Decreased ventilatory response to carbon dioxide by steady state in patients with myotonic dystrophy type 1 compared to healthy subjects

Abstract

Background and objective: Ventilation is exquisitely sensitive to increased PCO2. Carbon dioxide produces its effects by stimulating both central and peripheral chemoreceptors. The testing of such ventilatory response to CO2 can be achieved either by steady state or rebreathing (Read) methods. In order to test the hypothesis based upon abnormality of the central ventilatory control mechanisms in myotonic dystrophy, contributing to chronic alveolar hypoventilation, we compared the ventilatory response to CO2 between control subjects and patients with myotonic dystrophy type 1 (MD1).

Methods: Ventilatory response to CO2 was achieved in a steady state while breathing gas mixtures containing 3% and 6% of CO2. Each concentration was successively inhaled during 5 minutes following spontaneous breathing room air for at least 10 min. While seated in a comfortable chair, ventilation and PETCO2 were continuously recorded.

Results: Twenty one controls and 51 MD1 patients were studied. In controls mean ventilatory responses to CO2 were 1.18 L/min/mmHg ± 0.71 (CO2= 3%) and 1.25 L/min/mmHg ± 0.72 (CO2= 6%). In MD1 patients mean ventilatory responses to CO2 were 0.71 L/min/mmHg ± 0.46 (CO2= 3%) and 0.75 L/min/mmHg ± 0.36 (CO2= 6%). For both concentrations, ventylatory response to CO2 was significantly lower (p<0.01) in MD1 patients than in controls.

Conclusion: This control study confirms the decreased ventilatory response to CO2 in MD1 patients using the alternative steady state method. Further studies are needed to define more precisely the role of the impairment of the central ventilatory control in the course of the disease.