Breathing pattern and ventilatory response to CO2 during exercise.

ABSTRACT

The aim of this study was to determine during moderate exercise whether response to the CO2 rebreathing test was dependent on differences in breathing pattern components among individuals recorded before the test and whether differences in tidal volume response and/or breathing frequency response to CO2 during the test could influence their ventilatory response to CO2. Ten healthy, sedentary male subjects, 20 to 34 years old, participated in the study. Ventilatory response to CO2 was measured by the CO2 rebreathing method (7% CO2, 50% O2). The measurements of breathing pattern components and CO2 rebreathing were made during mild steady state exercise VCO2 = 20 ml.kg-1.min-1. We measured the following 1) tidal volume (VTex) and breathing frequency (fex) before CO2 rebreathing and 2) ventilatory response to CO2 (SVEex), tidal volume response to CO2 (SVTex), and breathing frequency response to CO2 (Sfex) during the CO2 rebreathing test. The results showed that SVEex was correlated with VTex (r = 0.89, p less than 0.001), fex (r = -0.79, p less than 0.01), and Sfex (r = 0.83, p less than 0.01). There was no correlation between SVEex and SVTex. A curvilinear relationship existed between SVEex and alveolar ventilation calculated during exercise (r = 0.87, p less than 0.001), but there was no correlation with dead space. Sfex was positively correlated with VTex (r = 0.68, p less than 0.05) and negatively with fex (r = -0.70, p less than 0.05). We concluded that, during moderate exercise, higher tidal volumes measured before CO2 rebreathing were associated with higher response to the CO2 rebreathing test and consequently with higher ventilatory response to CO2.(ABSTRACT TRUNCATED AT 250 WORDS)