Intro to Pulm Physiology

Question 1

Answer 1

Gas flow rate

Question 2

E

Answer 2

expired gas

Question 3

I

Answer 3

inspired gas

Question 4

A

Answer 4

alveolar gas

Question 5

a

Answer 5

arterial blood

Question 6

v

Answer 6

venous blood

Question 7

Answer 7

mixed venous blood = pulmonary arterial blood, bc it’s a mixture of all the venous blood from all over the body

Question 8

What is the difference between ventilation, gas exchange, and gas transport?

Answer 8

Ventilation = Atmosphere <–> Alveolar space

Gas exchange = Alveolar space <–> Blood

Gas transport = Blood <–> Tissues

Question 9

Hypercapnia

Answer 9

Too much CO2 in the blood

Leads to increased cerebral blood flow/intracranial pressure, acedemia

Question 10

Hypoxemia

Answer 10

Not enough O2 in the blood

Leads to tissue hypoxia, inhibition of cellular aerobic respiration, death

Question 11

What is the relationship between partial pressure of a gas and the fraction of the gas? Equation?

Answer 11

Partial pressure and fraction of gas are directly proportional

P_gas = F_gas x P_total

Question 12

What is atmospheric pressure at sea level?

Answer 12

760 mmHg

Question 13

What makes inspired gas different than atmospheric gas?

Answer 13

Your body warms it up and adds water vapor to saturate it

Question 14

How much partial pressure of water vapor is added to air that you breathe in?

Answer 14

47 mmHg

Question 15

Negative pressure ventilation

Answer 15

Subatmospheric pressures in the chest generate air flow

“spontaneous” breathing = tidal breathing

Iron lung

Question 16

Positive pressure ventilation

Answer 16

Suparatmospheric pressure outside the chest generate air flow

Machine/ventialator does this

Question 17

What is normal RR?

Answer 17

10-16 breaths per minute

Question 18

Tidal volume = VT

Answer 18

Volume of gas inspired in a normal breath

About 0.5 L

Question 19

Minute ventilation

Answer 19

Volume of gas expired or inspired in a minute

About 6-7 L/min

Question 20

Tachypnea

Answer 20

Increased RR

Question 21

Hypopnea

Answer 21

Small tidal volume

Synonymous to shallow breathing

Question 22

Dead space

Answer 22

Ventilated but does not participate in gas exchange

Question 23

Anatomic dead space

Answer 23

Normal, part of your anatomy

Includes trachea, bronchi, bronchioles

About 1 ml/lb ideal body weight

Question 24

Physiologic Dead Space

Answer 24

Anatomic dead space + diseased areas not participating in gas exchange

Question 25

Which parts do participate in gas exchange?

Answer 25

Alveolar space = respiratory bronchioles, alveolar ducts, alveolar sacs

Question 26

What is the relationship between minute ventilation, dead space ventilation, and alveolar ventilation?

Answer 26

Where V(dot)_E = minute ventilation V(dot)_D = dead space ventilation V(dot)_A = Alveolar ventilation

Question 27

What are the 4 main ways that alveolar ventilation are regulated?

Answer 27

peripheral chemoreceptors (CO2, O2, H⁺), central chemoreceptors (H⁺), lung stretch receptors, muscle and joint receptors Includes: inspiratory inhibition reflex/Hering-Breuer reflex, Irritant receptors, J receptors (respond to pulm edema)

Question 28

What is the strongest influence of control over breathing?

Answer 28

Central chemoreceptors: sense H+ in brain arterial blood If pH goes down, tells your body to breathe faster

Question 29

What is the relationship between CO2 and H+ in the blood?

Answer 29

CO₂ \<--\> H₂CO₃ \<--\> H⁺ + HCO3^- If CO2 levels rise, then H+ levels increase and pH goes down, which is a signal to the brain to increase ventilation

Question 30

What can the peripheral chemoreceptors sense?

Answer 30

Located in carotid and aortic bodies Elevated H+ (low pH) Increase in arterial PCO2 Decrease in arterial PaO2

Question 31

What is the best way to measure alveolar ventilation?

Answer 31

Measure alveolar CO₂! Unlike O2, it's pretty constant: there is no inspired CO₂ Transferred VCO₂ messes with the value of V_CO2 a little bit BUT the rate of transfer of CO2 from pulm circ/tissue to alveolus is **constant** when you are at rest

Question 32

What is the equation for partial pressure of CO₂ in the alveolus?

Answer 32

P_ACO₂ = 863 x V_(dot)CO₂/V_(dot)A The amount of **CO2 in your alveoli** is: * _directly proportional_ to the amount of **CO2 moving from capillary blood to alveolus** (this is your "*input*" of CO2) * _inversely proportional_ to your **alveolar ventilation** (this is your "*drainage*:" if you increase alveolar ventilation, you'll take more CO2 out of the lung & ppCO2 will go down)

Question 33

What is a simplified version of the equation for PCO₂? Why can we rewrite the equation in this way?

Answer 33

P_ACO₂ = K'/V_(dot)A Because V_(dot)CO₂ is constant at rest

Question 34

What is the easiest way to calculate alveolar flow?

Answer 34

V(dot)_A = K'/P_aCO₂ We can measure **arterial PCO2**!!! Alveolar PCO2 = arterial PCO2 because the CO2 has equilibrated between the alveolus and pulmonary capillary PCO2, which becomes pulmonary venous & becomes left atrial & aortic & all the arteries

Question 35

What is the normal range for P_aCO₂ (arterial)?

Answer 35

37-42 mmHg

Question 36

What does low PaCO2 indicate?

Answer 36

Less than 37 mmHg Hypocapnia/hypocarbia Due to **alveolar hyperventilation**

Question 37

What does high alveolar PaCO2 indicate?

Answer 37

Hypercapnia/hypercarbia: elevated alveolar PCO2 Due to **alvolar hypoventilation**

Question 38

What causes alveolar hyperventilation?

Answer 38

Hypoxemia Acidemia Stimulation of lung receptors Drugs: aspirin, progestins Pain Anxiety Fever Pregnancy Exercise Note: hypercapnia causes increased respiratory drive but it's impossible to have both hypercapnia and alveolar hyperventilation at the same time

Question 39

What are signs of increased work of breathing?

Answer 39

Accessory muscle use Tachypnea Nasa flaring Paradoxical breathing: when belly moves in while chest moves out secondary to diaphragmatic weakness which is due to muscle fatigue

Question 40

What can cause alvolar hypoventilation?

Answer 40

Decreased respiratory drive/effort (drugs, sleep, breath holding) Neuromuscular incompetence i.e ALS patient with weak muscles Muscle fatigue due to increased load i.e. AIDS patient has increased dead space due to pneumonia Loss of respiratory system integrity (crushed chest, complete airway obstruction)

Question 41

What are sources of dead space that's not normal?

Answer 41

Adding external dead space: scuba, ventilator tubing, breathe through a straw New dead space created from alveolar space: due to a pulmonary embolism that blocks blood flow to a section of alveoli

Question 42

Why does increased dead space due to pulmonary embolism lead to alveolar hypoventilation?

Answer 42

Normal homeostasis leads to increased PaCO2 which leads to increased minute ventilation and increased alveolar ventilation which ultimately brings down the PaCO2 to normal levels But when you have dead space due to pulmonary embolism, you get increased PaCO2 which leads to increased minute ventilation & increased ventillation of the dead space --\> eventually you get increased work of breathing & your muscles get fatigued --\> alveolar hypoventilation