Discussion
This study provides four major observations: (1) PCO2 response
to exercise is highly heterogeneous in patients with advanced
COPD; (2) half of the patients (50%) demonstrated CO2 retention, whereas a 31% of total population exhibited EIH during the
6MWT; (3) exercise-induced CO2 retention is mostly determined
by worse airflow limitation while EIH is mostly associated with
higher baseline PCCO2 levels; and (4) overweight BMI may prevent
the occurrence of EIH in very severe COPD. To the best of our knowledge, this is the first study to demonstrate the patterns of TCPCO2
trends in the 6MWT using continuous recording of CO2 and to reveal
the determinants of CO2 retention and EIH during walking in GOLD
stage IV.