In healthy subjects fitted with a nasogastric double balloon catheter and breathing at a resistance, the investigators will measure time to failure, Borg ratings, VO2, VCO2, flow, esophageal-, gastric- and airway-pressure. This will be done during breathing at either a square wave or triangle wave pressure waveform, in random order and trials separated by >two days. Further respiratory muscle fatigue will be investigated pre and post intervention by maximal esophageal pressure generation (voluntary and with cervical magnetic stimulation).
The study aims at investigating if time to respiratory muscle fatigue and metabolism are influenced by the pressure wave form mode applied during resistive breathing.