Lecture 3: Respiratory Mechanics Flashcards
Compliance of the lung _________ with _________ lung volume; relate to compliance and elastance
Decreases with increasing (more –> less compliance, less –> more elastance)
If the pleural plessure _______ 0, what happens to the lungs? To the chest wall?
Lungs collapse, chest wall springs outward
At the functional resting capacity, the pressure of the lungs equals what?
The negative pressure of the chest wall
What size of alveoli is unstable? What’s the equation?
Small; P = 2T / r
Describe surfactant
Phospholipids that migrate to surface of alveoli w/ hydrophobic ends sticking out, decreasing surface tension
What is hysteresis?
Change in mechanical properties due to the volume history of the lung (lung volume depends not only pressure but also whether your inspiring or expiring)
Higher pressures are required to open/close airways
Open
Lungs filled with water are more/less compliant? What does this mean?
More (surfactant is more important for compliance than lung’s intrinsic properties)
Laminar flow is proportional to…Turbulent flow is proportional to…
Pressure difference; the square root of pressure difference
Reynold’s number
Determines laminar (smaller numbers) or turbulent (larger numbers) flow; = pdV / viscosity of gas
While each airway by itself gets smaller through the respiratory track…
Entire cross-sectional area of peripheral airways is much greater than that of central areas
In large airways, what kind of flow do we get?
Turbulent
In peripheral airways, what kind of flow do we get?
Peripheral
Where do we get the most resistance in the airways?
Early (bronci)
Resistance is proportional to gas _______ in turbulent flow. Give a clinical indication of this.
Density; heliox (helium/oxygen mixture less dense than air) can be given to patients with upper airway narrowing to decrease airway resistance
