The spirometry measures Forced Expired Volume in 1 Second (FEV 1 ) and Forced Vital Capacity (FVC), both in percent predicted, decreased from Exacerbation Levels I to II (p < 0.017) but remained unchanged from Levels II to III ( Figure 1A and 1C, respectively). However, when Levels II and III were combined to create an 'in-patient' category for each of these variables, there was a statistically signifi-Respiratory Research 2006, 7:74 http://respiratory-research.com/content/7/1/74 cant decrease for the in-patients versus the out-patients (p < 0.05) ( Figure 1B and 1D, respectively). We also observed the same trend for FEV 1 /FVC (Figure 2A and 2B ). For all other spirometry measures, there were too few studies available in Level III for meta-analysis.