Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA.
J Physiol. 2010 Jul 1;588(Pt 13):2487-501. doi: 10.1113/jphysiol.2009.186056. Epub 2010 May 10.
Heart failure (HF) patients have a reduced cardiac reserve and increased work of breathing. Increased locomotor muscle blood flow demand may result in competition between respiratory and locomotor vascular beds. We hypothesized that HF patients would demonstrate improved locomotor blood flow with respiratory muscle unloading during activity. Ten patients (ejection fraction = 31 +/- 3%) and 10 controls (CTL) underwent two cycling sessions (60% peak work). Session 1 (S1): 5 min of normal breathing (NB), 5 min respiratory muscle unloading with a ventilator, and 5 min of NB. Session 2 (S2): 5 min NB, 5 min of respiratory muscle loading with inspiratory resistance, and 5 min of NB. Measurements included: leg blood flow (LBF, thermodilution), cardiac output (Q), and oesophageal pressure (P(pl), index of pleural pressure). S1: P(pl) was reduced in both groups (HF: 73 +/- 8%; CTL: 60 +/- 13%, P < 0.01). HF: Q increased (9.6 +/- 0.4 vs. 11.3 +/- 0.8 l min(-1), P < 0.05) and LBF increased (4.8 +/- 0.8 vs. 7.3 +/- 1.1 l min(-1), P < 0.01); CTL: no changes in Q (14.7 +/- 1.0 vs. 14.8 +/- 1.6 l min(-1)) or LBF (10.9 +/- 1.8 vs. 10.3 +/- 1.7 l min(-1)). S2: P(pl) increased in both groups (HF: 172 +/- 16%, CTL: 220 +/- 40%, P < 0.01). HF: no change was observed in Q(10.0 +/- 0.4 vs. 10.3 +/- 0.8 l min(-1)) or LBF (5.0 +/- 0.6 vs. 4.7 +/- 0.5 l min(-1)); CTL: increased (15.4 +/- 1.4 vs. 16.9 +/- 1.5 l min(-1), P < 0.01) and LBF remained unchanged (10.7 +/- 1.5 vs. 10.3 +/- 1.8 l min(-1)). These data suggest HF patients preferentially steal blood flow from locomotor muscles to accommodate the work of breathing during activity. Further, HF patients are unable to vasoconstrict locomotor vascular beds beyond NB when presented with a respiratory load.
心力衰竭（HF）患者的心脏储备减少，呼吸做功增加。运动时，增加的运动肌肉血流需求可能导致呼吸和运动血管床之间的竞争。我们假设 HF 患者在活动时通过呼吸肌卸载会改善运动时的血流。10 例 HF 患者（射血分数=31±3%）和 10 例对照（CTL）进行了两次踏车运动（60%峰值工作）。第 1 节（S1）：正常呼吸（NB）5 分钟，呼吸机卸载呼吸肌 5 分钟，NB 5 分钟。第 2 节（S2）：NB 5 分钟，吸气阻力呼吸肌加载 5 分钟，NB 5 分钟。测量包括：腿血流量（LBF，热稀释法）、心输出量（Q）和食管压力（Ppl，胸膜压力指数）。S1：两组的 Ppl 均降低（HF：73±8%；CTL：60±13%，P<0.01）。HF：Q 增加（9.6±0.4 比 11.3±0.8 l min-1，P<0.05）和 LBF 增加（4.8±0.8 比 7.3±1.1 l min-1，P<0.01）；CTL：Q（14.7±1.0 比 14.8±1.6 l min-1）或 LBF（10.9±1.8 比 10.3±1.7 l min-1）无变化。S2：两组 Ppl 均增加（HF：172±16%，CTL：220±40%，P<0.01）。HF：Q（10.0±0.4 比 10.3±0.8 l min-1）或 LBF（5.0±0.6 比 4.7±0.5 l min-1）无变化；CTL：增加（15.4±1.4 比 16.9±1.5 l min-1，P<0.01），LBF 不变（10.7±1.5 比 10.3±1.8 l min-1）。这些数据表明，HF 患者在活动时优先从运动肌肉中窃取血流以适应呼吸做功。此外，HF 患者在出现呼吸负荷时无法使运动血管床的血管收缩超过 NB。
