Pingitore Alessandro, Gemignani Angelo, Menicucci Danilo, Di Bella Gianluca, De Marchi Daniele, Passera Mirko, Bedini Remo, Ghelarducci Brunello, L'Abbate Antonio
CNR Institute of Clinical Physiology, Via Moruzzi 1, Pisa, Italy.
Am J Physiol Heart Circ Physiol. 2008 Jan;294(1):H449-55. doi: 10.1152/ajpheart.00607.2007. Epub 2007 Nov 9.
Prolonged breath hold (BH) represents a valid model for studying the cardiac adaptation to acute hypoxemia in humans. Cardiac magnetic resonance (CMR) allows a three-dimensional, high-resolution, noninvasive, and nonionizing anatomical and functional evaluation of the heart. The aim of the study was to assess the adaptation of the cardiovascular system to prolonged BH in air. Ten male volunteer diving athletes (age 30 +/- 6 yr) were studied during maximal BH duration with CMR. Four epochs were studied: I, rest; II and III, intermediate BH; and IV, peak BH. Oxygen saturation (So(2)), heart rate (HR), blood pressure (BP), systemic vascular resistance (VR), end-diastolic (EDV) and end-systolic volumes (ESV), stroke volume (SV), cardiac output (CO), ejection fraction (EF), maximal elastance index (EL), systolic wall thickening (SWT), and end-systolic wall stress (ESWS) of the left ventricle (LV) were measured in all four BH epochs. Average BH duration was 3.7 +/- 0.3 min. So(2) was reduced (I: 97 +/- 0.2%, range 96-98%, vs. IV: 84 +/- 2.0%, range 76-92%; P < 0.00001). BP, EDV, ESV, SV, CO, and ESWS linearly increased from epochs I to IV, whereas EF, EL, and SWT showed an opposite behavior, decreasing from resting to epoch IV (all trends are P < 0.01). During prolonged BH in air, a marked enlargement of the LV chamber occurs in healthy diving athletes. This response to acute hypoxemia allows SV,CO, and arterial pressure to be maintained despite the severe reduction in LV contractile function.
长时间屏气（BH）是研究人体心脏对急性低氧血症适应性的有效模型。心脏磁共振成像（CMR）能够对心脏进行三维、高分辨率、无创且无电离辐射的解剖结构和功能评估。本研究的目的是评估心血管系统在空气中长时间屏气时的适应性。对10名男性潜水运动员志愿者（年龄30±6岁）在最大屏气持续时间内进行CMR研究。研究了四个阶段：I，静息状态；II和III，中等屏气阶段；IV，屏气峰值阶段。在所有四个屏气阶段测量了氧饱和度（So₂）、心率（HR）、血压（BP）、全身血管阻力（VR）、舒张末期容积（EDV）和收缩末期容积（ESV）、每搏输出量（SV）、心输出量（CO）、射血分数（EF）、最大弹性指数（EL）、左心室（LV）的收缩期壁增厚（SWT）和收缩末期壁应力（ESWS）。平均屏气持续时间为3.7±0.3分钟。So₂降低（I：97±0.2%，范围96 - 98%，对比IV：84±2.0%，范围76 - 92%；P < 0.00001）。BP、EDV、ESV、SV、CO和ESWS从阶段I到IV呈线性增加，而EF、EL和SWT表现出相反的变化，从静息状态到阶段IV逐渐降低（所有趋势P < 0.01）。在空气中长时间屏气期间，健康的潜水运动员左心室腔明显扩大。这种对急性低氧血症的反应使得尽管左心室收缩功能严重降低，仍能维持SV、CO和动脉血压。
