TY - JOUR T1 - Does carbon dioxide retention during exercise predict a more rapid decline in FEV<sub>1</sub> in cystic fibrosis? JF - Archives of Disease in Childhood JO - Arch Dis Child SP - 792 LP - 795 DO - 10.1136/adc.2004.070110 VL - 90 IS - 8 AU - S M Javadpour AU - H Selvadurai AU - D L Wilkes AU - J Schneiderman-Walker AU - A L Coates Y1 - 2005/08/01 UR - http://adc.bmj.com/content/90/8/792.abstract N2 - Background: Carbon dioxide (CO2) retention during exercise is uncommon in mild to moderate lung disease in cystic fibrosis (CF). The ability to deal with increased CO2 is dependent on the degree of airflow limitation and inherent CO2 sensitivity. CO2 retention (CO2R) can be defined as a rise in PETCO2 tension of ⩾5 mm Hg with exercise together with a failure to reduce PETCO2 tension after peak work by at least 3 mm Hg by the termination of exercise. Aim: To ascertain if carbon dioxide retention during exercise is associated with more rapid decline in lung function. Methods: Annual spirometric and exercise data from 58 children aged 11–15 years, with moderate CF lung disease between 1996 and 2002 were analysed. Results: The mean FEV1 at baseline for the two groups was similar; the CO2R group (n = 15) was 62% and the non-CO2 retention group (CO2NR) was 64% (n = 43). The decline in FEV1 after 12 months was −3.2% (SD 1.1) in the CO2R group and −2.3% (SD 0.9) in the CO2NR group. The decline after 24 months was −6.3% (SD 1.3) and −1.8% (SD 1.1) respectively. After 36 months, the decline in FEV1 was −5.3% (SD 1.2) and −2.6% (SD 1.1) respectively. The overall decline in lung function was 14.8% (SD 2.1) in the CO2R group and 6.7% (SD 1.8) in the CO2NR group. Using the primary outcome measure as a decline in FEV1 of &gt;9%, final multivariate analysis showed that the relative risks for this model were (95% CIs in parentheses): ΔPETCO2 11.61 (3.41 to 24.12), peak V˙O2 1.23 (1.10 to 1.43), and initial FEV1 1.14 (1.02 to 1.28). Conclusion: Results show that the inability to defend carbon dioxide during exercise is associated with a more rapid decline in lung function. ER -