective renal plasma flow
ERPF = U_PAH✖️(V/P_PAH) = C_PAH
Renal blood flow
RBF = RPF/(1-Hct)
Filtration fraction
FF = GFR/RPF
Henderson-Hasselbalch equation
For extracellular pH
pH = 6.1 + log([HCO3-]/0.03PCO2)
Physiologic dead space
V_D = V_T✖️[(PaCO2 -PECO2)/PaCO2]
- V_T = tidal volume
- PECO2 = expired air PCO2
Pulmonary vascular resistance
PVR = (P_pulm art - P_L atrium)/cardiac output
Alveolar gas equation
PAO2 = PIO2 - (PaCO2/R)
- PAO2 = alveolar PO2
- PIO2 = PO2 in inspired air
- PaCO2 = arterial PCO2
- R = respiratory quotient = CO2 produced/O2 consumed (~0.8)
