Ventilation Flashcards
Minute Ventilation (VE) define
volume of air flow through the lung per minute
Equation for Minute ventilation
mInute ventilation (VE) = tidal volume x Breathing rate
typical values (average sized person) for TV BR Minute ventilation (VE)
TV = 0.5 L/breath BR = 12 breaths/minute
Minute ventilation (VE) = 6L
define tidal volume
frequency of breathing and volume of air per breath
define ventilation
airflow in the lung
a
a
define alveolar ventilation (VAdot)
volume of air flow in alveolar space per minute
typical value for alveolar ventilation
4.2 L
where does gas exchange occur in the lungs
alveoli
Airways hold ___% of lung volume Alveoli hold ___% of lung volume
30%
70% so VE * 0.7 = VAdot
a
a
Factors that influence lung ventilation (VAdot)
1) Obstructive diseases (COPD)
2) Compliance problems (pulm fibrosis)- severe ONLY
3) exercise (incr up to 10x)
4) high altitude (low O2 level)
5) gravity
why does only severe compliance disease affect lung ventilation
because body has compensatory mechanisms to compensate for mild/moderate form of disease
why does ventilation incr with exercise
to get more O2 delivery to periphery
how does gravity affect ventilation
alveolus at top of lung has more gravitational forces (more weight below it) than alveolus at bottom –> gravity affects top alveolus more than bottom
which alveolus, top or bottom, is more affected by gravity
top –> has weight of lung below it
Vol (top alveolus) > Vol (bottom alveolus)
Vent (top alveolus) < Vent (bottom alveolus)
why does top alveolus have less ventilation than bottom alveolus
airflow = change in volume during ventilation cycle
smaller volume = greater possible change in volume = greater air flow and greater ventilation therefore, top alveolus LESS COMPLIANT than bottom because more gravity to incr baseline volume
ventilation (airflow) depends on ___ NOT ___
DEPENDS ON CHANGE IN VOLUME DURING VENTILATION CYCLE NOT ABSOLUTE ALVEOLAR VOLUME/SIZE
On compliance CURVE with alveolar volume vs. transpulmonary pressure where do top and bottom alveolus lie
top alveolus is further up on saturated portion so slope (compliance) is smaller bottom alveolus in mid curve
A
A
A
A
lung compliance and airway resistance not only affect the magnitude of air flow in the lung (ventilation) but also ____
how we breathe
lung compliance and airway resistance not only affect the ___ but also how we breathe
magnitude of air flow in the lung (ventilation)
what is the work done in the lungs? (2 types)
1) work done against elastic recoil of lungs 2) work done against airway resistance
if you increase elastic recoil (decr compliance), work ___ if you increase airway resistance, work ____
increases increases can be each individually or combo
for small tidal volumes, work to overcome elastic recoil is (small/large) work to overcome airway resistance is (small/large)
elastic recoil = small work airway resistance = large work –> when you breath at high frequency (small TV), you won’t inflate lungs to large lung volumes during inspiration (small TV) - –> incr freq –> opens up airways
for large tidal volumes, work to overcome elastic recoil is (small/large) work to overcome airway resistance is (small/large)
elastic recoil = large work inflating lung far past intrinsic equilibrium position, and that takes lots of work –> decr freq –> MORE WORK airway resistance = small work
most people breathe at ___ tidal volumes why?
middle tidal volume (least amount of work)
based on work vs TV/freq curve, at low Freq, high tidal volume work is ____ (large/small)
large
based on work vs TV/freq curve, at low Freq, high tidal volume work is ____ (large/small)
alarge
based on work vs TV/freq curve, we breathe in what shape
we breathe at middle TV and frequency v-shaped
how does obstructive disease affect work vs. resistance and elastic curves?
