Non-invasive ventilation as a prehospital intervention for acute COPD exacerbation

Chronic obstructive pulmonary disease (COPD) is progressive and not fully reversible. It is characterised by increasing airflow obstruction, predominantly caused by smoking, although exposure to occupational dusts, chemicals and air pollution are also considered risk factors (Brashers and Huether, 2014). COPD is the second most common respiratory disease in the UK, with 1.2 million people (2% of the population) suffering from the condition (Snell et al, 2016). Airflow obstruction occurs as a result of airway and parenchymal damage, caused by chronic inflammation (National Institute for Health and Care Excellence (NICE), 2010). Exacerbations of COPD are common, where symptoms become pronounced and unstable compared with those on a daily basis, characterised by rapid dyspnoea and hypoxaemia (Clancy and McVicar, 2009).

The clinical forms of COPD are chronic bronchitis and emphysema, although guidelines discourage differentiation between the two forms when making a diagnosis (NICE, 2010). Chronic bronchitis is defined as hypersecretion of mucus and a productive cough over 3 months of the year for at least 2 consecutive years (Brashers and Huether, 2014). Bronchitis occurs as a result of the inhalation of irritants which cause airway inflammation, leading to bronchial oedema, bronchospasm and increased mucous in the epithelium. Impaired ciliary function impedes the clearance of mucous, resulting in frequent infections and mucous plugging (Colbert et al, 2009; Brashers and Huether, 2014). Chronic inflammation results in hypertrophied bronchial smooth muscle and progression of inflammation to other airways; this leads to narrowing of the airways, which worsens during the expiration phase when airways are constricted (Brashers and Huether, 2014).