Respiratory - FA p646-656

Question 1

Answer 1

Question 2

Formula to find O2 content of blood?

Answer 2

(1.34 × Hb × Sao2) + (0.003 × Pao2)

Question 3

Formula for minute ventilation

Answer 3

Total volume of gas entering lungs per minute
V_E = V_T × RR

Question 4

How does O2 sat and PAO2 change with dec Hgb?

Answer 4

There is no change in either one, the only change is with normal O2 content in arterial blood (PaO2).

Hb decreased

PaO2 is normal

Question 5

Alveolar ventilation

Answer 5

Volume of gas that reaches alveoli each minute

V_A = (V_T − V_D) × RR

Question 6

What disease cause an increase in total O2 content?

Answer 6

Polycythemia

Question 7

In which disease will there be dec O2 sat’n but normal Hgb?

Answer 7

CO poisoning

Question 8

Diffusion equation

Answer 8

Diffusion:

V˙ gas = A × Dk × [(P1 – P2)/T]

A = area,

T = alveolar wall thickness,

Dk(P1 – P2) ≈ difference in partial pressures:

Question 9

When is area decreased? when is alveolar wall thickness inc?

Answer 9

Emphysema, Pulm fibrosis

Question 10

At ___, inward pull of lung is balanced by outward pull of chest wall, and system pressure is _________.

Answer 10

At FRC, inward pull of lung is balanced by outward pull of chest wall, and system pressure is atmospheric.

Question 11

Dec in paO2 causes what in lung a/v?

Answer 11

VC (diff from systemic circ)

Question 12

PVR formula (pulm vas resistance)

Answer 12

PVR =( Ppulm artery – P L atrium)/Cardiac Output

Question 13

T or F Both ventilation and perfusion are greater at the base of the lung than at the apex of the lung.

Answer 13

True

Question 14

How does ventilation and perfusion change with exercise?

Answer 14

With exercise (INC cardiac output), there is vasodilation of apical capillaries –> Ž V˙/Q˙ ratio approaches 1.

Question 15

Respiratory rate (RR)

Answer 15

12–20 breaths/min

Question 16

Tidal volume

Answer 16

500 mL/breath

Question 17

Physiological dead space

Answer 17

150 mL/breath

Question 18

Formula to determine dead space, define dead space

Answer 18

.VD = physiologic dead space = anatomic dead space of conducting airways plus alveolar dead space; apex of healthy lung is largest contributor of alveolar dead space. Volume of inspired air that does not take part in gas exchange. VT = tidal volume. Paco2 = arterial Pco2. Peco2 = expired air Pco2

Question 19

Cl−, H+, CO2, 2,3-BPG, and temperature cause what change in Hgb and O2?

Answer 19

favor taut form over relaxed form (shifts dissociation curve right O2 unloading).

Question 20

T or F Myoglobin has higher affinity for O2 > Hgb

Answer 20

True

Question 21

MoA of Cyanide/CO poisoning

Answer 21

Both inhibit aerobic metabolism via inhibition of complex IV (cytochrome c oxidase) –> hypoxia unresponsive to supplemental O2 and inc anaerobic metabolism

Question 22

Treatment of CN poisoning?

Answer 22

Hydroxocobalamin (forms cyanocobalamin) or induced methemoglobinemia with nitrites and sodium thiosulfate.

Question 23

Cyanide is found in ?

Answer 23

synthetic product combustion, ingestion of amygdalin (cyanogenic glucoside found in apricot seed)

Question 24

Presentation of CO poisoning?

Answer 24

headaches, dizziness, and cherry red skin.

Question 25

Treatment for CO poisoning?

Answer 25

100% O2, Hyperbaric O2

Question 26

What CNS lesion is seen with CO poisoning?

Answer 26

Classically associated with bilateral globus pallidus lesions on MR

Question 27

What is methemoglobin?

Answer 27

Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has inc affinity for cyanide.

Question 28

Methemoglobinemia - presentation and Tx?

Answer 28

Methemoglobinemia may present with cyanosis and chocolate-colored blood

methylene blue and vitamin C.

Question 29

R shift of O2 curve - what does it mean? causes?

Answer 29

dec Hb affinity for O2 (facilitates unloading of O2 to tissue)

R shift = get Rid of O2

Inc H+ ( dec pH, Acid)
Inc PCO₂
Inc 2,3–BPG
Exercise
High Altitude
Inc Temperature

Question 30

L shift of O2 curve means? Causes?

Answer 30

dec unloading into tissues

inc pH
dec PCO2
dec temp

dec 2,3 BPG
Inc CO, Met Hb, HbF

Question 31

How does the body compensate for left shift?

