Calculated versus Measured MVV-Surrogate Marker of Ventilatory Capacity in Pediatric CPET.

INTRODUCTION: Maximum voluntary ventilation (MVV), a surrogate marker of maximum ventilatory capacity, allows for measuring ventilatory reserve during cardiopulmonary exercise testing (CPET), which is necessary to assess ventilatory limitation. MVV can be measured directly during a patient maneuver or indirectly by calculating from forced expiratory volume in 1 s (FEV1 × 40). We investigated for a potential difference between calculated MVV and measured MVV in pediatric subjects, and which better represents maximum ventilatory capacity during CPET.

METHODS: Data were collected retrospectively from CPET conducted in pediatric subjects for exercise-induced dyspnea from January 2014 to June 2015 at Akron Children's Hospital. Subjects with neuromuscular weakness, morbid obesity, and suboptimal effort during the testing were excluded from the study.

RESULTS: Thirty-five subjects (mean ± SD, age = 13.8 ± 2.7 yr, range = 7-18 yr) fulfilled the criteria. Measured MVV was significantly lower than calculated MVV (89.9 ± 26.4 vs 122.4 ± 34.5 L·min; P < 0.01). The ventilatory reserve based on measured MVV was also significantly lower than ventilatory reserve based on calculated MVV (12.4% ± 19.6% vs 36.1% ± 13.2%; P < 0.01). Calculated MVV (as well as ventilatory reserve based on calculated MVV) was significantly correlated with ventilatory parameters. By contrast, no significant correlations were found between measured MVV (or ventilatory reserve based on measured MVV) and ventilatory parameters except for peak ventilation (peak V˙E).

CONCLUSIONS: The measured MVV was significantly lower than the calculated MVV in our pediatric subjects. The calculated MVV was a better surrogate of maximum ventilatory capacity as shown by significant correlation to other ventilatory parameters during CPET.