Ventilation and perfusion at the level of lung Flashcards
Total ventilation
7500 ml/min
Anatomic dead space
150 ml
Alveolar ventilation
4 L/min
Alveolar gas volume
3000 ml
Volume of blood in pulmonary capillaries
70 ml
Pulmonary blood flow
5000 ml/min
What happens if left lung is ventilated but not perfused and right lung is perfused but not ventilated
V/Q = 1 but there is NO GAS EXCHANGE
=> V/Q must be matched at level of alveolar unit for normal gas exchange
Increase perfusion, increase ventilation and vice versa
Are all regions of lung ventilated equally
NO
Order of zones of lung in terms of decreasing ventilation
- Lower zone
- Middle zone
- Upper zone
Normal pulmonary capillary perfusion
5 L/min
What is normal V/Q (V/P)
4/5 = 0.8
What sort of area is the upper zone
Non-dependent (usually > 1)
What sort of area is the lower zone
Dependent area (usually < 1)
P and V of alveoli at the apex
Alveoli are UNDERPERFUSED and OVERVENTILATED
P and V of alveoli at the base
Alveoli are OVERPERFUSED and UNDERVENTILATED
V/P at apex
3.4
V/P at base
0.63
PO2 at base
PO2 at apex
PO2 difference
89
132
40
Difference in ventilation between apex and base
APEX = 0.24 L/min
BASE = 0.82 L/min
Difference in blood flow between apex and base
APEX = 0.07 L/min
BASE = 1.29 L/min
Consequence of high V/P ratio at apex
high PO2 and low PCO2
(opposite at the base)
Relationship between ventilation and perfusion
A local decrease in perfusion matches local decrease in ventilation - diversion of blood flow and air to healthy areas of lungs
Blood pH
Formula
What does body buffer to a pH of
7.35 - 7.45
pH = 6.1 + log [HCO3-]/0.03 x [PCO2]
pH = log kidney/lung
Body buffers to a pH of 7.38
What is PaCO2
Partial pressyre of CO2 dissolved in arterial plasma
40 mmHg
