Clinical Medicine Insights: Circulatory, Respiratory and Pulmonary Medicine

Introduction: Submaximal exercise gas exchange may be a useful tool to track responses to therapy in pulmonary arterial hypertension (PAH) patients.

Methods: Three patients diagnosed with idiopathic PAH, on differing therapies, were included. Standard clinical tests (echocardiogra- phy; 6 minute walk) were performed pre and 3–5 months after treatment. Gas exchange was measured during 3 minutes of step exercise at both time points.

Results: Gas exchange variables, end tidal CO2 (PET CO2) and the ratio of ventilation to CO2 production (VE/VCO2), during submaximal exercise were able to track patient responses to therapy over a 3–5 month period. Two patients demonstrated positive improvements, with an increased PETCO2 and decreased VE/VCO2 during light exercise, in response to an altered therapeutic regime. The third patient had a worsening of gas exchange (decreased PETCO2 and increased VE/VCO2) following no changes in the medical regime from the baseline visit.

Conclusion: Gas exchange variables measured during light submaximal exercise, such as PETCO2 and VE/VCO2, may be able to better detect small changes in functional status following treatment and could, therefore, be a useful tool to track disease severity in PAH patients. Further study is required to determine the clinical usefulness of these gas exchange variables.