心脏移植受者运动诱发的低氧血症

Braith R W, Limacher M C, Mills R M, Leggett S H, Pollock M L, Staples E D

Center for Exercise Science, College of Medicine, University of Florida, Gainesville 32610.

J Am Coll Cardiol. 1993 Sep;22(3):768-76. doi: 10.1016/0735-1097(93)90189-8.

OBJECTIVES

The purpose of this study was to determine whether heart transplantation has an adverse effect on pulmonary diffusion and to investigate the potentially deleterious effects of impaired pulmonary diffusion on arterial blood gas dynamics during exercise in heart transplant recipients.

BACKGROUND

Abnormal pulmonary diffusing capacity is reported in patients after orthotopic heart transplantation. Abnormal diffusion may be caused by cyclosporine or by the persistence of preexisting conditions known to adversely affect diffusion, such as congestive heart failure and chronic obstructive pulmonary disease.

METHODS

Eleven patients (mean age 50 +/- 14 years) performed pulmonary function tests 3 +/- 1 months before and 18 +/- 12 (mean +/- SD) months after heart transplantation. Transplant patients were assigned to groups with diffusion > 70% (n = 5) or diffusion < 70% of predicted values (n = 5). The control group and both subsets of patients performed 10 min of cycle exercise at 40% and 70% of peak power output. Arterial blood gases were drawn every 30 s during the 1st 5 min and at 6, 8 and 10 min.

RESULTS

Significant improvements in forced vital capacity (17.4%), forced expiratory volume in 1 s (11.7%) and diffusion capacity (6.6%) occurred in the patients; however, posttransplantation vital capacity, forced expiratory volume and diffusion were lower (p < or = 0.05) compared with values in 11 matched control subjects. Changes in blood gases were similar among groups at 40% of peak power output. At 70% of peak power output, arterial blood gases and pH were significantly (p < or = 0.05) lower in transplant patients with low diffusion (arterial oxygen pressure 15 to 38 mm Hg below baseline) than in patients with normal diffusion and control subjects. Cardiac index did not differ (p > or = 0.05) between transplant patients with normal and low diffusion at rest or during exercise. Posttransplantation mean pulmonary artery pressure was significantly related to exercise-induced hypoxemia (r = 0.71; p = 0.03).

CONCLUSIONS

Abnormal pulmonary diffusion observed in patients before heart transplantation persists after transplantation with or without restrictive or obstructive ventilatory defects. Heart transplant recipients experience exercise-induced hypoxemia when diffusion at rest is < 70% of predicted. Our data also suggest that abnormal pulmonary gas exchange possibly contributes to diminished peak oxygen consumption in some heart transplant recipients; however, direct testing of this hypothesis was beyond the scope of the present study. This possibility needs to be investigated further.

目的

本研究旨在确定心脏移植对肺弥散是否有不利影响，并调查肺弥散受损对心脏移植受者运动期间动脉血气动力学的潜在有害影响。

背景

原位心脏移植术后患者报告有异常的肺弥散能力。异常弥散可能由环孢素引起，或由已知会对弥散产生不利影响的既往疾病持续存在所致，如充血性心力衰竭和慢性阻塞性肺疾病。

方法

11例患者（平均年龄50±14岁）在心脏移植前3±1个月和移植后18±12（平均±标准差）个月进行肺功能测试。将移植患者分为弥散>预测值70%的组（n = 5）和弥散<预测值70%的组（n = 5）。对照组以及两组患者均以峰值功率输出的40%和70%进行10分钟的自行车运动。在最初5分钟内每30秒采集一次动脉血气，并在6、8和10分钟时采集。

结果

患者的用力肺活量（提高17.4%）、第1秒用力呼气量（提高11.7%）和弥散能力（提高6.6%）有显著改善；然而，与11名匹配的对照受试者的值相比，移植后的肺活量、用力呼气量和弥散较低（p≤0.05）。在峰值功率输出的40%时，各组间血气变化相似。在峰值功率输出的70%时，弥散低的移植患者（动脉血氧分压比基线低15至38 mmHg）的动脉血气和pH值显著低于（p≤0.05）弥散正常的患者和对照受试者。在静息或运动时，弥散正常和低的移植患者之间的心指数无差异（p≥0.05）。移植后的平均肺动脉压与运动诱发的低氧血症显著相关（r = 0.71；p = 0.03）。

结论

心脏移植前患者中观察到的异常肺弥散在移植后持续存在，无论是否存在限制性或阻塞性通气缺陷。当静息时的弥散<预测值的70%时，心脏移植受者会出现运动诱发的低氧血症。我们的数据还表明，异常的肺气体交换可能导致一些心脏移植受者的峰值氧耗量降低；然而，对这一假设的直接测试超出了本研究的范围。这一可能性需要进一步研究。