Waters II Flashcards
What is the major muscle of inspiration?
the diaphragm
How much does the diaphragm move during tidal inspiration?
1cm down
How much does the diaphragm move during forced inspiration?
up to 10cm
What nerve innervates the diaphragm?
the phrenic nerve
What accessory muscles help in inspiration?
- External intercostals (I for E and E for I),
- Scalenes, and
- SCM
How does expiration occur normally?
passive (no muscles)
How does forced expiration occur (what muscles?)?
abdominal muscles (rectus abdominus, internal and external obliques, transverse abdominus) and internal intercostals work
What happens to intra-pleural pressure during inspiration?
it becomes more negative and transpulmonary pressure increases
What is transpulmonary pressure?
Palveolar-Pintrapleural
What does an increase in transpulmonary pressure cause?
increased lung expansion
How does lung expansion affect Palveolar?
it becomes sub-atmospheric
What happens when Palveolar becomes sub-atmospheric?
air flows into alveoli
T or F. Pintrapleural becomes less negative during inspiration
F. It becomes more negative
When is Palveolar most negative?
Mid-inspiration
When is Palveolar most positive?
Mid expiration
What happens with Palv- Patm is negative?
inspiration
Why is Pintrapleural negative?
There is a natural tendency for the chest wall to pull out and for the lung tissue to collapse
The degress to which transpulmonary pressure (Palv- Pip) leads to lung expansion depends on ____ of the lung.
compliance (compliance= 1/elasticity)
T or F. Compliance changes during parts of inspiration (and expiration)
T. It is not constant or linear, nor is compliance the same during inspiration as it is during expiration
Why do compliance patterns differ from inspiration to expiration?
hysteresis (surfactant properties control this)
What pathologies can decrease compliance of the lungs (this is considered ‘restrictive’)?
- fibrosis
- pulmonary edema
these patients have trouble getting air IN to the lungs and EXPANDING them
What pathologies can increase compliance of the lungs (‘this is considered obstructive’)?
- emphysema
- some in normal aging
these patients have trouble getting air OUT of the lungs
When compliance increases, ____ becomes more likely
lung collapse
T or F. Restrictive lung patients have decreases capacities and volumes (FVC, TLC, RV, FRC)
T.
T or F. Obstructive lung patients have decreases capacities and volumes (FVC, TLC, RV, FRC)
F. Increases FRC, TLC, FEV1 and RV, but normal or reduced FVC
What does the term COPD encompass?
emphysema or chronic bronchitis
80-90% of COPD cases are caused by what?
smoking
What happens in emphysema?
destruction of alveolar walls due to loss of elastic material (increased compliance) and enlargement of alveolar air spaces which decreases surface area for gas exchange
What happens when elastic material is lost from lung tissue?
the lungs struggle to stay open during forced expiration
What causes chronic bronchitis?
inflammation where the airways become obstructed due to excessive mucus production
What changes are seen in Pip at the end of inspiration in emphysema patients?
less negative Pip than normal due to loss of elastic fibers
Lung compliance is determined by what main factors?
- tissue properties
- surface forces
What is interdependence?
The fact that adjacent alveoli share a wall prevents them from collapsing
Tissue properties (collagen, elastin, etc.) account for approx. ___ of the compliance of the lung
1/3
What is the role of pulmonary surfactant?
It acts as a detergent to reduce water molecule surface tension that tends to act to promote collapse of alveoli.
NOTE: Surface tension must also be overcome to expand the lungs
What produces surfactant?
Type II pneumocytes
What stimulates surfactant production?
large expansion of the lungs
What happens in respiratory distress syndrome (RDS) of newborns?
reduced surfactant production (which occurs late in gestation) makes lung inflation difficult
T or F. Compliance is increased in RDS
F.
What is another potential consequence of RDS
Alveoli tend to collapse upon expiration (aka atelectasis)
How is RDS treated?
mechanical ventilation and surfactant replacement therapy
What is the transmural pressure needed to keep an alveoli open?
2*Tension/radius of sphere
Laplace’s law
Atelectasis is a common complication of anesthesia, why?
it reduced surfactant function
Resistance to air flow decreases drastically in the respiratory airways compared to conducting airways even though radius decreases substantially. Why?
Because the cumulative radius is higher
What is lateral traction?
elastic connective tissue fibers attach to airways exterior and pull outward, tending to open airways
What happens in asthma?
bronchioles constrict via inflammation
Where is Pip most negative in the lung?
at the apical parts
Where is resistance to flow highest in the lungs?
medium-sized bronchi, even as radii decrease moving toward alveoli, the flow becomes more laminar
