lecture 14 Flashcards
Exam 3
What would Emphysema do to the delta P?
The delta P would be less than a normal lung. Alveoli have less elastic recoil so the surrounding pressure exceeds the pressure inside the alveoli. Other things that can cause this are lower lung volumes and asthma.
In addition to delta P, what else helps guard against small airway collapse?
the springy tissue of the alveoli (more of this tissue = more elastic recoil) and it provides airway traction.
What is the most important factor to getting air out of the lungs in regards to delta P?
Elastic recoil pressure is more important than pleural pressure
What could cause collapse of the upper airways?
injury to the cartilage lining the upper airways could lead to upper airway collapse
What is an example of something that could cause a fixed intra- or extra-thoracic obstruction?
Selecting too small of an ETT.
Give an example of something that could cause a variable intra-thoracic obstruction…
Causes an obstruction on forced expiration (not during inspiration) an example of this is small airway collapse caused by Emphysema, COPD or asthma.
Give an example of something that could cause a variable extra-thoracic obstruction…
Causes an obstruction on inspiration (pushes obstruction out of the way on expiration) an example of this is tracheal or upper airway injury or paralyzed vocal cords.
What does FEV1 stand for?
forced expiratory volume in 1 second
What does FVC stand for?
forced vital capacity
What is the normal FEV1/FVC for a healthy patient?
80%
What would you expect to see with FEV1/FVC for a patient with restrictive lung disease?
a fairly normal ratio, but a lower FVC.
What would you expect to see with FEV1/FVC with Emphysema or COPD?
a markedly decreased FEV1/FVC ratio dt to the extra time it takes these patients to expire all the air out of their lungs.
What do you need to do to your vent settings to help patients with COPD or Emphysema?
increase E time (expiratory time)
What does the closing volume/ capacity test tell us?
These tells us about the health of the small airways, whether they collapse or not.
Describe the closing capacity PFT…
Patient is instructed to breathe from a 100% O2 source. Any N2 coming out of the patient is measured. As patient continues to breathe N2 concentration/ PaN2 is lower in the deeper parts of the lung compared to apical lung.
Describe the 4 phases of the closing capacity test…
I: expiring dead space (no N2)
II: transitional phase (same as Fowler’s test)
III: plateau phase (beginning from the base of the lung, later portion more from the apical lung)
IV: closing volume, increased N2 as a result of collapsing airways
What is the closing capacity?
closing volume + residual volume
What is the difference in closing capacities between a 20 year old patient and a 70 year old patient?
20 y.o. = closing capacity is below FRC (very little airway collapse, as we don’t go below FRC often)
70 y.o. = closing capacity is above FRC (small airways collapse before FRC is reached)
What is clinically significant about the difference between the closing capacity between a 20 year old and a 70 year old?
d/t increased small airway collapse as we age, work of breathing increases
At what age does our closing capacity begin to exceed our FRC?
55 years of age
