Respiratory failure

31/08/2011

Vivian Ho

Contents• Definition• Types• Pathogenesis• Effects• Blood gases• Management

Definition• Failure to maintain gas exchange• Numbers…

pO2 < 60 mmHg pCO2 > 50mmHg

Types• Acute / acute on chronic / chronic

• Type 1 vs Type 2

• Causes

Pathogenesis• Hypoventilation • V/Q inequality• Shunt• Diffusion impairment

Pathogenesis• Hypoventilation • V/Q inequality• Shunt• Diffusion impairment

Pathogenesis• Hypoventilation • V/Q inequality• Shunt• Diffusion impairment

PaO2

40

0.25 0.75 Time (s)

Pathogenesis• Hypoventilation • V/Q inequality• Shunt• Diffusion impairment

Effects

Blood gases 1pH 7.47pCO2 33pO2 47Na 144 K 3.7HCO3 24BE 0.5FiO2 55%

Blood gases 2pH 7.19pCO2 74pO2 59Na 132 K 4.7HCO3 28BE -1.6FiO2 35%

Blood gases 3pH 7.46pCO2 30pO2 58Na 136 K 4.8HCO3 21BE -2FiO2 85%

Management• Treat cause

• Oxygen

• Ventilatory support

To tube or not to tube

Ventilatory support

NIV• What is it?• How does it work?• When does it work? • What does the evidence suggest?

NIV• Indications

– Hypercapnic respiratory failure– COPD with resp acidosis pH 7.25-7.35 – Cardiogenic pulmonary oedema– Pneumonia in the immunosuppressed– Weaning from the ventilator in

hypercapnic COPD patients

NIV• Contraindications

– Airway – Facial abn– Respiratory Arrest– Severe hypoxaemia– Untreated pneumothorax– Haemodynamic instability– Agitation– GI bleed / ileus/ surg

Cochrane• NIV vs Medical therapy alone

– Lower mortality NNT 8

– Prevent intubation NNT 5

– Length of stay – Improved pH/paCO2/RR within 1h of

tx

NIV• Compared with intubation..

– Hosp acq pneumonia– Complications

Mechanical Ventilation• Indications for intubation

– Airway– Ventilation – Improve Oxygenation– Decrease work of breathing– Stabilise chest wall in severe injury

Summary• Resp failure is the inability to

maintain adequate gas exchange• Type 1: hypoxaemic• Type 2: hypercapnic + hypoxaemic• NIV should be considered in

– patients with hypercapnic resp failure – cardiogenic pulmonary oedema – pneumonia in immunosuppressed