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Y3 Medicine: Respiratory > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

1
Q

What is respiratory failure?

A

Respiratory failure occurs when gas exchange is inadequate, resulting in hypoxia. It is defined as a PaO2 <8kPa and subdivided into two types according to PaCO2 level.

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2
Q

What is type I respiratory failure? What may cause it?

A

Defined as hypoxia (PaO2 <8kPa) with a normal or low PaCO2.

It is caused primarily by ventilation/perfusion (v/q) mismatch, hypoventilation, abnormal diffusion, right to left cardiac shunts.

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3
Q

Give examples of causes of type I respiratory failure

A
  • Pneumonia
  • Pulmonary oedema
  • PE
  • Asthma
  • Emphysema
  • Pulmonary fibrosis
  • ARDs
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4
Q

What is type II respiratory failure? What may cause it?

A

Defined as hypoxia (PaO2 <8kPa) with hypercapnia (PaCO2 >6.0kPa).

This is caused by alveolar hypoventilation, with or without v/q mismatch.

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5
Q

Give examples of causes of type II respiratory failure

A
  • Pulmonary disease
    • Asthma, copd, pneumonia, end-stage pulmonary fibrosis and obstructive sleep apnoea
  • Reduced respiratory drive
    • Sedative drugs, CNS tumour or trauma
  • Neuromuscular disease
    • Cervical cord lesion, diaphragmatic paralysis, poliomyelitis, myasthenia gravis and Guillain–Barré syndrome
  • Thoracic wall disease
    • Flail chest and kyphoscoliosis
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6
Q

What are the signs and symptoms of hypoxia?

A

Dyspnoea; restlessness; agitation; confusion; central cyanosis. If longstanding hypoxia: polycythaemia; pulmonary hypertension; cor pulmonale.

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7
Q

What are the signs and symptoms of hypercapnia?

A

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

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8
Q

What investigations should be ordered for respiratory failure?

A
  • Blood tests: FBC, U&E, CRP and ABG
  • CXR
  • Sputum and blood cultures (if febrile)
  • Spirometry
    • COPD, neuromuscular disease and Guillain–Barré syndrome
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9
Q

When should an ABG be considered?

A
  • Any unexpected deterioration in an ill patient
  • Anyone with an acute exacerbation of a chronic chest condition
  • Anyone with impaired consciousness or impaired respiratory effort
  • Signs of CO2 retention
  • Cyanosis, confusion, visual hallucinations (signs of ↓PaO2; SAO2 is an alternative)
  • To validate measurements from transcutaneous pulse oximetry
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10
Q

What are the signs of CO2 retention?

A

Bounding pulse, drowsy, tremor (flapping) and headache.

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11
Q

What are the reference ranges for the following parameters?

  1. pH
  2. PaCO2
  3. PaO2

Note: in kPa

A
  1. pH: 7.35 – 7.45
  2. PaCO2: 4.7 – 6.0 kPa
  3. PaO2: 11 – 13 kPa
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12
Q

Differentiate between acidotic and alkalotic blood

A

Acidotic: pH <7.35

Normal: pH 7.35 – 7.45

Alkalotic: pH >7.45

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13
Q

How does pH, pCO2 and HCO3- present in the following conditions?

  1. Respiratory acidosis
  2. Respiratory alkalosis
  3. Respiratory acidosis with metabolic compensation
  4. Respiratory alkalosis with metabolic compensation
A
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14
Q

How does pH, pCO2 and HCO3- present in the following conditions?

  1. Metabolic acidosis
  2. Metabolic alkalosis
  3. Metabolic acidosis with respiratory compensation
  4. Metabolic alkalosis with respiratory compensation
A
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15
Q

What does a high base excess indicate?

A

A high base excess (> +2mmol/L) indicates that there is a higher than normal amount of HCO3– in the blood, which may be due to a primary metabolic alkalosis or a compensated respiratory acidosis.

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16
Q

What does a low base excess indicate?

A

A low base excess (< -2mmol/L) indicates that there is a lower than normal amount of HCO3– in the blood, suggesting either a primary metabolic acidosis or a compensated respiratory alkalosis.

17
Q

Briefly describe both metabolic and respiratory compensation

A

Respiratory acidosis/alkalosis (changes in CO2) can be metabolically compensated by increasing or decreasing the levels of HCO3– in an attempt to move the pH closer to the normal range.

Metabolic acidosis/alkalosis (changes in HCO3-) can be compensated by the respiratory system retaining or blowing off CO2 in an attempt to move the pH closer to the normal range.

18
Q

How long does respiratory compensation take?

A

Respiratory compensation for a metabolic disorder can occur quickly by either increasing or decreasing alveolar ventilation to blow off more CO2 (↑ pH) or retain more CO2 (↓ pH).

19
Q

How long does metabolic compensation take?

A

Metabolic compensation for a respiratory disorder, however, takes at least a few days to occur as it requires the kidneys to either reduce HCO3– production (to decrease pH) or increase HCO3– production (to increase pH).

Y3 Medicine: Respiratory (15 decks)

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