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MD2 Ambulatory Care and Emergency Medicine > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

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Royal College: Emergency Medicine flashcards
1
Q

What is the most common input to the central and peripheral control system?

A

Hypoxia

  • Chemoreceptors in carotids - look at O2
  • Chemoreceptors in brainstem - detect acid-base
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2
Q

What happens when the chemoreceptors in the brainstem detect an increase in pH?

A

Decrease breathing to keep CO2

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3
Q

What happens when the chemoreceptors in the brainstem detect a decrease in pH?

A

Increase breathing to blow off CO2

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4
Q

What are other stimulants of respiratory drive?

A

Pain
Anxiety
Exercise
Hypoxaemia

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5
Q

What are the components of the respiratory pump?

A

Thoracic skeletal muscles

Diaphragm

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6
Q

What can cause the respiratory pump to fail?

A

Post-laparotomy, bowel tenses > pushes up against diaphragm > diaphragm can’t move
Phrenic nerve damage
Muscle relaxants paralyse diaphragm > don’t breathe

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7
Q

What is paradoxical breathing?

A

Chest moves inwards during inhalation > decreases O2 inhaled

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8
Q

What can affect the alveolar-capillary membrane, thus affecting respiration?

A 
Inflammation > pus
Emphysema
Aspirated material
Mucus
Blood; eg:
- Haematemesis
- Bleeding
Pulmonary oedema
Atelectasis
Septic shock > inflammatory peptides released > V-Q mismatch
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9
Q

What conditions can decrease respiratory drive?

A

Holding breath
Narcotic overdose
Sedatives

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10
Q

Against which forces does passive breathing occur?

A

Elastic and resistive forces

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11
Q

What are the roles of the upper airways?

A

Humidifies, filters, and warms incoming air
1st line of defence
Prevents aspiration

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12
Q

How can the upper airways contribute to respiratory failure?

A

Obstruction

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13
Q

How can the conductive airways contribute to respiratory failure?

A

Obstruction/narrowing

  • Bronchospasm
  • Secretions/sputum
  • Collapse
    • Lack of elastic support; eg: emphysema
    • Endoluminal; eg: carcinoma, sputum
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14
Q

What does surfactant do?

A

Reduces surface tension and prevents alveolar collapse > improves lung compliance

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15
Q

What are the normal values of arterial blood gases?

A 
pH = 7.4 (7.35-7.45)
PaCO2 = 40 (35-45) mmHg
PaO2 = 100 (>85) mmHg
HCO3 = 24 (22-30) mmol/L
SaO2 = 95-100%
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16
Q

What is the A-a gradient?

A

Difference between arterial (a) and alveolar (A) concentration of O2

17
Q

What does an elevated A-a gradient suggest?

A

Problem with diffusion

V-Q mismatch

18
Q

What is the A-a gradient on room air at sea level?

A

150 - 12.25 x PaCO2 - PaO2 = 7-14 in young adults - higher in elderly

19
Q

What is respiratory failure?

A

Impairment of gas exchange between ambient air and circulating blood
Occurs in
- Intrapulmonary gas exchange
- Movement of gases in and out of lungs

20
Q

What does impaired gas exchange usually result in?

A

Hypoxaemia > type 1 respiratory failure

PaO2 <60 mmHg

21
Q

What does hypoventilation (inadequate movement of gases in and out of lungs) primarily result in?

A

Hypercapnia > type 2 respiratory failure

PaCO2 >50 mmHg

22
Q

What can result in hypoxaemia?

A 
Reduced inspired O2
- Altitude
- Fires
V-Q mismatch
- Pneumonia
- PE
Impaired diffusion
- Pulmonary fibrosis
- COPD
Shunt
Hypoventilation
23
Q

What can result in hypercapnia?

A 
Central depression
- Narcotic overdose
- Sedation
- Injury
Completely blocked upper airway
Primary pump failure
- Neuromuscular disease
Muscle fatigue
- Usually due to increased WOB
Intrinsic lung disease
- Most common
Chest wall abnormalities
- Obesity
- Kyphosis
24
Q

What are the symptoms of respiratory failure?

A 
May be non-specific
SOB
Drowsiness
Confusion
Headache
25
Q

What are the signs of respiratory failure?

A 
Use of accessory muscles
Increased RR
Irregular breathing
Low O2 saturation
Drowsiness
Confusion
Signs of cause
26
Q

What immediate investigations are carried out for respiratory failure?

A

Arterial blood gases

27
Q

What are the principles of management for respiratory failure?

A 
Maintain adequate O2 delivery
Reduce respiratory workload
Maximise ventilation
Maintain stable pH/electrolytes
Try and target cause

MD2 Ambulatory Care and Emergency Medicine (29 decks)

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