In ten eucapnic patients with chronic obstructive lung disease (COLD) we evaluated the breathing patterns during induced progressive hypercapnia (CO2 rebreathing) and progressive exercise on an ergometric bicycle (30 W/3 min). The time and volume components of the respiratory cycle were measured breath by breath. When compared to hypercapnia, the increase in ventilation (V̇E) during exercise was associated with a smaller increase in tidal volume (VT) and a greater increase in respiratory frequency (fR). Plots of tidal volume (VT) against both inspiratory time (TI) and expiratory time (TE) showed a greater decrease in both TI and TE during exercise than with hypercapnia. Analysis of V̇E in terms of flow (VT/TI) and timing (TI/TT) showed V̇E to increase by a similar increase to that in VT/TI during both exercise and hypercapnia, while TI/TT did not change significantly. When the patients were matched for a given VE (28 l·min-1), exercise induced a smaller increase in VT (p <0.05), a greater increase in fR (p <0.025); TI (p <0.025) and TE (p <0.01) were found to be smaller during exercise than hypercapnia. The change in the off-switch mechanism during exercise and hypercapnia could account for our results.
|Number of pages||6|
|Journal||European Respiratory Journal|
|Publication status||Published - 1988|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine