Need for population specific validation of a portable metabolic testing system: a case of sedentary pregnant women.

Commercially available portable metabolic systems have been validated with samples of young, healthy, and well-fit subjects, but use of these systems with a special population, such as healthy but sedentary pregnant women, requires a unique set of considerations. These include a woman's limited testing time necessary for fetal safety, relatively low oxygen consumption, and the unique physiology of pregnancy (woman, the placenta, and the fetus). The purpose of this study was to validate a portable metabolic testing system (VO2000) with healthy sedentary pregnant women. A total of 9 sedentary pregnant women who averaged 30 years of age (SD=3), 93 kg (SD=19) weight, 163 cm (SD=7) height, and at 19 weeks' gestation (SD=5) volunteered to participate. Submaximum fitness tests using the Cornell protocol were conducted once with two systems (VO2000 and CPX/D, a reference) simultaneously, and then subsequently twice with one system (VO2000). The VO2000 consistently overestimated VO2 measurement, compared to the same manufacturer's reference system, by 4.4 +/- 3.6 (SD) ml/kg/min, and when VO2000 was used twice, the mean difference was statistically significant (1.0 +/- 1.8 [SD] ml/kg/min; t(45) = 3.9, p < .001). The results of the study show that although VO2000 is an established and validated portable metabolic system for measurement on adult males and females who are relatively well fit, this portable system consistently overestimates VO2 readings for pregnant women compared to standard full-size system. Measurements, when repeated, were not consistent.