[Determination of Hypercapnic Ventilatory Response in COPD Patients]

Previous studies showed a reduced hypercapnic ventilatory response (HCVR) in patients with COPD. However, the association between HCVR and COPD GOLD stages is unknown. The measurement of the HCVR is a methodological option to test the function of the breathing feedback cycle. The aim of this feasibility study was to present a new automatic and standardized device (MATAM) to measure and interpret the HCVR. This device determines if exposure to CO2 leads to an adequate increase in breathing frequency and tidal volume. Recordings are performed in a closed system that allows selective changes of each gas component. The minute ventilation (AMV) under hypercapnic stimulation is plotted against the end-tidal CO2 (ETCO2). The HCVR is defined as the linear regression line.28 patients (18 male; 10 female) with COPD GOLD stages 0 to IV were studied. The patients had a mean age of 57 ± 14 (standard deviation) years and a mean BMI of 32 ± 9 kg/m(2). We could show that the HCVR measurement in patients with COPD using MATAM was feasible. Patients with more severe COPD stages had a significantly more reduced HCVR. This could be an indication of reduced chemosensitivity due to a worsening of blood values (pH and pCO2) which affect the central chemoreceptors in the long term. Further studies will be needed to validate the MATAM device for healthy individuals and other patient groups, and for the investigation of standard values.