EURO PEAN SOCI ETY OF CARDIOLOGY ® Original scientific paper The oxygen uptake efficiency slope in children with congenital heart disease: construct and group validity BC Bongers 1 , HJ Hulzebos 1 , AC Blank 2 , M van Brussel 1 and T Takken 1 Abstract Objective: The oxygen uptake efficiency slope (OUES) has been proposed as an independent and objective alternative to the peak oxygen uptake (VO 2peak ), which does not require maximal exercise. The aim of this study was to investigate the construct and group validity of the OUES in children with congenital heart disease (CHD). Methods: Thirty-one patients with CHD, of which 16 patients (mean age  SD 11.2  2.7 years) with a Fontan repair and 15 patients (mean age  SD 13.2  3.6 years) with surgical repair of tetralogy of Fallot (ToF) completed a symptom-limited cardiopulmonary exercise test. The OUES was calculated and normalized for body surface area at three different exercise intensities: (1) using 100% of the exercise data; (2) using the first 75% of the exercise data; and (3) using exercise data up to the ventilatory threshold (VT). Furthermore, peak oxygen uptake (VO 2peak ), VT, ventilatory efficiency (V E /VO 2 -slope), and ventila- tory drive (V E /VCO 2 -slope) were calculated and compared with values of 46 healthy children (mean age  SD 12.2  2.4 years). Results: In all three groups, the OUES values determined at the three different exercise intensities were not significantly different from each other. Moreover, the OUES was significantly reduced in the children with CHD, with significantly lower values in the Fontan patients compared to ToF. Strong correlations were found between the OUES and both the VO 2peak and VT in Fontan and ToF patients. Discussion: The OUES provides a valid measure of cardiopulmonary fitness in children with CHD, which is independent of exercise intensity and strongly correlated with VO 2peak and VT (construct validity). Furthermore, the OUES is capable of differentiating between healthy children and children with CHD and between Fontan and ToF patients (group validity). Therefore, the OUES may be a valid, effort-independent parameter of cardiopulmonary fitness in children with CHD. Keywords Oxygen uptake efficiency slope, congenital heart disease, exercise testing, children Received 10 May 2010; accepted 3 August 2010 Introduction The importance of cardiopulmonary exercise testing (CPET) is becoming more accepted in clinical practice. The results of CPET can be used at all stages of clinical assessment (e.g. diagnosis and characterization of dis- ease severity, progression, prognosis, and response to treatment). 1,2 In children with congenital heart disease (CHD), the main indication for CPET is the evaluation of aerobic capacity. 3 Since cardiopulmonary function testing at rest cannot predict an individual’s aerobic capacity reliably, 4 the measurement of the maximal oxygen uptake (VO 2max ) during CPET is currently the only modality that provides an accurate and objective indication of (maximal) aerobic capacity. Classically, the VO 2max describes a point at which there is no further increase in oxygen uptake (VO 2 ), despite further increases in exercise intensity. 5 Unfortunately, the VO 2max cannot be measured directly in individuals who are unable or unwilling to perform 1 Child Development and Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands. 2 Department of Pediatric Cardiology, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands. Corresponding author: Tim Takken, Child Development and Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, KB.02.056.0, P.O. Box 85090, 3508 AB Utrecht, The Netherlands Email: t.takken@umcutrecht.nl European Journal of Cardiovascular Prevention & Rehabilitation 18(3) 384–392 ! The European Society of Cardiology 2011 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1741826710389390 ejcpr.sagepub.com Downloaded from https://academic.oup.com/eurjpc/article/18/3/384/5931549 by guest on 28 February 2023