Answer 31

dec O2 unloading –> renal hypoxia –> inc EPO synthesis –> erythrocytosis

Question 32

Dec of PAO2 causes what?

Answer 32

DEC in PAO2 causes a hypoxic vasoconstriction that shifts blood away from poorly ventilated regions of lung to well-ventilated regions of lung.

Question 33

Which gases are perfusion limited and which are diffusion limited?

Answer 33

Perfusion - O2 (normally), CO2, N2 - exchange can only inc if blood flow inc

Diffusion limited - O2 (emphysema, fibrosis, exercise) & CO

Question 34

Why does fetal Hgb shift the curve L?

Answer 34

Fetal Hb has higher affinity for O2 than adult Hb (due to low affinity for 2,3-BPG), so its dissociation curve is shifted left.

Question 35

Increased parameters in elderly

Answer 35

Lung compliance (loss of elastic recoil)
RV
V ˙/Q ˙ mismatch
A-a gradient

Question 36

Decreased parameters in the elderly

Answer 36

Chest wall compliance (inc chest wall stiffness)
FVC and FEV1
Respiratory muscle strength (can impair cough)

ventilatory response to hypoxia/hypercapnia

Question 37

How does CN/CO affect the O2 Sat curve?

Answer 37

CN - Curve normal; oxygen saturation may appear normal initially.

CO - inc oxygen-binding capacity with left shift in curve, dec O2 unloading in tissues. ( Binds competitively to Hb with 200× greater affinity than O2 to form carboxyhemoglobin. )

Question 38

When is A-a gradient normal / Inc?

Answer 38

Normal A-a gradient = 10-15 nmHg

A-a gradient may occur in hypoxemia; causes include R–> L shunting, V˙/Q˙ mismatch, fibrosis (impairs diffusion)

Question 39

Causes of Hypoxia

Answer 39

DEC cardiac output
Hypoxemia
Anemia
CO poisoning

Question 40

Causes of Hypoxemia (DEC PaO2)

Answer 40

Normal A-a gradient
ƒHigh altitude
ƒHypoventilation (eg, opioid use)

INC A-a gradient
ƒ V˙/Q˙ mismatch
ƒDiffusion limitation (eg, fibrosis)
ƒ Right-to-left shunt

Question 41

Ischemia (loss of blood flow)

Answer 41

Impeded arterial flow

dec venous drainage

Question 42

CO2 is transported from tissues to lungs in what forms?

Answer 42

HCO3− (90%). ƒƒ Carbaminohemoglobin or HbCO2 (5%). CO2 bound to Hb at N-terminus of globin (not heme). CO2 binding favors taut form (O2 unloaded). ƒƒ Dissolved CO2 (5%).

Question 43

Bohr Effect?

Answer 43

In peripheral tissue, inc H+ from tissue metabolism shifts curve to right, unloading O2 (Bohr effect).

Question 44

haldane effect?

Answer 44

In lungs, oxygenation of Hb promotes dissociation of H+ from Hb. This shifts equilibrium toward CO2 formation; therefore, CO2 is released from RBCs

Question 45

Majority of blood CO2 is carried as _____ in the plasma.

Answer 45

Majority of blood CO2 is carried as HCO3− in the plasma.

Question 46

Initial Body response to high altitude - what metabolic disturbance

Answer 46

dec atmospheric oxygen DEC (PiO2) –> dec PaO₂ –> INC ventilation –> PaCO₂ –> respiratory alkalosis –> altitude sickness.

Question 47

Other body responses to high altitude What two things do we produce more of? What happens in the kidney? on a cellular level?

Answer 47

• Inc erythropoietin –> Inc hematocrit and Hb (chronic hypoxia).
• Inc 2,3-BPG (binds to Hb so that Hb releases more O2).
• Cellular changes ( Inc mitochondria).
• Inc renal excretion of HCO3− to compensate for respiratory alkalosis (can augment with acetazolamide).
• Chronic hypoxic pulmonary vasoconstriction results in pulmonary hypertension and RVH.

Question 48

Response to Exercise

Answer 48

INC CO2 production.
INC O2 consumption.
INC ventilation rate to meet O2 demand.
V ̇/Q ̇ ratio from apex to base becomes more uniform.
INC pulmonary blood flow due to INC cardiac output.

Question 49

What happens to pH in exercise?

Answer 49

Dec due to lactic acid

Question 50

How do gas values change in exercise? (PaO2, PaCO2, v CO2/o2 content)

Answer 50

No change in paO2, and PaCO2, but INC venous CO2, and dec venous O2