Lung physiology

Question 1

Five important lung products

Answer 1

1. Surfactant from type 2 pneumocytes
2. prostaglandins
3. Histamine
4. Angiotensin converting enzyme (blockage of which increases bradykinin)
5. Kallikrein - activates bradykinin

Question 2

8 Lung Volumes

Answer 2

1. Residual Volume, RV, the part you cant blow off
2. Expiratory reserve, ERV, can blow off but don’t usually
3. Tidal volume, TV, normal resting breaths,
4. Inspiratory reserve, IRV, extra space for a deep breath
5. Vital Capacity, VC, 2+3+4
6. Functional Residual capacity, FRC, 1+2
7. Inspiratory capacity, IC, 3+4
8. Total Lung Capacity, TLC, 1+2+3+4

Question 3

Physiological dead space

Answer 3

V_d=V_T (PaCO2 - PeCO2)/PaCO2

Portions of the lung that do not exchange gas

mostly the apex

Question 4

What causes a O2 hemoglobin curve to shift right?

Answer 4

This signifies decrease O2 affinity,

Caused by C-BEAT

1. CO2
2. BPG
3. Exercise
4. Acid/Altitude
5. Temperature

Question 5

What does CO poisoning due to circulating hemoglobin

Answer 5

It binds cooperatively to Hb, which has a odd effect

The O2-Hb binding curve will shift left (higher affinity)

but

The overall capacity will decrease (fewer binding site)

Question 6

Define Perfusion limited gasses

Answer 6

Gasses that rapidly diffuse across the lung tissue, meaning that the length of the capillary exposed to aveoli (and the partial pressure of gas outside) determine the exchange of the gas.

O2 (in normal health

CO2

N2O

These gasses diffuse freely, so if blood volume goes up, diffusion goes up.

Question 7

define diffusion limited gasses

Answer 7

Gasses that are limited by the rate at which they diffuse across the membrane. This means that even with long exposeure to the aveoli, they cant exchange well, because they dont cross the membranes well

O2 (when emphysema, fibrosis are present)

CO

These gasses dont equilibrate by the time the blood carrying them leaves the lung.

Question 8

Factors that directly effect diffusion

Answer 8

V = A/T xD(P1-P2)

A = area

T = thickness

D(P1-P2) = difference in pressure

Thus, Area and delta Pressure are directly proportional to diffusion.

while

Membrane thickness is inversly proportional

Question 9

Define and describe causes of pulmonary hypertension

Answer 9

mmHg > 25

results in atherosclerosis, medial hypertrophy and intimal fibrosis of the pulmonary arteries

Primary - inactivation of BMPR2 - proliferation of lung smooth muscle

Secondary - COPD, mitral stenosis, reccurent PE, autoimmune, Fibrosis, Left to right shung, sleep apnea or high altitue (due to hypoxic vasoconstriction)

Question 10

Pulmonary vascular resistance

Answer 10

PVR = Delta P (artery - left atria)/Cardiac Output

here CO = R = 8nL/πr⁴

Where n is viscosity

L is length

and pi R 4 is the radius.

Question 11

What is the alveolar gas equation

Answer 11

PAO2 = PIO2 - PaCO2/R

or

aveolar O2 = pressure of O2 inspired - Pressure of CO2 in arteries/(CO2 produced/O2 consumed)

Is usually about

PAO@ = 150 - PACO2/0.8

Question 12

What is the usual A-a gradient

Answer 12

10 - 15 mmHg

Question 13

Types of Oxygen deprivation

Answer 13

Hypoxemia (low artery O2)

Hypoxia (low O2 delivered to tissures)

Ischemia (lack of blood flow

Question 14

Causes of Hypoxemia

Answer 14

**Normal A-a Gradient causes **

High altitude (not enough air outside to exchange with)

Hypoventilation (not breathing enough to excahange)

**High A-a Gradient Causes **

V/Q mismatch (not enough blood going to perfused space)

Diffusion limitation (gas cant exchange in lungs)

Right to left shunt (deoxygenated blood bypasses lungs)

Question 15

Causes of Hypoxia

Answer 15

Normal A-a grade

decreased cardiac output

Hypoxemia

**High A-a Grade **

anemia

cyanide

CO poisoning