Validity of the oxygen uptake efficiency slope in children with cystic fibrosis and mild-to-moderate airflow obstruction.

PURPOSE: The oxygen uptake efficiency slope (OUES) has been proposed as an 'effort-independent' measure of cardiopulmonary exercise capacity, which could be used as an alternative measurement for peak oxygen uptake (VO(2peak)) in populations unable or unwilling to perform maximal exercise. The aim of the current study was to investigate the validity of the OUES in children with cystic fibrosis (CF). METHODS: Exercise data of 22 children with CF and mild to moderate airflow obstruction were analyzed and compared with exercise data of 22 healthy children. The OUES was calculated using data up to three different relative exercise intensities, namely 50%, 75%, and 100% of the total exercise duration, and normalized for body surface area (BSA). RESULTS: Only the OUES/BSA using the first 50% of the total exercise duration was significantly different between the groups. OUES/BSA values determined at different exercise intensities differed significantly within patients with CF and correlated only moderately with VO(2peak) and the ventilatory threshold. CONCLUSION: The OUES is not a valid submaximal measure of cardiopulmonary exercise capacity in children with mild to moderate CF, due to its limited distinguishing properties, its nonlinearity throughout progressive exercise, and its moderate correlation with VO(2peak) and the ventilatory threshold.

Reference ranges for interrupter resistance technique: the Asthma UK Initiative.

Measuring interrupter resistance (R(int)) is an increasingly popular lung function technique and especially suitable for preschool children because it is simple, quick and requires only passive cooperation. A European Respiratory Society (ERS)/American Thoracic Society (ATS) Task Force recently published empirical recommendations related to procedures, limitations and interpretation of the technique. However, for valid interpretation, high-quality reference equations are required and these have been lacking. The aim of the present study was to collate R(int) data from healthy children in order to produce more robust reference equations. A further aim was to examine the influence of methodological differences on predicted R(int) values. R(int) data from healthy children were collected from published and unpublished sources. Reference equations for expiratory and inspiratory R(int) were developed using the LMS (lambda, mu, sigma) method. Data from 1,090 children (51% males) aged 3-13 yrs were collated to construct sex-specific reference equations for expiratory R(int) and data from 629 children (51% males) were collated for inspiratory R(int). Height was the best independent predictor of both expiratory and inspiratory R(int). Differences between centres were clinically irrelevant, and differences between ethnic groups could not be examined. The availability of a large and generalisable sample and the use of modern statistical techniques enabled the development of more appropriate reference equations for R(int) in young children.