Effect of high and low level breathing support delivered via a mask during walking in patients with severe kyphoscoliosis

Each participant performed 4 endurance treadmill tests within one day. One test was performed unassisted, one with continous positive airway pressure (CPAP) of 4cmH2O, one with low level pressure support (PS) of 10cmH2O and one with high level PS of 20cmH2O. Tests were performed in random order. Prior to performing each exercise test, participants rested in the sitting position for 10 minutes. Of the 10 minute rest period, participants breathed unassisted for the first 5 minues. For the second 5 minutes of rest, participants breathed on CPAP prior to the CPAP walk test, PS 10 prior to the PS 10 walk test, PS 20 prior to the PS 20 walk test, and a further 5 minute period of breathing unassisted prior to the unassisted walking test. Participants rested for at least 30 minutes while breathing unassisted between each exercise test (and until heart rate, blood pressure, breathlessness, oxygen saturation and exertion had returned to baseline). Participants only received CPAP, PS 10 and PS 20 for the duration of the endurance walk test and 5 minute rest period immediately prior to the walk test as described above.