University of Oregon, Department of Human Physiology, Eugene, Oregon, USA.
J Appl Physiol (1985). 2011 May;110(5):1354-61. doi: 10.1152/japplphysiol.01246.2010. Epub 2011 Mar 3.
The prevalence of a patent foramen ovale (PFO) is ~30%, and this source of right-to-left shunt could result in greater pulmonary gas exchange impairment at rest and during exercise. The aim of this work was to determine if individuals with an asymptomatic PFO (PFO+) have greater pulmonary gas exchange inefficiency at rest and during exercise than subjects without a PFO (PFO-). Separated by 1 h of rest, 8 PFO+ and 8 PFO- subjects performed two incremental cycle ergometer exercise tests to voluntary exhaustion while breathing either room air or hypoxic gas [fraction of inspired O(2) (FI(O(2))) = 0.12]. Using echocardiography, we detected small, intermittent boluses of saline contrast bubbles entering directly into the left atrium within 3 heart beats at rest and during both exercise conditions in PFO+. These findings suggest a qualitatively small intracardiac shunt at rest and during exercise in PFO+. The alveolar-to-arterial oxygen difference (AaDo(2)) was significantly (P < 0.05) different between PFO+ and PFO- in normoxia (5.9 ± 5.1 vs. 0.5 ± 3.5 mmHg) and hypoxia (10.1 ± 5.9 vs. 4.1 ± 3.1 mmHg) at rest, but not during exercise. However, arterial oxygen saturation was significantly different between PFO+ and PFO- at peak exercise in normoxia (94.3 ± 0.9 vs. 95.8 ± 1.0%) as a result of a significant difference in esophageal temperature (38.4 ± 0.3 vs. 38.0 ± 0.3°C). An asymptomatic PFO contributes to pulmonary gas exchange inefficiency at rest but not during exercise in healthy humans and therefore does not explain intersubject variability in the AaDO(2) at maximal exercise.
卵圆孔未闭（PFO）的患病率约为 30%，这种右向左分流的来源可能导致休息和运动时的肺气体交换受损更大。本研究的目的是确定无症状 PFO（PFO+）患者在休息和运动时的肺气体交换效率是否比没有 PFO（PFO-）的患者更高。8 名 PFO+和 8 名 PFO-患者在休息 1 小时后，分别在呼吸空气或低氧气体[吸入氧分数（FI（O2））= 0.12]时进行了两次递增的踏车运动试验，直至力竭。通过超声心动图，我们在 PFO+中发现，在休息和运动期间，每隔 3 次心跳就会有小的、间歇性的盐水对比剂微泡直接进入左心房。这些发现表明，PFO+在休息和运动时存在小的、定性的心内分流。在休息时，PFO+的肺泡动脉氧差（AaDo2）在常氧（5.9±5.1 对 0.5±3.5mmHg）和低氧（10.1±5.9 对 4.1±3.1mmHg）时与 PFO-显著不同（P<0.05），但在运动时则没有。然而，由于食管温度的显著差异（38.4±0.3 对 38.0±0.3°C），在常氧下，PFO+在运动峰值时的动脉血氧饱和度与 PFO-显著不同（94.3±0.9 对 95.8±1.0%）。无症状的 PFO 导致健康人在休息时的肺气体交换效率降低，但在运动时则没有，因此不能解释最大运动时 AaDo2 的个体间变异性。
