Respiration Lecture 06: Ventilation, Work and Breathing Strategies Flashcards
alveolar ventilation
how pumping actions affect PO2 and PCO2 in the alveolus
ventilation
process by which the concentrations of O2 and CO2 are established
minute ventilation =
breathing frequency X tidal volume. The amount of gas moved into and out of lung over time (L/min)
2 major divisions of the lung
1) gas exchange area (respiratory zone)
2) gas conducting zone
Which divisions of lung are ventilated and which participate in gas exchange?
Both ventilated; only respiratory zone part. in gas exchange
VO2
rate that O2 is removed from the alveolus
VCO2
rate CO2 is released into alveolus
concentrations of alveolar gases compared to air
lower O2, higher CO2 than air
Dead space volume (VD)
volume of air in conducting zone. Considered “wasted ventilation”
Vt = what two volumes?
VD + VA (dead space volume + alveolar volume)
Alveolar ventilation (V’A)
portion of the minute ventilation that is involved directly in refreshing the alveolar gas. V’A = VA * f . Directly related to concentrations of O2 and CO2 in the blood.
Increased VD for same Vt –> V’A?
Decrease
Most effective way to increase V’A?
Increase Vt and keep VD constant
What does “arterial” refer to?
blood coming into L heart that’s been through the lung and participated in gas exchange
What is rate at which CO2 is removed from the lung a fx of?
V’A and V’CO2
Increased V’CO2 –> PACO2?
increases
Increased V’A –> PACO2?
Decreases
Review graph on page 37
:)
Effect of FRC on oscillation of PCO2 and PO2
Decreased FRC leads to more rapid oscillations. FRC helps to stabilize O2 and CO2 concentrations over the total breathe
What is the maximum level PAO2 can reach?
PiO2
Hyperventilation
Breathing so much (increasing V’A) that alveolar PCO2 drops below 40mmHg
Hypoventilation
Decreasing alveolar ventilation so that alveolar PCO2 increases above 40mmHg
V’A indirectly effects ARTERIAL O2 and CO2
:)
end-expiratory sample
measurement of the PO2 and PCO2 in the last gas to leave the mouth at the end of an expiration. Contains alveolar gas without non-exchanged dead space air.
Work
moving mass over a distance
respiratory work =
area under pressure-volume curve
inspiratory work
deviation to the right of the straight line on P/V curve during inspiration necessary to overcome resistance
expiratory work
deviation to the left of the line during expiration on P/V curve necessary to overcome resistance
mechanical work
work used to overcome the lung elastic recoil during inspiration. Stored as potential energy and is recovered during expiration
what is elastic work related to?
volume
what is resistive work related to?
flow and changes in frequency
Total work =
elastic work + resistive work
How do most animals minimize work for breathing?
adjust BOTH Vt and f to minimize work and optimize V’A
What requires more work, increasing f or increasing Vt? Which produces greatest change in V’A?
increasing Vt. Increasing Vt has greatest effect on increasing V’A
horse breathing strategy
splits Vt above and below FRC to avoid large active inspiratory volumes and decrease amt. of elastic muscle work needed. Have stiff chests. Also uses gait to assist breathing by inspiring during swing phase and expiring during forelimb strike.
