20 - Respiratory Failure

Question 1

Concentration of oxygen in air

Answer 1

20.94%

Question 2

Barometric pressure (atmospheric pressure)

Answer 2

101.3kpa

Question 3

PO2 of dry air at sea level

Answer 3

21.2kpa

o2 in air x atmospheric pressure

Question 4

What is tracheal gas

Answer 4

PO2 after humidification

Question 5

How to work out tracheal gas

Answer 5

•	Fractional concentration of oxygen in the dry gas phase x (barometric pressure - SVP)
FiO2 x (PB - SVP)

Question 6

What effects alveolar PO2

Answer 6

Ventilation

O2 consumption/CO2 production

Question 7

Alveolar PaO2

Answer 7

dry barometric pressure x (FiO2-VO2 / VA)

Question 8

What is FiO2, VO2 and Va

Answer 8

o FiO2 – inspired oxygen concentration- 21/20.93
o VO2- oxygen consumption(round 250 ml/min)
o VA- alveolar ventilation

Question 9

What is the alveolar to arterial PO2 difference determined by

Answer 9

Shunting

Question 10

What is the normal A-A O2 difference

Answer 10

not normally greater than 2 kPa

Question 11

What is shunting

Answer 11

An area of the lung that is perfused but not ventilated

Has blood supply but not oxygen

Question 12

What is oxygen delviery

Answer 12

= [Hb] x Oxygen Saturation of Hb x 1.34 x 10 x Cardiac Output
o Round 1 litre per minute

Question 13

Signs of respiratory compensation

Answer 13

Tachypnoea > 20
Use of accessory muscles
Nasal flaring

Question 14

Signs of increased sympathetic tone

Answer 14

Tachycardia
Hypertension
Sweating

Question 15

Signs of end-organ hypoxia

Answer 15

Altered mental status

Bradycardia and hypotension

Question 16

Signs of haemoglobin desaturation

Answer 16

Cyanosis

Question 17

Signs of CO2 retention

Answer 17

Flap

Bounding pulse

Question 18

Type I respiratory failure

Answer 18

Hypoxaemia only- caused by shunting (hypoxia)

PaO2 < 8kpa

Question 19

Causes of Type I resp failure

Answer 19

Pneumonia
Pulmonary oedema
Asthma/COPD
PE
Pneumothorax

Question 20

Type II respiratory failure

Answer 20

o Hypoxaemia and hypercapnia
PaO2 <8kPa
PaCO2 > 6.5kPa

Question 21

Symptoms of type I resp failure

Answer 21

Type I with fatigue

Question 22

What can cause type 1 to turn into type 2

Answer 22

COPD

- After tired muscle

Question 23

What causes type 2 resp failure

Answer 23

Brainstem
Neuropathy 
Airway obstruction
Depressant drugs
Nerve root injury, or Chest wall compliance, nothing to do with lung

Question 24

Indications for oxygen therapy

Answer 24

• Respiratory failure, cardiac or respiratory arrest, tachypnoea, cyanosis, hypotension, metabolic acidosis

Question 25

Treatment for respiratory failure

Answer 25

Oxygen

Question 26

When do you use oxygen mask, nasal cannulae

Answer 26

Patient with normal vital signs (post op)

Question 27

When trauma mask

Answer 27

Higher o2 conc needed Asthma attack, pneumonia, sepsis (60% oxygen)

Question 28

When to use venturi mask

Answer 28

Controlled treatment in long term resp failure e,g COPD

Question 29

What does pulse oximetry tell us (SpO2)

Answer 29

oxygenation NOT ventilation

Question 30

What is the critical threshold for pulse oximetry saturation

Answer 30

94%

Question 31

Sources of error in pulse oximetry

Answer 31

 Poor peripheral perfusion  Dark skin (oximeter over-reads slightly)  False nails or nail varnish  Lipaemia / hyperlipidaemia / propofol infusion

Question 32

What is arterial blood gas monitoring for

Answer 32

• Arterial blood gas monitoring is used to keep the FiO2 to the minimum required to achieve adequate oxygenation Too high O2 --> free radicals which damage the body ABG also used to evaluate pH changes

Question 33

What percentage of COPD patients are CO2 retainers

Answer 33

10%

Question 34

What do do if unknown CO2 retainer

Answer 34

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

Question 35

What to do if known CO2 RETAINER

Answer 35

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

Question 36

When do you give ventilation

Answer 36

* Not for hypoxia * Ventilation Used for hypercapnea * i.e. give oxygen in hypoxia and ventilate in hypercapnea (= hypoventilation)