Chonan T, Altose M D, Cherniack N S
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
J Appl Physiol (1985). 1990 Jul;69(1):91-5. doi: 10.1152/jappl.1990.69.1.91.
To determine whether an increase in expiratory motor output accentuates the sensation of dyspnea (difficulty in breathing), the following experiments were undertaken. Ten normal subjects, in a series of 2-min trials, breathed freely (level I) or maintained a target tidal volume equal to (level II) or twice the control (level III) at a breathing frequency of 15/min (similar to the control frequency) with an inspiratory load, an expiratory load, and without loads under hyperoxic normocapnia. In tests at levels II and III, end-expiratory lung volume was maintained at functional residual capacity. A linear resistance of 25 cmH2O.1(-1).s was used for both inspiratory and expiratory loading; peak mouth pressure (Pm) was measured, and the intensity of dyspnea (psi) was assessed with a visual analog scale. The sensation of dyspnea increased significantly with the magnitude of expiratory Pm during expiratory loading (level II: Pm = 9.4 +/- 1.5 (SE) cmH2O, psi = 1.26 +/- 0.35; level III: Pm = 20.3 +/- 2.8 cmH2O, psi = 2.22 +/- 0.48) and with inspiratory Pm during inspiratory loading (level II: Pm = 9.7 +/- 1.2 cmH2O, psi = 1.35 +/- 0.38; level III: Pm = 23.9 +/- 3.0 cmH2O, psi = 2.69 +/- 0.60). However, at each level of breathing, neither the intensity of dyspnea nor the magnitude of peak Pm during loading was different between inspiratory and expiratory loading. The augmentation of dyspnea during expiratory loading was not explained simply by increases in inspiratory activity. The results indicate that heightened expiratory as well as inspiratory motor output causes comparable increases in the sensation of difficulty in breathing.
为了确定呼气运动输出增加是否会加剧呼吸困难的感觉，进行了以下实验。十名正常受试者在一系列2分钟的试验中，在高氧正常碳酸血症状态下，以15次/分钟的呼吸频率（与对照频率相似）自由呼吸（I级），或维持目标潮气量等于对照（II级）或对照的两倍（III级），同时施加吸气负荷、呼气负荷以及无负荷状态。在II级和III级测试中，呼气末肺容积维持在功能残气量。吸气和呼气负荷均采用25 cmH2O·L⁻¹·s的线性阻力；测量口腔峰值压力（Pm），并使用视觉模拟量表评估呼吸困难的强度（psi）。在呼气负荷期间，呼吸困难的感觉随呼气Pm的大小显著增加（II级：Pm = 9.4 ± 1.5（SE）cmH2O，psi = 1.26 ± 0.35；III级：Pm = 20.3 ± 2.8 cmH2O，psi = 2.22 ± 0.48），在吸气负荷期间随吸气Pm的大小显著增加（II级：Pm = 9.7 ± 1.2 cmH2O，psi = 1.35 ± 0.38；III级：Pm = 23.9 ± 3.0 cmH2O，psi = 2.69 ± 0.60）。然而，在每个呼吸水平，吸气负荷和呼气负荷期间的呼吸困难强度以及峰值Pm大小均无差异。呼气负荷期间呼吸困难的加剧并非仅仅由吸气活动增加所解释。结果表明，呼气运动输出和吸气运动输出增强均会导致呼吸困难感觉出现类似程度的增加。
