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Respiratory medicine > L14 - Respiratory Failure > Flashcards

L14 - Respiratory Failure Flashcards

1
Q

OHS —> Obesity Hypoventillation syndrome (3)

A

Obesity hypoventillation syndrome

  • combination of obesity
  • high BMI
  • awake chronic hypercapnia
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2
Q

Effect of obesity on breathing

A

Increases work of breathing

  • because of reduction in chest wall compliance
  • reduction of respiratory muscle strength.
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3
Q

Define respiratory failure

A

When resp system fails in one or both of its gas exhange functions:
- oxygenation and CO2 elimination

Hypoxemia
Hypercapnia

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4
Q

Type 1 respiratory failure

A 
Low PaO2 ( <60mmHg)
Normal PaCO2

Occurs with diseases damaging lung tissue

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5
Q

Type 2 respiratory failure

A

Low PaO2

Alveolar ventillation insufficient to remove CO2 vol produced by tissue metabolism.

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6
Q

Ventilatory capacity

A

Maximal spontaneous ventilation that can be maintained without development of respiratory muscle fatigue.

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7
Q

Ventilatory demand

A

Spontaneous minute ventilation that results in a stable PaCO2

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8
Q

Optimally ventilated alveoli that are not perfused well have:

A

Large ventilation to perfusion ratio.

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9
Q

Alveoli that are optimally perfused but not adequately ventilated have:

A

Low ventillation / perfusion ratio.

Low V/Q unit

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10
Q

What two main factors account for hypoxemia

A

V/Q mismatch

Shunt

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11
Q

Effect of low V/Q units

A

Contribute to hypoxemia and hypercapnia.

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12
Q

High V/Q units

A

Waste ventillatoin.

Do not affect gas exchange unless the abnormality is quite severe.

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13
Q

Shunt

A

Persistence of hypoxemia despite 100% oxygen inhalation

  • deoxy blood bypassed ventilated alveoli
  • mixes with oxy blood that has flowed through ventilated alveoli
  • leads to reduction in arterial blood content
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14
Q

Criteria for daignosis of Adult respiratory distress syndrome ARDS

A
  • crackles upon auscultation
  • tachypnea, dyspnea
  • aspiration
  • sepsis
  • diminished compliance
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15
Q

Compare respiratory and metabolic compensation

A

Respiratory compensation;

  • quickly
  • increase or decrease in alveolar ventilation

Metabolic compensation:

  • takes few days to occur
  • requires kidneys to either reduce bicarb production or increase bicarb production
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16
Q

Describe respiratory acidosis

A

Inadequate alveolar ventilation.
Leads to CO2 retenion.

ABG:

  • low pH
  • high CO2
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17
Q

Causes of respiratory acidosis (3)

A
  1. Guillain-Barre syndrome
    - leads to inability to adequately ventilate
  2. Asthma
  3. COPD
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18
Q

Describe respiratory alkalosis

A

Excessive alveolar ventilation.

PaCO2 reduced and pH increases causing alkalosis.

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19
Q

Describe metabolic acidosis

A
  • Increase H+ acid over production

- decrease H+ acid excretion

20
Q

Describe metabolic alkalosis

A
  • Decrease H+ leading to increased bicarb.
  • GI loss of H+, via vomitting

Renal loss of h+

21
Q

Describe mixed resp and metabolic acidosis on ABG

A

ABG - decreased pH, increased CO2, decreased bicarb

causes?
- cardiac arrest, multiorgan failure

22
Q

Describe some potential causes of Type I respiratory failure

A
  • pneumonia
  • acute lung injury
  • cardiogenic pulmonary oedema
  • lung fibrosis
23
Q

Describe some potential causes of Type II respiratory failure

A
  • COPD
  • Chest wall deformities - resp muscle weakness (GBS)
  • depression of resp centre in drug overdose
24
Q

Describe mixed resp and metabolic alkalosis

A

ABG: High pH, low CO2, high bicarb

Causes: liver cirrhosis with diuretic use, hyperemesis gavidarum, excessive ventilation in COPD

25
Q

When is vital capacity a useful diagnostic tool?

