延长呼气法和平静呼气法呼气末二氧化碳监测在慢性阻塞性肺疾病中的比较

Comparing Study of Prolonged Expriation Method and Expiration Method in the Measurement of Expired Gas PCO_2 at end Expiration in COPD Patients

目的:在23例COPD病人中(合并Ⅱ型呼吸衰竭者15例),分别采用平静呼气法和延长呼气法测定PETCO2,探讨两种方法测定PETCO2与PaCO2的关系。方法:采用红外线吸收法,以主气流方式测定慢性阻塞性肺疾病(COPD)病人平静呼气PETCO2[PETCO2(T)]和延长呼气5s时的PETCO2[PETCO2(P)],同步检测PaCO2。随访治疗后PaCO2与PETCO2的变化。结果:平静呼气时PETCO2为50.93±13.35mmHg(6.79±1.78Kpa),PaCO2为59.10±15.53mmHg(7.88±2.07kPa),两者比较有显著差异(P<0.05);延长呼气5s时PETCO2为58.95±14.70(7.86±1.96Kpa),和PaCO2比较无显著差异(P>0.05)。平静呼气及延长呼气PETCO2变异系数分别为5.01±3.09%和5.00±2.58%,两者无显著差异(P>0.05)。治疗后PETCO2的变化可反映的PaCO2变化。结论:COPD病人中,延长呼气法测定PETCO2可预测PaCO2和反映其动态变化,可用于无创监测COPD患者的PaCO2动态变化,具有重要的临床应用价值。

Objective： In order to investigate the possibility of estimating the arterial PCO2 （ PaCO2 ） with the measurement of expired gas PCO2 at end expiration using the prolonged expiration method, end expiration PCO2（PETCO2） was measured with tidal （PETCO2（T）） and prolonged expiration method （PETCO2 （P） ） in COPD patients. Method： 23 severe COPD patients admitted into the hospital because of acute exacerbation were recruited for the study. Expired PCO2 was measured with NOVAMETRIC CO2 monitoring system （ Novametric Co, USA ）. PETCO2 was measured with tidal breathing PETCO2 （ T） and prolonged expiration （ more than 5 seconds ） methods PETCO2 （ P ）, and PaCO2 was measured simultaneously. The relationship between PaCO2, PETCO2 （T） and PrrCO2 （ P ） was analyzed. Follow - up measurements were repeated 7 ～ 8 days later in order to evaluate the relationship between the change in PaCO2, and PETCO2 （P）. Result：The PETCO2 was dynamically related to the expiratory time （ Fig. 1 ） in COPD. PETCO2 at 5 seconds after the start of expiration was read as PETrCO2（P（. The mean difference between PETCO2 （T） and PaCOswas 8.18 ＋ 6. 45mmHg（ 1.09 ±0.86Kpa） （P 〈0.05） ; On the other hand, the mean difference between PETCO2 （ P） and PaCO2 was only 0.15 ± 4.73mmHg （ 0.02 ± 0.63Kpa ） （ P = 0.45 ）. The average PaCO2 was 59.10 ± 15. 53mmHg（7.88 ±2.07Kpa） and PErCO2 （P） was 58.95 ± 14.70mmHg（7.86 ± 1.96Kpa）. By linear regression analysis, PErCO2 （ P ） was very closely related to PaCO2 （ R = 0.95, P 〈 0.05 ）. The mean within subject coefficient of variation for PErCO2 （P） and PETCO2 （T） was 5.00 ±2.58% and 5.01 ±3.49%. They were close to each other（ P = 0.49）. In the follow -up measurement, the mean reduction of PaCO2 was 2.33 ±9.68mmHg（0.31 ± 1.29Kpa） and PETCO2 （ P） was 1.65 ± 8.10mmHg（0.22 ± 1.08Kpa）. There was close correlation between the change of PaCO2 and PETCO2 （ P ） （ R = 0.79, P 〈 0.000 ）. Conclusion： In COPD patients, there was significant difference between end tidal expired PCO2 and PaCO2, however, with the prolonged expiration method, PETCO2 （ P） could reliably estimate the PaCO2 and reflect the change of PaCO2, which will provide an valuable non - invasive method for monitoring PaCO2 in COPD patients.