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CR2 > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

To understand how oxygen passes from the atmosphere to the arterial level To understand what pathophysiological processes affect this oxygen cascade To identify symptoms and signs of respiratory failure To understand treatment options in respiratory failure

1
Q

What does oxygen delivery =?

A

Oxygen Delivery = [Hb] x Oxygen Saturation of Hb x 1.34 x 10 x Cardiac Output

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2
Q

What are some signs of respiratory failure?

A 
Respiratory compression
Increased sympathetic tone
end-organ hypoxia
haemoglobin desaturation
CO2 retention
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3
Q

What would be symptoms of CO2 retention?

A

flap

bounding pulse

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4
Q

What would be symptoms of end-organ hypoxia?

A

altered mental status

bradycardia and hypotension

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5
Q

What would be symptoms of Hb desaturation?

A

cyanosis

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6
Q

What would be symptoms of increased sympathetic tone?

A

tachycardia
hypertension
sweating

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7
Q

What would be symptoms of respiratory compensation?

A

tachypnoea
accessory muscle use
nasal flaring
intercostal or supersternal recession

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8
Q

When is type 1 respiratory failure defined as?

A

hypoxaemia only

PaO2<8kPa

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9
Q

What is type 2 respiratory failure defined as?

A

Hypoxaemia and hypercapnia
PaO2 < 8 kPa
PaCO2 >6.5 kPa

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10
Q

What are some examples of type 1 respiratory failure?

A

ANY DAMAGE TO LUNG TISSUE:

pneumonia, pneumothorax, pulmonary embolism, pulmonary contusion, asthma/COPD, collapse,pulmonary oedema, atelectasis

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11
Q

What are some examples of type 2 respiratory failure?

A

ANYTHING AFFECTING VENTILATION (cannot get rid of CO2)
Type 1 with fatigue
hypoventilation

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12
Q

What are some causes of hypoventilation?

A 
Brainstem
Metabolic encephalopathy
Depressant drugs
Spinal cord
Nerve root injury
Nerve trauma
Neuropathy
Neuromuscular junction
Respiratory muscles
Airway obstruction
Decreased lung or chest wall compliance
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13
Q

What are some indications for oxygen therapy?

A 
Respiratory failure
Cardiac or respiratory arrest
TACHYPNOEA
Cyanosis
Hypotension
Metabolic acidosis
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14
Q

What is first line treatment for hypoxia?

A

oxygen therapy

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15
Q

What are the different types of masks that can be used to deliver oxygen?

A

Oxygen masks with nasal cannulae
face mask with reservoir bag
venturi mask

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16
Q

When would you use the different types of masks?

A

oxygen masks with nasal cannulae - patient with normal vital signs (e.g. post op)
face mask with reservoir - higher O2 conc. needed (e.g. asthma attack/sepsis/pneumonia)
venturi mask - controlled treatment in LT (e.g COPD)

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17
Q

How is oxygen therapy carried out?

A

Provide high flow oxygen
continuous oximetry
monitor - vital signs & ABG

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18
Q

What is the limitation of pulse oximetry?

A

tells you only about oxygenation not ventilation

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19
Q

What is the threshold for pulse oximetry saturation?

A

94%, below this a small fall in PaO2 produces a sharp fall in SpO2.

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20
Q

What is the difference between PaO2 and SpO2?

A

PaO2 is the partial pressure of oxygen in the blood plasma whilst SpO2 is the saturation of haemoglobin with oxygen.

21
Q

What are some sources of error of pulse oximetry?

A 
Poor peripheral perfusion
Dark skin (oximeter over-reads slightly)
False nails or nail varnish
Lipaemia / hyperlipidaemia / propofol infusion
Bright ambient light
Poorly adherent probe
Excessive motion
Carboxyhaemoglobin (SpO2 > SaO2)
22
Q

What is the single most important sign of respiratory failure?

A

Tachypnoea

23
Q

What is ventilation used for?

A

Hypercapnea not hypoxia
Type 2 not Type 1
invasive and non-invasive

24
Q

What factors affect alveolar PO2?

A

ventilation

oxygen consumption/carbon dioxide production

25
Q

What is shunting of the lungs?

A

AN AREA OF THE LUNG THAT IS PERFUSED BUT NOT VENTILATED

26
Q

What is PaO2

A

Partial pressure of oxygen in the arterial blood

27
Q

What is PO2?

A

Partial pressure of oxygen in air

28
Q

What does PO2 =?

A

barometric pressure x concentration in air

29
Q

What is the PO2 for oxygen?

A

barometric pressure (101.3kPa) x conc in air (21%) = 21.2kPa

30
Q

What is tracheal gas?

A

PO2 after humidification

31
Q

How do you calculate tracheal gas?

A

Fractional concentration of oxygen in the dry gas phase x (barometric pressure - SVP)

32
Q

What is SVP?

A

saturated vapour pressure - amount of gas saturated in water vapour which causes it to lose 6.3kPa

33
Q

What is the tracheal gas of oxygen?

A

0.21 x (101.3 – 6.3) = 19.9kPa

34
Q

What is PAO2?

A

Partial pressure of oxygen in the alveoli

35
Q

What does alveolar O2=

A

= dry barometric pressure x (FiO2-VO2 / VA)

36
Q

What is VA and VO2?

A

VA - alveolar ventilation

VO2 - oxygen ventilation

37
Q

What is the alveolar to arterial PO2 difference is determined by?

A

Shunting

38
Q

What is the alveolar to arterial PO2 difference?

A

not normally greater than 2 kPa

39
Q

What is the most common cause of hypoxia?

A

Shunting

40
Q

What is P50?

A

PO2 when haemoglobin is 50% saturated - normally 3.5Kpa

41
Q

When does cyanosis occur?

A

When PO2 is any less than 8kPa

42
Q

How much oxygen do we pump around in a minute?

A

1L

43
Q

How much oxygen do we consumer per minute?

A

250ml

44
Q

How can oxygen delivery be variable?

A

Breath to breath, respiratory rate, tidal volume.
Person to person
Size of mask, type of mask, vents in mask, fit of mask

45
Q

Why should arterial blood gas be monitored?

A

pH

PaCO2

46
Q

What are CO2 retainers?

A

10% of COPD patients

don’t rely on CO2 release, if give oxygen to them they will become hypoxic as CO2 still high

47
Q

What to do if you don’t know if the patient is a CO2 retainer or not?

A

Start high flow oxygen.
Monitor for drowsiness / signs of CO2 retention.
Check ABGs after 30 minutes

48
Q

What to do if you know a patient is a CO2 retainer?

A 
Controlled mask
Titrate - use lowest O2 possible
Aim for sats 90% - 92% (may need 85%+)
Measure ABGs ASAP
Repeat ABGs after 30 mins of O2 change

CR2 (35 decks)

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