Respiratory Mechanics Flashcards
(48 cards)
FRC
“Functional Residual Capacity”
-Amount of air in the lungs with the mouth is held open; elastic recoil of the lungs and thoracic wall are equal and opposite
Most common cause of pleurisy
Viral infection
2 Forces of Lung Elastic Recoil
- Collagen and elastin fibers
2. Surface tension from the water lining the alveoli
Laplace’s Law (Surface Tension)
P=T/ r/2
*Pressure is inversely proportional to radius
Shunt
Vascular pathway in the lung which has no gas exchange
Dipalmitoyl phosphatidyl choline
“SURFACTANT”
-Surfactant inserts itself b/w water molecules lining the alveoli to decrease the cohesive forces b/w them
Net Result= Decreased surface tension
Tripod Position
Assumed by COPD pts. in an effort to force expiration of air
Pressures in Inspiration
Start: Transmural Pressure = -5 cm H2O; lung elastic recoil = 5 cm H2O
=>No air-flow
Begin inhalation: Pleural volume increases; decrease in Ppl
=> Lungs begin to expand
During Inhalation: Increased lung volume increases the volume of alveoli; Patm> Pa
=>Air flows in
End Inhalation: Elastic recoil is stretched to limits and it balances forces around the lung
=>Airflow stops
Flail Chest
Damage thorax causes chest cavity to move inward during inspiration
-Ppl is not sufficiently negative causing no air to flow in
Tension Pneumothorax
Air accumulates in pleural cavity after collapse of lung
*Mediastinum will shift to opposite side of lung
Transmural Pressure
Ptm= Palv- Ppl
Compliance in emphysema and fibrosis
Emphysema= INCREASED
Fibrosis= DECREASED
Specific Compliance
A measure of compliance as a function of size
C= P/V
Specific Compliance= C/volume of lungs
Total pulmonary compliance
1/total compliance= 1/lung compliance + 1/ chest wall compliance
Alveolar Simplification
Breakdown of structural proteins due to increased levels of trypsin in the lungs
=>Decreased # of alveoli
Centrilobar emphysema
Most common subtype of emphysema that affects the central region around the secondary pulmonary lobules; (Upper lobe)
- Spreads peripherally
- Assoc. w/ long-term smoking; inhalation of chemicals
Panacinar Emphysema
Uniform destruction of alveoli predominantly in the lower lungs
-Assoc. w/ AAT deficiencies of Ritalin abuse
Predict compliance in the following situations:
Decreased pulmonary surfactant
Removal of lobe
Obesity
Pulmonary Vascular Congestion
Decreased in all
Areas of greatest airway resistance
Large airways
Passive Exhalation
Elastic recoil forces in alveoli move air out of the airway; airway is held open by expansile forces since Ppl is negative
Forced Exhalation
When the rib cage pushes in and abdominal muscles push upwards, Ppl increases
Alveolar pressure becomes more positive pushing air out faster
Dynamic Compression
Increased Ppl during forced exhalation can cause collapse of the alveolar airways => Decreased air release
*Common in emphysema; decreased elastic recoil means air must be forced out of alveoli
Greatest flow rate in lungs
Large Airways
*Must have cartilaginous rings because fast air flow=decreased pressure; airway could collapse
Tethering
The attachment of alveoli to neighboring alveoli
=>Decreases the tendency for vessels to collapse
*Decreased in emphysema
