lecture 18 Flashcards
What does respiratory minute volume =?
Tidal volume x respiratory rate
What is the dead space?
it is where the inhaled air that never gets to the alveoli for gas exchange
What is the value for dead space or Vd?
~150mLs
what does Va or alveolar ventilation =?
(tidal volume - dead space) x respiratory rate
What is daltons law?
In a gas mixture, each gas exerts its own individual pressure, called a partial pressure
Where is the final destination for inhaled oxygen?
capillaries
What is Fick’s law of diffusion?
F = A/T x D x (P1-P2)
What determines rate of diffusion?
surface area of membranes
thickness of membranes
pressure difference between two sides
How do gases move across the membrane between the alveoli and the capillaries?
diffusion
What does diffusion constant depend on?
Gas solubility and its molecular weight
Which diffuses faster CO2 or O2?
CO2 diffuses about 20x faster due to CO2 having a higher solubility
What creates a lot of surface area for gas exchange?
Bulbous structures of alveoli and the high density of capillaries
what is emphysema?
a disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls
What is the result of emphysema?
Reduction in surface area means less contact between the air and capillaries so oxygen exchange is decreased
What is the blood air barrier comprised of?
Alveolar and capillary walls and a fused basement membrane
What is pulmonary fibrosis?
thickening and scarring of the alveolar membranes
What is a disease that affects diffusion?
emphysema
What is a disease that affects thickness of blood air barrier?
Pulmonary fibrosis
What does PaO2 depend on?
Partial pressure of oxygen in inspires air
alveolar ventilation
oxygen consumption via blood
Why is the balance between oxygen consumption and alveolar ventilation most important?
because partial pressure of O2 inspired air is constant
What results in lower levels of oxygen in the venous blood?
High activity like exercise and increased oxygen consumption
PaCO2 depends on?
partial pressure of CO2 in inspired air
alveolar ventilation
Blood CO2 production
