lecture 1 - intro to respiratory physiology Flashcards
What is ventilation?
The process of moving air in and out of the lungs to supply O2 and remove CO2 from the alveoli via a process called bulk flow
What is Dalton’s Law of partial pressures?
Pressure(gas) = Fraction(gas) * Pressure(total)
In Dalton’s Law, what value do we normally assign to Pressure(total)?
Atmospheric pressure = 760mmHg
What effect does water vapour have on the pressure of inspired oxygen?
Reduces the PO2 (by about 10mmHg)
How does the pressure of inspired oxygen change with increasing altitude?
The fraction of oxygen of the total pressure remains the same, but the total partial pressure drops, leading to a proportionate drop in the PO2
What is the normal value for alveolar partial pressure of CO2?
40mmHg
What is the normal value for alveolar partial pressure of O2?
100mmHg
What is the equation for pulmonary ventilation?
V = frequency of breaths *tidal volume
What is the equation for alveolar ventilation?
V = frequency of breaths * (tidal volume - dead space)
Which breathing pattern is most effective in terms of ventilating the alveoli (increases VA)?
Deep, slow breathing
What is the typical pulmonary blood flow per minute?
5000mL (same as the amount of blood pumped around the body by the heart each minute, because the circuits are in series
What does Fick’s Law explain?
gas exchange across semi-permeable membranes
What are the factors that affect gas exchange (Fick’s Law)?
Surface area, pressure difference across membrane, thickness
What are the 5 mechanisms that can cause arterial hypoxaemia (low oxygen in blood due to issues in the lungs)?
- Reduced Pressure of inspired oxygen
- Hypoventilation
- Impaired diffusion
- Shunt
- Ventilation-perfusion (V/Q mismatch)
What are the 2 forms in which oxygen is carried in the blood?
Dissolved, combined with Hb
