7: Resp Failure and Support

Question 1

What is normal tidal volume?

Answer 1

10-20ml/kg

Question 2

What should mmHg PaO2 be?

Answer 2

80-100

Question 3

What should mmHg PaCO2?

Answer 3

35-45

Question 4

What happens to the O2 dissociation curve in sick animals?

Answer 4

Moves right so small O2 changes cause large saturation change

Question 5

What is type 1 resp failure?

Answer 5

Hypoxic - either from decreased oxygen percentage like altitude or anaesthetic machine failure, OR from pulmonary disease like a shunt, V:Q mismatch or perfusion impairment

Question 6

What is type 2 resp failure?

Answer 6

Hypoventilation/hypercapnia - from metabolic rate increase or failure to remove CO2 like low resp rate, low tidal volume or too much dead space

Question 7

What happens in hypoxic pulmonary vasoconstriction?

Answer 7

Blood redirected to well-ventilated areas of lungs

Question 8

What reduces the effect of hypoxic pulmonary vasoconstriction?

Answer 8

Inhalational anaesthetic, systemic vasodilator, lung trauma or injury e.g. sepsis

Question 9

How do intrapulmonary shunts respond to oxygen therapy?

Answer 9

Don’t

Question 10

What determines saturation in intrapulmonary shunts?

Answer 10

The shunt fraction

Question 11

How long does cyanosis take to occur?

Answer 11

A long time

Question 12

What does cyanosis depend on?

Answer 12

The amount of Hb

Question 13

Which sample is definitive for hypoxaemia?

Answer 13

Arterial blood gas

Question 14

What clinical signs do you see in low O2?

Answer 14

Orthopnoeic stance and tachypnoea

Question 15

How do you treat hypoxaemia?

Answer 15

De-stress, increase oxygen until sats at 90%, treat cause

Question 16

What are clinical signs or type 2 resp failure?

Answer 16

Mouth breathing, abducted elbows, no cyanosis, tachycardia as high CO2 is sympathomimetic, bounding pulses, hypertension

Question 17

How do you treat type 2 resp failure?

Answer 17

Remove cause, ventilate if cannot relieve failure, or tracheostomy

Question 18

What is type 3 resp failure?

Answer 18

Subtype of 1 with components of 2 - it is atelectasis from increased abdominal pressure or inadequate analgesia for thoracic surgery

Question 19

What kind of oxygen sats does type 3 resp failure cause?

Answer 19

Low when breathing room air

Question 20

What are some examples of type I resp failure?

Answer 20

Pneumonia, pulmonary fibrosis, asthma

Question 21

What are some examples of type II resp failure?

Answer 21

Obstruction, decreased resp muscle, anaesthesia, NM disease

Question 22

What is an example of type III resp failure?

Answer 22

Atelectasis

Question 23

How do you treat type III resp failure?

Answer 23

Preventatively - if prolonged op, obese, high intra-abdominal pressure - must ventilate, keep head up, consider bronchodilator

Question 24

What is the “recruitment manoever”?

Answer 24

To treat type III resp failure - give a high pressure inspiration to cut off venous circulation for 30-45s so alveoli can re-expand

Question 25

After how long does 100% oxygen cause toxicity, inflammation and eventual fibrosis?

Answer 25

3-4 hours

Question 26

Above what % O2 do you need a delivery system?

Answer 26

Over 50%

Question 27

After how long do you see epithelial changes if you don’t use a humidifer?

Answer 27

2-3 hours (atelectasis and tracheitis)

Question 28

What are some problems with heat-moisture exchange (HME) devices?

Answer 28

Increase deadspace, increase resistance, can disconnect, only useful if intubated

Question 29

What’s the problem with using a humidifier?

Answer 29

Potential source of infection

Question 30

How often should you nebulise?

Answer 30

0.9% NaCl for 30-45 mins 2-4 times a day

Question 31

What does coupage do?

Answer 31

percussing chest wall loosen secretions and stimulates coughing

Question 32

What is type 4 resp failure?

Answer 32

Cardiovascular impairment to oxygen delivery like a thrombus or cardiac disease, or reduced carrying capacity like anaemia