Abstract: Objective　We analyzed the peak respiratory exchange ratio（RER） data of 102 symptom-limited maximal cardiopulmonary exercise tests（CPETs），in order to provide a reference for the determination of the appropriate RER for the stopping of the tests.Methods　Data concerning 112 CPETs performed with incremental protocols by 85 participants were collected from the Principles of Exercise Testing and Interpretation （Fourth Edition）．After the exclusion of 10 CPETs without RER because of inhaling pure oxygen，we analyzed RER related data of 102 CPETs.For CPETs with peak RER ≥1.10，1.15 and 1.20，we calculated and compared the differences of exercise duration，work rate （WR），systolic blood pressure（SBP），heart rate（HR），breath frequency（f），minute ventilation（V?E），carbon dioxide output（V?CO2），oxygen uptake（V?O2），oxygen pulse（O2P） and RER at the peak exercise and while the RER≥1.10，1.15 and 1.20 on the same CPET，using the paired-t test.Results　The mean peak RER of 102 CPETs was （1.21±0.16）（range：0.86-1.77）．Even though there were about one half to more than three quaters of CPETs with peak RER ≥1.10，1.15 and 1.20，there still were 7 CPETs with peak RER <1.0.For 77 CPETs with peak RER ≥1.10，there were significant differences for the parameters of exercise duration，WR，HR，f，V?E，V?CO2，V?O2 ，O2P and RER（P<0.05）．For 60 CPETs with peak RER ≥1.15，there were significant differences for the parameters of exercise duration，WR，HR，f，V?E，V?CO2 and RER（P<0.05）．For 50 CPETs with peak RER ≥1.20，there were significant difference for the parameters of exercise duration，WR，HR，f，V?E and RER（P<0.05）．Conclusion　Although more than half of the CPETs have a peak RER≥1.10，the remaining have a peak RER<1.0.In clinical practice，for ensuring the safety of symptom-limited maximal CPET，close monitoring is emphasized：the overall functional capacity of the patient would be underestimated if his exercise is stopped based on a peak RER reaching a certain level，and the the risk of over exercise would be posed to the patient if the maximal effort is denied based on a peak RER being below a certain level.So a fixed RER can not be used as the absolute predictor of stopping exercise，and we designed a special “Max”testing to identify the CPET as a maximal effort or not.

Key words: Respiratory function tests, Respiratory exchange ratio, Cardiopulmonary exercise testing, Work rate increasing rate, Standard for stopping exercise, Max testing, Saftey and risk

摘要： 目的　对所有症状限制性最大极限心肺运动试验（CPET）的呼吸交换率（RER）相关数据进行再分析，以期探讨CPET中RER为何水平时应该作为终止试验的参考依据。方法　第4版Principles of Exercise Testing and Interpretation一书中收录的85例受试者以标准连续递增功率方案共完成112例次CPET，其中完成RER记录的有102例次。计算并比较同一个CPET中峰值运动时与RER≥1.10、1.15、1.20时的运动时间、功率、收缩压、心率、呼吸频率、分钟通气量、二氧化碳排出量、摄氧量、氧脉搏和RER。结果　102例次CPET的峰值RER〔范围0.86~1.77，（1.21±0.16）〕，其中四分之三至半数CPET的峰值RER≥1.10、1.15和1.20；但同时峰值RER<1.0者也有7例次。峰值RER≥1.10的77例次CPET，其峰值运动时与RER≥1.10时的运动时间、功率、心率、呼吸频率、分钟通气量、二氧化碳排出量、摄氧量、氧脉搏和RER比较，差异有统计学意义（P<0.05）。CPET峰值RER≥1.15者60例次，峰值运动时与RER≥1.15时的运动时间、功率、心率、呼吸频率、分钟通气量、二氧化碳排出量和RER比较，差异有统计学意义（P<0.05）。CPET峰值RER≥1.20者50例次，峰值运动时与RER≥1.20时的运动时间、功率、心率、呼吸频率、分钟通气量和RER比较，差异有统计学意义（P<0.05）。结论　个体化症状限制性最大极限CPET大多数患者峰值RER达到或者超过1.10，但也有很多患者没有达到此值；不能以某特定RER值作为CPET的绝对标准。CPET临床实践中强调严密监护保安全前提下的“症状限制”，既不能以达到特定RER值终止试验，而低估患者整体功能状态；也不能以未达到特定RER值来否定患者CPET的极限运动状态，从而产生过度运动风险的可能，为此本研究提出了Max试验的方法以验证CPET是否为极限运动。

关键词: 呼吸功能试验, 呼吸交换率, 心肺运动试验, 功率递增速率, 终止运动标准, Max试验, 安全与风险