Universidad del Desarrollo, Santiago, Chile.
Respir Care. 2012 Apr;57(4):583-9. doi: 10.4187/respcare.01342. Epub 2011 Oct 13.
Ventilatory inefficiency increases ventilatory demand; corresponds to an abnormal increase in the ratio of minute ventilation (V_dot(E)) to CO(2) production (V_dot(CO(2))); represents increased dead space, deregulation of respiratory control, and early lactic threshold; and is associated with expiratory flow limitation that enhances dynamic hyperinflation and may limit exercise capacity.
To evaluate the influence of ventilatory inefficiency over exercise capacity in COPD patients.
Prospective study of 35 COPD subjects with different levels of severity, in whom cardiopulmonary stress test was performed. Ventilatory inefficiency was represented by the V_dot(E) /V_dot(CO(2)) relation. Its influence over maximal oxygen consumption (V_dot(O(2))max), power (W), and ventilatory threshold was evaluated. Surrogate parameters of cardiac function, like oxygen pulse (V_dot(O(2))/heart rate) and circulatory power (%V_dot(O(2))max × peak systolic pressure), were also evaluated.
Cardiopulmonary stress test was stopped due to dyspnea with elevated V_dot(E) and marked reduction of breathing reserve. A severe increase in V_dot(CO(2)) (mean ± SD 35.9 ± 5.6), a decrease of V_dot(O(2)) (mean ± SD 75.2 ± 20%), and a decrease of W (mean ± SD 68.6 ± 23.3%) were demonstrated. Twenty-eight patients presented dynamic hyperinflation. Linear regression showed a reduction of 2.04% on V_dot(O(2>))max (P < .001), 2.6% on W (P < .001), 1% on V_dot(O(2))/heart rate (P = .049), and 322.7 units on circulatory power (P = .02) per each unit of increment in V_dot(E)/V_dot(CO(2)), respectively.
Ventilatory inefficiency correlates with a reduction in exercise capacity in COPD patients. Including this parameter in the evaluation of exercise limitation in this patient population may mean a contribution toward the understanding of its pathophysiology.
通气效率降低会增加通气需求；与分钟通气量（V_dot(E)）与二氧化碳产生量（V_dot(CO(2))）的比值异常增加相对应；代表死腔增加、呼吸控制失调和早期乳酸阈；并与呼气流量受限相关，呼气流量受限可增强动态过度充气并可能限制运动能力。
评估 COPD 患者通气效率低下对运动能力的影响。
对不同严重程度的 35 例 COPD 患者进行前瞻性研究，对其进行心肺压力测试。通气效率通过 V_dot(E)/V_dot(CO(2)) 关系来表示。评估其对最大耗氧量（V_dot(O(2))max）、功率（W）和通气阈的影响。还评估了心脏功能的替代参数，如氧脉冲（V_dot(O(2))/心率）和循环功率（%V_dot(O(2))max×收缩压峰值）。
由于通气量增加和呼吸储备明显降低而出现呼吸困难，心肺压力测试被迫停止。V_dot(CO(2)) 显著增加（均值 ± 标准差 35.9 ± 5.6），V_dot(O(2)) 降低（均值 ± 标准差 75.2 ± 20%），W 降低（均值 ± 标准差 68.6 ± 23.3%）。28 例患者出现动态过度充气。线性回归显示，V_dot(O(2>))max 降低 2.04%（P <.001），W 降低 2.6%（P <.001），V_dot(O(2))/心率降低 1%（P =.049），循环功率降低 322.7 单位（P =.02），每增加一个单位的 V_dot(E)/V_dot(CO(2))。
通气效率与 COPD 患者运动能力下降相关。在 COPD 患者运动受限的评估中加入该参数可能有助于理解其病理生理学。
