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
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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
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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
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lung compliance and airway resistance not only affect the magnitude of air flow in the lung (ventilation) but also ____
how we breathe