The aim of this study is a detailed investigation of the effect of High Flow Nasal Oxygenation (HFNO) on respiratory system characteristics and ventilation parameters in healthy adult subjects and the subsequent use of measured data to answer the following questions:

What level of positive end expiratory pressure (PEEP) causes a HFNO with different flow rates? Does HFNO work as pressure support or does it act more like a Continuous Positive Airway Pressure (CPAP) ventilation?

High Flow Oxygen through nasal cannula is widely used in the setting of hypoxemic respiratory failure of heterogenous etiology with very good patients compliance.

However, the evidence of what level of PEEP or pressure support (if any) with different flow rates is weak.

Our goal is to determine these effects and compare them with standard approach with non-invasive ventilation via full face mask.

Inclusion Criteria:

• healthy volunteers willing to participate

Exclusion Criteria:

• general contraindications for oesophageal catheter insertion: oesophageal varices, bleeding disorders (including anticoagulant medication), diverticulitis, oesophageal tumors, history of recent oesophageal/gastric surgery, recent epistaxis,
• sinusitis
• allergy to local anesthetics
• subject refusal