chapter  5
16 Pages

Continuous positive airway pressure and non-invasive ventilation in acute hypoxaemic respiratory failure A K Simonds

Physiological considerations 57

CPAP use in acute hypoxaemic respiratory failure 58

NIV in heterogeneous acute respiratory failure 58

NIV in severe acute respiratory syndrome and pandemic flu 60

NIV in immunosuppressed patients with acute respiratory failure 63

NIV in acute severe asthma 64

CPAP and NIV in acute cardiogenic pulmonary oedema 64

NIV in chest trauma 67

NIV post extubation in non-COPD patients 67

NIV in patients with acute respiratory failure with malignant disease or who refuse endotracheal intubation 67

General applicability of NIV in non-COPD causes of acute respiratory failure 68

References 69

PHYSIOLOGICAL CONSIDERATIONS

Continuous positive airway pressure (CPAP) therapy has been used for many decades to treat acute hypoxaemic respiratory failure (ARF) due to acute pulmonary oedema, and pneumonia. Not only can it reduce the work of breathing, but it may also recruit alveoli and improve functional residual capacity. In ARF the work of breathing may increase such that the metabolic demand for oxygen increases to 25 per cent of total oxygen delivery. If cardiac function is depressed, oxygen delivery is reduced to vital organs and cardiac ischaemia will exacerbate the cardiopulmonary decline. In general ARF patients noninvasive ventilation (NIV) is likely to be more effective at reducing the work of breathing than CPAP, although this may not be the case in acute cardiogenic pulmonary oedema.