Formula's Flashcards
Dalton’s law
Ptotal = P1 + P2
Boyle’s law
P1V1 = P2V2
Henry’s law
Concentration = P (soluble)
Fick’s law of diffusion
Vgas = Area/Thickness * diffusion constant * (P1 - P2)
Diffusion constant
D = soluble/molecular weight
Starling-Landis equation
Jv = Lp * A * [(Pmv - Pint) - sigma(d) (pi(p) - pi(int))]
Jv = microvascular filtration rate
Lp = hydraulic conductivity (measure water permeability)
A = surface area
P mv = hydrostatic pressure microvessels
P int = hydrostatic pressure interstitium
sigma (d) = osmotic reflection coefficient
pi (p) = colloid osmotic pressure plasma
pi (int) = colloid osmotic pressure interstitium
Ohm’s law
Ql = (Pint + Ppump - Psv)/Rl
Ql = lymph flow
Pint = hydrostatic pressure interstitium
P pump = effective driving pressure generated by cyclic intrinsic contraction and extrinsic compression of lymphatic vessels
Psv = systemic venous pressure
Rl = resistance to lymph flow
Oxygen delivery index (DO2) (2)
1) CO * CaO2
CO = cardiac output
CaO2 = arterial oxygen content
2) CI (ml/kg/min) * CaO2/100
Arterial oxygen content (CaO2)
CaO2 = [1.34 * SaO2 * Hb] + [PaO2 * 0,003]
SaO2 = saturation
Hb = hemoglobin (g/dL)
P (A) O2 (alveolar oxygen pressure) - shortened
P (A) O2 = 150 - PaCO2
Oxygenation index (OI)
OI = MAP * FiO2 * 100/PaO2
Oxygen saturation index (OSI)
OSI = MAP * FiO2 * 100/SpO2
P (A) O2 (alveolar oxygen pressure) - full version
P (A) O2 = (Pbar - Ph2o) * FiO2 - (PaCO2/RQ)
Pbar = atmospheric pressure
Ph2o = partial pressure of water
RQ = respiratory quotient (0.8)
Venous admixture expressed as percent of cardiac output (Qs/Qt)
Qs/Qt = (CcO2 - CaO2)/(CcO2 - CvO2)
Qs = shunt fraction
Qt = cardiac output
CcO2 = oxygen content of end-capillary blood
CaO2 = oxygen content of arterial blood
CvO2 = oxygen content of mixed venous blood
Minute ventilation (Ve)
Ve = Vt * RR
Vt = Tidal volume
RR = respiratory rate
Tidal volume (Vt)
Vt = Vd + Va
Vd = dead space ventilation
Va = alveolar ventilation
Alveolar ventilation (Va)
Va = Ve - Vd
Ve = minute ventilation
Vd = dead space ventilation
Bohr’s equation (4)
1) Vt * Fe = Va * Fa
Vt = tidal volume
Fe = CO2 in exhaled gas
Va = alveolar volume
Fa = CO2 in alveolus
2) Vd/Vt = (Fa - Fe)/Fa
Vd = dead volume
3) Vd/Vt = (P(A)CO2 - PeCO2)/P(A)CO2
P(A)CO2 = partial pressure of CO2 in alveolus
PeCO2 = Partial pressure of CO2 in expired air
4) Vd/Vt = (PaCO2 - PeCO2)/PaCo2
PaCO2 = arterial partial pressure of CO2
Alveolar ventilation equation
P (A) CO2 = directly proportional to ( vCO2 /V(A)) * k
vCO2 = amount of CO2 produced by metabolism
V(A) = alveolar ventilation
k = 0,863
Pressure gradient between RA and RV in systole
pressure gradient = 4 velocity [m/s]2
Flow rate in high flow
Flow rate = Patient’s minute volume = respiratory rate * tidal volume
Equation of Motion
Pvent + Pmuscles = Elastance * volume + resistance * flow
Pvent = pressure generated by ventilator
Pmuscles = pressure generated by inspiratory muscles
Serum osmolality
Osmolality = 2 [Na] + (BUN/2.8) + (glucose/18)
BUN in mg/dL
Glucose in mg/dL
Free water deficit
Free water deficit (L) = (current [Na]/ normal [Na] - 1) * 0.6 * body weight
Sodium deficit
Sodium deficit = (target [Na] - patient [Na]) * 0.6 * body weight
Henderson-Hasselbalch equation
pH = 6.1 + log [HCO3] / (0,03 * pCO2)
6.1 is the pKa in body fluids
0.03 is the solubility coefficient for carbon dioxide in
plasma
Anion gap
Anion gap = [Na] + [K] - ([HCO3] + [Cl])
Strong ion difference
Strong ion difference = (sodium + potassium) - (chloride)
Albumin effect in SID approach
(measured albumin * 10 * [(0.123 * pH) -
0.631])
Phosphorus effect in SID approach
(measured phosphorus * 0.323 * [0.309 *
pH - 0.469])
Total weak acid concentration (Atot)
Atot = albumin effect + phosphorus effect
Strong ion gap
[SID - (bicarbonate + Atot)]
Simplified SIG dogs
SIG simplified = [albumin] * 4.9 – AG
Simplified SIG cats
SIG simplified = [albumin] * 7.4 - AG