Modified Desaturation Distance Ratio (mDDR) predicts prognosis in patients with Pulmonary Arterial Hypertension

Functional evaluation is important for the understanding and management of patients with Pulmonary Arterial Hypertension (PAH). The modified desaturation distance ratio (mDDR) is a parameter calculated using the 6-minute walk distance (and continuous peripheral oxygen saturation (SpO2) values during the test and has shown prognosis value in some chronic respiratory diseases. Currently, the cut-off 380 meters in the six-minute walk test (6MWT) has been used to assess prognosis in these patients. The aim of the present study was to predict the prognosis in PAH patients using the mDDR comparing it with the cut-off 380 meters in the 6MWT. This was a retrospective study, including prospective patients with PAH evaluated at the Pulmonary Hypertension Unit, in Hospital Clinic of Barcelona. A total of one hundred eighty one patients were assessed with a lung function test and a 6MWT. Changes in SpO2 (ΔSpO2) and those in Borg scale scores (ΔBorg) during the 6MWT were calculated by subtracting the values at baseline from those immediately after walking 6 minutes. Baseline demographic, clinical and functional characteristics of PAH patients are shown in Table 1. The 6MWD and the final SpO2 was 433 (328-492) meters and 90 (83-93)%, respectively (Table 2). Patients with a mDDR lower than 30 presented greater mortality at 5,10 and 15 years compared with patients with a mDDR greater than 30 (Figure 1). The mDDR is a better parameter than distance cut-off of 380 meters in 6MWT to predict prognosis in PAH patients (Figure 1). Further studies are needed to determine the role of mDDR in terms of disease progression and response to treatment in chronic respiratory patients.