The analysis of the two subgroups disclosed that IMPROVER presented lower PEF than
NONIMPROVER. According to Krowka et al. PEF correlates with the maximum
transpulmonary pressure and varies with the degree of expiratory effort made by the patient.
Considering that all patients performed a maximum effort and that the results were reproducible with
a variation of less than 10%, PEF reflected the degree of respiratory system elastic recoil and the
calibre of the airway. Thus, we can probably assume that patients with greater loss in the elastic
recoil and/or an increase in the airflow resistance can benefit from PLB. IMPROVER also showed a
smaller V’E at the peak of exercise than NONIMPROVER, which was independent of the respiratory strategy adopted. It thus seems that the subgroup that improves exercise tolerance under PLB presents a greater ventilatory limitation.