Fig. 2
Standard tests of air hunger and work/effort. Left: Typical raw data set for the air hunger (AH) test during which two levels of end-tidal PCO2 were imposed and ventilation was constrained. The vertical dashed lines indicate the steady state level of AH associated with the test level of CO2 chosen to elicit 50%VAS ratings in pre-mist trials. Right: Typical raw data set for the work effort (WE) test in which two levels of targeted VT were imposed and normocapnia was maintained. The vertical dashed lines indicate the steady state level of WE associated with the test level of VT chosen to elicit 50% VAS ratings in pre-mist trials. During both tests ventilatory constraint or targeting was suspended briefly and participants were instructed to take a sigh. VAS ratings were provided every 15 s in response to a LED cue. VT Tidal volume, PAW continuous airway pressure measured at the mouth