Validation of a Simplified, Portable Cardiopulmonary Gas ExchangeSystem for Submaximal Exercise Testing

摘要

Shape Medical Systems, Inc. has developed a new miniaturized, simplified system for non-invasivecardiopulmonary gas exchange quantification and has targeted their system for submaximal clinical exercise testing inorder to abbreviate testing in an expanding clinical market during a climate of escalating health care costs. The focus ofthe present study was to compare this new device to a validated, standardized system for measures of cardiopulmonarygas exchange. Eighteen healthy adults (10 male/8 female, age 29±7 yr, BMI 23.8±2.4 kg/m2) were brought to thelaboratory and instrumented with both measurement systems via in-series pneumotachs. Additionally, the Shape systemincluded a pulse oximeter for heart rate (HR) and oxygen saturation (SaO2), while the standard system included separate12-lead ECG and oximetry devices. The protocol included 2-min resting breathing, followed by 3-min at each of 3workloads (50, 70, 125 watts) on a cycle ergometer. Data were collected breath-by-breath and averaged the last 30-sec ofeach workload. After a 15-min rest period, the pneumotach order was reversed and the study repeated. Since gas exchangedata were similar (p>0.05) within a given metabolic testing system between sessions the data were pooled for comparingthe Shape and Standard systems. There were no differences (p>0.05) between the systems for oxygen consumption-VO2,carbon dioxide production-VCO2, ventilation-VE, end tidal CO2-PetCO2, tidal volume-VT, respiratory rate-fb, and HR atrest or any work load. SaO2 was slightly, but significantly lower using the Shape embedded oximeter (p<0.05, averaging~1% across workloads). There were significant correlation coefficients (p<0.001) between the systems for VO2 (r=0.991),VCO2 (r=0.986), VE (r=0.995) and PetCO2 (r=0.953). Bland Altman plots indicated good agreement between systems forthe same gas exchange measures, independent of workload. The Shape system was sensitive to small increases in work(50 to 70 watts) and there were no differences in gas exchange measures in a subgroup of subjects (n=4) using a tightfitting mask instead of a mouthpiece (p>0.05). These data suggest that the new, simplified metabolic system developed byShape Medical Systems, Inc. accurately quantifies key cardiopulmonary variables over a range of workloads, has acoefficient of variation similar to a well validated system and can be used with mouthpiece or mask.