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Anesthesia > Pulmonary > Flashcards

Pulmonary Flashcards

1
Q

What is physiologic dead space?

A

Anatomic (nasal, oropharynx, terminal & respiratory bronchioles) and alveolar; ~2 ml/kg (150 ml)

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2
Q

shunt fraction equation? Normal percentage?

A

Qs/Qt = (CcO2 - CaO2)/(CcO2 - CvO2); CcO2 is pulmonary capillary O2 content, CvO2 is mixed venous O2 content; 4-5%

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3
Q

Dead space equation, amount

A

Vd/Vt = (PaCO2 - PETCO2)/PaCO2; ~300 ml

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4
Q

Alveolar gas equation

A

PAO2 = FiO2(Patm - PH2O) - PaCO2/0.8

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5
Q

Right shift oxyhemoglobin dissociation curve (4)

A

High CO2, high H+, high temp, high 2,3 DPG (anemia, cirrhosis, increased altitude)

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6
Q

Left shift oxyhemoglobin dissociation curve (7)

A

Low CO2, low H+, low temperature, low 2,3 DPG, fetal hemoglobin, methemoglobin, carboxyhemoglobin

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7
Q

What is FRC?

A

ERV + RV

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8
Q

When does FRC decrease? (6)

A

Pregnancy, ascites, neonates, GA, obesity, supine position

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9
Q

When does FRC increase?

A

PEEP and emphysema

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10
Q

What happens when closing capacity is greater than FRC?

A

Shunting

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11
Q

What is closing capacity?

A

CC = CV + RV; volume at which small airways in the lung close

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12
Q

When does CC increase?

A

Age, chronic bronchitis, LV failure, surgery, smoking, obesity

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13
Q

When is closing capacity lowest?

A

During teenage years

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14
Q

Arterial O2 content equation

A

CaO2 = (1.34 x HgB x sat) + (0.003 x PaO2)

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15
Q

What is the P50?

A

Partial pressure of oxygen at which hemoglobin is 50% saturated

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16
Q

P50 adults? Infants?

A

27 mm Hg and 19 mm Hg

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17
Q

Partial pressure and O2 sat of mixed venous?

A

40 mm Hg and 75%

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18
Q

Partial pressure at 90% sat?

A

60 mm Hg

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19
Q

What happens with a right shift in the Oxy-Hb curve?

A

Increased unloading of oxygen to tissues

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20
Q

What happens with a left shift in the Oxy-Hb curve?

A

Decreased unloading of oxygen to tissues

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21
Q

What is the Bohr effect?

A

Oxy-Hb dissociation curve shifts with changes in CO2

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22
Q

What is the Haldane effect?

A

The more deoxygenated blood is the more CO2 (in the form of carbamino compounds) it can carry without altering the PaCO2

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23
Q

Where should mixed venous O2 sat be measured?

A

Pulmonary artery

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24
Q

What is normal PvO2 and sat?

A

35-45 mm Hg and 65-75% sat

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25
Q

What factors determine PvO2?

A

Cardiac output, O2 consumption, amount of hemoglobin, loading of hemoglobin

26
Q

What do carotid and aortic bodies respond to and what are their effects?

A

Respond to PaO2 levels lower than 60 (not low O2 content/sat) carotid bodies impact ventilation and aortic bodies impact circulation

27
Q

Where are chemosensitive areas in brainstorm located? What nerves are nearby?

A

Medulla, close to IX glossopharyngeal and X vagus

28
Q

Describe CO2 response curve and its parameters

A

Ventilatory response is linear between CO2 20-80, CO2 becomes ventilatory depressant >100

29
Q

What does left shift of CO2 curve indicate and what causes it?

A

Indicates increased sensitivity to CO2; arterial hypoxemia, metabolic acidemia, central causes (increased ICP, anxiety, fear, cirrhosis)

30
Q

What does right shift of CO2 curve indicate and what causes it?

A

Indicates decreased sensitivity to CO2; aminophylline, salicylates, catecholamines, narcotics, physiologic (metabolic alkalemia, denervation of peripheral chemoreceptors, normal sleep, drugs)

31
Q

What causes a down and right CO2 curve shift?

