Equations, Volumes and Lung Compliance Flashcards
Define Dalton’s law
Total pressure of gas mixture = Sum of each individual partial pressure
Extra info that the law gives:
Proportion (%) of gas in mixture = % of total pressure it contributes = its partial pressure
Partial pressure of a gas is directly proportional to its concentration
Define Boyle’s law
P1V1 = P2V2
At constant temp, pressure of a gas is inversely proportional to its Volume
Define Henry’s law
The amt of a gas dissolved in a liquid is proportional to the partial pressure of that gas when at equilibrium
Fick’s law tells us that diffusion increases with…?
SA increase
Membrane thickness decrease
Partial pressure gradient between outside and inside increase
Diffusion constant (D) increase : more soluble molecule, more diffusion. smaller molecule, better diffusion
What is the alveolar gas equation
PAO2 = PiO2 - PaCO2/R
aka
PAO2 = (Patm - pH2O)(FIO2) - (PaCO2/RQ)
R= the respi exchange ratio: the ratio btwn amount of CO2 produced in metabolism and O2 used
RQ= R =Respi quotient
Define Law of Laplace
P=2T/r
P=pressure
T= tension of alveolar wall= surface tension +elastic force
r= radius of alveolar wall
Define lung compliance (CL) and name its determinants
Change in lung volume caused by a given change in transpulmonary pressure. The greater the lung compliance, the more readily the lungs expand
Determinants:
1. stretchability of lung tissue: thickening would cause stretachability to decrease so less compliance
- Surface tension of air-water interfaces of alveoli: alveolar sacs surface are moist cuz they are lined w/ water. This creates surface tension which causes the alveoli to constantly shrink and resist stretching so less compliance. Expansion of lungs needs energy to overcome ST
What are surfactants and what cells produce them?
Surfactants such as Dipalmytol Lectin (DPL) and Dipalmythol Phophatidylcholine (DPPC) reduce the cohesive forces btwn H2O molecules so surface tension is decreased and lung compliance increases.
They are produced and secreted by Type II Pneumocytes
The amt of surfactant decrease when breaths are small and constant. Deep breaths stretch Type II pneumocytes and this stimulates the secretion
Define:
Inspiratory Reserve Volume (IRV)
Expiratory Reserve Volume (ERV)
Residual Volume (RV)
Inspiratory Reserve Volume (IRV): Amt of air in excess tidal inspiration/ quiet inspiration that can be inhaled w/ maximum effort
Expiratory Reserve Volume (ERV): Amt of air in excess tidal expiration/ quiet expiration that can be exhaled w/ maximum effort
Residual Volume (RV): Amt of air remaining in the lungs after max expiration. It keeps alveoli inflated btwn breaths & mixes w/ fresh air on next inspiration. Air that can’t be breathed out
Define: Vital Capacity (VC) Functional Residual Volume (FRV) Inspiration Capacity (IC) Total Lung Capacity (TLC) Tidal Volume (TV)
Vital Capacity (VC): Max air you can move in and out of lungs. Amt of air that can be exhaled w/ max effort after max inspiration. ERV +TV +IRV). Used to assess strength of thoracic muscles as well as pulmonary function
Functional Residual Volume (FRV): Amt of air remaining in lungs after normal tidal expiration (RV +ERV)
Inspiration Capacity (IC): Max amt of air that can be inhaled after a normal tidal expiration (TV +IRV)
Total Lung Capacity (TLC): Total air in lungs after a forced inspiration. Max amt of air lungs can contain (RV + VC)
Tidal Volume (TV): Amt of air inhaled or exhaled in one breath – usually 500ml a breath
Define measured volumes: FEV1 and FVC
FEV1: Forced expiratory volume in 1 second
FVC: Forced vital capcity. The total amt of air forcibly expired
What is the healthy FEV1/ FVC
Another way of asking: What percentage of Vital capacity can healthy individuals expire in 1 sec?
0.8 and above
80%
What are the FEV1, FVC and FEV1/ FVC results difference in airway obstruction and airway resistance as compared to a healthy person?
Obstruction:
FEV1 low
FVC possibly same w/ healthy
FEV1/FVC low or 70% of below
Restrictive:
FEV1 now as much as normal but not as low as obstructive
FVC lower
FEV1/ FVC possibly same as normal or a bit lesser than normal so about 75%
FVC
