Equations Flashcards
Altitude effect on PaO2
(Barometric pressure 1-47)(FiO2) =(barometric pressure 2-47 (FiO2)
A-A gradient (pAO2-paO2)
[FiO2x (barometric pressure-47)- (paCO2/0.8)] -paO2
Alveolar minute ventilation
(TV-dead space) x RR
Anion gap
NA - (cl + bicarb)
Cardiac output
HR x SV
SBP/ total peripheral vascular resistance
Cerebral blood flow
Cerebral perfusion pressure /cerebral vascular resistance
Cerebral perfusion pressure
Mean arterial pressure- intracranial pressure
Conpliance
Change in Volume /change in pressure
Physiologic dead space (Bohr)
[(Arterial CO2 -expired CO2)/arterial CO2] x TV
Elastance
Change in pressure/change in volume
FENa or urinary fractional secretion or Na:
[Urine Na] x [plasma creatinine] /
[urine creatinine] x [plasma Na]
X100
Laminar flow
Change in pressure /Resistance
Resistance
8 x viscosity x length / pie x radius^4
Glomerular filtration rate
0.45 x height (cm) / plasma creatinine
(For premature infants use 0.33 instead of 0.45)
Hardy Weingburg equilibrium
P + q =1
P^2 + 2pq + q^2 = 1
P = population frequency of dominant allele
q = population frequency of recessive allele
Henderson- Hasselbach equation
[H+] = 24 x CO2 / bicarbonate
Laplace law
Distending pressure = 2 x surface tension/ radius
Mean Airway Pressure
K (PIP-PEEP) x [i-time / (I-time + e-time)] + peep
Minute ventilation
TV x RR
Osmolality
2(plasma Na) + (glucose/18) + (BUN/2.8)
O2 content of blood
[1.34 x Hb x O2 sat] + [0.003 x PaO2]
Oxygen consumption (Fick principle)
CO x (arterial O2 content - venous O2 content)
CO x (1.34) x Hb x (arterial O2 Sat -venous O2 Sat)
Oxygen delivery
Cardiac output x O2 content
Oxygenation index
MAP x FiO2 (full like 100)/
PaO2
Ponderal index
Weight (grams)/
(Crown-heel^3)
X100
Power
Work x frequency
Pulmonary to systemic blood flow ratio
Aorta O2 Sat - superior vena cava O2 Sat/
Pulm venous O2 Sat- pulm artery O2 sat