Agreement Between 5 Different Pulse Oximeters Used Simultaneously During a Six-minute Walk Test

Inclusion Criteria: * All patients referred to our Cardiorespiratory Unit for a pulmonary rehabilitation programme * Aged over 18, no maximum age limit * Absence of language barriers or cognitive impairments that would make it impossible to explain the protocol * Resting SpO2 \> 90% * Signing the informed consent form after receiving detailed information about the study. Exclusion Criteria: * Any clinical condition that makes it impossible or compromises the performance of a walking test: unstable heart disease, acute myocarditis and/or pericarditis, acute arrhythmia, severe pulmonary hypertension, deep vein thrombosis, severe asthma, acute orthopaedic or rheumatic condition * Unstable clinical condition (patient hospitalised or less than 4 weeks after an exacerbation leading to hospitalisation) * Oxygen therapy at rest and/or during walking * Uncontrolled arterial hypertension (AHT) at rest * Known cardiac rhythm disorder * Unexplained chest pain at rest * Mechanical interference with the possibility of placing pulse oximeters: skin lesions, bandages, plaster casts, etc. * Withdrawal of consent during the study * Systemic scleroderma, sclerodactyly, history of any type of vasculitis * Symptomatic Raynaud's phenomenon * Marked clubbing * Known haemoglobinopathy * Refusal to remove nail polish