Observational study summary The goal of this observational study is to determine whether an outpatient pulmonary rehabilitation (PR) program-already known to be effective and safe for chronic obstructive pulmonary disease (COPD)-is equally effective and well-tolerated when COPD is complicated by pulmonary hypertension (PH).

Main question In adults with COPD + PH, does outpatient PR improve six-minute walk distance (6MWD) and remain safe, to the same extent as in adults with COPD without PH?

How the study is conducted

Researchers retrospectively analyse medical records from the University Hospital of Poitiers covering a ten-year period. Eligible participants are adults with COPD who completed at least three weeks of supervised PR and underwent echocardiography to assess PH probability. Two cohorts are compared:

COPD + PH (intermediate or high echocardiographic suspicion) COPD without PH (no echocardiographic suspicion) Key data collected Change in 6MWD between the start and end of PR (primary endpoint) Proportion of participants achieving a clinically meaningful improvement in 6MWD Occurrence of severe exacerbations (hospital- or emergency-treated events) during the year after PR All-cause mortality within one year Adverse events or program interruptions indicating PR tolerance

Inclusion Criteria:

• Age 18 years or older
• Spirometry-confirmed chronic obstructive pulmonary disease with a post-bronchodilator FEV1 / FVC ratio below 0 .70
• Completion of at least three consecutive weeks of outpatient pulmonary rehabilitation between January 2013 and December 2023 at the University - Hospital of Poitiers centre
• Six-minute walk test performed within seven days before programme start and repeated during the final week
• Transthoracic echocardiogram carried out within one year before or one year after programme start, used to grade pulmonary hypertension

Exclusion Criteria:

• Pulmonary rehabilitation shorter than three weeks or missing six-minute walk test or echocardiogram data

• Chronic lung disease other than chronic obstructive pulmonary disease or previous lung transplantation

  -,Hospital admission for an acute chronic obstructive pulmonary disease exacerbation in the four weeks preceding rehabilitation

• Unstable cardiovascular disease that contraindicates exercise training

• Active cancer with an expected survival under one year

• Pregnancy at the time of rehabilitation

• Documented refusal to allow medical data to be used for research

The source population consists of adults (18 years and older) with spirometry-confirmed chronic obstructive pulmonary disease who attended at least three consecutive weeks of supervised outpatient pulmonary rehabilitation at the University Hospital of Poitiers (France) between January 2013 and December 2023. Every individual had a six-minute walk test recorded both immediately before the programme and during its final week, plus a transthoracic echocardiogram performed within one year before or after programme start to grade the probability of pulmonary hypertension. Most candidates were current or former smokers with moderate-to-severe airflow limitation and common cardiometabolic or sleep-related comorbidities. Patients are classified into two analytic cohorts-COPD with pulmonary hypertension and COPD without pulmonary hypertension-according to their echocardiographic findings.

The individual participant data will not be shared because this is a retrospective single-center study based on medical records, and no explicit consent for data sharing was obtained from participants.