Acute respiratory failure

Question 1

Definition of respiratory failure

Answer 1

Hypoxia, gas exchange inadequate. Subdivided into 2 categories

1. Type 1
2. Type 2

Question 2

Type 1 respiratory failure: definition and causes

Answer 2

VQ mismatch
Hypoxia with normal or low CO2

Pneumonia
Pulmonary edema
Asthma
PE
Emphysema
Fibrosing alveolitis
ARDS

Question 3

Type 2 respiratory failure: definition and causes

Answer 3

Alveolar hypoventilation
Hypoxic, hypercapnic

Pulmonary disease
Reduced respiratory drive
Neuromuscular disease
Thoracic wall

Question 4

Pulmonary disease cause T2RF

Answer 4

Asthma
COPD
Pneumonia
Pulmonary fibrosis
OSA

Question 5

Reduced respiratory drive causes of T2RF

Answer 5

Sedative drugs
Tumor
Trauma

Question 6

NM causes of T2RF

Answer 6

Cervical cord
GBS
MG
Polymyositis
Diaphragmatic paralysis

Question 7

Thoracic wall causes T2RF

Answer 7

Kyphoscoliosis

Flail chest

Question 8

Clinical features

Answer 8

1. Underlying cause
2. Hypoxic->dyspnea, restless, agitation, confusion, central cyanosis. If long standing may have polycythemia, pulmonary hypertension, cor pulmonale
3. Hypercapnia->headache, peripheral vasodilation, tachy, asterixis, bounding pulse, tremor, confusion, drowsy, coma

Question 9

Investigations

Answer 9

ABG->pH 50 mmHg on room air
ECG->evidence of PE, MI, heart disease
UEC
FBC->look for +WCC
CXR->diffuse or patchy infiltrates; pneumothorax; pulmonary effusion; hyper-inflation; asymmetrical opacification of lung fields; asymmetrical lucency of lung fields
Pulse oximetry-> Sp02% PEFR cultures

Question 10

Management of Type 1

Answer 10

Depends on cause
ABC
Give oxygen by facemask, 35-60%
Assisted ventilation if required->NIPPV, ETT with mechanical

Question 11

Management Type 2

Answer 11

Hypoxic drive
Treat underlying cause
Controlled 02 therapy 24%
Recheck ABG after 20 mins
If PCO2 is steady/lower, +02
If +PCO2 and still hypoxic, consider respiratory stimulant->doxapram, or NIPPV
If fails, intubate

Question 12

Follow-up requirements

Answer 12

Close F/U for first week after recovery to evaluate development of complications after NIPPV: sinus infection, middle ear infection, skin necrosis or ETT use->tracheal inflammation, nosocomial infection, pneumonia, lung abscess.

Patients need education about underlying causes of respiratory failure.

Question 13

Oxygen saturation aim for normal and those at risk of hypercapnia

Answer 13

Normal: 94-98

At risk of hypercapnia: 88-92

Question 14

Nasal cannulae: typical flow rate and concentration

Answer 14

1-4 L

24-40% oxygen saturation

Question 15

Simple face mask: risks, when not to use

Answer 15

Less precise than venturi
Do not use if hypercapnia or T2RF
Risk of CO2 accumulation if flow

Question 16

Venturi mask

Answer 16

Provides precise O2% at high flow rates
24% Blue
28% White
35% Yellow
40% Red
60% Green

Question 17

Non-rebreathing mask: oxygen concentration delivery, common use, when to avoid

Answer 17

Reservoir bag, deliver high oxygen 60-90% determined by inflow 10-15L/min
Commonly used in emergencies, imprecise, avoid in those requiring controlled 02 therapy.

Question 18

Other ways to +oxygenation

Answer 18

Treat anemia->transfusion may be required
Improve CO->treat heart failure
Chest physio to +ventilation/perfusion mismatch

Question 19

When to consider ABG

Answer 19

Unexpected deterioration in ill
Acute exacerbation of chronic chest condition
Impaired consciousness or impaired respiratory effort
Signs of CO2 retention
Drowsy, bounding pulse, asterixis, HA
Cyanosis, confusion, irritability, hallucinations
To validate measurements for transcutaneous oximetry