PULMONARY 03: LUNG MECHANICS 2 Flashcards
What are the four primary non overlapping lung volumes?
RV, V(total), IRV, ERV Residual volume Tidal volume Inspiratory reserve volume Expiratory reserve volume
What is a lung capacity? How does it differ from a lung volume?
A lung capacity is comprised of 2+ lung volumes
meaning a lung volume is a basic unit of lung potential, and a capacity is a summation of two+ of those
How do you measure residual volume?
Helium or plethysmography (you cannot use a spirometer)
What is compliance?
A measure of the elastic properties of something (in this case, the lung)
Surfactant does what to compliance?
Surfactant increases lung compliance
What is going on at point 1 of the lung PV loop
Volume is low (we are at the residual volume)
From here, as we inspire and approach point two, pressure around the lung decreases
What is going on at point 2 of the lung PV loop?
Pressure has dropped during inspiration. As pleural pressure decreases (becomes more negative), volume slowly increases, but this is low compliance. This is until a critical opening pressure is achieved (at point 2). At this point, we have achieved the pressure required to open and recruit closed pathways and alveoli.
What is going on at point 3 of the lung PV loop?
Volume is going to rapidly flood into the lungs at this point (high compliance point, system is able to distend and collapse with smaller changes in pressure)
What is going on to get to point 4 on the lung PV loop?
There is a decrease in compliance as TLC is reached; then, as we expire, “pleural pressure” increases because we are no longer contracting external intercostals and diaphragm. The lung volume returns toward residual volume
What is point 5 on the lung PV loop referring to?
Point 5 is referring to hysteresis
What is hysteresis?
Non-recoverable work required to inflate the lungs
What is hysteresis proportional to?
DeltaP between inflation and deflation
What is the impact of surfactant on the PV loop?
Surfactant deceases pressure necessary to open. If you do not have surfactant (blue loop) it takes WAY more pressure to open airways and you lose way more energy (hysteresis)
What is elastic recoil of the lungs attributable to?
Its elastic properties and surfactant
What does fibrosis lead to?
A loss of compliance (tissue is tougher)
this would cause high elastance
What does emphysema lead to?
A gain of compliance (lungs become more stretchy, too stretchy)
Air flow is (turbulant/laminar) in the large airways, and (turbulant/laminar) in the small airways of conducting zone?
Turbulent; laminar (and transitional)
AWR (airway resistance) is most dependent on:
A.) Length of airway
B.) Radius of airway
C.) Viscosity of air
D.) Airway resistance is whatever you want it to be
Radius of the airway
Remember, this is the same resistance formula we talked about with jonathan
R= L8viscosity/(r^4 * pi)
Do we count the resistance of airways in the lungs as a series, or in parallel? What does this mean for the total resistance?
Parallel
therefore, the total resistance is less than the individual components
Because modulating the radius of an airway changes the resistance, we know that it therefore also alters
A.) Flow
B.) viscosity
Flow
What is the effect on airway resistance as you increase lung volume?
As you increase lung volume, airway resistance decreases
What happens if you decrease cross-sectional area of an airway?
The resistance of the airway increases
Airway resistance is dependent on what three things
Lung volume
smooth muscle
mucus/edema
What does it mean if you have a restrictive lung disease?
The lungs cannot inflate
They display a reduced cmpliance and volumes (FrC/TLC/etc are reduced)
What does it mean if you have an obstructive lung disease
There is increased resistance in the airways
This means you have a reduced flow
Parameters like FEV1 will be reduced
The equal pressure point, with regard to lungs, is what?
The point at which pressure inside and surrounding airways is the same
During forced expiration, what limits airflow?
Dynamic compression of airways
Work of breathing at tidal volume is high, or low?
Low
Patients will try to adjust breathing to minimize the work of breathing
How do we treat obstructive diseases like asthma?
B2 agonists like inhalers can help dilate airways
