延长呼气法和曲线拟合法在老年慢性阻塞性肺疾病呼吸衰竭患者呼出气二氧化碳图中的应用

目的 探讨老年慢性阻塞性肺疾病(COPD)呼吸衰竭患者应用呼出气二氧化碳分压(PCO2)监测估算动脉血PCO2(PaCO2)的方法,为无创动态监测COPD呼吸衰竭患者的PaCO2提供方法学依据.方法 30例COPD急性加重期(AECOPD)患者给予常规药物治疗,部分患者联用BiPAP呼吸机鼻(面)罩双水平正压辅助通气,疗程为5～7d,治疗前后均采用平静呼气法和延长呼气法记录呼出气PCO2曲线图.结果 患者治疗前平静呼吸呼气末PCO2[PETCO2(Q)]为(50.72±8.93)mm Hg(1mm Hg=0.133 kPa),延长呼气第5s末PCO2[(PETCO2(P)]为(70.35±8.91)mm Hg,PaCO2为(71.25±9.08)mm Hg.治疗前PETCO2(Q)显著低于PaCO2(F=38.73,P＜0.01),PETCO2(P)与PaCO2基本一致(P＞0.05),PETCO2(P)基本能反映PaCO2;治疗后复查的结果与治疗前类似.治疗前和治疗后PETCO2(P)和PaCO2均呈正相关(r=0.96和r=0.97,P＜0.01).治疗前,根据从呼气开始到PCO2与PaCO2相等的时间(TABG)呼气时间,从平静呼气二氧化碳-时间拟合曲线公式求得PCO2(C)为(71.78±9.04)mm Hg,与PaCO2比较差异无统计学意义(P＞0.05);治疗后复查的结果与治疗前类似.治疗前后PCO2(C)与PaCO2均呈正相关(r=0.97和r=0.98,P＜0.01).结论 对于COPD伴Ⅱ型呼吸衰竭患者,延长呼气法测定PETCO2(P)可较准确地预测PaCO2,适合于PaCO2的动态预测.对于部分重度和极重度COPD患者,延长呼气法测定受到一定限制,平静呼气外推PCO2(C)值与延长呼气法测定PETCO2(P),均可较准确地预测PaCO2.

Prolonged expiratory method and curve fitting method used in exploratory study of expiratory capnography in elderly patients with chronic obstructive pulmonary disease

Objective To find noninvasive estimation of partial pressure of carbon dioxide in artery (PaCO2) by measuring the end-tidal CO2 partial pressure (PETCO2) in elderly patients with respiratory failure with chronic obstructive pulmonary disease (COPD). Methods All the 30 acutely exacerbated COPD subjects received routine clinical treatment including bronchodilators,mucolytics, glucocorticosteroid, antibiotics and oxygen therapy for 5-7 days, and part of them received noninvasive positive-pressure ventilation (NIPPV) treatment concurrently. They were both tested by eupnea method and prolonged expiratory method before and after treatment. Results Before treatment, PET CO2 (Q) (end-tidal CO2 pressure with eupnea, (50.72±8.93) mm Hg wassignificantly lower than PaCO2 (F=38.73, P＜0.01 ). Yet, PETCO2(P) (end-tidal CO2 pressure with prolong expiration) was (70.35±8.91) mm Hg and PaCO2 was (71.25±9.08) mm Hg. There was no significant difference between PETCO2 (P) and PaCO2 (P＞0.05). The similar results were found after treatment. By linear regression analysis, PetCO2(P) was remarkably positive correlated with PaCO2 before and after treatment (r=0.96 and 0.97, respectively, P＜0.01). According to TABG,PCO2(C) which was calculated by the average expiratory time of fitting curve was (71.78±9.04)mm Hg. And there was no significant difference between PCO2 (C) and PaCO2 (P＞0.05);Thesimilar results were founcl after treatment. By linear regression analysis, PCO2 (C) was remarkably positively correlated with PaCO2 (r=0.97 and 0.98, respectively, P＜0.01) before and after treatment. Conclusions In COPD patients with type Ⅱ respiratory failure, conventional PETCO2 (Q) is significantly lower than PaCO2. Yet, PETCO2 (P) could exactly estimate PaCO2 and is appropriate to its dynamic monitoring. And PCO2 (C) which is calculated by mode Boltzmann on eupnea curve also obtain similar results.