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Medicine Clerkship > Learning Objectives - Dyspnea + Pulmonary Tests > Flashcards

Learning Objectives - Dyspnea + Pulmonary Tests Flashcards

1
Q

List 6 common/serious cardiac causes of dyspnea.

A
  1. CHF
  2. CAD (MI)
  3. Pericardial disease (restrictive pericarditis or pericardial effusion w/tamponade)
  4. Arrhythmia
  5. Valvular heart disease
  6. Congenital heart disease
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2
Q

List 12 common/serious pulmonary causes of dyspnea.

A
  1. COPD
  2. Asthma
  3. PE
  4. Pneumonia
  5. Pleural effusion
  6. Malignancy
  7. ILD/fibrosis
  8. Bronchiectasis
  9. Pulmonary HTN
  10. Foreign body airway obstruction
  11. ARDS
  12. Pneumothorax
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3
Q

List 13 other common/serious causes of dyspnea.

A
  1. Renal failure (metabolic acidosis and volume overload)
  2. Anemia
  3. Obesity
  4. Neuromuscular disorders (MG, muscular dystrophy)
  5. Liver cirrhosis
  6. Thyroid disease
  7. Deconditioning
  8. Chest wall deformities (rib fracture, kyphoscoliosis)
  9. Psychogenic causes
  10. Sepsis
  11. DKA
  12. GERD
  13. Medication
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4
Q

List the 7 conditions that cause 85% of cases of dyspnea.

A
  1. Asthma
  2. CHF
  3. COPD
  4. Pneumonia
  5. Cardiac ischemia
  6. ILD
  7. Psychogenic conditions
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5
Q

Dry inspiratory crackles + clubbing?

A

Pulmonary fibrosis/ILD

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6
Q

Diminished lung excursion + rapid/shallow breathing +/- trouble swallowing/ptosis

A

Neuromuscular disease

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7
Q

Accentuated P2 heart sound, right ventricular heave, tricuspid murmur

A

Pulmonary HTN

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8
Q

Pulsus paradoxus definition and DDx?

A

Decrease in BP of >25 mmHg with inspiration

Severe asthma/COPD
Tamponade

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9
Q

99% of the time, hypoxemia is due to which 2 mechanisms?

What other mechanisms can cause hypoxia?

A 
VQ mismatch (#1)
Shunt
Diffusion impairment
Diffusion-perfusion impairment
Hypoventilation
Altitude
Decreased FiO2
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10
Q

Normal mixed venous O2 pressure?

Normal arterial O2 pressure?

Normal mixed venous CO2 pressure?

Normal arterial CO2 pressure?

A

40 mmHg

100 mmHg

45 mmHg

40 mmHg

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11
Q

What happens in VQ mismatch?

A

Decreased ventilation relative to perfusion

O2 exits the alveolus much more quickly than it enters via the bronchi

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12
Q

In VQ mismatch, is the hypoxia mild or severe? Does it improve with supplemental O2?

A

Mild; yes

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13
Q

Major causes of VQ mismatch?

A

Asthma, COPD
Pulmonary emboli
ILD

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14
Q

What happens in a sunt?

A

No O2 reaches some set of the pulmonary capillaries

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15
Q

In shunt, is the hypoxia mild or severe? Does it improve with supplemental O2?

A

Severe; no

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16
Q

Major causes of shunt?

A

Pulmonary shunt:

  • No ventilation to alveoli that are still perfused (filled with blood, pus, water or atelectasis)
  • Pulmonary AVM

Cardiac sunt: PFO, ASD, VSD

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17
Q

Most shunts are partial shunts, so there will be some response to oxygen. Name 2 types of complete shunts.

A

R to L intracardiac shunt (Eisenmenger’s syndrome)

Severe ARDS (majority of lung involved)

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18
Q

What happens in diffusion impairment?

A

Normally thin basement membrane between the alveoli and pulmonary capillary vessel thickens, leading to decreased diffusion of gases

Note - primarily affects O2, as CO2 is 20x more soluble and diffuses more easily

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19
Q

In diffuse impairment, is the hypoxia mild or severe? Does it improve with supplemental O2?

A

Mild; yes

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20
Q

Causes of diffusion impairment?

A

Not a common problem, because blood is normally fully oxygenated within 25% of its transit through the alveolar capillaries

Therefore, even if slowed by a diffusion barrier, blood usually reaches full saturation

-Exercise at altitude in a patient with fibrosis

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21
Q

What is diffusion-perfusion impairment and when is it seen?

A

Dilated capillaries pose an impairment to full oxygenation

Seen occasionally in cirrhosis (hepatopulmonary syndrome)

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22
Q

Why does hypoxia occur at high altitudes?

A

Atmospheric pressure is lower (percentage of oxygen in the air remains 21%)

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23
Q

Calculate the A-a gradient.

A

= PAlvO2 - PaO2

Alv - calculated
a - measured

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24
Q

Normal A-a gradient?

A

Less than Age/4 + 4

25
Q

What does an elevated A-a gradient suggest?

