Ventilation Flashcards
Minute ventilation units
TV X RR
(Volume/ breath) x (frequency of breaths/minute)
Normal tidal volume= 500 ml/breath
Normal frequency= 15 breaths / min
Minute ventilation= 500 x 15= 7,500 ml/min
Where does the tidal volume go?
Normal tidal volume = 500 ml
150 ml -> anatomic dead space
The rest goes into alveolar gas
What is anatomic dead space roughly equivalent to?
Ideal body weight
Dead space ventilation
Breaths/min X volume of dead space
What is total ventilation - dead space ventilation?
Alveolar ventilation
Normal values: FRC
Composed of what two values
Functional residual capacity
3 L
Expiratory reserve volume 1.5 L
Residual volume 1.5 L
Normal values: IC
Composed of what two values
Inspiratory capacity
3 L
IRV 2.5 L
TV 0.5 L
Normal values: Vital capacity
4.5 L
Normal Values: Total Lung Capacity
6 L
Which values cannot be measured?
RV
FRC= ERV + RV
TCL= VC + RV (TLC= IC + FRC)
Volume of air during normal quiet breathing
TV
Air that can be inhaled after a normal inhalation
IRV
Air that can be exhaled after a normal exhalation
ERV
Air that remains in the lung after a maximal expiration
RV
Air that can be inhaled after a normal exhalation
IC
Air that remains after a normal exhalation
FRC
ERV + RV
Maximum air that can be inhaled
VC
Air in the lungs after a maximal inhalation
TLC
How does the helium dilution technique work?
C1 V1 = C2 (V1 + V2)
Have a known concentration and volume of helium in a container
Hook a patient up to the container, ask the patient to breath in and out
After a while, concentration of helium in container will decrease and level off
(this is at FRC)
Measure the new concentration of helium in container and solve for volume V2 (lung FRC)
With this you can measure RV (FRC - ERV)
To calculate TLC
(RV + IC)
How does the body-box plethysmography work?
Boyle’s lay
P1V1 = P2V2
What is the effect of increased depth of breathing vs increased rate of breathing on alveolar ventilation?
Tidal volume X RR = minute ventilation
Dead space ventilation = 150 ml X RR
Alveolar ventilation is minute ventilation - dead space ventilation
Therefore, increasing RR will cause more volume to go to the dead space vs alveolar space.
Increasing depth of breathing and decreasing RR will maximize alveolar ventilation bc less will go to the dead space.
What is alveolar dead space?
Not anatomic, only happens in disease conditions.
Ventilated bu underperfused alveoli (no gas exchange)
Negligible in healthy people
What conditions are associated with alveolar dead space
Low CO
Pulm embolism
(Little or no blood flow causes the vessel to shrivel up)
Partial pressure of arterial CO2 is proportional to:
What can you exchange elimination of CO2 with?
CO2 production/ CO2 elimination
Alveolar ventilation bc Alveolar CO2 ~ arterial CO2
Alveolar ventilation equation
Minute vent - dead space vent
(RR X Vt) - (RR X Vd)
RR X Vt (1 - Vd/Vt)
Increased dead space will result in
Decreased alveolar ventilation
Restriction can be diagnosed by
Reduced TLC
