SNIP and SNEP

SNIP was performed using a nasal plug attached to one of the nostrils and consisted of performing a maximum and rapid inspiratory effort (sniff). The following criteria were used for accepting SNIP maneuvers: highest peak pressure value without leakage, duration of the inspiratory effort up to 500 ms, maneuvers performed from functional residual capacity, peak pressure held for less than 50 ms, and pressure waveform displaying smooth curves [6, 20]. Technical criteria were followed by the European Respiratory Society [3], and reference values were obtained according to Araújo et al. [9].

SNEP was performed using an inflatable face mask (dead space of approximately 150 ml) fixed to the participant through a headgear (Vital Signs, New Jersey, USA). The face mask had two orifices: one to dissipate the pressure generated during the test (2 mm) and another to allow participants to breathe freely before the test and between maneuvers (15 mm). The second orifice was connected to a one-way inspiratory valve during the tests. The test consisted of maximum and rapid expirations (nose-blowing) from functional residual capacity with the mouth closed. The larger orifice was manually occluded during each maneuver and reopened right after the test. Participants were instructed on how to perform each maneuver. Twenty maneuvers of each test were conducted with a 30-second interval in between, and two tests were conducted 15 minutes before the protocol for familiarization.