Steps in inspiration
1) contraction of inspiratory muscles
2) inflation of chest cavity
3) inflation of lung
4) inward airflow
What are inspiratory muscles?
External intercostals - muscle of ____
contraction of intercostals --> expands rib cage
when are your expiratory muscles active?
during forced expiration and exercise (abd wall muscles)
NONE ACTIVE DURING QUIET BREATHING
Patients with obstructive diseases breathe at ___
higher lung volumes
average lung size with breathing is larger in obstructive disease
resting diaphragm after expiration is ____ (more or less contracted) than average inflated lung
therefore, diaphragm is (shorter/longer)
diaphragm is shorter
what is intrapleural pressure?
what happens to PIP when you inspire?
pressure between chest wall and lung
negative PIP (vacuum) causes lung to attach to chest wall
equilibrium size of lung is (larger/smaller) than in body
2 opposing forces that cause lung to inflate
1) chest wall tends to inflate
2) lung tends to deflate
--> negative intrapleural pressuere
Typical values of PIP
@ end of expiration
@ end of inspiration
What happens in pneumothorax
bullet disrupts hydraulic connection between lung and chest wall
PIP less negative
How does Plung change with inspiration and expiration (graph)
Definition of lung compliance
which is worse, low or high compliance
graph of compliance curve
measure of how easily applied pressure induces a volume change
low compliance b/c requires more pressure for a given volume change
why does PTP incr?
Hysteresis curves for inspiration vs. expiration
difference in compliance d/t additional energy required during inspiration to recruit and inflate additional alveoli
Lung volume at any given pressure during inhalation is less than the lung volume at any given pressure during exhalation
how does emphysema vs. restrictive disease affect the lung volume vs. PTP curve
emphysema = incr compliance = destroy elastin
restrictive disease = more rigid = harder to inflate
how does emphysema affect P lung during epiration
P lung is less positive b/c lose recoil strength so no gradient for outward air flow
Causes of reduced chest wall compliance
what does curve look like?
1) old age - more fibrotic tissue in rib cage
2) obesity - extra fat impedes outward movement of chest wall
3) scar tissue
how does reduced chest wall complaince affect tidal volume?
decr tidal volume