CVPR Week 5: Ventilation Flashcards
Objectives
Question
How is ventilation determined?
tidal volume and frequency
What is dead space ventilation?
referred to as wasted ventilation because it doesn’t contribute to gas exchange
in the conducting zones
pharynx larynx, trachea, bronchi
Conduction zones of the airway
- Pharynx
- Larynx
- Trachea
- Bronchi
Respiratory zones of the airway
- Terminal bronchioles
- Alveolar ductts
- Alveolar sacs
- Alveoli
What is alveolar ventilation?
the fraction of tidal volume that participates in gas exchange not in the conduction zones
Breathing pattern can affect?
VD to VA ratio
dead space to the alveolar ratio
increase in frequency increases VD
increase in TV increases VA
Total Dead space AKA
Physiologic dead space
Total Dead space =
Anatomic dead space + Alveolar dead space
Physiologic dead space
anatomic dead space and alveolar dead space (where air fills the alveoli but there is no blood flow going there so ventilated but not perfused)
Partial pressure review
Bohr Equation
VD / VT = PaCO2 - PECO2
PaCO2
Where VD = dead space
VT = Tidal volume
How to calculate physiologic dead space
Alveolar ventilation equation
Question
Alveolar ventilation can be calculated from?
PCO2
Equations to know
- Alveolar ventilation equation
- Alveolar gas equation
- Oxygen content equation
- Henderson-Hasselbach equation
Interpretation of the alveolar ventilation equation
V of CO2 expired = VA x Fractional [CO2}
All the expired CO2 must come from?
must come from CO2 delivered to the alveoli from the blood
PACO2 (alveoli) in relation to PaCO2 (arteries)
What happens when VA does not match the metabolism (CO2 production)
Hypercapnia PaCO2 > 45 mmHg Hypoventilating
Hypocapnia PaCO2 < 35 mmHg Hyperventilating
Hypercapnia
Hypocapnia
