Lecture 4: compliance, FRC, respiration volumes Flashcards
2 major collapsing fources of the lungs
surface tension
lung elastic recoil
Lung Elastic Recoil
lung has connective tissue network composed of elastic fibers; stretching them from rest position creates a retracting force that acts when stretching force is released
Pressure- Volume Curve
expand lung in volume increments and measure trans-pulmonary pressure
stretchability nonlinear
more force needed at lower and higher lung volumes
Compliance
slope of the curv; greater, easier lung compliesto disteniding; normal is .2L/cm
Stiffening of the lung casues?
Compliance (fibrosis)
Emphysema
Causes increased compliance
Net compliance
combination of lung elastic recoil and surface tension
Residual Volume
volume of air that remains when you expire as much as possible
Minimal Volume
natural collapsing force of lug down to a very small lung volume
P-V Curve
nonlinear; rest position of chest wall is very high; chest at lowest volumes is associated with negative pressure
FRC
functional residual capacity; where pressure of lung collapsing and chest wall expanding are equal due to mechanically linked systems; resting lung volume; energetically favorable
combined PV curve
total respiratory system (lung and chest wall); nonlinear
Low lung volumes
airway pressure is very negative
high lung volumes
airway pressure is positive
