Hi everyone, we will explain the dynamic collapse of the airways and how it is
manifested on the ventilators scalars and loops but let's first explain what is a
dynamic airway collapse. Normally there is a dynamic airway collapse characterized
by bulging of the posterior membrane inside the airway lumen. The cartilages
are intact and airway narrowing during expiration is usually less than 50% as
compared with inspiration. Now excessive dynamic airway collapse is
caused by excessive bulging of the posterior membrane this leads to greater
than 50% reduction in airway lumen during expiration compared to
inspiration. In severe dynamic airway collapse or in Crescent type tracheomalacia
airway collapse is caused by weakness of the anterior wall which
leads to airway narrowing during expiration. Now on volume flow loop you
can see the sudden drop in expiratory flow followed by the plateau phase. These
findings characterized the airway collapse better
Now on the CT scan you'll be able to appreciate complete collapse of the
lower trachea during expiration
compared to inspiration this area here. You can also see that on the dynamic
bronchoscopy that reveals similar findings and confirms that the
collapse is caused by flattening of the anterior tracheal wall which
characterizes the Crescent type tracheomalacia. So on the scholars what you see
is on the floor of our time curve you can see the sudden decrease in the flow
and then the plateau phase of the floor you may be able to appreciate some
persistent flow at the end of expiration which lead to auto-peep and on the floor
volume which is reversed from the spirometry, you can see the big sudden
decrease in the flow and the plateau phase. Similarly in this patient you can
appreciate the sudden decrease in the flow in early expiration as a result of
the dynamic collapse of the trachea followed by the plateau phase where the
flow continues gradually however there is not enough time for complete
exhalation so the patient develops auto-peep or dynamic hyperinflation on
top of the dynamic collapse of the airway and he can appreciate the trapped
volume on the volume over time curve or this area represent the amount of air
that was trapped into the lung. I hope I was able to explain the dynamic collapse
of the Airways and how it is manifested on the ventilator scholars and on the
floor volume loop thank you