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8 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Alveolar Gas Equation
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PAO2 = FlO2 x (Pb - PH2O) - PaCO2/R
R = respiratory quotient is generally about 0.8 Pb (atm) = 760mmHg PH2O = 47mmHg (water moisture in mouth) FlO2 = 21% if not augmented by supplement |
This equation estimates the Alveolar O2 concentration from the measurable arterial O2 levels
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Bohr Equation (Estimate Dead Space)
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Vd/Vt = (PACO2 - PECO2) / (PACO2)
PACO2 is about equal to PaCO2. This is the case for CO2 but NOT O2 PECO2 - the expired CO2 |
Uses CO2 washout to measure indirectly the volume of the lungs
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Alveolar Ventilation
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PACO2 = PaCO2 = V'CO2 / (K*V'A)
V'A = alveolar ventilation is indirectly related to PaCO2 |
THis equation is important because it show how arterial CO2 is indirectly related to alveolar ventilation
double V'A and halve PaCO2 |
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Minute Ventilate
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Minute ventilation = Resp rate * tidal volume
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Thus there are 2 ways to maintain the ventilation needed.
- alter resp rate - alter tidal volume |
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Fick Equation
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Flow Gas = [Area*(MW^0.5)*Solubility*Driving Pressure ] / (membrane thickness)
- Solubility (Higher = better flow) this is CO2 - Driving Pressure (O2 = 100 to 40 & CO2 = 40 to 45) |
Each of these variables are manipulated for the lung to maximize gas transport
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Laplaces Law (justify surfactant)
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Pressure = 2T / R
R - radius T - tension in the walls |
Thus the small radii alveoli will require higher pressure to keep patent with equal tension
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Compliance (elastance)
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Compliance = dVolume / dPressure
Elastance is the inverse |
Something compliant will increase volume easily for a given pressure.
Something with high elastance will require more pressure to increase its volume (it will be less compliant) |
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Respiratory Quotient
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R = CO2 output / O2 input
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R is usually 0.8
R changes based on anaerobic or aerobic metabolism High fat diet will decrease CO2 output and the respiratory quotient |
