Chapter 28: Partial Airway Obstruction Flashcards
Abnormal, high-pitched sound produced by turbulent airflow through a partially obstructed airway at the level of the supraglottis, glottis, subglottis, or trachea
Stridor
Three types of stridor? Most common?
Inspiratory, expiratory, biphasic; inspiratory is most common
What type of stridor suggests a laryngeal obstruction?
Inspiratory stridor
What type of stridor implies tracheobronchial obstruction?
Expiratory stridor
What type of stridor implies suggests a subglottic or glottic anomaly?
Biphasic stridor
Stridor acts according to what principle of Physics?
Bernoulli principle
Condition defined by turbulent flow over an orificial lesion in the airway
Stridor
Relationship of diameter and length in stridorous airway:
Diameter > length
What causes turbulent flow in stridor?
Patient makes larger inspiratory/expiratory effort against a narrowed airway, which creates a pressure difference and results in stridor.
Three management techniques for partial airway obstruction:
Pharmacologic agents
Non-surgical techniques
Surgery
Which equation is the mathematical basis for laminar flow?
Hagen-Poiseuille equation
The H-P equation for laminar flow vs. turbulent flow:
Laminar flow: r^4, viscosity
Turbulent flow: r^5, density
Which H-P equation involves viscosity?
Laminar flow
Which H-P equation involves density?
Turbulent flow
What portion of the H-P equation can we manipulate when we treat partial airway obstruction? What about the surgeon?
We can manipulate air density (decreasing density = increasing flow).
Surgeons can manipulate airway radius. (Increasing radius = increasing flow)
Visible signs of partial airway obstruction?
Dyspnea, stress, breathing pattern (stridor), retractions
What are retractions and where will you see them in a patient with a partial airway obstruction?
Retractions = when the area between the ribs and in the neck sinks in when a person attempts to inhale
Seen in supraclavicular, sternal notch, intercostal, and subcostal areas of body
What can we infer from flow-volume loops?
Whether or not lesion exists
Whether lesion if fixed or variable
And if variable, whether intrathoracic or extrathoracic
What radiologic exams might we perform if we suspect a partial airway obstruction?
CT scan
MRI
What does a CT scan tell us about partial airway obstructions?
We use them to define location, cross-sectional area, and length.
Also, for diagnosis
Which method of diagnosis can be performed bedside?
Flow-volume loop, though it requires patient cooperation
On flow-volume loop, x-axis is:
time
On flow-volume loop, y-axis is:
flow
Which phase of breathing is below the x-axis on a flow-volume loop?
inspiratory
Which phase of breathing is above the x-axis on a flow-volume loop?
expiratory
Phase of breathing defined by negative pressure:
Inspiration
Phase of breathing defined by positive pressure:
Expiration
Lesions at/near the glottic level are what type of lesion? Affects what phase of breathing? Resulting flow-volume loop?
Extrathoracic variable obstruction
Inspiratory loop has attenuated inspiratory limb–inspiratory plateau–and normal expiratory phase.
In a normal airway, I:E =
50:50
In an extrathoracic variable lesion airway, I:E =
I < E
Inspiration has what affect to extrathoracic variable lesion?
Forces lesion open
Lesions within chest? Affects what phase of breathing? Resulting flow-volume loop?
Intrathoracic variable obstruction
Affects expiratory phase
Normal inspiratory limb with expiratory plateau
In an intrathoracic variable lesion airway, I:E =
I > E
In an intrathoracic variable lesion, what kind of forces pull on the parynchema?
Retractive forces
Fixed obstruction shows what kind of flow-volume loop?
Inspiratory + expiratory plateaus
Fixed obstruction has what kind of I:E ratio?
50:50
From which flow-volume loop can we not determine location of lesion? Why not?
Fixed obstruction F-V loop; Cannot determine location of lesion because it doesn’t move i terms of cross-sectional area
From which type of lesion are both limbs of a flow-volume loop attenuated?
Fixed lesion
What is your goal in a patient that presents with a PAO?
OXYGENATION
What role might steroids play in treating a PAO?
They are NOT useful acutely in treating PAO–only useful in treating respiratory distress due to asthma (inflammatory condition).
In order to qualify as support to a patient, your efforts must have what effect in regards to the PAO?
They must improve flow across an orificial lesion
Non-surgical techniques to improve flow and achieve oxygenation in a patient with a PAO:
Intubation or other airway device
Surgeries that may be performed in the event of a PAO? Which is an emergent procedure only?
Tracheostomy: could be emergent or could provide intermediate support
Cricothyrotomy: ALWAYS EMERGENT
What does salient mean?
Most notable; most important
What test should you call for in a patient of whom you suspect a PAO?
ABG
Molecular weight of O2?
32
Molecular weight of N2?
28
Molecular weight of He?
4
Which heliox mixture is the best choice for oxygenation of patient w/ PAO? Molecular weight? Density?
He:O2 = 80:20
MW: 9.6 g/mol
Density: 0.43
He:O2 = 70:30
MW?
Density?
MW: 12.4
Density: 55
If you change from air to 100% oxygen, what is your change in flow?
90%
What is density of O2?
1.43
What is density of He?
0.18
What is density of air?
1.29
Change from 100% O2 to 70:30 Heliox = what change in flow?
260%
Change from 100% O2 to 80:20 Heliox = what change in flow?
330%
