to assess the effectiveness of helium:oxygen mixture adjunct with non-invasive ventilation in sulfur mustard exposed patients with acute decompensation

Inclusion Criteria:

• a history of previous exposure to sulfur mustard
• worsening dyspnea during the last 10 days
• respiratory rate >25/min
• arterial pH<7.35
• PaCO2 of >50 mmHg
• PaO2 of <50 mmHg

Exclusion Criteria:

• recent pneumothorax (<1 month)
• severe respiratory failure or hemodynamic instability with forthcoming intubation
• FIO2 of <0.4
• impaired consciousness or absence of patient cooperation
• facial lesions precluding NIV