[Increase in hypercapnia in exercise--an unloading strategy?].

BACKGROUND

Chronic hypercapnia seems to preserve the overloaded respiratory pump from manifest muscle failure. In order to get information about the regulation of the ventilation under exercise we investigated clinical stable hypercapnic patients.

PATIENTS AND METHODS

Twenty-one patients (20 males, 53.7 +/- 13.2 years) with obesity-hypoventilation syndrome (8), chronic obstructive lung disease (4), scoliosis (3), myopathy (2) and post-Tbc (2) were examined. Ventilation parameters (fb, Vt, VO2), respiratory muscle strength (PImax, PEmax), arterial blood gases (pO2, pCO2), respiratory quotient (RQ) and lactate were measured at rest and at the end of 5 minutes of maximal bicycle exercise. The control group consisted of 10 healthy persons.

RESULTS AND CONCLUSIONS

A significant augmentation of the pre-existing hypercapnia under exercise (reflecting hypoventilation in relation to the predicted value) was observed in all patients with chronically overloaded respiratory muscles. This mechanism seems to be wise because it protects the respiratory pump from failure.