Noninvasive ventilation and the potential risk of transmission of infection.

Noninvasive positive-pressure ventilation (NPPV) is becoming increasingly used in patients with acute respiratory failure caused by a wide range of infectious aetiologies such as human-adapted avian influenza, aspergillosis and varicella [2–4], in order to avoid intubation or as a bridge to invasive mechanical ventilation. Substantial exposure to exhaled air occurs within a 0.5-m radius of patients receiving NPPV at usual pressures (expiratory positive airway pressure 45 cmH2O (0.39 kPa); inspiratory positive airway pressure 1,215 cmH2O (1.18 kPa)): higher ventilator pressures result in a wider distribution of exhaled air [5]. Indeed, in the recently proposed World Health Organization interim guidelines on prevention and control of acute respiratory diseases in healthcare, NIV has been included among those aerosol-generating procedures in which the risk of pathogen transmission is still ‘‘controversial/possible’’ but not documented [6].