University of Calgary, Department of Medicine, Division of Respirology, Calgary, Alberta, Canada; Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada; Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France; Service de Pneumologie, Hôpital Bicêtre, AP-HP, Le Kremlin-Bicêtre, France; INSERM U999, LabEx LERMIT, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France.
Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, Le Kremlin-Bicêtre, France; Service de Pneumologie, Hôpital Bicêtre, AP-HP, Le Kremlin-Bicêtre, France; INSERM U999, LabEx LERMIT, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France.
Arch Bronconeumol (Engl Ed). 2020 Sep;56(9):578-585. doi: 10.1016/j.arbres.2019.12.030. Epub 2020 Feb 26.
Ventilatory inefficiency (high V'/V'CO) and resting hypocapnia are common in pulmonary vascular disease and are associated with poor prognosis. Low resting PaCO suggests increased chemosensitivity or an altered PaCO set-point. We aimed to determine the relationships between exercise gas exchange variables reflecting the PaCO set-point, exercise capacity, hemodynamics and V'/V'CO.
Pulmonary arterial hypertension (n=34), chronic thromboembolic pulmonary hypertension (CTEPH, n=19) and pulmonary veno-occlusive disease (PVOD, n=6) patients underwent rest and peak exercise arterial blood gas measurements during cardiopulmonary exercise testing. Patients were grouped according to resting PaCO: hypocapnic (PaCO ≤34mmHg) or normocapnic (PaCO 35-45mmHg). The PaCO set-point was estimated by the maximal value of end-tidal PCO (maximal PCO) between the anaerobic threshold and respiratory compensation point.
The hypocapnic group (n=39) had lower resting cardiac index (3.1±0.8 vs. 3.7±0.7L/min/m, p<0.01), lower peak V'O (15.8±3.5 vs. 20.7±4.3mL/kg/min, p<0.01), and higher V'/V'CO slope (60.6±17.6 vs. 38.2±8.0, p<0.01). At peak exercise, hypocapic patients had lower PaO, higher V/V and higher PCO. Maximal PCO (r=0.59) and V/V (r=-0.59) were more related to cardiac index than PaO or PaCO at rest or peak exercise. Maximal PCO was the strongest correlate of V'/V'CO slope (r=-0.86), peak V'O (r=0.64) and peak work rate (r=0.49).
Resting hypocapnia is associated with worse cardiac function, more ventilatory inefficiency and reduced exercise capacity. This could be explained by elevated chemosensitivity and lower PaCO set-point. Maximal PCO may be a useful non-invasive marker of PaCO setpoint and disease severity even with submaximal effort.
通气效率低下（高 V'/V'CO）和静息性低碳酸血症在肺血管疾病中很常见，与预后不良有关。静息性 PaCO 较低提示化学感受器敏感性增加或 PaCO 设定点改变。我们旨在确定反映 PaCO 设定点、运动能力、血液动力学和 V'/V'CO 的运动气体交换变量之间的关系。
肺动脉高压（n=34）、慢性血栓栓塞性肺动脉高压（CTEPH，n=19）和肺静脉闭塞性疾病（PVOD，n=6）患者在心肺运动测试期间进行静息和峰值运动动脉血气测量。根据静息性 PaCO 分组：低碳酸血症（PaCO≤34mmHg）或正常碳酸血症（PaCO 35-45mmHg）。通过在无氧阈和呼吸补偿点之间的最大呼气末 PCO（最大 PCO）来估计 PaCO 设定点。
低碳酸血症组（n=39）的静息性心指数较低（3.1±0.8 与 3.7±0.7L/min/m，p<0.01），峰值 V'O 较低（15.8±3.5 与 20.7±4.3mL/kg/min，p<0.01），V'/V'CO 斜率较高（60.6±17.6 与 38.2±8.0，p<0.01）。在峰值运动时，低碳酸血症患者的 PaO 较低，V/V 较高，PCO 较高。最大 PCO（r=0.59）和 V/V（r=-0.59）与静息或峰值运动时的 PaO 或 PaCO 相比，与心指数的相关性更强。最大 PCO 与 V'/V'CO 斜率（r=-0.86）、峰值 V'O（r=0.64）和峰值工作率（r=0.49）相关性最强。
静息性低碳酸血症与心脏功能更差、通气效率更低和运动能力降低有关。这可以通过化学感受器敏感性增加和 PaCO 设定点降低来解释。最大 PCO 可能是 PaCO 设定点和疾病严重程度的有用非侵入性标志物，即使在亚最大努力下也是如此。
