Comparing four non-invasive methods to determine the ventilatory anaerobic threshold during cardiopulmonary exercise testing in children with congenital heart or lung disease Naomi. C. A. Visschers 1 , Erik. H. Hulzebos 1 , Marco. van Brussel 1 and Tim. Takken 1,2 1 Child Development & Exercise Centre, Wilhelmina Children’s Hospital, University Medical Center Utrecht, and 2 Partner of Shared Utrecht Pediatric Exercise Research (SUPER) Lab, Utrecht, The Netherlands Summary Correspondence Tim Takken, Science, Child Development and Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Room KB2.056.0, PO Box 85090, NL 3508 AB Utr- echt, The Netherlands E-mail: t.takken@umcutrecht.nl Accepted for publication Received 19 February 2014; accepted 1 July 2014 Key words anaerobic threshold; child; congenitally corrected transposition of the great arteries; cystic fibrosis; exercise test Background The ventilatory anaerobic threshold (VAT) is an important method to assess the aerobic fitness in patients with cardiopulmonary disease. Several meth- ods exist to determine the VAT; however, there is no consensus which of these methods is the most accurate. Objective To compare four different non-invasive methods for the determination of the VAT via respiratory gas exchange analysis during a cardiopulmonary exercise test (CPET). A secondary objective is to determine the interobserver reliability of the VAT. Methods CPET data of 30 children diagnosed with either cystic fibrosis (CF; N = 15) or with a surgically corrected dextro-transposition of the great arteries (asoTGA; N = 15) were included. Results No significant differences were found between conditions or among testers. The RER = 1 method differed the most compared to the other methods, showing significant higher results in all six variables. The PET-O 2 method differed signifi- cantly on five of six and four of six exercise variables with the V-slope method and the VentEq method, respectively. The V-slope and the VentEq method dif- fered significantly on one of six exercise variables. Ten of thirteen ICCs that were >0Á80 had a 95% CI > 0Á70. The RER = 1 method and the V-slope method had the highest number of significant ICCs and 95% CIs. Conclusion The V-slope method, the ventilatory equivalent method and the PET-O 2 method are comparable and reliable methods to determine the VAT during CPET in children with CF or asoTGA. Introduction Aerobic fitness is one of the most relevant prognostic factors for morbidity and mortality in patients with pulmonary or cardiac diseases, such as cystic fibrosis or congenital heart dis- eases (Nixon et al., 1992; Giardini et al., 2007, 2009; Inuzuka et al., 2012; Perez et al., 2013; Hulzebos et al., 2014). The maximal oxygen uptake (VO 2max ), the highest rate at which an individual can consume oxygen during exercise, is widely recognized as the golden standard to assess an individual’s level of aerobic fitness (Shephard et al., 1968). Maximal oxy- gen uptake conventionally implies the existence of a VO 2 pla- teau. However, this response is not typical of children and adolescents (Rowland, 1993; Armstrong et al., 1996), and so it has gradually become more common to determine the VO 2peak , being the highest VO 2 elicited during a cardiopulmo- nary exercise test (CPET), to describe the aerobic fitness of children (Fawkner & Armstrong, 2007). Achieving this VO 2 peak, however, requires maximal effort, which might not be attainable for every paediatric patient with a cardiac or pul- monary impairment. Therefore, in these patients, supplemen- tary approaches to determine the level of physical fitness, such as quantifying the ventilatory anaerobic threshold (VAT), are being implemented (Hebestreit et al., 2000). Maintaining and improving a certain level of aerobic fitness (within a frame of reference suitable for cardiopulmonary impaired patients) is a fundamental pillar in the multidisci- plinary treatment of the above mentioned diseases. Therefore, Clin Physiol Funct Imaging (2014) doi: 10.1111/cpf.12183 1 © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd