Pulmonary

Question 1

What factors impact Resistance in your lungs?

Answer 1

Viscosity of inhaled air and Airway resistance (flow-dependent)

Question 2

What are the elastic properties of the lung?

Answer 2

Collagen and elastin

Question 3

Compliance

Answer 3

Stretch-ability. Measure of stiffness. Change in volume per unit change in pressure. /\V / /\P

Question 4

Transmural pressure

Answer 4

pressure across alveolar wall = intra-alveolar pressure minus extra alveolar pressure

Question 5

Extra-alveolar pressure

Answer 5

Intrapleural pressure as this is the space b/w lungs and chest wall

Question 6

Hysteresis

Answer 6

Feature of pressure volume loop for air filled lung. Lung is more compliant during expiration than inspiration. Surface tension at liquid-air interface of lung causes hysteresis

Question 7

Law of Laplace

Answer 7

Describes collapsing pressure on alveolus as it relates to surface tension (T) and radius (r).
P = 2T/r. A small alveolus will experience a greater inward force than a large alveolus, if their surface tensions are equal.

Question 8

Surfactant

Answer 8

Phospholipids. Reduces surface tension as charged molecules repel each other and reduces the collapsing pressure on the alveolus. Improves lung compliance

Question 9

What determines the compliance of the Respiratory System

Answer 9

Compliance of the Lung + the Compliance of the Chest Wall. Combined compliance is less than that of either structure alone.

Question 10

FRC (functional residual capacity)

Answer 10

Resting or equilibrium volume, volume present in lungs after a normal breath exhaled

Question 11

Intrapleural pressure

Answer 11

Slightly net negative pressure

Question 12

Emphysema

Answer 12

Increase in lung compliance due to a loss of elastic fibers. FRC is higher = barrel chested.

Question 13

Fibrosis

Answer 13

Decrease in lung compliance due to excessive collagen. Stiffness in the lung. FRC is below normal so chest is squished

Question 14

Resistance

Answer 14

Flow = /\P / Resistance. /\P is the pressure difference b/w mouth/nose and alveoli. Smaller the radius, smaller the resistance

Question 15

Sympathetic adrenergic

Answer 15

Fight or flight, beta2 receptors -> relaxation of the bronchial smooth muscle and bronchodilation

Question 16

Parasympathetic cholinergic

Answer 16

Muscarinic receptors -> airway narrowing or bronchospasm

Question 17

Pulmonary Vascular Resitance

Answer 17

Resistance = Pressure gradient / Flow

Question 18

PVR

Answer 18

Pressure differential between Pulm Artery and Left Atrial pressure / Flow. (mPAP - mLAP)/Cardiac Output

Question 19

Regulation of Pulmonary blood flow

Answer 19

Regulated by alterating resistance of arterioles. Change in resistance due to change in tone of ateriolar smooth muscle. Unique structue - even smaller pulmonary aterieoles have smooth muscle in their walls -> vasoconstriction

Question 20

What is the most important mediator of vasoconstriction?

Answer 20

Partial pressure of O2 in alveolar gas (PAO2)

Question 21

What is the response to low alv PAO2?

Answer 21

Tone of the arteriolar smooth muscle -> vasoconstriction

Question 22

Hypoxic vasoconstriction

Answer 22

When the vessels contract under low oxygen pressure in the alveolar. Unique to the lungs and protective which decreases perfusion (Q) to poorly ventilated (V) area -> reduced V/Q mismatch by directing blood flow away from damaged alveoli or poorly ventilated units.

Question 23

What are the mechanisms of hypoxic pulmonary vasoconstriction?

Answer 23

Reduced alveolar PAO2 (below 70 mmHg) -> inhibition of pulmonary arterial smooth muscle K+ channel -> depolization -> opens voltage gated Ca++ channels -> Ca++ influx -> smooth muscle contraction

Question 24

What are the mediators of hypoxic pulmonary vasoconstriction?

Answer 24

Nitric oxide is endothelial-derized relaxing factor -> activates cGMP -> relaxation of smooth muscle. Production of NO is affected by low PO2. Also PGI2 (arachidonic acid product)

Question 25

What mediators cause vasoconstriction?

Answer 25

Endothelin is a vasoconstrictor and TXA2 (arachidonic acid product)

Question 26

What happens to your lungs in high altitude?

Answer 26

Reduced barometric pressure -> decrease in inspired PO2 -> low alveolar PAO2 -> Global vasocontriction -> increase in PVR. Chronically over time, this causes RV pressure overload -> hypertrophy

Question 27

Zone 1 of the lungs

Answer 27

Apex of the lungs (top). Gravitational effects causes a lower arterial pressure Pa than compared to alveolar PA (atmospheric). Pulmonary arterioles can be compressed by higher alveolar pressure surrounding them. Closure of capillaries means least blood flow at apex. PA > Pa > Pv

Question 28

What is physiologic dead space?

Answer 28

When a zone of lung is underperfused which causes no gas exchange, but still is ventilated

Question 29

Zone 2 of the lungs

Answer 29

Gravitational effect in the middle of the lung on hydrostatic pressure causes arterial Pa > alveolar PA. Alveolar PA still higher than venous PV. Blood flow driven by arterial and alveolar pressure difference. Pa > PA > Pv

Question 30

Zone 3 of the lungs

Answer 30

Gravity increases both arterial Pa and venous Pv. Both are higher than alveolar PA. Blood flow is driven by arterial-venous difference. Capillaries are the most open, blood flow is highest. Pa > PV > PA

Question 31

Physiologic shunt

Answer 31

Portion of cardiac output divergent/re-routed, bypassing alveoli, no gas exchange. Accounts for 2% of cardiac output. Bronchial blood flow - blood supply to conducting airways - drains directly into left atrium. Coronary blood flow drains directly into left ventricle through thesbesian veins. This is the reason why arterial PaO2 always slightly < alveolar PAO2, diluting your arterial blood.

Question 32

Right to left shunt

Answer 32

Direct flow of blood right right sided heart chambers to left sided heart chambers and never passing through the lungs. Fraction of cardiac output is not delivered to the lungs for oxygenation or for arterilaization hypoxemia occurs (low PaO2)

Question 33

Arterialization Hypoxemia

Answer 33

Fraction of cardiac output that is not delievered to the lungs for oxygentation due to right to left shunt. Cannot be corrected by inhaling higher inspired O2.

Question 34

What happens to CO2 in a shunt?

Answer 34

Slight increase in arterial PaCO2 increases ventilatory rate and extra CO2 is expired. Central chemoreceptors are sensitive to changes in arterial PaCO2

Question 35

Left to right shunt

Answer 35

Oxygenated blood from left side of cirulation enter right side and recirculates through lungs. Pulmonary blood flow increases as part of left cardiac output enters right side. PO2 of right sided heart chambers is elevated

Question 36

What causes left to right shunt?

Answer 36

ASD, VSD, Patent ductus arteriosus