Non-invasive ventilation for acute exacerbations of COPD: a new standard of care

Acute exacerbations of chronic obstructive pulmonary disease (COPD) are a frequent cause of admission to hospital and the intensive care unit (ICU). During these episodes a major deterioration in gas exchange is accompanied by a worsening in the clinical condition of the patient, characterised by a rapid and shallow breathing pattern, severe dyspnoea, right ventricular failure, and encephalopathy. The pathophysiological pathway of all these features is the inability of the respiratory system to maintain adequate alveolar ventilation in the presence of major abnormalities in respiratory mechanics. Hypercapnia, acidosis, and hypoxaemia all ensue, leading to clinical deterioration in cardiovascular and neurological functions. What triggers the abnormal breathing pattern of the patient is still unclear. Although it has been suggested that rapid shallow breathing may afford a protection against the development of respiratory muscle fatigue, this notion has been challenged by studies of weaning off mechanical ventilation where the occurrence of acute respiratory failure can be closely monitored and analysed.1 2 The key element during decompensation seems to be the shortening of the inspiratory time, inducing both a decrease in tidal volume and an increase in respiratory frequency. Because this is associated with, or is secondary to, excessive respiratory loads, treatment should be directed at reducing the loads imposed on the respiratory muscles. Unfortunately, the ability of medical treatment to reverse severe respiratory failure in these patients is limited. When hypoventilation becomes so severe that several organ dysfunctions occur, there is no choice other than to provide “artificial” ventilation to avoid a fatal outcome. The traditional way has been to use endotracheal intubation as a means of access to the lower airways and to deliver ventilation to the patient's lungs. A more recent approach, called non-invasive ventilation (NIV), has profoundly changed the management and outcome of these patients.3 4

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