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Medicine: Respiratory > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

1
Q

What is respiratory failure?

A

PaO2 <8kPa and subdivided into two types according to the PaCO2.

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2
Q

What are the steps of normal ventilation?

A
  1. Diaphragm (and external intercostals) contract - in laboured breathing, the accessory muscles contract.
  2. Increases the volume and increases the negative intrapleural pressure - overcomes elastic recoil of lungs, pleural cavity filled with fluid which cannot expand.
  3. Lungs expand
  4. Diaphragm relaxes - quiet breathing = lung elastic recoil, increased ventilation = aided by internal intercostal and accessory muscles.
  5. Decreases the negative pressure and forces air out.
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3
Q

Which areas of the brain control ventilation and what specifically do they each control?

A
  1. Medulla - controls basic rhythm of respiration, respiratory pattern generator
  2. Apneustic centre - increases inspiration and prevents expiration
  3. Pneumotaxic centre - coordinates transition between inspiration and expiration (inhibits apneustic centre)
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4
Q

Where do the centres in the brain controlling respiration receive input from?

A
  1. Peripheral chemoreceptors - in the aortic arch (CN IX) and carotid body (CN X), they are stimulated by low oxygen and high CO2 and acidaemia.
  2. Central chemoreceptors - ventral medulla, stimulated by CO2 only in the CSF so cannot detect metabolic causes of acid-base imbalance, only respiratory.
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5
Q

What is a VQ mismatch?

A

Reduction in either perfusion (obstruction to blood supply) or ventilation (airway obstruction).

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6
Q

What is the extreme form of VQ mismatch where there is no blood perfusion?

A

Shunt

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7
Q

What are the early signs of respiratory failure?

A

Tachypnoea (more pronounced in type 1), agitation and decreased levels of consciousness.

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8
Q

What are the long term effects of hypoxia?

A
  1. Polycythaemia - decreased renal oxygenation, increased EPO.
  2. Cor pulmonale - hypoxic vasoconstriction of pulmonary vessels = pulmonary HTN, right heart hypertrophy, right sided heart failure.
  3. Fluid retention - decreased renal perfusion, RAAS upregulation.
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9
Q

What are the signs and symptoms of hypoxia?

A

Dyspnoea, restlessness, agitation, confusion, central cyanosis, polycythaemia (chronic), cor pulmonale (chronic).

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10
Q

What are the signs and symptoms of hypercapnia?

A

Headache, confusion, drowsiness, coma, peripheral vasodilation, bounding pulse, tremor/flap, papilloedema.

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11
Q

What are the long term effects of hypercapnia?

A
  1. Respiratory acidosis - compensated in chronic patients

2. Hypercapnic respiratory drive desensitised - partial switch to hypoxic drive.

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12
Q

What is type 1 respiratory failure?

A

A failure of oxygenation - hypoxia with a normal or low PaCO2.

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13
Q

What are the causes of type 1 respiratory failure and do they affect ventilation (V) or perfusion (Q)?

A
  1. Pneumonia (V)
  2. Pulmonary oedema (V)
  3. Pulmonary embolism (Q)
  4. Asthma (V)
  5. Emphysema (V)
  6. Pulmonary fibrosis (V)
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14
Q

What is the management for type 1 respiratory failure?

A
  1. Treat underlying cause
  2. O2 24-60% by facemask
  3. Assisted ventilation if PaO2 <8kPa despite 60% O2
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15
Q

What is type 2 respiratory failure?

A

A failure of pump - hypoxia with hypercapnia (alveolar hypoventilation)

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16
Q

What are the causes of type 2 respiratory failure?

A
  1. Pulmonary disease - asthma, COPD, pneumonia, end stage pulmonary fibrosis, OSA
  2. Reduced respiratory drive - sedative drugs, CNS tumour/trauma
  3. Neuromuscular disease - cervical cord lesion, diaphragmatic paralysis, myasthenia gravis, Guillain-Barre syndrome
  4. Thoracic wall disease - kyphoscoliosis
17
Q

What is the management for type 2 respiratory failure?

A
  1. Treat underlying cause
  2. Controlled O2 therapy - start at 24%
  3. Recheck ABG after 20 mins, if PaCO2 steady then increased O2, if >1.5kPa then consider NIPPV (BiPAP)
  4. If NIPPV fails, intubation and ventilation
18
Q

What is the key indication of non-invasive positive pressure ventilation?

A

COPD pH 7.25-7.35

19
Q

What is non-invasive positive pressure ventilation and what are the two types?

A

Delivery of oxygen via tightly fitted mask:

  1. CPAP (continuous)
  2. BiPAP (bi-level positive airway pressure)
20
Q

What ventilation is favoured in type 2 respiratory failure and why?

A
  1. BiPAP (CPAP for type 1)

2. Creates low pressure resistance for expiration

Medicine: Respiratory (29 decks)

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