title: Influence of exercise and CO2 on breathing pattern in patients with chronic obstructive lung disease (COLD).
abstract: In ten eucapnic patients with chronic obstructive lung disease (COLD) we evaluated the breathing pattern 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 (VE) 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 VE in terms of flow (VT/TI) and timing (TI/TT) showed VE 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 less than 0.05), a greater increase in fR (p less than 0.025); TI (p less than 0.025) and TE (p less than 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.
mesh_terms: D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000502:physiology*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D012123:Pulmonary Ventilation; D012119:Respiration; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide