Dear Editor,

We would like to thank Lindley and Mickleborough for their comments on our paper (1) recently published in the Thorax journal. We agree that eucapnic voluntary hyperventilation (EVH) challenges provide greater sensitivity when compared with exercise challenges in the diagnosis of EIA in elite athletes and have recently published data supporting this hypothesis (2). Despite the greater sensitivity provided by EVH, the criteria an athlete must meet to use inhaled Beta-2-agonists in Olympic competition is a 10% fall from baseline in FEV1 after either an exercise or EVH challenge (3). Accordingly the aim of our paper was to compare the parameters FEF50 and FEV1 rather than examine the sensitivity of EVH and exercise challenges. Irrespective of the challenge employed (EVH, exercise or direct) FEF50 and FEV1 should respond in a similar manor and therefore data from both challenges can be used in sensitivity and specificity analysis.

We agree with Lindley and Mickleborough that laboratory exercise challenges should be conducted with inhaled dry air at an intensity of near maximal exercise. However, the relative high cost and logistical limitations with dry air inhalation preclude its use in many situations with elite athletes. In our study we thought it more appropriate to use an exercise challenge that was more sports specific to each individual athlete and therefore none of our exercise challenges were conducted in the laboratory. Furthermore, in the methods section of our paper we state the intensity of our exercise challenge was at >85% of maximal heart rate. This was only a guideline for athletes during these challenges and in most cases this athletes achieved an exercise intensity that was closer to 95% maximal heart rate by the end of the challenge.

In conclusion we feel FEF50 and FEV1 respond in a similar manor following both exercise and EVH, which means data from both challenges can be involved in our analysis. We agree that dry air inhalation exercise challenges will provide a more sensitive test for EIA, however due to challenge specificity and logistical constraints sports specific exercisechallenges were employed in our study.

Yours Sincerely

John Dickinson

References

1. Dickinson, J., Whyte, G., McConnell, A., Nevill, A. and Harries. The role of Mid-expiratory flow in the diagnosis of exercise induced asthma in elite athletes. Thorax 2006; 61: 111-114

2. Dickinson, J., Whyte, G., McConnell, A. and Harries, M. Screening elite winter athletes for exercise-induced asthma: a comparison of three challenge methods. Brit J Sports Med 2006; 40: 179-183

3. Medical Commision of the International Olympic Committee. IOC’s Medical Code. Lusanne: International Olympic Committee; 2002.

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.