OS2 Equations Flashcards
Nernst potential
61 log [outside cell] / [ inside cell]
2 equations for MAP
- SVR x CO
2. Diastolic + 1/3 pulse pressure
2 equations for pulse pressure
- Systolic pressure - diastolic pressure
2. Stroke volume / aortic compliance
Cardiac output (2 equations)
- stroke volume x heart rate
2. O2 consumption / (O2 pulmonary vein - O2 pulmonary artery)
relationship of length and radius to resistance
increase length, increase resistance; increase radius, decrease resistance
ηL/r^4
SVR
MAP-RAP / (CO x 80)
flow = P/R R = P/flow
sometimes right atrial pressure is ignored since very small and hard to measure
tension + stress
tension = length x radius stress = (length x radius) / thickness
Flow (Q)
delta P / resistance
pressure = resistance x flow
Diffusion flow (J) how it's affected by: -thickness -area -concentration difference
[D x A (C1-C2)] / X
X= thickness D= diffusion coefficient A= area C1-C2 = concentration difference
Velocity of fluid flow
V = flow / area
Starling’s Law Equation for flow Q
Q = K [(Pc-Pi) – σ (πc –πi)]
K = filtration coefficient
Stroke work
Stroke volume x Mean arterial Pressure
Stroke volume
End diastolic volume - end systolic volume
Cardiac Efficiency
external work / internal work
internal work is a function of what type of factors?
laplace law (Regading tension)
- thickness
- radius (dilated ventricle)
- increase in pressure
increased tension –> increased internal work –> decreased cardiac efficiency
2 Equations for compliance
- dV/dP (measure of pressure change for a given change volume
- stroke volume / pulse pressure (PP = SV/compliance)
Inverse of compliance
stiffness
Ejection Fraction
Stroke volume / End diastolic volume
Clearance rate
(Ux * V) / Px
Filtered Load
GFR * Px
Excretion rate
Ux * V = FLx + S - R
Fractional Excretion
(Ux*V) / FLx
Filtration Fraction
GFR / RPF
Anion Gap
[Na] - [Cl] - [HCO3]
Net Acid Excretion
[U(NH4)V] + [U(TA)V] - [U(HCO3)*V]
Posm
2P(Na) + Urea/2.8 + Glucose/18
Volume excreted
mosm excreted / Urinary osm (mosm/L)
Oxygen dissolved in plasma
0.003(PO2)
O2 carrying capacity of Hb
1.34 ml O2
hemoglobin capacity of O2
[Hb] x carrying capacity
normal values: 15 g Hb/dl blood x 1.34 mlO2/gHb
O2 content
O2 saturation x O2 carrying capacity + amount dissolved
(Hbsatuation x 1.34 x [Hb]) + .003PaO2
when PaO2 = 100, SaO2 = 98%
relationship between oxygen capacity (O2 bound to hemoglobin) and PO2
nonlinear
Respiratory Quotient (RQ)
CO2 production/O2 consumption
Minute Ventilation (VE)
Tidal Volume x respiratory rate
Alveolar Ventilation (VA)
(Tidal Volume - Dead Space) x respiratory rate
FEV1 (forced expiatory volume of air expired in first second) is normally 75-80%, which is expressed as:
FEV1 / FVC
FVC = forced vital capacity
Alveolar Gas Equation
PAO2
PaO2 = PIO2 - (PACO2/RQ)
PIO2
FIO2(760-47mmHg)
760=Patm
47=Ph20
FIO2 = concentration of O2 (usually 21%
pCO2
(.863xCO2 produced) / Alveolar ventilation
recall: VA= (TV-DS)xRR
take away point: pCO2 decreases as alveolar ventilation increases
Recall that Fick’s law of Diffusion = [D x A (C1-C2)] / X
What is D (diffusion capacity) proportional to?
D proportional to solubility / square root (MW)
smaller MW has higher diffusion rate, and higher solubility has higher diffusion rate
Pulmonary vein [O2] is measured in _______
Pulmonary artery [O2] is measured in ______
peripheral artery
systemic mixed venous blood
Coronary perfusion pressure (pushing into heart to give O2–only occurs during diastole)
Aortic diastolic pressure - pressure drop across stenosis - LVEDP
Dead space
VD = VT x (PACO2-PECO2)/PACO2
where PECO2 is PCO2 of expired air
pCO2
CO2 produced / (TV-DS)rr
Tension
Stress
Tension = Pr Stress = Pr/2h
Oxygen uptake (2)
- Flow x (CaO2-CvO2)
where CvO2= mixed venous O2 content
- (Hbx1.34)(SaO2-SvO2) x CO
