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Ventilatory and Cardiovascular Responses to Exercise in Patients With Pectus Excavatum^*

^* From the Departments of Medicine and Physiology (Dr. Cooper), the Exercise Physiology Research Laboratory (Mr. Malek), and the Division of Pediatric Surgery (Dr. Fonkalsrud), Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA.

Correspondence to: Christopher B. Cooper, MD, FCCP, Professor of Medicine and Physiology, Exercise Physiology Research Laboratory, David Geffen School of Medicine at UCLA, 10833 Le Conte Ave, 37-131 CHS, Los Angeles, CA 90095; e-mail: ccooper{at}mednet.ucla.edu

Purpose: Uncertainty exists as to whether pectus excavatum causes true physiologic impairments to exercise performance as opposed to lack of fitness due to reluctance to exercise. The purpose of this study was to examine the effect of pectus excavatum on ventilatory and cardiovascular responses to incremental exercise in physically active patients.

Methods: Twenty-one patients with pectus excavatum (age range, 13 to 50 years; mean [± SD] age, 23.6 ± 8.9 years; severity index range, 3.7 to 8.0; mean severity index, 5.1 ± 1.2) were referred for preoperative evaluation. Eighteen of the patients (85%) had a history of performing aerobic activity ranging from 30 min to 2 h per day (mean duration, 1.0 ± 0.61 h per day) for 3 ± 1.5 days per week. Patients performed pulmonary function tests, and submaximal and maximal incremental exercise testing.

Results: On maximal exercise testing, the maximum oxygen uptake (O₂max), and oxygen-pulse were significantly lower than the reference values (t₂₀ = 6.17 [p < 0.0001] and t₂₀ = 4.52 [p < 0.0001], respectively). Furthermore, patients exhibited cardiovascular limitation, but not ventilatory limitation. Despite their high level of habitual exercise activity, the overall metabolic threshold for lactate accumulation was abnormally low (ie, 41% of the reference value for O₂max) especially in those with a pectus severity index (PSI) of > 4.0 (39% of the reference value of O₂max), which is consistent with cardiovascular impairment rather than physical deconditioning. Patients with a PSI of > 4.0 were also eight times more likely to have reduced aerobic capacity than patients who had a low severity index, despite their level of exercise participation. On submaximal testing, we found that the time constant for O₂ uptake kinetics was 37.4 s for the on-transit and 41.6 s for the off-transit. The observed values for FVC, FEV₁, maximum voluntary ventilation, and diffusing capacity of the lung for carbon monoxide were significantly lower than reference values, but those for total lung capacity and residual volume were not significantly lower than reference values.

Conclusions: The information derived from this study supports the opinion that pectus excavatum is associated with true physiologic impairment and reduced exercise capacity, predominantly due to impaired cardiovascular performance rather than ventilatory limitation. Furthermore, the impairment is not explained by physical deconditioning.

Key Words: aerobic fitness • cardiovascular disease • chest wall deformity • clinical exercise physiology • exercise testing • maximum oxygen uptake • oxygen uptake kinetics • pectus excavatum

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