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revision > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

What are the contraindications for spirometry?

A

Haemoptysis of unknown cause
Pneumothorax
Unstable cardiovascular status
Recent MI or PE
Thoracic/abdo/ocular aneurysm
Recent thoracic/abdo/ocular surgery
Nausea/vomiting

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2
Q

What is the expected annual decline in FEV1 each year?

A

Approx 25ml/year

Nb. healthy pt expires 80% of lung volume in first second

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3
Q

What measurements would make spirometry reproducible?

A

3xFEV1 + FVC within 150ml
Max 8 tries
Difference of 5% between insp and exp volume allowed

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4
Q

What are spirometry criteria for obstructive airways disease?

A

FEV1/FVC <0.7

<0.65 if over 65

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5
Q

What does flow-volume loop look like in obstructive airways disease?

A

Scalloped expiration

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6
Q

What does flow-volume loop look like in coughing?

A

Sudden drops of flow rate to 0 before returning back to curve

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7
Q

What does flow-volume loop look like in exercise-induced asthma?

A

Gets smaller each time

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8
Q

What is the underlying cause of a flow volume loop where the fastest flow is reach after 0.1 seconds? E.g more even looking curve up and down in expiration?

A

Poor technique - expired too slow. Should get fastest rate (PEFR) within 0.1 seconds

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9
Q

What is the z-score on spirometry?

A

Number of standard deviations away from mean. Normal is within 1.64

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10
Q

What does flow-volume loop look like in restrictive lung disease?

A

Normal shape but don’t reach FVC

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11
Q

What is the diagnosis in a flow volume loop with a flattened inspiratory curve?

A

Variable extrathoracic obstruction
- vocal cord paralysis
- extrathoracic goitre
- laryngeal tumour

–> expiratory part normal as obstruction pushed outwards by force of expiration

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12
Q

What is the diagnosis in a flow volume loop with a flattened expiratory curve?

A

Variable intrathoracic obstruction?
- Tracheal tumour

–> inspiratory part normal as tumour sucked out during inspiration

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13
Q

What is the diagnosis in a flow volume loop with flattened inspiratory and expiratory curves?

A

Fixed large airway obstruction
- Tracheal stenosis
- Circular tracheal tumour
- Granulomatosis with polyangitis

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14
Q

A patient with COPD is going on holiday and asks re air travel. His SATS are 96% on air. He gets breathless when hurrying on the level. What assessment does he need?

A

None (nb. MRC 2)

If SATS ≥95% on RA and MRC ≤ 2, then no hypoxic challenge or oxygen required

MRC 1 - SOB on vigourous exercise
2 - hurrying level or walking up slight hill
3 - slower than ppl of same age or stop while walking on level
4 - stop after 100m
5- can’t leave house or SOB on dressing

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15
Q

A patient with COPD is going on holiday and asks re air travel. His SATS are 93% on air. He has to stop to catch his breath after 100m. He has a hx of T2RF but doesn’t use NIV. What assessment does he need?

A

Hypoxic challenge (unless already done and no recent hospital admissions, exacerbations or significant changes to treatment)

Results - if PaO2 ≥6.6 or SATS ≥85% (90 for CF) then nothing. Otherwise needs O2 to get above this.

Nb. MRC score irrelevant (4 in this case) as SATS <95% on air. If were above, then if MRC ≥3, would need 6MWT/shuttle walk.

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16
Q

A patient with COPD is going on holiday and asks re air travel. His SATS are 93% on air. He has no hx of T2RF. What assessment does he need?

A

None - can safely be given 2 litres O2 on plane.

  • if at risk of T2RF, would need hypoxic challenge
  • if already on LTOT, then would get 2 litres more than normal setting (would still need hypoxic challenge if T2RF)
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17
Q

A patient with COPD is going on holiday and asks re air travel. His SATS are 96% on air. He gets breathless when while walking on a level. What assessment does he need?

A

MRC 3 therefore needs 6MWT/shuttle walk - if SATS <84% + hx/risk of T2RF, then hypoxic challenge. Otherwise 2litres O2.

MRC 1 - SOB on vigourous exercise
2 - hurrying level or walking up slight hill
3 - slower than ppl of same age or stop while walking on level
4 - stop after 100m
5- can’t leave house or SOB on dressing

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18
Q

What SATS would you expect a healthy person to have on a plane?

A

> 90%

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19
Q

Does pt who has had previous significant intolerance to plane travel e.g. emergency O2/diversion need hypoxic challenge?

A

No - can give 2litres O2. Unless T2RF risk then needs.

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20
Q

Pt has severe asthma and symptoms not controlled. Want to travel on plane. Do they need tests?

A

Yes - need hypoxic challenge

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21
Q

Pt has lung disease and FEV1<50%. Do they need tests?

A

Yes. Hypoxic challenge

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22
Q

Pt has ILD. Wants to travel on plane. What do you need to know?

