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

PaO Time (s) Pathogenesis Hypoventilation V/Q inequality Shunt Diffusion impairment

Effects

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

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

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