Dear Editor,

We read with great interest the article published in Thorax by Dickinson et al (February 2006)(1) investigating the response of FEF50 following EVH (Eucapnic voluntary hyperventilation) or exercise challenges in elite athletes as an adjunct to FEV1.0. We were however, slightly confused as to the research design selected by the researchers. It appears from the stated methods that the researchers used either an EVH challenge or an exercise challenge for EIB diagnosis in their elite athletes. If this is indeed the case then the underlying assumption is, that the exercise challenge test selected by the authors is not different in its impact upon pulmonary function than the EVH challenge test. As the authors do not present this data in their paper then it is impossible for us to know if the data from different challenge tests can be pooled to provide a single sample. Indeed in a recent publication from the same authors (2) their contention is that EVH and exercise tests do not give identical results and that they should not be used synonymously.

In addition, we were concerned about the authors selection of the ATS (3) guidelines as the basis for their use of 85% of maximal heart rate as an exercise intensity for the exercise challenge test. The ATS guidelines clearly indicate that cold dry air should be used during an exercise test and that the test should “produce 4-6 minutes of exercise at near maximal targets”(3). On the basis the subjects being tested were ‘current or potential Olympic competitive standard’ we would have recommended using an exercise challenge that stressed the elite athletes closer to their maximal capabilities (4). It is well documented (5) that elite endurance athletes can exhibit adaptations to their physiology that allow them to exercise at higher intensities for longer durations and so it is possible that these Olympic caliber athletes were not ventilating at a sufficient level to exhibit symptoms of EIB during the exercise challenge(6). It has been shown previously, in young asthmatic patients, that exercise load is of paramount importance when exercise challenge testing for EIB (due to the level of ventilation) (7). The difference between 85% and 95% predicted maximal heart rate had a 60% difference in terms of EIB diagnosis (7).

Therefore, as suggested in our communication to the editor of BJSM and the authors of the current paper (8), the levels of ventilation reached during each test would be extremely useful in comparing exercise and EVH challenge tests. This would allow a further examination of the data presented by the authors and the removal of the different tests as extraneous variables when discussing the negative and positive diagnosis of EIB based upon pulmonary function.

References

1 Dickinson, J.W., Whyte, G.P., McConnell, A.K., Nevill, A.M. and Harries, M.G. Mid-expiratory flow versus FEV1 measurements in the diagnosis of exercise induced asthma in elite athletes. Thorax 2006; 61: 111-114.

2 Dickinson, J.W., Whyte, G.P., McConnell, A.K., Harries, M.G. and Rundell, K.W. Screening elite winter athletes for exercise induced asthma: a comparison of three challenge methods. Commentary. British Journal of Sports Medicine., February 2006; 40: 179 - 182.

3 American Thoracic Society. Guidelines for Methacholine and Exercise Challenge Testing – 1999.American Journal of Respiratory and Critical Care Medicine 2000; 161: 309-329.

4 Mickleborough TD, Murray RL, Ionescu AA, Lindley MR. Fish oil supplementation reduces severity of exercise-induced bronchoconstriction in elite athletes. American Journal of Respiratory and Critical Care Medicine 2003; 168: 1181-1189.

5 Jones, A.M. and Carter, H. The effect of endurance training on parameters of aerobic fitness. Sports Medicine. 2000 June, Vol 29 Issue (6) 373-386.

6 Anderson SD, Holzer K. Exercise-induced asthma: is it the right diagnosis in elite athletes? J Allergy Clin Immunol 2000; 106: 419-428.

7 Carlsen, K.H., Engh, G. and Mork, M. Respiratory Medicine. 2000 Aug, Vol 94, Issue(8):pages750-5.

8 Lindley, M.R. and Mickleborough, T.D. Exercise challenge testing of elite winter athletes for exercise-induced asthma. British Journal of Sports Medicine. Published on 13 February 2006. http://bjsm.bmjjournals.com/cgi/eletters/40/2/179.