Formula's Flashcards by Chiara Debie

Dalton’s law

Ptotal = P1 + P2

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Boyle’s law

P1V1 = P2V2

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Henry’s law

Concentration = P (soluble)

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Fick’s law of diffusion

Vgas = Area/Thickness * diffusion constant * (P1 - P2)

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Diffusion constant

D = soluble/molecular weight

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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

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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

F = delta P/ R

R = resistance

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Oxygen delivery index (DO2) (2)

1) CO * CaO2

CO = cardiac output
CaO2 = arterial oxygen content

2) CI (ml/kg/min) * CaO2/100

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Arterial oxygen content (CaO2)

CaO2 = [1.34 * SaO2 * Hb] + [PaO2 * 0,003]

SaO2 = saturation
Hb = hemoglobin (g/dL)

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P (A) O2 (alveolar oxygen pressure) - shortened

P (A) O2 = 150 - PaCO2

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Oxygenation index (OI)

OI = MAP * FiO2 * 100/PaO2

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Oxygen saturation index (OSI)

OSI = MAP * FiO2 * 100/SpO2

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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)

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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

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Minute ventilation (Ve)

Ve = Vt * RR

Vt = Tidal volume
RR = respiratory rate

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Tidal volume (Vt)

Vt = Vd + Va

Vd = dead space ventilation
Va = alveolar ventilation

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Alveolar ventilation (Va)

Va = Ve - Vd

Ve = minute ventilation
Vd = dead space ventilation

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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

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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

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Pressure gradient between RA and RV in systole

pressure gradient = 4 velocity [m/s]2

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Flow rate in high flow

Flow rate = Patient’s minute volume = respiratory rate * tidal volume

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Equation of Motion

Pvent + Pmuscles = Elastance * volume + resistance * flow

Pvent = pressure generated by ventilator
Pmuscles = pressure generated by inspiratory muscles

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Serum osmolality

Osmolality = 2 [Na] + (BUN/2.8) + (glucose/18)

BUN in mg/dL
Glucose in mg/dL

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Free water deficit

Free water deficit (L) = (current [Na]/ normal [Na] - 1) * 0.6 * body weight

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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)

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

Free water effect dogs

0.25([Na] - mid-normal [Na])

Free water effect cats

0.22([Na] - mid-normal [Na])

Corrected chloride

measured [Cl] * (mid-normal [Na]/ measured [Na])

Chloride effect

mid-normal [Cl] - corrected [Cl]

Lactate effect

-1 * [lactate]

Sum of effects in semiquantitative approach

free water effect + chloride effect + phosphorus effect + albumin effect + lactate effect

Unmeasured ion effect

base excess - sum of effects

Fractional excretion of sodium (FeNa)

FeNa = 100 * (Urine [Na] * Plasma [Creatinine] / Plasma [Na] * Urine [Creatinine])

Transtubular potassium gradient

(Urine [K] * Plasma osmolality) / (Urine osmolality * Plasma [K])

Urinary free water clearance

urine volume * (1 - (Urine [Na] + Urine [K]) / Serum [Na])

CVC collapsibility

CVC CI = CVCd max – CVCd min / CVCd max

RER

70*(BW^0,75 ) /24 h

Dehydratation deficit

body wt (kg) * % dehydration (as decimal) * 1000 (ml/L)

Effective osmolality

2*[Na] + [glucose (mg/dl) / 18]

Corrected sodium

Na(meas) + 1.6 ([measured glucose – 100] / 100)

amended insulin/glucose ratio (AIGR)

(insulin 100) / (plasma glucose - 30)

Monroe-Kelly doctrine

Vintracranial = V brain + V CSF + V blood + V mass/lesion

Dog plasma volume

(1 – hematocrit) * (body weight [kg] * 85 ml/kg) HCT in decimals

Cat plasma volume

(1 – hematocrit) * (body weight [kg] * 55 ml/kg) HCT in decimals

Mean arterial blood pressure

1) Diastolic P + (systolic - diastolic) / 3 2) Diastolic P + 1/3 Pulse pressure

Pulse pressure variation (PPV)

PPV (%) = 100 * (PPmax - PPmin) / [(PPmax + PPmin) / 2]

Systemic vascular resistance

1) SVR = (MAP - CVP) / CO 2) SVR (mmHg/ml/kg/min) = (MAP - CVP) / CI (ml/kg/min) 3) SVR (dynes * sec/cm^5 ) = ([MAP - CVP] * 79.9) / CI (L/min/m^2)

Cardiac output (Fick method)

CO = VO2 / (CaO2 - CvO2)

Functional SO2

[(HbO2)/(HbO2 + HHb)] * 100

Fractional SO2

[(HbO2)/(HbO2 + HHb + COHb+1 MetHb)] * 100

Colloid osmotic pressure

COP = 2.1P + 0.16P^2 + 0.009P ^3 P = Plasma protein

Abdominal perfusion pressure

mean arterial pressure (MAP) - intraabdominal pressure (IAP)

Filtration gradient

glomerular filtration pressure - proximal tubule pressure = MAP - 2*IAP

Urine volume on POCUS

Vurine (ml) = (L * W * (dl + DT)/2) * 0.52 L = length of the bladder (longitudinal) W = width of the bladder (transverse) dl = depth of the bladder (longitudinal) DT = depth of the bladder (transverse)

cardiac index (CI) (2)

1) CI (ml/kg/min) = CO (ml/min) / BW (kg) 2) CI (L/m^2/min) = CO (L/min) / body surface area (m^2)

Oxygen consumption index (from Fick equation)

VO2 (ml/kg/min) = CI (ml/kg/min) * (CaO2- CmvO2 ) / 100

Oxygen extraction ratio

OER (%) = (CaO2 - CmvO2) / CaO2

Pulmonary vascular resistance (2)

1) PVR (mmHg/ml/kg/min) = (PAP - PAOP) / CI (ml/kg/min) 2) PVR (dynes*sec/cm^5) = ([PAP - PAOP] * 79.9) / CI (L/min/m^2) PAP = pulmonary artery pressure PAOP = pulmonary artery occlusion pressure

Stroke volume (SV) (2)

1) SV (ml/beat/kg) = CI (ml/kg/min) / HR 2) SV (ml/beat/m^2) = CI (ml/min/m^2) / HR

Fractional shortening

FS = [LVIDd - LVIDs] / LVIDd * 100

Ejection fraction

EF = (LVVd - LVVs) / LVVd * 100

Static compliance

C stat = VT / (Pplat - PEEP)

Dynamic compliance

C dyn = VT / (PIP - PEEP)

Inspired resistance

RI = (PIP - Pplat) / VT

Transpulmonary pressure

TPP = Palv - Ppl

Driving pressure

deltaP = Pplat - PEEP

Osmole gap

measured osmolality - calculated osmolality

Total body water

0 6 * BW (kg)

Laplace law

P = 2t / r t = wall thickness r = radius

Modified Bernoulli equation

deltaP = 4*V^2

Poiseuille’s law

Resistance = (8 *n * l) / (2*pi*r^4) n = viscosity l = lenght r = radius

Reynolds number

Re = (D* rho* V) / n D = diameter rho = density V = velocity n = viscosity

Wall stress

sigma = liniary correlated to (P * R) / 2t sigma = wall stress P = pressure R = resistance t = thickness

Compliance

Delta V / Delta P

Elastance

Delta P / Delta V

Total dead space

anatomical + apparatus + alveolar dead spaces

Alveolar-arterial PO2 gradient

PAO2 = (Patm – PH2O) x FiO2 – (PaCO2/0.8)

Velocity in blood vessel

Blood flow (F) / Area of blood vessel (A)

Formula's Flashcards

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