A

High dose narcotics, volatile anesthetics (with higher doses curve flattens with little CO2 response)

32
Q

Zone 1

A

PA > Ppa > Ppv

33
Q

Zone 2

A

Ppa > PA > Ppv

34
Q

Zone 3

A

Ppa > Ppv > PA

35
Q

FiO2 - PaO2 relationship

A

Every 10% increase in FiO2 equals 50 torr PaO2 increase

36
Q

What is hypoxic pulmonary vasoconstriction? Causes?

A

Regional pulmonary vasoconstriction in response to regional lung hypoxia (PAO2); mixed venous <30 indirectly induces HPV

37
Q

Benefits of HPV

A

Decreases shunting by decreasing blood flow by 50%

38
Q

What decreases HPV response? (10)

A

Increased pulmonary vascular pressure, increased cardiac output, hypocapnea, acidosis, alkalosis, hypothermia, CCB, nitroprusside, isoproterenol, high frequency ventilation

39
Q

What inhibits HPV?

A

Inhaled anesthetics, nitrous

40
Q

Define dead space

A

Ventilation with no perfusion; V/Q ratio is infinity

41
Q

Define shunt

A

Perfusion with no ventilation; V/Q ratio is 0

42
Q

Altitude

A

Inspired O2 diminishes as altitude increases and barometric pressure decreases

43
Q

A-a gradient

A

About 1/4 patients age

44
Q

RA normal A-a gradient?

A

5-10 mm Hg

45
Q

100% A-a gradient?

A

20-30 mm Hg

46
Q

What causes shunt?

A

Thesbian veins, bronchial veins, R-L intracardiac shunt, pneumothorax, bronchospasm, pneumonia

47
Q

How does shunt affect PaO2 and PaCO2?

A

Linear decline in PaO2 with shunting. PaCO2 does not increase until shunt fraction exceeds 50% (because of increased solubility of CO2)

48
Q

Why does A-a gradient increase under GA?

A

Decreases in cardiac output, FRC, lung and chest wall compliance. Airway resistance is increased.

49
Q

When FRC greatest after surgery? How long does decrease last?

A

Greatest 3-5 days post (most severe with upper abdominal) and lasts 10-14 days

50
Q

How much O2/min is removed from alveoli? CO2 produced?

A

250 ml/min O2 removed; 200 ml/min CO2 produced

51
Q

What is the treatment for pulmonary edema?

A

100% O2, PEEP, nitroglycerin to reduce preload, inotrope to increase cardiac contractility, LASIK, fluid restriction, PA catheter

52
Q

What causes pulmonary edema? (4)

A
  1. Increased capillary pressure - mitral stenosis, heart failure, fluid retention, negative pressure pulmonary edema 2. Increased capillary leak - aspiration, ARDS, burn, neurogenic 3. Decreased oncotic pressure - low albumin from burn/poor nutrition 4. Lymphatic obstruction - tumor
53
Q

What symptoms are associated with cardiogenic pulmonary edema?

A

Bibasilar rales, patchy infiltrates, and pink, frothy sputum, high PCWP

54
Q

What causes non-cardiogenic pulmonary edema? Symptoms?

A

Massive blood transfusion, smoke inhalation, sepsis, DIC; bibasilar rales

55
Q

Pulmonary vascular resistance equation

A

PVR =

56
Q

What causes pulmonary HTN? (3)

A

Increased blood flow - L-R cardiac shunt; increased pulm resistance - hypoxia, hypercarbia, acidosis, lung disease, pulm vascular bed destruction, embolism; increased backward pressure - mitral stenosis/regurg

57
Q

How does smoking cause hypoxia?

A

It increases closing capacity relative to FRC

58
Q

What happens after 24-48 hours after smoking cessation? One week? Months?

A

Decrease carboxyhemoglobin levels to normal (2.5%), corrects left shift of oxy-hemoglobin curve. Decreased pulm secretions. Normal mucociliary clearance.

59
Q

Post-op complications associated with smoking?

A

Atelectasis, pneumonia, hypoxia

60
Q

How many weeks are needed of smoking cessation to decrease chance of postoperative pulm complications?

A

6-8 weeks

61
Q

What is nitric oxide?

A

Endothelial derived relaxin factor that vasodilates smooth muscle

62
Q

How is NO deactivated?

A

Binding to hemoglobin

Anesthesia (16 decks)

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