respiratory failure

Question 1

Define respiratory failure

Answer 1

Syndrome of inadequate gas exchange due to dysfunction of one or more components of the respiratory system

Question 2

What are the three components of the respiratory system?

Answer 2

Nervous system, respiratory muscle, pulmonary

Question 3

How does the nervous system contribute to the respiratory system?

Answer 3

CNS/ brainstem (ventro-lateral medulla) contains respiratory centres.
PNS and neuromuscular junction

Question 4

What happens in terms of ventilation when the pressure in the pleura is more negative?

Answer 4

There is a greater transmural pressure gradient therefore the alveoli become larger and less compliant resulting in less ventilation

Question 5

What happens in terms of ventilation when the pressure in the pleura is less negative?

Answer 5

Smaller transmural pressure gradient therefore the alveoli become smaller and more compliant so more ventilation

Question 6

What happens in terms of lung perfusion when there is a lower intravascular pressure?

Answer 6

Less recruitment, greater resistance, lower flow rate

Question 7

What happens in terms of lung perfusion when there is a higher intravascular pressure?

Answer 7

More recruitment, less resistance and higher flow rate

Question 8

What are the three classifications of respiratory failure?

Answer 8

Acute, chronic, acute on chronic

Question 9

What are some examples of acute respiratory failure?

Answer 9

Pulmonary: infection, aspiration, primary graft dysfunction. Extra-pulmonary: trauma, pancreatitis, sepsis. Neuromuscular: myasthenia/GBS

Question 10

What are some examples of chronic respiratory failure?

Answer 10

Pulmonary: COPD, lung fibrosis, CF, lobectomy. Muscoskeletal: muscular dystrophy

Question 11

What are some examples of acute on chronic respiratory failure?

Answer 11

Infective exacerbation of COPD or CF, myasthenic crises, post operative

Question 12

What is the biggest risk factor in males for respiratory failure and what is the biggest risk factors in females?

Answer 12

Males = smoking. Females = household air pollution

Question 13

What are the four different physiological classifications of respiratory failure?

Answer 13

Type 1 (hypoxemic). Type 2 (hypercapnic). Type 3. Type 4

Question 14

What is meant by the term hypoxemic?

Answer 14

below-normal level of oxygen in your blood, specifically in the arteries

Question 15

What is meant by the term hypercapnic

Answer 15

an elevation in the arterial carbon dioxide tension

Question 16

What is type 1 respiratory failure?

Answer 16

Failure of oxygen exchange, pO2<60. Leads to increased shunt fraction due to alveolar flooding. Hypoxemia despite adequate levels of inspiration. Causes collapse, pulmonary oedema, fibrosis or embolism and hypertension

Question 17

What is type 2 respiratory failure?

Answer 17

Failure to exchange or remove CO2, pCO2>45. Decreased alveolar minute ventilation, dead space ventilation. Seen in NM disease or COPD, obstructive airway disease

Question 18

What is type 3 respiratory failure?

Answer 18

Perioperative respiratory failure. Increased atelactasis due to low functional residual capacity with abnormal abdominal wall mechanics. Results in hypoxemia or hypercapnia, can be prevented with good postural positioning

Question 19

What is type 4 respiratory failure?

Answer 19

Shock. Poor perfusion of the lung, intubated and ventilated during shock. Ventilator effects on LV reducing afterload but has negative effect on RV as increases preload

Question 20

Define minute ventilation?

Answer 20

Gas entering and leaving the lungs per minute

Question 21

Define alveolar ventilation

Answer 21

Gas entering and leaving the alveoli per minute

Question 22

How do we calculate minute ventilation?

Answer 22

Tidal volume (L) x breathing frequency

Question 23

How do we calculate alveolar ventilation?

Answer 23

(Tidal volume (L) - dead space (L)) x breathing frequency

Question 24

What are the risk factors associated with chronic respiratory failure?

Answer 24

COPD
Pollution
Recurrent pneumonia
CF
Pulmonary fibrosis
Neuro-muscular diseases

Question 25

What are the risk factors associated with acute respiratory failure?

Answer 25

Infection – viral, bacterial Aspiration Trauma Pancreatitis Transfusion

Question 26

What is commonly seen alongside acute respiratory failure?

Answer 26

Lower respiratory tract infections, aspiration of gastric contents, trauma, pulmonary vascular disease, pancreatitis

Question 27

Why is aspiration of gastric contents often seen alongside acute respiratory failure?

Answer 27

Acid results in response in the lungs

Question 28

Outline how vascular supply injury can lead to acute lung injury

Answer 28

Leads to damage of lung interstitium which is necessary for structural support

Question 29

Outline how activation of alveolar macrophages leads to acute lung injury

Answer 29

When alveolar macrophages are activated by infection or inflammation release further cytokines. IL-6 and TNF-alpha, (also TNFR1) well established in response to ARDs In response to inflammatory setup, get alveolar fluid build-up/protein-rich oedema forming within lung. Degradation of surfactant so lung less efficient at expanding Migration of leukocytes out of blood vessels into interstitium where they can cause damage before getting to site of interest, due to chemokines Secrete proteases + other inflammatory mediators causing damage and fluid build up. Larger gap between alveoli and capillary so gas exchange less effective

Question 30

What are the pulmonary causes of ARDS?

Answer 30

Aspiration, trauma, burns, surgery, drug toxicity, infection

Question 31

What are the extra-pulmonary causes of ARDS?

Answer 31

Trauma, pancreatitis, burns, transfusion, surgery, BM transplant, drug toxicity, infection

Question 32

What pharmacological therapies have been tried to treat ARDS?

Answer 32

Steroids like dexamethasone, salbutamol, surfactant, N-acetylcysteine, neutrophil esterase inhibitor, GM-CSF, statins

Question 33

What pharmacological treatments are currently being trialled for ARDS?

Answer 33

Mysenchymal stem cells, keratinocyte growth factor, mircovesicles, extra corporeal removal of CO2 using ECMO light circuit

Question 34

What are the underlying distinct biological processes in ARDS?

Answer 34

Pulmonary vascular, endothelial inflammatory response Thrombosis -> micro emboli – vast areas of lung with poor perfusion Angiogenesis -> radiological evidence of new blood vessel formation

Question 35

What therapeutic interventions are offered to treat underlying disease of ARDS?

Answer 35

Inhaled therapies -> bronchodilators, pulmonary vasodilators (esp. if proven RH failure) Steroids Antibiotics Anti-virals Drugs -> pyridostigmine, plasma exchange, IViG, rituximab

Question 36

What therapeutic intervention is offered to give respiratory support to those with ARDS?

Answer 36

Physiotherapy Oxygen (COPD + type 2 chronic resp. failure need diff. oxygen management to normal) Nebulisers  salbutamol, ipratropium bromide, saline, NAC to reduce mucus. High flow oxygen – nasal cannula, face masks Non invasive ventilation – stent to open alveoli Mechanical ventilation Extra-corporeal support – membrane lung

Question 37

What therapeutic intervention is given for multiple organ support to those with ARDS?

Answer 37

Cardiovascular support  fluids, vasopressors, inotropes, pulmonary vasodilators Renal support  haemofiltration, haemodialysis Immune therapies  plasma exchange, convalescent plasma

Question 38

What are the sequelae of ARDS?

Answer 38

Poor gas exchange, infection, inflammation, systemic effects