Background: Transcutaneous carbon-dioxide partial-pressure (TCPCO2) can be reliably measured and may
be of clinical relevance in COPD. Changes in TCPCO2 and exercise-induced hypercapnia (EIH) during sixminute walk test (6MWT) need further investigation. We aimed (1) to define patterns of TCPCO2 trends
during 6MWT and (2) to study determinants of CO2-retention and EIH.
Methods: Sixty-two COPD patients (age: 63 ± 8years, FEV1: 33 ± 10%pred.) were recruited and TCPCO2
was recorded by SenTec digital-monitoring-system during 6MWT.
Results: Half of patients (50%) exhibited CO2-retention (TCPCO2 [] >4 mmHg); 26% preserved and 24%
reducedTCPCO2.Nineteen(31%)patientspresentedEIH(TCPCO2 >45 mmHg).EIHwasassociatedtohigher
baseline-PCCO2, worse FEV1, lower inspiratory-pressures, underweight/normal BMI, and pre-walk dyspnea. Stronger determinants of CO2-retention were FEV1 and pre-walk dyspnea, whereas baseline-PCCO2
and pre-walk dyspnea better predict EIH.
Conclusions: PCO2 response to 6MWT is highly heterogeneous; however, very low FEV1 and elevated
baseline-PCCO2 together with pre-walk dyspnea increase the risk for CO2-retention and EIH. OverweightBMI seems to carry a protective effect against EIH in very severe COPD