Myers Jonathan, Gujja Pradeep, Neelagaru Suresh, Hsu Leon, Vittorio Timothy, Jackson-Nelson Tamika, Burkhoff Daniel
Cardiology Division, Veterans Affairs Palo Alto Health Care System, Stanford University, Palo Alto, CA 94304, USA.
Med Sci Sports Exerc. 2009 Jan;41(1):19-25. doi: 10.1249/MSS.0b013e318184c945.
In patients with heart failure (HF), end-tidal CO2 pressure (PetCO2) is related to ventricular function at rest and has been shown to predict prognosis. However, little is known about the association between ventricular performance and PetCO2 responses to exercise.
Forty-eight patients with HF and 13 normal subjects underwent cardiopulmonary exercise testing (CPX), while cardiac output and other hemodynamic measurements at rest and during exercise were obtained using a novel, noninvasive, bioreactance device based on assessment of relative phase shifts of electric currents injected across the thorax, heart rate, and ventricular ejection time. CPX responses and indices of cardiac performance were compared between normal subjects and HF patients achieving above and below a PetCO2 of 36 mm Hg at the ventilatory threshold (PetCO2@VT).
HF patients with an abnormal PetCO2@VT (<36 mm Hg) had a lower exercise capacity, a lower .VO2@VT, a higher .V_E/.VCO2 slope, and lower oxygen uptake efficiency slope (OUES) values compared with normal subjects and patients achieving a normal PetCO2@VT. Patients with reduced PetCO2@VT had lower peak cardiac output responses to exercise (20.0 +/- 10, 17.8 +/- 6, and 13.7 +/- 7 L x min for normal subjects and HF patients with normal and abnormal PetCO2 responses to exercise, respectively, P = 0.04). PetCO2@VT was inversely related to the .V_E/.VCO2 slope (r = -0.78, P < 0.001) and directly related to the OUES (r = 0.55, P < 0.001).
Reduced PetCO2 reflects impairments in the functional, ventilatory, and cardiac performance response to exercise in patients with HF. PetCO2 can supplement other clinical and CPX indices in the functional and prognostic evaluation of patients with HF.
在心力衰竭（HF）患者中，呼气末二氧化碳分压（PetCO2）与静息时的心室功能相关，并且已被证明可预测预后。然而，关于心室功能与运动时PetCO2反应之间的关联，人们知之甚少。
48例HF患者和13名正常受试者接受了心肺运动试验（CPX），同时使用一种基于评估经胸注入电流的相对相移的新型无创生物电阻抗装置，获取静息和运动期间的心输出量及其他血流动力学测量值、心率和心室射血时间。比较正常受试者与在通气阈值时PetCO2高于和低于36 mmHg的HF患者之间的CPX反应和心脏功能指标（PetCO2@VT）。
与正常受试者和PetCO2@VT正常的患者相比，PetCO2@VT异常（<36 mmHg）的HF患者运动能力较低、通气阈值时的摄氧量（.VO2@VT）较低、.V_E/.VCO2斜率较高且氧摄取效率斜率（OUES）值较低。PetCO2@VT降低的患者运动时的心输出量峰值反应较低（正常受试者以及运动时PetCO2反应正常和异常的HF患者分别为20.0±10、17.8±6和13.7±7 L·min，P = 0.04）。PetCO2@VT与.V_E/.VCO2斜率呈负相关（r = -0.78，P < 0.001），与OUES呈正相关（r = 0.55，P < 0.001）。
PetCO2降低反映了HF患者运动时功能、通气和心脏功能反应受损。PetCO2可在HF患者的功能和预后评估中补充其他临床和CPX指标。
