Division of Chest and Critical Care Medicine, Department of Internal Medicine, National Taiwan University Hospital, Hsin-Chu branch, Hsin-Chu, Taiwan.
Respirology. 2012 Apr;17(3):402-11. doi: 10.1111/j.1440-1843.2011.02124.x.
Obesity, particularly severe central obesity, affects respiratory physiology both at rest and during exercise. Reductions in expiratory reserve volume, functional residual capacity, respiratory system compliance and impaired respiratory system mechanics produce a restrictive ventilatory defect. Low functional residual capacity and reductions in expiratory reserve volume increase the risk of expiratory flow limitation and airway closure during quiet breathing. Consequently, obesity may cause expiratory flow limitation and the development of intrinsic positive end expiratory pressure, especially in the supine position. This increases the work of breathing by imposing a threshold load on the respiratory muscles leading to dyspnoea. Marked reductions in expiratory reserve volume may lead to ventilation distribution abnormalities, with closure of airways in the dependent zones of the lungs, inducing ventilation perfusion mismatch and gas exchange abnormalities. Obesity may also impair upper airway mechanical function and neuromuscular strength, and increase oxygen consumption, which in turn, increase the work of breathing and impair ventilatory drive. The combination of ventilatory impairment, excess CO(2) production and reduced ventilatory drive predisposes obese individuals to obesity hypoventilation syndrome.
肥胖症，尤其是严重的中心型肥胖症，会影响休息和运动时的呼吸生理。呼气储备量、功能残气量、呼吸系统顺应性降低，以及呼吸系统力学功能受损，导致限制性通气缺陷。功能残气量降低和呼气储备量减少，增加了安静呼吸时呼气流量受限和气道关闭的风险。因此，肥胖症可能导致呼气流量受限和内源性呼气末正压的发展，尤其是在仰卧位时。这会通过对呼吸肌施加阈值负荷来增加呼吸功，导致呼吸困难。呼气储备量显著降低可能导致通气分布异常，肺的下垂区域气道关闭，引起通气/血流比例失调和气体交换异常。肥胖症还可能损害上呼吸道的力学功能和神经肌肉力量，并增加耗氧量，这反过来又增加呼吸功，并损害通气驱动。通气障碍、二氧化碳生成过多和通气驱动降低的综合作用，使肥胖者易患肥胖低通气综合征。
