Dept. of Env. Health, Harvard School of Public Health, USA.
Compr Physiol. 2011 Jan;1(1):263-82. doi: 10.1002/cphy.c100017.
Obesity currently affects about one-third of the U.S. population, while another one-third is overweight. The importance of obesity for certain conditions such as heart disease and type 2 diabetes is well appreciated. The effects of obesity on the respiratory system have received less attention and are the subject of this article. Obesity alters the static mechanical properties of the respiratory system leading to a reduction in the functional residual capacity (FRC) and the expiratory reserve volume (ERV). There is substantial variability in the effects of obesity on FRC and ERV, at least some of which is related to the location rather than the total mass of adipose tissue. Obesity also results in airflow obstruction, which is only partially attributable to breathing at low lung volume, and can also promote airway hyperresponsiveness and asthma. Hypoxemia is common is obesity and correlates well with FRC, as well as with measures of abdominal obesity. However, obese subjects are usually eucapnic, indicating that hypoventilation is not a common cause of their hypoxemia. Instead, hypoxemia results from ventilation-perfusion mismatch caused by closure of dependent airways at FRC. Many obese subjects complain of dyspnea either at rest or during exertion, and the dyspnea score also correlates with reductions in FRC and ERV. Weight reduction should be encouraged in any symptomatic obese individual, since virtually all of the respiratory complications of obesity improve with even moderate weight loss.
目前，肥胖影响了大约三分之一的美国人口，另有三分之一的人超重。肥胖对某些疾病的重要性，如心脏病和 2 型糖尿病，已得到充分认识。然而，肥胖对呼吸系统的影响却没有得到足够的重视，本文正是针对这一问题展开讨论。肥胖改变了呼吸系统的静态力学特性，导致功能残气量（FRC）和呼气储备量（ERV）减少。肥胖对 FRC 和 ERV 的影响存在很大的可变性，至少有一部分与脂肪组织的位置而非总质量有关。肥胖还会导致气流阻塞，这部分阻塞部分归因于低肺容积时的呼吸，但也可以促进气道高反应性和哮喘。肥胖患者常伴有低氧血症，与 FRC 以及腹部肥胖的衡量指标密切相关。然而，肥胖患者通常为正常碳酸血症，这表明低通气并不是其低氧血症的常见原因。相反，低氧血症是由于 FRC 时依赖气道的关闭导致通气-灌注不匹配引起的。许多肥胖患者无论是在休息时还是在运动时都会出现呼吸困难，呼吸困难评分也与 FRC 和 ERV 的减少相关。任何有症状的肥胖个体都应鼓励减轻体重，因为肥胖的几乎所有呼吸系统并发症都会随着适度的体重减轻而改善。
