Mechanics of Breathing II Flashcards
during inspiration pressure?
intrapleural pressure drops
during expiration pressure?
intrapleural pressure increases
transmural pressure?
Ptm = alveolar pressure - intrapleural pressure
driving pressure?
pressure change from one end of tube to the other
deltaP = V x R
laminar flow
P ~ V
turbulent flow
P ~ V-squared
reynolds number
Re = 2rvd / n
end pressure in laminar vs. turbulent?
greater drop in pressure turbulent vs laminar flow
end pressure turbulent < laminar
higher velocity of flow?
less pressure
resistance = ?
R = (P1-P2) / flow
constant irrespective of flow
1/ r to the 4th
turbulent flow
resistance increases with flow rate
resistance in lung?
increases in 5-7 generations then drops off
- increase in airways in parallel - cross sectional area increases
- have lower resistance
velocity of gas in lung?
highest in trachea (turbulent)
decreases as you go along airway
laminar flow in smaller airways (moving slower)
two types of resistance in lung?
airway and tissue
tissue resistance
overcome for lung to inflate
-85% of total resistance
factors determining cross sectional area of airways
lung volume
lung elasticity
bronchial smooth muscle tone
airway resistance and lung volume?
resistance decreases as lung volume increases
patient with obstructive lung disease?
breathe at higher lung volumes to decrease airway resistance
ex/ barrel chested in emphysema
bronchoconstrictors
medium sized airways (bronchioles)
PNS (ACh and methacholine)
histamine
irritants (cigarettes)
bronchodilators
SNS (NE on beta-2 receptors)
beta-2 agonists (isoproterenol and albuterol)
increased P-CO2 in bronchioles
parasympathetic on lungs?
bronchoconstriction
sympathetic on lungs?
bronchodilation
quiet respiration?
transmural pressure remains positive
forced expiration?
engage expiratory muscles raises intrapleural pressure which is often positive
intrapleural pressure exceeds airway pressure?
transmural is negative
-airways will collapse unless supported by smooth muscle or cartilage
extra effort?
leads to compression of alveolus
no increase in flow
dynamic airway compression
during forced expiration
- loss of pressure occurs as gas moves from alveolus to mouth
- increasing resistance and velocity
- transition from laminar to turbulent flow
forced expiration
dramatic increase in intrapleural pressure
transmural pressure becomes negative (airways close)
airway compression driving force?
difference between alveolar pressure and pleural pressure
elastic recoil pressure?
difference between alveolar and pleural pressure
flow volume loop and emphysema
not much change with inspiration curve
- during expiration, decreased flow-volume loop
- due to airway closure (air trapping)
bronchodilator - expiratory curve will increase
obstructive FEV/FVC relationship?
decreased ratio
restrictive FEV/FVC releationship?
increased ratio
FEV/FVC?
FEV - forced expiratory volume (in 1 second)
FVC - forced vital capacity
work of breathing for restrictive?
increased elastic resistance
-around 20 breath is comfortable (rapid)
work of breathing for obstructive?
increased airflow resistance
-around 10 breaths is comfortable (slower)
airway resistance
decreases with increased volume
airways in parallel?
decreases resistance
obstructive lung disease?
airflow limitations at early point when compared to normal subjects
