The global peripheral chemoreflex drive in patients with systemic sclerosis: a rebreathing and exercise study

Abstract

Background: Exercise intolerance (EI) in systemic sclerosis (SSc) is difficult to manage by the clinician. The peripheral chemoreflex drive compensates for metabolic acidosis during exercise and may be related to EI.

Aim: To assess the global peripheral chemoreflex drive (GPCD) in patients with SSc at rest and during exercise.

Methods: Consecutively tested SSc patients (n = 49) were evaluated by pulmonary function tests, carbon dioxide (CO2) rebreathing studies and non-invasive cardiopulmonary exercise testing (CPET). Results of their CO2 rebreathing tests were compared with those of controls (n = 32). Respiratory compensation for metabolic acidosis during CPET was defined by the occurrence of a sharp increase in minute ventilation (VdotE) and the ventilatory equivalent for CO2 (V'E and V'CO2) at the end of the isocapnic buffer phase. Euoxic (eVHR) and hyperoxic (hVHR) ventilatory responses to hypercapnia were measured and its difference (eVHR - hVHR) was considered to reflect the GPCD.

Results: In 45 patients with SSc, CPET results showed respiratory compensation at the occurrence of metabolic acidosis. eVHR - hVHR in patients with diffuse cutaneous SSc (dcSSc) differed significantly from that in patients with limited cutaneous SSc (lcSSc) and from that in controls (0.47 ± 0.38 (dcSSc) vs. 0.90 ± 0.77 (lcSSc) and 0.90 ± 0.49 (controls) l/min/mmHg; P = 0.04 and P = 0.03, respectively).

Conclusions: Respiratory compensation for metabolic acidosis occurred in all patients. However, the GPCD was diminished in dcSSc patients, suggesting an altered control of breathing. Its assessment may help the clinician to better understand reported EI and exertional dyspnea in dcSSc patients.