A

Something is decreasing the efficiency of oxygen transfer from the atmosphere to the arterial circulation

26
Q

Calculate PAlvO2.

A

[(Pb - PH2O) x FiO2] - (PaCO2/RQ)

First value = 150 if sea level and room air
Pb = 760, PH2O = 47, FiO2 = 0.21
Assume RQ = 0.8
PaCO2 from ABG

27
Q

How is the degree of hypoxia described?

A

P/F ratio = PaO2/FiO2

Normally ~100/0.2 = 500

Lower ratios imply worsening degrees of hypoxia

<200 counts as ARDS
<100 - severe ARDS

28
Q

How much oxygen is delivered to the tissues?

A

Product of CO and oxygen content

29
Q

Normal oxygen consumption? Normal oxygen delivery?

A

VO2 = 250 cc/min at rest

DaO2 = CO x CaO2 = 1000 mL O2/min

30
Q

What is an extraction ratio?

A

% of delivered oxygen actually consumed

31
Q

Evidence of inadequate delivery relative to consumption?

A

Decreased CmvO2
Increased Da-vO2
Increased extraction ratio

32
Q

FiO2 of oxygen delivered via nasal cannula?

A

24-44% FiO2

Increases ~3% for each additional L/min

33
Q

FiO2 of oxygen delivered via simple face mask?

A

40-60% FiO2

34
Q

FiO2 of oxygen delivered via non-rebreather mask (reservoir with a one-way valve)?

A

60-100% FiO2

35
Q

FiO2 of oxygen delivered via Venturi mask (includes a valve allowing for “precise” delivery)?

A

24-60% FiO2

36
Q

FiO2 of oxygen delivered via Optiflow (Nasal High Flow Oxygen) - heated and humidified, flushes out dead space, provides a tiny amount of CPAP

A

Up to 100% FiO2

37
Q

What does the PaCO2 depend on?

A

How much CO2 is produced vs. eliminated

Elimination depends upon alveolar ventilation (Total MV, dead space)

38
Q

Normal VCO2 (production)?

A

200 mL/min

Increases are NOT clinically relevant (unless there is a serious neuro problem)

39
Q

Normal MV?

A

5 L/min at rest, up to 100 L/min with maximum aerobic activity

40
Q

Dead space ventilation = ?

A

Vd/Vt

Percent of each tidal volume NOT participating in gas exchange

Anatomic dead space (air in trachea and bronchi down to the conducting airways) + physiologic dead space (not participating in gas exchange)

41
Q

Normal tidal volume?

A

500 cc

42
Q

Normal dead space?

A

1 cc/pound -> ~150 cc/pound

~30% of an average TV

43
Q

Causes of increased VD/VT?

A

Decreased perfusion of ventilated lung (pulmonary emboli, pulmonary HTN, volume depletion)

Increased alveolar pressure (PEEP - MV, auto-PEEP - emphysema)

44
Q

When should you think about dead space?

A 
Increased PaCO2 (hypercapnea)
Normal PaCO2 with increased MV
45
Q

Primary determinants of PFTs?

A

Age
Height
Sex
Race

NOT weight

46
Q

Obstructive PFT pattern?

A

Decreased FEV1/FVC ratio (<70%)

Both are decreased but FEV1 decreases more than FVC

47
Q

Causes of obstructive PFT pattern?

A

Asthma
COPD
Bronchiectasis

48
Q

Restrictive PFT pattern?

A

Decreased TLC

49
Q

Causes of restrictive PFT pattern?

A

ILD (95% of cases)
Chest wall disease
Neuromuscular disease

50
Q

Causes of decreased DLCO (diffusion capacity)?

A

Associated with COPD and/or ILD

If isolated, primary pulmonary HTN

51
Q

PFT findings consistent with reactive airway disease/asthma?

A

12% and 200CC increase in either FEV1 or FVC

52
Q

What determines O2 content?

A

Aka how much O2 is in the blood

Hgb, SaO2, PaO2

53
Q

What determines O2 delivery?

A

O2 content and cardiac output

54
Q

What determines O2 extraction?

A

Tissue’s metabolic activity

55
Q

PaCO2 = ?

A

VCO2/[MV x (1 - Vd/Vt)]

VCO2 = CO2 production
Vd/Vt = dead space
MV = minute volume
56
Q

Benefits of supplemental oxygen?

A

Only treatment that lowers mortality in COPD

May improve other outcome measures, including quality of life, CV morbidity, depression, cognitive function, exercise capacity, and frequency of hospitliztaion

57
Q

Potential dangers of overly aggressive O2 supplementation?

A

Absorptive atelectasis
Increased oxidative stress
Inflammation
Peripheral vasoconstriction

58
Q

List 9 causes of tachypnea.

A
  1. Exericse/exertion
  2. Lung disease (PE, asthma, COPD, pneumonia)
  3. Heart disease
  4. Anemia
  5. Anxiety
  6. CO poisoning
  7. Toxin-related metabolic acidosis
  8. DKA
  9. Sepsis

Medicine Clerkship (15 decks)

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