14 Male Human Subjects participated in a comparison and single-blind randomized experimental study. That was approved by the Ethical Review Committee. All male subjects were in averaged age of 38.9±5 year old and a FEV1 4.60±0.70 Liter. A written consent was obtained for all the subjects prior their acceptance. No rejection happened during the recruiting. The eligibility criteria were: i. No significant cardiac and respiratory diseases known; ii. No epilepsy background; iii. No severe pathology requiring medication; iv. No pregnancy for woman; v. Face medium - size in relation of the gas mask. The exclusion criteria were: i. Refusals relate to wear the oesophageal catheter and for capillary punctures; ii. Claustrophobia; iii. Oesophageal wounds backgrounds; iv. No coronary background and stroke history; v. No face morphology incompatibility with the mask. Spirometry and usual health screening was also done before starting the clinical trial.