Background: Cystic fibrosis (CF) patients experience pulmonary exacerbations and the three-minute step test (3-min step test) may be a simple and easy-to-perform functional test to help identify such episodes. The present study aimed to evaluate the association of the 3-min step test with the occurrence of pulmonary exacerbations in children with CF.
Methods: Cross-sectional study of CF patients aged 6 years and older. Pulmonary exacerbations were assessed using both the Fuchs criteria and the Kanga Score. The 3-min step test was performed using a 15 cm-high step and heart rate (HR), oxygen saturation (SpO<inf>2</inf>), and dyspnea were measured before and after the test. Correlations between the test and the scores, as well as comparisons between patients experiencing or not an exacerbation, were performed.
Results: Sixty-two patients (11.1±4.3 years) were included. Both the Fuchs criteria and the Kanga score correlated significantly with age, forced expiratory volume in the first second (FEV<inf>1</inf>), final SpO<inf>2</inf>, and 1-min recovery SpO<inf>2</inf>. A fall greater than 4% in the final SpO<inf>2</inf> was significantly associated with the presence of a pulmonary exacerbation, considering both Fuchs and Kanga criteria. Age, resting HR, and HR after 1-min recovery were significantly higher, while FEV<inf>1</inf>, SpO<inf>2</inf> at rest, final SpO<inf>2</inf>, and SpO<inf>2</inf> after 1-min recovery were significantly lower in patients classified as exacerbated.
Conclusions: Physiological responses to the 3-min step test are associated with the occurrence of pulmonary exacerbation in children with CF. Desaturation at the end of the test or during 1-min recovery may be the best variable to monitor.