A
  • usefull in patients with resp inadequacy due to neuromuscular problems
  • GB, myasthenia gravis

Vital capacity will decrease as disease worsens

26
Q

Describe some methods of oxygen administration

A
  • Nasal canullae
  • Intermittent positive pressure ventilation
  • Ventilator
27
Q

Nasal canullae

A
  • less claustrophobic
  • does not interfere with speaking or feeding
  • can cause ulcercation of nasal and pharyngeal mucosa
28
Q

Intermittent positive pressure ventillation

A

Mechanical ventilor intermittently inflates lung with positive pressure

29
Q

Dangers of controlled mechanical ventillation CMV

A

CMV with abolition of spontaneous breathing rapidly leads to atrophy of resp muscles.

30
Q

What is a measure of bacterial infections that might occur as a result of using a ventilator

A

Measurement of procalcitonin as a marker of severe bacterial infections.

31
Q

Describe the two types of CMV

A
  1. Volume controlled ventilation.
    - tidal vol and resp rate preset, airway pressure varies
  2. Pressure controlled ventilation
    - insp pressure and resp rate preset but tidal volume varies.
    - depends on patients lung mechanics
32
Q

Describe use of CPAP

A

Continous positive airway pressure.
- oxygen and air delivered under pressure via an endoctracheal tube.

Improves lung compliance, work of breathing reduced

33
Q

Guillain Barre syndrome

A

Acute multifocal disease demyelinating peripheral nerves.

Muscle weakness tends to occur at lower extremities then progresses upwards.

Nerve conduction studies almost always show evidence of demyelination and CSF protein usually high.

34
Q

Asthma

A

Asthma

  • airway hyperresponsiveness
  • reversible constriction of airways due to smooth muscle spasm and mucosal inflammation
35
Q

Asthma may lead to which type of repsiratory failure

A

Type 1
- compensation by hypoventilating unobstructed areas of lung, resulting in low paCO2.

Type 1 –> acidosis –> Type 2

  • capacity for hyperventillation impaired by high FRC.
  • more airway narrowing
  • hypoxemia worsens
  • pCO2 rises
  • hypercapnia
  • type 2
36
Q

COPD

A

Small airway collapse due to destruction of elastic pulmonary tissue.

  • high FRC, hyperinflation chest
  • effort required to ventilate alveoli against increasing resistance gives rise to dyspnoea or exertion.
37
Q

Destruction of alveolar wall may lead to formation of what:

A

Formation of larger air sacs (emphysema)

Inefficient for gas exchange.

38
Q

Emphysema

A

Enlargement of alveolar sacs by destruction of alveoli wall.
Bullae (large spaces) form.
Reduce SA

39
Q

How might emphysema lead to pnuemothorax?

A
  • Bullae situated close to visceral pleura can rupture.

- Resulting in pneumothorax

40
Q

Causes of enlargement of lung

A

Destruction of elastin fibres in lung tissue by activity of neutrophil elastaste.

41
Q

Link between a1-anti-trypsin and neutrophil elastate

A

AAT inhibits neutrophil elastase.

Cigarrete smoke stimulates neutrophil influx with the release of excess elastase.

42
Q

State some causes of hypoxemia

A

Shunt

  • lung perfused but not ventilated
  • v/q mismatch
  • diffusion block due to thickened interstitium between alveoli and capillary
43
Q

Hypercapnia causes

A

Failure to ventilate.
CNS
Neuromuscular chest wall defects.

44
Q

How does CPAP work

A

Tight fitting mask and flow generator to deliver positive pressure.

Increases functional residual capacity.

45
Q

Describe invasive mechanical ventilation

A

Delivered through an endotracheal tube or tracheostomy.

46
Q

State some causes of Type 2 respiratory failure

A
  • muscle conditions
  • acute Guillain Barre syndrome
  • Botulism acute
  • muscular dystrophy
  • motor neurone disease chronic
47
Q

Disadvantages of positive pressure ventilation (4)

A
  1. over distention of alveoli causing them to rupture —> leading to barotrauma and pneumothroax.
  2. shearing alveoli leads to cytokine release.
  3. positive pressure squeezes BV draining blood to heart, reduces blood returning to heart, leading to hypotension, reduction in cardiac output
  4. ventilator associated pneumonia

Respiratory medicine (16 decks)

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