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In teenagers, the Nuss procedure for pectus excavatum (PEx) repair has the potential to improve lung function and normalize aerobic performance during incremental exercise testing. In a cohort of 70 adults, we have previously observed that aerobic capacity significantly improved one year after the Ravitch-type procedure . In sharp contrast, Udholm et al. failed to demonstrate such improvements at the one-year follow-up in 15 adults undergoing the Nuss procedure . Whether these contrasting results rely on different surgical approaches will be answered in the future by the 3-year follow-up proposed by Udholm et al. Meanwhile, interesting methodological issues mentioned by Udholm et al. deserve additional comments.
First, Udholm et al. observed increases in postoperative peak VO2 that were consistent with our previous reports [1,3]. Study by Ulholm et al. was underpowered, precluding any definite conclusion. Surprisingly, exercise testing was performed using a 30 Watt-increment to progressively increase workload. Of note, although VO2 is linearly related to workload, high workload increments require sufficient time for VO2 to increase as well. This time delay can induce an oxygen debt limiting peak VO2 at the latest exercise steps. Absence of difference between pre- and postoperative peak VO2 in Udholm et al.'s study may be related, at least in part, to blunted VO2 kinetics. In order to limit confounding effects of reduced VO2 kinetics, determination of VO2 at ventilatory threshold and oxygen uptake efficiency slope may be useful to better characterize cardiopulmonary functional reserve in the context of symptom-limited submaximal exercise.
Secondly, authors claimed that exercise habit was similar before and after surgical correction. Exercise habits were evaluated with scoring system for categories, comparisons of which should be analysed using the Chi-2 trend rather than comparisons of means. Expression of postoperative VO2 changes according to individual fitness category could be informative as well. As suggested by Ulholm et al., changes in exercise habit may be considered a confounding effect of PEx repair on postoperative peak VO2. Alternatively, it can be considered an expected result of PEx repair. In our series, some well-trained patients who maintained their intensive training after surgery did actually demonstrate increased peak VO2. Here, PEx repair can be the main cause of aerobic capacity improvement. Other patients intensified their training after surgery. Here, aerobic capacity increases may be a confounding factor for peak VO2 change analysis, but may be also viewed as an expected result of PEx repair that has improved patients' self-image and his motivation for social activities, including sports. Hence, beneficial impact of PEx repair on aerobic capacity may be related to direct improvement of cardiopulmonary response to exercise and through postoperative increases in exercise training, which will improve patient's quality of life and reduce risk of premature mortality.
Overall, Udholm et al. have provided useful information on the 1-year follow-up after Nuss procedure in patients with PEx regarding changes in aerobic capacity. We feel that a standardized exercise testing protocol represents the most important issue that will allow study comparisons for evaluation of different procedures for PEx repair in adults.
Conflict of interest: none declared.