A

Needs hypoxic challenge if rest PaO2 ≤9.42 or TLCO≤50% and SATS<95% with 6MWT or shuttle walk

If already on LTOT then can just increase by 2 litres

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23
Q

Pt has resp muscle weakness or chest wall deformity. What are indications for hypoxic challenge?

A

FVC <1litre (or risk/hx of T2RF)

Results - if PaO2 ≥6.6 or SATS ≥85% (90 for CF) then nothing. Otherwise needs O2 to get above this.

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24
Q

How long after thoracic surgery can pt travel on plane?

A

4 weeks (2 weeks if essential)

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25
Q

How do you manage asthma/copd exacerbation on board plane?

A

Normal inhalers

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26
Q

How long after PNX can pt travel on plane?

A

1 week after CXR resolution

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27
Q

How long after interventional bronch (transbronch biopsy, EBUS, valves etc) can pt travel on plane?

A

1 week

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28
Q

Pt smear +ve TB. How long before can travel on plane?

A

2xsmear negative.
If MDR/XDR then 2xculture negative + clinical improvement

29
Q

Pt smear -ve TB (or unknown). How long before can travel on plane?

A

2 weeks after treatment (no restriction if extra-pulmonary TB)

30
Q

MDR/XDR TB. How long before can travel on plane?

A

2xculture negative + clinical improvement

31
Q

Extrapulmonary TB. How long before can travel on plane

A

No restriction

32
Q

Pt has pneumonia. How long before travel on plane?

A

1 week if SATS <94%

33
Q

Pt has OSA and uses CPAP. What are suggestions for plane travel?

A

Bring CPAP and use if overnight flight

34
Q

Pt has DVT/PE. Should they travel on plane?

A

Should delay 2 weeks

35
Q

Pt has pulmonary HTN. NY heart class 3/4. What do they need for plane travel?

A

2 litres O2 or hypoxic challenge if concerns of T2RF. Double rate if on LTOT

Nb. NYHA 3/4 = SOB on less than ordinary activity or at rest

36
Q

Can pt with lung cancer/mesothelioma travel on plane?

A

Suggest not during chemo due to ifx risk but otherwise no rules outside of other conditions

37
Q

What are contraindications for plane travel with respect to resp disease?

A

Untreated resp failure
Untreated PNX
Active infectious risk
Bronchogenic cyst

Nb. O2>4litres no longer a restriction

38
Q

What is a normal RV/TLC ratio?

A

<0.35 - if over, suggests air trapping e.g. obstructive airways disease

39
Q

What kind of spirometry is found in obesity?

A

Restrictive defect
- low functional residual capacity (volume left after normal tidal volume breath out)
- RV/TLC likely normal

40
Q

What are the grades of severity of restrictive lung disease based on spirometry?

A

Mild: FVC≥70%
Moderate: ≥60% but <70%
Moderately severe: ≥50% but <60
Severe: ≥34% but <50
Very severe: <34%

41
Q

What is pt exposed to in hypoxic challenge?

A

Gas mixture with 15% O2 for 20 mins or in equilibrium

42
Q

What spirometry findings might you get in diaphragmatic weakness?

A
  • FVC 75% unilateral, <50% bilateral.
  • marked fall in supine position (healthy person drop only 5%) –> 30% drop considered severe
43
Q

What are the criteria for reversibility on spirometry?

A

> 12% and 200ml

44
Q

What is a methacholine challenge?

A

Test for bronchial hyperresponsiveness - test what concentration of methacholine required to get fall in FEV1 of 20% (PC20). >16mg/mL = excludes airway hyperresponsiveness

Nb. histamine challenge should also stimulate if hyperresponsive

45
Q

What is best way to test for exercise-induced asthma?

A

Eucapnic voluntary ventilation (breath fast with gas mixture O2 21% and CO2 5% to mimic exercise, looks for drop in FEV1 of 10% within 20 mins)

Second best is exercise test, then nebuliser challenge

46
Q

What is the Empey ratio?

A

FEV1 in ml/PEFR in L per min
Can be used to see if upper airways obstruction. Normal result is <10

E.g. 2500 / (600x60)

47
Q

What is a normal A-a gradient?

A

FiO2 (e.g. 21) - (paCO2/0.8) - paO2

Normal in region of 1-3 (1-2 young/middle age, 2-3 elderly)

  • normal gradient but hypoxic = alveolar hypoventilation. Will get elevated PaCO2 (CNS depression, OHS, COPD, high altitude)
  • if V/Q mismatch, shunt or impaired diffusion then will be elevated
    –> dead space ventilation (ventilation without perfusion) e.g. pneumonia, PE, asthma, COPD
    –> shunt (perfusion without ventilation) e.g. pulmonary oedema, ARDS, pneumonia
    –> diffusion limit e.g. ILD
48
Q

What is a normal end-expiratory pressure?

