Tessa Schneeberger

Transcutaneous carbon-dioxide partial pressure trends during six-minute walk test in patients with very severe COPD

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 six-minute 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[Δ]>4mmHg); 26% preserved and 24% reduced TCPCO2. Nineteen (31%) patients presented EIH (TCPCO2>45mmHg). EIH was associated to higher 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. Overweight-BMI seems to carry a protective effect against EIH in very severe COPD.

Randomised controlled trial of adjunctive inspiratory muscle training for patients with COPD

Background This study aimed to investigate whether adjunctive inspiratory muscle training (IMT) can enhance the well-established benefits of pulmonary rehabilitation (PR) in patients with COPD. Methods 219 patients with COPD (FEV1: 42%±16% predicted) with inspiratory muscle weakness (PImax: 51±15 cm H2O) were randomised into an intervention group (IMT+PR; n=110) or a control group (Sham-IMT+PR; n=109) in this double-blind, multicentre randomised controlled trial between February 2012 and October 2016 (ClinicalTrials.gov NCT01397396). Improvement in 6 min walking distance (6MWD) was a priori defined as the primary outcome. Prespecified secondary outcomes included respiratory muscle function and endurance cycling time. Findings No significant differences between the intervention group (n=89) and the control group (n=85) in improvements in 6MWD were observed (0.3 m, 95% CI −13 to 14, p=0.967). Patients who completed assessments in the intervention group achieved larger gains in inspiratory muscle strength (effect size: 1.07, p<0.001) and endurance (effect size: 0.79, p<0.001) than patients in the control group. 75 s additional improvement in endurance cycling time (95% CI 1 to 149, p=0.048) and significant reductions in Borg dyspnoea score at isotime during the cycling test (95% CI −1.5 to −0.01, p=0.049) were observed in the intervention group. Interpretation Improvements in respiratory muscle function after adjunctive IMT did not translate into additional improvements in 6MWD (primary outcome). Additional gains in endurance time and reductions in symptoms of dyspnoea were observed during an endurance cycling test (secondary outcome) Trial registration number NCT01397396; Results.

Pulmonary Rehabilitation Outcomes after Single or Double Lung Transplantation in Patients with Chronic Obstructive Pulmonary Disease or Interstitial Lung Disease

Background: Pulmonary rehabilitation (PR) following lung transplantation (LTx) has been shown to be effective with regard to exercise capacity and health-related quality of life (HRQL). However, outcome data is limited with respect to LTx as a population. Differences concerning the effects of PR in patients with single LTx (SLTx) or double LTx (DLTx) have not been studied yet. Objectives: The aim was to compare possible differences concerning PR outcomes between SLTx and DLTx. Methods: In a retrospective analysis (period: 1997-2016), data from 722 patients with either chronic obstructive pulmonary disease (COPD; SLTx: n = 129, FEV1 51 ± 17% pred.; DLTx: n = 204, FEV1 74 ± 20% pred.) or interstitial lung disease (ILD; SLTx: n = 135, FVC 58 ± 18% pred.; DLTx: n = 254, FVC 63 ± 18% pred.) after LTx were included. All patients underwent a specialized inpatient PR program. The data of the 6-minute walk distance (6MWD) and HRQL (physical [PCS] and mental [MCS] component summary of the SF- 36 questionnaire) were analyzed. Results: Independently from the procedure and pretransplant diagnosis, patients significantly (p < 0.05) improved the 6MWD without any differences between SLTx and DLTx (COPD: SLTx: +109 ± 68 m, DLTx: +117 ± 82 m; ILD: SLTx: +115 ± 80 m, DLTx: +132 ± 77 m). The PCS (COPD: SLTx: +9 ± 9 points, DLTx: +7 ± 9 points; ILD: SLTx: +6 ± 9 points, DLTx: +9 ± 9 points) and MCS (COPD: SLTx: +8 ± 15 points, DLTx: +7 ± 15 points; ILD: SLTx: +10 ± 13 points, DLTx: +8 ± 12 points) also improved significantly without any group differences. Conclusions: LTx patients with a pretransplant diagnosis of COPD or ILD all benefitted significantly and with clinical relevance with regard to exercise capacity and HRQL from an inpatient PR performed within 1 year postoperatively. PR outcomes were similar regardless of SLTx or DLTx.

Accuracy of a transcutaneous carbon dioxide monitor during the 6-minute walk test in COPD patients - a pilot study

Background: Chronic respiratory failure can be associated with CO2 retention and hypercapnia during exercise in COPD patients. A continuously monitoring of transcutaneous CO2 levels (TcPCO2) may be useful to screen CO2 trends and to identify patients with exercise-induced hypercapnia (EIH). Objective: The aim of this study was to investigate the accuracy of the SenTec Digital Monitoring System (SDMS, SenTec AG, Therwil, Switzerland) during the 6-minute walk test (6MWT) in COPD patients. Methods: 10 COPD patients were enrolled in this prospective, pilot study. Capillary blood gases (CBG) from the earlobe were taken by the same investigator pre-6MWT and directly following 6MWT withTcPCO2 levels recorded simultaneously. To ensure a valid comparison between CBG and TcPCO2, values were taken at the same time point. An independent person set digital markers in the SenTec device concurrently with the taking of the CBG. Results: The agreement of PCO2 recording between CBG and SenTec device showed a very strong intra-class correlation coefficient for pre-walk (ICC=0.98, 95%CI: 0.93-0.99) and post-walk (ICC=0.98, 95CI: 0.73-0.99) values of the 6MWT (see Figure). Conclusion: Transcutaneously measured PCO2 values by the SDMS during 6MWT were highly accurate. The strong correlation with CBG and the continuous, non-invasive method could be advantageous to detect patients with EIH during the 6MWT.