in bronchitis/asthma, the elastic curve stays same
resistance curve shifts upwards due to incr resistance to outflow
lowest point (two curves intersect) is occurring at lower freq, high TV than healthy
what is anatomical dead space what % of total lung volume why is it called dead space
difference between minute ventilation and alveolar ventilation = air flow through AIRWAYS per minute BEFORE REACH ALVEOLAR 30% NO GAS EXCHANGE
how does a snorkel affect the anatomical dead space
LARGER ANATOMICAL DEAD SPACE
enlarges you have to breathe deeper and slower frequency because to get air down to alveoli must move air through tubing so total air intake has to be larger
define alveolar dead space
why called dead space
alveolus functioning perfectly well but sitting against an occluded pulmonary capillary NO GAS EXCHANGE (defective pulm capill)
what is significant about alveolar dead space in terms of efficiency of breathing and how that affects work in breathing such as in snorkeling
dead space decr efficiency of breathing
MORE WASTED VENTILATION (not contribute to gas exchange)
therefore, incr work in breath
(you have to breath deeper, slower freq to get air to alveoli thru tubing so total air intake has to be larger)
define physiologic dead space
physiologic dead space = anatomical dead space + alveolar dead space
what is anatomical dead space why is it called dead space
difference between minute ventilation and alveolar ventilation = air flow through airways per minute NO GAS EXCHANGE
how does a snorkel affect the anatomical dead space
enlarges
define alveolar dead space
why called dead space
alveolus functioning perfectly well but sitting against an occluded pulmonary capillary NO GAS EXCHANGE (defective pulm capill)
UNPERFUSED REGIONS OF LUNG
what is significant about alveolar dead space in terms of efficiency of breathing
dead space decr efficiency of breathing MORE WASTED VENTILATION
define physiologic dead space
physiologic dead space = anatomical dead space + alveolar dead space
can increases in dead space result in reduced alveolar ventilation?
TYPICALLY NOT changing alveolar ventilation manifests as V/Q mismatches unless snorkel too long, can’t fill both long tubing and airway and alveoli
can increases in dead space result in reduced alveolar ventilation?
TYPICALLY NOT changing alveolar ventilation manifests as V/Q mismatches unless snorkel too long, can’t fill both long tubing and airway and alveoli
Define (active breathing) Total lung capacity Vital Capacity Residual Volume
TLC = volume of lung with maximal inspiration VITAL CAPACITY = difference between TLC and Residual Volume Residual volume = minimal volume lung maintains with maximal EXPIRATION (~2L)
Define (quiet breathing) Tidal Volume Functional Residual Capacity
Tidal Volume = Difference between max and minimal volume of lung with quiet breathing FRC (~3 L) = volume of lung after quiet expiration = minimal volume of lung with quiet breathing
a
a
How to measure dynamics of airflow Procedure
1) Patient quietly breathing 2) Patient takes in max inspiration incr lung capacity 3) Patient then breathes out with max expiration 4) Measure rate of air flow 5) Lung returns to residual volume
Equation for rate of airflow
rate of air flow during expiration = FEV 1.0 / FVC
Define FEV 1.0 FVC
FEV 1.0 = volume of air flow in 1st second FVC = total amount of air moving after max expiration
how does pulmonary fibrosis affect compliance
Can’t inflate lung fully, decr VC
Do not affect airway resistance (may even incr FEV1.0/FVC
Forces on lung to deflate towards intrinsic equilibrium position are greater with pulm fibrosis
Effect of bronchitis on RV, FRC, TLC, VC
incr FRC and incr RV due to air trapping
decr FEV1.0/FVC due to extra air trapped in lung with expiration
decr VC because airway resistance
What are situations where we increase proportion of anatomic dead space
1) breathe rapidly, small tidal volume (so tidal volume doesn’t reach alveoli) = compliance problem
2) snorkeling (incr total conducting path for air)
Effect of decr compliance disease on elastic and resistance work
What is different about emphysema from other obstructive lung diseases?
unchanged or small incr (rather than decr) in vital capacity due to incr lung compliance so reach higher lung volumes
