This document discusses respiratory monitoring techniques including rib cage and abdominal belts, thermistors, nasal cannulas, and esophageal pressure. It explains how these methods can detect changes in breathing from normal to obstructed. Rib cage and abdominal paradox and changes in inspiratory flow shape indicate obstruction. Esophageal pressure monitors the effort required to breathe and also detects obstruction. CPAP and bilevel pressure therapies use positive pressure to splint open the upper airway and alleviate obstruction during sleep.

1. Requirement for this lecture:
•one balloon that is easy to inflate and
•one that is difficult to inflate

2. Respiratory Waveforms
 Nasal Flow via nasal cannula
 Oral/nasal flow via thermistor
 Effort via esophageal pressure (not often used)
 Rib cage and abdominal movement via RIP
(respiratory inductive plethysmograph)

3. Rib cage and abdominal belts (RIP)
 During quiet, unobstructed breathing the belts move
in and out together. This reflects the RC(rib cage) and
Ab(abdomen) expanding and relaxing together.
 With partial obstruction the belts can begin to move
out of phase with each other.

4. Rib cage and abdominal belts (RIP)
 With significant or full obstruction the belts will move
in paradox; that is one moves out when the other
moves in. This is because the airway is now a closed
system-the volume doesn’t change. So, if you expand
your chest (increasing chest volume) you have to
decrease your abdominal volume and vice versa.
 Now fill your balloon with air (or water if you like) and
tie it off. What happens to the top of the balloon if you
squeeze the bottom? What happens to the bottom if
you squeeze the top? That is PARADOX!

5. Thermistor
 This measures temperature change as air moves in an
out.
 It can tell you the presence of air flow but cannot give
you information about the quality of that flow such as
flow limitation.

6. Nasal cannula
 Actually measures the pressure changes as air moves
past the cannula.
 In a closed system like a nasal mask (with no leak)
pressure equals flow.
 In a small area (like the inside of the nose) pressure is
very similar to flow.
 This would not work for oral flow because it is not a
closed area.
 The signal you see is showing the rate of change of the
inspiratory and expiratory pressure

7. Unobstructed Airflow measured by
mask or nasal canula
Inspiratory flow
Expiratory flow
Zero flow
Notice that the unobstructed inspiratory flow (pressure) signal is rounded.
As the signal moves up it is showing the flow rate increasing and as the
signal moves back to zero the rate of flow is decreasing.
The expiratory signal is pointed and gradually returns to zero. Inspiratory
flow should always be up.

8. Partially obstructed inspiratory
flow (UAR)
Notice the concave shape of the inspiratory
flow signal
This occurs because during inspiration the
airway narrows and the rate of inspiratory
flow decreases despite increasing effort.

9. Compare the obstructed and
unobstructed breaths

10. Esophageal Pressure (Pes)
 A balloon on a catheter is placed through the nose into
the esophagus.
 This pressure reflects the pressure being generated in
the larynx.
 When you breathe in the negative pressure changes
the pressure in the balloon and it returns to normal
during relaxed exhalation.
 The harder it is to breathe (increased resistance,
snoring, upper airway obstruction) the more negative
pressure you have to develop to draw in air.

11. Esophageal pressure (Pes)
Notice that Pes is negative during inspiratory flow. This indicates the negative
(suction) pressure generated by the expansion of the lungs that causes inspiratory
flow. Pressure returns to zero during relaxed expiration.
The next slide shows you how pressure and flow change from wake to sleep to
increased resistance/snoring.

12. Rounded
Notice the rounded inspiratory
Wake inspiratory
flow flow, little effort (Pes-esophageal
Little pressure indicates how hard you
effort work to pull in air), and RC and AB
are in phase
RC and
AB in
phase
Sleep- The airway is still open although
open breathing frequency is higher
than awake – rounded flow, little
airway effort, and RC and AB are still in
phase
Notice now the inspiratory flow
Insp. Flow is collapsed
Sleep- Indicating flow limitation signal is not rounded but is
Flow collapsed a little, Pes is bigger
Greater pressure
indicating much more pressure
limitation Development means more
work has to be developed to breath and
RC and AB out of RC and AB are paradoxing
phase

13. Respiratory belts, airflow and respiratory effort (Pes) when
partial obstruction resolves
This picture shows an
individual moving from
partial obstruction to a
fully open airway.
Notice that when airflow
(measured by nasal pressure in the
first few breaths of channel “e”)
shows flow limitation –
the RC (a) and AB (b) are
in paradox. The pressure
developed (f) is large.
In the last breath, with no
flow limitation, the belts
are in phase and little
pressure is developed

14. Why does this happen?
Remember:
 The upper airway is composed partially of muscle.
 Upper airway muscles relax in sleep
 This allows the airway to narrow in everyone and in
some to partially or fully collapse.
 The next slide shows the airway changing from wake to
sleep to snoring to hypopnea to apnea. Below that are
the effects on flow and pressure.

15. Sleep on the upper airway and its consequences

16. CPAP on the Upper airway
 CPAP’s positive airway pressure essentially takes the
place of the relaxed muscles to hold open the airway.
Get your easy to inflate balloon and blow just enough
air in to stretch it a little. Now try it again with the
stiffer balloon. Can you tell that it takes more pressure
for you to inflate the second balloon?
 Peoples airways are like balloons with different degrees
of stiffness. This is why they need different levels of
PAP.

17. Bilevel Pressure on the Upper Airway
 Bilevel pressure is a combination of CPAP (which is
the expiratory pressure) and mechanical ventilation
which helps to inflate the lungs.
 Now blow enough air in one balloon just to hold it
open (point A.) That is the CPAP.
 Now, holding that pressure inflate your balloon a little
(point B) then let the pressure back to point A.
 This simulates what bilevel pressure does. It hold the
airway pressure at a certain level to keep it open then
adds more air pressure during inspiration to increase
the size of the breath.