Respiratory failure

Question 1

What is respiratory failure

Answer 1

when the lungs fail to adequately oxygenate arterial blood, and/or fail to prevent CO2 retention

Question 2

What is seen in bloods with type 1?

Answer 2

type 1 known as oxygenation failure

Low PaO2 (hypoxaemia), Low or normal PaCO2

Question 3

Type 1 respiratory failure is associated with?

Answer 3

Damage to lung tissue which prevents adequate oxygenation of the blood. However, the remaining normal lung is still sufficient to excrete carbon dioxide.

• gas exchange problem

Question 4

Commonest mechanism to cause type 1 respiratory failure?

Answer 4

V/Q mismatch

possible to recognise a VQ mismatch or shunt because the arterial blood gases will not fit the alverolar gas equation (PaO2 is reduced, PaCO2 is normal) - type 1

Question 5

Some common causes of type 1 respiratory failure?

Answer 5

• Pneumonia
• Pulmonary oedema
• Pulmonary embolism
• Asthma
• Emphysema
• Pulmonary fibrosis
• Acute respiratory distress syndrome

Question 6

Treatment for type 1 respiratory failure

Answer 6

improve oxygenation: nasal cannula, hudson mask, venturi mask, non-rebreathe mask, high flow nasal cannulae

recruit alveoli

Question 7

In type 2, what is seen in bloods?

Answer 7

Low PaO2 (hypoxaemia), high PaCO2 (hypercapnea)

Question 8

Commonest mechanism to cause type 2 respiratory failure?

Answer 8

Alveolar hypoventilation

Question 9

Some common causes of type 2 respiratory failure

Answer 9

Lung problems (restrictive eg FLD, obstructive eg COPD)

Respiratory generator problems (drugs, hypothyroidism, CVA)

Chest wall/neuromsc junction (obesity, kyphoscoliosis, myasthenia gravis)

Question 10

Problems with just oxygenating more?

Answer 10

will not ventilate the patient more, only oxygenate the patient better

Question 11

Treatment of type 2 respiratory failure?

Answer 11

Positive pressure ventilation
- Bilevel positive airway pressure (BIPAP)
– Inspiratory positive airway pressure (IPAP)
– Positive end expiratory pressure (PEEP/EPAP)
- Set backup respiratory rate
- Can be volume controlled
- CPAP = continuous positive airway pressure,
not ventilation, can splint upper airway (in
obstructive sleep apnoea), aids oxygenation

Treating the underlying cause

Question 12

Difference between invasive and non-invasive PPV

Answer 12

Positive pressure ventilation can be delivered in two forms: non-invasive positive pressure ventilation (NIPPV), which is delivered through a special face mask with a tight seal (air travels through anatomical airways), or invasive positive pressure ventilation (IPPV), which involves the delivery of positive pressure to the lungs through an endotracheal tube or tracheostomy (or any other device that delivers gas bypassing parts of the anatomical airway).

Question 13

Non-invasive postive pressure ventilation

Answer 13

• NPPV is used to treat both acute and chronic respiratory failure
• In the patient with chronic respiratory failure, NPPV can be used to provide 24-hour ventilatory support
• Acute exacerbation of COPD most evidence/successful

Question 14

Why might giving uncontrolled O2 therapy to someone in type 2 failure may indeed worsen their condition?

Answer 14

chronic pulmonary disease usually causes the patient to be reliant on hypoxic drive (as opposed to hypercapnic drive) for breathing; therefore, giving them O2 could obliterate this hypoxic drive and cause them to go into respiratory arrest.

Question 15

What is V/Q mismatch mechanism?

Answer 15

Ventilation/perfusion ratio is off

Lead to compensatory vasoconstriction

Extremes:
Ventilation, no perfusion =dead space

Perfusion, no ventilation =shunt

Question 16

Common causes of V/Q mismatch?

Answer 16

• Alveolar filling e.g. pneumonia, pulmonary oedema
  
  • Poor ventilation COPD
  • Pneumothorax
  • Pulmonary embolus

Question 17

What is shunt? causes of shunt?

Answer 17

• the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries.
• may not respond to supplemental oxygenation
• if extreme will affect CO2

Causes:
Extensive atelectasis/Severe pneumonia/ARDS

Can be anatomic e.g. Intracardiac defects (Eisenmengers) and intrapulmonary (AV malformations)

Question 18

What is impaired diffusion?

Answer 18

Impaired if distance between alveoli and capillary increased, e.g. in fibrotic lung disease

Question 19

What is Hypoventilation?

Answer 19

occurs when ventilation is inadequate to perform respiratory gas exchange

• breathing too little
• causes increased CO2 (hypercapnea) and respiratory acidosis

Question 20

Arterial hypoxaemia an important cause of
tissue hypoxia but not the only cause as
also influenced by:

Answer 20

Tissue blood flow
Cardiac output
Haemaglobin O2 affinity
Oxygen carrying capacity of blood

Question 21

Low pH occurs in?

Answer 21

primary respiratory acidosis

Question 22

If arterial PCO2 is decreased what does it mean?

Answer 22

Hyperventilation

If PaO2 fits the alveolar PO2 → hyperventilation problem only (e.g. panic attack)

If PaO2 less than calculated alveolar PO2 → hyperventilation problem + gas exchange problem)

Question 23

If arterial PCO2 is decreased what does it mean?

Answer 23

Hyperventilation

If PaO2 fits the alveolar PO2 → hyperventilation problem only (e.g. panic attack)

If PaO2 less than calculated alveolar PO2 → hyperventilation problem + gas exchange problem)

Question 24

If arterial PCO2 is elevated what does it mean?

Answer 24

hypoventilation

If the PaO2 fits the alveolar gas equation → hypoventilation only (e.g. respiratory depressant drug e.g. morphine)

If PaCO2 elevated and PaO2 less than calculated alveolar PO2 → hypoventilation problem and gas exchange problem e.g. COPD

Question 25

Why do we use PaO2’s reference range of >10.6kPa?

Answer 25

the point where 98% saturation of Hb is achieved on the HbO2 dissociation curve

Question 26

what is PaO2 ?

Answer 26

partial pressure of O2, measurement of oxygen pressure in arterial blood. Reflects how effective oxygen is able to move from the lungs into the blood.