CARBON-DIOXIDE RESPIRATORY RESPONSE DURING POSITIVE INSPIRATORY PRESSURE IN COPD PATIENTS

The aim of this study was to compare the effect of inspiratory pressur e support (IFS) on the respiratory CO2 response in 13 stable COPD pati ents and in 13 normal subjects. Without IFS, the slopes of the ventila tory response to CO2 were lower in the patients than in the normal sub jects (mean +/- SEM, 0.82 +/- 0.19 vs. 1.69 +/- 0.31 l.min(-) l.mmHg(- 1)). When IFS was applied, both groups showed, at any level of end-tid al CO2 pressure, an increase in ventilation due to an increase in tida l volume (VT) associated with a decrease in occlusion pressure (P-0.1) . In addition, respiratory parameters ((V) over dotE, VT, P-0.1, inspi ratory flow) were insensitive to CO2 as long as PETCO2 remained below a threshold which was slightly above the eupneic value. However, above this CO2-threshold, no differences in slopes were observed between th e IFS and control conditions in either group, except for a decrease in the P-0.1 slope during IFS in the COPD patients. In conclusion, IFS i nduced similar respiratory changes during CO2 response in stable COPD patients and in normal subjects. Above the eupneic value, LPS did not change the slope of the ventilatory response to CO2. (C) 1997 Elsevier Science B.V.