Respiratory failure

Question 1

Define respiratory failure

Answer 1

Acute or chronic impairment of gas exchange between the lungs and blood - causes hypoxia with/without hypercapnia

Question 2

Type 1 respiratory failure

Answer 2

Hypoxic respiratory failure

• no hypercapniea
• Arterial PaO2 <60mmHg

Question 3

Type 2 respiratory failure

Answer 3

Hypercapnic respiratory failure

• Arterial PaO2 <60mmHg
• Arterial PaCO2 >50mmHg

Question 4

Normal PaO2

Answer 4

75-100mmHg

Question 5

Normal PaCO2

Answer 5

38-42mmHg

Question 6

Mortality from respiratory failure

Answer 6

20-40%

Question 7

Gender differences in respiratory failure

Answer 7

M=F

Question 8

What pulmonary infection is most often associated with respiratory failiure

Answer 8

Pneumonia

Question 9

3 main causes of respiratory failure

Answer 9

• Respiratory causes
• Non-respiratory causes
• Traumatic causes

Question 10

Respiratory causes of respiratory failure

Answer 10

• Acute exacerbation of asthma
• Pulmonary embolism
• Pulmonary oedema
• Acute respiratory distress syndrome (ARDS)
• Pneumonia
• Acute epiglotitis

Question 11

Non-respiratory causes of respiratory failure

Answer 11

• Hypovolaemia
• Shock
• Severe anaemia
• Drug overdose
• Neuromuscular disorder

Question 12

Traumatic causes of respiratory failure

Answer 12

• Blood loss
• Direct thoracic injury
• Pulmonary contusion

Question 13

3 broad reasons for hypercapnic respiratory failure

Answer 13

1. Increased dead space - anatomical
2. Reduced minute ventilation
3. Increased CO2 production

Question 14

Causes for increased dead space in respiratory failure

Answer 14

• PE
• Vascular disease
• Hyperinflation

Question 15

2 causes of reduced minute ventilation

Answer 15

• Decreased central respiratory drive

- Decreased respiratory neuromuscular/thoracic cage function

Question 16

Reasons for decreased central respiratory drive

Answer 16

• Sedatives
• Encephalitis
• Stroke
• Sleep apnoea
• Alkalosis
• Hypothyroidism
• Hypothermia
• Starvation

Question 17

Reasons for decreased respiratory neuromuscular/thoracic cage function

Answer 17

• MND
• Muscular disorders
• Toxins

Question 18

Difference between hypoxia and hypoxaemia

Answer 18

• Hypoxaemia - PaO2 low

- Hypoxia - low O2 at tissue level

Question 19

Pathophysiology of respiratory failure

Answer 19

• CO2/O2 exchange fails

- Metabolic demands for O2 and body system acid base stabilisation are not maintained

Question 20

Type 1 and 2 respiratory failure have what in common?

Answer 20

• Hypoxemia

- Causes cellular anoxia and tissue asphyxia

Question 21

Consequence of chronic hypoxia

Answer 21

Stimulates increases int he number of circulating RBC (erythrocytosis)

Question 22

What does hypercapnia cause

Answer 22

• Carbonic acid accumulation

- Respiratory acidosis

Question 23

Causes of hypercapnia

Answer 23

• Poor ventilatory muscle function
• Obstructed airways and alveoli
• Secretions in small airways
• Chest wall abnormalities

Question 24

Classification of acute respiratory failure

Answer 24

• Acute lack of O2 transfer to the blood by the respiratory systems OR acute failure of the respiratory system to remove CO2

Question 25

Classification of chronic respiratory failure

Answer 25

- Long-term lack of O2 delivery to the blood by the respiratory system - Worsening respiratory acidosis - Chronically low PaO2 or high PaCO2 - High carbonic acid with renal compensation (increased reabsorption of bicarbonate) - Increased RBC count

Question 26

Classification of type 1 hypoxic respiratory failure

Answer 26

PaO2 <60mmHg or 10% decrease in baseline | chronic lung disease may have PaO2 50mmHg already

Question 27

Classification of type 2 hypercapnic respiratory failure

Answer 27

PaO2 <60mmHg and PaCO2 >50mmHg

Question 28

Clinical presentation of type 1 respiratory failure

Answer 28

- Dyspnoea - Agitation - Anxiety - Headache - Confusion - Somnolence - Seizure - Tachypnoea - fatigues - decreased RR

Question 29

Clinical presentation of type 2 respiratory failure

Answer 29

* ** Generally tolerate symptoms better * ** Respiratory failure develops more slowly - Headache - Confusion - Disorientated - Coma - Seizure - Hypoventilate - respiratory acidosis - Agitation - Slurred speech - Tremour

Question 30

Symptoms of SEVERE hypercapnia

Answer 30

- Asterixis - Myoclonus (jerky movements) - Seizures - Papilloedema (optic nerve swelling) - Dilated superficial veins

Question 31

At what PaCO2 is there a decreased level of consciousness

Answer 31

PaCO2 >75mmHg | if chronic - may only develop symptoms >90mmHg

Question 32

Risk factors for respiratory failure

Answer 32

- Smoking - Young or old - Pulmonary infection - Chronic lung disease - Upper and lower airway obstruction - Alveolar abnormalities - Perfusion abnormalities - Cardiac failure - Peripheral nerve abnormalities - Muscle system abnormalities - Opiates + sedatives - Toxic fumes/gases - Traumatic spinal injury

Question 33

Investigations for respiratory failure

Answer 33

- Pulse oximetry - Blood gas analysis - FBC - ECG - CXR - Capnometry (measures CO2 in expired gases) - Pulmonary function test - Toxicology testing - Chest CT - CTPA - V/Q lung scanning - Cardiothoracic US

Question 34

DDX for respiratory failure

Answer 34

- Hyperventilation secondary to metabolic acidosis - Hyperventilation secondary to anxiety - Sleep apnoea - Obesity

Question 35

Acute management of respiratory failure

Answer 35

- Airway clearance - Supplemental O2 - Treat underlying cause If unconscious - endotracheal intubation and mechanical ventilation

Question 36

Complications of respiratory failure

Answer 36

- Pneumothorax - Endotracheal tube misplacement/dislodgement - Nosocomial infection - Throat pain with intubation

Question 37

Describe chronic type 2 respiratory failure

Answer 37

High PaCO2 but normal pH due to renal compensation