How do we change the radius of the tube? What does decrease/increasing the radius do to resistance? What is radius changes used for?
- Smooth muscle in the airway walls
- a. increase resistance
b. decrease resistance - Directing air to the alveoli with lots of blood (?)
Perfusion
- Q
- from right ventricle (5L/min)
Alveolar Ventilation
- volume of air reaching the alveoli
- 4L/min
J=_________________
=((S.A) X D X (P1-P2)) / distance
J: diffusion rate in ml/min
D: diffusion coefficient for each gas
(P1-P2): pressure gradient across alveolar membrane
S.A.: surface area available for diffusion (corresponds to # of alveoli in lungs)
Distance: thickness of alveolar barrier
***must be calculated for each gas independently
What is J for O2? CO2?
- 250 ml/min (air to blood)
2. 200 ml/min (blood to air)
What is the role of collagen in the interstitial space?
it increases the diffusion distance and decrease the diffusion of the gases across the barrier (can increase with pathology; such as interstitial lung disease)
What two things can change within the lungs?
surface area and distance
Which weighs more/which is more soluble in water: O2 or CO2?
- CO2
2. O2
What is the safety margin for RBCs?
They spend .75 seconds in the pulmonary capillary, but typically pick up the O2 by .25 seconds. This gives them an extra .5 seconds to pick up the O2 if anything happened to go wrong.
What is the safety margin for RBCs during heavy exercise?
- they don’t have one!!
- they only get the .25 seconds in the capillary
- also true in patients with lung disease
What is the simples correction factor ever?
DLO2= 1.23 X DLCO
Which has a larger safety margin: CO2 or O2?
CO2 by a LOT
Acute neonatal respiratory distress syndrome
- caused by immaturity of the lungs and deficient surfactant production
- treatment with exogenous surfactant improves condition
LaPlace’s Law
Pressure=2T/r
T= tension
r= radius
Large/small alveoli have a _1/2__ radius, so the pressure is __3/4__.
Large/small alveoli have a large/small radius, so the pressure is low/high.
**Problem: the air wants to go towards the lower P, and this can collapse the small alveoli
What is the role of surfactant?
It reduced T in the smallest alveoli more than in the larger alveoli, which helps to lower their pressure. It removes the gradient, so the air stays in the small alveoli. It is stored in intracellular lamellar bodies, and secreted into alveolus. (basically, it reduces water’s attraction to itself)
What is surfactant composed of?
- Phospholipids
- Dipalmitoylphosphatidylcholine
- Multiple proteins (SPA, SPB!!!, SPC, SPD)
O2 vs. CO2
- Partial pressure in lungs
- Partial Pressure in venous blood
- Gradient for diffusion at the start of the capillary
- 104 vs. 40 mmHg
- 40 vs. 45 mmHg
- 60 vs. 5 mmHg
SP-A
- regulates DPPC secretion and function
- SP-D has similar function/may modify SP-A
SP-B
- important in adjusting surface tension
- SP-C has similar function; both are lipophilic
What 2 things promote surfactant production? What inhibits it?
- Prostaglandins promote secretion
- ## ATP and stretch
- SP-A and DPPC inhibit secretion (negative feedback)
COPD results in the destruction of ___
alveoli (destroys SA for GE)
Interstitial fibrosis
deposition of collagen into the interstitial space
Sympathetic innervation causes…
broncho-dilation
