Combination of High-flow Nasal Oxygen (Optiflow) and Vibrating Membrane Nebuliser (Aerogen) in the Pre-hospital Setting - Before/After Study

The aim of this observational before/after study is to determine how to optimally administer oxygen to patients experiencing an asthma or COPD exacerbation in emergency medical services. The aim will be to determine which method will achieve the target oxygen saturation objectives: \> 95% in asthma exacerbations and between 88% and 92% (or \> 92% in ambient air or with FiO2 21%) in COPD exacerbations. The study will compare a group "before" receiving standard care with a nebulizer mask to a group "after" using a combination of a vibrating membrane nebulizer and high-flow nasal oxygen.

Inclusion Criteria: * ≥ 18 years of age * Exacerbation of asthma or COPD requiring nebulization * Free and informed consent Exclusion Criteria: * Clinical signs of hypercapnia * Non French speaker * Contraindications to high-flow nasal oxygen: haemodynamic instability, Glasgow \< 12, cardiorespiratory arrest, lack of airway protection, cardiogenic pulmonary oedema * Indication for orotracheal intubation