潮气量、胸腔内压和心肌收缩力对脉搏压、每搏量和胸腔内血容量变化的影响。
Effect of tidal volume, intrathoracic pressure, and cardiac contractility on variations in pulse pressure, stroke volume, and intrathoracic blood volume.
机构信息
Cardiopulmonary Research Laboratory, Department of Critical Care Medicine, University of Pittsburgh Medical Center, 606 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA.
出版信息
Intensive Care Med. 2011 Oct;37(10):1672-9. doi: 10.1007/s00134-011-2304-3. Epub 2011 Jul 8.
PURPOSE
We evaluated the impact of increasing tidal volume (V (t)), decreased chest wall compliance, and left ventricular (LV) contractility during intermittent positive-pressure ventilation (IPPV) on the relation between pulse pressure (PP) and LV stroke volume (SV(LV)) variation (PPV and SVV, respectively), and intrathoracic blood volume (ITBV) changes.
METHODS
Sixteen pentobarbital-anesthetized thoracotomized mongrel dogs were studied both before and after propranolol-induced acute ventricular failure (AVF) (n = 4), with and without chest and abdominal pneumatic binders to decrease chest wall compliance (n = 6), and during V (t) of 5, 10, 15, and 25 ml/kg (n = 6). SV(LV) and right ventricular stroke volume (SV(RV)) were derived from electromagnetic flow probes around aortic and pulmonary artery roots. Arterial pressure was measured in the aorta using a fluid-filled catheter. Arterial PPV and SVV were calculated over three breaths as (max - min)/[(max + min)/2]. ITBV changes during ventilation were inferred from the beat-to-beat volume differences between SV(RV) and SV(LV).
RESULTS
Arterial PP and SV(LV) were tightly correlated during IPPV under all conditions (r (2) = 0.85). Both PPV and SVV increased progressively as V (t) increased and with thoraco-abdominal binding, and tended to decrease during AVF. SV(RV) phasically decreased during inspiration, whereas SV(LV) phasically decreased 2-3 beats later, such that ITBV decreased during inspiration and returned to apneic values during expiration. ITBV decrements increased with increasing V (t) or with thoraco-abdominal binding, and decreased during AVF owing to variations in SV(RV), such that both PPV and SVV tightly correlated with inspiration-associated changes in SV(RV) and ITBV.
CONCLUSION
Arterial PP and SV(LV) are tightly correlated during IPPV and their relation is not altered by selective changes in LV contractility, intrathoracic pressure, or V (t). However, contractility, intrathoracic pressure, and V (t) directly alter the magnitude of PPV and SVV primarily by altering the inspiration-associated decreases in SV(RV) and ITBV.
目的
我们评估了在间歇正压通气（IPPV）期间增加潮气量（V（t））、降低胸壁顺应性和左心室（LV）收缩力对脉搏压（PP）和左心室射血分数（SV（LV））变化之间关系的影响（分别为 PPV 和 SVV），以及胸腔内血容量（ITBV）的变化。
方法
16 只戊巴比妥钠麻醉开胸杂种犬在普罗帕酮诱导急性心室衰竭（AVF）前后（n=4）、使用和不使用胸部和腹部气动约束器降低胸壁顺应性（n=6）以及在 V（t）为 5、10、15 和 25 ml/kg 时（n=6）进行研究。SV（LV）和右心室射血分数（SV（RV））通过电磁流量探头在主动脉和肺动脉根部得出。动脉压通过充满液体的导管在主动脉中测量。在三次呼吸中计算动脉 PPV 和 SVV，公式为（最大值-最小值）/[（最大值+最小值）/2]。在通气过程中，通过 SV（RV）和 SV（LV）之间的每搏体积差异推断 ITBV 的变化。
结果
在所有条件下，在 IPPV 期间，动脉 PP 和 SV（LV）之间存在紧密的相关性（r（2）=0.85）。随着 V（t）的增加和胸廓腹部的束缚，PPV 和 SVV 逐渐增加，并在 AVF 期间趋于下降。SV（RV）在吸气时瞬间下降，而 SV（LV）在 2-3 个心跳后瞬间下降，因此 ITBV 在吸气时下降，并在呼气时恢复到无呼吸值。随着 V（t）或胸廓腹部束缚的增加，ITBV 减少，而由于 SV（RV）的变化，AVF 期间的 ITBV 减少，使得 PPV 和 SVV 与 SV（RV）和 ITBV 相关的吸气变化密切相关。
结论
在 IPPV 期间，动脉 PP 和 SV（LV）之间存在紧密的相关性，LV 收缩力、胸腔内压力或 V（t）的选择性变化不会改变它们之间的关系。然而，收缩力、胸腔内压力和 V（t）直接通过改变与吸气相关的 SV（RV）和 ITBV 的下降来改变 PPV 和 SVV 的幅度。
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