A

-4kPa

49
Q

Where are ventilation and perfusion highest in the lung?

A

Both at bases
- Perfusion decreases faster than ventilation towards apices, therefore V/Q highest in apices
- lower V/Q tends towards shunts, where as higher V/Q tend towards dead space

50
Q

What causes low DLCO?

A

ILD
Emphysema
Severe anaemia
PEs
Increased carboxyhaemoglobin
Hypothyroid
CCF

NB. normal/high KCO = extrapulmonary restriction e.g. obesity, neuromuscular disease, pleural disease, kyphoscoliosis, post-pneumonectomy

51
Q

What causes high DLCO?

A

Pulmonary haemorrhage
Polycythaemia
Obesity
High altitude
Hyperthyroidism
Pneumonectomy
AV malformation (or other L-R shunt)

52
Q

What is the relationship between PaO2 and FiO2 in normal lungs?

A

PaO2 = FiO2 x 0.75

  • Normal FiO2 = 21%
53
Q

What increase in 6MWT is considered a good outcome for pulmonary rehab?

A

50m

54
Q

CPET testing - what is the RER?

A

Respiratory Exchange ratio
- VCO2/VO2
- Would expect VCO2 to increase with exercies
- At rest, ratio 0.8
- Hard exercise 1.1
- May also go up in hyperventilation

55
Q

CPET testing - what is VO2?

A

Oxygen consumption
- Would expect >80% to be considered normal

Nb. O2 pulse = oxygen concentration/HR (if low, suggestive of cardiac problem)

56
Q

CPET testing - what is anaerobic threshold?

A

Point where VCO2 faster than VO2 (usually when RER = 1)
- 50% is normal
- <40% considered disease state

57
Q

CPET testing - what is ventilatory equivalence/VCO2 slope?

A

How efficient ventilation is i.e. how hard you breathe to move the same amount of CO2
- if VE is close to predicted max (>80%) then is what has caused you stop exercising as you have reached your resp limit

58
Q

What stages should you go through to interpret CPET?

A

1) Is it maximal test
- VO2 plateau reached
- RER >1.1
- HR reserve low (i.e. close to maximal HR)
- Lactate >4
- Anaerobic threshold passed (point at which CO2 rises faster than VO2)
- Exhaustion

If yes,
2) Is the capacity normal? Peak VO2 >80% or 20ml/kg (considered normal) –> ie. if see VO2 >80% then can basically say is normal test

If no,
3) Did they reach resp limit?
- VE >80% of predicted max = FEV1x40
- ‘Low breathing reserve’
Or did they reach cardio limit?
- HR>80% predicted max = 220-age
- ‘Low heart reserve’ –> nb. this is what would expect in normal tests

4) If yes, did SATS fall by >4%? or rapid rise in HRR? or abnormal BP response?
- Y probably cardiac disease
- N probably deconditioning

59
Q

CPET test - what is O2 pulse?

A

oxygen consumption (VO2) / HR

  • normal is 10ml/min
  • proxy of cardiac output
60
Q

What are contraindications to diving in respiratory disease?

A
  • bullae or cysts
  • spontaenous PNX unless treated with bilateral surgical pleurectomy and normal CT after surgery (nb traumatic okay as long as CT and lung function normal)
  • Airways disease and FEV1 <80%
  • Active sarcoid (quiescent needs normal CT and lung function)
  • CF
  • ILD
61
Q

What causes a biphasic flow volume loops (tails at the end of the exp and insp phase)?

A

Unilateral bronchial stenosis
- bronchial cancer or mets
- unilateral emphysema
- single lung tx
- granulation tissue at anastomosis post-tx
- GPA
- Sarcoid, amyloid
- Bronchogenic cyst

62
Q

What is the best test for assessing lung volumes prior to lung volume reduction surgery in bullous disease?

A

Body plethysmography

63
Q

how much would you expect vital capacity to fall when pt lying down?

A

10%

10-20% suggestive of diaphragm paralysis
>20% usually bilateral diaphragm paralysis

64
Q

What can cause a flow-volume loop that has ‘vibrations’?

A

OSA

65
Q

How is airways resistance proportional to the radius of the bronchi?

A

Inversely proportional to radius^4 (Poiseuilles Law)

e.g. if radius becomes twice as large, resistance decreases by 2^4 = 16

66
Q

What is the limit for the transverse diameter of the trachea beyond which it is considered tracheomegaly?

A

3cm

Normal: 1.5-2.5cm men, 1.0-2.1cm women

67
Q

What shifts the oxygen dissociation curve to the right? i.e. lower affinity of Hb for oxygen = more available for tissues

A

Low pH
Increase 2-3 DBP (organic phosphate)
Increase temp

68
Q

What shifts the oxygen dissociation curve to the left? i.e. higher affinity of Hb for oxygen = less available for tissues

A

Increase pH
Decrease 2-3 DPG
Decrease temp

revision (17 decks)

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