Respiratory Physiology
Embryology
Pharynx > Larynx > Trachea > Primary bronchi > Secondary bronchi > Tertiary bronchi > Bronchioles > Terminal Bronchioles > respiratory Bronchioles > Alveola
Bronchioles defined by lack of cartilage
Alveolar development is completed by 3y
High ventilation superiorly
High perfusion inferiorly
VQ ratio highest superiorly, lowest inferiorly
Elastance = resistant to deformation (dP/dV)
Elastic recoil = ability to return to resting state
Compliance is deformability (inverse of Elastance) = dV/dP
(Think balloon not straw (no airway resistance) fill it, if elastic lots of pressure, if compliant little. So if high pressure = high elastance (so high P on top), low compliance ( so high P on bottom), low pressure = low elastance to low P on top, high compliance so low p on bottom)
Resistance = amount of pressure required to generate flow
Poiseuille’s law (laminar flow) = R = 8lη / 𝜋r4
Alveolar air equation = PAO2 = ((Baro-PH2O) x FiO2) - (PACO2/R)
Pharynx > Larynx > Trachea > Primary bronchi > Secondary bronchi > Tertiary bronchi > Bronchioles > Terminal Bronchioles > respiratory Bronchioles > Alveola
Bronchioles defined by lack of cartilage
Alveolar development is completed by 3y
High ventilation superiorly
High perfusion inferiorly
VQ ratio highest superiorly, lowest inferiorly
Elastance = resistant to deformation (dP/dV)
Elastic recoil = ability to return to resting state
Compliance is deformability (inverse of Elastance) = dV/dP
(Think balloon not straw (no airway resistance) fill it, if elastic lots of pressure, if compliant little. So if high pressure = high elastance (so high P on top), low compliance ( so high P on bottom), low pressure = low elastance to low P on top, high compliance so low p on bottom)
Resistance = amount of pressure required to generate flow
Poiseuille’s law (laminar flow) = R = 8lη / 𝜋r4
- l is length, η is viscosity, and r is the radius
- r is radius, v is velocity, d is density, and η is viscosity
Alveolar air equation = PAO2 = ((Baro-PH2O) x FiO2) - (PACO2/R)
- A = Alveolar, a = arterial
- R = respiratory quotient (generally assumed to be 0.8
- PACO2 usually substituted for PaCO2
- Sea level = 760mmHg
- PiO2 = (Barometric pressure - water pressure) x FiO2
- PH2O = 47 generally