Ventilation Flashcards
Ratio between alveolar ventilation and pulmonary blood flow
~1:1
Alveolar ventilation = 5.25 L/min
Pulm blood = 5L/min
Tidal volume #
500 mL
Anatomic dead space volume
150 mL (1mL per 1lb)
Alveolar gas volume
3L
Pulmonary capillary blood volume
70 mL
Total ventilation #
7.5 L/min
Frequency
15/min
Total lung capacity (TLC or Vt) = ?
Vital capacity (VC) + Residual Volume (RV)
Inspiratory Capacity (IC) + Functional Residual Capacity (FRC)
Insp reserve volume (IRV) + Tidal volume (TV) + Exp reserve volume (ERV) + residual volume (RV)
Vital capacity =
Max inspiration - max expiration
Tital volume
Under normal/rest conditions
Resting volume
After expiration during rest
Total ventilation =
Tidal volume x respiratory rate
Normal = 500mL x 15breathes/min
= 7,500mL/min
Alveolar ventilation
Since anatomic dead space is about 150mL…
Alveolar ventilation = (500-150mL) x 15br/min
= 5,250mL/min
Overall:
Alveolar ventilation = total ventilation - dead space ventilation
Tidal volume is mixture of gases of what ‘areas’
Gas from anatomic dead space
And
Alveolar gas…
CO2 levels in alveolar gas and blood are…
Same
Because CO2 has a higher diffusion constant than O2
Measuring [CO2] in expired gas
Alveolar vent. = (CO2 vent/CO2 press) x constant
CO2 ventilation = alv vent x fractional conc of CO2
If alveolar ventilation is halved…and CO2 production stays the same
Then…
Alveolar and arterial pCO2 will double
Inverse relationship
As alveolar ventilation increases….
The alveolar P-CO2 decreases
Bringing alveolar P-O2 closer to inspired P-O2
What does Fowler’s method measure
Anatomic dead space
What does Bohr method measure
Physiologic dead space
This is increased with pathology
Regional differences in ventilation
Upper < middle < lower lung
Due to gravity
