TY - JOUR T1 - DL,no; slave to a rhythm? JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p1217 AU - Antoinette Houtkooper AU - P.J.A.M. van Ooij AU - R.A. van Hulst Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p1217.abstract N2 - Background: It is generally accepted that spirometry and diffusing capacity are subjected to a diurnal rhythm (CINKOTAI 1966, BORSBOOM 1999, MEDAROV 2008). Values for VC, for example, are lowest around noon and highest between 3.00 and 4.00 pm (MEDAROV 2008,) while DL,co is highest between 08.00 and 09.00 am and decreases during the day (CINKOTAI 1966, MEDAROV 2008).Introduction: The aim of this study was to investigate the diurnal rhythm for DL,no. The DL,no is a relatively new method and for applying in studies it is important to know whether there is a diurnal rhythm or not.Methods: Eleven male subjects were measured between 8 am and 10 pm. In this period DL,no was measured six times using a Masterscreen PFT-Pro (CareFusion), each time with a pause of at least two hours (max 4 hours).Statistics: The Shapiro-Wilk test was used to test for normality. To determine diurnal variance, within-day variations were tested using the one-way Analysis of Variance (Anova). The Bonferroni correction was used to account for multiple comparisons. However, as diurnal variations can be curve shaped we also tested this index with a fractional polynomial regression model.Results: The Anova test with Bonferroni correction showed no significant diurnal variation in DL,no (p=0.854). Also the fractional polynomial regression model to the 4th degree or lower did not show any significant relationship between time of the day and DL,no (p=0.526).Conclusion: In our study DL,no does not have a diurnal rhythm. We would like to expand our group of subjects to confirm this statement. Further investigation is therefore necessary. ER -