The aim of this study was to compare the 6-min walk test against the recently developed 3-min step test, as measures of exercise tolerance in children with moderate to severe cystic fibrosis (CF) lung disease referred for lung transplantation assessment.Twenty-eight children with CF (16 girls, 12 boys), with a mean age of 13.7 yrs (range 7.2–17.8 yrs) and mean forced expiratory volume in one second of 34% predicted (range 17%–67%) were recruited. All subjects performed both the 6-min walk and 3-min step-tests. Outcome measures were maximum rise in heart rate (HR), and maximum fall in arterial oxygen saturation (Sa,O2).There was no significant difference in resting HR orSa,O2prior to starting the two tests. Both step and walk tests produced significant rises in median HR (from 114–149 min−1, p<0.0005, and 119–138 min−1, p<0.0005, respectively) and significant falls inSa,O2(both from 94–92%, p<0.0005). The step test produced a significantly greater percentage rise in HR (30%versus18%, p<0.0005) and a significantly greater percentage fall inSa,O2(4%versus2%, p=0.002). Bland-Altman analysis gave wide 95% limits of agreement (10.7–29.3% for rise in HR, −2.1–4.6% for fall inSa,O2). The step test was well tolerated.The 3-min step test produced a greater fall inSa,O2and a greater rise in HR than the 6-min walk test in children with moderate to severe CF lung disease. It may be of value when assessing a child's suitability for lung transplantation.
Using a flow of 50 ml/s, FENO increases following admission for IV antibiotic treatment in children with CF but does not correlate with lung function. It is not a useful marker of lung diseases in CF, which has implications for clinical practice.
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