Ghoos Y, Rutgeerts P, Vantrappen G, Hiele M
Department of Medicine, UZ St Rafaël-Gasthuisberg, Leuven, Belgium.
Biomed Environ Mass Spectrom. 1988 Apr 15;15(8):447-51. doi: 10.1002/bms.1200150806.
A new method was developed and validated for measuring the CO2 concentration in the breath by mass spectrometric analysis. Argon, an inert gas that is present in air in a constant concentration of 0.923%, was used as an internal standard. By determining the ratio of CO2 (mass 44) to Ar (mass 40) in a breath sample, it was possible to read the CO2 concentration from a standard curve, relating CO2 concentration to CO2: Ar ratio. By combining mass spectrometric determination of CO2 concentration in breath with spirometric measurement of expired volumes, the CO2 production was determined in 67 subjects at rest. The mean value was 8.86 mmol kg-1 h-1, but there was considerable interindividual variation. This new method was applied to glucose oxidation studies in 10 normal subjects, 10 post-gastrectomy patients and 7 obese type II diabetic subjects. Measurement of the 13CO2 exhalation with quantitative determination of CO2 production allowed more accurate determination of the CO2 excretion rate in relation to blood levels of glucose, insulin and free fatty acids than assuming the constant CO2 production of 300 mmol unit body surface -1 h-1 or 9 mmol kg-1 h-1. It also resulted in a better discrimination between normal subjects and diabetics.
开发并验证了一种通过质谱分析测量呼出气体中二氧化碳浓度的新方法。氩气是一种惰性气体，在空气中的浓度恒定为0.923%，用作内标。通过测定呼出气体样本中二氧化碳（质量数44）与氩气（质量数40）的比例，可以从标准曲线读取二氧化碳浓度，该标准曲线将二氧化碳浓度与二氧化碳：氩气比例相关联。通过将呼出气体中二氧化碳浓度的质谱测定与呼出气体量的肺量计测量相结合，测定了67名静息受试者的二氧化碳产生量。平均值为8.86 mmol kg-1 h-1，但个体间存在相当大的差异。将这种新方法应用于10名正常受试者、10名胃切除术后患者和7名肥胖II型糖尿病受试者的葡萄糖氧化研究。与假设二氧化碳产生量恒定为300 mmol单位体表面积-1 h-1或9 mmol kg-1 h-1相比，通过测量13CO2呼出量并定量测定二氧化碳产生量，可以更准确地确定与血糖、胰岛素和游离脂肪酸血水平相关的二氧化碳排泄率。这也使得正常受试者和糖尿病患者之间的区分更加明显。
