Ventilation Flashcards
static volumes are measured with a
spirometer
tidal volume
volume of air entering or leaving the lungs during a single breath
- includes volume that fills alveoli and volume that fills the airways
inspiratory reserve volume
additional volume inspired above tidal volume
- used in exercise
expiratory reserve volume
additional volume expired below tidal volume
residual volume
volume of gas left in lungs after maximal forced expiration
inspiratory capacity
tidal volume + inspiratory reserve volume
functional residual capacity
- volume of air in the lungs at the end of a normal passive expiration (or normal tidal volume)
- Expiratory reserve volume + residual volume
- **resting volume of lungs
vital capacity
- volume expired after maximal inspiration
- VC= inspiratory capacity + expiratory resperve volume
- VC= tidal volume + inspiratory reserve volume + expiratory resperve volume
vital capacity increases with? decreased with?
- increases
- sex (M>F)
- body size
- physical conditioning
- decreases
- age
total lung capacity
- maximal volume of air that the lungs can hold
- TLC= vital capacity + residual volume
functional residual capacity (FRC)
volume remaining in the lungs after a normal expiration
- resting volume of lungs
- can not be measured by spirometery
normal residual volume/total lung capacity
less than or equal to 0.25
*volume of air trapped in the lungs in 25% of the total lung volume
obstructive lung disease (emphysema) has what affect on RV/TLC ratio
- RV increases therefore RV/TLC ratio increases
- **see barrel shaped chest
restrictive lung disease (fibrosis) has what affect on RV/TLC ratio
- TLC decreases thus RV/TLC ratio increases
dead space. Comprised of what two parts?
- volume of airways and lungs not involved in gas exchange
- comprised of
- anatomic dead space
- conducting zone (nose, trachea, bronchi, bronchioles)
- physiologic dead space
- anatomic dead space
physiologic dead space. Name normal equation and abnormal equation
total volume of lungs not participating in gas exchange
- abnormal
- physiologic dead space = anatomic dead space + functional dead space in alveoli
- V/Q mismatch
- normal
- physiologic dead space = anatomic dead space
- V/Q matched
volume of physiologic dead space is calculated based on the pp of CO2 in expired air and what 3 assumptions
- all CO2 in expired air comes from alveolar exchange
- no CO2 in inspired air
- physiologic dead space does not exchange nor contributes to CO2
physiologic dead space is calculated using the following equation
VD=VT x (PaCO2-PECO2) / PaCO2
- PaCO2 = PCO2 of arterial blood
- PECO2 = PCO2 of expired air
- VT= tital volume
- Vd= physiologic dead space
alveolar air equilibriates with arterial blood. what does this mean for pressures
PaCO2 = PACO2
- PACO2= alveolar
- PaCO2 = arterial
minute ventilation equation
- total rate of air movement into/out of lungs
- minute ventilation = tidal volume x breaths/min
alveolar ventilation equation that corrects for physiologic dead space
- alveolar ventilation = (VT-VD) x breaths/min
alveolar ventilation equation that relates alveolar ventilation and alveolar PCO2
alveolar ventilation = (VCO2 x K) / PACO2
- VCO2 = rate of CO2 production
- k = constant
- **thus if CO2 production is constant, PACO2 is determined by alveolar ventilation (hyperbolic relationship)
if CO2 production is constant, PACO2 is determined by alveolar ventilation (hyperbolic relationship). What happens if CO2 production doubles from strenuous exercise?
- alveolar ventilation must also double to maintain PACO2 and PaCO2
- curve shifts to the right
Forced expiratory volume in one second (FEV1)
volume of air that can be forcible expired in the 1st second
Normal FEV1/FVC ratio
- 8
* 80% of the vital capacity can be forcibly expired in the 1st second
FEV1/FVC ratio in airway restrictive disease (e.g. fibrosis)
- Both FEV1 and FVC are decreased
- BUT FVC decreases more than FEV1
- therefore FEV1>FVC
- FEV1/FVC increases
FEV1/FVC ratio in airway obstructive disease (e.g. asthma)
- Both FEV1 and FVC decrease
- BUT FEV1 decreases more than FVC
- therefore FVC>FEV1
- FEV1/FVC decreases
